Computer Aided Methodology for the Optimization of an Electric Motorcycle Suspension

Abstract

Abstract There are almost 9 million motorcycles registered only in the United States, while in other much smaller countries such as Colombia, this number can exceed 8 million. However, the population of Colombia is about six times smaller than the population in the United States. This demonstrates that for many people around the world, motorcycles are a great transportation method, which at the same time can provide a solution to the problems of urban traffic and scarcity of parking space. In addition to the problems associated with traffic, there are also public health problems related to the air pollution generated by internal combustion engines in motor vehicles. The issue of greenhouse gases emission from motor vehicles is being tackled by electric propulsion systems. The massive use of electric vehicles can have a strong positive impact in the quality of life of people and the environment. Therefore, electric motorcycles can become an optimal solution for transportation, by reducing the problems of urban traffic and space, while also being friendly with the environment. Two ways to help popularizing these vehicles are by reducing their cost and improving their performance. This work focuses on the optimization of the suspension system which is one of the key components of a motorcycle. The main function of the suspension system is to provide safety and comfort to the riders, two conditions that must be guaranteed in a good design. This article proposes a methodology for the optimal design of a motorcycle suspension, considering the different phases of development, starting with the geometric design, where the different parameters are determined for the front suspension, such as Rake Angle and Trail, and for the rear suspension, such as the inclination and the geometry of the swing arm system. Next, the detailed design is carried out, making sure that the elements of the suspension coincide with the dimensions at the attachment points to the chassis. Once all the geometry is available, the kinematic analysis is carried out, to assess the behavior of the system during the wheel trip. A structural analysis is performed to evaluate stresses, stiffness and resonance frequencies of the system, and to evaluate the minimum safety factor of the structure under the action of typical loads. With the final geometry of the system, a lumped parameter model can be obtained to rapidly observe its transient behavior under the effect of different irregularities that may be encountered on the road, which lead to the optimization of the parameters that offer greatest comfort to the rider. This set of parameters was used as inputs for the representation of the system in the physical modeling simulation interface Simmechanics® to generate final performance graphs. The results obtained with this methodology covered the different aspects that must be considered in the design of an important part of a transportation system such as an electric motorcycle.