Add code for prototyping with the 2012 drivebase

Change-Id: I16b5b2e9982f1911b410c25872eca7a00fa561f3
diff --git a/y2012/control_loops/accessories/BUILD b/y2012/control_loops/accessories/BUILD
new file mode 100644
index 0000000..7dde829
--- /dev/null
+++ b/y2012/control_loops/accessories/BUILD
@@ -0,0 +1,25 @@
+package(default_visibility = ['//visibility:public'])
+
+load('/aos/build/queues', 'queue_library')
+
+cc_binary(
+  name = 'accessories',
+  srcs = [
+    'accessories.cc',
+  ],
+  deps = [
+    ':accessories_queue',
+    '//aos/linux_code:init',
+    '//aos/common/controls:control_loop',
+  ],
+)
+
+queue_library(
+  name = 'accessories_queue',
+  srcs = [
+    'accessories.q',
+  ],
+  deps = [
+    '//aos/common/controls:control_loop_queues',
+  ],
+)
diff --git a/y2012/control_loops/accessories/accessories.cc b/y2012/control_loops/accessories/accessories.cc
new file mode 100644
index 0000000..1c0dcbc
--- /dev/null
+++ b/y2012/control_loops/accessories/accessories.cc
@@ -0,0 +1,39 @@
+#include "y2012/control_loops/accessories/accessories.q.h"
+
+#include "aos/linux_code/init.h"
+#include "aos/common/controls/control_loop.h"
+
+namespace y2012 {
+namespace control_loops {
+namespace accessories {
+
+class AccessoriesLoop : public ::aos::controls::ControlLoop<
+                            ::y2012::control_loops::AccessoriesQueue> {
+ public:
+  explicit AccessoriesLoop(
+      ::y2012::control_loops::AccessoriesQueue *my_accessories =
+          &::y2012::control_loops::accessories_queue)
+      : ::aos::controls::ControlLoop<::y2012::control_loops::AccessoriesQueue>(
+            my_accessories) {}
+
+  void RunIteration(
+      const ::y2012::control_loops::AccessoriesQueue::Message *goal,
+      const ::aos::control_loops::Position * /*position*/,
+      ::y2012::control_loops::AccessoriesQueue::Message *output,
+      ::aos::control_loops::Status * /*status*/) override {
+    if (output) {
+      *output = *goal;
+    }
+  }
+};
+
+}  // namespace accessories
+}  // namespace control_loops
+}  // namespace y2012
+
+int main() {
+  ::aos::Init();
+  ::y2012::control_loops::accessories::AccessoriesLoop accessories;
+  accessories.Run();
+  ::aos::Cleanup();
+}
diff --git a/y2012/control_loops/accessories/accessories.q b/y2012/control_loops/accessories/accessories.q
new file mode 100644
index 0000000..79f9820
--- /dev/null
+++ b/y2012/control_loops/accessories/accessories.q
@@ -0,0 +1,18 @@
+package y2012.control_loops;
+
+import "aos/common/controls/control_loops.q";
+
+queue_group AccessoriesQueue {
+  implements aos.control_loops.ControlLoop;
+  message Message {
+    bool[3] solenoids;
+    double[2] sticks;
+  };
+
+  queue Message goal;
+  queue .aos.control_loops.Position position;
+  queue Message output;
+  queue .aos.control_loops.Status status;
+};
+
+queue_group AccessoriesQueue accessories_queue;
diff --git a/y2012/control_loops/drivetrain/BUILD b/y2012/control_loops/drivetrain/BUILD
new file mode 100644
index 0000000..d23c06f
--- /dev/null
+++ b/y2012/control_loops/drivetrain/BUILD
@@ -0,0 +1,150 @@
+package(default_visibility = ['//visibility:public'])
+
+load('/aos/build/queues', 'queue_library')
+
+cc_binary(
+  name = 'replay_drivetrain',
+  srcs = [
+    'replay_drivetrain.cc',
+  ],
+  deps = [
+    ':drivetrain_queue',
+    '//aos/common/controls:replay_control_loop',
+    '//aos/linux_code:init',
+    '//frc971/queues:gyro',
+  ],
+)
+
+queue_library(
+  name = 'drivetrain_queue',
+  srcs = [
+    'drivetrain.q',
+  ],
+  deps = [
+    '//aos/common/controls:control_loop_queues',
+  ],
+)
+
+genrule(
+  name = 'genrule_drivetrain',
+  visibility = ['//visibility:private'],
+  cmd = '$(location //y2012/control_loops/python:drivetrain) $(OUTS)',
+  tools = [
+    '//y2012/control_loops/python:drivetrain',
+  ],
+  outs = [
+    'drivetrain_dog_motor_plant.h',
+    'drivetrain_dog_motor_plant.cc',
+    'kalman_drivetrain_motor_plant.h',
+    'kalman_drivetrain_motor_plant.cc',
+  ],
+)
+
+genrule(
+  name = 'genrule_polydrivetrain',
+  visibility = ['//visibility:private'],
+  cmd = '$(location //y2012/control_loops/python:polydrivetrain) $(OUTS)',
+  tools = [
+    '//y2012/control_loops/python:polydrivetrain',
+  ],
+  outs = [
+    'polydrivetrain_dog_motor_plant.h',
+    'polydrivetrain_dog_motor_plant.cc',
+    'polydrivetrain_cim_plant.h',
+    'polydrivetrain_cim_plant.cc',
+  ],
+)
+
+cc_library(
+  name = 'polydrivetrain_plants',
+  srcs = [
+    'polydrivetrain_dog_motor_plant.cc',
+    'drivetrain_dog_motor_plant.cc',
+    'kalman_drivetrain_motor_plant.cc',
+  ],
+  hdrs = [
+    'polydrivetrain_dog_motor_plant.h',
+    'drivetrain_dog_motor_plant.h',
+    'kalman_drivetrain_motor_plant.h',
+  ],
+  deps = [
+    '//frc971/control_loops:state_feedback_loop',
+  ],
+)
+
+cc_library(
+  name = 'ssdrivetrain',
+  srcs = [
+    'ssdrivetrain.cc',
+  ],
+  hdrs = [
+    'ssdrivetrain.h',
+  ],
+  deps = [
+    ':polydrivetrain_plants',
+    ':drivetrain_queue',
+    '//aos/common/controls:polytope',
+    '//aos/common:math',
+    '//aos/common/messages:robot_state',
+    '//frc971/control_loops:state_feedback_loop',
+    '//frc971/control_loops:coerce_goal',
+    '//aos/common/util:log_interval',
+    '//aos/common/logging:queue_logging',
+    '//aos/common/logging:matrix_logging',
+  ],
+)
+
+cc_library(
+  name = 'polydrivetrain',
+  srcs = [
+    'polydrivetrain.cc',
+  ],
+  hdrs = [
+    'polydrivetrain.h',
+  ],
+  deps = [
+    ':polydrivetrain_plants',
+    ':drivetrain_queue',
+    '//aos/common/controls:polytope',
+    '//aos/common:math',
+    '//aos/common/messages:robot_state',
+    '//frc971/control_loops:state_feedback_loop',
+    '//frc971/control_loops:coerce_goal',
+    '//aos/common/util:log_interval',
+    '//aos/common/logging:queue_logging',
+    '//aos/common/logging:matrix_logging',
+  ],
+)
+
+cc_library(
+  name = 'drivetrain_lib',
+  srcs = [
+    'drivetrain.cc',
+  ],
+  hdrs = [
+    'drivetrain.h',
+  ],
+  deps = [
+    ':drivetrain_queue',
+    ':polydrivetrain',
+    ':polydrivetrain_plants',
+    ':ssdrivetrain',
+    '//aos/common/controls:control_loop',
+    '//frc971/queues:gyro',
+    '//aos/common/util:log_interval',
+    '//aos/common/logging:queue_logging',
+    '//aos/common/logging:matrix_logging',
+  ],
+)
+
+cc_binary(
+  name = 'drivetrain',
+  srcs = [
+    'drivetrain_main.cc',
+  ],
+  deps = [
+    '//aos/linux_code:init',
+    ':drivetrain_lib',
+    ':drivetrain_queue',
+  ],
+)
diff --git a/y2012/control_loops/drivetrain/drivetrain.cc b/y2012/control_loops/drivetrain/drivetrain.cc
new file mode 100644
index 0000000..e97e440
--- /dev/null
+++ b/y2012/control_loops/drivetrain/drivetrain.cc
@@ -0,0 +1,152 @@
+#include "y2012/control_loops/drivetrain/drivetrain.h"
+
+#include <stdio.h>
+#include <sched.h>
+#include <cmath>
+#include <memory>
+#include "Eigen/Dense"
+
+#include "aos/common/logging/logging.h"
+#include "aos/common/logging/queue_logging.h"
+#include "aos/common/logging/matrix_logging.h"
+
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "y2012/control_loops/drivetrain/drivetrain_dog_motor_plant.h"
+#include "y2012/control_loops/drivetrain/kalman_drivetrain_motor_plant.h"
+#include "y2012/control_loops/drivetrain/polydrivetrain.h"
+#include "y2012/control_loops/drivetrain/ssdrivetrain.h"
+#include "frc971/queues/gyro.q.h"
+
+// A consistent way to mark code that goes away without shifters. It's still
+// here because we will have shifters again in the future.
