WheeledWalkMC Class Reference

Provides a 'WalkMC' implementation for wheeled robots (diff-drive or theoretically holonomic configurations as well). More...

#include <WheeledWalkMC.h>

Inheritance diagram for WheeledWalkMC:

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Detailed Description

Provides a 'WalkMC' implementation for wheeled robots (diff-drive or theoretically holonomic configurations as well).

Uses kinematic description to determine location and orientation of wheels and computes appropriate wheel velocities to produce a target motion. Can handle skid-steer (diff drive) type motion, including holonomic wheels, but does not handle ackerman style (steered) configurations.

Also does not handle 'slanted' wheels optimally: Assumes wheels are perpendicular to the ground, that the base frame Z axis is perpendicular to the ground frame. This could be added with a bit more math when computing wheel positions.

This motion command also assumes that wheels are commanded by mm/sec ground speed, not rad/sec rotational speed.

For simulation in Mirage, make sure all wheels are marked by adding a Velocity=true entry in the ControllerInfo of the corresponding kinematics configuration, and that the x and y dimensions of the collision model are set for the wheel radius.

TODO: Test on a holonomic platform, should handle it, but originally only tested on diff-drive like Create. Also, perhaps add config settings to override rotationCenter and a flag to have updateWheelConfig called before each updateOutputs.

Definition at line 32 of file WheeledWalkMC.h.

List of all members.

Classes
struct	WheelInfo
	stores information about the configuration and current target state of each wheel More...
Public Member Functions
	WheeledWalkMC ()
	constructor
void	resetConfig ()
	reset and reload configuration settings, implies call to updateWheelConfig()
void	setDirty ()
virtual int	updateOutputs ()
	is called once per update cycle, can do any processing you need to change your priorities or set output commands on the MotionManager
virtual int	isDirty ()
	not used by MotionManager at the moment, but could be used to reduce recomputation, and you may find it useful
virtual int	isAlive ()
	used to prune "dead" motions from the MotionManager
virtual void	start ()
	called after this is added to MotionManager; don't override this, use doStart instead
virtual void	stop ()
	called after this is removed from MotionManager; don't override this, use doStop instead
virtual void	zeroVelocities ()
	Posts a LocomotionEvent and sets velocities to zero. Also forces an output frame setting wheel velocities to zero; needed because if we remove a motion command there may be nothing left to zero the velocities.
float	getMaxXVel () const
float	getMaxYVel () const
float	getMaxAVel () const
unsigned int	getTravelTime ()
	the amount of time (ms) we have been travelling the current vector
const fmat::Column< 2 > &	getTargetVelocity () const
	Returns the current x and y velocities in mm/sec.
float	getTargetAngVelocity () const
	Returns the current angular velocity in radians/sec.
virtual void	getTargetVelocity (float &xvel, float &yvel, float &avel)
	Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second).
virtual void	setTargetVelocity (float xvel, float yvel, float avel)
	Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second); does not stop automatically.
virtual void	setTargetVelocity (float xvel, float yvel, float avel, float time)
	Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second), and amount of time before stopping.
virtual void	setTargetDisplacement (float xdisp, float ydisp, float adisp, float time=0)
	Specify the desired body displacement in x and y (millimeters) and a (radians).
void	setTargetDisplacement (float xdisp, float ydisp, float adisp, float xvel, float yvel, float avel)
	Specify body displacement and speed.
virtual void	updateWheelConfig ()
	Recomputes wheel positions and orientations. Automatically called by constructor, but may need to recall if wheel positions are actuated.
Public Attributes
plist::Primitive< float >	preferredXVel
	optimal X velocity for unspecified displacements
plist::Primitive< float >	preferredYVel
	optimal Y velocity for unspecified displacements
plist::Primitive< float >	preferredAngVel
	optimal angular velocity for unspecified displacements
Protected Member Functions
void	updateWheelVels ()
	updates WheelInfo::targetVel values based on targetVel and targetAngVel
Protected Attributes
fmat::Column< 2 >	targetVel
	the requested xy velocity of the body (ignoring parameterized body motion, like sway or surge), millimeters per second
float	targetAngVel
	the requested angular velocity of the body, radians per second
unsigned int	targetDur
	duration in msecs for the current displacement
float	targetDist
	forward distance we want to travel
float	targetAngDist
	angular distance we want to travel
fmat::Column< 2 >	maxVel
	maximum velocity in x,y
float	maxAngVel
	maximum angular velocity
fmat::Column< 2 >	rotationCenter
	point to use as center of rotations, defaults to center of wheels
bool	displacementMode
	If true, velocity will be set to 0 when desired displacement is achieved.
unsigned int	travelStartTime
	the time of the last call to setTargetVelocity - handy to check the time we've been traveling current vector
float	travelStartDist
	The forward odometry reading in millimeters at the time of the last call to setTargetVelocity.
float	travelStartAngle
	The angular odometry reading in radians at the time of the last call to setTargetVelocity.
bool	dirty
	set to true by updateWheelVels(), cleared up updateOutputs()
WheelInfo	wheels [NumWheels]
Static Protected Attributes
static constexpr float	EPSILON = 1e-4f

Constructor & Destructor Documentation

WheeledWalkMC::WheeledWalkMC ( )

constructor

Definition at line 35 of file WheeledWalkMC.h.

