Class RobotModel
Defined in File robot_model.hpp
Class Documentation
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class RobotModel
Represents a chain or tree of robot elements (rigid bodies and joints).
(Currently, only chains of elements are fully supported)
Public Types
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using ActuatorType = robot_model::ActuatorType
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using BracketType = robot_model::BracketType
Public Functions
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RobotModel()
Creates a robot model object with no bodies and an identity base frame.
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std::unique_ptr<RobotModel> createSubtree(size_t element_index)
Create a RobotModel object that is a subtree of this robot model, beginning at a given element. The created subtree is linked to the original RobotModel, and so kinematics and IK operations are not safe if the original model and subtree are accessed from different threads. However, the lifetimes can be treated as independent (the original RobotModel can be disposed of while the subtree is still in use).
- Parameters:
element_index – The index of the RobotMOdelElement, using a depth-first tree traversal, of the element that becomes the root of the new robot model object
- Returns:
A unique_ptr-wrapped RobotModel object is returned, represending a substree starting at the given index, or an empty unique_ptr if the element index is invalid for this robot model.
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~RobotModel() noexcept
Destructor cleans up robot model object, including all managed elements.
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void setBaseFrame(const Eigen::Matrix4d &base_frame)
Set the transform from a world coordinate system to the input of the root element in this robot model object. Defaults to an identity 4x4 matrix.
The world coordinate system is used for all position, vector, and transformation matrix parameters in the member functions.
- Parameters:
base_frame – The 4x4 homogeneous transform from the world frame to the root kinematic body frame.
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Eigen::Matrix4d getBaseFrame() const
Returns the transform from the world coordinate system to the root kinematic body, as set by the setBaseFrame function.
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size_t getFrameCount(FrameType frame_type) const
Return the number of frames in the forward kinematics.
Note that this depends on the type of frame requested — for center of mass frames, there is one per added body; for output frames, there is one per output per body.
- Parameters:
frame_type – Which type of frame to consider — see HebiFrameType enum.
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inline size_t getFrameCount(HebiFrameType frame_type) const
Return the number of frames in the forward kinematics.
- Deprecated:
Replaced by getFrameCount(FrameType) accepting C++ enum
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size_t getDoFCount() const
Returns the number of settable degrees of freedom in the kinematic tree. (This is equal to the number of actuators added).
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std::string getMeshPath(size_t mesh_frame_index) const
Returns the path to the mesh used in the “ith” mesh frame.
Note that this may be an empty string for frames without a custom mesh, even if those frames have a mesh transform. For built-in elements with known meshes (e.g., a bracket or an R-series actuator), this currently returns an empty string, but this behavior may change in the future and should not be relied upon.
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bool addRigidBody(const Eigen::Matrix4d &com, const Eigen::VectorXd &inertia, double mass, const Eigen::Matrix4d &output)
Adds a rigid body with the specified properties to the robot model.
- Parameters:
com – 4x4 matrix of the homogeneous transform to the center of mass location, relative to the input frame of the element. Note that this frame is also the frame the inertia tensor is given in.
inertia – The 6 element representation (Ixx, Iyy, Izz, Ixy, Ixz, Iyz) of the inertia tensor, in the frame given by the COM.
output – 4x4 matrix of the homogeneous transform to the output frame, relative to the input frame of the element.
mass – The mass of this element.
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bool addJoint(JointType joint_type)
Adds a degree of freedom about the specified axis.
This does not represent an element with size or mass, but only a connection between two other elements about a particular axis.
- Parameters:
joint_type – The axis of rotation or translation about which this joint allows motion.
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inline bool addJoint(HebiJointType joint_type)
Adds a degree of freedom about the specified axis.
- Deprecated:
Replaced by addJoint(JointType) accepting C++ enum
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bool addActuator(robot_model::ActuatorType actuator_type)
Add an element to the robot model with the kinematics/dynamics of an X5 actuator.
- Parameters:
actuator_type – The type of actuator to add.
