A single axis hinge joint. More...

#include <SimbodyHingeJoint.hh>

Public Types
enum	Attribute { FUDGE_FACTOR, SUSPENSION_ERP, SUSPENSION_CFM, STOP_ERP, STOP_CFM, ERP, CFM, FMAX, VEL, HI_STOP, LO_STOP }
	Joint attribute types. More...

enum	EntityType { BASE = 0x00000000, ENTITY = 0x00000001, MODEL = 0x00000002, LINK = 0x00000004, COLLISION = 0x00000008, LIGHT = 0x00000010, VISUAL = 0x00000020, JOINT = 0x00000040, BALL_JOINT = 0x00000080, HINGE2_JOINT = 0x00000100, HINGE_JOINT = 0x00000200, SLIDER_JOINT = 0x00000400, SCREW_JOINT = 0x00000800, UNIVERSAL_JOINT = 0x00001000, GEARBOX_JOINT = 0x00002000, FIXED_JOINT = 0x00004000, ACTOR = 0x00008000, SHAPE = 0x00010000, BOX_SHAPE = 0x00020000, CYLINDER_SHAPE = 0x00040000, HEIGHTMAP_SHAPE = 0x00080000, MAP_SHAPE = 0x00100000, MULTIRAY_SHAPE = 0x00200000, RAY_SHAPE = 0x00400000, PLANE_SHAPE = 0x00800000, SPHERE_SHAPE = 0x01000000, MESH_SHAPE = 0x02000000, POLYLINE_SHAPE = 0x04000000, SENSOR_COLLISION = 0x10000000 }
	Unique identifiers for all entity types. More...

Public Member Functions
	SimbodyHingeJoint (SimTK::MultibodySystem *world, BasePtr _parent)
	Constructor. More...

virtual	~SimbodyHingeJoint ()
	Destructor. More...

void	AddChild (BasePtr _child)
	Add a child to this entity. More...

void	AddType (EntityType _type)
	Add a type specifier. More...

virtual ignition::math::Vector3d	Anchor (const unsigned int _index) const
	Get the anchor point. More...

ignition::math::Pose3d	AnchorErrorPose () const
	Get pose offset between anchor pose on child and parent, expressed in the parent link frame. More...

virtual void	ApplyStiffnessDamping ()
	Callback to apply spring stiffness and viscous damping effects to joint. More...

virtual bool	AreConnected (LinkPtr _one, LinkPtr _two) const
	Determines of the two bodies are connected by a joint. More...

virtual void	Attach (LinkPtr _parent, LinkPtr _child)
	Attach the two bodies with this joint. More...

ignition::math::Quaterniond	AxisFrame (const unsigned int _index) const
	Get orientation of reference frame for specified axis, relative to world frame. More...

ignition::math::Quaterniond	AxisFrameOffset (const unsigned int _index) const
	Get orientation of joint axis reference frame relative to joint frame. More...

virtual void	CacheForceTorque ()
	Cache Joint Force Torque Values if necessary for physics engine. More...

double	CheckAndTruncateForce (unsigned int _index, double _effort)
	check if the force against velocityLimit and effortLimit, truncate if necessary. More...

template<typename T >
event::ConnectionPtr	ConnectJointUpdate (T _subscriber)
	Connect a boost::slot the the joint update signal. More...

virtual void	Detach ()
	Detach this joint from all links. More...

virtual unsigned int	DOF () const

virtual void	FillMsg (msgs::Joint &_msg)
	Fill a joint message. More...

virtual void	Fini ()
	Finialize the object. More...

BasePtr	GetByName (const std::string &_name)
	Get by name. More...

BasePtr	GetChild (unsigned int _i) const
	Get a child by index. More...

BasePtr	GetChild (const std::string &_name)
	Get a child by name. More...

LinkPtr	GetChild () const
	Get the child link. More...

unsigned int	GetChildCount () const
	Get the number of children. More...

double	GetDamping (unsigned int _index)
	Returns the current joint damping coefficient. More...

virtual double	GetEffortLimit (unsigned int _index)
	Get the effort limit on axis(index). More...

virtual double	GetForce (unsigned int _index)

virtual JointWrench	GetForceTorque (unsigned int _index)
	get internal force and torque values at a joint. More...

uint32_t	GetId () const
	Return the ID of this entity. More...

double	GetInertiaRatio (const unsigned int _index) const
	Computes moment of inertia (MOI) across a specified joint axis. More...

virtual LinkPtr	GetJointLink (unsigned int _index) const
	Get the link to which the joint is attached according the _index. More...

msgs::Joint::Type	GetMsgType () const
	Get the joint type as msgs::Joint::Type. More...

std::string	GetName () const
	Return the name of the entity. More...

virtual double	GetParam (const std::string &_key, unsigned int _index)
	Get a non-generic parameter for the joint. More...

LinkPtr	GetParent () const
	Get the parent link. More...

int	GetParentId () const
	Return the ID of the parent. More...

bool	GetSaveable () const
	Get whether the object should be "saved", when the user selects to save the world to xml. More...

std::string	GetScopedName (bool _prependWorldName=false) const
	Return the name of this entity with the model scope model1::...::modelN::entityName. More...

virtual const sdf::ElementPtr	GetSDF ()
	Get the SDF values for the object. More...

double	GetSpringReferencePosition (unsigned int _index) const
	Get joint spring reference position. More...

double	GetStiffness (unsigned int _index)
	Returns the current joint spring stiffness coefficient. More...

double	GetStopDissipation (unsigned int _index) const
	Get joint stop dissipation. More...

double	GetStopStiffness (unsigned int _index) const
	Get joint stop stiffness. More...

unsigned int	GetType () const
	Get the full type definition. More...

virtual double	GetVelocity (unsigned int _index) const
	Get the rotation rate of an axis(index) More...

virtual double	GetVelocityLimit (unsigned int _index)
	Get the velocity limit on axis(index). More...

const WorldPtr &	GetWorld () const
	Get the World this object is in. More...

double	GetWorldEnergyPotentialSpring (unsigned int _index) const
	Returns this joint's spring potential energy, based on the reference position of the spring. More...

virtual ignition::math::Vector3d	GlobalAxis (const unsigned int _index) const
	Get the axis of rotation in global cooridnate frame. More...

