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_