| Recently, the development of our national economy advances rapidly, but the energy waste is serious, product energy consumption is higher than 40% of world average level. It has great significance to the sustainable development of our country by improving the utilization ratio of energy relying on technical progress. Associating with the special subject "Key Technological Research on Hydrodynamic Variable Speed and Saving Energy of Large Pump and Fan" of the National High-tech Research Development Plan (863), mathematical model of hydrodynamic coupling is established through analyzing dynamic characteristics of hydrodynamic coupling in this paper. Based on uncertainty of the mathematical model fuzzy-PID dual-mode control strategy is used to realize rapid and exact automatic control of the speed of hydrodynamic coupling.Most pumps and fans used in industrial production have characteristics such as high speed, great power, high energy consumption and periodical output. It can save a lot of energy to instead of backward throttle governing which is high energy loss. by using fluid coupling. At present, manual openloop control is used more in the speed control system of hydrodynamic coupling, which can not realize the accurate regulation to hydrodynamic coupling and meet the need of automation. Dynamic regulation features of the speed control system of hydrodynamic coupling is analyzed in this paper, and the research is conducted to the speed regulation process of hydrodynamic coupling which is divided into liquid-filled process and variable speed process to get the speed regulation dynamic equation. And the speed control system of hydrodynamic coupling is seen as non-linear system composed of many linear systems with variable parameters. In the speed control system, manual openloop control is used more, and in the loop-closed speed adjustment system of hydrodynamic coupling, PID control is used more. Because PID control over-relies on the exact mathematical model of hydrodynamic coupling, and the flow state of working flow is complex, it is difficult to establish exact mathematical model, so the control effect of PID control to speed regulating of hydrodynamic coupling is not good enough, which affects the speed control and energy saving effect of the whole system. The fuzzy control has high robustness, but its control precision is not high, the stability is not good. Because the PID and fuzzy control can not meet the speed control system of hydrodynamic coupling well, so it effects the results of speed control and energy saving. In this paper, fuzzy-PID control strategy is used in the speed control system of hydrodynamic couplingIn this paper, aiming at the speed control system of hydrodynamic coupling, some research is conducted as follow:(1) The theory of speed control and saving energy of speed control of hydrodynamic coupling are analyzed, and the result shows that it has actual significance to the speed control of hydrodynamic coupling in the aspect of saving energy(2) In this paper, YOCQz420 variable speed hydrodynamic coupling used in the speed adjustment of fan is used as model. The dynamic process of speed control of hydrodynamic coupling is divided into liquid-filled process and variable speed process. Under the condition of some hypothesis and linearization in a small range, analysis is conducted to dynamic characteristics of variable liquid filled content and speed control, then dynamic adjusting equation of speed control system of hydrodynamic coupling is derived. The speed control drive function of hydrodynamic coupling is composed of variable-parameter inertia link and delay linkage.(3) After considering the characteristics of dynamic adjustment performance of the hydrodynamic coupling speed control system as well as the advantages and disadvantages of fuzzy, PID control strategy, fuzzy-PID control strategy is used in the speed control system of hydrodynamic coupling. According to the composition of fuzzy and PID control system as well as working principle, fuzzy controller and PID controller are designed, and model switcher is established.(4) In Simulink of MATLAB, model of fuzzy-PID dual-mode control system of YOCQz420 variable speed hydrodynamic coupling is established, simulation analysis is conducted by comparing fuzzy-PID dual-mode control system and single PID control system. The result shows that fuzzy-PID dual-mode control strategy is better than single PID control in aspects such as strategy response speed , overshoot, steady state accuracy and so on, so it is more reasonable to use fuzzy-PID dual-mode control strategy in the speed control of hydrodynamic coupling. Fuzzy-PID dual-mode control system is simulated through taking different threshold, and the effect of threshold on control efficacy is studied. In this paper, fuzzy-PID dual-mode control theory is used in the speed control system of hydrodynamic coupling, which provided a new choice for the control method of speed control of hydrodynamic coupling.
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