# Multi-Criteria Optimization of an Innovative Suspension System for Race Cars
## 1 Introduction  
While passing over irregularities on the rolling surface, the car wheel was subjected to vertical displacement. The suspension system (which includes the wheel guiding mechanism, and the elastic and damping elements) has the role of minimizing the impact that the rolling surface irregularities has on the chassis, reducing the forces, damping the vibration, isolating the interior (cabin/cockpit) from noise and shocks, and thus improving the ride and handling of the vehicle [1, 2, 3, 4, 5, 6, 7, 8]. Optimal suspension design, including the development of innovative solutions such as those shown in [9, 10], has been a permanent concern and challenge. In case of passenger car guiding (suspension and steering) systems, there are many theoretical and practical researches, including various analysis and optimization methods/techniques [11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21], which reflect the performances provided by the current designs, and in case of the single seater and lightweight formula cars, due to their special purpose and use, there are still researchable aspects insufficiently addressed so far. The present paper introduced a new suspension design that, compared with the existing ones, decoupled important metrics that would be preferred to be tuned separately. For instance, one of the MacPherson (suspension type mainly used in stock car racing) strut suspension main tuning disadvantages is its reduced ability to tune the camber gain. The main disadvantage of a double wishbone suspension system (suspension type mainly used in single seater) is the fact that some of the tunables influence each other and cannot be decoupled; for instance, the camber gain with wheel track variation. In the case of some of the best-handling street cars, such as the double wishbone suspension system whichcannot cope with the desired tuning, a multi-link suspension system is used, which offers a greater degree of freedom in tuning and decouples most of the metrics. In the case of the double wishbone suspension system, based on the Formula Student tuning trials, the main conflicts in this tuning are: The wheelbase variation being influenced by tuning the bump camber (same as roll camber); and the wheel track variation being influenced by the bump caster. One of the biggest constraints in the single-seater race car classes is the fact that there is not enough vertical space to insert a MacPherson strut suspension system (as it is one of the tallest suspension systems used in stock cars) or even a double wishbone strut suspension system (as there is not enough space to insert a regular spring and damper assembly). Thus, the main suspension system used in these racing events is the double wishbone with a push/pull rod and rocker. This paper dealt with a newly (innovative) design for the wheel suspension system of a single-seater car (Formula Student type), based on a comprehensive approach that included conceptual design, modeling, simulation and optimization, and development and testing of experimental model. For the proposed suspension system, the tuning process was not as straight forward as it would be for the other suspension systems. Some of the advantages of the proposed suspension system were that it has a similar spring, damper, and rocker assembly as the double wishbone (it does not require extra space), and it can cope with tuning the bump camber and bump caster without effecting the wheel track and wheelbase. It is well known that any suspension system is designed so that it creates the best dynamic behavior of the vehicle. This behavior may vary from vehicle to vehicle, as different cars have different scopes, although they use the same suspension mechanism. Any dynamic behavior can be divided into different design objectives (targets).