MotionView User's Guide

Feedback Traction Controller - PID Controller

Feedback Traction Controller - PID Controller

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Feedback Traction Controller - PID Controller

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A Proportional-Integral-Derivative (PID) controller is a feedback controller that computes a vehicle input using the error, the integral of error, and the rate of change of error between a desired vehicle response and the actual vehicle response.  To use a PID control you enter proportional (KP), integral (KI), and derivative (KD) gains, the type of desired response (for example, longitudinal speed or acceleration), and reference the desired response (for example, a table of speed vs time).  The Altair Driver then applies the Proportional-Integral-Derivative (PID) control law to calculate the throttle and brake signals.

Algorithm:

Parameters

Demand Signal

U

Feedback or response signal

X

Error

e

Proportional gain

Proportional gain

Derivative gain

Derivative gain

Integral gain

Integral Gain

Integral control flag

Integral Control Flag

Integral band

Integral band

Driver throttle output

O throttle

Driver brake output

O brake

Drive Ratio

altair_driver_pid_control_drive_ratio_equation_mv

Gear Ratio

altair_driver_pid_control_gear_ratio_equation_mv

altair_driver_pid_control_y_equation_mv

altair_driver_pid_control_e_equation_mv

altair_driver_pid_control_x_equation_mv

altair_driver_pid_control_0_throttle_equation_mv

altair_driver_pid_control_0_brake_equation_mv

Types:

•VELOCITY CONTROL – Demand signal is a velocity profile with time or distance traveled as independent variable.
•ACCELERATION CONTROL - Demand signal is an acceleration profile with time or distance traveled as independent variable.
•Demand signal can be constant, expression driver, user defined curve, or MotionView Signal (similar to Open Loop controller).

[LONG_PID_CONTROLLER]

TAG = 'PID'

TYPE = 'FOLLOW_VELOCITY'

DEMAND_SIGNAL = 'DEMAND_SPEED'

I_ACTIVE_BAND = 2

KP                                = 100

KD                                = 20

KI                                = 10

INITIAL_ERROR                = -5

[FEEDFORWARD LONGITUDINAL CONTROLLER]

TAG

Attr - string

REQUIRED

<PID >

TYPE

Attr – string

OPTIONAL

•By default assumes FOLLOW_VELOCITY.
•Options:
oFOLLOW_VELOCITY
oFOLLOW_ACCELERATION

DEMAND_SIGNAL

Attr - string

REQUIRED

Block name that contains the demand signal.   See the Demand Signal Block topic to learn more about all of the available methods.

I_ACTIVE_BAND

Attr - real

OPTIONAL

•Band in which integral control is activate.

If absent:

•Integral gain is always active.  May lead to overcompensation.

KP

Attr-real

OPTIONAL

•Proportional gain

If absent:

•KP  = 0

KD

Attr-real

OPTIONAL

•Differential gain

If absent:

•KD  = 0

KI

Attr-real

OPTIONAL

•Integral gain

If absent:

•KI = 0

[FEEDFORWARD LONGITUDINAL CONTROLLER]

INITIAL_ERROR

Attr-real

OPTIONAL

•Integral error

If absent:

•INITIAL_ERROR = 0