Make a mutual drivetrain between robots.

Change-Id: I23cc9634d9af5d0482dc5a5501dccc064b7b53d3
diff --git a/frc971/control_loops/drivetrain/polydrivetrain.h b/frc971/control_loops/drivetrain/polydrivetrain.h
new file mode 100644
index 0000000..1ba7eee
--- /dev/null
+++ b/frc971/control_loops/drivetrain/polydrivetrain.h
@@ -0,0 +1,75 @@
+#ifndef FRC971_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_
+#define FRC971_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_
+
+#include "aos/common/controls/polytope.h"
+
+#include "frc971/control_loops/drivetrain/drivetrain.q.h"
+#include "frc971/control_loops/state_feedback_loop.h"
+#include "frc971/control_loops/drivetrain/drivetrain_config.h"
+
+namespace frc971 {
+namespace control_loops {
+namespace drivetrain {
+
+class PolyDrivetrain {
+ public:
+  enum Gear { HIGH, LOW, SHIFTING_UP, SHIFTING_DOWN };
+
+  PolyDrivetrain(const DrivetrainConfig &dt_config);
+
+  int controller_index() const { return loop_->controller_index(); }
+
+  bool IsInGear(Gear gear) { return gear == LOW || gear == HIGH; }
+
+  // Computes the speed of the motor given the hall effect position and the
+  // speed of the robot.
+  double MotorSpeed(const constants::ShifterHallEffect &hall_effect,
+                    double shifter_position, double velocity);
+
+  // Computes the states of the shifters for the left and right drivetrain sides
+  // given a requested state.
+  void UpdateGears(Gear requested_gear);
+
+  // Computes the next state of a shifter given the current state and the
+  // requested state.
+  Gear UpdateSingleGear(Gear requested_gear, Gear current_gear);
+
+  void SetGoal(double wheel, double throttle, bool quickturn, bool highgear);
+
+  void SetPosition(
+      const ::frc971::control_loops::DrivetrainQueue::Position *position);
+
+  double FilterVelocity(double throttle);
+
+  double MaxVelocity();
+
+  void Update();
+
+  void SendMotors(::frc971::control_loops::DrivetrainQueue::Output *output);
+
+ private:
+  StateFeedbackLoop<7, 2, 3> kf_;
+
+  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_;
+  ::frc971::control_loops::DrivetrainQueue::Position last_position_;
+  ::frc971::control_loops::DrivetrainQueue::Position position_;
+  int counter_;
+  DrivetrainConfig dt_config_;
+};
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace frc971
+
+#endif  // FRC971_CONTROL_LOOPS_DRIVETRAIN_POLYDRIVETRAIN_H_