Robot PID Control Applications (Android Studio)
Multi-Axis PID Control
Many FTC mechanisms require controlling more than one axis at a time, such as X/Y drive or multi-joint arms. Each axis can have its own PID controller, and sometimes you need to coordinate them for smooth, accurate movement.
Example: Dual-Axis PID for Drivetrain
double xError = targetX - getCurrentX();
double yError = targetY - getCurrentY();
double xOutput = xPID.calculate(xError);
double yOutput = yPID.calculate(yError);
setDrivePower(xOutput, yOutput);Drivetrain PID Control
PID control is commonly used for driving straight, turning to a specific angle, or following a path. By using encoders and IMUs, you can create closed-loop control for your drivetrain.
Example: PID Turn to Angle (IMU)
double error = targetAngle - imu.getHeading();
double output = turnPID.calculate(error);
leftMotor.setPower(output);
rightMotor.setPower(-output);Arm and Mechanism PID Control
PID is also used for arms, lifts, and other mechanisms. For example, you can use a PID controller to move an arm to a specific position using an encoder.
Example: Arm PID Control
double error = targetPosition - armMotor.getCurrentPosition();
double output = armPID.calculate(error);
armMotor.setPower(Range.clip(output, -1, 1));Tuning Strategies for Complex Systems
- Tune one axis or mechanism at a time.
- Start with kP, then add kD and kI as needed.
- Watch for interactions between axes (e.g., X and Y).
- Use telemetry to monitor errors and outputs.
Integrating PID with the FTC SDK
The FTC SDK provides built-in PIDFCoefficients classes so users can tune their motors' PIDF coefficients. You can use these classes for more advanced control and to simplify your code. See the official documentation for details: PIDFCoefficients Javadoc
Safety and Best Practices
- Always set limits on motor power and positions to prevent hardware damage.
- Use failsafes and watchdog timers to stop the robot if something goes wrong.
- Test new PID code at low power and with the robot off the ground.