Terrain Truck: Control of Wheel Rotational Velocities and Tire Slippages

The dynamics of an AWD vehicle is determined by the interactions between the vehicle's wheels and the tire contact surface. Understanding and controlling these interactions drives the vehicle mobility and energy efficiency. In this paper new issues related to tire slippage control are addressed. The paper analytically demonstrates that two tires on the same axle with the same rotational speeds can have different slippages when the normal reaction and inflation pressure vary due to motion conditions. Hence, a new method is proposed to control the rotational velocity of the wheels in a way that provides the same slippages of the tires by accounting for changes in the normal load and tire inflation pressure. This approach is especially beneficial for vehicles with individual (electric) wheel drives which can be individually controlled by introducing the proposed algorithm for controlling both the vehicle linear velocity and the tire slippages.

The developed method is based on continuously monitoring the normal load and tire inflation pressure and using them as the inputs to estimate the theoretical linear velocity of the wheel (zero slippage). The control algorithm, based on an inverse dynamics approach, adjusts the applied wheel torques via closed loop feedback control of both the measured angular velocity and slippage of the wheels. A vehicle model, based on empirical data of terrain and tires, is created in LabVIEW software to simulate the tires of a terrain truck to evaluate the control algorithm.