Feedforward Control of Single-Link Flexible Manipulators by Discrete Model Inversion

Abstract

The design of feedforward controllers to control the position of single-link flexible arms is developed in this paper. The objective is to drive the tip position along a commanded trajectory without any oscillations at the tip. The method is based on the well-known dynamics model inversion technique. Since the controllers are implemented on a computer, the dynamic inversion of the single-link flexible arm is studied from a discrete point of view. A general method to obtain a feedforward controller is developed, even in the case when the system transfer function is of nonminimum phase. The method is general in the sense that it removes oscillation in the arm with any number of vibration modes. A method to modify the transfer function of these controllers to improve the robustness is also proposed in this paper. It is shown that the input preshaping scheme developed by Singer and Seering is a special case of this method. The design technique is illustrated with numerical examples and a comparison with the input preshaping method is carried out.