Static Suspension Force Analysis of Three-wheel Vehicle : Determining Chassis Boundary Conditions for Structural FEA

Sammanfattning

This study determines the static reaction forces at the suspension-to-chassis attachment points of a three-wheel electric vehicle developed in collaboration with an industrial partner. The purpose is to establish a complete set of force-based boundary conditions for future finite element analysis of the chassis structure. The analysis is carried out for a defined static vertical wheel-load case at nominal ride height. Motion Design is used as the primary multibody simulation method, while independent analytical calculations are used to verify the dominant load paths. The suspension-to-chassis reactions are determined as force vectors in the global vehicle coordinate system. For paired attachment points, lever-rule formulations are used to distribute the total reactions to the physical chassis attachments. The results show that the suspension geometry significantly amplifies, redirects, and redistributes the applied wheel load before it reaches the chassis. The rear spring link and the front pushrod are identified as dominant load-carrying members. The results also show that paired chassis attachments do not necessarily share the load equally, which means that simplified load-distribution assumptions may underestimate critical local attachment forces. The comparison between Motion Design and the analytical calculations shows good agreement for the dominant load-carrying members. The front upper-arm result shows lower agreement because the steering-link contribution is not included in the simplified analytical model. Therefore, the final upper-arm boundary conditions are taken from the complete Motion Design model, while this result is treated as less certain than the dominant load-carrying members. The determined boundary conditions are valid for the defined static ride-height case and can be used as input for static chassis finite element analysis.