+#define HAVE_SHIFTERS 1
+
+using frc971::sensors::gyro_reading;
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+DrivetrainLoop::DrivetrainLoop(
+    ::y2012::control_loops::DrivetrainQueue *my_drivetrain)
+    : aos::controls::ControlLoop<::y2012::control_loops::DrivetrainQueue>(
+          my_drivetrain),
+      kf_(::y2012::control_loops::drivetrain::MakeKFDrivetrainLoop()) {
+  ::aos::controls::HPolytope<0>::Init();
+}
+
+void DrivetrainLoop::RunIteration(
+    const ::y2012::control_loops::DrivetrainQueue::Goal *goal,
+    const ::y2012::control_loops::DrivetrainQueue::Position *position,
+    ::y2012::control_loops::DrivetrainQueue::Output *output,
+    ::y2012::control_loops::DrivetrainQueue::Status *status) {
+  bool bad_pos = false;
+  if (position == nullptr) {
+    LOG_INTERVAL(no_position_);
+    bad_pos = true;
+  }
+  no_position_.Print();
+
+  bool control_loop_driving = false;
+  if (goal) {
+    double wheel = goal->steering;
+    double throttle = goal->throttle;
+    bool quickturn = goal->quickturn;
+#if HAVE_SHIFTERS
+    bool highgear = goal->highgear;
+#endif
+
+    control_loop_driving = goal->control_loop_driving;
+    double left_goal = goal->left_goal;
+    double right_goal = goal->right_goal;
+
+    dt_closedloop_.SetGoal(left_goal, goal->left_velocity_goal, right_goal,
+                           goal->right_velocity_goal);
+#if HAVE_SHIFTERS
+    dt_openloop_.SetGoal(wheel, throttle, quickturn, highgear);
+#else
+    dt_openloop_.SetGoal(wheel, throttle, quickturn, false);
+#endif
+  }
+
+  if (!bad_pos) {
+    const double left_encoder = position->left_encoder;
+    const double right_encoder = position->right_encoder;
+    if (gyro_reading.FetchLatest()) {
+      LOG_STRUCT(DEBUG, "using", *gyro_reading.get());
+      dt_closedloop_.SetPosition(left_encoder, right_encoder,
+                                 gyro_reading->angle);
+      last_gyro_heading_ = gyro_reading->angle;
+      last_gyro_rate_ = gyro_reading->velocity;
+    } else {
+      dt_closedloop_.SetRawPosition(left_encoder, right_encoder);
+    }
+  }
+  dt_openloop_.SetPosition(position);
+  dt_openloop_.Update();
+
+  if (control_loop_driving) {
+    dt_closedloop_.Update(output == NULL, true);
+    dt_closedloop_.SendMotors(output);
+  } else {
+    dt_openloop_.SendMotors(output);
+    if (output) {
+      dt_closedloop_.SetExternalMotors(output->left_voltage,
+                                       output->right_voltage);
+    }
+    dt_closedloop_.Update(output == NULL, false);
+  }
+
+  // set the output status of the control loop state
+  if (status) {
+    status->robot_speed = dt_closedloop_.GetEstimatedRobotSpeed();
+    status->filtered_left_position = dt_closedloop_.GetEstimatedLeftEncoder();
+    status->filtered_right_position = dt_closedloop_.GetEstimatedRightEncoder();
+
+    status->filtered_left_velocity = dt_closedloop_.loop().X_hat(1, 0);
+    status->filtered_right_velocity = dt_closedloop_.loop().X_hat(3, 0);
+    status->output_was_capped = dt_closedloop_.OutputWasCapped();
+    status->uncapped_left_voltage = dt_closedloop_.loop().U_uncapped(0, 0);
+    status->uncapped_right_voltage = dt_closedloop_.loop().U_uncapped(1, 0);
+  }
+
+
+  double left_voltage = 0.0;
+  double right_voltage = 0.0;
+  if (output) {
+    left_voltage = output->left_voltage;
+    right_voltage = output->right_voltage;
+  }
+
+  const double scalar = ::aos::robot_state->voltage_battery / 12.0;
+
+  left_voltage *= scalar;
+  right_voltage *= scalar;
+
+  kf_.set_controller_index(dt_openloop_.controller_index());
+
+  Eigen::Matrix<double, 3, 1> Y;
+  Y << position->left_encoder, position->right_encoder, last_gyro_rate_;
+  kf_.Correct(Y);
+  integrated_kf_heading_ +=
+      kDt * (kf_.X_hat(3, 0) - kf_.X_hat(1, 0)) / (kRobotRadius * 2.0);
+
+  // To validate, look at the following:
+
+  // Observed - dx/dt velocity for left, right.
+
+  // Angular velocity error compared to the gyro
+  // Gyro heading vs left-right
+  // Voltage error.
+
+  Eigen::Matrix<double, 2, 1> U;
+  U << last_left_voltage_, last_right_voltage_;
+  last_left_voltage_ = left_voltage;
+  last_right_voltage_ = right_voltage;
+
+  kf_.UpdateObserver(U);
+}
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
diff --git a/y2012/control_loops/drivetrain/drivetrain.h b/y2012/control_loops/drivetrain/drivetrain.h
new file mode 100644
index 0000000..6fcbca7
--- /dev/null
+++ b/y2012/control_loops/drivetrain/drivetrain.h
@@ -0,0 +1,55 @@
+#ifndef Y2014_CONTROL_LOOPS_DRIVETRAIN_H_
+#define Y2014_CONTROL_LOOPS_DRIVETRAIN_H_
+
+#include "Eigen/Dense"
+
+#include "aos/common/controls/polytope.h"
+#include "aos/common/controls/control_loop.h"
+#include "aos/common/controls/polytope.h"
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "y2012/control_loops/drivetrain/polydrivetrain.h"
+#include "y2012/control_loops/drivetrain/ssdrivetrain.h"
+#include "aos/common/util/log_interval.h"
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+class DrivetrainLoop : public aos::controls::ControlLoop<
+                           ::y2012::control_loops::DrivetrainQueue> {
+ public:
+  // Constructs a control loop which can take a Drivetrain or defaults to the
+  // drivetrain at y2012::control_loops::drivetrain
+  explicit DrivetrainLoop(
+      ::y2012::control_loops::DrivetrainQueue *my_drivetrain =
+          &::y2012::control_loops::drivetrain_queue);
+
+ protected:
+  // Executes one cycle of the control loop.
+  virtual void RunIteration(
+      const ::y2012::control_loops::DrivetrainQueue::Goal *goal,
+      const ::y2012::control_loops::DrivetrainQueue::Position *position,
+      ::y2012::control_loops::DrivetrainQueue::Output *output,
+      ::y2012::control_loops::DrivetrainQueue::Status *status);
+
+  typedef ::aos::util::SimpleLogInterval SimpleLogInterval;
+  SimpleLogInterval no_position_ = SimpleLogInterval(
+      ::aos::time::Time::InSeconds(0.25), WARNING, "no position");
+  double last_gyro_heading_ = 0.0;
+  double last_gyro_rate_ = 0.0;
+
+  PolyDrivetrain dt_openloop_;
+  DrivetrainMotorsSS dt_closedloop_;
+  StateFeedbackLoop<7, 2, 3> kf_;
+
+  double last_left_voltage_ = 0;
+  double last_right_voltage_ = 0;
+
+  double integrated_kf_heading_ = 0;
+};
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
+
+#endif  // Y2014_CONTROL_LOOPS_DRIVETRAIN_H_
diff --git a/y2012/control_loops/drivetrain/drivetrain.q b/y2012/control_loops/drivetrain/drivetrain.q
new file mode 100644
index 0000000..819a28f
--- /dev/null
+++ b/y2012/control_loops/drivetrain/drivetrain.q
@@ -0,0 +1,126 @@
+package y2012.control_loops;
+
+import "aos/common/controls/control_loops.q";
+
+// For logging information about what the code is doing with the shifters.
+struct GearLogging {
+  // Which controller is being used.
+  int8_t controller_index;
+  // Whether the left loop is the high-gear one.
+  bool left_loop_high;
+  // Whether the right loop is the high-gear one.
+  bool right_loop_high;
+  // The state of the left shifter.
+  int8_t left_state;
+  // The state of the right shifter.
+  int8_t right_state;
+};
+
+// For logging information about the state of the shifters.
+struct CIMLogging {
+  // Whether the code thinks the left side is currently in gear.
+  bool left_in_gear;
+  // Whether the code thinks the right side is currently in gear.
+  bool right_in_gear;
+  // The velocity in rad/s (positive forward) the code thinks the left motor
+  // is currently spinning at.
+  double left_motor_speed;
+  // The velocity in rad/s (positive forward) the code thinks the right motor
+  // is currently spinning at.
+  double right_motor_speed;
+  // The velocity estimate for the left side of the robot in m/s (positive
+  // forward) used for shifting.
+  double left_velocity;
+  // The velocity estimate for the right side of the robot in m/s (positive
+  // forward) used for shifting.
+  double right_velocity;
+};
+
+queue_group DrivetrainQueue {
+  implements aos.control_loops.ControlLoop;
+
+  message Goal {
+    // Position of the steering wheel (positive = turning left when going
+    // forwards).
+    double steering;
+    // Position of the throttle (positive forwards).
+    double throttle;
+    // True to shift into high, false to shift into low.
+    bool highgear;
+    // True to activate quickturn.
+    bool quickturn;
+    // True to have the closed-loop controller take over.
+    bool control_loop_driving;
+    // Position goal for the left side in meters when the closed-loop controller
+    // is active.
+    double left_goal;
+    // Velocity goal for the left side in m/s when the closed-loop controller
+    // is active.
+    double left_velocity_goal;
+    // Position goal for the right side in meters when the closed-loop
+    // controller is active.
+    double right_goal;
+    // Velocity goal for the right side in m/s when the closed-loop controller
+    // is active.
+    double right_velocity_goal;
+  };
+
+  message Position {
+    // Relative position of the left side in meters.
+    double left_encoder;
+    // Relative position of the right side in meters.
+    double right_encoder;
+    // The speed in m/s of the left side from the most recent encoder pulse,
+    // or 0 if there was no edge within the last 5ms.
+    double left_speed;
+    // The speed in m/s of the right side from the most recent encoder pulse,
+    // or 0 if there was no edge within the last 5ms.
+    double right_speed;
+    // Position of the left shifter (smaller = towards low gear).
+    double left_shifter_position;
+    // Position of the right shifter (smaller = towards low gear).
+    double right_shifter_position;
+    double low_left_hall;
+    double high_left_hall;
+    double low_right_hall;
+    double high_right_hall;
+  };
+
+  message Output {
+    // Voltage to send to the left motor(s).
+    double left_voltage;
+    // Voltage to send to the right motor(s).
+    double right_voltage;
+    // True to set the left shifter piston for high gear.
+    bool left_high;
+    // True to set the right shifter piston for high gear.
+    bool right_high;
+  };
+
+  message Status {
+    // Estimated speed of the center of the robot in m/s (positive forwards).
+    double robot_speed;
+    // Estimated relative position of the left side in meters.
+    double filtered_left_position;
+    // Estimated relative position of the right side in meters.
+    double filtered_right_position;
+    // Estimated velocity of the left side in m/s.
+    double filtered_left_velocity;
+    // Estimated velocity of the left side in m/s.
+    double filtered_right_velocity;
+
+    // The voltage we wanted to send to the left side last cycle.
+    double uncapped_left_voltage;
+    // The voltage we wanted to send to the right side last cycle.
+    double uncapped_right_voltage;
+    // True if the output voltage was capped last cycle.
+    bool output_was_capped;
+  };
+
+  queue Goal goal;
+  queue Position position;
+  queue Output output;
+  queue Status status;
+};
+
+queue_group DrivetrainQueue drivetrain_queue;
diff --git a/y2012/control_loops/drivetrain/drivetrain_main.cc b/y2012/control_loops/drivetrain/drivetrain_main.cc
new file mode 100644
index 0000000..ddff516
--- /dev/null
+++ b/y2012/control_loops/drivetrain/drivetrain_main.cc
@@ -0,0 +1,11 @@
+#include "y2012/control_loops/drivetrain/drivetrain.h"
+
+#include "aos/linux_code/init.h"
+
+int main() {
+  ::aos::Init();
+  ::y2012::control_loops::drivetrain::DrivetrainLoop drivetrain;
+  drivetrain.Run();
+  ::aos::Cleanup();
+  return 0;
+}
diff --git a/y2012/control_loops/drivetrain/polydrivetrain.cc b/y2012/control_loops/drivetrain/polydrivetrain.cc
new file mode 100644
index 0000000..598d635
--- /dev/null
+++ b/y2012/control_loops/drivetrain/polydrivetrain.cc
@@ -0,0 +1,332 @@
+#include "y2012/control_loops/drivetrain/polydrivetrain.h"
+
+#include "aos/common/logging/logging.h"
+#include "aos/common/controls/polytope.h"
+#include "aos/common/commonmath.h"
+#include "aos/common/logging/queue_logging.h"
+#include "aos/common/logging/matrix_logging.h"
+
+#include "aos/common/messages/robot_state.q.h"
+#include "frc971/control_loops/state_feedback_loop.h"
+#include "frc971/control_loops/coerce_goal.h"
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "y2012/control_loops/drivetrain/drivetrain_dog_motor_plant.h"
+#include "y2012/control_loops/drivetrain/polydrivetrain_dog_motor_plant.h"
+
+#define HAVE_SHIFTERS 1
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+using ::y2012::control_loops::GearLogging;
+using ::y2012::control_loops::CIMLogging;
+using ::frc971::control_loops::CoerceGoal;
+
+PolyDrivetrain::PolyDrivetrain()
+    : U_Poly_((Eigen::Matrix<double, 4, 2>() << /*[[*/ 1, 0 /*]*/,
+               /*[*/ -1, 0 /*]*/,
+               /*[*/ 0, 1 /*]*/,
+               /*[*/ 0, -1 /*]]*/).finished(),
+              (Eigen::Matrix<double, 4, 1>() << /*[[*/ 12 /*]*/,
+               /*[*/ 12 /*]*/,
+               /*[*/ 12 /*]*/,
+               /*[*/ 12 /*]]*/).finished()),
+      loop_(new StateFeedbackLoop<2, 2, 2>(
+          ::y2012::control_loops::drivetrain::MakeVelocityDrivetrainLoop())),
+      ttrust_(1.1),
+      wheel_(0.0),
+      throttle_(0.0),
+      quickturn_(false),
+      stale_count_(0),
+      position_time_delta_(kDt),
+      left_gear_(LOW),
+      right_gear_(LOW),
+      counter_(0) {
+  last_position_.Zero();
+  position_.Zero();
+}
+
+double PolyDrivetrain::MotorSpeed(bool high_gear, double velocity) {
+  if (high_gear) {
+    return velocity / kHighGearRatio / kWheelRadius;
+  } else {
+    return velocity / kLowGearRatio / kWheelRadius;
+  }
+}
+
+void PolyDrivetrain::SetGoal(double wheel, double throttle, bool quickturn,
+                             bool highgear) {
+  const double kWheelNonLinearity = 0.3;
+  // Apply a sin function that's scaled to make it feel better.
