chrono::ChLinkMotionImposed Class Reference
Description
A joint to enforce position and rotation between two frames on two bodies, using six rheonomic constraints.
That is, position and rotation of Body 1 are precisely enforced respect to Body 2 by using functions of time, where functions are defined via ChFunctionRotation and ChFunctionPosition objects. A typical usage scenario is where Body 2 is a fixed body, representing the absolute reference, so you move/rotate Body 1 in space according to the provided functions; this is the case for example where you have some data coming from a motion capture hardware following the motion, say, of a human head, and you want to replicate the motion of that head in 3D space. This joint imposes all the 6 DOFs of a body, including rotations, differently from the ChLinkLockTrajectory that imposes only the position but leaves rotation free.
Notes
- if you are interested in simply imposing a straight motion, just use ChLinkMotorLinearPosition, and if you just need to impose a rotation on a shaft, just use the ChLinkMotorRotationAngle.
- no compliance is allowed, so if the imposed motion hits an undeformable obstacle it mets a pathological situation and the solver result can be unstable/unpredictable. Think at it as a 6DOF servo drive with "infinitely stiff" control.
By default it is initialized with no motion / no rotation, so by default is just like welding the two bodies, so it is up to the user to provide proper ChFunctionRotation and a proper ChFunctionPosition. Note: differently from most other ChLinkMate-inherited links, that assume the frame2 as link coodrinate system, in this case we use the "moving" auxiliary frame M whose motion is concatenated to frame2 (in absolute coordinates, such moving frame will be coincident with frame1 if the constraint is well assembled - in fact this makes constraint forces more intuitive, as one will get reaction forces and torques as applied to the frame1 of moving body 1).
#include <ChLinkMotionImposed.h>
Inheritance diagram for chrono::ChLinkMotionImposed:
Collaboration diagram for chrono::ChLinkMotionImposed:
Public Member Functions | |
| ChLinkMotionImposed (const ChLinkMotionImposed &other) | |
| virtual ChLinkMotionImposed * | Clone () const override |
| "Virtual" copy constructor (covariant return type). | |
| void | SetPositionFunction (std::shared_ptr< ChFunctionPosition > mf) |
| Set the position function for a generic 3D rotation, as p=p(t) vector function. More... | |
| std::shared_ptr< ChFunctionPosition > | GetPositionFunction () const |
| Get the position function q=q(t). | |
| void | SetRotationFunction (std::shared_ptr< ChFunctionRotation > mf) |
| Set the rotation function for a generic 3D rotation, as q=q(t) quaternion rotation function. More... | |
| std::shared_ptr< ChFunctionRotation > | GetRotationFunction () const |
| Get the rotation function q=q(t). | |
| ChFrame & | GetFrameM2 () |
| For plotting etc: get the last computed value of imposed rotation and position, expressed as the "moving" ChFrame M respect to frame2. | |
| virtual ChFramed | GetFrame2Rel () const override |
| Get the link frame 2, relative to body 2. | |
| virtual void | LoadKRMMatrices (double Kfactor, double Rfactor, double Mfactor) override |
| Add the current stiffness K matrix in encapsulated ChKRMBlock item(s), if any. More... | |
| virtual void | ArchiveOut (ChArchiveOut &archive_out) override |
| Method to allow serialization of transient data to archives. | |
| virtual void | ArchiveIn (ChArchiveIn &archive_in) override |
| Method to allow deserialization of transient data from archives. More... | |
 Public Member Functions inherited from chrono::ChLinkMateGeneric | |
| ChLinkMateGeneric (bool mc_x=true, bool mc_y=true, bool mc_z=true, bool mc_rx=true, bool mc_ry=true, bool mc_rz=true) | |
| ChLinkMateGeneric (const ChLinkMateGeneric &other) | |
| virtual ChFrame | GetVisualModelFrame (unsigned int nclone=0) const override |
| Get the reference frame (expressed in and relative to the absolute frame) of the visual model. More... | |
| virtual ChFramed | GetFrame1Rel () const override |
| Get the link frame 1, relative to body 1. | |
| bool | IsConstrainedX () const |
| bool | IsConstrainedY () const |
| bool | IsConstrainedZ () const |
| bool | IsConstrainedRx () const |
| bool | IsConstrainedRy () const |
| bool | IsConstrainedRz () const |
| void | SetConstrainedCoords (bool mc_x, bool mc_y, bool mc_z, bool mc_rx, bool mc_ry, bool mc_rz) |
| Sets which movements (of frame 1 respect to frame 2) are constrained. | |
