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HebiKinematics/getJacobian

getJacobian calculates the matrix that relates input joint velocities to body velocities. This method calculates the partial derivatives of the kinematics equation, which relates the joint velocities to the linear and angular velocities of each body in the kinematic chain. More background on Jacobians and kinematics can be found at: http://docs.hebi.us/core_concepts.html#kinematics The Jacobian is returned as a [6 x numDoF x numBodies] set of matrices. Rows 1:3 of the Jacobian correspond to linear velocities [m/s] along the X-Y-Z axes in the world frame, while rows 4:6 correspond to rotational velocities [rad/s] about the X-Y-Z axes in the world frame. 'FrameType' Argument 'OutputFrame' calculates the transforms to the output of each body (also: 'out', 'output') 'CoMFrame' calculates the transforms to the center of mass of each body (also: 'com') 'EndEffectorFrame' calculates the transform to only the output frame of the last body, e.g., a gripper (also: 'endeffector') 'Position' Argument A [1 x numDoF] vector that specifies the position of each degree of freedom. Rotational positions are specified in [rad]. Translational positions are specified in [m]. 'FixedFrame' Argument A number that specifies which rigid body of the Jacobian is assumed to be fixed, and returns the Jacobian in this frame. This parameter is optional, and the default if not specified is the world frame, which would be the same as ['fixedframe', 0]. This parameter uses negative indexing to specify the end-effector as -1 regardless of the number of links in kinenamitic chain. Note that if you want the frame at the usual origin of the chain to be returned in the Jacobian, you will need to add a body there in the HRDF file or kinematic definition code, as the base frame of the chain is normally omitted from forward kinematics and Jacobian calculations. Examples % End-Effector Jacobian using group feedback fbk = group.getNextFeedback(); J = kin.getJacobian('endEffector', fbk.position); % Jacobian assuming the end-effector is fixed, using group % feedback. For example, if the kinematic chain were a % leg and the end-effector (the foot) is fixed to the ground. fbk = group.getNextFeedback(); J = kin.getJacobian('output', fbk.position, 'fixedframe', -1);

Method Details

Access | public |

Sealed | false |

Static | false |