1. Purpose and Significance (including domestic and foreign research status analysis)

   1.1 Research Background:

   With environmental protection and energy issues becoming more and more prominent, the problem of increasing air pollution and shortage of oil caused by traditional automobiles has received attention from people.In order to solve the problems of energy saving and environmental protection, the country strongly supports the development of electric vehicles and is considered as an ideal alternative to traditional vehicles.Electric vehicles have the advantages of sustainable zero-emission and low-noise energy sources. At the same time, electric vehicles can realize regenerative braking energy recovery through their own drive motors.^[1]Compared with traditional vehicles, electric vehicles have an absolute advantage in being able to recover part of the braking energy during braking.Braking energy recovery is also referred to as regenerative braking, which refers to controlling a motor to operate in a state of power generation during braking of a vehicle, converting the mechanical energy of the vehicle into electrical energy, and storing it in an energy storage system such as a battery，to achieve part of the braking energy recovery；^[2]At the same time as the motor generates power, braking torque will be generated and transmitted to the wheels through the drive train, thus decelerating the vehicle. However, the inertial energy in the braking process of conventional vehicles is converted into heat by friction.Motor regenerative braking technology can effectively extend the vehicle's driving range and improve energy utilization efficiency；Because the motor takes a part of the required braking torque, the friction braking torque borne by the brake can be reduced accordingly, so the motor regenerative braking technology can also reduce the thermal load of the friction brake, reduce the wear of the brake disc, improve the vehicle's system. Safe and economical use.Under urban conditions, vehicles need more frequent stops, decelerations, idle speeds, etc. Motor regenerative braking technology therefore has more considerable economic and social benefits.^[3]-[4]The eddy current retarder is the main component. Traditional automotive friction brakes have significant thermal decay when they are braked, and can generate braking dust and noise, affecting the safety of the brakes and polluting the environment.^[5]Electromagnetic brake is a non-contact eddy current brake, which has the characteristics of fast response time, stable braking, convenient control, no brake dust and noise, etc. Therefore, electromagnetic brake will be more and more widely applied to automobiles.^[6]

   1.2 Research Status at Home and Abroad

   The working principle and classification of the eddy current brake technology are introduced. Based on this, the structural principle and performance characteristics of the eddy current retarder and the permanent magnet retarder are described.^[7]-[8] Finally, the development of the eddy current brake technology is emphasized. The analysis of the trend indicates that the lightweight, integrated and energy-saving of eddy current brakes will be the future technological developmentment directiong.^[9]-[12]Safety,environmental protection, energy saving, high speed, and comfort are the directions for the development of modern automobiles. The auxiliary brakes will be an essential configuration for automobiles. As a kind of auxiliary brake, the eddy current retarder works on the principle that the kinetic energy of the vehicle when braking is converted into heat energy and is dissipated on the rotor.This will inevitably lead to the waste of energy, especially the heavy trucks that often run down long slopes on mountain roads and buses that often travel on complicated urban roads. ^[13]Frequent work of eddy current retarders will waste a lot of energy.The research will bring a more feasible method to solve the energy waste problem of eddy current retarder.Based on the above considerations, we will focus on the following aspects.^[14]Firstly, on the basis of summarizing the characteristics of eddy current retarder and various braking energy recovery methods, a scheme of energy recovery eddy current retarder is proposed, and its working principle, typical working modes and control are analyzed.Secondly, the braking torque of the energy recovery type eddy current retarder is studied, and its calculation formula is given. Based on this, various energy recovery type eddy current retarders with the maximum braking torque of 1500 N.m are designed. Parameters, based on the reference to the existing eddy current retarder, designed a more reasonable structure.^[15]This paper presents an energy recuperative eddy current retarder (ERECR), which offers a solution to the energy consumption and overheating issues of the conventional eddy current retarders (ECR). The ERECR obtains three main systems, namely Eddy Current Braking (ECB) system, Regenerative Braking (RGB) system, and Electrical Control System. The RGB system, which could recover the kinetic energy from downhill and the braking condition, is mainly concerned in this research.^[16]High power rating and robustness of AC drive has made Induction motor based motion control a preferable choice in the industrial applications. This paper embarks on the issues of bidirectional power conversion, regenerative braking and energy storage. A simplified and cost effective method of three phase inverter fed induction motor drive capable of regenerative energy storage is discussed. This method is very useful for Hybrid Electric Vehicles, Traction Drive and hoist drive applications.^[17] A cost-effective regenerative braking system for Electric Vehicles (EV) driven by induction machine (IM) is proposed. The structure of the system is simple because the extra demands are only the capacitor bank and resistor bank. A five- phase IM is chosen in this paper to adapt the high- power trend of EV and lower the device size. The required reactive power for the braking system is supplied by means of a parallel connected capacitor bank and a voltage source PWM converter. The capacitor bank is used as a bulk uncontrolled source to transfer reactive power to minimize the converter current and filter voltage harmonic. An instantaneous power based control algorithm is also implemented to regulate the AC output voltage and DC link voltage.^[18]This paper first establishes the vehicle mechanics model, studies the structure and working principle of the brake energy recovery system of pure electric vehicles, and gives the control circuit of the brake energy recovery system using the permanent magnet brushless DC motor as the drive motor. The working principle of permanent magnet brushless DC motor and bidirectional DCDC/converter in the control circuit during regenerative braking is analyzed. In order to efficiently recover the braking energy, the flow conditions and conversion relationships of the braking energy are analyzed, and the main influencing factors that limit the braking energy recovery capability are studied.^[19]The vehicle-assisted braking device is a relatively independent braking system connected in parallel with the main braking device (service braking). Under the premise of ensuring the required braking power of the vehicle, the work of the main braking system can be greatly reduced. Time, thereby reducing the temperature rise of the main braking system, to avoid the risk of failure of the main braking system due to temperature rise of the main braking system. Therefore, it is very important to study the safety-relevant performance of automobile-assisted braking devices with high reliability, moderate cost, and energy conservation and environmental protection. This article analyzes the necessity of automobile-assisted braking devices from the perspective of policy and technology, and briefly describes the development status of auxiliary braking devices.^[20]

   1.3 Research Significance

   This paper mainly studies the structure of the eddy-current brake device, determines the torque matching relationship between the drive motor and the eddy-current boosting torque system, and improves the structure on the basis of the original to increase its torque and ensure the safe braking capability ang do not waste brake power.

   
   

2. 研究的基本内容与方案

2 The basic content, objectives, proposed technical solutions and measures for research (design)

2.1 Research objectives