Experimental Identification of the Lateral Dynamics of a Steering-assisted Two-wheeled Vehicle

This paper presents an Active Steering-Assistant system (ActiSA) that aims at enhancing the stability and safety of bicycles and motorcycles. The main objective of the ActiSA system is to control the lateral dynamics, which in the case of two wheelers are especially challenging and can become unstable. While the ActiSA system is designed to support the rider in such situations only, it remains inactive most of the time to minimise energy usage. This paper addresses the question whether or not the mere presence of the inactive ActiSA system may negatively affects handling. The problem is investigated through the identification of the steering torque to vehicle lateral dynamics transfer functions, both when the steering-assistant system is mechanically connected to the steering system yet remains inactive and when the steering-assistant is mechanically disconnected from the steering system. Transfer functions are identified experimentally using different types of tests such as lane-change, slalom, and multi-frequency steering excitations in the band range 0.1-4.0 Hz. The results obtained are consistent over the different approaches employed, and show an impact of the ActiSA system mainly at frequencies below 2 Hz, which is particularly evident at low speeds.