Application of frequency-shaped disturbance accommodating optimal control to robust assist for conveyance of flexible structures

Power assist systems have been introduced to reduce workers' load in industrial production. The author has studied on control systems for power assisted conveyance of flexible structures. Generally, the systems include influences of various kinds of uncertainties. One of them is vibration influence of controlled objects to operators. Another one is structured uncertainty such as nonlinear friction or parameter variations. The author's previous paper proposed a robust assist system design by taking these uncertainties into account. It consisted of an impedance controller, a disturbance accommodating optimal controller, a disturbance observer and a reaction force controller. However, the nonlinear friction such as Coulomb friction often induces chattering motion. Such a motion may cause a controlled object spill-over instability because the previous control system design does not take influences of unstructured uncertainties into account. Therefore, this note provides a modified version of the previous design by using the frequency-shaped disturbance accommodating optimal control. This note adopts the same controlled object as the author's previous paper. The effectiveness of the modification is verified by simulations. © 2012 The Japan Society of Mechanical Engineers.