## 1 Introduction
[11] adopt fuzzy adaptive PID control to realize the stable control of grouting pressure with uncertain, time-varying and nonlinear characteristics, and its performance indicators are better than traditional control methods. In reference [12], a fuzzy PID controller is designed to control the steam temperature of the supercritical lignite boiler, and its excellent response speed and stability are verified through simulation. References [13; 14] introduce the idea of a variable theory domain on the basis of a fuzzy PID control, which overcomes the shortcoming of the limited control rules of a fuzzy PID controller, further increases the controller's adaptive ability, and improves the dynamic characteristics of the control system. In addition, references [15; 16; 17] use variable universe fuzzy PID control in different applications, and the control effect is significant. In practical applications, the MCCS systems have common control system characteristics, such as non-linearity, hysteresis and parameter uncertainty, but also have their own unique load dynamic changes, channel switching disturbance and other system characteristics caused by the actual working conditions. Therefore, the multi-controller compound control is proposed by researchers, which is suitable for more complicated control systems or devices with higher control accuracy requirements. For example, reference [18] proposes a control method combining fuzzy PID and implicit generalized predictive control. Simulation experiments show that it can reduce the variation amplitude of the main steam pressure in the marine steam power system during the dynamic change process, and improve the response speed. [PERSON] et al. [19] propose a control strategy that is a combination of a fuzzy sliding film controller and a linear controller for the speed control of dual-mass drives, which has been verified by experiments and simulations. [PERSON] et al. [17] propose a new type of double closed-loopcontrol, chaos optimization and adaptive fuzzy PID compound control strategy for variable spray systems with large inertia, large hysteresis, nonlinearity, etc., and a satisfactory control effect is obtained through experimental verification. In reference [20], a compound controller based on fuzzy logic is proposed for the steam supply system of a nuclear power plant. Two local controllers are coordinated according to the working conditions based on the neural network PID controller and the fuzzy controller. The simulation results show that the control effect is a smoother and more stable operating performance. In this paper, based on the change law of pressure in the process of MCCS switching, a master and auxiliary control strategy is proposed. On this basis, a co-simulation platform is built to verify the effectiveness of the proposed control strategy, and the effectiveness of the proposed control strategy is compared with that of the single fuzzy PID and the single variable theory domain fuzzy PID control. The advantages of the proposed composite control strategy are verified. The control strategy is tested and verified on the test bench, which further proves that the main and auxiliary compound control based on the variable universe fuzzy PID control can effectively optimize the pressure change of the main pipe. The paper is organized as follows. In Section 2, we build a research platform and co-simulation platform of the MCCS system. In Section 3, we design the master and auxiliary compound controllers. Then, in Section 4, we give simulation results and experimental results to demonstrate the superiority of the compound control strategy compared with single control. Finally, in Section 5, we summarize this paper.