Parameter Estimation and an Extended Predictive-Based Tuning Method for a Lab-Scale Distillation Column

The present study proposes a new PI controller tuning method using extended predictive control (EPC). The PI controller parameter values are calculated using the EPC controller output and its closed-loop response. This provides a simple and an effective tuning strategy which results in an improved closed-loop response compared to conventional tuning methods. The tuning methodology is applicable for single input single output and multi input multi output stable processes. Simulation and experimental results reveal the efficacy of the method under plant uncertainty conditions.

On-line delay estimation for stable, unstable and integrating systems under step response

A simple but effective on-line method to estimate the delay from step response, which can be used for stable, unstable and integrating systems, is proposed in this paper. The estimation and control are made simultaneously since the nominal delay is updated in closed-loop based on certain calculus on the output signal. Moreover, the approach is based on a Modified Smith Predictor and the delay estimation is implemented using a multi-model scheme with fixed models. Additionally, the convergence properties of the estimation algorithm and the stability analysis of the closed-loop are well-defined. Simulation examples show the effectiveness of the proposed method, where the delay estimation leads to an optimal and robust controller, tackling the uncertainty in the delay.

A novel predictive control algorithm and robust stability criteria for integrating processes

This paper introduces a novel predictive controller for single-input/single-output (SISO) integrating systems, which can be directly applied without pre-stabilizing the process. The control algorithm is designed on the basis of the tested step response model. To produce a bounded system response along the finite predictive horizon, the effect of the integrating mode must be zeroed while unmeasured disturbances exist. Here, a novel predictive feedback error compensation method is proposed to eliminate the permanent offset between the setpoint and the process output while the integrating system is affected by load disturbance. Also, a rotator factor is introduced in the performance index, which is contributed to the improvement robustness of the closed-loop system. Then on the basis of Jury's dominant coefficient criterion, a robust stability condition of the resulted closed loop system is given. There are only two parameters which need to be tuned for the controller, and each has a clear physical meaning, which is convenient for implementation of the control algorithm. Lastly, simulations are given to illustrate that the proposed algorithm can provide excellent closed loop performance compared with some reported methods.

Analysis and design of a double two-degree-of-freedom control scheme

Robust analysis and design for a double two-degree-of-freedom (TDF) scheme are discussed in the paper. It is shown that the double TDF scheme is a TDF version of the internal model control (IMC) structure for integrating and unstable processes and retains the property of the IMC structure for stable processes. A robustness measure is proposed assuming that the controlled process has a general uncertainty description. The measure is convenient for comparing the robustness of different control systems and can be used as a guideline for robust tuning. Finally, a TDF-IMC method is proposed to design and tune the parameters of the double TDF scheme to achieve improved robust performance.

Modified Smith predictor design for periodic disturbance rejection

In this paper, a modified Smith predictor control scheme is proposed for periodic disturbance rejection in both stable and unstable processes with time delay. Without affecting the superior setpoint response of Smith predictor control, the regulation performance under periodic disturbance can be enhanced significantly by the proposed design. Meanwhile, the asymptotical rejection for non-periodic disturbance will also be improved. Internal stability is investigated for a closed-loop control system. The effectiveness of the proposed scheme will be demonstrated by simulations as well as a test on an experimental thermal system.

A new two-degree-of-freedom level control scheme

In this paper, a two-degree-of-freedom level control scheme for delay free processes is analyzed. The nominal performance and robustness are examined. And sufficient and necessary conditions for robust stability are derived. An alternative level control scheme is developed for processes with dead time and suboptimal controllers that can produce smooth response are derived analytically based on the internal model control. The scheme has an important feature in that it is simple and transparent in design and in the corporation of performance and robust stability issues. Numerical examples are provided to compare the proposed scheme with those developed.