PositionControl Class Reference
[Miscellaneous Library Utilities]

#include <PositionControl.hh>

Inherits MotorControl.

List of all members.

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Detailed Description

Module to implement basic PD control of DC motors.

The PositionControl module implements PD motion control for a single axis. It uses the EncoderReader module instance with the same index and outputs commands through the DCMotorHW hardware component's corresponding axis.

Depending on the configuration of the underlying DC motors, it performs computations for either voltage or torque mode operations. For the latter, the motor command is simply computed with a proportional derivative feedback term based on current shaft position and velocity measurements. In contrast, in the former case, the module can be configured to perform back-EMF compensation to obtain approximate torque control.

Public Types
enum	CompensationType { NONE, BACKEMF }
Public Member Functions
	PositionControl (int index)
void	init (void)
void	uninit (void)
void	activate (void)
void	deactivate (void)
void	update (void)
float	getTorqueOffset (void)
void	setTorqueOffset (float torque)
void	setErrorOffset (float offset)
float	getErrorOffset (void)
void	setCompensationType (CompensationType type)
CompensationType	getCompensationType (void)
float	getSpeedErr (void)
float	getPositionErr (void)
void	freeze (void)

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Member Enumeration Documentation

enum PositionControl::CompensationType

This enum type defines possible types of command compensation if the underlying hardware operates in voltage mode.

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Constructor & Destructor Documentation

PositionControl::PositionControl (  int  index  )

This constructor selects the index of the module, establishing correspondances with the appropriate EncoderReader and the axis number of the underlying hardware

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Member Function Documentation

void PositionControl::freeze (  void   )

This method sets the motor target to the current motor pos.

CompensationType PositionControl::getCompensationType (  void   )  [inline]

This method returns the current type for the command compensation

float PositionControl::getErrorOffset (  void   )  [inline]

This method returns the current error offset setting

float PositionControl::getPositionErr (  void   )  [inline]

This method returns the current error in shaft position

float PositionControl::getSpeedErr (  void   )  [inline]

This method returns the current error in shaft speed

float PositionControl::getTorqueOffset (  void   )  [inline]

This method returns the current feedforward torque command

void PositionControl::setCompensationType (  CompensationType  type  )  [inline]

This method can be used to choose the type of command compensation term in the feedback loop.

void PositionControl::setErrorOffset (  float  offset  )  [inline]

This metod sets the error offset for angular difference computations. The need for such an offset comes from the periodicity of angular values and the ambiguity of what "error" means for angle differences. This error offset determines the range of the position error in the PD calculations. The range of the error becomes: [-PI+offset,PI+offset] where offset is in [-PI, PI]. Using this feature, it is possible to set the preferred direction of travel for the motor.

void PositionControl::setTorqueOffset (  float  torque  )  [inline]

This method sets the value of the feedforward torque command for PD computations

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RHexLib Reference Documentation