设施园艺移动平台分布式驱动自适应防滑控制

针对设施园艺特殊作业场景对电驱移动平台灵活作业与高操纵稳定性需求，该研究设计了一种四轮轮毂电机独立驱动的分布式设施园艺电驱移动平台，并提出了一种可提高转向灵活性与稳定性的自适应防滑控制策略。在该控制策略中，首先构建电驱移动平台动力学模型与Ackermann差速转向模型，结合速度瞬心原理及轮胎侧偏角确定各车轮转向目标转速；其次，为提高电驱移动平台对时变附着系数的适应能力，采用改进的强跟踪自适应无迹卡尔曼滤波算法设计复杂路面识别器，实现对路面附着系数准确估计；最后，设计基于自适应滑模算法的防滑控制器，根据路面附着系数估计值确定车轮相对最佳滑转率并实时控制滑转率。为验证所提控制策略的有效性，开展了Carsim-MATLAB/Simulink联合仿真与分布式设施园艺电驱移动平台实车试验。试验结果表明，所提控制策略可准确估计复杂道路下路面附着系数，降低车轮滑转率误差；在不变路面、对接路面与对开路面3种工况下，左侧车轮滑转率误差分别为0.031、0.015和0.038，右侧车轮滑转率误差分别为0.026、0.005和0.028；在不变路边随机路面实测路况下，电驱移动平台路面附着系分别数约为0.44和0.47，最大滑转率分别约为0.69和0.68，有效抑制了轮胎转向时的过度滑转，提高了电驱移动平台的行驶稳定性。研究可为设施园艺车辆驱动防滑控制提供具体理论依据和实施方案。

Distributed drive adaptive skid control of facility horticulture mobile platform

Flexible operation and high handling stability are often required in the distributed electric drive mobile platform in special scenarios of facility horticulture. This study aims to design a mobile platform with distributed electric driven independently by four-wheel hub motors. An adaptive anti-slip control strategy was also proposed to improve the steering flexibility and stability. The dynamic model and Ackermann differential steering model were constructed for the distributed electric drive mobile platform. The target steering speed of each wheel was determined to combine the instantaneous center of speed and tire side deflection angle. Then, the time-varying adhesion coefficient was selected to improve the adaptability of the distributed electric drive mobile platform. A complex road identifier was designed using strong tracking adaptive untracked Kalman filter, in order to accurately estimate the road adhesion coefficient. Finally, an anti-slip controller was obtained with adaptive sliding mode. The optimal wheel slip rate was determined, according to the estimated road adhesion coefficient and control the wheel slip rate in real time, Finally, the self-adaptive anti-slip control was realized for the drive wheel of the distributed electric drive mobile platform in the facility horticulture scene. Both Carsim-MATLAB/Simulink co-simulation and vehicle tests of the distributed horticultural electric drive mobile platform were carried out to verify the effectiveness of the control strategy. The simulation results show that the estimated errors of the wheel to road adhesion coefficient were 0.009 and 0.033 on the unchanged and docked road surfaces, respectively, while 0.01 and 0.007 on the opposite road surfaces for left and right wheel, respectively; When using anti-slip control, the slip rate errors of the left wheel were 0.031, 0.015, and 0.038, respectively, and the slip rate errors of the right wheel were 0.026, 0.005, and 0.028, respectively. The test results show that the maximum slip rates of the left front, right front, left rear, and right rear wheels without anti-slip control were 0.80, 0.85, 0.90, and 0.93, respectively, indicating severe wheel slip. Under the same road conditions, there was a significant deviation in the wheel slip rate between adjacent moments, resulting in the slipping at all times unsuitable for the stable driving of the mobile platform. The adaptive anti-skid control with road recognition can be expected to accurately estimate the wheel road adhesion coefficient on complex roads, thus reducing the error of wheel slip rate. The overall estimated values were around 0.44 and 0.47 for the four-wheel road adhesion coefficient after the stable starting of the mobile platform. The maximum slip rates of the controlled wheel under two tested road conditions were approximately 0.69 and 0.68, respectively. The tire slip was greatly reduced during turning, in order to effectively improve the driving stability of the mobile platform.