Active disturbance rejection controller (ADRC) has achieved soaring success in motion controls featured by rapid dynamics. However, it turns obstreperous to implement it in the power plant process with considerable time-delay, largely because of the tuning difficulty. To this end, this article proposes a quantitative tuning rule for the time-delayed ADRC (TD-ADRC) structure based on the typical first order plus time delay (FOPTD) model. By compensating the FOPTD process as an integrator plus time delay in low frequencies, the gain parameter of TD-ADRC can be related to a scaled time constant which shapes the closed-loop tracking performance. Bandwidth parameter of extended state observer is scaled as a dimensionless parameter. A sufficient stability condition of TD-ADRC is theoretically derived in terms of the scaled parameter pair, the range of which falls within the practical interest. Relative delay margin is revealed as a critical robustness metric among others, a default pair of scaled parameter setting is recommended as well as an explicit retuning guideline according to the user's preference for performance or robustness. Simulation and laboratory water tank experiment validate the tuning efficacy and a coal mill temperature control test depicts a promising prospective of the proposed method in process control practice.

This paper aims to propose a quantitative tuning method for active disturbance rejection control (ADRC) that controls the K/(Ts+1)n-type high-order processes. An asymptote in the Nyquist curve has been observed for the first time and its mathematical expression has been deduced. An asymptote condition is provided in order to derive a parameter tuning rule under the sensitivity constraint. Although this proposed tuning rule is originally designed for a certain type of high-order processes, it can be extended to other types processes that can be approximated into the form of K/(Ts+1)n. Comparisons with different PID control strategies have been conducted for a range of cases to demonstrate the efficiency of the proposed tuning method. Finally, the effectiveness of the proposed tuning rule is experimentally verified on water tank system that exhibits high-order dynamics. Field tests on the superheater steam temperature control of a circulating fluidized bed (CFB) power plant further demonstrate its potential for applications in complex industrial processes.

Several improved active disturbance rejection control (ADRC) methods, including input modified ADRC (MADRC), input delay ADRC, Smith predictor-based ADRC, and Smith-like based ADRC (SLADRC), have been proposed to tackle $\boldsymbol{K/(Ts+1)^{n}}$ -type high-order processes. This article aims to investigate their control performance theoretically, such as the input disturbance rejection and measurement noise rejection capabilities. It is proved that these improved ADRCs with the same parameters have the same measurement noise rejection capability. Besides, quantitative tuning rules of MADRC and SLADRC are derived based on their desired dynamic equations. Compared with proportional-integral controller and regular ADRC, their effectiveness is verified by comparative simulations and experiments, where MADRC obtains the best control performance with good robustness. Finally, the successful field applications of MADRC on the main steam pressure process further illustrate its application potential in complicated industrial processes.