maspack.spatialmotion

Class FixedAxisCoupling

java.lang.Object

maspack.spatialmotion.RigidBodyCoupling

maspack.spatialmotion.FixedAxisCoupling

All Implemented Interfaces:

java.lang.Cloneable

public class FixedAxisCoupling
extends RigidBodyCoupling

Implements a fixed axis coupling - which is a roll-pitch coupling with no translational constraint and no joint limits.

Field Summary

Fields

Modifier and Type	Field and Description
static int	PITCH_IDX
static int	ROLL_IDX
static int	X_IDX
static int	Y_IDX
static int	Z_IDX

Fields inherited from class maspack.spatialmotion.RigidBodyCoupling

debug

Constructor Summary

Constructors

Constructor and Description
FixedAxisCoupling()

Method Summary

Modifier and Type	Method and Description
FixedAxisCoupling	clone()
void	coordinatesToTCD(RigidTransform3d TCD, VectorNd coords) Computes the TCD transform for a set of coordinates, if coordinates are supported.
void	initializeConstraints() Called inside the RigidBodyCoupling constructor to allocate constraint and coordinate information, using calls to the addConstraint and addCoordinate methods.
void	projectToConstraints(RigidTransform3d TGD, RigidTransform3d TCD, VectorNd coords) Project a transform TCD onto the nearest transform TGD that is legal given this coupling's bilateral constraints.
void	TCDToCoordinates(VectorNd coords, RigidTransform3d TCD) If coordinates are supported by this coupling, compute their values based on the supplied transform TCD from frame C to D, and return the result in coords.
void	updateConstraints(RigidTransform3d TGD, RigidTransform3d TCD, Twist errC, Twist velGD, boolean updateEngaged) Called from RigidBodyCoupling.updateBodyStates(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.spatialmotion.Twist, boolean) to update the constraints, usually once per simulation step.

Methods inherited from class maspack.spatialmotion.RigidBodyCoupling

clipCoordinate, coordinatesToTCD, findNearestAngle, getBilateralConstraints, getBilateralForceG, getBilateralForces, getBreakSpeed, getCompliance, getConstraint, getConstraintFlags, getConstraintForce, getCoordinate, getCoordinateIndex, getCoordinateMotionType, getCoordinateName, getCoordinateRange, getCoordinates, getCoordinateSpeed, getCoordinateWrench, getDamping, getLinearLimitTol, getRotaryLimitTol, getState, getUnilateralConstraints, getUnilateralForceG, getUnilateralForces, getUnilateralState, isCoordinateLocked, main, numBilaterals, numConstraints, numCoordinates, numEngagedUnilaterals, numUnilaterals, printConstraintInfo, projectAndUpdateCoordinates, scaleDistance, setBilateralForces, setBreakSpeed, setCompliance, setCoordinateLocked, setCoordinateName, setCoordinateRange, setCoordinateValue, setCoordinateValues, setDamping, setLinearLimitTol, setRotaryLimitTol, setState, setUnilateralForces, setUnilateralState, transformGeometry, updateBodyStates, updateUnilateralConstraints, zeroForces

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

X_IDX

public static final int X_IDX

See Also:

Constant Field Values

Y_IDX

public static final int Y_IDX

See Also:

Constant Field Values

Z_IDX

public static final int Z_IDX

See Also:

Constant Field Values

ROLL_IDX

public static final int ROLL_IDX

See Also:

Constant Field Values

PITCH_IDX

public static final int PITCH_IDX

See Also:

Constant Field Values

Constructor Detail

FixedAxisCoupling

public FixedAxisCoupling()

Method Detail

projectToConstraints

public void projectToConstraints(RigidTransform3d TGD,
                                 RigidTransform3d TCD,
                                 VectorNd coords)

Description copied from class: RigidBodyCoupling

Project a transform TCD onto the nearest transform TGD that is legal given this coupling's bilateral constraints. In more detail, given a transform TCD from frame C to D, find the frame G that is nearest to C while lying on the constraint surface defined by the bilateral constraints. Subclasses should implement this method as needed.

