Summary: This paper summarizes the basic situation of the technology application of the camera monitor system (hereinafter referred to as CMS) at home and abroad, the standards and regulations at home and abroad, the functional requirements and installation requirements of CMS. CMS helps improve the driver's indirect vision, improve aerodynamics and optimize the fuel economy of new vehicles. According to the latest version of UN Regulation No. 46 (UN-R46) [1] and the standard framework established by the new standard ISO 16505 [2], CMS can be used to replace the mandatory installation of traditional mirrors in vehicles produced in mass in Europe, Japan and other countries. According to the characteristics of traditional rear-view mirrors, the CMS designed must have similar functions, including time characteristics, system resolution, size of display objects and field of vision.
Beijing Rubik's Cube CMS, taken at the 2021 Guangzhou Auto Show
1. Technical background of camera monitor system
1.1 Technical status of camera monitor system
CMS is an indirect vision device used to replace the traditional rear-view mirror. With the emergence of intelligent networking, automatic driving, ADAS and other new technologies, cars are developing rapidly in the direction of electronics and intelligence, as well as car rear-view mirrors. In the future, rear-view mirrors will be allowed to be replaced. The combination of camera and monitor will be used to solve the problem of rear-view. The use of the camera monitor system (CMS) instead of the mandatory rear-view mirror can help reduce the air resistance of the vehicle, reduce the blind area of vision, and improve the visual performance in harsh environments. At the same time, the camera that replaces the rear-view mirror can integrate ADAS and intelligent networking related functions, and display visual information in real time on the appropriate display in the vehicle. CMS includes a camera to capture the field of vision, send signals to the electronic control unit (ECU) for further processing, and then use the monitor to provide the driver with the field of vision.
1.2 CMS in China
The content of GB 15084 Performance and Installation Requirements for Devices for Indirect Vision of Motor Vehicles [3] is based on the requirements and test methods specified in UN-R46. Therefore, the installation of rear-view mirrors in China is also a mandatory requirement, and CMS is not allowed to replace such rear-view mirrors (except Class V and Class VI rear-view mirrors). In 2018, the revision of GB15084 standard was officially launched in China. In the near future, it is possible to allow CMS to replace traditional rear-view mirrors in China. At present, some information indicates that the standard may be implemented in May 2022.
1.3 CMS in Europe
As the first region to implement UN-R46 regulations, Europe has allowed CMS to replace traditional rear-view mirrors in 2016. Major vehicle manufacturers have also begun to develop relevant models. At present, there are mass production models of passenger cars and commercial vehicles.
1.4 CMS in Japan
As a contracting party to the 1958 Agreement, Japan has synchronously adopted the UN-R46 regulation. On this basis, Japan has allowed the use of CMS instead of traditional vehicle mirrors.
1.5 CMS in the United States
FMVSS 111, the regulation of indirect vision devices in the United States, stipulates that vehicles must be equipped with physical rear-view mirrors, and CMS is not allowed to replace rear-view mirrors. In March 2014, the Alliance of Automobile Manufacturers and Tesla Motors requested NHTSA to update and upgrade FMVSS 111 to make CMS compliant. Since NHTSA hopes to know about the safety performance of the system before CMS is allowed, the Alliance of Automobile Manufacturers has carried out research on the safety impact. At present, the Alliance of American Automobile Manufacturers and NHTSA are still communicating on this aspect.
2. Foreign standards related to CMS
According to the requirements of UN-R46 regulations, the vehicle must be equipped with a system that provides indirect vision. Typically, indirect vision is provided by conventional mirrors mounted on the vehicle. According to the new international standard ISO 16505 Road Vehicles - Ergonomics and Performance Aspects of Camera Monitoring Systems - Requirements and Test Procedures, the corresponding technical requirements for replacing such mandatory rear-view mirrors with camera monitoring systems are outlined.
The latest amendments to UN Regulation No. 46 have been issued in accordance with ISO 16505. This amendment is the first regulation to allow the use of CMS instead of rear-view mirrors in passenger cars and commercial vehicles. The World Forum for Harmonization of Vehicle Regulations (WP. 29) adopted the amendment proposal for UN-R46 in November 2015, and it came into force in August 2016.
2.1 UN-R46
The United Nations Economic Commission for Europe World Forum for Harmonization of Vehicle Regulations (UN-ECE WP. 29) is one of the working groups of UN-ECE. The working group started to revise Regulation R46 in 2009 to make the camera monitoring system replace all rear-view mirrors. In order to determine the technical parameters and test methods, an informal working group on camera monitoring system (IGCMS) was established. For commercial vehicles, CMS has been allowed to replace Class V rear-view mirror (close proximity mirror) and Class VI rear-view mirror (front rear-view mirror) since 2005. These two types of rear-view mirrors are only used when the vehicle is in a low-speed condition (such as reversing, etc.), and it is not appropriate to implement the same requirements for all other types of rear-view mirrors. One of the results of IGCMS's work is that a proposal for such a system was made within the expert group of the International Organization for Standardization (ISO). The international expert group carried out in-depth research from 2010 to 2014, and finally drafted ISO 16505, and reorganized IGCMS (ICGCMS II) in 2014. According to the content of ISO 16505 standard, IGCMS II prepared an amendment to UN R46, and added other content, rather than just citing the entire content of ISO 16505 standard. The proposal came into force in August 2016, allowing the replacement of the following categories of rear-view mirrors: Class I rear-view mirrors (interior rear-view mirrors) and Class III rear-view mirrors (main exterior rear-view mirrors) for passenger vehicles; Class II rear-view mirror (main exterior rear-view mirror), Class IV rear-view mirror (wide-angle exterior rear-view mirror), Class V rear-view mirror (close proximity exterior rear-view mirror) and Class VI rear-view mirror (front exterior rear-view mirror) for commercial vehicles.
