Make a mutual drivetrain between robots.

Change-Id: I23cc9634d9af5d0482dc5a5501dccc064b7b53d3
diff --git a/frc971/control_loops/drivetrain/drivetrain.cc b/frc971/control_loops/drivetrain/drivetrain.cc
new file mode 100644
index 0000000..ca395cb
--- /dev/null
+++ b/frc971/control_loops/drivetrain/drivetrain.cc
@@ -0,0 +1,146 @@
+#include "frc971/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 "frc971/control_loops/drivetrain/drivetrain.q.h"
+#include "frc971/control_loops/drivetrain/polydrivetrain.h"
+#include "frc971/control_loops/drivetrain/ssdrivetrain.h"
+#include "frc971/control_loops/drivetrain/drivetrain_config.h"
+#include "frc971/queues/gyro.q.h"
+#include "frc971/shifter_hall_effect.h"
+
+using frc971::sensors::gyro_reading;
+
+namespace frc971 {
+namespace control_loops {
+namespace drivetrain {
+
+DrivetrainLoop::DrivetrainLoop(
+    const DrivetrainConfig &dt_config,
+    ::frc971::control_loops::DrivetrainQueue *my_drivetrain)
+    : aos::controls::ControlLoop<::frc971::control_loops::DrivetrainQueue>(
+          my_drivetrain),
+      dt_config_(dt_config),
+      kf_(dt_config_.make_kf_drivetrain_loop()) {
+  ::aos::controls::HPolytope<0>::Init();
+}
+
+void DrivetrainLoop::RunIteration(
+    const ::frc971::control_loops::DrivetrainQueue::Goal *goal,
+    const ::frc971::control_loops::DrivetrainQueue::Position *position,
+    ::frc971::control_loops::DrivetrainQueue::Output *output,
+    ::frc971::control_loops::DrivetrainQueue::Status *status) {
+  bool bad_pos = false;
+  if (position == nullptr) {
+    LOG_INTERVAL(no_position_);
+    bad_pos = true;
+  }
+  no_position_.Print();
+
+  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_ += dt_config_.dt *
+                              (kf_.X_hat(3, 0) - kf_.X_hat(1, 0)) /
+                              (dt_config_.robot_radius * 2.0);
+  }
+
+  bool control_loop_driving = false;
+  if (goal) {
+    double wheel = goal->steering;
+    double throttle = goal->throttle;
+    bool quickturn = goal->quickturn;
+    bool highgear = goal->highgear;
+
+    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);
+    dt_openloop_.SetGoal(wheel, throttle, quickturn, highgear);
+  }
+
+  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;
+
+  // 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 frc971