bool	HasType (const EntityType &_t) const
	Returns true if this object's type definition has the given type. More...

double	InertiaRatio (const ignition::math::Vector3d &_axis) const
	Computes moment of inertia (MOI) across an arbitrary axis specified in the world frame. More...

ignition::math::Pose3d	InitialAnchorPose () const
	Get initial Anchor Pose specified by model <joint><pose>...</pose></joint> More...

bool	IsSelected () const
	True if the entity is selected by the user. More...

virtual ignition::math::Vector3d	LinkForce (const unsigned int _index) const
	Get the forces applied to the center of mass of a physics::Link due to the existence of this Joint. More...

virtual ignition::math::Vector3d	LinkTorque (const unsigned int _index) const
	Get the torque applied to the center of mass of a physics::Link due to the existence of this Joint. More...

void	Load (LinkPtr _parent, LinkPtr _child, const ignition::math::Pose3d &_pose)
	Set pose, parent and child links of a physics::Joint. More...

ignition::math::Vector3d	LocalAxis (const unsigned int _index) const
	Get the axis of rotation. More...

virtual double	LowerLimit (const unsigned int _index) const
	Get the joint's lower limit. More...

bool	operator== (const Base &_ent) const
	Returns true if the entities are the same. More...

ignition::math::Pose3d	ParentWorldPose () const
	Get anchor pose on parent link relative to world frame. More...

virtual double	Position (const unsigned int _index=0) const final
	Get the position of an axis according to its index. More...

void	Print (const std::string &_prefix)
	Print this object to screen via gzmsg. More...

virtual void	RemoveChild (unsigned int _id)
	Remove a child from this entity. More...

void	RemoveChild (const std::string &_name)
	Remove a child by name. More...

void	RemoveChild (physics::BasePtr _child)
	Remove a child by pointer. More...

void	RemoveChildren ()
	Remove all children. More...

virtual void	Reset ()
	Reset the joint. More...

virtual void	Reset (Base::EntityType _resetType)
	Calls recursive Reset on one of the Base::EntityType's. More...

virtual void	RestoreSimbodyState (SimTK::State &_state)
	restore simbody state for spawning More...

virtual void	SaveSimbodyState (const SimTK::State &_state)
	save simbody state for spawning More...

virtual void	SetAnchor (const unsigned int _index, const ignition::math::Vector3d &_anchor)
	Set the anchor point. More...

void	SetAxis (const unsigned int _index, const ignition::math::Vector3d &_axis)
	Set the axis of rotation where axis is specified in local joint frame. More...

virtual void	SetDamping (unsigned int _index, const double _damping)
	Set the joint damping. More...

virtual void	SetEffortLimit (unsigned int _index, double _effort)
	Set the effort limit on a joint axis. More...

virtual void	SetForce (unsigned int _index, double _force)
	Set the force applied to this physics::Joint. More...

virtual void	SetLowerLimit (const unsigned int _index, const double _limit)
	Set the joint's lower limit. More...

void	SetModel (ModelPtr _model)
	Set the model this joint belongs too. More...

virtual void	SetName (const std::string &_name)
	Set the name of the entity. More...

virtual bool	SetParam (const std::string &_key, unsigned int _index, const boost::any &_value)
	Set a non-generic parameter for the joint. More...

void	SetParent (BasePtr _parent)
	Set the parent. More...

virtual bool	SetPosition (const unsigned int _index, const double _position, const bool _preserveWorldVelocity=false) override
	The child links of this joint are updated based on desired position. More...

virtual void	SetProvideFeedback (bool _enable)
	Set whether the joint should generate feedback. More...

void	SetSaveable (bool _v)
	Set whether the object should be "saved", when the user selects to save the world to xml. More...

virtual bool	SetSelected (bool _show)
	Set whether this entity has been selected by the user through the gui. More...

void	SetState (const JointState &_state)
	Set the joint state. More...

virtual void	SetStiffness (unsigned int _index, const double _stiffness)
	Set the joint spring stiffness. More...

virtual void	SetStiffnessDamping (unsigned int _index, double _stiffness, double _damping, double _reference=0)
	Set the joint spring stiffness. More...

void	SetStopDissipation (unsigned int _index, double _dissipation)
	Set joint stop dissipation. More...

void	SetStopStiffness (unsigned int _index, double _stiffness)
	Set joint stop stiffness. More...

virtual void	SetUpperLimit (const unsigned int _index, const double _limit)
	Set the joint's upper limit. More...

virtual void	SetVelocity (unsigned int _index, double _rate)
	Set the velocity of an axis(index). More...

virtual void	SetVelocityLimit (unsigned int _index, double _velocity)
	Set the velocity limit on a joint axis. More...

void	SetWorld (const WorldPtr &_newWorld)
	Set the world this object belongs to. More...

std::string	TypeStr () const
	Get the string name for the entity type. More...

void	Update ()
	Update the joint. More...

virtual void	UpdateParameters (sdf::ElementPtr _sdf)
	Update the parameters using new sdf values. More...

virtual double	UpperLimit (const unsigned int _index) const
	Get the joint's upper limit. More...

common::URI	URI () const
	Return the common::URI of this entity. More...

ignition::math::Pose3d	WorldPose () const
	Get pose of joint frame relative to world frame. More...

Public Attributes
SimTK::Constraint	constraint
	: isValid() if we used a constraint to model this joint. More...

SimTK::Force::MobilityLinearDamper	damper [MAX_JOINT_AXIS]
	: for enforcing joint damping forces. More...

SimTK::Transform	defxAB
	default mobilizer pose More...

bool	isReversed
	: if mobilizer, did it reverse parent&child? Set when we build the Simbody model. More...

SimTK::Force::MobilityLinearStop	limitForce [MAX_JOINT_AXIS]
	: for enforcing joint stops Set when we build the Simbody model. More...

SimTK::MobilizedBody	mobod
	Use isValid() if we used a mobilizer Set when we build the Simbody model. More...

bool	mustBreakLoopHere
	Force Simbody to break a loop by using a weld constraint. More...

bool	physicsInitialized

SimTK::Force::MobilityLinearSpring	spring [MAX_JOINT_AXIS]
	: Spring force element for enforcing joint stiffness. More...

SimTK::Transform	xCB
	child body frame to mobilizer frame More...

