Auto with Path Planner leading to Oscillating

ChocolateFreckle · October 21, 2024, 10:26pm

Our team has been dabbling in autonomous code and we’ve gotten to the point where we can select our auto in shuffleboard, change the FRC Driver station to autonomous mode, and then enable the auto. Still, instead of taxing like intended, our robot’s motor started oscillating like crazy. Any advice for troubleshooting?

Rumbbly-Swerve-/src/main/java/frc/robot at main · frc4087/Rumbbly-Swerve-

ajs2 · October 21, 2024, 10:40pm

That sounds like badly-tuned PID(F) control. Take a look at Introduction to PID — FIRST Robotics Competition documentation and probably more resources I can’t remember but they’re out there somewhere!

kn4 · October 21, 2024, 10:44pm

Specifically, the PID values you might want to look at are in your HolonomicPathFollowerConfig class in your PathPlanner configuration:

github.com

frc4087/Rumbbly-Swerve-/blob/main/src/main/java/frc/robot/subsystems/CommandSwerveDrivetrain.java#L104


      
          double driveBaseRadius = 0;
          for (var moduleLocation : m_moduleLocations) {
              driveBaseRadius = Math.max(driveBaseRadius, moduleLocation.getNorm());
          }
          
          AutoBuilder.configureHolonomic(
              ()->this.getState().Pose, // Supplier of current robot pose
              this::seedFieldRelative,  // Consumer for seeding pose against auto
              this::getCurrentRobotChassisSpeeds,
              (speeds)->this.setControl(autoRequest.withSpeeds(speeds)), // Consumer of ChassisSpeeds to drive the robot
              new HolonomicPathFollowerConfig(new PIDConstants(100, 0, 0.2),
                                              new PIDConstants(100, 0, 0.2),
                                              TunerConstants.kSpeedAt12VoltsMps,
                                              driveBaseRadius,
                                              new ReplanningConfig()),
              () -> {
                      // Boolean supplier that controls when the path will be mirrored for the red alliance
                      // This will flip the path being followed to the red side of the field during auto only.
                      // THE ORIGIN WILL REMAIN ON THE BLUE SIDE
          
                      var alliance = DriverStation.getAlliance();

A kP value of 100 would probably lead to issues. For comparison, the PathPlanner documentation examples have a kP of 5 and the CTRE Swerve PathPlanner example uses 10.

Owen4026 · October 21, 2024, 10:45pm

The P constant in your auto configs looks really high (100). I would lower that until you stop seeing the oscillation.