Research On Driving Force Distribution Of Electric-Driven High-Clearance Tractor

Electric-driven high-clearance tractor has multiple advantages, such as environmental protection, energy saving, safety, etc. As one of the effective approaches to solving environmental pollution and energy wastage problems caused by agricultural machines, it has become an important orientation of the agricultural machines’ development in the future. Based on the completion of the structural design on theory of electric-driven high-clearance tractor, this paper carries out research on the driving force distribution strategy and conducts related mathematical modeling and simulation.Pertinent to the high-clearance tractor’s shortcomings in structural performances, such as the fixed ground clearance and wheel span, single drive and rotation method and so on, the author proposes the structural design plan of the electric-driven high-clearance tractor characterized with independent four-wheel drive, independent four-wheel rotation, adjustable ground clearance and adjustable wheel span in the paper. Through comparing the performances of the motors of the four vehicle motors, the author determines the use the PMSM (Permanent Magnet Synchronous Motor, PMSM) as the drive motor and confirms the rated power, maximum torque, reduction ratio and other parameters of the motor as well as the completed vehicle’s power supply mode according to the high-clearance tractor’s completed vehicle design parameters and its motor performance indicators.The author also carries out theoretical analysis on PMSM and its control system as well as vehicle dynamics, and then establishes PMSM and the simulation model of the control system, simulation model of the tractor’s longitudinal dynamics, simulation model of wheels and tires in Matlab/Simulink respectively. The simulation results of PMSM control system indicate that the control effect of vector control-current hysteresis band PWM method is sound. Motor’s torque respond quickly and has high dynamic precision, which can fully meet the performance characteristics of electric vehicles.According to the main functions that the driving force control system should complete, the author puts forward the layered control system of the driving force control system of four-wheel independent electric-driven high-clearance tractor and clarifies the specific functions that every layer of the control method should complete. In accordance with the functional goals of the four-wheel torque distribution layer, based on deepening into the idea of distribution control with the optimal economical efficiency and the principle of driving force distribution control, the author formulates the simple and effective economic distribution control strategy and ASR (Acceleration Slip Regulation) strategy.The author also develops the control system simulation platform of the four-wheel independent electric-driven high-clearance tractor, and analyzes the distribution control with the optimal economical efficiency and ASR strategy under the operating conditions of possessing the uniform adhesion coefficient and separating from the ground. The simulation results show that:on the road whose adhesion coefficient is 0.8, when the tractor keeps the accelerator pedal opening at 12.5%, under the economically optimized distribution control mode, the drive system efficiency can be increased by 48%; On the road whose surface adhesion coefficient is 0.2, when the tractor keeps the accelerator pedal opening at 100%, under ASR mode, the traction force can be increased by 79.17% and the speed can be increased by 88.51%. It means that the distribution control strategy based on optimal economical efficiency can obviously improve the economy of high-clearance tractor in the driving process and that ASR strategy can effectively improve the power and traction performance of the high-clearance tractor.