Profiled PID Control

Profiled PID control, similar to regular PID control, is a control loop feedback mechanism that incorporates acceleraton and velocity limits with a trapezoidal constraint.

Note

for a review on PID control, see PID

A profiled PID is used over normal PID when the system being controlled has physical constraints on acceleration and velocity. For example, a robot arm may have a maximum acceleration and velocity that it can achieve. A profiled PID will take these constraints into account when generating the control signal.

The profiled PID is implemented as a subclass of the regular PID class. The profiled PID class overrides the PIDController.calculate() method to add the acceleration and velocity constraints.

The profiled PID class also adds two new methods, PIDController.setAccelerationLimits() and PIDController.setVelocityLimits(), which set the acceleration and velocity limits, respectively.

You can create a profiled PID controller using the ProfiledPIDController class.

from wpilib.controller import ProfiledPIDController
from wpilib.trajectory import TrapezoidProfile

constraints = TrapezoidProfile.Constraints(max_velocity=1.7, max_acceleration=2)

controller = ProfiledPIDController(1, 0, 0, constraints=constraints)

# Set the goal state

controller.setGoal(TrapezoidProfile.State(3, 0))

# Calculate the feedforward and feedback terms

output = controller.calculate(current_pose, current_velocity)

# Use the output to control the mechanism

mechanism.setVoltage(output)

Note

The ProfiledPIDController class is a subclass of the PIDController class. This means that you can use a profiled PID controller anywhere you would use a regular PID controller. For example, you can use a profiled PID controller in the wpilib.controller.RamseteController class.

from wpilib.controller import RamseteController
from wpilib.trajectory import Trajectory

trajectory = Trajectory()

controller = RamseteController(2, 0.7)

# Set the goal state

controller.setGoal(trajectory.sample(0))

# Calculate the feedforward and feedback terms

output = controller.calculate(current_pose, current_velocity)

# Use the output to control the mechanism

mechanism.setVoltage(output)