+  const double angular_range = M_PI_2 * kWheelNonLinearity;
+
+  wheel_ = sin(angular_range * wheel) / sin(angular_range);
+  wheel_ = sin(angular_range * wheel_) / sin(angular_range);
+  quickturn_ = quickturn;
+
+  static const double kThrottleDeadband = 0.05;
+  if (::std::abs(throttle) < kThrottleDeadband) {
+    throttle_ = 0;
+  } else {
+    throttle_ = copysign(
+        (::std::abs(throttle) - kThrottleDeadband) / (1.0 - kThrottleDeadband),
+        throttle);
+  }
+
+  // TODO(austin): Fix the upshift logic to include states.
+  Gear requested_gear = highgear ? HIGH : LOW;
+
+  const Gear shift_up = HIGH;
+  const Gear shift_down = LOW;
+
+  if (left_gear_ != requested_gear) {
+    if (IsInGear(left_gear_)) {
+      if (requested_gear == HIGH) {
+        left_gear_ = shift_up;
+      } else {
+        left_gear_ = shift_down;
+      }
+    } else {
+      if (requested_gear == HIGH && left_gear_ == SHIFTING_DOWN) {
+        left_gear_ = SHIFTING_UP;
+      } else if (requested_gear == LOW && left_gear_ == SHIFTING_UP) {
+        left_gear_ = SHIFTING_DOWN;
+      }
+    }
+  }
+  if (right_gear_ != requested_gear) {
+    if (IsInGear(right_gear_)) {
+      if (requested_gear == HIGH) {
+        right_gear_ = shift_up;
+      } else {
+        right_gear_ = shift_down;
+      }
+    } else {
+      if (requested_gear == HIGH && right_gear_ == SHIFTING_DOWN) {
+        right_gear_ = SHIFTING_UP;
+      } else if (requested_gear == LOW && right_gear_ == SHIFTING_UP) {
+        right_gear_ = SHIFTING_DOWN;
+      }
+    }
+  }
+}
+void PolyDrivetrain::SetPosition(
+    const ::y2012::control_loops::DrivetrainQueue::Position *position) {
+  if (position == NULL) {
+    ++stale_count_;
+  } else {
+    last_position_ = position_;
+    position_ = *position;
+    position_time_delta_ = (stale_count_ + 1) * kDt;
+    stale_count_ = 0;
+  }
+
+#if HAVE_SHIFTERS
+  if (position) {
+    if (left_gear_ == LOW) {
+      if (right_gear_ == LOW) {
+        loop_->set_controller_index(0);
+      } else {
+        loop_->set_controller_index(1);
+      }
+    } else {
+      if (right_gear_ == LOW) {
+        loop_->set_controller_index(2);
+      } else {
+        loop_->set_controller_index(3);
+      }
+    }
+  }
+#endif
+}
+
+double PolyDrivetrain::FilterVelocity(double throttle) {
+  const Eigen::Matrix<double, 2, 2> FF =
+      loop_->B().inverse() *
+      (Eigen::Matrix<double, 2, 2>::Identity() - loop_->A());
+
+  constexpr int kHighGearController = 3;
+  const Eigen::Matrix<double, 2, 2> FF_high =
+      loop_->controller(kHighGearController).plant.B().inverse() *
+      (Eigen::Matrix<double, 2, 2>::Identity() -
+       loop_->controller(kHighGearController).plant.A());
+
+  ::Eigen::Matrix<double, 1, 2> FF_sum = FF.colwise().sum();
+  int min_FF_sum_index;
+  const double min_FF_sum = FF_sum.minCoeff(&min_FF_sum_index);
+  const double min_K_sum = loop_->K().col(min_FF_sum_index).sum();
+  const double high_min_FF_sum = FF_high.col(0).sum();
+
+  const double adjusted_ff_voltage =
+      ::aos::Clip(throttle * 12.0 * min_FF_sum / high_min_FF_sum, -12.0, 12.0);
+  return (adjusted_ff_voltage +
+          ttrust_ * min_K_sum * (loop_->X_hat(0, 0) + loop_->X_hat(1, 0)) /
+              2.0) /
+         (ttrust_ * min_K_sum + min_FF_sum);
+}
+
+double PolyDrivetrain::MaxVelocity() {
+  const Eigen::Matrix<double, 2, 2> FF =
+      loop_->B().inverse() *
+      (Eigen::Matrix<double, 2, 2>::Identity() - loop_->A());
+
+  constexpr int kHighGearController = 3;
+  const Eigen::Matrix<double, 2, 2> FF_high =
+      loop_->controller(kHighGearController).plant.B().inverse() *
+      (Eigen::Matrix<double, 2, 2>::Identity() -
+       loop_->controller(kHighGearController).plant.A());
+
+  ::Eigen::Matrix<double, 1, 2> FF_sum = FF.colwise().sum();
+  int min_FF_sum_index;
+  const double min_FF_sum = FF_sum.minCoeff(&min_FF_sum_index);
+  // const double min_K_sum = loop_->K().col(min_FF_sum_index).sum();
+  const double high_min_FF_sum = FF_high.col(0).sum();
+
+  const double adjusted_ff_voltage =
+      ::aos::Clip(12.0 * min_FF_sum / high_min_FF_sum, -12.0, 12.0);
+  return adjusted_ff_voltage / min_FF_sum;
+}
+
+void PolyDrivetrain::Update() {
+  // TODO(austin): Observer for the current velocity instead of difference
+  // calculations.
+  ++counter_;
+#if HAVE_SHIFTERS
+  const double current_left_velocity =
+      (position_.left_encoder - last_position_.left_encoder) /
+      position_time_delta_;
+  const double current_right_velocity =
+      (position_.right_encoder - last_position_.right_encoder) /
+      position_time_delta_;
+  const double left_motor_speed =
+      MotorSpeed(left_gear_ == HIGH, current_left_velocity);
+  const double right_motor_speed =
+      MotorSpeed(right_gear_ == HIGH, current_right_velocity);
+
+  {
+    CIMLogging logging;
+
+    // Reset the CIM model to the current conditions to be ready for when we
+    // shift.
+    if (IsInGear(left_gear_)) {
+      logging.left_in_gear = true;
+    } else {
+      logging.left_in_gear = false;
+    }
+    logging.left_motor_speed = left_motor_speed;
+    logging.left_velocity = current_left_velocity;
+    if (IsInGear(right_gear_)) {
+      logging.right_in_gear = true;
+    } else {
+      logging.right_in_gear = false;
+    }
+    logging.right_motor_speed = right_motor_speed;
+    logging.right_velocity = current_right_velocity;
+
+    LOG_STRUCT(DEBUG, "currently", logging);
+  }
+#endif
+
+#if HAVE_SHIFTERS
+  if (IsInGear(left_gear_) && IsInGear(right_gear_))
+#endif
+  {
+    // FF * X = U (steady state)
+    const Eigen::Matrix<double, 2, 2> FF =
+        loop_->B().inverse() *
+        (Eigen::Matrix<double, 2, 2>::Identity() - loop_->A());
+
+    // Invert the plant to figure out how the velocity filter would have to
+    // work
+    // out in order to filter out the forwards negative inertia.
+    // This math assumes that the left and right power and velocity are
+    // equals,
+    // and that the plant is the same on the left and right.
+    const double fvel = FilterVelocity(throttle_);
+
+    const double sign_svel = wheel_ * ((fvel > 0.0) ? 1.0 : -1.0);
+    double steering_velocity;
+    if (quickturn_) {
+      steering_velocity = wheel_ * MaxVelocity();
+    } else {
+      steering_velocity = ::std::abs(fvel) * wheel_;
+    }
+    const double left_velocity = fvel - steering_velocity;
+    const double right_velocity = fvel + steering_velocity;
+
+    // Integrate velocity to get the position.
+    // This position is used to get integral control.
+    loop_->mutable_R() << left_velocity, right_velocity;
+
+    if (!quickturn_) {
+      // K * R = w
+      Eigen::Matrix<double, 1, 2> equality_k;
+      equality_k << 1 + sign_svel, -(1 - sign_svel);
+      const double equality_w = 0.0;
+
+      // Construct a constraint on R by manipulating the constraint on U
+      ::aos::controls::HPolytope<2> R_poly = ::aos::controls::HPolytope<2>(
+          U_Poly_.H() * (loop_->K() + FF),
+          U_Poly_.k() + U_Poly_.H() * loop_->K() * loop_->X_hat());
+
+      // Limit R back inside the box.
+      loop_->mutable_R() =
+          CoerceGoal(R_poly, equality_k, equality_w, loop_->R());
+    }
+
+    const Eigen::Matrix<double, 2, 1> FF_volts = FF * loop_->R();
+    const Eigen::Matrix<double, 2, 1> U_ideal =
+        loop_->K() * (loop_->R() - loop_->X_hat()) + FF_volts;
+
+    for (int i = 0; i < 2; i++) {
+      loop_->mutable_U()[i] = ::aos::Clip(U_ideal[i], -12, 12);
+    }
+
+    // TODO(austin): Model this better.
+    // TODO(austin): Feed back?
+    loop_->mutable_X_hat() =
+        loop_->A() * loop_->X_hat() + loop_->B() * loop_->U();
+#if HAVE_SHIFTERS
+  } else {
+    // Any motor is not in gear.  Speed match.
