Development of a method to compute the kingpin axis using screw axis theory based on suspension-parameter-measuring device data

摘要

Kingpin geometry is one of the most important design features in vehicle development, as it determines the steering feeling of drivers, the handling performance, and the steering stability of a vehicle. The idea of a geometric kingpin axis has been used to design a relatively simple suspension mechanism such as a double-wishbone type, and various techniques have been developed to design the kingpin axis of multi-link suspensions. However, a kingpin axis for a real vehicle has been unknown so far because there has been no method to measure or compute it. This paper presents the development of a method to compute the kingpin axis of a vehicle using screw theory and suspension-parameter-measuring device (SPMD) data. SPMD data, such as the wheel centre displacement, toe, camber, and side view angles, are used to derive the finite displacement matrix of the wheel. The finite screw axis is computed on the basis of the displacement matrix, and its compatibility with the kingpin axis is verified by an in-house kinematic analysis program and ADAMS/Car. The result of the finite screw axis method (FSAM) is also verified indirectly by comparing suspension parameters such as the caster trail with the SPMD test result. Both verification results show that the FSAM can successfully compute the kingpin axis of a real vehicle.