Make a mutual drivetrain between robots.

Change-Id: I23cc9634d9af5d0482dc5a5501dccc064b7b53d3
diff --git a/frc971/control_loops/drivetrain/drivetrain.h b/frc971/control_loops/drivetrain/drivetrain.h
new file mode 100644
index 0000000..22a6c32
--- /dev/null
+++ b/frc971/control_loops/drivetrain/drivetrain.h
@@ -0,0 +1,58 @@
+#ifndef FRC971_CONTROL_LOOPS_DRIVETRAIN_H_
+#define FRC971_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 "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 "aos/common/util/log_interval.h"
+
+namespace frc971 {
+namespace control_loops {
+namespace drivetrain {
+
+class DrivetrainLoop : public aos::controls::ControlLoop<
+                           ::frc971::control_loops::DrivetrainQueue> {
+ public:
+  // Constructs a control loop which can take a Drivetrain or defaults to the
+  // drivetrain at frc971::control_loops::drivetrain
+  explicit DrivetrainLoop(const DrivetrainConfig &dt_config,
+      ::frc971::control_loops::DrivetrainQueue *my_drivetrain =
+          &::frc971::control_loops::drivetrain_queue);
+
+ protected:
+  // Executes one cycle of the control loop.
+  virtual void 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);
+
+  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;
+
+  const DrivetrainConfig dt_config_;
+
+  PolyDrivetrain dt_openloop_{dt_config_};
+  DrivetrainMotorsSS dt_closedloop_{dt_config_};
+  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 frc971
+
+#endif  // FRC971_CONTROL_LOOPS_DRIVETRAIN_H_