The disadvantages and limitations of digital motion control systems are due mostly to the inherent properties of discrete systems that results in sampling, quantization, and truncation errors. These errors can affect seriously the load disturbance rejection limits of the controller. Also, the computation delay limits the system bandwidth and can affect the control stability when too large.
Table 2 summarizes the advantages and limitations of analog and digital technologies in motion control. One can note that the advantages of digital technology in motion control outnumber its disadvantages. Furthermore, the recent developments in VLSI, processor technology, and control theory tend to minimize the disadvantages shown. Data converters can be now incorporated on the same chip as the CPU to reduce parts count. The execution speed of new-generation processors is such that the bandwidth of digital motion control systems can now attain values comparable to that of analog ones. Self-tuning systems can be implemented to provide optimum control performance without adjustment. Simulation and CAD (computer-aided design) software are now available to help the design engineer reducing the analysis and design time of digital control systems.