四轮轮毂电机驱动农用无人车差速转向建模与分析

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 selfdeveloped 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.