| virtual void | Initialize (std::shared_ptr< ChBodyFrame > body1, std::shared_ptr< ChBodyFrame > body2, ChFrame<> absframe) |
| Initialize the link given the two bodies to be connected and the absolute position of the link. More... | |
| virtual void | Initialize (std::shared_ptr< ChBodyFrame > body1, std::shared_ptr< ChBodyFrame > body2, bool pos_are_relative, ChFrame<> frame1, ChFrame<> frame2) |
| Initialize the link given the two bodies to be connected and two frames (either referring to absolute or body coordinates) in which the link must be placed. More... | |
| virtual void | Initialize (std::shared_ptr< ChBodyFrame > body1, std::shared_ptr< ChBodyFrame > body2, bool pos_are_relative, const ChVector3d &point1, const ChVector3d &point2, const ChVector3d &dir1, const ChVector3d &dir2) |
| Initialization based on passing two vectors (point + dir) on the two bodies, which will represent the Z axes of the two frames (X and Y will be built from the Z vector via Gram-Schmidt orthonormalization). More... | |
| virtual void | SetDisabled (bool mdis) override |
| Enable/disable all the constraint of the link as desired. | |
| virtual void | SetBroken (bool mon) override |
| Set this link as 'broken'. | |
| void | SetUseTangentStiffness (bool useKc) |
| Enable/disable calculation of the tangent stiffness matrix (Kc) of this constraint (default: false). | |
| virtual unsigned int | GetNumConstraints () override |
| Get the number of scalar constraints. | |
| virtual unsigned int | GetNumConstraintsBilateral () override |
| Get the number of bilateral scalar constraints. | |
| virtual unsigned int | GetNumConstraintsUnilateral () override |
| Get the number of unilateral scalar constraints. | |
| virtual ChVectorDynamic | GetConstraintViolation () const override |
| Link violation (residuals of the link constraint equations). | |
| Public Member Functions inherited from chrono::ChLinkMate | |
| ChLinkMate (const ChLinkMate &other) | |
| Public Member Functions inherited from chrono::ChLink | |
| ChLink (const ChLink &other) | |
| virtual unsigned int | GetNumAffectedCoords () override |
| Get the number of scalar variables affected by constraints in this link. | |
| ChBodyFrame * | GetBody1 () const |
| Get the constrained body 1. | |
| ChBodyFrame * | GetBody2 () const |
| Get the constrained body 2. | |
| virtual ChFramed | GetFrame1Abs () const override |
| Get the link frame 1, on body 1, expressed in the absolute frame. | |
| virtual ChFramed | GetFrame2Abs () const override |
| Get the link frame 2, on body 2, expressed in the absolute frame. | |
| virtual ChWrenchd | GetReaction1 () const override |
| Get the reaction force and torque on the 1st body, expressed in the link frame 1. | |
| virtual ChWrenchd | GetReaction2 () const override |
| Get the reaction force and torque on the 2nd body object, expressed in the link frame 2. | |
| virtual void | UpdateTime (double mytime) |
| Given new time, current body state, update time-dependent quantities in link state, for example motion laws, moving markers, etc. More... | |
| virtual void | Update (bool update_assets=true) override |
| As above, but with current time. | |
| virtual void | UpdatedExternalTime (double prevtime, double time) |
| Called from a external package (i.e. a plugin, a CAD app.) to report that time has changed. | |
| Public Member Functions inherited from chrono::ChLinkBase | |
| ChLinkBase (const ChLinkBase &other) | |
| bool | IsValid () |
| Tells if the link data is currently valid. More... | |
| void | SetValid (bool mon) |
| Set the status of link validity. | |
| bool | IsDisabled () |
| Tells if all constraints of this link are currently turned on or off by the user. | |
| bool | IsBroken () |
| Tells if the link is broken, for excess of pulling/pushing. | |
| virtual bool | IsActive () const override |
| Return true if the link is currently active and thereofre included into the system solver. More... | |
| virtual bool | IsRequiringWaking () |
| Tells if this link requires that the connected ChBody objects must be waken if they are sleeping. More... | |
| Public Member Functions inherited from chrono::ChPhysicsItem | |
| ChPhysicsItem (const ChPhysicsItem &other) | |
| ChSystem * | GetSystem () const |
| Get the pointer to the parent ChSystem(). | |
| virtual void | SetSystem (ChSystem *m_system) |
| Set the pointer to the parent ChSystem(). More... | |
| void | AddVisualModel (std::shared_ptr< ChVisualModel > model) |
| Add an (optional) visualization model. More... | |
