An intuitive force feed-back to avoid singularity proximity and workspace boundaries in bilateral controlled systems based on virtual springs

Kinematic and dynamic performance of robotic manipulators is poor when they are near singularities and workspace edges. This problem becomes more complex in teleoperated systems where there are two robots whose kinematics can be different. In these cases, neither should approach singularities or workspace boundaries. This work proposes a means of preventing the robots approaching places of risk. The algorithm computes a force proportional to the distance to singularity and/or workspace boundary. This force stops the robot moving towards that direction. It should be stressed that this strategy works in a very intuitive way in bilateral controlled systems, since the operator feels as if there are virtual springs which serve to prevent him entering forbidden regions. Finally, the algorithm has been tested successfully in a telerobotic system that consists of a Stewart platform and a 6-DOF open-chain manipulator.