Stable inversion control for flexible-link cooperating manipulators: a case study of a four-bar linkage mechanism

We consider the nonlinear inversion control for flexible-link cooperating manipulators, also known as the inverse dynamics control or the computed torque method for rigid manipulators. Difficulties in applying this method to the control of flexible link manipulators are due to the fact that the inverse dynamics system is generally unstable. As such, bounded actuator torques cannot be guaranteed. For multiple manipulators handling a common object, there are more actuators than the degrees of freedom of the system. We investigate possibilities of using the actuation redundancy to stabilize the inverse dynamics system. Consequently, nonlinear inversion control can be applied to object trajectory tracking.