Tune turret for real

Add in friction compensation and tune the controller a bit.  Fix a poor
velocity estimate.

Change-Id: I153b659bf92d5f34f0e8f59fda34e3c693e41d6a
diff --git a/y2020/control_loops/superstructure/superstructure.h b/y2020/control_loops/superstructure/superstructure.h
index d8ce917..d5f4235 100644
--- a/y2020/control_loops/superstructure/superstructure.h
+++ b/y2020/control_loops/superstructure/superstructure.h
@@ -21,6 +21,11 @@
   explicit Superstructure(::aos::EventLoop *event_loop,
                           const ::std::string &name = "/superstructure");
 
+  // Terms to control the velocity gain for the friction compensation, and the
+  // voltage cap.
+  static constexpr double kTurretFrictionGain = 10.0;
+  static constexpr double kTurretFrictionVoltageLimit = 1.5;
+
   using PotAndAbsoluteEncoderSubsystem =
       ::frc971::control_loops::StaticZeroingSingleDOFProfiledSubsystem<
           ::frc971::zeroing::PotAndAbsoluteEncoderZeroingEstimator,