SimTK::Transform	xPA
	Normally A=F, B=M. More...

Protected Member Functions
ignition::math::Pose3d	ChildLinkPose (const unsigned int _index, const double _position)
	internal function to help us compute child link pose if a joint position change is applied. More...

void	ComputeScopedName ()
	Compute the scoped name of this object based on its parents. More...

bool	FindAllConnectedLinks (const LinkPtr &_originalParentLink, Link_V &_connectedLinks)
	internal helper to find all links connected to the child link branching out from the children of the child link and any parent of the child link other than the parent link through this joint. More...

virtual void	Init ()
	Initialize joint. More...

virtual void	Load (sdf::ElementPtr _sdf)
	Load joint. More...

virtual double	PositionImpl (const unsigned int _index) const
	Helper function to get the position of an axis. More...

virtual void	RegisterIntrospectionItems ()
	Register items in the introspection service. More...

virtual void	SetForceImpl (unsigned int _index, double _torque)
	Set the force applied to this physics::Joint. More...

bool	SetPositionMaximal (const unsigned int _index, double _position, const bool _preserveWorldVelocity=false)
	Helper function for maximal coordinate solver SetPosition. More...

bool	SetVelocityMaximal (unsigned int _index, double _velocity)
	Helper function for maximal coordinate solver SetVelocity. More...

virtual void	UnregisterIntrospectionItems ()
	Unregister items in the introspection service. More...

Protected Attributes
LinkPtr	anchorLink
	Anchor link. More...

ignition::math::Vector3d	anchorPos
	Anchor pose. More...

ignition::math::Pose3d	anchorPose
	Anchor pose specified in SDF <joint><pose> tag. More...

gazebo::event::ConnectionPtr	applyDamping
	apply damping for adding viscous damping forces on updates More...

bool	axisParentModelFrame [2]
	Flags that are set to true if an axis value is expressed in the parent model frame. More...

LinkPtr	childLink
	The first link this joint connects to. More...

Base_V	children
	Children of this entity. More...

double	dissipationCoefficient [2]
	joint viscous damping coefficient More...

double	effortLimit [2]
	Store Joint effort limit as specified in SDF. More...

std::vector< common::URI >	introspectionItems
	All the introspection items regsitered for this. More...

double	lowerLimit [2]
	Store Joint position lower limit as specified in SDF. More...

ModelPtr	model
	Pointer to the parent model. More...

BasePtr	parent
	Parent of this entity. More...

ignition::math::Pose3d	parentAnchorPose
	Anchor pose relative to parent link frame. More...

LinkPtr	parentLink
	The second link this joint connects to. More...

bool	provideFeedback
	Provide Feedback data for contact forces. More...

sdf::ElementPtr	sdf
	The SDF values for this object. More...

SimbodyPhysicsPtr	simbodyPhysics
	keep a pointer to the simbody physics engine for convenience More...

double	springReferencePosition [2]
	joint spring reference (zero load) position More...

double	stiffnessCoefficient [2]
	joint stiffnessCoefficient More...

double	upperLimit [2]
	Store Joint position upper limit as specified in SDF. More...

double	velocityLimit [2]
	Store Joint velocity limit as specified in SDF. More...

SimTK::MultibodySystem *	world
	Simbody Multibody System. More...

JointWrench	wrench
	Cache Joint force torque values in case physics engine clears them at the end of update step. More...

Detailed Description

A single axis hinge joint.

Member Enumeration Documentation

enum Attribute

inherited

Joint attribute types.

Enumerator
FUDGE_FACTOR	Fudge factor.
SUSPENSION_ERP	Suspension error reduction parameter.
SUSPENSION_CFM	Suspension constraint force mixing.
STOP_ERP	Stop limit error reduction parameter.
STOP_CFM	Stop limit constraint force mixing.
ERP	Error reduction parameter.
CFM	Constraint force mixing.
FMAX	Maximum force.
VEL	Velocity.
HI_STOP	Upper joint limit.
LO_STOP	Lower joint limit.

enum EntityType

inherited

Unique identifiers for all entity types.

Enumerator
BASE	Base type.
ENTITY	Entity type.
MODEL	Model type.
LINK	Link type.
COLLISION	Collision type.
LIGHT	Light type.
VISUAL	Visual type.
JOINT	Joint type.
BALL_JOINT	BallJoint type.
HINGE2_JOINT	Hing2Joint type.
HINGE_JOINT	HingeJoint type.
SLIDER_JOINT	SliderJoint type.
SCREW_JOINT	ScrewJoint type.
UNIVERSAL_JOINT	UniversalJoint type.
GEARBOX_JOINT	GearboxJoint type.
FIXED_JOINT	FixedJoint type.
ACTOR	Actor type.
SHAPE	Shape type.
BOX_SHAPE	BoxShape type.
CYLINDER_SHAPE	CylinderShape type.
HEIGHTMAP_SHAPE	HeightmapShape type.
MAP_SHAPE	MapShape type.
MULTIRAY_SHAPE	MultiRayShape type.
RAY_SHAPE	RayShape type.
PLANE_SHAPE	PlaneShape type.
SPHERE_SHAPE	SphereShape type.
MESH_SHAPE	MeshShape type.
POLYLINE_SHAPE	PolylineShape type.
SENSOR_COLLISION	Indicates a collision shape used for sensing.

Constructor & Destructor Documentation

SimbodyHingeJoint	(	SimTK::MultibodySystem *	world,
		BasePtr	_parent
	)

Constructor.

virtual ~SimbodyHingeJoint ( )

virtual

Destructor.

Member Function Documentation

void AddChild ( BasePtr _child )

inherited

Add a child to this entity.

Parameters

[in] _child Child entity.

void AddType ( EntityType _type )

inherited

Add a type specifier.

Parameters

[in] _type New type to append to this objects type definition.

virtual ignition::math::Vector3d Anchor ( const unsigned int _index ) const

virtualinherited

Get the anchor point.

Parameters

[in] _index Index of the axis.

Returns: Anchor value for the axis.

Implements Joint.

Reimplemented in SimbodyUniversalJoint, SimbodyHinge2Joint, and SimbodyBallJoint.

ignition::math::Pose3d AnchorErrorPose ( ) const

inherited

Get pose offset between anchor pose on child and parent, expressed in the parent link frame.