+    ::Eigen::Matrix<double, 1, 1> R_left;
+    ::Eigen::Matrix<double, 1, 1> R_right;
+    R_left(0, 0) = left_motor_speed;
+    R_right(0, 0) = right_motor_speed;
+
+    const double wiggle =
+        (static_cast<double>((counter_ % 20) / 10) - 0.5) * 5.0;
+
+    loop_->mutable_U(0, 0) = ::aos::Clip(
+        (R_left / Kv)(0, 0) + (IsInGear(left_gear_) ? 0 : wiggle), -12.0, 12.0);
+    loop_->mutable_U(1, 0) =
+        ::aos::Clip((R_right / Kv)(0, 0) + (IsInGear(right_gear_) ? 0 : wiggle),
+                    -12.0, 12.0);
+    loop_->mutable_U() *= 12.0 / ::aos::robot_state->voltage_battery;
+#endif
+  }
+}
+
+void PolyDrivetrain::SendMotors(
+    ::y2012::control_loops::DrivetrainQueue::Output *output) {
+  if (output != NULL) {
+    output->left_voltage = loop_->U(0, 0);
+    output->right_voltage = loop_->U(1, 0);
+    output->left_high = left_gear_ == HIGH || left_gear_ == SHIFTING_UP;
+    output->right_high = right_gear_ == HIGH || right_gear_ == SHIFTING_UP;
+  }
+}
+
+constexpr double PolyDrivetrain::kStallTorque;
+constexpr double PolyDrivetrain::kStallCurrent;
+constexpr double PolyDrivetrain::kFreeSpeed;
+constexpr double PolyDrivetrain::kFreeCurrent;
+constexpr double PolyDrivetrain::kWheelRadius;
+constexpr double PolyDrivetrain::kR;
+constexpr double PolyDrivetrain::Kv;
+constexpr double PolyDrivetrain::Kt;
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
diff --git a/y2012/control_loops/drivetrain/polydrivetrain.h b/y2012/control_loops/drivetrain/polydrivetrain.h
new file mode 100644
index 0000000..73dcc8b
--- /dev/null
+++ b/y2012/control_loops/drivetrain/polydrivetrain.h
@@ -0,0 +1,80 @@
+#ifndef Y2014_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_
+#define Y2014_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_
+
+#include "aos/common/controls/polytope.h"
+
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "frc971/control_loops/state_feedback_loop.h"
+#include "y2012/control_loops/drivetrain/drivetrain_dog_motor_plant.h"
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+class PolyDrivetrain {
+ public:
+  enum Gear { HIGH, LOW, SHIFTING_UP, SHIFTING_DOWN };
+  // Stall Torque in N m
+  static constexpr double kStallTorque = drivetrain::kStallTorque;
+  // Stall Current in Amps
+  static constexpr double kStallCurrent = drivetrain::kStallCurrent;
+  // Free Speed in RPM. Used number from last year.
+  static constexpr double kFreeSpeed = drivetrain::kFreeSpeedRPM;
+  // Free Current in Amps
+  static constexpr double kFreeCurrent = drivetrain::kFreeCurrent;
+  static constexpr double kWheelRadius = drivetrain::kWheelRadius;
+  // Resistance of the motor, divided by the number of motors per side.
+  static constexpr double kR = drivetrain::kR;
+  // Motor velocity constant
+  static constexpr double Kv = drivetrain::kV;
+
+  // Torque constant
+  static constexpr double Kt = drivetrain::kT;
+
+  static constexpr double kLowGearRatio = 15.0 / 60.0 * 15.0 / 50.0;
+  static constexpr double kHighGearRatio = 30.0 / 45.0 * 15.0 / 50.0;
+
+  PolyDrivetrain();
+
+  int controller_index() const { return loop_->controller_index(); }
+
+  static bool IsInGear(Gear gear) { return gear == LOW || gear == HIGH; }
+
+  static double MotorSpeed(bool high_gear, double velocity);
+
+  void SetGoal(double wheel, double throttle, bool quickturn, bool highgear);
+
+  void SetPosition(
+      const ::y2012::control_loops::DrivetrainQueue::Position *position);
+
+  double FilterVelocity(double throttle);
+
+  double MaxVelocity();
+
+  void Update();
+
+  void SendMotors(::y2012::control_loops::DrivetrainQueue::Output *output);
+
+ private:
+  const ::aos::controls::HPolytope<2> U_Poly_;
+
+  ::std::unique_ptr<StateFeedbackLoop<2, 2, 2>> loop_;
+
+  const double ttrust_;
+  double wheel_;
+  double throttle_;
+  bool quickturn_;
+  int stale_count_;
+  double position_time_delta_;
+  Gear left_gear_;
+  Gear right_gear_;
+  ::y2012::control_loops::DrivetrainQueue::Position last_position_;
+  ::y2012::control_loops::DrivetrainQueue::Position position_;
+  int counter_;
+};
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
+
+#endif  // Y2014_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_
diff --git a/y2012/control_loops/drivetrain/replay_drivetrain.cc b/y2012/control_loops/drivetrain/replay_drivetrain.cc
new file mode 100644
index 0000000..db03741
--- /dev/null
+++ b/y2012/control_loops/drivetrain/replay_drivetrain.cc
@@ -0,0 +1,36 @@
+#include "aos/common/controls/replay_control_loop.h"
+#include "aos/linux_code/init.h"
+
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "frc971/queues/gyro.q.h"
+
+// Reads one or more log files and sends out all the queue messages (in the
+// correct order and at the correct time) to feed a "live" drivetrain process.
+
+int main(int argc, char **argv) {
+  if (argc <= 1) {
+    fprintf(stderr, "Need at least one file to replay!\n");
+    return EXIT_FAILURE;
+  }
+
+  ::aos::InitNRT();
+
+  {
+    ::aos::controls::ControlLoopReplayer<
+        ::y2012::control_loops::DrivetrainQueue>
+        replayer(&::y2012::control_loops::drivetrain_queue, "drivetrain");
+
+    replayer.AddDirectQueueSender("wpilib_interface.Gyro", "sending",
+                                  ::frc971::sensors::gyro_reading);
+    for (int i = 1; i < argc; ++i) {
+      replayer.ProcessFile(argv[i]);
+    }
+  }
+  ::frc971::sensors::gyro_reading.Clear();
+  ::y2012::control_loops::drivetrain_queue.goal.Clear();
+  ::y2012::control_loops::drivetrain_queue.status.Clear();
+  ::y2012::control_loops::drivetrain_queue.position.Clear();
+  ::y2012::control_loops::drivetrain_queue.output.Clear();
+
+  ::aos::Cleanup();
+}
diff --git a/y2012/control_loops/drivetrain/ssdrivetrain.cc b/y2012/control_loops/drivetrain/ssdrivetrain.cc
new file mode 100644
index 0000000..0dd3eb1
--- /dev/null
+++ b/y2012/control_loops/drivetrain/ssdrivetrain.cc
@@ -0,0 +1,186 @@
+#include "y2012/control_loops/drivetrain/ssdrivetrain.h"
+
+#include "aos/common/controls/polytope.h"
+#include "aos/common/commonmath.h"
+#include "aos/common/logging/matrix_logging.h"
+
+#include "frc971/control_loops/state_feedback_loop.h"
+#include "frc971/control_loops/coerce_goal.h"
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+#include "y2012/control_loops/drivetrain/drivetrain_dog_motor_plant.h"
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+using ::frc971::control_loops::DoCoerceGoal;
+
+DrivetrainMotorsSS::LimitedDrivetrainLoop::LimitedDrivetrainLoop(
+    StateFeedbackLoop<4, 2, 2> &&loop)
+    : StateFeedbackLoop<4, 2, 2>(::std::move(loop)),
+      U_Poly_((Eigen::Matrix<double, 4, 2>() << 1, 0, -1, 0, 0, 1, 0, -1)
+                  .finished(),
+              (Eigen::Matrix<double, 4, 1>() << 12.0, 12.0, 12.0, 12.0)
+                  .finished()) {
+  ::aos::controls::HPolytope<0>::Init();
+  T << 1, -1, 1, 1;
+  T_inverse = T.inverse();
+}
+
+void DrivetrainMotorsSS::LimitedDrivetrainLoop::CapU() {
+  const Eigen::Matrix<double, 4, 1> error = R() - X_hat();
+
+  if (::std::abs(U(0, 0)) > 12.0 || ::std::abs(U(1, 0)) > 12.0) {
+    mutable_U() =
+        U() * 12.0 / ::std::max(::std::abs(U(0, 0)), ::std::abs(U(1, 0)));
+    LOG_MATRIX(DEBUG, "U is now", U());
+    // TODO(Austin): Figure out why the polytope stuff wasn't working and
+    // remove this hack.
+    output_was_capped_ = true;
+    return;
+
+    LOG_MATRIX(DEBUG, "U at start", U());
+    LOG_MATRIX(DEBUG, "R at start", R());
+    LOG_MATRIX(DEBUG, "Xhat at start", X_hat());
+
+    Eigen::Matrix<double, 2, 2> position_K;
+    position_K << K(0, 0), K(0, 2), K(1, 0), K(1, 2);
+    Eigen::Matrix<double, 2, 2> velocity_K;
+    velocity_K << K(0, 1), K(0, 3), K(1, 1), K(1, 3);
+
+    Eigen::Matrix<double, 2, 1> position_error;
+    position_error << error(0, 0), error(2, 0);
+    const auto drive_error = T_inverse * position_error;
+    Eigen::Matrix<double, 2, 1> velocity_error;
+    velocity_error << error(1, 0), error(3, 0);
+    LOG_MATRIX(DEBUG, "error", error);
+
+    const auto &poly = U_Poly_;
+    const Eigen::Matrix<double, 4, 2> pos_poly_H = poly.H() * position_K * T;
+    const Eigen::Matrix<double, 4, 1> pos_poly_k =
+        poly.k() - poly.H() * velocity_K * velocity_error;
+    const ::aos::controls::HPolytope<2> pos_poly(pos_poly_H, pos_poly_k);
+
+    Eigen::Matrix<double, 2, 1> adjusted_pos_error;
+    {
+      const auto &P = drive_error;
+
+      Eigen::Matrix<double, 1, 2> L45;
+      L45 << ::aos::sign(P(1, 0)), -::aos::sign(P(0, 0));
+      const double w45 = 0;
+
+      Eigen::Matrix<double, 1, 2> LH;
+      if (::std::abs(P(0, 0)) > ::std::abs(P(1, 0))) {
+        LH << 0, 1;
+      } else {
+        LH << 1, 0;
+      }
+      const double wh = LH.dot(P);
+
+      Eigen::Matrix<double, 2, 2> standard;
+      standard << L45, LH;
+      Eigen::Matrix<double, 2, 1> W;
+      W << w45, wh;
+      const Eigen::Matrix<double, 2, 1> intersection = standard.inverse() * W;
+
+      bool is_inside_h;
+      const auto adjusted_pos_error_h =
+          DoCoerceGoal(pos_poly, LH, wh, drive_error, &is_inside_h);
+      const auto adjusted_pos_error_45 =
+          DoCoerceGoal(pos_poly, L45, w45, intersection, nullptr);
+      if (pos_poly.IsInside(intersection)) {
+        adjusted_pos_error = adjusted_pos_error_h;
+      } else {
+        if (is_inside_h) {
+          if (adjusted_pos_error_h.norm() > adjusted_pos_error_45.norm()) {
+            adjusted_pos_error = adjusted_pos_error_h;
+          } else {
+            adjusted_pos_error = adjusted_pos_error_45;
+          }
+        } else {
+          adjusted_pos_error = adjusted_pos_error_45;
+        }
+      }
+    }
+
+    LOG_MATRIX(DEBUG, "adjusted_pos_error", adjusted_pos_error);
+    mutable_U() =
+        velocity_K * velocity_error + position_K * T * adjusted_pos_error;
+    LOG_MATRIX(DEBUG, "U is now", U());
+  } else {
+    output_was_capped_ = false;
+  }
+}
+
+DrivetrainMotorsSS::DrivetrainMotorsSS()
+    : loop_(new LimitedDrivetrainLoop(
+          ::y2012::control_loops::drivetrain::MakeDrivetrainLoop())),
+      filtered_offset_(0.0),
+      gyro_(0.0),
+      left_goal_(0.0),
+      right_goal_(0.0),
+      raw_left_(0.0),
+      raw_right_(0.0) {
+  // High gear on both.
