On the response of rider body to motorcycle oscillations

In two-wheeled vehicles the mass of the rider is a significant fraction of the total mass of the system. Hence, the rider influences the dynamic behavior of the vehicle not only by means of voluntary control actions, but also by means of the passive mechanical properties of his/her body (mass, stiffness and damping properties). In particular the stabilization weave and wobble is affected by rider characteristics. For these reasons, advanced simulation of two wheeled vehicles requires detailed information about rider biomechanical properties. This paper deals with a research carried out at Motorcycle Dynamics Research Group that is aimed to identify the biomechanical properties of rider body from laboratory tests. Special test equipment has been developed, it is a mock motorcycle driven by a hydraulic servo-actuator that generates roll and yaw oscillations in the range 0.5 – 10 Hz. When the rider rides the mock motorcycle, a system of sensors measures the input motion and the response of the rider’s body. The motion of the rider’s body is represented in the frequency domain by means of frequency response functions (FRFs). To identify the biomechanical parameters of the rider, a lumped element biomechanical model has been developed, it makes possible the calculation of the theoretical FRFs corresponding to measured FRFs. Biomechanical parameters are found with best fitting techniques.