| std::shared_ptr< ChVisualModel > | GetVisualModel () const |
| Access the visualization model (if any). More... | |
| void | AddVisualShape (std::shared_ptr< ChVisualShape > shape, const ChFrame<> &frame=ChFrame<>()) |
| Add the specified visual shape to the visualization model. More... | |
| std::shared_ptr< ChVisualShape > | GetVisualShape (unsigned int i) const |
| Access the specified visualization shape in the visualization model (if any). More... | |
| void | AddVisualShapeFEA (std::shared_ptr< ChVisualShapeFEA > shapeFEA) |
| Add the specified FEA visualization object to the visualization model. More... | |
| std::shared_ptr< ChVisualShapeFEA > | GetVisualShapeFEA (unsigned int i) const |
| Access the specified FEA visualization object in the visualization model (if any). More... | |
| virtual unsigned int | GetNumVisualModelClones () const |
| Return the number of clones of the visual model associated with this physics item. More... | |
| void | AddCamera (std::shared_ptr< ChCamera > camera) |
| Attach a ChCamera to this physical item. More... | |
| std::vector< std::shared_ptr< ChCamera > > | GetCameras () const |
| Get the set of cameras attached to this physics item. | |
| virtual bool | IsCollisionEnabled () const |
| Tell if the object is subject to collision. More... | |
| virtual void | AddCollisionModelsToSystem (ChCollisionSystem *coll_sys) const |
| Add to the provided collision system any collision models managed by this physics item. More... | |
| virtual void | RemoveCollisionModelsFromSystem (ChCollisionSystem *coll_sys) const |
| Remove from the provided collision system any collision models managed by this physics item. More... | |
| virtual void | SyncCollisionModels () |
| Synchronize the position and bounding box of any collsion models managed by this physics item. | |
| virtual ChAABB | GetTotalAABB () |
| Get the entire AABB axis-aligned bounding box of the object. More... | |
| virtual void | GetCenter (ChVector3d &mcenter) |
| Get a symbolic 'center' of the object. More... | |
| virtual void | Setup () |
| This might recompute the number of coordinates, DOFs, constraints, in case this might change (ex in ChAssembly), as well as state offsets of contained items (ex in ChMesh) | |
| virtual void | ForceToRest () |
| Set zero speed (and zero accelerations) in state, without changing the position. More... | |
| virtual unsigned int | GetNumCoordsPosLevel () |
| Get the number of coordinates at the position level. More... | |
| virtual unsigned int | GetNumCoordsVelLevel () |
| Get the number of coordinates at the velocity level. More... | |
| unsigned int | GetOffset_x () |
| Get offset in the state vector (position part) | |
| unsigned int | GetOffset_w () |
| Get offset in the state vector (speed part) | |
| unsigned int | GetOffset_L () |
| Get offset in the lagrangian multipliers. | |
| void | SetOffset_x (const unsigned int moff) |
| Set offset in the state vector (position part) Note: only the ChSystem::Setup function should use this. | |
| void | SetOffset_w (const unsigned int moff) |
| Set offset in the state vector (speed part) Note: only the ChSystem::Setup function should use this. | |
| void | SetOffset_L (const unsigned int moff) |
| Set offset in the lagrangian multipliers Note: only the ChSystem::Setup function should use this. | |
| virtual void | IntStateGather (const unsigned int off_x, ChState &x, const unsigned int off_v, ChStateDelta &v, double &T) |
| From item's state to global state vectors y={x,v} pasting the states at the specified offsets. More... | |
| virtual void | IntStateScatter (const unsigned int off_x, const ChState &x, const unsigned int off_v, const ChStateDelta &v, const double T, bool full_update) |
| From global state vectors y={x,v} to item's state (and update) fetching the states at the specified offsets. More... | |
| virtual void | IntStateGatherAcceleration (const unsigned int off_a, ChStateDelta &a) |
| From item's state acceleration to global acceleration vector. More... | |
| virtual void | IntStateScatterAcceleration (const unsigned int off_a, const ChStateDelta &a) |
| From global acceleration vector to item's state acceleration. More... | |
| virtual void | IntStateIncrement (const unsigned int off_x, ChState &x_new, const ChState &x, const unsigned int off_v, const ChStateDelta &Dv) |
| Computes x_new = x + Dt , using vectors at specified offsets. More... | |
| virtual void | IntStateGetIncrement (const unsigned int off_x, const ChState &x_new, const ChState &x, const unsigned int off_v, ChStateDelta &Dv) |
