New Frequency Domain PID Controller Design Method

This chapter presents a new PID controller design method based on process frequency response information. The novel ideas lie in the way that the closed-loop performance is specified via the desired response of the control signal and in the use of only two process frequency response points in the design. The relationship between the process frequency response and its step response, developed in Chapter 5, is exploited here to determine the frequency information to be used for controller design. 

This chapter consists of seven sections. In Section 6.2, we present the desired closed-loop performance specification in terms of the controller output response for both stable and integrating processes. In order to gain some insight into the new design method, Section 6.3 discusses a least squares approach to the PID controller parameter solutions. Prom the least squares solution, we propose in Section 6.4 a simpler approach based on process information at just two frequency points. Section 6.5 addresses the question of which two frequencies should be used in the design. Section 6.6 discusses the choice of a PI or a PID controller and provides some guidance with respect to the selection of the closed-loop performance parameters. Extensive simulation studies are performed in Section 6.7 and the results are compared with other design methods. 

Portions of this chapter have been reprinted from lEE Proceedings-Control Theory and Applications 142, L. Wang, T.J.D. Barnes and 

Cluett, New frequency-domain design method for PID controllers , pp. 265-271, 1995, with permission from lEE. 

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