This can be used to compute the bilateral constraint error.

Returns: Pose offset between anchor pose on child and parent, in parent link frame.

virtual void ApplyStiffnessDamping ( )

virtualinherited

Callback to apply spring stiffness and viscous damping effects to joint.

: rename to ApplySpringStiffnessDamping()

Reimplemented in ODEJoint, and BulletJoint.

virtual bool AreConnected	(	LinkPtr	_one,
		LinkPtr	_two
	)		const

virtualinherited

Determines of the two bodies are connected by a joint.

Parameters

[in]	_one	First link.
[in]	_two	Second link.

Returns: True if the two links are connected by a joint.

Implements Joint.

virtual void Attach	(	LinkPtr	_parent,
		LinkPtr	_child
	)

virtualinherited

Attach the two bodies with this joint.

Parameters

[in]	_parent	Parent link.
[in]	_child	Child link.

Reimplemented in ODEJoint, ODEFixedJoint, and DARTJoint.

ignition::math::Quaterniond AxisFrame ( const unsigned int _index ) const

inherited

Get orientation of reference frame for specified axis, relative to world frame.

The value of axisParentModelFrame is used to determine the appropriate frame.

Parameters

[in] _index joint axis index.

Returns: Orientation of axis frame relative to world frame.

ignition::math::Quaterniond AxisFrameOffset ( const unsigned int _index ) const

inherited

Get orientation of joint axis reference frame relative to joint frame.

This should always return identity unless flag use_parent_model_frame is true in sdf 1.5 or using sdf 1.4-, i.e. bug described in issue #494 is present. In addition, if use_parent_model_frame is true, and the parent link of the joint is world, the axis is defined in the world frame. The value of axisParentModelFrame is used to determine the appropriate frame internally.

Parameters

[in] _index joint axis index.

Returns: Orientation of axis frame relative to joint frame. If supplied _index is out of range, or use_parent_model_frame is not true, this function returns identity rotation quaternion.

virtual void CacheForceTorque ( )

virtualinherited

Cache Joint Force Torque Values if necessary for physics engine.

Reimplemented from Joint.

double CheckAndTruncateForce	(	unsigned int	_index,
		double	_effort
	)

inherited

check if the force against velocityLimit and effortLimit, truncate if necessary.

Parameters

[in]	_index	Index of the axis.
[in]	_effort	Force value.

Returns: truncated effort

ignition::math::Pose3d ChildLinkPose	(	const unsigned int	_index,
		const double	_position
	)

protectedinherited

internal function to help us compute child link pose if a joint position change is applied.

Parameters

[in]	_index	axis index
[in]	_position	new joint position

Returns: new child link pose at new joint position.

void ComputeScopedName ( )

protectedinherited

Compute the scoped name of this object based on its parents.

See Also: Base::GetScopedName

event::ConnectionPtr ConnectJointUpdate ( T _subscriber )

inlineinherited

Connect a boost::slot the the joint update signal.

Parameters

[in] _subscriber Callback for the connection.

Returns: Connection pointer, which must be kept in scope.

References EventT< T >::Connect().

virtual void Detach ( )

virtualinherited

Detach this joint from all links.

Reimplemented from Joint.

virtual unsigned int DOF ( ) const

inlinevirtualinherited

Implements Joint.

virtual void FillMsg ( msgs::Joint & _msg )

virtualinherited

Fill a joint message.

Parameters

[out] _msg Message to fill with this joint's properties.

Reimplemented in GearboxJoint< ODEJoint >, ScrewJoint< ODEJoint >, ScrewJoint< DARTJoint >, ScrewJoint< SimbodyJoint >, and ScrewJoint< BulletJoint >.

Referenced by ScrewJoint< BulletJoint >::FillMsg(), and GearboxJoint< ODEJoint >::FillMsg().

bool FindAllConnectedLinks	(	const LinkPtr &	_originalParentLink,
		Link_V &	_connectedLinks
	)

protectedinherited

internal helper to find all links connected to the child link branching out from the children of the child link and any parent of the child link other than the parent link through this joint.

Parameters

[in]	_originalParentLink	parent link of this joint, this is used to check for loops connecting back to the parent link.
	in/out]	_connectedLinks list of aggregated links that contains all links connected to the child link of this joint. Empty if a loop is found that connects back to the parent link.

Returns: true if successful, false if a loop is found that connects back to the parent link.

virtual void Fini ( )

virtualinherited

Finialize the object.

Reimplemented from Base.

Reimplemented in ODEJoint, and BulletJoint.

BasePtr GetByName ( const std::string & _name )

inherited

Get by name.

Parameters

[in] _name Get a child (or self) object by name

Returns: A pointer to the object, NULL if not found

BasePtr GetChild ( unsigned int _i ) const

inherited

Get a child by index.

Parameters

[in] _i Index of the child to retreive.

Returns: A pointer to the object, NULL if the index is invalid.

BasePtr GetChild ( const std::string & _name )

inherited

Get a child by name.

Parameters

[in] _name Name of the child.

Returns: A pointer to the object, NULL if not found

LinkPtr GetChild ( ) const

inherited

Get the child link.

Returns: Pointer to the child link.

unsigned int GetChildCount ( ) const

inherited

Get the number of children.

Returns: The number of children.

double GetDamping ( unsigned int _index )

inherited

Returns the current joint damping coefficient.

Parameters

[in] _index Index of the axis to get, currently ignored, to be implemented.

Returns: Joint viscous damping coefficient for this joint.

virtual double GetEffortLimit ( unsigned int _index )

virtualinherited

Get the effort limit on axis(index).

Parameters

[in] _index Index of axis, where 0=first axis and 1=second axis

Returns: Effort limit specified in SDF

virtual double GetForce ( unsigned int _index )

virtualinherited

Todo:

: not yet implemented. Get external forces applied at this Joint. Note that the unit of force should be consistent with the rest of the simulation scales.

Parameters

[in] _index Index of the axis.

Returns: The force applied to an axis.

Reimplemented from Joint.

virtual JointWrench GetForceTorque ( unsigned int _index )

virtualinherited

get internal force and torque values at a joint.

The force and torque values are returned in a JointWrench data structure. Where JointWrench.body1Force contains the force applied by the parent Link on the Joint specified in the parent Link frame, and JointWrench.body2Force contains the force applied by the child Link on the Joint specified in the child Link frame. Note that this sign convention is opposite of the reaction forces of the Joint on the Links.