+  loop_->set_controller_index(3);
+}
+
+void DrivetrainMotorsSS::SetGoal(double left, double left_velocity,
+                                 double right, double right_velocity) {
+  left_goal_ = left;
+  right_goal_ = right;
+  loop_->mutable_R() << left, left_velocity, right, right_velocity;
+}
+void DrivetrainMotorsSS::SetRawPosition(double left, double right) {
+  raw_right_ = right;
+  raw_left_ = left;
+  Eigen::Matrix<double, 2, 1> Y;
+  Y << left + filtered_offset_, right - filtered_offset_;
+  loop_->Correct(Y);
+}
+void DrivetrainMotorsSS::SetPosition(double left, double right, double gyro) {
+  // Decay the offset quickly because this gyro is great.
+  const double offset =
+      (right - left - gyro * 0.5) / 2.0;
+  filtered_offset_ = 0.25 * offset + 0.75 * filtered_offset_;
+  gyro_ = gyro;
+  SetRawPosition(left, right);
+}
+
+void DrivetrainMotorsSS::SetExternalMotors(double left_voltage,
+                                           double right_voltage) {
+  loop_->mutable_U() << left_voltage, right_voltage;
+}
+
+void DrivetrainMotorsSS::Update(bool stop_motors, bool enable_control_loop) {
+  if (enable_control_loop) {
+    loop_->Update(stop_motors);
+  } else {
+    if (stop_motors) {
+      loop_->mutable_U().setZero();
+      loop_->mutable_U_uncapped().setZero();
+    }
+    loop_->UpdateObserver(loop_->U());
+  }
+  ::Eigen::Matrix<double, 4, 1> E = loop_->R() - loop_->X_hat();
+  LOG_MATRIX(DEBUG, "E", E);
+}
+
+double DrivetrainMotorsSS::GetEstimatedRobotSpeed() const {
+  // lets just call the average of left and right velocities close enough
+  return (loop_->X_hat(1, 0) + loop_->X_hat(3, 0)) / 2;
+}
+
+void DrivetrainMotorsSS::SendMotors(
+    ::y2012::control_loops::DrivetrainQueue::Output *output) const {
+  if (output) {
+    output->left_voltage = loop_->U(0, 0);
+    output->right_voltage = loop_->U(1, 0);
+    output->left_high = true;
+    output->right_high = true;
+  }
+}
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
diff --git a/y2012/control_loops/drivetrain/ssdrivetrain.h b/y2012/control_loops/drivetrain/ssdrivetrain.h
new file mode 100644
index 0000000..76df3fd
--- /dev/null
+++ b/y2012/control_loops/drivetrain/ssdrivetrain.h
@@ -0,0 +1,84 @@
+#ifndef Y2014_CONTROL_LOOPS_DRIVETRAIN_SSDRIVETRAIN_H_
+#define Y2014_CONTROL_LOOPS_DRIVETRAIN_SSDRIVETRAIN_H_
+
+#include "aos/common/controls/polytope.h"
+#include "aos/common/commonmath.h"
+#include "aos/common/logging/matrix_logging.h"
+
+#include "frc971/control_loops/state_feedback_loop.h"
+#include "frc971/control_loops/coerce_goal.h"
+#include "y2012/control_loops/drivetrain/drivetrain.q.h"
+
+namespace y2012 {
+namespace control_loops {
+namespace drivetrain {
+
+class DrivetrainMotorsSS {
+ public:
+  class LimitedDrivetrainLoop : public StateFeedbackLoop<4, 2, 2> {
+   public:
+    LimitedDrivetrainLoop(StateFeedbackLoop<4, 2, 2> &&loop);
+
+    bool output_was_capped() const {
+      return output_was_capped_;
+    }
+
+   private:
+    void CapU() override;
+
+    const ::aos::controls::HPolytope<2> U_Poly_;
+    Eigen::Matrix<double, 2, 2> T, T_inverse;
+    bool output_was_capped_ = false;;
+  };
+
+  DrivetrainMotorsSS();
+
+  void SetGoal(double left, double left_velocity, double right,
+               double right_velocity);
+
+  void SetRawPosition(double left, double right);
+
+  void SetPosition(double left, double right, double gyro);
+
+  void SetExternalMotors(double left_voltage, double right_voltage);
+
+  void Update(bool stop_motors, bool enable_control_loop);
+
+  double GetEstimatedRobotSpeed() const;
+
+  double GetEstimatedLeftEncoder() const {
+    return loop_->X_hat(0, 0);
+  }
+
+  double left_velocity() const { return loop_->X_hat(1, 0); }
+  double right_velocity() const { return loop_->X_hat(3, 0); }
+
+  double GetEstimatedRightEncoder() const {
+    return loop_->X_hat(2, 0);
+  }
+
+  bool OutputWasCapped() const {
+    return loop_->output_was_capped();
+  }
+
+  void SendMotors(
+      ::y2012::control_loops::DrivetrainQueue::Output *output) const;
+
+  const LimitedDrivetrainLoop &loop() const { return *loop_; }
+
+ private:
+  ::std::unique_ptr<LimitedDrivetrainLoop> loop_;
+
+  double filtered_offset_;
+  double gyro_;
+  double left_goal_;
+  double right_goal_;
+  double raw_left_;
+  double raw_right_;
+};
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2012
+
+#endif  // Y2014_CONTROL_LOOPS_DRIVETRAIN_SSDRIVETRAIN_H_
diff --git a/y2012/control_loops/python/BUILD b/y2012/control_loops/python/BUILD
new file mode 100644
index 0000000..7e2b657
--- /dev/null
+++ b/y2012/control_loops/python/BUILD
@@ -0,0 +1,39 @@
+package(default_visibility = ['//y2012:__subpackages__'])
+
+py_binary(
+  name = 'drivetrain',
+  srcs = [
+    'drivetrain.py',
+  ],
+  deps = [
+    '//external:python-gflags',
+    '//external:python-glog',
+    '//frc971/control_loops/python:controls',
+  ],
+)
+
+py_binary(
+  name = 'polydrivetrain',
+  srcs = [
+    'polydrivetrain.py',
+    'drivetrain.py',
+  ],
+  deps = [
+    '//external:python-gflags',
+    '//external:python-glog',
+    '//frc971/control_loops/python:controls',
+  ],
+)
+
+py_library(
+  name = 'polydrivetrain_lib',
+  srcs = [
+    'polydrivetrain.py',
+    'drivetrain.py',
+  ],
+  deps = [
+    '//external:python-gflags',
+    '//external:python-glog',
+    '//frc971/control_loops/python:controls',
+  ],
+)
diff --git a/y2012/control_loops/python/drivetrain.py b/y2012/control_loops/python/drivetrain.py
new file mode 100755
index 0000000..291fe14
--- /dev/null
+++ b/y2012/control_loops/python/drivetrain.py
@@ -0,0 +1,351 @@
+#!/usr/bin/python
+
+from frc971.control_loops.python import control_loop
+from frc971.control_loops.python import controls
+import numpy
+import sys
+import argparse
+from matplotlib import pylab
+
+import gflags
+import glog
+
+FLAGS = gflags.FLAGS
+
+gflags.DEFINE_bool('plot', False, 'If true, plot the loop response.')
+
+class CIM(control_loop.ControlLoop):
+  def __init__(self):
+    super(CIM, self).__init__("CIM")
+    # Stall Torque in N m
+    self.stall_torque = 2.42
+    # Stall Current in Amps
+    self.stall_current = 133
+    # Free Speed in RPM
+    self.free_speed = 4650.0
+    # Free Current in Amps
+    self.free_current = 2.7
+    # Moment of inertia of the CIM in kg m^2
+    self.J = 0.0001
+    # Resistance of the motor, divided by 2 to account for the 2 motors
+    self.resistance = 12.0 / self.stall_current
+    # Motor velocity constant
+    self.Kv = ((self.free_speed / 60.0 * 2.0 * numpy.pi) /
+              (12.0 - self.resistance * self.free_current))
+    # Torque constant
+    self.Kt = self.stall_torque / self.stall_current
+    # Control loop time step
+    self.dt = 0.005
+
+    # State feedback matrices
+    self.A_continuous = numpy.matrix(
+        [[-self.Kt / self.Kv / (self.J * self.resistance)]])
+    self.B_continuous = numpy.matrix(
+        [[self.Kt / (self.J * self.resistance)]])
+    self.C = numpy.matrix([[1]])
+    self.D = numpy.matrix([[0]])
+
+    self.A, self.B = self.ContinuousToDiscrete(self.A_continuous,
+                                               self.B_continuous, self.dt)
+
+    self.PlaceControllerPoles([0.01])
+    self.PlaceObserverPoles([0.01])
+
+    self.U_max = numpy.matrix([[12.0]])
+    self.U_min = numpy.matrix([[-12.0]])
+
+    self.InitializeState()
+
+
+class Drivetrain(control_loop.ControlLoop):
+  def __init__(self, name="Drivetrain", left_low=True, right_low=True):
+    super(Drivetrain, self).__init__(name)
+    # Number of motors per side
+    self.num_motors = 2
+    # Stall Torque in N m
+    self.stall_torque = 2.42 * self.num_motors * 0.60
+    # Stall Current in Amps
+    self.stall_current = 133.0 * self.num_motors
+    # Free Speed in RPM. Used number from last year.
+    self.free_speed = 5500.0
+    # Free Current in Amps
+    self.free_current = 4.7 * self.num_motors
+    # Moment of inertia of the drivetrain in kg m^2
+    self.J = 1.5
+    # Mass of the robot, in kg.
+    self.m = 30
+    # Radius of the robot, in meters (from last year).
+    self.rb = 0.647998644 / 2.0
+    # Radius of the wheels, in meters.
+    self.r = .04445
+    # Resistance of the motor, divided by the number of motors.
+    self.resistance = 12.0 / self.stall_current
+    # Motor velocity constant
+    self.Kv = ((self.free_speed / 60.0 * 2.0 * numpy.pi) /
+               (12.0 - self.resistance * self.free_current))
+    # Torque constant
+    self.Kt = self.stall_torque / self.stall_current
+    # Gear ratios
+    self.G_low = 15.0 / 60.0 * 15.0 / 50.0
+    self.G_high = 30.0 / 45.0 * 15.0 / 50.0
+    if left_low:
+      self.Gl = self.G_low
+    else:
+      self.Gl = self.G_high
+    if right_low:
+      self.Gr = self.G_low
+    else:
+      self.Gr = self.G_high
+
+    # Control loop time step
+    self.dt = 0.005
+
+    # These describe the way that a given side of a robot will be influenced
+    # by the other side. Units of 1 / kg.
+    self.msp = 1.0 / self.m + self.rb * self.rb / self.J
+    self.msn = 1.0 / self.m - self.rb * self.rb / self.J
+    # The calculations which we will need for A and B.
