## 5 Conclusions  
This paper analyzes the mathematical model of the MCCS system, and establishes a simulation model based on AMESim. According to the application scenario of the MCCS system, a master and auxiliary composite control strategy with variable universe fuzzy PID as the primary control is proposed, a co-simulation platform based on LabVIEW and AMESim is built, and the master and auxiliary composite controller is designed. Combining simulation and experimental testing, the following conclusions are obtained.  
By comparing the data of the experiment and the simulation model, the accuracy of the AMESim model is verified from the two aspects of the constant flow and the unsteady flow of the MCCS system.  
The main controller's precision and adaptive ability are improved by using the idea of the variable theory domain. A master and auxiliary composite control strategy is proposed, which further increases the anti-interference ability of the control system, especially the peak clipping ability of the pressure peak caused by the common switching condition of the MCCS system.  
According to the co-simulation technology, a co-simulation platform based on LabVIEW and AMESim is built, which can realize the switching of working conditions, the pressure adjustment of each channel, the setting of control parameters, and the data acquisition, processing and storage. It has good operability and an excellent human-computer interaction interface. Through the analysis and comparison of different control schemes, the effectiveness of the main and auxiliary compound control strategies is verified, and the controller parameter values are initially obtained, which reduces the workload of subsequent tests.  
The experimental results showed that compared with adaptive fuzzy PID and variable universe fuzzy PID control methods, the main and auxiliary compound control strategy has a strong anti-interference ability, a fast dynamic response speed, high stability and a good peak shaving effect.  
The results presented in this work can be used to guide the design and operation of the control system of the MCCS device, meet the stable and continuous requirements of the water supply system, and improve the efficiency of fire water supply. Of course, the research in this paper has certain limitations. The proposed master and auxiliary composite control strategy is only for pressure fluctuations caused by switching operating conditions. The next research direction of this paper will continue to improve the control scheme and expand its applicable working conditions.  
Conceptualization, G.Z. and W.L.; methodology, G.Z.; software, G.Z.; validation, G.Z., J.W., J.Z. and W.L.; formal analysis, G.Z.; investigation, G.Z.; resources, J.W. and W.L.; data curation, G.Z.; writing--original draft preparation, G.Z.; writing--review and editing, J.W. and J.Z.; visualization, G.Z.; supervision, J.W. and W.L.; project administration, J.W. and W.L.; funding acquisition, W.L. All authors have read and agreed to the published version of the manuscript.  
This research work was supported by National Key R&D Program of China, grant number 2016 YFC0802900, and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, Top-noch Academic Programs Project of Jiangsu Higher Education Institutions.  
The authors declare no conflict of interest.