FIXME TODO: change name of this function to something like: GetNegatedForceTorqueInLinkFrame and make GetForceTorque call return non-negated reaction forces in perspective Link frames.

Note that for ODE you must set <provide_feedback>true<provide_feedback> in the joint sdf to use this.

Parameters

[in] _index Not used right now

Returns: The force and torque at the joint, see above for details on conventions.

Implements Joint.

uint32_t GetId ( ) const

inherited

Return the ID of this entity.

This id is unique.

Returns: Integer ID.

double GetInertiaRatio ( const unsigned int _index ) const

inherited

Computes moment of inertia (MOI) across a specified joint axis.

The ratio is given in the form of MOI_child / MOI_parent. If MOI_parent is zero, this funciton will return 0. The inertia ratio for each joint axis indicates the sensitivity of the joint to actuation torques.

Parameters

[in] _index axis number about which MOI ratio is computed.

Returns: ratio of child MOI to parent MOI.

virtual LinkPtr GetJointLink ( unsigned int _index ) const

virtualinherited

Get the link to which the joint is attached according the _index.

Parameters

[in] _index Index of the link to retreive.

Returns: Pointer to the request link. NULL if the index was invalid.

Implements Joint.

msgs::Joint::Type GetMsgType ( ) const

inherited

Get the joint type as msgs::Joint::Type.

Returns: Joint type.

std::string GetName ( ) const

inherited

Return the name of the entity.

Returns: Name of the entity.

virtual double GetParam	(	const std::string &	_key,
		unsigned int	_index
	)

virtualinherited

Get a non-generic parameter for the joint.

See Also: SetParam(const std::string &, unsigned int, const boost::any)

Parameters

[in]	_key	String key.
[in]	_index	Index of the axis.

Reimplemented from Joint.

Reimplemented in SimbodyScrewJoint.

LinkPtr GetParent ( ) const

inherited

Get the parent link.

Returns: Pointer to the parent link.

int GetParentId ( ) const

inherited

Return the ID of the parent.

Returns: Integer ID.

bool GetSaveable ( ) const

inherited

Get whether the object should be "saved", when the user selects to save the world to xml.

Returns: True if the object is saveable.

std::string GetScopedName ( bool _prependWorldName = false ) const

inherited

Return the name of this entity with the model scope model1::...::modelN::entityName.

Parameters

[in] _prependWorldName True to prended the returned string with the world name. The result will be world::model1::...::modelN::entityName.

Returns: The scoped name.

virtual const sdf::ElementPtr GetSDF ( )

virtualinherited

Get the SDF values for the object.

Returns: The SDF values for the object.

Reimplemented in Actor, and Model.

double GetSpringReferencePosition ( unsigned int _index ) const

inherited

Get joint spring reference position.

Parameters

[in] _index Index of the axis to get.

Returns: Joint spring reference position (in radians for angular joints).

double GetStiffness ( unsigned int _index )

inherited

Returns the current joint spring stiffness coefficient.

Parameters

[in] _index Index of the axis to get, currently ignored, to be implemented.

Returns: Joint spring stiffness coefficient for this joint. : rename to GetSpringStiffness()

double GetStopDissipation ( unsigned int _index ) const

inherited

Get joint stop dissipation.

Parameters

[in] _index joint axis index.

Returns: joint stop dissipation coefficient.

double GetStopStiffness ( unsigned int _index ) const

inherited

Get joint stop stiffness.

Parameters

[in] _index joint axis index.

Returns: joint stop stiffness coefficient.

unsigned int GetType ( ) const

inherited

Get the full type definition.

Returns: The full type definition.

virtual double GetVelocity ( unsigned int _index ) const

virtual

Get the rotation rate of an axis(index)

Parameters

[in] _index Index of the axis.

Returns: The rotaional velocity of the joint axis.

Implements Joint.

virtual double GetVelocityLimit ( unsigned int _index )

virtualinherited

Get the velocity limit on axis(index).

Parameters

[in] _index Index of axis, where 0=first axis and 1=second axis

Returns: Velocity limit specified in SDF

const WorldPtr& GetWorld ( ) const

inherited

Get the World this object is in.

Returns: The World this object is part of.

double GetWorldEnergyPotentialSpring ( unsigned int _index ) const

inherited

Returns this joint's spring potential energy, based on the reference position of the spring.

If using metric system, the unit of energy will be Joules.

Returns: this joint's spring potential energy,

virtual ignition::math::Vector3d GlobalAxis ( const unsigned int _index ) const

virtual

Get the axis of rotation in global cooridnate frame.

Parameters

[in] _index Index of the axis to get.

Returns: Axis value for the provided index.

Implements Joint.

bool HasType ( const EntityType & _t ) const

inherited

Returns true if this object's type definition has the given type.

Parameters

[in] _t Type to check.

Returns: True if this object's type definition has the.

double InertiaRatio ( const ignition::math::Vector3d & _axis ) const

inherited

Computes moment of inertia (MOI) across an arbitrary axis specified in the world frame.

The ratio is given in the form of MOI_chidl / MOI_parent. If MOI_parent is zero, this funciton will return 0. The moment of inertia ratio along constrained directions of a joint has an impact on the performance of Projected Gauss Seidel (PGS) iterative LCP methods.

Parameters

[in] _axis axis in world frame for which MOI ratio is computed.

Returns: ratio of child MOI to parent MOI.

virtual void Init ( )

inlineprotectedvirtualinherited

Initialize joint.

Reimplemented from Joint.

ignition::math::Pose3d InitialAnchorPose ( ) const

inherited

Get initial Anchor Pose specified by model <joint><pose>...</pose></joint>

Returns: Joint::anchorPose, initial joint anchor pose.

bool IsSelected ( ) const

inherited

True if the entity is selected by the user.

Returns: True if the entity is selected.

virtual ignition::math::Vector3d LinkForce ( const unsigned int _index ) const

virtualinherited

Get the forces applied to the center of mass of a physics::Link due to the existence of this Joint.

Note that the unit of force should be consistent with the rest of the simulation scales.

Parameters

[in] index The index of the link(0 or 1).

Returns: Force applied to the link.

