Bilateral Control of SeNZA - A Series Hybrid Electric Bicycle

The need for reducing pollution, congestion, and energy consumption is increasing the interest in light electric vehicles. E-bikes can play an important role in this scenario, since they are cost effective, easy to use, and have a small footprint. This paper explores the series hybrid electric bicycle concept. This vehicle is characterized by the absence of a mechanical transmission: the pedals are connected to a generator electrically coupled to a battery pack and an electric motor. This increases the degrees of freedom with which assistance can be provided, but poses several challenges: from human interfacing to energy management. The proposed vehicle is not equipped with a throttle: pedals are, at the same time, a power source and the human-machine interface. It is paramount that the vehicle is controlled so to yield a natural feeling, both at the pedaling dynamics level and at the vehicle level. In this paper, this is obtained through the bilateral control framework. This paper discusses the design of the control system along with several considerations on the choice of generator, motor, and tuning. The controller is finally extensively experimentally analyzed in a human-in-the-loop setting, considering both the cycling feeling and the energy flows.