Method and apparatus for hybrid position/force control of multi-arm cooperating robots

DETAILED DESCRIPTION As noted above, the prior art concentrated on a master-slave approach wherein, for example, a master arm pulls and the slave simply follows without contributing to the task.
This invention departs from that conventional approach by providing a system free from any master or slave arm.
Instead two or more robot arms each share in applying a scaled amount of force in order to move an object being controlled by the two or more robot arms to a desired position and orientation.
The novel architecture of this invention provides hybrid position/force control of robots having a plurality of cooperating arms wherein each arm is controlled such that the burden of actuation is shared between the arms in a non-conflicting way as they control the position of, and force upon, a designated point on a mutually-held object.
This invention is applicable whether or not the controlled object is in contact with a rigid external environment.
The position control loops of this invention are based upon each manipulator's Cartesian space dynamic equations.
In the position control subspace, a feature of this invention allows the robot arms to exert additional forces/torques to achieve compression, tension, or torsion in the object without affecting the execution of motion trajectories.
In the force control subspace, the total force/torque magnitude square is minimized while realizing the net desired force/torque on the environment.