农用柔性底盘前轮转向动力学研究

农用柔性底盘通过偏置转向轴转向,4个独立的电动轮既要用于行进,又要驱动转向,控制难度大.为探明柔性底盘前轮转向过程的转向特性,建立了7自由度整车动力学模型,并通过Matlab/Simulink软件建立相应的交互控制仿真模型,进行了不同车速下单轮驱动转向与双轮比例控制转向的仿真与分析,根据仿真结果制定了控制策略;在此基础...

Dynamics Research on Front Wheel Steering of Agricultural Flexible Chassis

The agricultural flexible chassis (FC) is a four wheel hub motor independent drive, and four wheel omni-directional independent steering chassis. Its structure is very simple, even the steering motors used in the ordinary steer-by-wire system are cancelled. It steers through an offset steering shaft mechanism. It is very flexible and can realize special movements such as four-wheel steering, in-situ turning and lateral driving. The four independent electric wheels are used for both driving and steering, which increases the difficulty of control. In order to explore the steering characteristics of the front wheel steering process, a seven degree of freedom vehicle dynamics model was established. Based on this model, combined with the control system, a simulation model capable of interactive control was established through Matlab/Simulink software. Simulation and analysis of single-wheel drive steering and two-wheel proportional control steering at multiple vehicle velocity were carried out. Electronic control hardware and software systems of actual vehicle were designed. According to the steering characteristics obtained by the simulation and the control characteristics of the in-wheel motor, a control method was developed. Real vehicle steering tests at multiple vehicle velocity were carried out and corresponding simulations were performed. There was a strong coupling effect between the two steering wheels. The key factor causing the coupling effect was the tire aligning torques caused by the deviation of the steering angle of the two wheels from the Ackerman steering geometry, and this aligning torques prevent the deviation. The greater the deviation was, the greater the aligning torque was, and vice versa. The front wheel steering system had strong nonlinearity. When the steering angle was the same, the wheel drive torque required during the steering process was proportional to the square of the vehicle velocity. The simulation results of steering were in good agreement with the measured results. This research can provide a simulation platform and theoretical basis for the research and formulation of general control strategies for front-wheel steering.