Abstract
Here, we analyze the energy loss that occurs owing to slippage between tires and the road surface in four-wheel-steering electric vehicles. We investigate the determination of tire force distribution for minimizing the energy loss as an optimization problem under the following constraints. We formulate the problem with the constraints that the total values of the traction/braking forces, of the lateral forces due to the steering of the front and rear wheels, and of the yaw moments generated by differences in the steering and the traction/braking forces between the left and right wheels are equal to the corresponding reference values. The analysis algebraically determines the tire force for the four wheels and the steering angles of the front and rear wheels. We also determine the optimum direct yaw moment analytically on the basis of the solution. We demonstrate, through numerical examples, the effect of energy loss reduction by comparing the optimization method with an alternative tire force distribution without the direct yaw moment control.
