This constraint consists of a single constraint equation that enforces that a unit vector v1 fixed to one body (the "base body") must maintain a fixed angle theta with respect to a unit vector v2 fixed on the other body (the "follower body").
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| ConstantAngle (MobilizedBody &baseBody_B, const UnitVec3 &defaultAxis_B, MobilizedBody &followerBody_F, const UnitVec3 &defaultAxis_F, Real angle=Pi/2) |
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| ConstantAngle () |
| Default constructor creates an empty handle. More...
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ConstantAngle & | setAxisDisplayLength (Real) |
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ConstantAngle & | setAxisDisplayWidth (Real) |
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Real | getAxisDisplayLength () const |
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Real | getAxisDisplayWidth () const |
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ConstantAngle & | setDefaultBaseAxis (const UnitVec3 &) |
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ConstantAngle & | setDefaultFollowerAxis (const UnitVec3 &) |
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ConstantAngle & | setDefaultAngle (Real) |
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MobilizedBodyIndex | getBaseMobilizedBodyIndex () const |
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MobilizedBodyIndex | getFollowerMobilizedBodyIndex () const |
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const UnitVec3 & | getDefaultBaseAxis () const |
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const UnitVec3 & | getDefaultFollowerAxis () const |
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Real | getDefaultAngle () const |
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const UnitVec3 & | getBaseAxis (const State &) const |
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const UnitVec3 & | getFollowerAxis (const State &) const |
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Real | getAngle (const State &) const |
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Real | getPositionError (const State &) const |
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Real | getVelocityError (const State &) const |
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Real | getAccelerationError (const State &) const |
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Real | getMultiplier (const State &) const |
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Real | getTorqueOnFollowerBody (const State &) const |
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| Constraint () |
| Default constructor creates an empty Constraint handle that can be used to reference any Constraint. More...
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| Constraint (ConstraintImpl *r) |
| For internal use: construct a new Constraint handle referencing a particular implementation object. More...
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void | disable (State &) const |
| Disable this Constraint, effectively removing it from the system. More...
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void | enable (State &) const |
| Enable this Constraint, without necessarily satisfying it. More...
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bool | isDisabled (const State &) const |
| Test whether this constraint is currently disabled in the supplied State. More...
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bool | isDisabledByDefault () const |
| Test whether this Constraint is disabled by default in which case it must be explicitly enabled before it will take effect. More...
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void | setDisabledByDefault (bool shouldBeDisabled) |
| Normally Constraints are enabled when defined and can be disabled later. More...
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| operator ConstraintIndex () const |
| This is an implicit conversion from Constraint to ConstraintIndex when needed. More...
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const SimbodyMatterSubsystem & | getMatterSubsystem () const |
| Get a const reference to the matter subsystem that contains this Constraint. More...
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SimbodyMatterSubsystem & | updMatterSubsystem () |
| Assuming you have writable access to this Constraint, get a writable reference to the containing matter subsystem. More...
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ConstraintIndex | getConstraintIndex () const |
| Get the ConstraintIndex that was assigned to this Constraint when it was added to the matter subsystem. More...
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bool | isInSubsystem () const |
| Test whether this Constraint is contained within a matter subsystem. More...
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bool | isInSameSubsystem (const MobilizedBody &mobod) const |
| Test whether the supplied MobilizedBody is in the same matter subsystem as this Constraint. More...
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int | getNumConstrainedBodies () const |
| Return the number of unique bodies directly restricted by this constraint. More...
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const MobilizedBody & | getMobilizedBodyFromConstrainedBody (ConstrainedBodyIndex consBodyIx) const |
| Return a const reference to the actual MobilizedBody corresponding to one of the Constrained Bodies included in the count returned by getNumConstrainedBodies(). More...
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const MobilizedBody & | getAncestorMobilizedBody () const |
| Return a const reference to the actual MobilizedBody which is serving as the Ancestor body for the constrained bodies in this Constraint. More...
