Base class for all joints. More...

#include <physics/physics.hh>

Inheritance diagram for gazebo::physics::Joint:

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...

Public Types inherited from gazebo::physics::Base
enum	EntityType { BASE = 0x00000000, ENTITY = 0x00000001, MODEL = 0x00000002, LINK = 0x00000004, COLLISION = 0x00000008, ACTOR = 0x00000016, 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, 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
	Joint (BasePtr _parent)
	Constructor. More...

virtual	~Joint ()
	Destructor. More...

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

virtual bool	AreConnected (LinkPtr _one, LinkPtr _two) const =0
	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...

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...

void	DisconnectJointUpdate (event::ConnectionPtr &_conn)
	Disconnect a boost::slot the the joint update signal. More...

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

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

virtual math::Vector3	GetAnchor (unsigned int _index) const =0
	Get the anchor point. More...

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

math::Angle	GetAngle (unsigned int _index) const
	Get the angle of rotation of an axis(index) More...

virtual unsigned int	GetAngleCount () const =0
	Get the angle count. More...

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

math::Quaternion	GetAxisFrameOffset (unsigned int _index) const
	Get orientation of joint axis reference frame relative to joint frame. More...

LinkPtr	GetChild () const
	Get the child link. 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)=0
	get internal force and torque values at a joint. More...

virtual math::Vector3	GetGlobalAxis (unsigned int _index) const =0
	Get the axis of rotation in global cooridnate frame. More...

virtual math::Angle	GetHighStop (unsigned int _index)=0
	Get the high stop of an axis(index). More...

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

double	GetInertiaRatio (const math::Vector3 &_axis) const
	Computes moment of inertia (MOI) across an arbitrary axis specified in the world frame. More...

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

virtual LinkPtr	GetJointLink (unsigned int _index) const =0
	Get the link to which the joint is attached according the _index. More...

virtual math::Vector3	GetLinkForce (unsigned int _index) const =0
	Get the forces applied to the center of mass of a physics::Link due to the existence of this Joint. More...

virtual math::Vector3	GetLinkTorque (unsigned int _index) const =0
	Get the torque applied to the center of mass of a physics::Link due to the existence of this Joint. More...

math::Vector3	GetLocalAxis (unsigned int _index) const
	Get the axis of rotation. More...

math::Angle	GetLowerLimit (unsigned int _index) const
	: get the joint upper limit (replaces GetLowStop and GetHighStop) More...

virtual math::Angle	GetLowStop (unsigned int _index)=0
	Get the low stop of an axis(index). More...

virtual double	GetMaxForce (unsigned int _index) GAZEBO_DEPRECATED(5.0)=0
	Get the max allowed force of an axis(index) when using Joint::SetVelocity. More...

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

math::Pose	GetParentWorldPose () const
	Get anchor pose on parent link relative to world frame. 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...

math::Angle	GetUpperLimit (unsigned int _index) const
	: get the joint lower limit (replacee GetLowStop and GetHighStop) More...

virtual double	GetVelocity (unsigned int _index) const =0
	Get the rotation rate of an axis(index) More...

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

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

math::Pose	GetWorldPose () const
	Get pose of joint frame relative to world frame. More...

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

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

virtual void	Load (sdf::ElementPtr _sdf)
	Load physics::Joint from a SDF sdf::Element. More...

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

virtual void	SetAnchor (unsigned int _index, const math::Vector3 &_anchor)=0
	Set the anchor point. More...

void	SetAngle (unsigned int _index, math::Angle _angle) GAZEBO_DEPRECATED(4.0)
	If the Joint is static, Gazebo stores the state of this Joint as a scalar inside the Joint class, so this call will NOT move the joint dynamically for a static Model. More...

virtual void	SetAxis (unsigned int _index, const math::Vector3 &_axis)=0
	Set the axis of rotation where axis is specified in local joint frame. More...

virtual void	SetDamping (unsigned int _index, double _damping)=0
	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 _effort)=0
	Set the force applied to this physics::Joint. More...

virtual bool	SetHighStop (unsigned int _index, const math::Angle &_angle)
	Set the high stop of an axis(index). More...

void	SetLowerLimit (unsigned int _index, math::Angle _limit)
	: set the joint upper limit (replaces SetLowStop and SetHighStop) More...

virtual bool	SetLowStop (unsigned int _index, const math::Angle &_angle)
	Set the low stop of an axis(index). More...

virtual void	SetMaxForce (unsigned int _index, double _force) GAZEBO_DEPRECATED(5.0)=0
	Set the max allowed force of an axis(index) when using Joint::SetVelocity. More...

