Module: hingedRigidBodyPIDMotor

Executive Summary

This module implements a simple Proportional-Integral-Derivative (PID) control law to provide the commanded torque to a Module: spinningBodyOneDOFStateEffector.

Message Connection Descriptions

The following table lists all the module input and output messages. The module msg connection is set by the user from python. The msg type contains a link to the message structure definition, while the description provides information on what this message is used for.

Module I/O Messages

Msg Variable Name	Msg Type	Description
motorTorqueOutMsg	ArrayMotorTorqueMsgPayload	Output Spinning Body Reference Message.
hingedRigidBodyInMsg	HingedRigidBodyMsgPayload	Input Spinning Body Message Message.
hingedRigidBodyRefInMsg	HingedRigidBodyMsgPayload	Input Spinning Body Reference Message Message.

Module Assumptions and Limitations

This module is very simple and does not make any assumptions. The only limitations are those inherent to a PID type of control law, here implemented. The type of response (underdamped, overdamped, or critically damped) depends on the choice of gains provided as inputs to the module.

Detailed Module Description

For this module to operate, the user needs to provide control gains K, P and I. Let’s define \(\theta_R\) and \(\dot{\theta}_R\) the reference angle and angle rate contained in the hingedRigidBodyRefInMsg, and \(\theta\) and \(\dot{\theta}\) the current solar array angle and angle rate contained in the hingedRigidBodyInMsg, which is provided as an output of the Module: spinningBodyOneDOFStateEffector. The control torque is obtained as follows:

\[T = K (\theta_R - \theta) + P (\dot{\theta}_R - \dot{\theta}) + I \int_0^t (\theta_R - \theta) \text{d}\tau.\]

User Guide

The required module configuration is:

motorConfig = hingedRigidBodyPIDMotorConfig.hingedRigidBodyPIDMotorConfig()
motorWrap = unitTestSim.setModelDataWrap(motorConfig)
motorWrap.ModelTag = "solarArrayPDController"
motorConfig.K = K
motorConfig.P = P
motorConfig.P = I
unitTestSim.AddModelToTask(unitTaskName, motorWrap, motorConfig)

The module is configurable with the following parameters:

Module Parameters

Parameter	Description
K	proportional gain; defaults to 0 if not provided
P	derivative gain; defaults to 0 if not provided
I	integral gain; defaults to 0 if not provided

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Functions

void SelfInit_hingedRigidBodyPIDMotor(hingedRigidBodyPIDMotorConfig *configData, int64_t moduleID)

This method initializes the output messages for this module.

Parameters

• configData – The configuration data associated with this module

• moduleID – The module identifier

Returns

void

void Reset_hingedRigidBodyPIDMotor(hingedRigidBodyPIDMotorConfig *configData, uint64_t callTime, int64_t moduleID)

This method performs a complete reset of the module. Local module variables that retain time varying states between function calls are reset to their default values.

Parameters

• configData – The configuration data associated with the module

• callTime – [ns] time the method is called

• moduleID – The module identifier

Returns

void

void Update_hingedRigidBodyPIDMotor(hingedRigidBodyPIDMotorConfig *configData, uint64_t callTime, int64_t moduleID)

This method computes the control torque to the solar array drive based on a PD control law

Parameters

• configData – The configuration data associated with the module

• callTime – The clock time at which the function was called (nanoseconds)

• moduleID – The module identifier

Returns

void

struct hingedRigidBodyPIDMotorConfig

#include <hingedRigidBodyPIDMotor.h>

Top level structure for the sub-module routines.

Public Members

double K

proportional gain

declare these user-defined input parameters

double P

derivative gain

double I

integral gain

uint64_t priorTime

prior function call time for trapezoid integration

declare these variables for internal computations

double priorThetaError

theta error at prior function call

double intError

integral error

HingedRigidBodyMsg_C hingedRigidBodyInMsg

input spinning body message

HingedRigidBodyMsg_C hingedRigidBodyRefInMsg

output msg containing spinning body target angle and angle rate

ArrayMotorTorqueMsg_C motorTorqueOutMsg

output msg containing the motor torque to the array drive

BSKLogger *bskLogger

BSK Logging.