+    self.tcl = -self.Kt / self.Kv / (self.Gl * self.Gl * self.resistance * self.r * self.r)
+    self.tcr = -self.Kt / self.Kv / (self.Gr * self.Gr * self.resistance * self.r * self.r)
+    self.mpl = self.Kt / (self.Gl * self.resistance * self.r)
+    self.mpr = self.Kt / (self.Gr * self.resistance * self.r)
+
+    # State feedback matrices
+    # X will be of the format
+    # [[positionl], [velocityl], [positionr], velocityr]]
+    self.A_continuous = numpy.matrix(
+        [[0, 1, 0, 0],
+         [0, self.msp * self.tcl, 0, self.msn * self.tcr],
+         [0, 0, 0, 1],
+         [0, self.msn * self.tcl, 0, self.msp * self.tcr]])
+    self.B_continuous = numpy.matrix(
+        [[0, 0],
+         [self.msp * self.mpl, self.msn * self.mpr],
+         [0, 0],
+         [self.msn * self.mpl, self.msp * self.mpr]])
+    self.C = numpy.matrix([[1, 0, 0, 0],
+                           [0, 0, 1, 0]])
+    self.D = numpy.matrix([[0, 0],
+                           [0, 0]])
+
+    self.A, self.B = self.ContinuousToDiscrete(
+        self.A_continuous, self.B_continuous, self.dt)
+
+    q_pos = 0.12
+    q_vel = 1.0
+    self.Q = numpy.matrix([[(1.0 / (q_pos ** 2.0)), 0.0, 0.0, 0.0],
+                           [0.0, (1.0 / (q_vel ** 2.0)), 0.0, 0.0],
+                           [0.0, 0.0, (1.0 / (q_pos ** 2.0)), 0.0],
+                           [0.0, 0.0, 0.0, (1.0 / (q_vel ** 2.0))]])
+
+    self.R = numpy.matrix([[(1.0 / (12.0 ** 2.0)), 0.0],
+                           [0.0, (1.0 / (12.0 ** 2.0))]])
+    self.K = controls.dlqr(self.A, self.B, self.Q, self.R)
+
+    glog.debug('DT K %s', name)
+    glog.debug(str(self.K))
+    glog.debug(str(numpy.linalg.eig(self.A - self.B * self.K)[0]))
+
+    self.hlp = 0.3
+    self.llp = 0.4
+    self.PlaceObserverPoles([self.hlp, self.hlp, self.llp, self.llp])
+
+    self.U_max = numpy.matrix([[12.0], [12.0]])
+    self.U_min = numpy.matrix([[-12.0], [-12.0]])
+    self.InitializeState()
+
+
+class KFDrivetrain(Drivetrain):
+  def __init__(self, name="KFDrivetrain", left_low=True, right_low=True):
+    super(KFDrivetrain, self).__init__(name, left_low, right_low)
+
+    self.unaugmented_A_continuous = self.A_continuous
+    self.unaugmented_B_continuous = self.B_continuous
+
+    # The states are
+    # The practical voltage applied to the wheels is
+    #   V_left = U_left + left_voltage_error
+    #
+    # [left position, left velocity, right position, right velocity,
+    #  left voltage error, right voltage error, angular_error]
+    self.A_continuous = numpy.matrix(numpy.zeros((7, 7)))
+    self.B_continuous = numpy.matrix(numpy.zeros((7, 2)))
+    self.A_continuous[0:4,0:4] = self.unaugmented_A_continuous
+    self.A_continuous[0:4,4:6] = self.unaugmented_B_continuous
+    self.B_continuous[0:4,0:2] = self.unaugmented_B_continuous
+    self.A_continuous[0,6] = 1
+    self.A_continuous[2,6] = -1
+
+    self.A, self.B = self.ContinuousToDiscrete(
+        self.A_continuous, self.B_continuous, self.dt)
+
+    self.C = numpy.matrix([[1, 0, 0, 0, 0, 0, 0],
+                           [0, 0, 1, 0, 0, 0, 0],
+                           [0, -0.5 / self.rb, 0, 0.5 / self.rb, 0, 0, 0]])
+
+    self.D = numpy.matrix([[0, 0],
+                           [0, 0],
+                           [0, 0]])
+
+    q_pos = 0.05
+    q_vel = 1.00
+    q_voltage = 10.0
+    q_encoder_uncertainty = 2.00
+
+    self.Q = numpy.matrix([[(q_pos ** 2.0), 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
+                           [0.0, (q_vel ** 2.0), 0.0, 0.0, 0.0, 0.0, 0.0],
+                           [0.0, 0.0, (q_pos ** 2.0), 0.0, 0.0, 0.0, 0.0],
+                           [0.0, 0.0, 0.0, (q_vel ** 2.0), 0.0, 0.0, 0.0],
+                           [0.0, 0.0, 0.0, 0.0, (q_voltage ** 2.0), 0.0, 0.0],
+                           [0.0, 0.0, 0.0, 0.0, 0.0, (q_voltage ** 2.0), 0.0],
+                           [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, (q_encoder_uncertainty ** 2.0)]])
+
+    r_pos =  0.0001
+    r_gyro = 0.000001
+    self.R = numpy.matrix([[(r_pos ** 2.0), 0.0, 0.0],
+                           [0.0, (r_pos ** 2.0), 0.0],
+                           [0.0, 0.0, (r_gyro ** 2.0)]])
+
+    # Solving for kf gains.
+    self.KalmanGain, self.Q_steady = controls.kalman(
+        A=self.A, B=self.B, C=self.C, Q=self.Q, R=self.R)
+
+    self.L = self.A * self.KalmanGain
+
+    # We need a nothing controller for the autogen code to be happy.
+    self.K = numpy.matrix(numpy.zeros((self.B.shape[1], self.A.shape[0])))
+
+
+def main(argv):
+  argv = FLAGS(argv)
+
+  # Simulate the response of the system to a step input.
+  drivetrain = Drivetrain()
+  simulated_left = []
+  simulated_right = []
+  for _ in xrange(100):
+    drivetrain.Update(numpy.matrix([[12.0], [12.0]]))
+    simulated_left.append(drivetrain.X[0, 0])
+    simulated_right.append(drivetrain.X[2, 0])
+
+  if FLAGS.plot:
+    pylab.plot(range(100), simulated_left)
+    pylab.plot(range(100), simulated_right)
+    pylab.show()
+
+  # Simulate forwards motion.
+  drivetrain = Drivetrain()
+  close_loop_left = []
+  close_loop_right = []
+  R = numpy.matrix([[1.0], [0.0], [1.0], [0.0]])
+  for _ in xrange(100):
+    U = numpy.clip(drivetrain.K * (R - drivetrain.X_hat),
+                   drivetrain.U_min, drivetrain.U_max)
+    drivetrain.UpdateObserver(U)
+    drivetrain.Update(U)
+    close_loop_left.append(drivetrain.X[0, 0])
+    close_loop_right.append(drivetrain.X[2, 0])
+
+  if FLAGS.plot:
+    pylab.plot(range(100), close_loop_left)
+    pylab.plot(range(100), close_loop_right)
+    pylab.show()
+
+  # Try turning in place
+  drivetrain = Drivetrain()
+  close_loop_left = []
+  close_loop_right = []
+  R = numpy.matrix([[-1.0], [0.0], [1.0], [0.0]])
+  for _ in xrange(100):
+    U = numpy.clip(drivetrain.K * (R - drivetrain.X_hat),
+                   drivetrain.U_min, drivetrain.U_max)
+    drivetrain.UpdateObserver(U)
+    drivetrain.Update(U)
+    close_loop_left.append(drivetrain.X[0, 0])
+    close_loop_right.append(drivetrain.X[2, 0])
+
+  if FLAGS.plot:
+    pylab.plot(range(100), close_loop_left)
+    pylab.plot(range(100), close_loop_right)
+    pylab.show()
+
+  # Try turning just one side.
+  drivetrain = Drivetrain()
+  close_loop_left = []
+  close_loop_right = []
+  R = numpy.matrix([[0.0], [0.0], [1.0], [0.0]])
+  for _ in xrange(100):
+    U = numpy.clip(drivetrain.K * (R - drivetrain.X_hat),
+                   drivetrain.U_min, drivetrain.U_max)
+    drivetrain.UpdateObserver(U)
+    drivetrain.Update(U)
+    close_loop_left.append(drivetrain.X[0, 0])
+    close_loop_right.append(drivetrain.X[2, 0])
+
+  if FLAGS.plot:
+    pylab.plot(range(100), close_loop_left)
+    pylab.plot(range(100), close_loop_right)
+    pylab.show()
+
+  # Write the generated constants out to a file.
+  drivetrain_low_low = Drivetrain(
+      name="DrivetrainLowLow", left_low=True, right_low=True)
+  drivetrain_low_high = Drivetrain(
+      name="DrivetrainLowHigh", left_low=True, right_low=False)
+  drivetrain_high_low = Drivetrain(
+      name="DrivetrainHighLow", left_low=False, right_low=True)
+  drivetrain_high_high = Drivetrain(
+      name="DrivetrainHighHigh", left_low=False, right_low=False)
+
+  kf_drivetrain_low_low = KFDrivetrain(
+      name="KFDrivetrainLowLow", left_low=True, right_low=True)
+  kf_drivetrain_low_high = KFDrivetrain(
+      name="KFDrivetrainLowHigh", left_low=True, right_low=False)
+  kf_drivetrain_high_low = KFDrivetrain(
+      name="KFDrivetrainHighLow", left_low=False, right_low=True)
+  kf_drivetrain_high_high = KFDrivetrain(
+      name="KFDrivetrainHighHigh", left_low=False, right_low=False)
+
+  if len(argv) != 5:
+    print "Expected .h file name and .cc file name"
+  else:
+    namespaces = ['y2012', 'control_loops', 'drivetrain']
+    dog_loop_writer = control_loop.ControlLoopWriter(
+        "Drivetrain", [drivetrain_low_low, drivetrain_low_high,
+                       drivetrain_high_low, drivetrain_high_high],
+        namespaces = namespaces)
+    dog_loop_writer.AddConstant(control_loop.Constant("kDt", "%f",
+          drivetrain_low_low.dt))
+    dog_loop_writer.AddConstant(control_loop.Constant("kStallTorque", "%f",
+          drivetrain_low_low.stall_torque))
+    dog_loop_writer.AddConstant(control_loop.Constant("kStallCurrent", "%f",
+          drivetrain_low_low.stall_current))
+    dog_loop_writer.AddConstant(control_loop.Constant("kFreeSpeedRPM", "%f",
+          drivetrain_low_low.free_speed))
+    dog_loop_writer.AddConstant(control_loop.Constant("kFreeCurrent", "%f",
+          drivetrain_low_low.free_current))
+    dog_loop_writer.AddConstant(control_loop.Constant("kJ", "%f",
+          drivetrain_low_low.J))
+    dog_loop_writer.AddConstant(control_loop.Constant("kMass", "%f",
+          drivetrain_low_low.m))
+    dog_loop_writer.AddConstant(control_loop.Constant("kRobotRadius", "%f",
+          drivetrain_low_low.rb))
+    dog_loop_writer.AddConstant(control_loop.Constant("kWheelRadius", "%f",
+          drivetrain_low_low.r))
+    dog_loop_writer.AddConstant(control_loop.Constant("kR", "%f",
+          drivetrain_low_low.resistance))
+    dog_loop_writer.AddConstant(control_loop.Constant("kV", "%f",
+          drivetrain_low_low.Kv))
+    dog_loop_writer.AddConstant(control_loop.Constant("kT", "%f",
+          drivetrain_low_low.Kt))
+
+    dog_loop_writer.Write(argv[1], argv[2])
+
+    kf_loop_writer = control_loop.ControlLoopWriter(
+        "KFDrivetrain", [kf_drivetrain_low_low, kf_drivetrain_low_high,
+                         kf_drivetrain_high_low, kf_drivetrain_high_high],
+        namespaces = namespaces)
+    kf_loop_writer.Write(argv[3], argv[4])
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))
diff --git a/y2012/control_loops/python/polydrivetrain.py b/y2012/control_loops/python/polydrivetrain.py
new file mode 100755
index 0000000..9948ff2
--- /dev/null
+++ b/y2012/control_loops/python/polydrivetrain.py
@@ -0,0 +1,512 @@
+#!/usr/bin/python
+
+import numpy
+import sys
+from frc971.control_loops.python import polytope
+from y2012.control_loops.python import drivetrain
+from frc971.control_loops.python import control_loop
+from frc971.control_loops.python import controls
+from matplotlib import pylab
+
+import gflags
+import glog
+
+__author__ = 'Austin Schuh (austin.linux@gmail.com)'
+
+FLAGS = gflags.FLAGS
+
+try:
+  gflags.DEFINE_bool('plot', False, 'If true, plot the loop response.')
