A unified design for feedback-feedforward control system to improve regulatory control performance

Abstract

The PID controller is widely used in industries because of its simplicity and robustness. A simple approach to improve regulatory control performance is to combine both feedback PID and feedforward controllers. The feedforward controller enables early compensation of a measured disturbance before it can seriously affect the process. The conventionally derived non-ideal feedforward controllers are not often used in practice. The reason is that an ideal feedforward controller based on direct inversion of process model is often not physically realizable. Several non-ideal feedforward control designs have been proposed where some of them involve rather intensive tuning procedure to obtain good disturbance rejection. In this paper, we present a new systematic method for designing a combined feedback-feedforward control system. The proposed design method is easy to use and applicable to stable, unstable and integrating deadtime processes where the ideal feedforward controller is physically not realizable.

Attitude control for astronaut assisted robot in the space station

“…Then, the Matlab/Simulink is used to build up the control system simulation platform. Finally, the rationality of the designed robot's structural dynamics and the control effect of PIDNN controller are validated by conducting the dynamics co-simulation [32,33].…”

Simulation and control of water-gas shift packed bed reactor with inter-stage cooling

“…MSC feedforward-feedback control strategy Figure 5 illustrate the block diagram of the proposed feedback-feedforward control structure based on the multi-scale control (MSC) scheme [9]. The feature that distinguishes this MSCbased feedback-feedforward (MSC FB-FF) control structure from the conventional one (figure 4) is that the MSC-FB/FF treats the measured disturbance D as though it is an input disturbance introduced directly into the fast inner-loop of the MSC control system.…”

“…In this way, the effect of disturbance D on Y is mainly removed by the fast inner-loop sub-controller K 1 . The details of the MSC-FB/FF control strategy can be obtained from [9]. In figure 4, the transfer function from U f f to U is given by…”

“…One can derive an equivalent MSC-based feedforward controller as follows: Equation (19), F * ss denotes the optimised static feedforward controller while F msc denotes the MSC-based feedforward controller, i.e., the subscript msc is used to differentiate it from the conventional feedforward controller in figure 4. The formula for obtaining static the feedforward is obtained via the proposed method in [9].…”

“…Even so, feedforward controller only rejects a specific measured disturbance and not all of the disturbances that occur in a process. For this reason, it is a common in industry that the feedforward controller is used together with feedback control system against certain disturbances [9]. Interestingly, both the feedback and feedforward controllers can be effectively designed based on the recently proposed multi-scale control (MSC) scheme in [10].…”