Implements Joint.

virtual ignition::math::Vector3d LinkTorque ( const unsigned int _index ) const

virtualinherited

Get the torque applied to the center of mass of a physics::Link due to the existence of this Joint.

Note that the unit of torque should be consistent with the rest of the simulation scales.

Parameters

[in] index The index of the link(0 or 1)

Returns: Torque applied to the link.

Implements Joint.

virtual void Load ( sdf::ElementPtr _sdf )

protectedvirtual

Load joint.

Parameters

[in] _sdf Pointer to SDF element

Reimplemented from HingeJoint< SimbodyJoint >.

void Load	(	LinkPtr	_parent,
		LinkPtr	_child,
		const ignition::math::Pose3d &	_pose
	)

inherited

Set pose, parent and child links of a physics::Joint.

Parameters

[in]	_parent	Parent link.
[in]	_child	Child link.
[in]	_pose	Pose containing Joint Anchor offset from child link.

ignition::math::Vector3d LocalAxis ( const unsigned int _index ) const

inherited

Get the axis of rotation.

Parameters

[in] _index Index of the axis to get.

Returns: Axis value for the provided index.

virtual double LowerLimit ( const unsigned int _index ) const

virtualinherited

Get the joint's lower limit.

For rotational axes, the value is in radians, for prismatic axes it is in meters.

Parameters

[in] _index Index of the axis, defaults to 0.

Returns: Lower limit of the axis.

Reimplemented from Joint.

Reimplemented in SimbodyBallJoint, and SimbodyScrewJoint.

bool operator== ( const Base & _ent ) const

inherited

Returns true if the entities are the same.

Checks only the name.

Parameters

[in] _ent Base object to compare with.

Returns: True if the entities are the same.

ignition::math::Pose3d ParentWorldPose ( ) const

inherited

Get anchor pose on parent link relative to world frame.

When there is zero joint error, this should match the value returned by Joint::WorldPose() for the constrained degrees of freedom.

Returns: Anchor pose on parent link in world frame.

virtual double Position ( const unsigned int _index = 0 ) const

finalvirtualinherited

Get the position of an axis according to its index.

For rotational axes, the value is in radians. For prismatic axes, it is in meters.

For static models, it returns the static joint position.

It returns ignition::math::NAN_D in case the position can't be obtained. For instance, if the index is invalid, if the joint is fixed, etc.

Subclasses can't override this method. See PositionImpl instead.

Parameters

[in] _index Index of the axis, defaults to 0.

Returns: Current position of the axis.

See Also: PositionImpl

virtual double PositionImpl ( const unsigned int _index ) const

protectedvirtual

Helper function to get the position of an axis.

Subclasses must override this.

Parameters

[in] _index Index of the axis, defaults to 0.

Returns: Position of the axis.

See Also: Position

Implements Joint.

void Print ( const std::string & _prefix )

inherited

Print this object to screen via gzmsg.

Parameters

[in] _prefix Usually a set of spaces.

virtual void RegisterIntrospectionItems ( )

protectedvirtualinherited

Register items in the introspection service.

Reimplemented from Base.

virtual void RemoveChild ( unsigned int _id )

virtualinherited

Remove a child from this entity.

Parameters

[in] _id ID of the child to remove.

void RemoveChild ( const std::string & _name )

inherited

Remove a child by name.

Parameters

[in] _name Name of the child.

void RemoveChild ( physics::BasePtr _child )

inherited

Remove a child by pointer.

Parameters

[in] _child Pointer to the child.

void RemoveChildren ( )

inherited

Remove all children.

virtual void Reset ( )

virtualinherited

Reset the joint.

Reimplemented from Joint.

virtual void Reset ( Base::EntityType _resetType )

virtualinherited

Calls recursive Reset on one of the Base::EntityType's.

Parameters

[in] _resetType The type of reset operation

virtual void RestoreSimbodyState ( SimTK::State & _state )

virtual

restore simbody state for spawning

Reimplemented from SimbodyJoint.

virtual void SaveSimbodyState ( const SimTK::State & _state )

virtual

save simbody state for spawning

Reimplemented from SimbodyJoint.

virtual void SetAnchor	(	const unsigned int	_index,
		const ignition::math::Vector3d &	_anchor
	)

virtualinherited

Set the anchor point.

Parameters

[in]	_index	Index of the axis.
[in]	_anchor	Anchor value.

Implements Joint.

void SetAxis	(	const unsigned int	_index,
		const ignition::math::Vector3d &	_axis
	)

virtual

Set the axis of rotation where axis is specified in local joint frame.

Parameters

[in]	_index	Index of the axis to set.
[in]	_axis	Vector in local joint frame of axis direction (must have length greater than zero).

Reimplemented from SimbodyJoint.

virtual void SetDamping	(	unsigned int	_index,
		const double	_damping
	)

virtualinherited

Set the joint damping.

Parameters

[in]	_index	Index of the axis to set, currently ignored, to be implemented.
[in]	_damping	Damping value for the axis.

Implements Joint.

virtual void SetEffortLimit	(	unsigned int	_index,
		double	_effort
	)

virtualinherited

Set the effort limit on a joint axis.

Parameters

[in]	_index	Index of the axis to set.
[in]	_effort	Effort limit for the axis.

virtual void SetForce	(	unsigned int	_index,
		double	_effort
	)

virtualinherited

Set the force applied to this physics::Joint.

Note that the unit of force should be consistent with the rest of the simulation scales. Force is additive (multiple calls to SetForce to the same joint in the same time step will accumulate forces on that Joint). Forces are truncated by effortLimit before applied.

Parameters

[in]	_index	Index of the axis.
[in]	_effort	Force value.

Implements Joint.

virtual void SetForceImpl	(	unsigned int	_index,
		double	_force
	)

protectedvirtual

Set the force applied to this physics::Joint.

Note that the unit of force should be consistent with the rest of the simulation scales. Force is additive (multiple calls to SetForceImpl to the same joint in the same time step will accumulate forces on that Joint).

Parameters

[in]	_index	Index of the axis.
[in]	_force	Force value. internal force, e.g. damping forces. This way, Joint::appliedForce keep track of external forces only.

Implements SimbodyJoint.

virtual void SetLowerLimit	(	const unsigned int	_index,
		const double	_limit
	)

virtualinherited

Set the joint's lower limit.