+except gflags.DuplicateFlagError:
+  pass
+
+def CoerceGoal(region, K, w, R):
+  """Intersects a line with a region, and finds the closest point to R.
+
+  Finds a point that is closest to R inside the region, and on the line
+  defined by K X = w.  If it is not possible to find a point on the line,
+  finds a point that is inside the region and closest to the line.  This
+  function assumes that
+
+  Args:
+    region: HPolytope, the valid goal region.
+    K: numpy.matrix (2 x 1), the matrix for the equation [K1, K2] [x1; x2] = w
+    w: float, the offset in the equation above.
+    R: numpy.matrix (2 x 1), the point to be closest to.
+
+  Returns:
+    numpy.matrix (2 x 1), the point.
+  """
+  return DoCoerceGoal(region, K, w, R)[0]
+
+def DoCoerceGoal(region, K, w, R):
+  if region.IsInside(R):
+    return (R, True)
+
+  perpendicular_vector = K.T / numpy.linalg.norm(K)
+  parallel_vector = numpy.matrix([[perpendicular_vector[1, 0]],
+                                  [-perpendicular_vector[0, 0]]])
+
+  # We want to impose the constraint K * X = w on the polytope H * X <= k.
+  # We do this by breaking X up into parallel and perpendicular components to
+  # the half plane.  This gives us the following equation.
+  #
+  #  parallel * (parallel.T \dot X) + perpendicular * (perpendicular \dot X)) = X
+  #
+  # Then, substitute this into the polytope.
+  #
+  #  H * (parallel * (parallel.T \dot X) + perpendicular * (perpendicular \dot X)) <= k
+  #
+  # Substitute K * X = w
+  #
+  # H * parallel * (parallel.T \dot X) + H * perpendicular * w <= k
+  #
+  # Move all the knowns to the right side.
+  #
+  # H * parallel * ([parallel1 parallel2] * X) <= k - H * perpendicular * w
+  #
+  # Let t = parallel.T \dot X, the component parallel to the surface.
+  #
+  # H * parallel * t <= k - H * perpendicular * w
+  #
+  # This is a polytope which we can solve, and use to figure out the range of X
+  # that we care about!
+
+  t_poly = polytope.HPolytope(
+      region.H * parallel_vector,
+      region.k - region.H * perpendicular_vector * w)
+
+  vertices = t_poly.Vertices()
+
+  if vertices.shape[0]:
+    # The region exists!
+    # Find the closest vertex
+    min_distance = numpy.infty
+    closest_point = None
+    for vertex in vertices:
+      point = parallel_vector * vertex + perpendicular_vector * w
+      length = numpy.linalg.norm(R - point)
+      if length < min_distance:
+        min_distance = length
+        closest_point = point
+
+    return (closest_point, True)
+  else:
+    # Find the vertex of the space that is closest to the line.
+    region_vertices = region.Vertices()
+    min_distance = numpy.infty
+    closest_point = None
+    for vertex in region_vertices:
+      point = vertex.T
+      length = numpy.abs((perpendicular_vector.T * point)[0, 0])
+      if length < min_distance:
+        min_distance = length
+        closest_point = point
+
+    return (closest_point, False)
+
+
+class VelocityDrivetrainModel(control_loop.ControlLoop):
+  def __init__(self, left_low=True, right_low=True, name="VelocityDrivetrainModel"):
+    super(VelocityDrivetrainModel, self).__init__(name)
+    self._drivetrain = drivetrain.Drivetrain(left_low=left_low,
+                                             right_low=right_low)
+    self.dt = 0.005
+    self.A_continuous = numpy.matrix(
+        [[self._drivetrain.A_continuous[1, 1], self._drivetrain.A_continuous[1, 3]],
+         [self._drivetrain.A_continuous[3, 1], self._drivetrain.A_continuous[3, 3]]])
+
+    self.B_continuous = numpy.matrix(
+        [[self._drivetrain.B_continuous[1, 0], self._drivetrain.B_continuous[1, 1]],
+         [self._drivetrain.B_continuous[3, 0], self._drivetrain.B_continuous[3, 1]]])
+    self.C = numpy.matrix(numpy.eye(2))
+    self.D = numpy.matrix(numpy.zeros((2, 2)))
+
+    self.A, self.B = self.ContinuousToDiscrete(self.A_continuous,
+                                               self.B_continuous, self.dt)
+
+    # FF * X = U (steady state)
+    self.FF = self.B.I * (numpy.eye(2) - self.A)
+
+    self.PlaceControllerPoles([0.8, 0.8])
+    self.PlaceObserverPoles([0.02, 0.02])
+
+    self.G_high = self._drivetrain.G_high
+    self.G_low = self._drivetrain.G_low
+    self.R = self._drivetrain.R
+    self.r = self._drivetrain.r
+    self.Kv = self._drivetrain.Kv
+    self.Kt = self._drivetrain.Kt
+
+    self.U_max = self._drivetrain.U_max
+    self.U_min = self._drivetrain.U_min
+
+
+class VelocityDrivetrain(object):
+  HIGH = 'high'
+  LOW = 'low'
+  SHIFTING_UP = 'up'
+  SHIFTING_DOWN = 'down'
+
+  def __init__(self):
+    self.drivetrain_low_low = VelocityDrivetrainModel(
+        left_low=True, right_low=True, name='VelocityDrivetrainLowLow')
+    self.drivetrain_low_high = VelocityDrivetrainModel(left_low=True, right_low=False, name='VelocityDrivetrainLowHigh')
+    self.drivetrain_high_low = VelocityDrivetrainModel(left_low=False, right_low=True, name = 'VelocityDrivetrainHighLow')
+    self.drivetrain_high_high = VelocityDrivetrainModel(left_low=False, right_low=False, name = 'VelocityDrivetrainHighHigh')
+
+    # X is [lvel, rvel]
+    self.X = numpy.matrix(
+        [[0.0],
+         [0.0]])
+
+    self.U_poly = polytope.HPolytope(
+        numpy.matrix([[1, 0],
+                      [-1, 0],
+                      [0, 1],
+                      [0, -1]]),
+        numpy.matrix([[12],
+                      [12],
+                      [12],
+                      [12]]))
+
+    self.U_max = numpy.matrix(
+        [[12.0],
+         [12.0]])
+    self.U_min = numpy.matrix(
+        [[-12.0000000000],
+         [-12.0000000000]])
+
+    self.dt = 0.005
+
+    self.R = numpy.matrix(
+        [[0.0],
+         [0.0]])
+
+    # ttrust is the comprimise between having full throttle negative inertia,
+    # and having no throttle negative inertia.  A value of 0 is full throttle
+    # inertia.  A value of 1 is no throttle negative inertia.
+    self.ttrust = 1.0
+
+    self.left_gear = VelocityDrivetrain.LOW
+    self.right_gear = VelocityDrivetrain.LOW
+    self.left_shifter_position = 0.0
+    self.right_shifter_position = 0.0
+    self.left_cim = drivetrain.CIM()
+    self.right_cim = drivetrain.CIM()
+
+  def IsInGear(self, gear):
+    return gear is VelocityDrivetrain.HIGH or gear is VelocityDrivetrain.LOW
+
+  def MotorRPM(self, shifter_position, velocity):
+    if shifter_position > 0.5:
+      return (velocity / self.CurrentDrivetrain().G_high /
+              self.CurrentDrivetrain().r)
+    else:
+      return (velocity / self.CurrentDrivetrain().G_low /
+              self.CurrentDrivetrain().r)
+
+  def CurrentDrivetrain(self):
+    if self.left_shifter_position > 0.5:
+      if self.right_shifter_position > 0.5:
+        return self.drivetrain_high_high
+      else:
+        return self.drivetrain_high_low
+    else:
+      if self.right_shifter_position > 0.5:
+        return self.drivetrain_low_high
+      else:
+        return self.drivetrain_low_low
+
+  def SimShifter(self, gear, shifter_position):
+    if gear is VelocityDrivetrain.HIGH or gear is VelocityDrivetrain.SHIFTING_UP:
+      shifter_position = min(shifter_position + 0.5, 1.0)
+    else:
+      shifter_position = max(shifter_position - 0.5, 0.0)
+
+    if shifter_position == 1.0:
+      gear = VelocityDrivetrain.HIGH
+    elif shifter_position == 0.0:
+      gear = VelocityDrivetrain.LOW
+
+    return gear, shifter_position
+
+  def ComputeGear(self, wheel_velocity, should_print=False, current_gear=False, gear_name=None):
+    high_omega = (wheel_velocity / self.CurrentDrivetrain().G_high /
+                  self.CurrentDrivetrain().r)
+    low_omega = (wheel_velocity / self.CurrentDrivetrain().G_low /
+                 self.CurrentDrivetrain().r)
+    #print gear_name, "Motor Energy Difference.", 0.5 * 0.000140032647 * (low_omega * low_omega - high_omega * high_omega), "joules"
+    high_torque = ((12.0 - high_omega / self.CurrentDrivetrain().Kv) *
+                   self.CurrentDrivetrain().Kt / self.CurrentDrivetrain().R)
+    low_torque = ((12.0 - low_omega / self.CurrentDrivetrain().Kv) *
+                  self.CurrentDrivetrain().Kt / self.CurrentDrivetrain().R)
+    high_power = high_torque * high_omega
+    low_power = low_torque * low_omega
+    #if should_print:
+    #  print gear_name, "High omega", high_omega, "Low omega", low_omega
+    #  print gear_name, "High torque", high_torque, "Low torque", low_torque
+    #  print gear_name, "High power", high_power, "Low power", low_power
+
+    # Shift algorithm improvements.
+    # TODO(aschuh):
+    # It takes time to shift.  Shifting down for 1 cycle doesn't make sense
+    # because you will end up slower than without shifting.  Figure out how
+    # to include that info.
+    # If the driver is still in high gear, but isn't asking for the extra power
+    # from low gear, don't shift until he asks for it.
+    goal_gear_is_high = high_power > low_power
+    #goal_gear_is_high = True
+
+    if not self.IsInGear(current_gear):
+      glog.debug('%s Not in gear.', gear_name)
+      return current_gear
+    else:
+      is_high = current_gear is VelocityDrivetrain.HIGH
+      if is_high != goal_gear_is_high:
+        if goal_gear_is_high:
+          glog.debug('%s Shifting up.', gear_name)
+          return VelocityDrivetrain.SHIFTING_UP
+        else:
+          glog.debug('%s Shifting down.', gear_name)
+          return VelocityDrivetrain.SHIFTING_DOWN
+      else:
+        return current_gear
+
+  def FilterVelocity(self, throttle):
+    # Invert the plant to figure out how the velocity filter would have to work
+    # out in order to filter out the forwards negative inertia.
