Design and performance analysis of drive system for high clearance self-propelled corn detasseling machine

Abstract: A hydrostatic drive system scheme for the high clearance self-propelled corn detasseling machine was proposed and the dynamic performance of the system was simulated and tested in this paper. Although detasseling machines have much higher working efficiency than manual detasseling, they have just been used for a few years in China and mostly were imported from abroad at a high price. Since the machine demanded a high ground clearance, the closed volumetric speed control loop with one pump and four motors was adopted. The engine directly drives the pump to output high pressure fluid to the four-wheel motors, and then the motors drive the hub reducers to turn the wheels. It can be concluded that the vehicle can achieve 3 gears of I, II and III by choosing the appropriate maximum and minimum displacements of motors and reducer gear ratios. To better analyze the performance of the drive system, a detasseling machine model with 15 degrees of freedom was built according to the vehicle structure features. The vehicle model included vehicle body model, wheel model and four-wheel independent suspension system model. Meanwhile, the mathematical model of the hydrostatic drive system was derived, which included pump model, motor model and reducer model. Then, the simulation model of vehicle dynamics of detasseling machine was presented using the software Matlab/Simulink based on the mathematical models. The simulation model was used to study the performance of speed and system pressure of the vehicle at 3 gears. And the results showed that the vehicle could get a maximum travel speed of 15.8, 19.7 and 26.1 km/h, and a steady system pressure of about 6.29, 7.30 and 8.94 MPa at the 3 gears of I, II and III, respectively, which could meet various application conditions. As a special component of detasseling machine, the effect of the suspension system on the drive system was testified. By exerting a road excitation on one wheel, the system pressure of the vehicle with the suspension was contrasted with the one without suspension. The results showed that the pressure of the one with the suspension fluctuated much narrower and smoother than the other, which meant the suspension could effectively improve the performance of the drive system. To verify the mathematical model and to further research the drive system, a high clearance self-propelled corn detasseling machine was designed to conduct the tests. During the process of changing the displacement of pump from the minimum to the maximum value at each gear, the maximum travel speed was recorded, and the variations of the inlet and outlet pressure of the pump and motor were measured. The main test devices contained oil pressure sensors, acceleration sensors, data acquisition card of National Instruments, switching power supply and laptop, and the software LabVIEW was used for data processing. The vehicle tests showed that with the increase of pump displacement, the system pressure of the high pressure side first trended to increase sharply and then decreased to a stable value of 6.361, 7.286 and 8.717 MPa at the 3 gears of I, II and III, respectively, which was consistent with the simulation results. And the pressure of the low pressure side was about 2.4 MPa, which was equal to the system charge pressure. In addition, the maximum driving speed of the machine at the 3 gears was 15, 19 and 24 km/h respectively, which was lower than the theoretical values. That was mainly due to the leakage loss of hydraulic components and the mechanical friction loss. The simulation and test results showed that the vehicle drive system had a rapid response and a good performance, and the correctness of the mathematical model of the machine was also verified. The study can provide a technical reference for the independent research and development of the high clearance self-propelled corn detasseling machine in China.