pid_controller

Classes

PIDController	PID Controller that contains a lateral and longitudinal controller
PIDLateralController	Lateral (steering) controller which minimizes error using a PID
PIDLongitudinalController	Longitudinal (throttle, braking) controller which minimizes error using a PID

class PIDController(system: wa.WASystem, vehicle: wa.WAVehicle, vehicle_inputs: wa.WAVehicleInputs, path: wa.WAPath, lat_controller: PIDLateralController = None, long_controller: PIDLongitudinalController = None)

Bases: wa_simulator.WAController

PID Controller that contains a lateral and longitudinal controller

Uses the lateral controller for steering and longitudinal controller throttle/braking

Parameters

• system (WASystem) – The system used to manage the simulation

• vehicle (WAVehicle) – The vehicle to grab the state from

• vehicle_inputs (WAVehicleInputs) – The vehicle inputs

• path (WAPath) – The path to follow

• lat_controller (PIDLateralController, optional) – Lateral controller for steering. Defaults to None. Will create one if not passed.

• long_controller (PIDLongitudinalController, optional) – Longitudinal controller for throttle/braking. Defaults to None. Will create one if not passed.

set_delta(self, steering_delta: float, throttle_delta: float, braking_delta: float)

Set the delta values

In this controller, delta values are the maximum change in steering/throttle/braking that can occur in a single update. For example, if the vehicle is not moving and the underyling longitudinal controller wanted to have the vehicle go pedal-to-the-metal, instead of going from 0% throttle to 100%, it will go from 0% to (1. / throttle_delta / 100)%. This means if the throttle_delta was 0.01, then the throttle would be placed at 10%. Same principle is true for braking and steering values during the update.

Parameters

• steering_delta (float) – max steering delta

• throttle_delta (float) – max throttle delta

• braking_delta (float) – max braking delta

set_gains(self, steering_gain: float, throttle_gain: float, braking_gain: float)

Set the gain values

The gains are multiplied to each “derivative” calculated during each time step. This controller works by using the target input value provided by the underlying lateral and longitudinal controllers and “stepping” towards that value in increments. See set_delta() to understand the delta values. On each step, the difference between the target and current values are multiplied by the gain. This is because the difference may be very small or very large, so a high/low gain can offset this and provide better results.

Parameters

• steering_gain (float) – steering gain

• throttle_gain (float) – throttle gain

• braking_gain (float) – braking gain

get_long_controller(self) → PIDLongitudinalController

Get the underyling longitudinal controller

Returns

PIDLongitudinalController – The underyling longitudinal (speed/throttle) controller

synchronize(self, time: float)

Synchronize the lateral and longitudinal controllers at the specified time

Parameters

time (float) – the time at which the controller should synchronize all modules

advance(self, step: float)

Advance the state of the lateral and longitudinal controllers

Parameters

step (float) – the time step at which the controller should be advanced

get_target_pos(self) → wa.WAVector

Get the position of the target point of the lateral controller

Returns

WAVector – The position of the target point

get_sentinel_pos(self) → wa.WAVector

Get the position of the sentinel point of the lateral controller

Returns

WAVector – The position of the sentinel point

class PIDLateralController(system: wa.WASystem, vehicle: wa.WAVehicle, vehicle_inputs: wa.WAVehicleInputs, path: wa.WAPath)

Bases: wa_simulator.WAController

Lateral (steering) controller which minimizes error using a PID

Parameters

• system (WASystem) – The system used to manage the simulation

• vehicle (WAVehicle) – the vehicle who has dynamics

• vehicle_inputs (WAVehicleInputs) – The vehicle inputs

• path (WAPath) – the path the vehicle is attempting to follow

set_gains(self, Kp: float, Ki: float, Kd: float)

Set the gains

Parameters

• Kp (float) – new proportional gain

• Ki (float) – new integral gain

• Kd (float) – new derivative gain

set_lookahead_distance(self, dist: float)

Set the lookahead distance

To track the path, this controller aims for a lookahead point at the specified distance directly infront of the vehicle. That way, the tracking will be much smoother.

Parameters

dist (float) – new lookahead distance

synchronize(self, time: float)

Synchronize the controller at the passed time

Doesn’t actually do anything.

Parameters

time (float) – the time to synchronize the controller to

advance(self, step: float)

Advance the state of the controller by step

Parameters

step (float) – step size to update the controller by

class PIDLongitudinalController(system: wa.WASystem, vehicle: wa.WAVehicle, vehicle_inputs: wa.WAVehicleInputs)

Bases: wa_simulator.WAController

Longitudinal (throttle, braking) controller which minimizes error using a PID

Parameters

• system (WASystem) – The system used to manage the simulation

• vehicle_inputs (WAVehicleInputs) – The vehicle inputs

• vehicle (WAVehicle) – the vehicle who has dynamics

set_gains(self, Kp: float, Ki: float, Kd: float)

Set the gains

Parameters

• Kp (float) – new proportional gain

• Ki (float) – new integral gain

• Kd (float) – new derivative gain

set_target_speed(self, speed: float)

Set the target speed for the controller

Parameters

speed (float) – the new target speed

synchronize(self, time: float)

Synchronize the controller at the passed time

Doesn’t actually do anything.

Parameters

time (float) – the time to synchronize the controller to

advance(self, step)

Advance the state of the controller by step

Parameters

step (float) – step size to update the controller by