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

virtual bool	SetParam (const std::string &_key, unsigned int _index, const boost::any &_value)=0
	Set a non-generic parameter for the joint. More...

virtual bool	SetPosition (unsigned int _index, double _position)
	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	SetState (const JointState &_state)
	Set the joint state. More...

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

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

void	SetUpperLimit (unsigned int _index, math::Angle _limit)
	: set the joint lower limit (replacee GetLowStop and GetHighStop) More...

virtual void	SetVelocity (unsigned int _index, double _vel)=0
	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	Update ()
	Update the joint. More...

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

Public Member Functions inherited from gazebo::physics::Base
	Base (BasePtr _parent)
	Constructor. More...

virtual	~Base ()
	Destructor. More...

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

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

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

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

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

BasePtr	GetParent () const
	Get the parent. 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...

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

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

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

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

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

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

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

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

Protected Member Functions
math::Pose	ComputeChildLinkPose (unsigned int _index, double _position)
	internal function to help us compute child link pose if a joint position change is applied. 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 math::Angle	GetAngleImpl (unsigned int _index) const =0
	Get the angle of an axis helper function. More...

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

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

Protected Member Functions inherited from gazebo::physics::Base
void	ComputeScopedName ()
	Compute the scoped name of this object based on its parents. More...

Protected Attributes
LinkPtr	anchorLink
	Anchor link. More...

math::Vector3	anchorPos
	Anchor pose. More...

math::Pose	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...

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

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

math::Angle	lowerLimit [2]
	Store Joint position lower limit as specified in SDF. More...

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

math::Pose	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...

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

double	stiffnessCoefficient [2]
	joint stiffnessCoefficient More...

math::Angle	upperLimit [2]
	Store Joint position upper limit as specified in SDF. More...

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

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

Protected Attributes inherited from gazebo::physics::Base
Base_V	children
	Children of this entity. More...

BasePtr	parent
	Parent of this entity. More...

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

WorldPtr	world
	Pointer to the world. More...

Detailed Description

Base class for all joints.

Member Enumeration Documentation

enum gazebo::physics::Joint::Attribute

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	High stop angle.
LO_STOP	Low stop angle.

Constructor & Destructor Documentation

gazebo::physics::Joint::Joint ( BasePtr _parent )

explicit

Constructor.

Parameters

[in] Joint parent

virtual gazebo::physics::Joint::~Joint ( )

virtual

Destructor.

Member Function Documentation

virtual void gazebo::physics::Joint::ApplyStiffnessDamping ( )

virtual

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

: rename to ApplySpringStiffnessDamping()

Reimplemented in gazebo::physics::ODEJoint, and gazebo::physics::BulletJoint.

virtual bool gazebo::physics::Joint::AreConnected	(	LinkPtr	_one,
		LinkPtr	_two
	)		const

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

virtual void gazebo::physics::Joint::Attach	(	LinkPtr	_parent,
		LinkPtr	_child
	)

virtual

Attach the two bodies with this joint.

Parameters

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

Reimplemented in gazebo::physics::ODEJoint, and gazebo::physics::DARTJoint.

virtual void gazebo::physics::Joint::CacheForceTorque ( )

virtual

Cache Joint Force Torque Values if necessary for physics engine.

Reimplemented in gazebo::physics::SimbodyJoint, and gazebo::physics::BulletJoint.

double gazebo::physics::Joint::CheckAndTruncateForce	(	unsigned int	_index,
		double	_effort
	)

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

math::Pose gazebo::physics::Joint::ComputeChildLinkPose	(	unsigned int	_index,
		double	_position
	)

protected

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.

template<typename T >

event::ConnectionPtr gazebo::physics::Joint::ConnectJointUpdate ( T _subscriber )

inline

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.

virtual void gazebo::physics::Joint::Detach ( )

virtual

Detach this joint from all links.

Reimplemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

void gazebo::physics::Joint::DisconnectJointUpdate ( event::ConnectionPtr & _conn )

inline

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

Parameters

[in] _conn Connection to disconnect.

void gazebo::physics::Joint::FillMsg ( msgs::Joint & _msg )

Fill a joint message.

