PIDController not manipulating jaguars

[gpetilli]

Originally Posted by ekapalka

Wow... that sounds amazing. Was this just using the simple WPILib PID classes or was it something else entirely? We've been looking into using closed loop control on our robot this year (we haven't ever in the past) and were thinking a "stay in place" button would be a cool [possibly unnecessary] thing to do for learning purposes (our robot is relatively simple).

Yesterday we increased the D term and the robot resisted movement more vehemently and only returned about 1in when kicked 1 foot - which is closer to our desired behavior.

As a point of clarification, we are not using encoders on the gearboxes - we have small, undriven follower omni-wheels with encoders to feedback velocity to the PID on the cRIO. This means that if the driven wheels lose traction while being pushed (or we spin wheels during hard acceleration) the PID still detects and tries to correct the movement. The closed loop PID "set point" is the driver commanded velocity. We do not have a "stay in place" special case, the PID is trying to drive to commanded zero velocity.

The WPI PID could potentially do this, but we implemented custom PID because we are using a holonomic drive (modified Killough) where the four driven omni-wheels are at a 30deg angle and we want the driver commands to be Cartesian. We measure the three degrees of freedom (X, Y, Rotation) and derive the four motor voltages.