Self-tuning cooperative control of manipulators with position/orientation uncertainties in the closed-kinematic loop

The problem of adaptive control of cooperative manipulators carrying an object in the presence of geometric uncertainties in the closed-kinematic loop is addressed in this paper. The kinematic parameters are estimated in real-time using two cascaded estimators in order to tune a cooperative controller to achieve accurate motion tracking with minimum-norm actuation force. Hence, no force measurement is required to deal with kinematic uncertainties of interconnected robotic system. The stability of the entire real-time estimator/controller system is systematically investigated. The results show that the convergence and stability of the adaptive control process can be ensured if the direction of angular velocity of the object does not remain constant over time. Experimental results demonstrate that even small error in relative position/orientation of two cooperative manipulators can give rise to tracking errors of a conventional inverse dynamic controller while the self-tuning cooperative controller is capable of significantly reducing the tracking errors.