Parameters

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

bool gazebo::physics::Joint::FindAllConnectedLinks	(	const LinkPtr &	_originalParentLink,
		Link_V &	_connectedLinks
	)

protected

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 gazebo::physics::Joint::Fini ( )

virtual

Finialize the object.

Reimplemented from gazebo::physics::Base.

virtual math::Vector3 gazebo::physics::Joint::GetAnchor ( unsigned int _index ) const

pure virtual

Get the anchor point.

Parameters

[in] _index Index of the axis.

Returns: Anchor value for the axis.

math::Pose gazebo::physics::Joint::GetAnchorErrorPose ( ) const

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.

math::Angle gazebo::physics::Joint::GetAngle ( unsigned int _index ) const

Get the angle of rotation of an axis(index)

Parameters

[in] _index Index of the axis.

Returns: Angle of the axis.

virtual unsigned int gazebo::physics::Joint::GetAngleCount ( ) const

pure virtual

Get the angle count.

Returns: The number of DOF for the joint.

virtual math::Angle gazebo::physics::Joint::GetAngleImpl ( unsigned int _index ) const

protectedpure virtual

Get the angle of an axis helper function.

Parameters

[in] _index Index of the axis.

Returns: Angle of the axis.

math::Quaternion gazebo::physics::Joint::GetAxisFrame ( unsigned int _index ) const

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.

math::Quaternion gazebo::physics::Joint::GetAxisFrameOffset ( unsigned int _index ) const

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.

LinkPtr gazebo::physics::Joint::GetChild ( ) const

Get the child link.

Returns: Pointer to the child link.

double gazebo::physics::Joint::GetDamping ( unsigned int _index )

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 gazebo::physics::Joint::GetEffortLimit ( unsigned int _index )

virtual

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 gazebo::physics::Joint::GetForce ( unsigned int _index )

virtual

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 in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

virtual JointWrench gazebo::physics::Joint::GetForceTorque ( unsigned int _index )

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::SimbodyJoint, and gazebo::physics::DARTJoint.

virtual math::Vector3 gazebo::physics::Joint::GetGlobalAxis ( unsigned int _index ) const

pure 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.

virtual math::Angle gazebo::physics::Joint::GetHighStop ( unsigned int _index )

pure virtual

Get the high stop of an axis(index).

This function is replaced by GetUpperLimit(unsigned int). If you are interested in getting the value of dParamHiStop*, use GetAttribute(hi_stop, _index)

Parameters

[in] _index Index of the axis.

Returns: Angle of the high stop value.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::SimbodyJoint, gazebo::physics::BulletJoint, gazebo::physics::BulletBallJoint, gazebo::physics::DARTScrewJoint, gazebo::physics::BulletHinge2Joint, gazebo::physics::DARTJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::SimbodyBallJoint, gazebo::physics::DARTBallJoint, gazebo::physics::ODEBallJoint, gazebo::physics::BulletSliderJoint, and gazebo::physics::SimbodyScrewJoint.

double gazebo::physics::Joint::GetInertiaRatio ( const unsigned int _index ) const

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

The ratio is given in the form of MOI_chidl / 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.

double gazebo::physics::Joint::GetInertiaRatio ( const math::Vector3 & _axis ) const

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.

math::Pose gazebo::physics::Joint::GetInitialAnchorPose ( ) const

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

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

virtual LinkPtr gazebo::physics::Joint::GetJointLink ( unsigned int _index ) const

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

virtual math::Vector3 gazebo::physics::Joint::GetLinkForce ( unsigned int _index ) const

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::DARTJoint, gazebo::physics::BulletJoint, and gazebo::physics::SimbodyJoint.

virtual math::Vector3 gazebo::physics::Joint::GetLinkTorque ( unsigned int _index ) const

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::DARTJoint, gazebo::physics::BulletJoint, and gazebo::physics::SimbodyJoint.

math::Vector3 gazebo::physics::Joint::GetLocalAxis ( unsigned int _index ) const

Get the axis of rotation.

Parameters

[in] _index Index of the axis to get.

Returns: Axis value for the provided index.

math::Angle gazebo::physics::Joint::GetLowerLimit ( unsigned int _index ) const

: get the joint upper limit (replaces GetLowStop and GetHighStop)

Parameters

[in] _index Index of the axis.