| Computes Dt = x_new - x, using vectors at specified offsets. More... | |
| virtual void | IntLoadResidual_F (const unsigned int off, ChVectorDynamic<> &R, const double c) |
| Takes the F force term, scale and adds to R at given offset: R += c*F. More... | |
| virtual void | IntLoadResidual_Mv (const unsigned int off, ChVectorDynamic<> &R, const ChVectorDynamic<> &w, const double c) |
| Takes the M*v term, multiplying mass by a vector, scale and adds to R at given offset: R += c*M*w. More... | |
| virtual void | IntLoadLumpedMass_Md (const unsigned int off, ChVectorDynamic<> &Md, double &err, const double c) |
| Adds the lumped mass to a Md vector, representing a mass diagonal matrix. More... | |
| virtual void | InjectVariables (ChSystemDescriptor &descriptor) |
| Register with the given system descriptor any ChVariable objects associated with this item. | |
| virtual void | VariablesFbReset () |
| Sets the 'fb' part (the known term) of the encapsulated ChVariables to zero. | |
| virtual void | VariablesFbLoadForces (double factor=1) |
| Adds the current forces (applied to item) into the encapsulated ChVariables, in the 'fb' part: qf+=forces*factor. | |
| virtual void | VariablesQbLoadSpeed () |
| Initialize the 'qb' part of the ChVariables with the current value of speeds. More... | |
| virtual void | VariablesFbIncrementMq () |
| Adds M*q (masses multiplied current 'qb') to Fb, ex. More... | |
| virtual void | VariablesQbSetSpeed (double step=0) |
| Fetches the item speed (ex. More... | |
| virtual void | VariablesQbIncrementPosition (double step) |
| Increment item positions by the 'qb' part of the ChVariables, multiplied by a 'step' factor. More... | |
| virtual void | ConstraintsBiLoad_Qc (double factor=1) |
| Adds the current Qc (the vector of C_dtdt=0 -> [Cq]*q_dtdt=Qc ) to the known term (b_i) of encapsulated ChConstraints. | |
| virtual void | ConstraintsFbLoadForces (double factor=1) |
| Adds the current link-forces, if any, (caused by springs, etc.) to the 'fb' vectors of the ChVariables referenced by encapsulated ChConstraints. | |
| Public Member Functions inherited from chrono::ChObj | |
| ChObj (const ChObj &other) | |
| int | GetIdentifier () const |
| Get the unique integer identifier of this object. More... | |
| void | SetTag (int tag) |
| Set an object integer tag (default: -1). More... | |
| int | GetTag () const |
| Get the tag of this object. | |
| void | SetName (const std::string &myname) |
| Set the name of this object. | |
| const std::string & | GetName () const |
| Get the name of this object. | |
| double | GetChTime () const |
| Gets the simulation time of this object. | |
| void | SetChTime (double m_time) |
| Sets the simulation time of this object. | |
| virtual std::string & | ArchiveContainerName () |
Additional Inherited Members | |
| Public Types inherited from chrono::ChLinkMateGeneric | |
| using | ChConstraintVectorX = Eigen::Matrix< double, Eigen::Dynamic, 1, Eigen::ColMajor, 6, 1 > |
| Protected Member Functions inherited from chrono::ChLinkMateGeneric | |
| void | SetupLinkMask () |
| void | ChangedLinkMask () |
| virtual void | IntStateGatherReactions (const unsigned int off_L, ChVectorDynamic<> &L) override |
| From item's reaction forces to global reaction vector. More... | |
| virtual void | IntStateScatterReactions (const unsigned int off_L, const ChVectorDynamic<> &L) override |
| From global reaction vector to item's reaction forces. More... | |
| virtual void | IntLoadResidual_CqL (const unsigned int off_L, ChVectorDynamic<> &R, const ChVectorDynamic<> &L, const double c) override |
| Takes the term Cq'*L, scale and adds to R at given offset: R += c*Cq'*L. More... | |
| virtual void | IntLoadConstraint_C (const unsigned int off, ChVectorDynamic<> &Qc, const double c, bool do_clamp, double recovery_clamp) override |
| Takes the term C, scale and adds to Qc at given offset: Qc += c*C. More... | |
| virtual void | IntToDescriptor (const unsigned int off_v, const ChStateDelta &v, const ChVectorDynamic<> &R, const unsigned int off_L, const ChVectorDynamic<> &L, const ChVectorDynamic<> &Qc) override |
| Prepare variables and constraints to accommodate a solution: More... | |
| virtual void | IntFromDescriptor (const unsigned int off_v, ChStateDelta &v, const unsigned int off_L, ChVectorDynamic<> &L) override |
| After a solver solution, fetch values from variables and constraints into vectors: More... | |
| virtual void | InjectConstraints (ChSystemDescriptor &descriptor) override |
| Register with the given system descriptor any ChConstraint objects associated with this item. | |
