Design and implementation of a brake-by-wire system for e-scooters

Abstract

Electric scooters are gaining popularity as a means of transportation, especially due to their extensive usage by dockless rental companies. In the past, the Research Unit of Technical Dynamics and Vehicle System Dynamics of TU Wien has been studying the dynamics of e-scooters, particularly focusing on vehicle safety, and has identified significant potential for improvement, especially for braking manoeuvres. Following these studies, it was deemed reasonable to aim for a brake assistance system specially configured for e-scooters, in order to improve their braking performance and braking stability. This was the starting point of this thesis, which will be specifically about the practical hardware realization of such a system to enable further research, while the related control strategies are the focus of an accompanying thesis. Initially, the difficulties with braking identified by previous studies were concluded, followed by a careful identification of objectives and requirements for the actual assistance system. The goal is to create a system capable of assisting any rider, regardless of stature, strength, or driving experience, and dynamically adapting to external circumstances, such as road grip or the standing position of the rider on the footboard. The system should require only a single manual input from the rider, leaving them with the task of basically requesting a deceleration, while modulation and distribution of braking force to the front and rear wheel of the e-scooter is managed by the system itself to improve braking stability and safety. Subsequently, systematic research was conducted to identify different possible solutions to the identified tasks, in order to effectively select a well-considered final concept. The working principles of potential solutions were also thoroughly analyzed from a technical point of view to solidly justify decisions during the development process. The final system is a brake-by-wire system. It detects the operation of a single brake lever on the handlebar and after the control unit processes data from surrounding sensors, according to the chosen control strategy, activates electric actuators that engage two independent hydraulic disc brake systems. This thesis further deals with the practical realization of the chosen concept's prototype, including e-scooter, braking system of the front and rear wheel and secondary components such as wheel speed sensors. Equally important is the development and implementation of a system capable of determining the rider’s mass and position on the footboard, which are crucial parameters for selecting the required total braking force as well as the optimal brake distribution. Finally, the system ready for testing is presented as a whole, including an analysis of the achieved results and prospects for future steps in the project.