+    # This math assumes that the left and right power and velocity are equal.
+
+    # The throttle filter should filter such that the motor in the highest gear
+    # should be controlling the time constant.
+    # Do this by finding the index of FF that has the lowest value, and computing
+    # the sums using that index.
+    FF_sum = self.CurrentDrivetrain().FF.sum(axis=1)
+    min_FF_sum_index = numpy.argmin(FF_sum)
+    min_FF_sum = FF_sum[min_FF_sum_index, 0]
+    min_K_sum = self.CurrentDrivetrain().K[min_FF_sum_index, :].sum()
+    # Compute the FF sum for high gear.
+    high_min_FF_sum = self.drivetrain_high_high.FF[0, :].sum()
+
+    # U = self.K[0, :].sum() * (R - x_avg) + self.FF[0, :].sum() * R
+    # throttle * 12.0 = (self.K[0, :].sum() + self.FF[0, :].sum()) * R
+    #                   - self.K[0, :].sum() * x_avg
+
+    # R = (throttle * 12.0 + self.K[0, :].sum() * x_avg) /
+    #     (self.K[0, :].sum() + self.FF[0, :].sum())
+
+    # U = (K + FF) * R - K * X
+    # (K + FF) ^-1 * (U + K * X) = R
+
+    # Scale throttle by min_FF_sum / high_min_FF_sum.  This will make low gear
+    # have the same velocity goal as high gear, and so that the robot will hold
+    # the same speed for the same throttle for all gears.
+    adjusted_ff_voltage = numpy.clip(throttle * 12.0 * min_FF_sum / high_min_FF_sum, -12.0, 12.0)
+    return ((adjusted_ff_voltage + self.ttrust * min_K_sum * (self.X[0, 0] + self.X[1, 0]) / 2.0)
+            / (self.ttrust * min_K_sum + min_FF_sum))
+
+  def Update(self, throttle, steering):
+    # Shift into the gear which sends the most power to the floor.
+    # This is the same as sending the most torque down to the floor at the
+    # wheel.
+
+    self.left_gear = self.right_gear = True
+    if True:
+      self.left_gear = self.ComputeGear(self.X[0, 0], should_print=True,
+                                        current_gear=self.left_gear,
+                                        gear_name="left")
+      self.right_gear = self.ComputeGear(self.X[1, 0], should_print=True,
+                                         current_gear=self.right_gear,
+                                         gear_name="right")
+      if self.IsInGear(self.left_gear):
+        self.left_cim.X[0, 0] = self.MotorRPM(self.left_shifter_position, self.X[0, 0])
+
+      if self.IsInGear(self.right_gear):
+        self.right_cim.X[0, 0] = self.MotorRPM(self.right_shifter_position, self.X[0, 0])
+
+    if self.IsInGear(self.left_gear) and self.IsInGear(self.right_gear):
+      # Filter the throttle to provide a nicer response.
+      fvel = self.FilterVelocity(throttle)
+
+      # Constant radius means that angualar_velocity / linear_velocity = constant.
+      # Compute the left and right velocities.
+      steering_velocity = numpy.abs(fvel) * steering
+      left_velocity = fvel - steering_velocity
+      right_velocity = fvel + steering_velocity
+
+      # Write this constraint in the form of K * R = w
+      # angular velocity / linear velocity = constant
+      # (left - right) / (left + right) = constant
+      # left - right = constant * left + constant * right
+
+      # (fvel - steering * numpy.abs(fvel) - fvel - steering * numpy.abs(fvel)) /
+      #  (fvel - steering * numpy.abs(fvel) + fvel + steering * numpy.abs(fvel)) =
+      #       constant
+      # (- 2 * steering * numpy.abs(fvel)) / (2 * fvel) = constant
+      # (-steering * sign(fvel)) = constant
+      # (-steering * sign(fvel)) * (left + right) = left - right
+      # (steering * sign(fvel) + 1) * left + (steering * sign(fvel) - 1) * right = 0
+
+      equality_k = numpy.matrix(
+          [[1 + steering * numpy.sign(fvel), -(1 - steering * numpy.sign(fvel))]])
+      equality_w = 0.0
+
+      self.R[0, 0] = left_velocity
+      self.R[1, 0] = right_velocity
+
+      # Construct a constraint on R by manipulating the constraint on U
+      # Start out with H * U <= k
+      # U = FF * R + K * (R - X)
+      # H * (FF * R + K * R - K * X) <= k
+      # H * (FF + K) * R <= k + H * K * X
+      R_poly = polytope.HPolytope(
+          self.U_poly.H * (self.CurrentDrivetrain().K + self.CurrentDrivetrain().FF),
+          self.U_poly.k + self.U_poly.H * self.CurrentDrivetrain().K * self.X)
+
+      # Limit R back inside the box.
+      self.boxed_R = CoerceGoal(R_poly, equality_k, equality_w, self.R)
+
+      FF_volts = self.CurrentDrivetrain().FF * self.boxed_R
+      self.U_ideal = self.CurrentDrivetrain().K * (self.boxed_R - self.X) + FF_volts
+    else:
+      glog.debug('Not all in gear')
+      if not self.IsInGear(self.left_gear) and not self.IsInGear(self.right_gear):
+        # TODO(austin): Use battery volts here.
+        R_left = self.MotorRPM(self.left_shifter_position, self.X[0, 0])
+        self.U_ideal[0, 0] = numpy.clip(
+            self.left_cim.K * (R_left - self.left_cim.X) + R_left / self.left_cim.Kv,
+            self.left_cim.U_min, self.left_cim.U_max)
+        self.left_cim.Update(self.U_ideal[0, 0])
+
+        R_right = self.MotorRPM(self.right_shifter_position, self.X[1, 0])
+        self.U_ideal[1, 0] = numpy.clip(
+            self.right_cim.K * (R_right - self.right_cim.X) + R_right / self.right_cim.Kv,
+            self.right_cim.U_min, self.right_cim.U_max)
+        self.right_cim.Update(self.U_ideal[1, 0])
+      else:
+        assert False
+
+    self.U = numpy.clip(self.U_ideal, self.U_min, self.U_max)
+
+    # TODO(austin): Model the robot as not accelerating when you shift...
+    # This hack only works when you shift at the same time.
+    if self.IsInGear(self.left_gear) and self.IsInGear(self.right_gear):
+      self.X = self.CurrentDrivetrain().A * self.X + self.CurrentDrivetrain().B * self.U
+
+    self.left_gear, self.left_shifter_position = self.SimShifter(
+        self.left_gear, self.left_shifter_position)
+    self.right_gear, self.right_shifter_position = self.SimShifter(
+        self.right_gear, self.right_shifter_position)
+
+    glog.debug('U is %s %s', str(self.U[0, 0]), str(self.U[1, 0]))
+    glog.debug('Left shifter %s %d Right shifter %s %d',
+               self.left_gear, self.left_shifter_position,
+               self.right_gear, self.right_shifter_position)
+
+
+def main(argv):
+  argv = FLAGS(argv)
+
+  vdrivetrain = VelocityDrivetrain()
+
+  if len(argv) != 5:
+    glog.fatal('Expected .h file name and .cc file name')
+  else:
+    namespaces = ['y2012', 'control_loops', 'drivetrain']
+    dog_loop_writer = control_loop.ControlLoopWriter(
+        "VelocityDrivetrain", [vdrivetrain.drivetrain_low_low,
+                       vdrivetrain.drivetrain_low_high,
+                       vdrivetrain.drivetrain_high_low,
+                       vdrivetrain.drivetrain_high_high],
+                       namespaces=namespaces)
+
+    dog_loop_writer.Write(argv[1], argv[2])
+
+    cim_writer = control_loop.ControlLoopWriter(
+        "CIM", [drivetrain.CIM()])
+
+    cim_writer.Write(argv[3], argv[4])
+    return
+
+  vl_plot = []
+  vr_plot = []
+  ul_plot = []
+  ur_plot = []
+  radius_plot = []
+  t_plot = []
+  left_gear_plot = []
+  right_gear_plot = []
+  vdrivetrain.left_shifter_position = 0.0
+  vdrivetrain.right_shifter_position = 0.0
+  vdrivetrain.left_gear = VelocityDrivetrain.LOW
+  vdrivetrain.right_gear = VelocityDrivetrain.LOW
+
+  glog.debug('K is %s', str(vdrivetrain.CurrentDrivetrain().K))
+
+  if vdrivetrain.left_gear is VelocityDrivetrain.HIGH:
+    glog.debug('Left is high')
+  else:
+    glog.debug('Left is low')
+  if vdrivetrain.right_gear is VelocityDrivetrain.HIGH:
+    glog.debug('Right is high')
+  else:
+    glog.debug('Right is low')
+
+  for t in numpy.arange(0, 1.7, vdrivetrain.dt):
+    if t < 0.5:
+      vdrivetrain.Update(throttle=0.00, steering=1.0)
+    elif t < 1.2:
+      vdrivetrain.Update(throttle=0.5, steering=1.0)
+    else:
+      vdrivetrain.Update(throttle=0.00, steering=1.0)
+    t_plot.append(t)
+    vl_plot.append(vdrivetrain.X[0, 0])
+    vr_plot.append(vdrivetrain.X[1, 0])
+    ul_plot.append(vdrivetrain.U[0, 0])
+    ur_plot.append(vdrivetrain.U[1, 0])
+    left_gear_plot.append((vdrivetrain.left_gear is VelocityDrivetrain.HIGH) * 2.0 - 10.0)
+    right_gear_plot.append((vdrivetrain.right_gear is VelocityDrivetrain.HIGH) * 2.0 - 10.0)
+
+    fwd_velocity = (vdrivetrain.X[1, 0] + vdrivetrain.X[0, 0]) / 2
+    turn_velocity = (vdrivetrain.X[1, 0] - vdrivetrain.X[0, 0])
+    if abs(fwd_velocity) < 0.0000001:
+      radius_plot.append(turn_velocity)
+    else:
+      radius_plot.append(turn_velocity / fwd_velocity)
+
+  cim_velocity_plot = []
+  cim_voltage_plot = []
+  cim_time = []
+  cim = drivetrain.CIM()
+  R = numpy.matrix([[300]])
+  for t in numpy.arange(0, 0.5, cim.dt):
+    U = numpy.clip(cim.K * (R - cim.X) + R / cim.Kv, cim.U_min, cim.U_max)
+    cim.Update(U)
+    cim_velocity_plot.append(cim.X[0, 0])
+    cim_voltage_plot.append(U[0, 0] * 10)
+    cim_time.append(t)
+  pylab.plot(cim_time, cim_velocity_plot, label='cim spinup')
+  pylab.plot(cim_time, cim_voltage_plot, label='cim voltage')
+  pylab.legend()
+  pylab.show()
+
+  # TODO(austin):
+  # Shifting compensation.
+
+  # Tighten the turn.
+  # Closed loop drive.
+
+  pylab.plot(t_plot, vl_plot, label='left velocity')
+  pylab.plot(t_plot, vr_plot, label='right velocity')
+  pylab.plot(t_plot, ul_plot, label='left voltage')
+  pylab.plot(t_plot, ur_plot, label='right voltage')
+  pylab.plot(t_plot, radius_plot, label='radius')
+  pylab.plot(t_plot, left_gear_plot, label='left gear high')
+  pylab.plot(t_plot, right_gear_plot, label='right gear high')
+  pylab.legend()
+  pylab.show()
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))