Optimal matching between the suspension and the rubber bushing of the in-wheel motor system

Abstract

To overcome the increase in the unsprung mass and deformation of the magnet gap for in-wheel-motor-propelling systems, a novel topology scheme had been presented in previous work. In this study, an optimal matching design between the suspension and the rubber bushing is employed for the novel system to reduce the effect of the road surface roughness on the magnet gap as much as possible, on the basis of good ride quality and comfort. First, the half-vehicle model of the scheme is set up. Second, the objective function is developed using the weighting coefficient method to obtain a balanced consideration of the magnet gap deformation, the body’s pitch angle acceleration and the vertical vibration acceleration which takes the road condition, the vehicle speed and the load condition into account. The suspension’s dynamic travel, the dynamic load of the tyres, the damping parameters of the suspension, the bushing stiffness, the bushing damping and the bushing deformation are selected as the constraint conditions. Third, the design optimization for matching is carried out with the following excitation sources: the road surface roughness and the unbalanced magnetic force. Finally, a comparative analysis of the three optimization indices is performed before and after the optimization. The results show that, after optimal matching, all vibration response variables demonstrate measurable improvements. The magnet gap deformation achieves the greatest improvement, followed by the vertical vibration acceleration and the body’s pitch angle acceleration. The magnet gap deformation is improved by 42.4%, 45.4% and 44.99% under the no-load condition, the half-load condition and the full-load condition respectively, and the deformation of the rubber bushings satisfies the required design. The performance improvement is significant. The optimal matching method can be used to solve research problems involving the magnet gap deformation and the ride comfort of in-wheel-motor-driven vehicles, while at the same time offering a method for design optimization.