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Journal of Inforamtion Science and Engineering, Vol.18 No.2, pp.145-161 (March 2002)

An Associative Architecture of CMAC for
Mobile Robot Motion Control

Yuan-Pao Hsu, Kao-Shing Hwang and Jinn-Shyan Wang
Department of Electrical Engineering
National Chung Cheng University
Chiayi, 621 Taiwan

A new design scheme for the Cerebellar Model Articular Controller (CMAC) is presented in this article. The controller is designed with a content addressable memory (CAM) that replaces the function of the hash-coding method, which is adopted by the traditional CMAC and consumes much computation power in memory space mapping. Therefore, address mapping in the proposed CMAC is different from the hash-coding method. The CAM, which is capable of fast comparison, can immediately determine in parallel if there is any identical data in memory as the input data to be compared. If a match does not occur, the activated address is then stored in a vacant cell of the CAM indexed by a circular incremental pointer. Memory collision can be avoided unless the memory is fully occupied. In this way, the memory utilization rate can be improved to 100%, which is difficult to achieve using the conventional schemes. Meanwhile, control noise can be largely suppressed. In content addressing, the associated mask function, which is triggered when the CAM is full, can decrease the probability of collision and improve control performance. Simulation results of function approximation and truck backer-upper control indicate that the proposed CMAC is clearly superior to the conventional CMACs.

Keywords: CMAC, CAM, hash-coding, generalization, match function, memory collision, truck backer-upper control

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Received August 3, 2000; revised November 23, 2000; accepted January 9, 2001.
Communicated by Chuen-Tsai Sun.