Returns: Lower limit of the axis.

virtual math::Angle gazebo::physics::Joint::GetLowStop ( unsigned int _index )

pure virtual

Get the low stop of an axis(index).

This function is replaced by GetLowerLimit(unsigned int). If you are interested in getting the value of dParamHiStop*, use GetAttribute(hi_stop, _index)

Parameters

[in] _index Index of the axis.

Returns: Angle of the low stop value.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::SimbodyJoint, gazebo::physics::BulletJoint, gazebo::physics::BulletBallJoint, gazebo::physics::DARTScrewJoint, gazebo::physics::BulletHinge2Joint, gazebo::physics::DARTJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::SimbodyBallJoint, gazebo::physics::DARTBallJoint, gazebo::physics::ODEBallJoint, gazebo::physics::BulletSliderJoint, and gazebo::physics::SimbodyScrewJoint.

virtual double gazebo::physics::Joint::GetMaxForce ( unsigned int _index )

pure virtual

Get the max allowed force of an axis(index) when using Joint::SetVelocity.

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 maximum force.

msgs::Joint::Type gazebo::physics::Joint::GetMsgType ( ) const

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

Returns: Joint type.

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

virtual

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 in gazebo::physics::ODEJoint, gazebo::physics::BulletScrewJoint, gazebo::physics::DARTJoint, gazebo::physics::SimbodyScrewJoint, gazebo::physics::BulletJoint, gazebo::physics::BulletSliderJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::ODEScrewJoint, gazebo::physics::SimbodyJoint, gazebo::physics::ODEUniversalJoint, and gazebo::physics::DARTScrewJoint.

LinkPtr gazebo::physics::Joint::GetParent ( ) const

Get the parent link.

Returns: Pointer to the parent link.

math::Pose gazebo::physics::Joint::GetParentWorldPose ( ) const

Get anchor pose on parent link relative to world frame.

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

Returns: Anchor pose on parent link in world frame.

double gazebo::physics::Joint::GetSpringReferencePosition ( unsigned int _index ) const

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 gazebo::physics::Joint::GetStiffness ( unsigned int _index )

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 gazebo::physics::Joint::GetStopDissipation ( unsigned int _index ) const

Get joint stop dissipation.

Parameters

[in] _index joint axis index.

Returns: joint stop dissipation coefficient.

double gazebo::physics::Joint::GetStopStiffness ( unsigned int _index ) const

Get joint stop stiffness.

Parameters

[in] _index joint axis index.

Returns: joint stop stiffness coefficient.

math::Angle gazebo::physics::Joint::GetUpperLimit ( unsigned int _index ) const

: get the joint lower limit (replacee GetLowStop and GetHighStop)

Parameters

[in] _index Index of the axis.

Returns: Upper limit of the axis.

virtual double gazebo::physics::Joint::GetVelocity ( unsigned int _index ) const

pure virtual

Get the rotation rate of an axis(index)

Parameters

[in] _index Index of the axis.

Returns: The rotaional velocity of the joint axis.

virtual double gazebo::physics::Joint::GetVelocityLimit ( unsigned int _index )

virtual

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

double gazebo::physics::Joint::GetWorldEnergyPotentialSpring ( unsigned int _index ) const

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,

math::Pose gazebo::physics::Joint::GetWorldPose ( ) const

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.

virtual void gazebo::physics::Joint::Init ( )

virtual

Initialize a joint.

Reimplemented from gazebo::physics::Base.

void gazebo::physics::Joint::Load	(	LinkPtr	_parent,
		LinkPtr	_child,
		const math::Pose &	_pose
	)

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.

virtual void gazebo::physics::Joint::Load ( sdf::ElementPtr _sdf )

virtual

Load physics::Joint from a SDF sdf::Element.

Parameters

[in] _sdf SDF values to load from.

Reimplemented from gazebo::physics::Base.

virtual void gazebo::physics::Joint::Reset ( )

virtual

Reset the joint.

Reimplemented from gazebo::physics::Base.

Reimplemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

virtual void gazebo::physics::Joint::SetAnchor	(	unsigned int	_index,
		const math::Vector3 &	_anchor
	)

pure virtual

Set the anchor point.

