The Full Power Shift Control Of Hydro-mechanical Continuously Variable Transmission Based On The Estimation Of Load

Hydro-mechanical variable transmission is a dual power flow compound transmission system with the characteristics of high mechanical transmission efficiency,large transmission power and stepless speed variation of hydraulic transmission,and is suitable for engineering vehicles and high-power vehicles.In this paper,the two-stage hydraulic-mechanical variable transmission is taken as the research object,and the estimation method of closed-loop hydraulic circuit pressure and the displacement control method of HMT are proposed,which are helpful to complete the HMT full-power shift control technology and improve the quality of the shift process.The main research contents include:(1)The working principle of the closed-loop hydraulic circuit is analyzed.Combining the hydraulic dynamic viscosity model and the hydraulic component leakage model,the estimation model of closed-loop hydraulic circuit pressure of two ranges are established based on the relationship between the volumetric efficiency of the hydraulic component and the total volumetric efficiency of the hydraulic circuit.(2)The estimation test of closed hydraulic circuit pressure is designed and carried out under different rotation speed,hydraulic pressure and displacement conditions,the effect of leakage coefficient on hydraulic circuit pressure is explored.The indirect estimation method of hydraulic circuit pressure based on look-up table,the indirect and direct estimation method of hydraulic circuit pressure based on neural network are proposed,the accuracy and relative error of the three methods are compared.(3)The structure and working principle of the hydraulic-mechanical displacement control system are analyzed,a mathematical model of the displacement control system is established,the reversibility of the displacement control system is verified,and the neural network is applied to establish inverse models of the displacement control system of the displacement increase process and the displacement decrease process,the hydraulic-mechanical displacement control method is proposed based on direct inverse control and is able to achieve accurate adjustment of displacement ratio.The simulation ofthe displacement control system between the hydraulic section and the hydraulic mechanical section under different required displacement ratios was carried out to verify the accuracy of the inverse displacement control method.Precise adjustment of displacement ratio can be achieved by the displacement inverse control method,which is proposed in this paper.