CACSD for controller ASIC implementation

In recent years, the prime implementation medium for control algorithms has been the digital processor with embedded software. These general purpose programmable devices have been used with success within many control system applications as a consequence of their low cost and size benefits coupled with high reliability. While the embedded software approach does provide flexibility during development, there are inherent problems associated with validating such software especially in safety critical applications. This approach can now, however, be complemented by custom Integrated Circuits (ICs). Here, a suitable design may be derived as a single custom IC solution which will perform a range of the control algorithm functions (as continuous and discrete time actions) as well as sensor and actuator interfacing. They do not aim to be a viable solution for all control system applications, but to allow for an additional degree of flexibility in control law implementation. However, since it can be a time consuming and expensive process to generate a suitable custom IC solution, the designer relies on suitable circuit/system simulation methods to develop confidence in the final solution prior to manufacture/fabrication. This complements a number of aspects of control system design in that the effective use of suitable system simulation packages is an important factor for the control system designer. Both control system design and custom IC simulation techniques rely on adequate modelling of the overall control system and extraction of relevant results. This paper will discuss a number of the issues involved in the design and simulation of custom ICs for closed-loop control system applications. The underlying architecture for the controller will be based on a custom designed digital control processor with analogue and digital interfacing. The work is aimed at the integration of the control system design and IC design aspects and deriving suitable linking points within a design flow.