FUZZY CONTROLLER SYNTHESIS FOR AN INVERTED PENDULUM SYSTEM

A frequently discussed issue in the use of fuzzy systems for control d esign is related to the ad hoc nature by which controller synthesis is performed, where incorporation of the designer's knowledge into the s ynthesis procedure is often not straightforward. This paper describes a controller synthesis procedure based on the idea of expanding the us able region of a linear control design technique. Comparative analyses are carried out via implementation of swing-up and balancing control for a rotational inverted pendulum system. For the complete control pr oblem, the paper focuses on three aspects of fuzzy control in the over all control design: direct, supervisory, and auto-tuning fuzzy control . For swing-up control, an energy pumping strategy, enhanced by introd ucing a fuzzy supervisory mechanism, is utilized. For balancing contro l, an LQR-based linear control strategy, valid in the ''linear region' ' of operation of the pendulum, is generalized to a nonlinear direct f uzzy control design. For improved performance when modeling uncertaint ies affect controller performance, a new scheme is developed, again ba sed on the LQR design, which is a simple yet effective auto-tuned fuzz y controller, having the capability to vary its resolution on-line. Al l controllers are tested on an experimental apparatus, and performance comparisons are drawn.