Study On Comprehensive Control Strategy Of Tractor Hydraulic Mechanical Transmission

Aiming at the problem of efficiency and response lag of HMT transmission,combined with the complex and changeable working environment of tractor,the integrated control strategy of HMT transmission is studied in this paper.The main works are as follows:The speed ratio law for maximum driving power of tractor is determined.Firstly,the efficiency calculation model of HMT is established,the relationship between the efficiency of pump-motor of HMT and displacement ratio of variable pump,speed and pressure of hydraulic system is established.Then from the point of view of tractor driving power optimization,considering the influence of HMT transmission efficiency,the objective function and constraints for obtaining the optimal dynamic speed ratio are determined,the traversal optimization algorithm is designed and implemented to obtain the optimal speed ratio law under varies tractor working conditions.Finally,a simulation model is established to compare the speed ratio laws before and after optimization.The simulation results show that the optimized speed ratio control law improves the tractor's dynamic performance compared with the traditional optimal dynamic speed ratio law.A HMT speed controller based on control algorithms is proposed.Considering that the actuator of HMT transmission is a pump-motor hydraulic system.To overcome the problem of hydraulic system,the conventional PID control is improved and optimized by using the wavelet neural network algorithm and the fuzzy adaptive algorithm,the wavelet neural network PID control and the fuzzy PID control are designed respectively.Simulation models are established to simulate and compare the two control methods.The simulation results show that the wavelet neural network PID control has better adaptability,stability and control accuracy.Finally,the wavelet neural network PID control method is selected as the method of HMT variable speed control.An integrated control strategy of engine-HMT based on working resistance estimation is proposed.Firstly,based on the working pressure of the hydraulic speed regulating system,an estimation model of tractor working resistance is established.Then,a throttle compensation module based on the estimation of working resistance is designed and implemented based on the fuzzy recognition algorithm.By actively compensating the engine throttle,the tractor can respond quickly when the working resistance changes.A simulation model is established to simulate and compare the engine-HMT integrated control strategy and single HMT speed control strategy.The simulation results show that the engine-HMT integrated strategy improves the stability of the tractor speed,guarantees the working efficiency of tractor and has a certain significance to improve the tractor's ability to adapt to complex working conditions.