Motion and force control for multiple cooperative manipulators

The authors address the problem of motion and force control of multiple robot arms manipulating an object. A general control paradigm that decouples the motion and force control problems is introduced. For motion control, different control strategies are constructed on the basis of control input variables. There are three natural choices: joint torques, arm tip force vectors, and the acceleration of a generalized coordinate. The first choice allows relatively model-independent control by exploiting the Hamiltonian structure of the open-loop system. The latter two require the full model information but produce simpler control design problems. The motion control determines the joint torque only to within a manifold, owing to the multiple-arm kinematic constraint. To resolve the nonuniqueness of the joint torques, two methods are introduced. If the arm and object models are available, the allocation of the desired end-effector control force to the joint actuators can be optimized. The other possibility is to control the internal force about some set point. Effective force regulation can be achieved with little model information