Jacobian of the iCub

[pattacini]

@LakshithaPW commented on Wed Feb 15 2017

Dear All,

I was wondering anyone could help me to find the Jacobian in real time for the iCub Simulator ?
I want to control the end effector of the iCub given a specified task space velocity.

Thanks in advance

[pattacini]

Hi @LakshithaPW

To get the Jacobian of the arm (or any other limb) of the iCub (no matter if we consider the simulated or the real robot), you might want to use iKin library, whose tutorials are available from our manual.

Essentially, you ought to use a snippet looking pretty much the following:

#include <iCub/iKin/iKinFwd.h>

iCub::iKin::iCubArm arm("left");   // declare the arm object
arm.setAllConstraints(false);   // we don't need to update the limits from the robot to compute the Jacobian
arm.releaseLink(0);   // release torso pitch joint
arm.releaseLink(1);   // release torso roll joint
arm.releaseLink(2);   // release torso yaw joint

// retrieve here joints from the torso and the left_arm
yarp::sig::Vector torso(3), left_arm(16);
ipos_torso->getEncoders(torso.data());
ipos_left_arm->getEncoders(left_arm.data());

// fill in the vector of degrees of freedom
yarp::sig::Vector dofs(arm.getDOF());
dofs[0]=torso[2];   // be careful of the order here
dofs[1]=torso[1];
dofs[2]=torso[0];
dofs[3]=left_arm[0];
// ...
dofs[9]=left_arm[6];

yarp::sig::Matrix Jacobian=arm.GeoJacobian((M_PI/180.0)*dofs);   // iKin works with radians

Besides recruiting directly the Jacobian, you might also consider relying on the Task-Space Reference Velocity Command of the Cartesian Interface.

[LakshithaPW]

Thank you very much for the response..
I'll follow the snippet.

[pattacini]

Related issue #208.