Nowadays, the proportional–integral–derivative (PID) controller dominates industrial process control. Because of the compromise between parameters, its tuning is still a challenge for practitioners. A reference model (RM)-based PID controller—the desired dynamic equational (DDE) PID controller—is regarded as a viable alternative since it can readily eliminate the compromise. However, how to design its desired dynamic equation remains an unsolved problem which limits the application of DDE PID controllers in large-scale industrial systems. Therefore, this paper studies the desired dynamic selection of DDE PID controllers and proposes a simple and practical selection procedure without using the accurate plant model. Simulations, experiments and filed tests demonstrate the convenience and advantages of the proposed method, thus making DDE PID an effective controller type which is specifically appealing to engineers. Moreover, the successful application of DDE PID controllers to a high-pressure (HP) heater in a coal-fired power plant shows their promising prospects in the future power industry with the increasing demand to integrate more renewables into the grid.

No abstract

An important task for estimators is to solve the inverse. However, as the designs of different estimators for solving the inverse vary widely, it is difficult for engineers to be familiar with all of their properties and to design suitable estimators for different situations. Therefore, we propose a more structurally unified and functionally diverse estimator, called generalized inverse solver (GIS). GIS is inspired by the desired dynamics of control systems and understanding of the generalized inverse. It is similar to a closed-loop system, structurally consisting of nominal models and an error-correction mechanism (ECM). The nominal models can be model-based, semi-model-based, or even model-free, depending on prior knowledge of the system. In addition, we design the ECM of GIS based on desired dynamics parameterization by following a simple and meaningful rule, where states are directly used in the ECM to accelerate the convergence of GIS. A case study considering a rotary flexible link shows that GIS can greatly improve the noise suppression performance with lower loss of dynamic estimation performance, when compared with other common observers at the same design bandwidth. Moreover, the dynamic estimation performances of the three GIS approaches (i.e., model-based, semi-model-based, and model-free) are almost the same under the same parameters. These results demonstrate the strong robustness of GIS (although by means of the uniform design method). Finally, some control cases are studied, including a comparison with DOB and ESO, in order to illustrate their approximate equivalence to GIS.

This paper deals with the conflict between the input–output response and the disturbance–output response, which cannot be completely eliminated by traditional and advanced control strategies without using the accurate process model. The inherently close association of these two responses and the unavailability of the accurate process model pose a great challenge to field test engineers of a coal-fired power plant, that is, the design requirements of reference tracking and disturbance rejection are compromised. In this paper, a novel two-degree-of-freedom controller—feedforward compensated (FC) desired dynamic equational (DDE) proportional–integral–derivative (PID) (FC-DDE PID)—is proposed as a viable alternative. In addition to achieving independent reference tracking performance and disturbance rejection performance, its simple structure and tuning procedure are specifically appealing to practitioners. Simulations, experiments, and field tests demonstrate the advantages of the proposed controller in both reference tracking and disturbance rejection, thus making FC-DDE PID a convenient and effective controller for the control of the coal-fired power plants, readily implementable on the distributed control system (DCS).

Purpose The modern missile has low uncertain and wide range vibration frequency. The conventional notch filter with the fixed notch frequency is less effective than that of the adaptive notch filter (ANF) in vibration suppression for the time-varying vibration frequency. Design/methodology/approach To overcome the drawback, a novel method is based on frequency estimators made by interpolation of three discrete Fourier transform (DFT) spectral lines. The modified frequency estimators based on the interpolation of three DFT spectral lines are presented to identify and track the vibration frequency. Then the notch frequencies of multiple ANFs are real-timely tuned according to estimators. Findings Finally, taking the second-order flexible missile as an example, the performance of the proposed method is verified. The verified simulation results show that multiple ANFs are effective in vibration suppression. Practical implications Cascading multiple ANFs to achieve multi-order vibration suppression is more efficient and feasible than conventional fixed-parameter notch filtering. Originality/value The frequency estimation method based on three DFT spectral lines proposed in this paper can effectively identify and track signals in the noise environment. Compared with conventional methods, the method pretended in this paper has high identification accuracy and a stronger ability to track signals. It can meet the fast frequency identification requirements of the actual flexible missile.