Petri Net Based Supervisory Control for Locomotion System of

The idea of a versatile six-legged walking robot, COMET-IV, has been conceived at the Robot & Control Laboratory of Chiba University based on the experience gathered from the development of walking robots COMET-I, COMET-II, and COMET-III. The mechatronic systems of COMET-IV has been designed with the aim of crossing large obstacles, a common feature of irregular and rough terrain, and at the same time autonomy of leg operation resulting into robust locomotion in the face of any partial failure of the locomotion system. Apart from controlling the leg joints at the low level resulting into change in joint angle, an efficient coordination mechanism is required to carry out the proper leg motion sequence and at the same time generate proper foot trajectory to achieve the gaits suitable for the terrain conditions. Thus the locomotion, i.e. overall body motion, requires two controllers, one for controlling the leg joints meeting the dynamic stability of the leg motion and the other one is a supervisory controller coordinating among various concurrent tasks and events resulting into body motion (locomotion) maintaining static stability of the robot body. In this research work Petri Net (PN) based versatile supervisory controller is proposed for the control of the various conditions (states) and events (transitions). Simulation has been carried out for assessing the performance of the proposed supervisory controller.