For rotational axes, the value is in radians. For prismatic axes, it is in meters.

It returns ignition::math::NAN_D in case the limit can't be obtained. For instance, if the index is invalid, if the joint is fixed, etc.

Parameters

[in]	_index	Index of the axis.
[in]	_limit	Lower limit of the axis.

Reimplemented from Joint.

Reimplemented in SimbodyBallJoint, and SimbodyScrewJoint.

void SetModel ( ModelPtr _model )

inherited

Set the model this joint belongs too.

Parameters

[in] _model Pointer to a model.

virtual void SetName ( const std::string & _name )

virtualinherited

Set the name of the entity.

Parameters

[in] _name New name.

Reimplemented in Entity.

virtual bool SetParam	(	const std::string &	_key,
		unsigned int	_index,
		const boost::any &	_value
	)

virtualinherited

Set a non-generic parameter for the joint.

replaces SetAttribute(Attribute, int, double) List of parameters: "friction" Axis Coulomb joint friction coefficient. "hi_stop" Axis upper limit. "lo_stop" Axis lower limit.

Parameters

[in]	_key	String key.
[in]	_index	Index of the axis.
[in]	_value	Value of the attribute.

Implements Joint.

Reimplemented in SimbodyScrewJoint.

void SetParent ( BasePtr _parent )

inherited

Set the parent.

Parameters

[in] _parent Parent object.

virtual bool SetPosition	(	const unsigned int	_index,
		const double	_position,
		const bool	_preserveWorldVelocity = `false`
	)

overridevirtualinherited

The child links of this joint are updated based on desired position.

And all the links connected to the child link of this joint except through the parent link of this joint moves with the child link.

Parameters

[in]	_index	Index of the joint axis (degree of freedom).
[in]	_position	Position to set the joint to. unspecified, pure kinematic teleportation.
[in]	_preserveWorldVelocity	If true, the velocity of the child link with respect to the world frame will remain the same after setting the position. By default this is false, which means there are no guarantees about what the child link's world velocity will be after the position is changed (the behavior is determined by the underlying physics engine).

Note: {Only ODE and Bullet support _preserveWorldVelocity being true.}

Returns: returns true if operation succeeds, false if it fails.

Reimplemented from Joint.

bool SetPositionMaximal	(	const unsigned int	_index,
		double	_position,
		const bool	_preserveWorldVelocity = `false`
	)

protectedinherited

Helper function for maximal coordinate solver SetPosition.

The child links of this joint are updated based on position change. And all the links connected to the child link of this joint except through the parent link of this joint moves with the child link.

Parameters

[in]	_index	Index of the joint axis (degree of freedom).
[in]	_position	Position to set the joint to.
[in]	_preserveWorldVelocity	True if to preserve the world velocity before set position, default is false.

Returns: returns true if operation succeeds, false if it fails.

virtual void SetProvideFeedback ( bool _enable )

virtualinherited

Set whether the joint should generate feedback.

Parameters

[in] _enable True to enable joint feedback.

Reimplemented in ODEJoint, and BulletJoint.

void SetSaveable ( bool _v )

inherited

Set whether the object should be "saved", when the user selects to save the world to xml.

Parameters

[in] _v Set to True if the object should be saved.

virtual bool SetSelected ( bool _show )

virtualinherited

Set whether this entity has been selected by the user through the gui.

Parameters

[in] _show True to set this entity as selected.

Reimplemented in Link.

void SetState ( const JointState & _state )

inherited

Set the joint state.

Parameters

[in] _state Joint state

virtual void SetStiffness	(	unsigned int	_index,
		const double	_stiffness
	)

virtualinherited

Set the joint spring stiffness.

Parameters

[in]	_index	Index of the axis to set, currently ignored, to be implemented.
[in]	_stiffness	Spring stiffness value for the axis. : rename to SetSpringStiffness()

Implements Joint.

virtual void SetStiffnessDamping	(	unsigned int	_index,
		double	_stiffness,
		double	_damping,
		double	_reference = `0`
	)

virtualinherited

Set the joint spring stiffness.

Parameters

[in]	_index	Index of the axis to set, currently ignored, to be implemented.
[in]	_stiffness	Stiffness value for the axis.
[in]	_reference	Spring zero load reference position. : rename to SetSpringStiffnessDamping()

Implements Joint.

void SetStopDissipation	(	unsigned int	_index,
		double	_dissipation
	)

inherited

Set joint stop dissipation.

Parameters

[in]	_index	joint axis index.
[in]	_dissipation	joint stop dissipation coefficient.

void SetStopStiffness	(	unsigned int	_index,
		double	_stiffness
	)

inherited

Set joint stop stiffness.

Parameters

[in]	_index	joint axis index.
[in]	_stiffness	joint stop stiffness coefficient.

virtual void SetUpperLimit	(	const unsigned int	_index,
		const double	_limit
	)

virtualinherited

Set the joint's upper limit.

For rotational axes, the value is in radians, for prismatic axes it is in meters.

Parameters

[in]	_index	Index of the axis, defaults to 0.
[in]	_limit	Lower limit of the axis.

Reimplemented from Joint.

Reimplemented in SimbodyBallJoint, and SimbodyScrewJoint.

virtual void SetVelocity	(	unsigned int	_index,
		double	_vel
	)

virtual

Set the velocity of an axis(index).

In ODE and Bullet, the SetVelocityMaximal function is used to set the velocity of the child link relative to the parent. In Simbody and DART, this function updates the velocity state, which has a recursive effect on the rest of the chain.

Parameters

[in]	_index	Index of the axis.
[in]	_vel	Velocity.

Implements Joint.

virtual void SetVelocityLimit	(	unsigned int	_index,
		double	_velocity
	)

virtualinherited

Set the velocity limit on a joint axis.

Parameters

[in]	_index	Index of the axis to set.
[in]	_velocity	Velocity limit for the axis.

bool SetVelocityMaximal	(	unsigned int	_index,
		double	_velocity
	)

protectedinherited

Helper function for maximal coordinate solver SetVelocity.

The velocity of the child link of this joint is updated relative to the current parent velocity. It currently does not act recursively.

Parameters

[in]	_index	Index of the joint axis (degree of freedom).
[in]	_velocity	Velocity to set at this joint.

