maspack.spatialmotion

Class EllipsoidCoupling

java.lang.Object

maspack.spatialmotion.RigidBodyCoupling

maspack.spatialmotion.EllipsoidCoupling

All Implemented Interfaces:

java.lang.Cloneable

public class EllipsoidCoupling
extends RigidBodyCoupling

Constrains a coordinate frame to the surface of an ellipsoid, together with two additional degrees of rotational freedom.

Field Summary

Fields

Modifier and Type	Field and Description
static int	LATITUDE_IDX
static int	LONGITUDE_IDX
boolean	myOpenSimCompatible
static int	PHI_IDX
static int	THETA_IDX

Fields inherited from class maspack.spatialmotion.RigidBodyCoupling

debug

Constructor Summary

Constructors

Constructor and Description
EllipsoidCoupling()
EllipsoidCoupling(double a, double b, double c, double alpha)
EllipsoidCoupling(double a, double b, double c, double alpha, boolean openSimCompatible)

Method Summary

Modifier and Type	Method and Description
MatrixNd	computeCoordinateJacobian(RigidTransform3d TGD) Computes the coordinate Jacobian.
void	coordinatesToTCD(RigidTransform3d TCD, double longitude, double latitude, double theta, double phi)
void	coordinatesToTCD(RigidTransform3d TCD, VectorNd coords) Computes the TCD transform for a set of coordinates, if coordinates are supported.
double	getAlpha()
Vector3d	getSemiAxisLengths()
void	initializeConstraints() Called inside the RigidBodyCoupling constructor to allocate constraint and coordinate information, using calls to the addConstraint and addCoordinate methods.
boolean	isOpenSimCompatible()
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	setAlpha(double alpha)
void	setOpenSimCompatible(boolean enable)
void	setSemiAxisLengths(Vector3d lengths)
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, clone, 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

LONGITUDE_IDX

public static final int LONGITUDE_IDX

See Also:

Constant Field Values

LATITUDE_IDX

public static final int LATITUDE_IDX

See Also:

Constant Field Values

THETA_IDX

public static final int THETA_IDX

See Also:

Constant Field Values

PHI_IDX

public static final int PHI_IDX

See Also:

Constant Field Values

myOpenSimCompatible

public boolean myOpenSimCompatible

Constructor Detail

EllipsoidCoupling

public EllipsoidCoupling()

EllipsoidCoupling

public EllipsoidCoupling(double a,
                         double b,
                         double c,
                         double alpha)

EllipsoidCoupling

public EllipsoidCoupling(double a,
                         double b,
                         double c,
                         double alpha,
                         boolean openSimCompatible)

Method Detail

isOpenSimCompatible

public boolean isOpenSimCompatible()

setOpenSimCompatible

public void setOpenSimCompatible(boolean enable)

setSemiAxisLengths

public void setSemiAxisLengths(Vector3d lengths)

getSemiAxisLengths

public Vector3d getSemiAxisLengths()

setAlpha

public void setAlpha(double alpha)

getAlpha

public double getAlpha()

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

computeCoordinateJacobian

public MatrixNd computeCoordinateJacobian(RigidTransform3d TGD)

Computes the coordinate Jacobian. This is a 6 x numc matrix that maps coordinate speeds onto spatial velocities in the C frame.

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,
                             double longitude,
                             double latitude,
                             double theta,
                             double phi)

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().