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KDL::ChainIkSolverVel_wdls Class Reference
[Kinematic Families]

#include <chainiksolvervel_wdls.hpp>

Inheritance diagram for KDL::ChainIkSolverVel_wdls:
Inheritance graph
[legend]

List of all members.

Public Member Functions

virtual int CartToJnt (const JntArray &q_init, const FrameVel &v_in, JntArrayVel &q_out)
virtual int CartToJnt (const JntArray &q_in, const Twist &v_in, JntArray &qdot_out)
 ChainIkSolverVel_wdls (const Chain &chain, double eps=0.00001, int maxiter=150)
void setLambda (const double &lambda)
void setWeightJS (const Eigen::MatrixXd &Mq)
void setWeightTS (const Eigen::MatrixXd &Mx)
 ~ChainIkSolverVel_wdls ()

Private Attributes

const Chain chain
double eps
Jacobian jac
ChainJntToJacSolver jnt2jac
double lambda
int maxiter
Eigen::VectorXd S
Eigen::VectorXd tmp
Eigen::MatrixXd tmp_jac
Eigen::MatrixXd tmp_jac_weight1
Eigen::MatrixXd tmp_jac_weight2
Eigen::MatrixXd tmp_js
Eigen::MatrixXd tmp_ts
Eigen::MatrixXd U
Eigen::MatrixXd V
Eigen::MatrixXd weight_js
Eigen::MatrixXd weight_ts

Detailed Description

Implementation of a inverse velocity kinematics algorithm based on the weighted pseudo inverse with damped least-square to calculate the velocity transformation from Cartesian to joint space of a general KDL::Chain. It uses a svd-calculation based on householders rotations.

J# = M_q*Vb*pinv_dls(Db)*Ub'*M_x

where B = Mx*J*Mq

and B = Ub*Db*Vb' is the SVD decomposition of B

Mq and Mx represent, respectively, the joint-space and task-space weighting matrices. Please refer to the documentation of setWeightJS(const Eigen::MatrixXd& Mq) and setWeightTS(const Eigen::MatrixXd& Mx) for details on the effects of these matrices.

For more details on Weighted Pseudo Inverse, see : 1) [Ben Israel 03] A. Ben Israel & T.N.E. Greville. Generalized Inverses : Theory and Applications, second edition. Springer, 2003. ISBN 0-387-00293-6.

2) [Doty 93] K. L. Doty, C. Melchiorri & C. Boniveto. A theory of generalized inverses applied to Robotics. The International Journal of Robotics Research, vol. 12, no. 1, pages 1-19, february 1993.

Definition at line 63 of file chainiksolvervel_wdls.hpp.


Constructor & Destructor Documentation

KDL::ChainIkSolverVel_wdls::ChainIkSolverVel_wdls ( const Chain chain,
double  eps = 0.00001,
int  maxiter = 150 
) [explicit]

Constructor of the solver

Parameters:
chain the chain to calculate the inverse velocity kinematics for
eps if a singular value is below this value, its inverse is set to zero, default: 0.00001
maxiter maximum iterations for the svd calculation, default: 150

Definition at line 25 of file chainiksolvervel_wdls.cpp.

KDL::ChainIkSolverVel_wdls::~ChainIkSolverVel_wdls (  ) 

Definition at line 46 of file chainiksolvervel_wdls.cpp.


Member Function Documentation

virtual int KDL::ChainIkSolverVel_wdls::CartToJnt ( const JntArray &  q_init,
const FrameVel v_in,
JntArrayVel q_out 
) [inline, virtual]

not (yet) implemented.

Implements KDL::ChainIkSolverVel.

Definition at line 87 of file chainiksolvervel_wdls.hpp.

int KDL::ChainIkSolverVel_wdls::CartToJnt ( const JntArray &  q_in,
const Twist v_in,
JntArray &  qdot_out 
) [virtual]

Calculate inverse velocity kinematics, from joint positions and cartesian velocity to joint velocities.

