Control design of electrically-assisted steering systems for bicycles with child restraint seats

Recently, bicycles biking with children are attracting much attention in Japan, but a variety of dangerousness comes up biking with children. Then, a law for safety of bicycles with children has been established 2009. Consequently, bicycle manufacturers have provided bicycles adapting to new safety standards by improving structure, strength, stiffness, braking and steering performance. However, unfortunately, consideration from the dynamics aspect comes short in such bicycles. Our previous research has shown that the bicycle stability is best if a child restraint system is installed above the front wheel. On the other hand, increasing the moment of inertia when a child sits on the front seat might cause steering instability. Hence, in our research, to overcome the problem, an electrically-assisted steering system for those bicycles has been proposed. In this paper, a control method based on disturbance observer-based control for the assisted steering system is presented. The effectiveness of the proposed system with each control method is verified by frequency analysis, numerical simulations and experiments.