The Study On The Design Of Hydrostatic Mechanical Transmission And Speed Control System

Hydromechanical variable-speed drive is a new type of transmission mode, which develops quickly in our country and represents the advanced level of today's vehicle transmission technology. It adopts hydraulic and mechanical double power flows. The output power is high and the variable-speed drive can be controlled flexibly and conveniently. The proper transmission design makes the hydraulic power dividing ratio small and the system efficiency high. It is of high power, economy and high exhaust capability compared with the step speed change mechanical transmission and hydraulic machine auto-transmission. Therefore, this paper presents a systematic theory analysis and emulation study on hydromechanical variable-speed drive.The paper describes in detail the current development situation of variable-speed drive both at home and abroad and analyzes the main problems existed in variable speed drive. It also describes the performance features of the hydromechanical variable-speed drive through analysis. Principles of the hrdromechanical variable-speed drive are studied, and relation between power dividing flow transmission structure parameters and efficiency is analyzed. System transmission plan is design on the basis of theoretical analysis. And the laws of the power flow varies with the load on each working condition are analyzed. A power dividing automobile variable-speed system is put forward. The system is composed of a set of variable-speed drives with adjustable exhaust volume, a set of epicyclic train and a clutch. Characteristics of hydraulic system speed regulating loop are analyzed, which proves the system feasibility theoretically. And the hydraulic system is designed.By considering the high order nonlinearity of the vehicle system, coupling effectiveness of input and output, complicated working conditions of vehicle operation and external interferences, a PID computation method is put forward for speed ratio control of variable-speed system. And dynamic computer emulation is done under MATLAB by combining the system mathematic model. Emulation result shows that the system is simple and the dynamic performance is stable. System response quickly and no over-regulating occurs. Basic purpose of this subject is reached. The research indicated that HMCVT for vehicles, which has high performance-cost-ratio, has strong competition advantage relative to conventional mechanical mufti-gear transmission. As a new product, it has good application prospects.