Parameters

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

Implemented in gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, gazebo::physics::SimbodyJoint, gazebo::physics::BulletScrewJoint, gazebo::physics::ODEGearboxJoint, gazebo::physics::ODEHingeJoint, gazebo::physics::ODEHinge2Joint, gazebo::physics::ODESliderJoint, gazebo::physics::DARTScrewJoint, gazebo::physics::ODEBallJoint, gazebo::physics::ODEScrewJoint, and gazebo::physics::ODEUniversalJoint.

void gazebo::physics::Joint::SetAngle	(	unsigned int	_index,
		math::Angle	_angle
	)

If the Joint is static, Gazebo stores the state of this Joint as a scalar inside the Joint class, so this call will NOT move the joint dynamically for a static Model.

But if this Model is not static, then it is updated dynamically. 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 axis.
[in]	_angle	Angle to set the joint to.

virtual void gazebo::physics::Joint::SetAxis	(	unsigned int	_index,
		const math::Vector3 &	_axis
	)

pure 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).

virtual void gazebo::physics::Joint::SetDamping	(	unsigned int	_index,
		double	_damping
	)

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, gazebo::physics::SimbodyJoint, and gazebo::physics::BulletSliderJoint.

virtual void gazebo::physics::Joint::SetEffortLimit	(	unsigned int	_index,
		double	_effort
	)

virtual

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 gazebo::physics::Joint::SetForce	(	unsigned int	_index,
		double	_effort
	)

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

virtual bool gazebo::physics::Joint::SetHighStop	(	unsigned int	_index,
		const math::Angle &	_angle
	)

virtual

Set the high stop of an axis(index).

Parameters

[in]	_index	Index of the axis.
[in]	_angle	High stop angle.

Reimplemented in gazebo::physics::ODEJoint, gazebo::physics::SimbodyJoint, gazebo::physics::BulletScrewJoint, gazebo::physics::BulletHinge2Joint, gazebo::physics::SimbodyBallJoint, gazebo::physics::DARTJoint, gazebo::physics::DARTBallJoint, gazebo::physics::ODEBallJoint, gazebo::physics::ODEUniversalJoint, gazebo::physics::BulletBallJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::BulletSliderJoint, and gazebo::physics::SimbodyScrewJoint.

void gazebo::physics::Joint::SetLowerLimit	(	unsigned int	_index,
		math::Angle	_limit
	)

: set the joint upper limit (replaces SetLowStop and SetHighStop)

Parameters

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

virtual bool gazebo::physics::Joint::SetLowStop	(	unsigned int	_index,
		const math::Angle &	_angle
	)

virtual

Set the low stop of an axis(index).

Parameters

[in]	_index	Index of the axis.
[in]	_angle	Low stop angle.

Reimplemented in gazebo::physics::ODEJoint, gazebo::physics::SimbodyJoint, gazebo::physics::BulletScrewJoint, gazebo::physics::BulletHinge2Joint, gazebo::physics::SimbodyBallJoint, gazebo::physics::DARTJoint, gazebo::physics::DARTBallJoint, gazebo::physics::ODEBallJoint, gazebo::physics::ODEUniversalJoint, gazebo::physics::BulletBallJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::BulletSliderJoint, and gazebo::physics::SimbodyScrewJoint.

virtual void gazebo::physics::Joint::SetMaxForce	(	unsigned int	_index,
		double	_force
	)

pure virtual

Set the max allowed force of an axis(index) when using Joint::SetVelocity.

Current implementation in Bullet and ODE is enforced using impulses, which enforces force/torque limits when calling Joint::SetVelocity. Current implementation is engine dependent. See for example ODE implementation in ODEHingeJoint::SetMaxForce. Note this functionality is not implemented in DART and Simbody. Note that the unit of force should be consistent with the rest of the simulation scales.

Parameters

[in]	_index	Index of the axis.
[in]	_force	Maximum force that can be applied to the axis.

void gazebo::physics::Joint::SetModel ( ModelPtr _model )

Set the model this joint belongs too.

Parameters

[in] _model Pointer to a model.

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

pure virtual

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.

Implemented in gazebo::physics::ODEJoint, gazebo::physics::DARTJoint, gazebo::physics::SimbodyScrewJoint, gazebo::physics::BulletJoint, gazebo::physics::BulletSliderJoint, gazebo::physics::BulletHingeJoint, gazebo::physics::BulletUniversalJoint, gazebo::physics::ODEScrewJoint, gazebo::physics::SimbodyJoint, and gazebo::physics::ODEUniversalJoint.

virtual bool gazebo::physics::Joint::SetPosition	(	unsigned int	_index,
		double	_position
	)

virtual

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.