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bool addLink(robot_model::LinkType link_type, double extension, double twist, LinkInputType input_type = LinkInputType::RightAngle, LinkOutputType output_type = LinkOutputType::RightAngle)
Add an element to the robot model with the kinematics/dynamics of a link between two actuators.
- Parameters:
link_type – The type of link between the actuators, e.g. a tube link between two X5 or X8 actuators.
extension – The center-to-center distance between the actuator rotational axes.
twist – The rotation (in radians) between the actuator axes of rotation. Note that a 0 radian rotation will result in a z-axis offset between the two actuators, and a pi radian rotation will result in the actuator interfaces to this tube being in the same plane, but the rotational axes being anti-parallel.
input_type – The style of input adapter on the link.
output_type – The style of input adapter on the link.
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bool addBracket(robot_model::BracketType bracket_type)
Add an element to the robot model with the kinematics/dynamics of a bracket between two actuators.
- Parameters:
bracket_type – The type of bracket to add.
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bool addEndEffector(EndEffectorType end_effector_type)
Add an end effector element to the robot model.
For a “custom” type end effector, indentity transforms and zero mass and inertia parameters are used.
- Parameters:
end_effector_type – The type of end_effector to add.
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bool addEndEffector(double x, double y, double z)
Add an end effector element to the robot model.
For a “custom” type end effector, indentity transforms and zero mass and inertia parameters are used.
- Parameters:
frame – The frame of the output of the end effector
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bool addEndEffector(const Eigen::Matrix4d &com, const Eigen::VectorXd &inertia, double mass, const Eigen::Matrix4d &output)
Adds a “custom” type end effector with the specified properties to the robot model.
- Parameters:
com – 4x4 matrix of the homogeneous transform to the center of mass location, relative to the input frame of the element. Note that this frame is also the frame the inertia tensor is given in.
inertia – The 6 element representation (Ixx, Iyy, Izz, Ixy, Ixz, Iyz) of the inertia tensor, in the frame given by the COM.
output – 4x4 matrix of the homogeneous transform to the output frame, relative to the input frame of the element.
mass – The mass of this element.
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void getForwardKinematics(FrameType, const Eigen::VectorXd &positions, Matrix4dVector &frames) const
Generates the forward kinematics for the given robot model.
See getFK for details.
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inline void getForwardKinematics(HebiFrameType frame_type, const Eigen::VectorXd &positions, Matrix4dVector &frames) const
Generates the forward kinematics for the given robot model.
- Deprecated:
Replaced by getForwardKinematics accepting C++ enum
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void getFK(FrameType, const Eigen::VectorXd &positions, Matrix4dVector &frames) const
Generates the forward kinematics for the given robot model.
The order of the returned frames is in a depth-first tree. As an example, assume a body A has one output, to which body B is connected to. Body B has two outputs; actuator C is attached to the first output and actuator E is attached to the second output. Body D is attached to the only output of actuator C:
(BASE) A - B(1) - C - D (2) | E
For center of mass frames, the returned frames would be A-B-C-D-E.
For output frames, the returned frames would be A-B(1)-C-D-B(2)-E.
- Parameters:
frame_type – Which type of frame to consider — see FrameType enum.
positions – A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
frames – An array of 4x4 transforms; this is resized as necessary in the function and filled in with the 4x4 homogeneous transform of each frame. Note that the number of frames depends on the frame type.
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inline void getFK(HebiFrameType frame_type, const Eigen::VectorXd &positions, Matrix4dVector &frames) const
Generates the forward kinematics for the given robot model.
- Deprecated:
Replaced by getFK accepting C++ enum
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void getEndEffector(const Eigen::VectorXd &positions, Eigen::Matrix4d &transform) const
Generates the forward kinematics to the end effector (leaf node) frame(s).
Note — for center of mass frames, this is one per leaf node; for output frames, this is one per output per leaf node, in depth first order.
This overload is for kinematic chains that only have a single leaf node frame.
(Currently, kinematic trees are not fully supported — only kinematic chains — and so there are not other overloads for this function).
- Parameters:
positions – A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
transform – A 4x4 transform that is resized as necessary in the function and filled in with the homogeneous transform to the end effector frame.
