Research on the design of electric vehicle power domain controller

【Abstract】 This paper first analyzes the development background and evolution of electric vehicle domain controllers, and then designs the vehicle's electronic and electrical architecture and power domain controller based on a pure electric vehicle, sets the performance goals of its power domain controller, and designs a power domain controller solution with hardware time-sharing multiplexing and software modularization, and defines atomic service functions, service functions driven by big data, and information security functions. Finally, through bench performance tests, vehicle performance tests, and vehicle reliability test results, the key performance indicators of its power domain controller are verified, hoping to provide a reference for the design of electric vehicle domain controllers in the industry.

1 Introduction

In recent years, with the acceleration of electrification and intelligence of automobiles, the number of electronic control units (ECUs) in automobiles has increased sharply. It is understood that from 1993 to 2010, the number of ECUs used in Audi A8 models increased sharply from 5 to more than 100, and the number of ECUs installed in Audi A8L exceeded 100 in 2013 [1]. However, with the rapid popularization of electrification and the rapid upgrading of intelligence, increasing the number of ECUs is no longer a good idea. Since different ECUs come from different suppliers, whether it is the development of vehicle functions or the subsequent maintenance and upgrades, car companies need to communicate and cooperate with these suppliers separately. The process is cumbersome, the vehicle development cycle is extended, and the manpower and material costs increase accordingly [2]. In this context, the traditional distributed vehicle electronic and electrical architecture has shown a trend of centralized evolution. The previously isolated ECUs are integrated with each other, grouped and centrally controlled, and the domain controller (Domain Control Unit, DCU) came into being [3].

With the help of domain controllers, the vehicle can be transformed from more than 100 ECUs to a few DCUs, and control functions can be quickly centralized, which is conducive to reducing costs[4]. Domain controllers have scalable computing power and more flexible vehicle remote upgrades (Over-the-air Technology, OTA), allowing automobile companies to provide users with a continuously iterative and upgraded functional experience[4]. More importantly, domain controllers break the traditional bundled development model of perception + algorithm + ECU. The perception data processing of multiple sensors can achieve data fusion with the controller computing platform, and the vehicle can make safer decisions in a timely manner[5]. The aforementioned cost, safety or maintenance upgrade issues are solved. Therefore, research on domain controllers has become a hot topic for major host companies and electronic control component companies.

2. Vehicle electrical and electronic architecture design

2.1 Classification of domain controllers

At present, there is no unified classification standard for the domain controllers of electric vehicles in the industry, but from the current point of view, there are two main ways to classify domain controllers. One is to classify by region, which can be specifically divided into front regional controller, left regional controller, right regional controller, etc. Due to the high concentration and high technical difficulty, only a few companies such as Tesla currently adopt this classification method; in the corresponding vehicle electronic and electrical architecture of this classification method, a central computing module and three domain controllers are configured, namely the front body domain controller, the left body domain controller, and the right body domain controller, as shown in Figure 1.

Figure 1 Schematic diagram of domain controllers divided by region

Compared with the above classification method, the method of dividing by function is more acceptable to all host companies. At present, most car companies or parts companies adopt this method. From the current point of view, the main classifications are power domain controllers, chassis domain controllers, body domain controllers, cockpit domain controllers, autonomous driving domain controllers, etc., with slight differences between different companies. Among them, the power domain controller mainly integrates powertrain-related control functions and is mainly responsible for the optimization and control of the powertrain. With the integrated development of new energy vehicle electric drive and electronic control systems, power domain controllers are also increasingly used. The schematic diagram of domain controllers divided by function is shown in Figure 2.

Figure 2 Schematic diagram of domain controllers divided by function

This article studies the design of a pure electric vehicle power domain controller. The division method of this domain controller is similar to the above-mentioned division by function, and it is a power domain controller. However, the function is slightly different from the above-mentioned one. This power domain controller integrates the control of the power domain and some chassis components and body components, and plays a core control role in the electronic and electrical architecture of the whole vehicle. For the convenience of expression and understanding, it is referred to as the "power domain controller" below.

2.2 The electric vehicle electronic and electrical architecture studied in this paper

The electric vehicle electronic and electrical architecture studied in this paper has evolved from the traditional distributed architecture to the current "three-domain" architecture, as shown in Figure 3.

Figure 3 Schematic diagram of the “three-domain” vehicle electrical and electronic architecture

The intelligent driving domain controller implements lane keeping, adaptive cruise control, automatic parking and other functions based on key technologies such as environmental perception, precise positioning, control and execution. The cockpit domain controller uses heterogeneous operating systems to integrate entertainment systems, driver monitoring, vehicle networking, OTA and audio processing functions. The power domain controller is the intelligent brain of the vehicle, which implements dynamic control, power battery core algorithms, charging control, vehicle integrated thermal management, body control and decision-making logic and algorithms. The functional integration of the power domain controller is shown in Figure 4.

Figure 4 Schematic diagram of power domain controller function integration

3 Power Domain Controller Design

3.1 Performance Goals

At present, foreign technology companies represented by Bosch, Delphi, and Continental have long monopolized the controller products of power systems. It is urgent to develop power domain controllers with independent intellectual property rights and functional performance comparable to international first-class products to resolve the "bottleneck" of electric vehicle domain control technology. The main performance targets of the electric vehicle power domain controller studied in this paper are shown in Table 1.

Table 1 Main performance objectives of the power domain controller

3.2 Time-division multiplexing hardware

The time-sharing multiplexing technology is applied to design the hardware of the power domain controller, realizing the integration of the vehicle controller, air conditioning controller, central gateway, vacuum pump controller, and water pump controller. The number of microprocessor chips, power chips, and storage chips are reduced from 5 to 1, and the number of communication chips is reduced from 8 to 4. While the safety performance, control accuracy, sampling accuracy, and response level of the controller hardware are improved, the cost is reduced by 30%. The five controllers that are not integrated are shown in Figure 5, and the integrated power domain controller is shown in Figure 6.

Figure 5 Schematic diagram of the five hardware components that the power domain controller needs to integrate

Figure 6 Hardware diagram of power domain controller with time-division multiplexing

3.3 Modular application layer software

Using the Autosar software architecture, we developed a virtual bus software module, decoupled the software from the hardware, and decoupled the application layer software, making the software module reusable and easy to transplant. The application layer software has 7 functional modules and 17 sub-functions, including mode management, vehicle dynamics control, thermal management, and intelligent cockpit interaction. See Table 2 for details.

Table 2 Modular software of power domain controller

3.4 Core Function Definition

3.4.1 Atomic service function

On the basis of modularization and standardization of application layer software, the smallest indivisible control unit is further identified, standard software library functions and API interfaces are established, and atomic service functions that can be called by different software applications are developed. The application layer software of the power domain controller calls related atomic services according to the timing and functional characteristics of the functions, carries out logic-based combination and sorting, and realizes service-oriented agile development.

The power domain controller studied in this paper has developed 8 atomic service functions, including up and down power control, gear control, brake light control, turn signal control, electronic parking control, steering control, brake pressure control, and motor drive control. The 8 atomic services can be grouped or combined in any number to form a new vehicle control application software, as shown in Figure 7.