Optimization of semi-trailing arm suspension for improving handling and stability of passenger car

Semi-trailing arm is an extended form of two suspension systems trailing arm and swing axle that compromises advantages and disadvantages of those systems. In this article, using Bees algorithm optimization method, the characteristic parameters of a semi-trailing arm suspension system to optimize the handling and stability performances of a passenger car are determined. Two types of objective functions, namely off-line and on-line, are defined. In off-line objective function, variation of camber, toe angle, and wheel track due to roll are considered. In the on-line objective function, handling and stability performance of a moving vehicle in a standard J-turn maneuver are considered. A nine degree-of-freedom non-linear vehicle model consists of semi-trailing arm and MacPherson suspensions in rear and front axle, respectively, is considered. The optimized suspension systems obtained from both off-line and on-line objective functions are utilized in making two accurate vehicle models in ADAMS-Car for experimental field test. A comparison between the behaviors of the two vehicles shows that despite the simplicity of optimization with off-line objective functions relative to on-line1, it returns the satisfactory results and improves both the handling and stability performances.