Using a steer-into-the-fall based control law to stabilize a pedelec

Despite having complex dynamics, a bicycle can be stabilized easily by steering into the direction the bicycle leans, also known as steer-into-the-fall. Although this can be a difficult task for the cyclist, this basic control law can easily be implemented by a technical system to help the cyclist to stabilize the bicycle. As several studies on bicycle dynamics show, at least theoretically in simulations, a proportional controller based on the steer-into-the-fall principle is sufficient to stabilize a bicycle (Åström et al., 2005; Schwab et al., 2008). A steering assistance system consisting of a proportional controller and an electric motor applying torque to the handlebars can provide steering assistance and thus help stabilizing the bicycle. However, the design of a proportional controller working in parallel with the rider can be tricky. To prevent the cyclist from being irritated, the natural steering behavior of the bicycle must be affected as little as possible by the steering interventions. In addition, the cyclist always must be in control of the handlebars. In this study, we propose a control strategy based on a proportional controller that is designed using classical control engineering methods. Used in a pedelec with a prototype steering assistance system, this study investigates the effect of the controller on the stability of the pedelec and the impact of the steering interventions on the cyclist's riding experience.