Optimization of vehicle dynamic behavior

Abstract

The current thesis focuses on the optimization of vehicle and seat suspension systems. A vehicle suspension system cannot eliminate the compromise between the parts of the most prominent conflict in automotive industry, i.e. the passenger's ride comfort and the vehicle's stability. However, they are able to combine the above-mentioned parts optimally. Considering the importance of a good suspension design, in this thesis, its optimization is studied extensively. Firstly, the most common mathematical models for simulation of vehicle dynamics are compared and investigated in order to conclude to the most appropriate for our research. Afterwards, an assessment of the optimization procedure in single and multiple objective optimization problems is conducted with respect to the efficiency of both the objective functions and the optimization algorithms. Then, an approach for handling the objective functions in multi-objective optimization problems is presented in order to minimize their number and save computational time. The research for a high-quality suspension system included also the study of semi-active suspensions and resulted in the development of a novel distribution-based control strategy (CDF) for skyhook control algorithms. Later, the conclusions regarding the optimization procedure are applied to various semi-active control algorithms, which also adopt the novel control strategy, in order to find their optimum design solution. However, the optimum design of a vehicle suspension system is not the only prerequisite for ride comfort. Seat suspension systems, are considered important and necessary so as to further isolate the passengers from the adverse effects of their exposure to vibration. In this respect, the modeling and the optimization of seat suspension systems is studied in this thesis. More specifically, a novel isolator with embedded negative stiffness elements (KDamper), which has proven efficient in other applications, is applied in a seat suspension and is benchmarked against the most common isolators in seat design, conducting an extensive dynamic analysis. Finally, conclusions are summed up and suggestions for further work are presented.