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int | getNumConstrainedMobilizers () const |
| Return the number of unique mobilizers directly restricted by this Constraint. More...
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const MobilizedBody & | getMobilizedBodyFromConstrainedMobilizer (ConstrainedMobilizerIndex consMobilizerIx) const |
| Return a const reference to the actual MobilizedBody corresponding to one of the Constrained Mobilizers included in the count returned by getNumConstrainedMobilizers(). More...
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const SimbodyMatterSubtree & | getSubtree () const |
| Return a subtree object indicating which parts of the multibody tree are potentially affected by this Constraint. More...
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int | getNumConstrainedQ (const State &, ConstrainedMobilizerIndex) const |
| Return the number of constrainable generalized coordinates q associated with a particular constrained mobilizer. More...
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int | getNumConstrainedU (const State &, ConstrainedMobilizerIndex) const |
| Return the number of constrainable mobilities u associated with a particular constrained mobilizer. More...
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ConstrainedUIndex | getConstrainedUIndex (const State &, ConstrainedMobilizerIndex, MobilizerUIndex which) const |
| Return the index into the constrained mobilities u array corresponding to a particular mobility of the indicated ConstrainedMobilizer. More...
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ConstrainedQIndex | getConstrainedQIndex (const State &, ConstrainedMobilizerIndex, MobilizerQIndex which) const |
| Return the index into the constrained coordinates q array corresponding to a particular coordinate of the indicated ConstrainedMobilizer. More...
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int | getNumConstrainedQ (const State &) const |
| Return the sum of the number of coordinates q associated with each of the constrained mobilizers. More...
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int | getNumConstrainedU (const State &) const |
| Return the sum of the number of mobilities u associated with each of the constrained mobilizers. More...
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QIndex | getQIndexOfConstrainedQ (const State &state, ConstrainedQIndex consQIndex) const |
| Map one of this Constraint's constrained q's to the corresponding index within the matter subsystem's whole q vector. More...
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UIndex | getUIndexOfConstrainedU (const State &state, ConstrainedUIndex consUIndex) const |
| Map one of this Constraint's constrained U's (or mobilities) to the corresponding index within the matter subsystem's whole u vector. More...
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void | getNumConstraintEquationsInUse (const State &state, int &mp, int &mv, int &ma) const |
| Find out how many holonomic (position), nonholonomic (velocity), and acceleration-only constraint equations are currently being generated by this Constraint. More...
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void | getIndexOfMultipliersInUse (const State &state, MultiplierIndex &px0, MultiplierIndex &vx0, MultiplierIndex &ax0) const |
| Return the start of the blocks of multipliers (or acceleration errors) assigned to this Constraint. More...
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void | setMyPartInConstraintSpaceVector (const State &state, const Vector &myPart, Vector &constraintSpace) const |
| Set the part of a complete constraint-space vector that belongs to this constraint. More...
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void | getMyPartFromConstraintSpaceVector (const State &state, const Vector &constraintSpace, Vector &myPart) const |
| Get the part of a complete constraint-space vector that belongs to this constraint. More...
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Vector | getPositionErrorsAsVector (const State &) const |
| Get a Vector containing the position errors. More...
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Vector | calcPositionErrorFromQ (const State &, const Vector &q) const |
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Matrix | calcPositionConstraintMatrixP (const State &) const |
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Matrix | calcPositionConstraintMatrixPt (const State &) const |
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Matrix | calcPositionConstraintMatrixPNInv (const State &) const |
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void | calcConstraintForcesFromMultipliers (const State &, const Vector &lambda, Vector_< SpatialVec > &bodyForcesInA, Vector &mobilityForces) const |
| This operator calculates this constraint's body and mobility forces given the complete set of multipliers lambda for this Constraint. More...
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Vector | getVelocityErrorsAsVector (const State &) const |
| Get a Vector containing the velocity errors. More...