Parameters:
q_in input joint positions
v_in input cartesian velocity
qdot_out output joint velocities
Returns:
if < 0 something went wrong

Implements KDL::ChainIkSolverVel.

Definition at line 63 of file chainiksolvervel_wdls.cpp.

void KDL::ChainIkSolverVel_wdls::setLambda ( const double &  lambda  ) 

Definition at line 58 of file chainiksolvervel_wdls.cpp.

void KDL::ChainIkSolverVel_wdls::setWeightJS ( const Eigen::MatrixXd &  Mq  ) 

Set the joint space weighting matrix

Parameters:
weight_js joint space weighting symetric matrix, default : identity. M_q : This matrix being used as a weight for the norm of the joint space speed it HAS TO BE symmetric and positive definite. We can actually deal with matrices containing a symmetric and positive definite block and 0s otherwise. Taking a diagonal matrix as an example, a 0 on the diagonal means that the corresponding joints will not contribute to the motion of the system. On the other hand, the bigger the value, the most the corresponding joint will contribute to the overall motion. The obtained solution q_dot will actually minimize the weighted norm sqrt(q_dot'*(M_q^-2)*q_dot). In the special case we deal with, it does not make sense to invert M_q but what is important is the physical meaning of all this : a joint that has a zero weight in M_q will not contribute to the motion of the system and this is equivalent to saying that it gets an infinite weight in the norm computation. For more detailed explanation : vincent.padois@upmc.fr
void KDL::ChainIkSolverVel_wdls::setWeightTS ( const Eigen::MatrixXd &  Mx  ) 

Set the task space weighting matrix

Parameters:
weight_ts task space weighting symetric matrix, default: identity M_x : This matrix being used as a weight for the norm of the error (in terms of task space speed) it HAS TO BE symmetric and positive definite. We can actually deal with matrices containing a symmetric and positive definite block and 0s otherwise. Taking a diagonal matrix as an example, a 0 on the diagonal means that the corresponding task coordinate will not be taken into account (ie the corresponding error can be really big). If the rank of the jacobian is equal to the number of task space coordinates which do not have a 0 weight in M_x, the weighting will actually not impact the results (ie there is an exact solution to the velocity inverse kinematics problem). In cases without an exact solution, the bigger the value, the most the corresponding task coordinate will be taken into account (ie the more the corresponding error will be reduced). The obtained solution will minimize the weighted norm sqrt(|x_dot-Jq_dot|'*(M_x^2)*|x_dot-Jq_dot|). For more detailed explanation : vincent.padois@upmc.fr

Member Data Documentation

Definition at line 141 of file chainiksolvervel_wdls.hpp.

Definition at line 147 of file chainiksolvervel_wdls.hpp.

Definition at line 143 of file chainiksolvervel_wdls.hpp.

Definition at line 142 of file chainiksolvervel_wdls.hpp.

Definition at line 157 of file chainiksolvervel_wdls.hpp.

Definition at line 148 of file chainiksolvervel_wdls.hpp.

Eigen::VectorXd KDL::ChainIkSolverVel_wdls::S [private]

Definition at line 145 of file chainiksolvervel_wdls.hpp.

Eigen::VectorXd KDL::ChainIkSolverVel_wdls::tmp [private]

Definition at line 149 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::tmp_jac [private]

Definition at line 150 of file chainiksolvervel_wdls.hpp.

Definition at line 151 of file chainiksolvervel_wdls.hpp.

Definition at line 152 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::tmp_js [private]

Definition at line 154 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::tmp_ts [private]

Definition at line 153 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::U [private]

Definition at line 144 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::V [private]

Definition at line 146 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::weight_js [private]

Definition at line 156 of file chainiksolvervel_wdls.hpp.

Eigen::MatrixXd KDL::ChainIkSolverVel_wdls::weight_ts [private]

Definition at line 155 of file chainiksolvervel_wdls.hpp.


The documentation for this class was generated from the following files:
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orocos_kdl
Author(s): Ruben Smits, Erwin Aertbelien, Orocos Developers
autogenerated on Fri Mar 1 16:20:15 2013