Member Function Documentation

float WheeledWalkMC::getMaxAVel ( ) const

Definition at line 70 of file WheeledWalkMC.h.

float WheeledWalkMC::getMaxXVel ( ) const

Definition at line 68 of file WheeledWalkMC.h.

float WheeledWalkMC::getMaxYVel ( ) const

Definition at line 69 of file WheeledWalkMC.h.

float WheeledWalkMC::getTargetAngVelocity ( ) const

Returns the current angular velocity in radians/sec.

Definition at line 78 of file WheeledWalkMC.h.

virtual void WheeledWalkMC::getTargetVelocity	(	float &	xvel,
		float &	yvel,
		float &	avel
	)			`[virtual]`

Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second).

Definition at line 81 of file WheeledWalkMC.h.

const fmat::Column<2>& WheeledWalkMC::getTargetVelocity ( ) const

Returns the current x and y velocities in mm/sec.

Definition at line 75 of file WheeledWalkMC.h.

unsigned int WheeledWalkMC::getTravelTime ( )

the amount of time (ms) we have been travelling the current vector

Definition at line 72 of file WheeledWalkMC.h.

virtual int WheeledWalkMC::isAlive ( ) [virtual]

used to prune "dead" motions from the MotionManager

note that a motion could be "paused" or inactive and therefore not dirty, but still alive, biding its time to "strike" ;)

Returns:: zero if the motion is still processing, non-zero otherwise

Implements MotionCommand.

virtual int WheeledWalkMC::isDirty ( ) [virtual]

not used by MotionManager at the moment, but could be used to reduce recomputation, and you may find it useful

Returns:: zero if none of the commands have changed since last getJointCmd(), else non-zero

Implements MotionCommand.

Definition at line 60 of file WheeledWalkMC.h.

void WheeledWalkMC::resetConfig ( )

reset and reload configuration settings, implies call to updateWheelConfig()

Referenced by WheeledWalkMC().

void WheeledWalkMC::setDirty ( )

Definition at line 57 of file WheeledWalkMC.h.

void WheeledWalkMC::setTargetDisplacement	(	float	xdisp,
		float	ydisp,
		float	adisp,
		float	xvel,
		float	yvel,
		float	avel
	)

Specify body displacement and speed.

virtual void WheeledWalkMC::setTargetDisplacement	(	float	xdisp,
		float	ydisp,
		float	adisp,
		float	time = `0`
	)			`[virtual]`

Specify the desired body displacement in x and y (millimeters) and a (radians).

Corresponding velocity will be limited to max velocity, so setting time=0 implies max speed

virtual void WheeledWalkMC::setTargetVelocity	(	float	xvel,
		float	yvel,
		float	avel,
		float	time
	)			`[virtual]`

Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second), and amount of time before stopping.

virtual void WheeledWalkMC::setTargetVelocity	(	float	xvel,
		float	yvel,
		float	avel
	)			`[virtual]`

Specify the desired body velocity in x and y (millimeters per second) and angular velocity (radians per second); does not stop automatically.

virtual void WheeledWalkMC::start ( ) [virtual]

called after this is added to MotionManager; don't override this, use doStart instead

Reimplemented from MotionCommand.

virtual void WheeledWalkMC::stop ( ) [virtual]

called after this is removed from MotionManager; don't override this, use doStop instead

Reimplemented from MotionCommand.

virtual int WheeledWalkMC::updateOutputs ( ) [virtual]

is called once per update cycle, can do any processing you need to change your priorities or set output commands on the MotionManager

Returns:: zero if no changes were made, non-zero otherwise

See also:: RobotInfo::NumFrames; RobotInfo::FrameTime

Implements MotionCommand.

virtual void WheeledWalkMC::updateWheelConfig ( ) [virtual]

Recomputes wheel positions and orientations. Automatically called by constructor, but may need to recall if wheel positions are actuated.

Includes a call to updateWheelVels() in case wheel positions change.

void WheeledWalkMC::updateWheelVels ( ) [protected]

updates WheelInfo::targetVel values based on targetVel and targetAngVel

virtual void WheeledWalkMC::zeroVelocities ( ) [virtual]

Posts a LocomotionEvent and sets velocities to zero. Also forces an output frame setting wheel velocities to zero; needed because if we remove a motion command there may be nothing left to zero the velocities.