Relay Feedback Autotuning Method for Integrating Processes with Inverse Response and Time Delay

Abstract

Integrating processes with inverse response and time delay are frequently encountered in the level control of a boiler steam drum and are difficult to identify and control. In this paper, a systematic approach for autotuning of a proportional−integral (PI) or proportional−integral−derivative (PID) controller is proposed for this type of process. A single run of a biased relay feedback test is carried out to obtain four parameters of the model without any prior information about the time delay or the steady-state gain. Since the exact limit cycle expressions are derived, accurate parameter estimations are achieved. Then, according to the estimated model, an analytical procedure for PI/PID controller design is developed based on H ∞ optimization and internal model control (IMC) theory. The internal stability of the closed-loop feedback system is guaranteed. Moreover, robust stability analysis for the proposed control scheme is provided in the presence of model mismatches. Hence, the best tradeoff between robust stability and nominal performance of the closed-loop system can be achieved by adjusting the controller parameter λ conveniently. For illustration, simulation examples are given to compare the proposed method with those previously used.

Tuning Three-Term Controllers for Integrating Processes with both Inverse Response and Dead Time

“…Both methods give a better performance, in terms of overshoot, maximum error and settling time, as compared to the method reported in the work by (Luyben, 2003). They also provide less overshoot in terms of set-point tracking as compared to the method reported in the work by (Gu et al, 2006). The method reported in the work by (Shamsuzzoha & Lee, 2006) gives the better overall performance, in the present case.…”

“…The method reported in the work (Shamsuzzoha & Lee, 2006), for λ=0.798, ξ=1, =25, yields the two-degrees-of-freedom PID controller settings, K C =2.3892, τ =3.5778, τ D =0.7249, in the case where the set-point weighting parameter is selected as b=0.3. Finally, the method proposed in the work (Gu et al, 2006) ,d). Both methods give a better performance, in terms of overshoot, maximum error and settling time, as compared to the method reported in the work by (Luyben, 2003).…”

“…The common examples of such processes are chemical reactors, distillation columns and, especially, level control of the boiler steam drum. In recent years, identification and tuning of controllers for such process models has not received the appropriate attention as compared to other types of inverse response processes, although some very interesting results have been reported in the literature (Gu et al, 2006;Luyben, 2003;Shamsuzzoha & Lee, 2006;Srivastava & Verma, 2007). In particular, the method reported by (Luyben, 2003) determines the integral time of a series form PID controller as a fraction of the minimum PI integral time, while the controller proportional gain is obtained by satisfying the specification of +2 dB maximum closed-loop log modulus, and the derivative time is given as the one maximizing the controller gain.…”

“…In particular, the method reported by (Luyben, 2003) determines the integral time of a series form PID controller as a fraction of the minimum PI integral time, while the controller proportional gain is obtained by satisfying the specification of +2 dB maximum closed-loop log modulus, and the derivative time is given as the one maximizing the controller gain. In the work proposed by (Gu et al, 2006), PID controller tuning for IPDT-IR processes is performed based on H∞ optimization and Internal Model Control (IMC) theory. In the work www.intechopen.com PID Controller Design Approaches -Theory, Tuning and Application to Frontier Areas 30 proposed by (Shamsuzzoha & Lee, 2006), set-point weighted PID controllers are designed on the basis of the IMC theory.…”

Analytical design of a generalised predictor‐based control scheme for low‐order integrating and unstable systems with long time delay

“…Note that an IMC based PID control method was given in the reference 37 , which had shown improved control performance compared with that of the reference 38 . For fair comparison, the 2DOF IMC control method presented in Chapter 8 of the bibliography 2 is used here, of which the control structure had been studied in the references 10,11 .…”