link/rt_friction - compute joint friction torque[view code]

Calling Sequence

tau_f = rt_friction(link, qd)

Parameters

• link : link object. It describes the link kinematics and dynamics.
• qd : p-element vector (p is arbitrary). A set of joint velocities.
• tau_f : p-element vector. The resulting set of joint friction torque.

Description

This function computes the joint friction torque based on friction parameter data, if any, in the link object link.

Friction is a function only of joint velocity qd. If qd is a vector (p > 1) then tau_f is a vector in which each element is the friction torque for the corresponding element in qd.

The friction model is a fairly standard one comprising viscous friction and direction dependent Coulomb friction.

Examples

   // The following example shows how rt_friction() can be used to compute
   // the joint friction torque for the waist joint of a Puma 560 robot
   exec <PATH>/models/rt_puma560.sce;       // load Puma 560 parameters
   wjoint = p560.links(1);                  // waist joint
   rt_showlink(wjoint);                     // display link data
   qd = [-1.2088, 2.7204],                  // joint velocity vector
   wjfrict = rt_friction(wjoint, qd),

   // qd(1)<0 => qd(1)*wjoint.B + wjoint.Tc(2)
   qd(1)*wjoint.B + wjoint.Tc(2),

   // qd(2)>0 => qd(2)*wjoint.B + wjoint.Tc(1)
   qd(2)*wjoint.B + wjoint.Tc(1),
   
  

See Also

rt_link,  link/rt_nofriction,  rt_robot,  robot/rt_nofriction,  robot/rt_friction,  

Authors

original Matlab version by

Peter I. Corke CSIRO Manufacturing Science and Technology

Scilab implementation by

Matteo Morelli Interdepartmental Research Center "E. Piaggio", University of Pisa

Bibliography

Corke, P.I. "A Robotics Toolbox for MATLAB", IEEE Robotics and Automation Magazine, Volume 3(1), March 1996, pp. 24-32

M.W. Walker and D.E. Orin. Efficient dynamic computer simulation of robotic mechanisms. ASME Journal of Dynamic Systems, Measurement and Control, 104:205-211, 1982