Optionally, the coupling may also extend the projection to include unilateral constraints that are not associated with coordinate limits. In particular, this should be done for constraints for which is it desired to have the constraint error included in the errC argument that is passed to RigidBodyCoupling.updateConstraints(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.spatialmotion.Twist, maspack.spatialmotion.Twist, boolean).

If this coupling supports coordinates and coords is non-null, then the coordinate values corresponding to TGD should also be computed and returned in coords. The easiest way to do this is to simply call RigidBodyCoupling.TCDToCoordinates(maspack.matrix.VectorNd, maspack.matrix.RigidTransform3d), although in some cases it may be computationally cheaper to compute both the coordinates and the projection at the same time. The method should not clip the resulting coordinates to their range limits.

Specified by:

projectToConstraints in class RigidBodyCoupling

Parameters:

TGD - returns the nearest transform to TCD that is legal with respect to the bilateral (and possibly some unilateral) constraints

TCD - transform from frame C to D to be projected

coords - if non-null, should be used to return coordinate values

initializeConstraints

public void initializeConstraints()

Description copied from class: RigidBodyCoupling

Called inside the RigidBodyCoupling constructor to allocate constraint and coordinate information, using calls to the addConstraint and addCoordinate methods. The method may be called at other times if the constraints need to be reconfigured (such as when switching constraints between bilateral and unilateral). Subclasses should implement this method as needed.

Specified by:

initializeConstraints in class RigidBodyCoupling

updateConstraints

public void updateConstraints(RigidTransform3d TGD,
                              RigidTransform3d TCD,
                              Twist errC,
                              Twist velGD,
                              boolean updateEngaged)

Description copied from class: RigidBodyCoupling

Called from RigidBodyCoupling.updateBodyStates(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.spatialmotion.Twist, boolean) to update the constraints, usually once per simulation step. This method is responsible for:

• Updating the values of all non-constant constraint wrenches, along with their derivatives;
• If updateEngaged is true, updating the engaged and distance attributes for all unilateral constraints not associated with a joint limit.

Wrenches and their derivatives should be computed with respect to frame G, which is frame C with the constraint errors removed.

If the coupling supports coordinates, their values will be updated before this method is called so as to correspond to TGD.

Specified by:

updateConstraints in class RigidBodyCoupling

Parameters:

TGD - idealized joint transform from frame G to D, obtained by calling RigidBodyCoupling.projectToConstraints(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.matrix.VectorNd) on TCD

TCD - actual joint transform from frame C to D; included for legacy reasons and not normally used

errC - error transform from frame C to G, represented as a Twist

velGD - velocity of frame G with respect to D, as seen in frame G

updateEngaged - if true, requests the updating of unilateral engaged and distance attributes as describe above.

TCDToCoordinates

public void TCDToCoordinates(VectorNd coords,
                             RigidTransform3d TCD)

Description copied from class: RigidBodyCoupling

If coordinates are supported by this coupling, compute their values based on the supplied transform TCD from frame C to D, and return the result in coords. Otherwise this method does nothing.

It is assumed that TCD is legal with respect the coupling's bilateral constraints, as defined by RigidBodyCoupling.projectToConstraints(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.matrix.VectorNd); otherwise, RigidBodyCoupling.projectToConstraints(maspack.matrix.RigidTransform3d, maspack.matrix.RigidTransform3d, maspack.matrix.VectorNd) should be used instead.

When setting coordinate values, they should not be clipped to their maximum and minimum values (as defined by RigidBodyCoupling.getCoordinateRange(int).

Overrides:

TCDToCoordinates in class RigidBodyCoupling

Parameters:

coords - returns the coordinate values

TCD - transform from frame C to D

coordinatesToTCD

public void coordinatesToTCD(RigidTransform3d TCD,
                             VectorNd coords)

Computes the TCD transform for a set of coordinates, if coordinates are supported. Otherwise this method does nothing. Subclasses should implement this method as needed.

Specified by:

coordinatesToTCD in class RigidBodyCoupling

Parameters:

TCD - returns the TCD transform

coords - supplies the coordinate values and must have a length >= RigidBodyCoupling.numCoordinates().

clone

public FixedAxisCoupling clone()

Overrides:

clone in class RigidBodyCoupling