Abstract: Slip phenomenon makes it difficult to establish the kinematic model of skidsteered vehicle. In order to accurately analyze the turning characteristics of a skidsteered unmanned ground vehicle (UGV）, based on the assumption of large turning radius, a two degrees of freedom kinetic model was established, and the relation between the speed difference of inner and outer wheels, and the turning radius was analyzed under ideal conditions. The experiment was carried out by selfdeveloped agricultural unmanned vehicle driven by fourwheel hub motor, the characteristic parameters of the speed of the real vehicle differential steering and driving path were measured by hall sensors and an Inertial Navigation System (INS) with a high accuracy. It was analyzed that the existence of slippage phenomenon led to the fact that the speed difference between the inner and outer wheels was not equal to the real speed difference, and the curve fitting equation between them was obtained, and corresponding error coefficient was introduced to modify the kinematic model. The results showed that the realtime turning radius could be calculated by combining the fourwheel speed with the kinetic model, considering the slippage phenomenon, the average absolute error was 4.033% and the maximum error was 6.715%, which could effectively guide the deadreckoning of the UGV.

Key words: unmanned ground vehicle (UGV), array hub motor, skidsteered, turning radius

摘要： 滑移现象的存在对差速转向车辆运动学模型的建立造成困难。为准确分析无人车的差速转向特性，基于大半径转弯前提，建立无人车的二自由度差速转向运动学模型，分析理想情况下内外侧车轮速度差与转弯半径之间的关系。并使用自主研制的四轮轮毂电机驱动农用无人车进行试验，通过高精度霍尔传感器和惯性导航系统测量实车差速转向时的行进速度和行驶路径等参数，分析出存在的滑移现象导致转弯时内外两侧车轮转速差大于车轮处真实速度差，计算得到二者之间的拟合方程，并引入误差系数对模型进行修正。结果表明：在考虑滑移现象的情况下，将四轮速度与运动学模型相结合，可计算得实时转弯半径大小，平均绝对误差为4.033%，最大误差为6.715%，可有效指导无人车的航路推算。

关键词: 无人车, 阵列式轮毂电机, 差速转向, 转弯半径