Force regulation for pick-and-place units by use of adaptive impedance control

Force regulation is an important topic in pick-and-place applications. To this end, a novel control concept for a setup consisting of two serially and co-linearly mounted axes is proposed. The position trajectory of the larger axis is tracked by a standard PD-controller. The feedback-law for the second and smaller axis mounted on the slide of the larger one is designed as an impedance control. A particular adaptive configuration of the proposed setup allows to achieve different tasks without changing the principal structure of the control algorithm. Firstly, tracking the position of the end effector rigidly mounted at the second drive may be achieved as long as no obstacle is hit. Secondly, a desired force trajectory to be imposed by the end effector may be tracked after collision. Finally, a sudden collapse of the obstacle, as it may happen in the considered application, can be dealt without any change of the control law. The efficiency of the proposed algorithms is shown on the basis of simulation results taking into account both, nonlinear friction models and parameter uncertainties.