Protective Fuzzy Control of a Two-Wheeled Mobile Pendulum Robot: Design and Optimization

摘要

This paper describes the design and optimization results of a cascade fuzzy control structure developed and applied for the stabilization of an underactuated two-wheeled mobile pendulum system. The proposed fuzzy control strategy applies three fuzzy logic controllers to both provide the planar motion of the plant and reduce the inner body oscillations. Among these controllers, one is a special PI-type fuzzy logic controller designed to simultaneously ensure the linear speed and prevent high current peaks in the motor drive system. The input-output ranges and membership functions of the controllers are initially selected based on earlier studies. A complex fitness function is formulated for the quantification of the overall control performance. In this fitness function, the quality of reference tracking related to the planar motion, the efficiency of the suppression of inner body oscillations as well as the magnitude of the resulting current peaks in the driving mechanism are considered. Using the defined fitness function, the optimization of the parameters of fuzzy logic controllers is realized with the aid of particle swarm optimization, yielding the optimal possible control performance. Results demonstrate that the optimized fuzzy control strategy provides satisfying overall control quality with both fast closed loop behavior and small current peaks in the driving mechanism of the plant. The flexibility of the proposed fuzzy control strategy allows to protect the plant’s electro-mechanical parts against jerks and vibrations along with smaller energy consumption. At the end of the paper, a look-up table based implementation technique of fuzzy logic controllers is described, which requires small computational time and is suitable for small embedded processors.