| virtual void | ConstraintsBiReset () override |
| Sets to zero the known term (b_i) of encapsulated ChConstraints. | |
| virtual void | ConstraintsBiLoad_C (double factor=1, double recovery_clamp=0.1, bool do_clamp=false) override |
| Adds the current C (constraint violation) to the known term (b_i) of encapsulated ChConstraints. | |
| virtual void | LoadConstraintJacobians () override |
| Compute and load current Jacobians in encapsulated ChConstraint objects. | |
| virtual void | ConstraintsFetch_react (double factor=1) override |
| Fetches the reactions from the lagrangian multiplier (l_i) of encapsulated ChConstraints. More... | |
| virtual void | InjectKRMMatrices (ChSystemDescriptor &descriptor) override |
| Register with the given system descriptor any ChKRMBlock objects associated with this item. | |
| Protected Member Functions inherited from chrono::ChObj | |
| int | GenerateUniqueIdentifier () |
| Protected Attributes inherited from chrono::ChLinkMateGeneric | |
| ChFrame | frame1 |
| ChFrame | frame2 |
| bool | c_x |
| bool | c_y |
| bool | c_z |
| bool | c_rx |
| bool | c_ry |
| bool | c_rz |
| int | m_num_constr |
| number of constraints | |
| int | m_num_constr_bil |
| number of bilateral constraints | |
| int | m_num_constr_uni |
| number of unilateral constraints | |
| ChLinkMask | mask |
| ChConstraintVectorX | C |
| residuals | |
| ChMatrix33 | P |
| projection matrix from Lagrange multiplier to reaction torque | |
| ChVector3d | gamma_f |
| translational Lagrange multipliers | |
| ChVector3d | gamma_m |
| rotational Lagrange multipliers | |
| std::unique_ptr< ChKRMBlock > | Kmatr = nullptr |
| the tangent stiffness matrix of constraint | |
| Protected Attributes inherited from chrono::ChLink | |
| ChBodyFrame * | m_body1 |
| first connected body | |
| ChBodyFrame * | m_body2 |
| second connected body | |
| ChVector3d | react_force |
| xyz reactions, expressed in local coordinate system of link; | |
| ChVector3d | react_torque |
| torque reactions, expressed in local coordinate system of link; | |
| Protected Attributes inherited from chrono::ChLinkBase | |
| bool | disabled |
| all constraints of link disabled because of user needs | |
| bool | valid |
| link data is valid | |
| bool | broken |
| link is broken because of excessive pulling/pushing. | |
| Protected Attributes inherited from chrono::ChPhysicsItem | |
| ChSystem * | system |
| parent system | |
| std::shared_ptr< ChVisualModelInstance > | vis_model_instance |
| instantiated visualization model | |
| std::vector< std::shared_ptr< ChCamera > > | cameras |
| set of cameras | |
| unsigned int | offset_x |
| offset in vector of state (position part) | |
| unsigned int | offset_w |
| offset in vector of state (speed part) | |
| unsigned int | offset_L |
| offset in vector of lagrangian multipliers | |
| Protected Attributes inherited from chrono::ChObj | |
| double | ChTime |
| object simulation time | |
| std::string | m_name |
| object name | |
| int | m_identifier |
| object unique identifier | |
| int | m_tag |
| user-supplied tag | |
Member Function Documentation
◆ ArchiveIn()
|
overridevirtual |
Method to allow deserialization of transient data from archives.
Method to allow de serialization of transient data from archives.
Reimplemented from chrono::ChLinkMateGeneric.
◆ LoadKRMMatrices()
|
overridevirtual |
Add the current stiffness K matrix in encapsulated ChKRMBlock item(s), if any.
The K matrix is loaded with scaling value Kfactor.
Reimplemented from chrono::ChLinkMateGeneric.
◆ SetPositionFunction()
|
inline |
Set the position function for a generic 3D rotation, as p=p(t) vector function.
Use an object from one of the ChFunctionPosition inherited classes to this end. This function should be C0 continuous and, to prevent acceleration spikes, it should ideally be C1 continuous. The position is imposed to frame1 respect to frame2, in frame2 coordinate system.
◆ SetRotationFunction()
|
inline |
Set the rotation function for a generic 3D rotation, as q=q(t) quaternion rotation function.
Use an object from one of the ChFunctionRotation inherited classes to this end. This function should be C0 continuous and, to prevent acceleration spikes, it should ideally be C1 continuous. The position is imposed to frame1 respect to frame2, in frame2 coordinate system.
The documentation for this class was generated from the following files:
- /builds/uwsbel/chrono/src/chrono/physics/ChLinkMotionImposed.h
- /builds/uwsbel/chrono/src/chrono/physics/ChLinkMotionImposed.cpp