Returns: returns true if operation succeeds, false if it fails.

void SetWorld ( const WorldPtr & _newWorld )

inherited

Set the world this object belongs to.

This will also set the world for all children.

Parameters

[in] _newWorld The new World this object is part of.

std::string TypeStr ( ) const

inherited

Get the string name for the entity type.

Returns: The string name for this entity.

virtual void UnregisterIntrospectionItems ( )

protectedvirtualinherited

Unregister items in the introspection service.

void Update ( )

virtualinherited

Update the joint.

Reimplemented from Base.

virtual void UpdateParameters ( sdf::ElementPtr _sdf )

virtualinherited

Update the parameters using new sdf values.

Parameters

[in] _sdf SDF values to update from.

Reimplemented from Base.

virtual double UpperLimit ( const unsigned int _index ) const

virtualinherited

Get the joint's upper limit.

For rotational axes, the value is in radians. For prismatic axes, it is in meters.

It returns ignition::math::NAN_D in case the limit can't be obtained. For instance, if the index is invalid, if the joint is fixed, etc.

Parameters

[in] _index Index of the axis, defaults to 0.

Returns: Lower limit of the axis.

Reimplemented from Joint.

Reimplemented in SimbodyBallJoint, and SimbodyScrewJoint.

common::URI URI ( ) const

inherited

Return the common::URI of this entity.

The URI includes the world where the entity is contained and all the hierarchy of sub-entities that can compose this entity. E.g.: A link entity contains the name of the link and the model where the link is contained.

Returns: The URI of this entity.

ignition::math::Pose3d WorldPose ( ) const

inherited

Get pose of joint frame relative to world frame.

Note that the joint frame is defined with a fixed offset from the child link frame.

Returns: Pose of joint frame relative to world frame.

Member Data Documentation

LinkPtr anchorLink

protectedinherited

Anchor link.

ignition::math::Vector3d anchorPos

protectedinherited

Anchor pose.

This is the xyz position of the joint frame specified in the world frame.

ignition::math::Pose3d anchorPose

protectedinherited

Anchor pose specified in SDF <joint><pose> tag.

AnchorPose is the transform from child link frame to joint frame specified in the child link frame. AnchorPos is more relevant in normal usage, but sometimes, we do need this (e.g. GetForceTorque and joint visualization).

gazebo::event::ConnectionPtr applyDamping

protectedinherited

apply damping for adding viscous damping forces on updates

bool axisParentModelFrame[2]

protectedinherited

Flags that are set to true if an axis value is expressed in the parent model frame.

Otherwise use the joint frame. See issue #494.

LinkPtr childLink

protectedinherited

The first link this joint connects to.

Base_V children

protectedinherited

Children of this entity.

SimTK::Constraint constraint

inherited

: isValid() if we used a constraint to model this joint.

Set when we build the Simbody model. How this joint was modeled in the Simbody System. We used either a mobilizer or a constraint, but not both. The type of either one is the same as the joint type above.

SimTK::Force::MobilityLinearDamper damper[MAX_JOINT_AXIS]

inherited

: for enforcing joint damping forces.

Set when we build the Simbody model. : Also, consider moving this into individual joint type subclass so we can specify custom dampers for special joints like ball joints.

SimTK::Transform defxAB

inherited

default mobilizer pose

double dissipationCoefficient[2]

protectedinherited

joint viscous damping coefficient

double effortLimit[2]

protectedinherited

Store Joint effort limit as specified in SDF.

std::vector<common::URI> introspectionItems

protectedinherited

All the introspection items regsitered for this.

bool isReversed

inherited

: if mobilizer, did it reverse parent&child? Set when we build the Simbody model.

SimTK::Force::MobilityLinearStop limitForce[MAX_JOINT_AXIS]

inherited

: for enforcing joint stops Set when we build the Simbody model.

: Also, consider moving this into individual joint type subclass so we can specify custom dampers for special joints like ball joints. Assuming this is not used for BallJoints it's ok here for now.

double lowerLimit[2]

protectedinherited

Store Joint position lower limit as specified in SDF.

SimTK::MobilizedBody mobod

inherited

Use isValid() if we used a mobilizer Set when we build the Simbody model.

How this joint was modeled in the Simbody System. We used either a mobilizer or a constraint, but not both. The type of either one is the same as the joint type above.

ModelPtr model

protectedinherited

Pointer to the parent model.

bool mustBreakLoopHere

inherited

Force Simbody to break a loop by using a weld constraint.

This flag is needed by SimbodyPhysics::MultibodyGraphMaker, so kept public.

BasePtr parent

protectedinherited

Parent of this entity.

ignition::math::Pose3d parentAnchorPose

protectedinherited

Anchor pose relative to parent link frame.

LinkPtr parentLink

protectedinherited

The second link this joint connects to.

bool physicsInitialized

inherited

bool provideFeedback

protectedinherited

Provide Feedback data for contact forces.

sdf::ElementPtr sdf

protectedinherited

The SDF values for this object.

SimbodyPhysicsPtr simbodyPhysics

protectedinherited

keep a pointer to the simbody physics engine for convenience

SimTK::Force::MobilityLinearSpring spring[MAX_JOINT_AXIS]

inherited

: Spring force element for enforcing joint stiffness.

The element is assigned when constructing Simbody model in SimbodyPhysics::AddDynamicModelToSimbodySystem. : Also, consider moving this into individual joint type subclass so we can specify custom springs for special joints like ball joints.

double springReferencePosition[2]

protectedinherited

joint spring reference (zero load) position

double stiffnessCoefficient[2]

protectedinherited

joint stiffnessCoefficient

double upperLimit[2]

protectedinherited

Store Joint position upper limit as specified in SDF.

double velocityLimit[2]

protectedinherited

Store Joint velocity limit as specified in SDF.

SimTK::MultibodySystem* world

protectedinherited

Simbody Multibody System.

JointWrench wrench

protectedinherited

Cache Joint force torque values in case physics engine clears them at the end of update step.

SimTK::Transform xCB

inherited

child body frame to mobilizer frame

SimTK::Transform xPA

inherited

Normally A=F, B=M.

But if reversed, then B=F, A=M. parent body frame to mobilizer frame

The documentation for this class was generated from the following file:

SimbodyHingeJoint.hh

Public Types

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation