Wuhan University of Technology Graduation Design (Thesis)

Micro-unmanned electric bus brake system design

School: School of International Education

Specialty amp; Class: Automotive Engineering gj1502

Name: Deng Hao

Tutor: Pei Xiaofei

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Abstract

This paper intends to explore and study how to reasonably layout design the sensor of the self-driving car, to ensure the safety of the self-driving car. At the same time, the design of the dual-bus and vehicle circuit distribution of the self-driving car is needed, and the circuit structure and data transmission difference between the self-driving car and the conventional car are clarified. Of course, it should also consider the reliability redundancy design of the car, such as the design of the dual controller, dual actuator and dual power system.

By consulting relevant literature, we can understand the working principle and structural composition of self-driving car, and study the feasibility of the project objectives. Learning and studying the principles and characteristics of related sensors (including cameras, radars) of the Context-Aware system, we design and optimize the optimal redundancy, and ensure that the self-driving car sensor arrangement can bring enough security. Understanding the working principle of CAN bus, we know the data communication mode between components, and divide the CAN network nodes in a targeted manner to optimize the node layout while ensuring normal data communication. To consult the relevant literature to understand the driving safety redundancy design of self-driving cars, and we develop a dual-controller, dual-actuator, dual-supply and dual-bus system design for self-driving cars to ensure that a car can still operate normally with faults in some components and systems. On the basis of the above, we organize all the data, and use the drawing software to design the layout and draw the relevant drawings.

Through design analysis, this paper has a relatively systematic normative design on the overall layout of self-driving car, and has a solution to the redundant design of autonomous vehicles, which has certain practical significance.

Key Words： Redundant design; Vehicle circuit; Bus design; Context-Aware system.

Contents

Abstract I

Chapter 1 Introduction 1

1.1 Research background 1

1.2 Research status at home and abroad 1

1.3 Research work and thesis structure of this paper 3

Chapter 2 Context-Aware system of the Self-driving car 4

2.1 Related background of self-driving cars 4

2.1.1 Classification of self-driving cars 4

2.1.2 Related Sensors of the Context-Aware system 5

2.2 The Context-Aware technology solution of Self-driving car 6

2.3 Design of Context-Aware system 7

2.3.1 Vehicle Motion Module 7

2.3.2 Context-Aware Module 8

Chapter 3 Communication bus design of the Self-driving car 14

3.1 Automotive Communication Bus 14

3.2 Self-driving car bus design 14

3.2.1 CAN bus design 15

3.2.2 FlexRay bus design 19

3.3 Dual bus design of the Self-driving car 19

Chapter 4 Power supply circuit design of the Self-driving car 22

4.1 Dual power supply design 22

4.2 Vehicle power distribution map design 23

Chapter 5 Redundant design of self-driving car actuator 25

5.1 The meaning of the redundant design of the actuator 25

5.2 Redundant Steering System Design 25

5.2.1 Steer by wire system 25

5.2.2 Redundant design of the SBW 26

5.3 Redundant design of the braking system 27

5.3.1 Electronic Hydraulic Brake System 27

5.3.2 Redundant design of the EHB 28

Conclusion and Outlook 30

References 31

Acknowledgement 33

Chapter 1 Introduction

Research background

In recent years, the automobile industry has begun to show a huge wave of innovation, rapidly moving towards electrification, networking and intelligence. The development of self-driving cars will have a profound impact on the automotive industry and the transportation industry. To achieve automatic driving, the Context-Aware system is one of the key technologies. The Context-Aware system needs to quickly obtain relevant data information of the driving environment, such as the target within a certain range of the vehicle, the guidance of the lane line, and the traffic road information. The control system of the self-driving car needs to make corresponding path planning and decision according to the information fed back by the Context-Aware system, combined with the high-precision navigation system, to realize safe automatic driving. At present, auto-driving technology is rapidly developing, and the use of Context-Aware system is becoming more and more common.

At the same time, the reliability redundancy design of self-driving cars is also developing rapidly. The reliability redundancy design of the automatic driving system generally includes bus, power supply, positioning, sensing, controller and actuator. The reliability redundancy design is mainly to avoid serious safety accidents caused by the failure of automatic driving system due to a certain component or system. It ensures the safety of pedestrians and passengers.

Of course, communication between components is also important. In the automotive bus, due to the high-performance, high-reliability communication mechanism of the CAN bus, the CAN protocol is widely used for communication between various components in the car, and the CAN bus can replace the expensive and bulky distribution harness. Therefore, the current main bus in the car is composed of the CAN bus, as well as in the self-driving car. However, due to the high bandwidth requirements of various sensors in the autonomous vehicle environment sensing system, especially the lidar and high-resolution cameras, it is also necessary to transmit data using the Flexray bus.

Research status at home and abroad

Most of the foreign auto-driving car technologies detect the dynamic obstacles by analyzing the laser sensor data. On behalf of Stanford University's smart car "Junior", the laser sensor is used to model the motion geometry of the tracking target, and then the Bayesian filter is used to update the state of each target separately; Carnegie Mellon University's "BOSS" smart car The obstacle features are extracted from the laser sensor data, and the dynamic obstacles are detected and tracked by correlating the laser sensor data at different times. The self-driving car "WildCat" developed by Oxford University uses laser radar and cameras to monitor road conditions without using GPS.

The Ohio State University and the Oshkosh Truck Company have developed the Terra Max intelligent driving vehicle. The car is equipped with an advanced sensor system and Global Positioning System (GPS). In order to obtain information on objects within a certain distance of the vehicle, 24 environmental sensing sensors such as a camera, a laser radar, a millimeter wave radar, and an ultrasonic radar are installed.

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