Design of the all-electrical anti-lock braking system and associated power conditioning for electric vehicles

Abstract

The anti-lock braking system (ABS) is crucial for automobile manufacturing and the market as a safety consideration. Thanks to the in-wheel technology (IWT), the development of ABS controllers has been dramatically enhanced. The application of an in-wheel motor dramatically improves the ABS's flexibility and accuracy in that each wheel is controlled independently. The proposed all-electrical ABS, which contains the anti-lock braking controller's algorithm design and associated power conditioning, is designed to precisely regulate the complete braking operation. A nonlinear anti-lock braking method with robust control performance is highly needed in the ABS algorithm design, especially when the vehicle braking on a tricky road. Generally, the ABS design starts with a single-wheel model and then evolves into a four-wheel model. The wheel slip control (WSC) with fuzzy sliding mode algorithm has been used to control all wheels under the anti-lock state on a predesigned sliding surface. A single-wheel dynamics model with initial parameters is established. Comparisons of braking effects under various anti-lock braking controllers are given, verifying that the proposed ABS can quickly stabilize the braking torque. Moreover, the road-detection module is added to the braking controller, making the proposed ABS more precise. The ABS design is then developed into the four-wheel braking control that addresses the braking issues with complex road conditions using the fuzzy sliding mode WSC method. Dynamic models under the complex braking situations are built with the consideration of certain exceptional cases, such as transition conditions on the braking road or split-conditions that occurs between the front-left, rear-left wheels and front-right, rear-right wheels, and even the worst braking situation wherein each wheel is on different roads, to demonstrate control performance, and some related simulation results are analyzed and examined. Finally, performance results are summarized to form a future ABS control and model. As the all-electrical ABS designed in this thesis contains the battery-supercapacitor energy storage system and the motor control module, associated electrical power conditioning is required throughout the ABS operation period. The power converters applied in EVs' energy storage system constructed by battery and supercapacitor are designed as the interleaved mode and operated in the voltage environment. However, this converter is designed to realize the energy flow arrangement through the current control method, which vulnerable to many problems, such as time delays due to the voltage-to-current-to-voltage cell transition and the addition of components. Usually, the voltage source inverters (VSI) used in the motor control module are expensive due to lower reliability and a large DC-link capacitor's demand. Therefore, the current source inverters (CSI) is considered as the alternate choice. Based on the preliminary analysis of these two modules, power converters based on the current-based environment are more suitable for developing all-electrical ABS. A series of the current source (CS) mode power converters are developed to help achieve the current-based environment. These converters directly offer current to the current-fed applications, which impose an alternative solution for the voltage source (VS) mode power converters in current-based systems. First, the CS mode switched-capacitor (SC) -based power converters are designed to increase conversion freedom. Combing the switched structure and the capacitor-tapping mode is validated as an excellent solution for limiting duty ratio adjustments. Then, CS mode switched-inductor (SI) -based power converters with a multiple-level conversion ratio selection mechanism are built. These converters transcend one conversion rule for one switching order under a fixed duty ratio and offer multiple choices for dealing with the complexation load. This type of converters' topology is designed with the resonance structure, which further eliminates the voltage spike on the switch and ensures soft switching for every switch. Moreover, a CS mode bidirectional DC/DC power converter between the battery-supercapacitor cell and EV is developed. The bidirectional DC/DC power converter is designed mainly by two methods: model predictive control and SC mode hybrid pulse-width modulation control. Moreover, the multiple-level conversion selection mechanism is applied to solve complicated load situations. This thesis aims to establish the all-electrical ABS rather than merely design a nonlinear anti-lock braking control algorithm. Another focus of this thesis is to explore and provide current-based power processing solutions to serve the current control further. Finally, the system, including the anti-lock braking controller and electrical power conditioning, is analyzed in detail, developed, and verified by simulation and experiments.