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template<typename ...Args>
inline IKResult solveInverseKinematics(const Eigen::VectorXd &initial_positions, Eigen::VectorXd &result, const Args&... args) const Solves for an inverse kinematics solution given a set of objectives.
See solveIK for details.
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template<typename ...Args>
inline IKResult solveIK(const Eigen::VectorXd &initial_positions, Eigen::VectorXd &result, const Args&... objectives) const Solves for an inverse kinematics solution given a set of objectives.
- Parameters:
initial_positions – The seed positions/angles (in SI units of meters or radians) to start the IK search from; equal in length to the number of DoFs of the kinematic tree.
result – A vector equal in length to the number of DoFs of the kinematic tree; this will be filled in with the IK solution (in SI units of meters or radians), and resized as necessary.
objectives – A variable number of objectives used to define the IK search (e.g., target end effector positions, etc). Each argument must have a base class of Objective.
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void getJacobians(FrameType, const Eigen::VectorXd &positions, MatrixXdVector &jacobians) const
Generates the Jacobian for each frame in the given kinematic tree.
See getJ for details.
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inline void getJacobians(HebiFrameType frame_type, const Eigen::VectorXd &positions, MatrixXdVector &jacobians) const
Generates the Jacobian for each frame in the given kinematic tree.
- Deprecated:
Replaced by getJacobians accepting C++ enum
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void getJ(FrameType, const Eigen::VectorXd &positions, MatrixXdVector &jacobians) const
Generates the Jacobian for each frame in the given kinematic tree.
- Parameters:
frame_type – Which type of frame to consider — see FrameType enum.
positions – A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
jacobians – A vector (length equal to the number of frames) of matrices; each matrix is a (6 x number of dofs) jacobian matrix for the corresponding frame of reference on the robot. This vector is resized as necessary inside this function.
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inline void getJ(HebiFrameType frame_type, const Eigen::VectorXd &positions, MatrixXdVector &jacobians) const
Generates the Jacobian for each frame in the given kinematic tree.
- Deprecated:
Replaced by getJ accepting C++ enum
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void getJacobianEndEffector(const Eigen::VectorXd &positions, Eigen::MatrixXd &jacobian) const
Generates the Jacobian for the end effector (leaf node) frames(s).
See getJEndEffector for details.
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void getJEndEffector(const Eigen::VectorXd &positions, Eigen::MatrixXd &jacobian) const
Generates the Jacobian for the end effector (leaf node) frames(s).
Note — for center of mass frames, this is one per leaf node; for output frames, this is one per output per leaf node, in depth first order.
This overload is for kinematic chains that only have a single leaf node frame.
(Currently, kinematic trees are not fully supported — only kinematic chains — and so there are not other overloads for this function).
- Parameters:
positions – A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
jacobian – A (6 x number of dofs) jacobian matrix for the corresponding end effector frame of reference on the robot. This vector is resized as necessary inside this function.
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void getMasses(Eigen::VectorXd &masses) const
Returns the mass of each rigid body (or combination of rigid bodies) in the robot model.
- Parameters:
masses – A vector which is filled with the masses in the robot model. This vector is resized as necessary inside this function (it is set to have length equal to the number of com frames).
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void getMetadata(std::vector<MetadataBase> &metadata) const
Returns the metadata of each component of the robot model.
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void getGravCompEfforts(const Eigen::VectorXd &angles, const Eigen::Vector3d &gravity, Eigen::VectorXd &comp_torque) const
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void getDynamicCompEfforts(const Eigen::VectorXd &angles, const Eigen::VectorXd &cmd_pos, const Eigen::VectorXd &cmd_vel, const Eigen::VectorXd &cmd_accel, Eigen::VectorXd &comp_torque, double dt) const
Public Static Functions
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static std::unique_ptr<RobotModel> loadHRDF(const std::string &file)
Creates a robot model object from the content of the HRDF file.
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static std::unique_ptr<RobotModel> loadHRDFString(const std::string &string)
Creates a robot model object from the content of the HRDF description in the string.
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using ActuatorType = robot_model::ActuatorType