Modify shooter control loop to take velocity.

- NOTE: Things compile and run, but the output never actually stabilizes.
Before this can be used, new motor_plant constants for the shooter MUST
be determined.
diff --git a/bot3/control_loops/shooter/shooter.cc b/bot3/control_loops/shooter/shooter.cc
index fbfeafb..07ce397 100644
--- a/bot3/control_loops/shooter/shooter.cc
+++ b/bot3/control_loops/shooter/shooter.cc
@@ -10,12 +10,9 @@
 
 ShooterMotor::ShooterMotor(control_loops::ShooterLoop *my_shooter)
     : aos::control_loops::ControlLoop<control_loops::ShooterLoop>(my_shooter),
-    loop_(new StateFeedbackLoop<2, 1, 1>(MakeShooterLoop())),
-    history_position_(0),
-    position_goal_(0.0),
-    last_position_(0.0),
+    loop_(new StateFeedbackLoop<1, 1, 1>(MakeShooterLoop())),
     last_velocity_goal_(0) {
-  memset(history_, 0, sizeof(history_));
+    loop_->Reset();
 }
 
 /*static*/ const double ShooterMotor::dt = 0.01;
@@ -26,10 +23,12 @@
     ::aos::control_loops::Output *output,
     control_loops::ShooterLoop::Status *status) {
   double velocity_goal = goal->velocity;
-  const double current_position =
+  // Our position here is actually a velocity.
+  average_velocity_ =
       (position == NULL ? loop_->X_hat(0, 0) : position->position);
   double output_voltage = 0.0;
 
+// TODO (danielp): This must be modified for our index.
 /*  if (index_loop.status.FetchLatest() || index_loop.status.get()) {
     if (index_loop.status->is_shooting) {
       if (velocity_goal != last_velocity_goal_ &&
@@ -42,57 +41,21 @@
   }*/
   last_velocity_goal_ = velocity_goal;
 
-  // Track the current position if the velocity goal is small.
-  if (velocity_goal <= 1.0) {
-    position_goal_ = current_position;
-  }
-
-  loop_->Y << current_position;
-
-  // Add the position to the history.
-  history_[history_position_] = current_position;
-  history_position_ = (history_position_ + 1) % kHistoryLength;
-
-  // Prevents integral windup by limiting the position error such that the
-  // error can't produce much more than full power.
-  const double kVelocityWeightScalar = 0.35;
-  const double max_reference =
-      (loop_->U_max(0, 0) - kVelocityWeightScalar *
-       (velocity_goal - loop_->X_hat(1, 0)) * loop_->K(0, 1))
-      / loop_->K(0, 0) + loop_->X_hat(0, 0);
-  const double min_reference =
-      (loop_->U_min(0, 0) - kVelocityWeightScalar *
-       (velocity_goal - loop_->X_hat(1, 0)) * loop_->K(0, 1))
-      / loop_->K(0, 0) + loop_->X_hat(0, 0);
-
-  position_goal_ = ::std::max(::std::min(position_goal_, max_reference),
-                              min_reference);
-  loop_->R << position_goal_, velocity_goal;
-  position_goal_ += velocity_goal * dt;
+  loop_->Y << average_velocity_;
+  loop_->R << velocity_goal;
 
   loop_->Update(position, output == NULL);
 
   // Kill power at low velocity goals.
   if (velocity_goal < 1.0) {
-    loop_->U[0] = 0.0;
+    loop_->U(0) = 0.0;
   } else {
-    output_voltage = loop_->U[0];
+    output_voltage = loop_->U(0);
   }
 
   LOG(DEBUG,
-      "PWM: %f, raw_pos: %f rotations: %f "
-      "junk velocity: %f, xhat[0]: %f xhat[1]: %f, R[0]: %f R[1]: %f\n",
-      output_voltage, current_position,
-      current_position / (2 * M_PI),
-      (current_position - last_position_) / dt,
-      loop_->X_hat[0], loop_->X_hat[1], loop_->R[0], loop_->R[1]);
-
-  // Calculates the velocity over the last kHistoryLength * .01 seconds
-  // by taking the difference between the current and next history positions.
-  int old_history_position = ((history_position_ == 0) ?
-        kHistoryLength : history_position_) - 1;
-  average_velocity_ = (history_[old_history_position] -
-      history_[history_position_]) * 100.0 / (double)(kHistoryLength - 1);
+      "PWM: %f, raw_velocity: %f,  xhat[0]: %f, R[0]: %f\n",
+      output_voltage, average_velocity_, loop_->X_hat[0], loop_->R[0]);
 
   status->average_velocity = average_velocity_;
 
@@ -107,8 +70,6 @@
   }
   LOG(DEBUG, "avg = %f goal = %f\n", average_velocity_, velocity_goal);
   
-  last_position_ = current_position;
-
   if (output) {
     output->voltage = output_voltage;
   }