Combined steering–direct tilt control for the enhancement of narrow tilting vehicle stability

Narrow tilting vehicles offer an opportunity to reduce both traffic congestion and carbon emissions by having a small road footprint, a low weight and a small frontal area. Their narrow track requires that they tilt into corners to maintain stability; this may be achieved by means of an automated tilt control system. Automated tilt control systems can be classed as steering tilt control in which active control of the front-wheel steering angle is used to maintain stability, direct tilt control in which some form of actuator is used to exert a moment between the tilting part(s) of the vehicle and non-tilting part(s), or a combination of the two, namely steering–direct tilt control. Combined steering–direct tilt control systems have the potential to offer improved performance as, unlike steering tilt control systems, they are effective at low speeds while offering superior transient roll stability to direct tilt control systems. This paper details the implementation of a steering direct tilt control system on a prototype narrow tilting vehicle and presents experimental results which demonstrate a 36% reduction in load transfer from the inside wheel to the outside wheel during a ramp-steering manoeuvre when compared with a direct tilt control system.