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

Reimplemented in gazebo::physics::ODEJoint, and gazebo::physics::BulletJoint.

bool gazebo::physics::Joint::SetPositionMaximal	(	unsigned int	_index,
		double	_position
	)

protected

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.

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

virtual void gazebo::physics::Joint::SetProvideFeedback ( bool _enable )

virtual

Set whether the joint should generate feedback.

Parameters

[in] _enable True to enable joint feedback.

Reimplemented in gazebo::physics::ODEJoint.

void gazebo::physics::Joint::SetState ( const JointState & _state )

Set the joint state.

Parameters

[in] _state Joint state

virtual void gazebo::physics::Joint::SetStiffness	(	unsigned int	_index,
		double	_stiffness
	)

pure virtual

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()

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

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

pure virtual

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()

Implemented in gazebo::physics::ODEJoint, gazebo::physics::BulletJoint, gazebo::physics::DARTJoint, and gazebo::physics::SimbodyJoint.

void gazebo::physics::Joint::SetStopDissipation	(	unsigned int	_index,
		double	_dissipation
	)

Set joint stop dissipation.

Parameters

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

void gazebo::physics::Joint::SetStopStiffness	(	unsigned int	_index,
		double	_stiffness
	)

Set joint stop stiffness.

Parameters

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

void gazebo::physics::Joint::SetUpperLimit	(	unsigned int	_index,
		math::Angle	_limit
	)

: set the joint lower limit (replacee GetLowStop and GetHighStop)

Parameters

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

virtual void gazebo::physics::Joint::SetVelocity	(	unsigned int	_index,
		double	_vel
	)

pure 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.

virtual void gazebo::physics::Joint::SetVelocityLimit	(	unsigned int	_index,
		double	_velocity
	)

virtual

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 gazebo::physics::Joint::SetVelocityMaximal	(	unsigned int	_index,
		double	_velocity
	)

protected

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 gazebo::physics::Joint::Update ( )

virtual

Update the joint.

Reimplemented from gazebo::physics::Base.

virtual void gazebo::physics::Joint::UpdateParameters ( sdf::ElementPtr _sdf )

virtual

Update the parameters using new sdf values.

Parameters

[in] _sdf SDF values to update from.

Reimplemented from gazebo::physics::Base.

Member Data Documentation

LinkPtr gazebo::physics::Joint::anchorLink

protected

Anchor link.

math::Vector3 gazebo::physics::Joint::anchorPos

protected

Anchor pose.

This is the xyz offset of the joint frame from child frame specified in the parent link frame

math::Pose gazebo::physics::Joint::anchorPose

protected

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 gazebo::physics::Joint::applyDamping

protected

apply damping for adding viscous damping forces on updates

bool gazebo::physics::Joint::axisParentModelFrame[2]

protected

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 gazebo::physics::Joint::childLink

protected

The first link this joint connects to.

double gazebo::physics::Joint::dissipationCoefficient[2]

protected

joint viscous damping coefficient

double gazebo::physics::Joint::effortLimit[2]

protected

Store Joint effort limit as specified in SDF.

math::Angle gazebo::physics::Joint::lowerLimit[2]

protected

Store Joint position lower limit as specified in SDF.

ModelPtr gazebo::physics::Joint::model

protected

Pointer to the parent model.

math::Pose gazebo::physics::Joint::parentAnchorPose

protected

Anchor pose relative to parent link frame.

LinkPtr gazebo::physics::Joint::parentLink

protected

The second link this joint connects to.

bool gazebo::physics::Joint::provideFeedback

protected

Provide Feedback data for contact forces.

double gazebo::physics::Joint::springReferencePosition[2]

protected

joint spring reference (zero load) position

double gazebo::physics::Joint::stiffnessCoefficient[2]

protected

joint stiffnessCoefficient

math::Angle gazebo::physics::Joint::upperLimit[2]

protected

Store Joint position upper limit as specified in SDF.

double gazebo::physics::Joint::velocityLimit[2]

protected

Store Joint velocity limit as specified in SDF.

JointWrench gazebo::physics::Joint::wrench

protected

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

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

Joint.hh

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation