Copy back a lot of the 2014 code.

Change-Id: I552292d8bd7bce4409e02d254bef06a9cc009568
diff --git a/y2014/control_loops/drivetrain/drivetrain.h b/y2014/control_loops/drivetrain/drivetrain.h
new file mode 100644
index 0000000..87e6362
--- /dev/null
+++ b/y2014/control_loops/drivetrain/drivetrain.h
@@ -0,0 +1,43 @@
+#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 "y2014/control_loops/drivetrain/drivetrain.q.h"
+#include "aos/common/util/log_interval.h"
+
+namespace frc971 {
+namespace control_loops {
+
+class DrivetrainLoop
+    : public aos::controls::ControlLoop<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(control_loops::DrivetrainQueue *my_drivetrain =
+                              &control_loops::drivetrain_queue)
+      : aos::controls::ControlLoop<control_loops::DrivetrainQueue>(
+            my_drivetrain) {
+    ::aos::controls::HPolytope<0>::Init();
+  }
+
+ protected:
+  // Executes one cycle of the control loop.
+  virtual void RunIteration(
+      const control_loops::DrivetrainQueue::Goal *goal,
+      const control_loops::DrivetrainQueue::Position *position,
+      control_loops::DrivetrainQueue::Output *output,
+      control_loops::DrivetrainQueue::Status *status);
+
+  typedef ::aos::util::SimpleLogInterval SimpleLogInterval;
+  SimpleLogInterval no_position_ = SimpleLogInterval(
+      ::aos::time::Time::InSeconds(0.25), WARNING, "no position");
+};
+
+}  // namespace control_loops
+}  // namespace frc971
+
+#endif  // Y2014_CONTROL_LOOPS_DRIVETRAIN_H_