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Vector | calcVelocityErrorFromU (const State &, const Vector &u) const |
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Matrix | calcVelocityConstraintMatrixV (const State &) const |
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Matrix | calcVelocityConstraintMatrixVt (const State &) const |
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Vector | getAccelerationErrorsAsVector (const State &) const |
| Get a Vector containing the acceleration errors. More...
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Vector | calcAccelerationErrorFromUDot (const State &, const Vector &udot) const |
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Vector | getMultipliersAsVector (const State &) const |
| Get a Vector containing the Lagrange multipliers. More...
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void | getConstraintForcesAsVectors (const State &state, Vector_< SpatialVec > &bodyForcesInG, Vector &mobilityForces) const |
| Given a State realized through Acceleration stage, return the forces that were applied to the system by this Constraint, with body forces expressed in Ground. More...
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Vector_< SpatialVec > | getConstrainedBodyForcesAsVector (const State &state) const |
| For convenience, returns constrained body forces as the function return. More...
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Vector | getConstrainedMobilityForcesAsVector (const State &state) const |
| For convenience, returns constrained mobility forces as the function return. More...
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Real | calcPower (const State &state) const |
| Calculate the power being applied by this Constraint to the system. More...
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Matrix | calcAccelerationConstraintMatrixA (const State &) const |
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Matrix | calcAccelerationConstraintMatrixAt (const State &) const |
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void | setIsConditional (bool isConditional) |
| (Advanced) Mark this constraint as one that is only conditionally active. More...
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bool | isConditional () const |
| (Advanced) Get the value of the isConditional flag. More...
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Public Member Functions inherited from SimTK::PIMPLHandle< Constraint, ConstraintImpl, true > |
bool | isEmptyHandle () const |
| Returns true if this handle is empty, that is, does not refer to any implementation object. More...
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bool | isOwnerHandle () const |
| Returns true if this handle is the owner of the implementation object to which it refers. More...
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bool | isSameHandle (const Constraint &other) const |
| Determine whether the supplied handle is the same object as "this" PIMPLHandle. More...
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void | disown (Constraint &newOwner) |
| Give up ownership of the implementation to an empty handle. More...
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PIMPLHandle & | referenceAssign (const Constraint &source) |
| "Copy" assignment but with shallow (pointer) semantics. More...
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PIMPLHandle & | copyAssign (const Constraint &source) |
| This is real copy assignment, with ordinary C++ object ("value") semantics. More...
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void | clearHandle () |
| Make this an empty handle, deleting the implementation object if this handle is the owner of it. More...
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const ConstraintImpl & | getImpl () const |
| Get a const reference to the implementation associated with this Handle. More...
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ConstraintImpl & | updImpl () |
| Get a writable reference to the implementation associated with this Handle. More...
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int | getImplHandleCount () const |
| Return the number of handles the implementation believes are referencing it. More...
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This constraint consists of a single constraint equation that enforces that a unit vector v1 fixed to one body (the "base body") must maintain a fixed angle theta with respect to a unit vector v2 fixed on the other body (the "follower body").
This can be done with a single constraint equation as long as theta is sufficiently far away from 0 and +/-Pi (180 degrees), with the numerically best performance at theta=Pi/2 (90 degrees).
- Warning
- Do not use this constraint to align the vectors, that is for angles near 0 or +/- Pi; performance will noticeably degrade within a few degrees of these limits and numerical integration will eventually fail at the limits.
If you want to enforce that two axes are aligned with one another (that is, the angle between them is 0 or +/-Pi), that takes two constraint equations since the only remaining rotation is about the common axis. (That is, two rotational degrees of freedom are removed; that can't be done with one constraint equation – the situation is analogous to the inability of a Rod (distance) constraint to keep two points at 0 distance.) Instead, you can use two ConstantAngle constraints on pairs of vectors perpendicular to the aligned ones, so that each ConstantAngle is set to the optimal 90 degrees.
This constraint is enforced by an internal scalar torque applied equal and opposite on each body, about the mutual perpendicular to the two vectors.
The assembly condition is the same as the run-time constraint: the bodies must be rotated until the vectors have the right angle between them.