Study On Hydro-Viscous Drive Speed Regulating Start And Control Technology

A hydro-viscous drive speed regulating start equipment transfers power by shearing force of oil film between friction discs, so as to realize the controllable startup process of mechanical equipment. It has great significance both in reducing manufacturing & operating cost and in prolonging servicing life of mechanical equipment. With belt conveyor as application object, the research work on hydro-viscous drive speed regulating start and control technology has been carried out.This paper discusses the engineering background, significance, basic principle and superiority of hydro-viscous drive speed regulating start, analyzes domestic and abroad research status, points out current problems of hydro-viscous drive speed regulating start, and presents research contents of this thesis.The mechanism of hydro-viscous drive speed regulating start is deeply studied. Since speed regulating start is a transient process and the oil film thins out gradually during the whole startup process, the effect of oil film squeezing cannot be neglected. With a comprehensive consideration of oil film squeezing effect, the effect of friction disc surface roughness and centrifugal force of the oil film, the modified transient Reynolds equation has been established. At the same time, the thermal energy equation and the temperature-viscosity equation have also been set up. The numerical calculation finite element model has been built to simulate the variation of oil film thickness, transmission torque, load capacity, pressure field and temperature field of the oil film. From the simulation results, the effect rules of the oil film squeezing, cross-section sizes and distribution of friction disc surface grooves, friction disc surface roughness and working oil temperature rising caused by the friction pair on transmission torque and load capacity are obtained.The dynamic balance equation of the friction discs are established on the basis of force analysis. Flow balance equation of the hydraulic control system and dynamic balance equation of load are also built. Dynamic characteristics of the proportional relief valve used in the testing system are studied experimentally and its transfer function is set up. According to the characteristics of the speed regulating start, transfer functions of the proportional pressure control system and the proportional flow control system are established respectively. The dynamic response characteristics of the two systems are analyzed and compared. The results show that the proportional pressure control system is more suitable for speed regulating start of belt conveyor.Speed regulating start characteristics of the PID control and the PID optimal control are deeply studied with the Harrision starting speed curve. The results show that the both cannot meet the demands of speed regulating start of belt conveyor. The output speed lags behind the given speed and there are fluctuations in output speed. On this basis, the fuzzy PID cascade control is presented and its dynamic response characteristics are analyzed. The Harrision starting speed curve is also simulated. The results show that the output speed can track the given speed more accurately and there are no fluctuations in output speed. It indicates the fuzzy PID cascade control is suitable for speed regulating start of belt conveyor.To verify correctness of theoretical analysis and effectiveness of control strategy, the experimental equipment of hydro-viscous drive speed regulating start has been built. By using a PLC, the experiments have been carried out to verify the PID and the PID optimal control effect. The fuzzy PID cascade control effect is verified by using a singlechip. The experimental results show that the fuzzy PID cascade control can meet the demands of speed regulating start of belt conveyor. Not only the output speed can track the given speed more accurately, but also there are no fluctuations in the output speed. It also proves the correctness of the theoretical analysis. The effects of working oil temperature, load and starting time on speed regulating start have also been studied experimentally.