Optimization of a Double-Wishbone Torsion Bar Spring Suspension System for an In-Wheel Motor Driven Vehicle.

To address the performance degradation of double-wishbone torsion bar suspension systems caused by the significant increase in unsprung mass in in-wheel motor electric vehicles, this study conducted kinematic simulation analysis and optimization research on the suspension system. First, a parametric model of the double-wishbone torsion bar suspension was established based on ADAMS/Car, and a parallel wheel travel simulation was performed to obtain the variation characteristics of front wheel camber angle, toe angle, kingpin inclination angle, and kingpin caster angle with wheel travel. The results indicated that the initial design did not meet the requirement for the kingpin inclination angle to vary within the range of 7° to 13°, while other wheel alignment parameters also had room for optimization. By using the optimization module Adams/Insight, the variation patterns of suspension alignment parameters with wheel travel were analyzed, identifying key variables related to suspension performance such as the upper control arm joint points, lower control arm joint points, and tie rod outer joint points, which are critical to suspension performance. Through sensitivity analysis, the key hardpoint coordinates significantly influencing the optimization objectives were determined, and Design of Experiments (DOE) along with multi-objective optimization were conducted on the relevant suspension hardpoints. The post-optimization simulation results demonstrated that the variation ranges of the front wheel alignment parameters fell within reasonable intervals, improving suspension performance metrics and effectively enhancing wheel motion stability and vehicle handling performance. This research provides a systematic and efficient methodology for the design and optimization of similar suspension systems in electric vehicles equipped with in-wheel motors.