2.2 ISO 16505
ISO 16505 specifies the minimum technical requirements that CMS must meet as an alternative to mandatory rear-view mirrors, including relevant safety, ergonomic design, performance requirements and test methods. This new standard is the basis for future standard CMS design and CMS testing by testing organizations. The ISO 16505:2015 standard document was first released in May 2015, and a revised version of ISO 16505:2019 was issued in 2019. Some editorial changes were mainly made, but the main technical content remained unchanged. Chapter 2 of ISO 16505:2019 is a normative reference document. Chapter 3 describes the terms and definitions used in this standard. Some of the terms and definitions are related to vehicles and rear-view mirrors, and some of the terms and definitions are related to various components (including cameras and monitors) and the entire CMS. Chapter 6 of the standard focuses on introducing and discussing detailed system technical requirements, involving component level and vehicle installation requirements. Chapter 7 clearly stipulates the test methods and conformity determination requirements for various technical requirements. ISO 16505:2019 finally discusses functional safety. CMS is a safety related system.
3 Technical requirements of CMS
3.1 Functional requirements
The functional requirements mainly focus on image quality. Although the functional requirements for Class V and Class VI CMS mainly include brightness contrast and highlight overflow, several new requirements have been formulated for Class I to Class IV CMS due to different use cases of CMS. The functional requirements are as follows: brightness adjustment, monitor isotropy, brightness and contrast reproduction, gray level reproduction, color restoration, artifacts, sharpness and field depth, geometric deformation, flicker, time characteristics, magnification and resolution. In this respect, it is required to focus on assessing the image performance ability of CMS under different ambient lighting conditions.
Brightness adjustment is the basic brightness adjustment function verification of CMS monitor; The monitor is isotropic, and the man-machine function energy efficiency of CMS monitor is assessed based on brightness: brightness and contrast reproduction, and brightness resolution is implemented for the monitor image recognition under four states of daytime, dusk, night, and direct sunlight; Gray level reproduction is the ability to judge the true reflection of CMS to gray blocks with different optical density values, and also represents the ability of dynamic range to a certain extent; Color restoration, that is, the ability of CMS to truly reproduce the color of the subject; The artifact point light source reproduces the CMS's ability to recognize the vehicle's low beam light 250 m away from the rear at night. The artifact leakage, artifact halo and lens flare distinguish the CMS's ability to process artifacts and retain enough normal field of view when there is a bright point light source in the field of view: sharpness, which requires calculating the MTF50 value of the CMS imaging center area and 70% field of view area, The sharpness of CMS image is characterized; Field of view depth (resolution) requires CMS to have sufficient clarity at distances of 4m, 6m and 10m: geometric deformation represents the distortion degree of terminal image of CMS as a camera system for automobiles; Flicker, which requires that the blinking of the CMS monitor has enough "affinity" for the human eye; The time characteristic ensures the timely response of CMS during startup and normal operation: magnification, which enables CMS to confirm that it has the same real scene zoom ability as traditional indirect vision devices [4].
3.2 Vehicle installation requirements
In addition to the requirements for CMS component level, it is also required to meet the requirements for vehicle installation, so as to meet the vehicle ergonomic design and provide users with a stable and reliable vision.
System startup and shutdown: specifies when the system must run and when it can be disabled. Most vehicle occupants will leave the vehicle soon after the engine ignition key is turned off. In consideration of power management and safety, a delay of more than 120 seconds before closing the image (T1=) will allow most vehicle occupants to leave the vehicle. And by adding (T2=) 300 seconds, until the passenger decides whether to continue or resume CMS operation, the image recovery time is less than (RT=) 1 second, the CMS can be used when the passenger delays leaving the vehicle after turning off the ignition key. Delays that are not reconfirmed by the need for continued use will be closed, and the recovery time is not longer than 7 seconds. The recovery time is also defined as the maximum time limit for CMS cold start.
Overlay: The maximum size limit of each overlay (such as icons, labels, colored lines, etc.) is 2.5% of the required minimum field of view display area. In addition, the maximum total area of all obstacles within the required field of vision is limited to 15% for Class I devices and 10% for all other categories of devices.
Amplified aspect ratio: the purpose of this clause is to avoid the CMS design of horizontal and vertical aspect ratio field of vision that is greatly different from the actual scenery, which may lead to misjudgment of the external field of vision.
Integration in the vehicle of the monitor: In ISO 16505, the display position of the visual field is related to the monitoring device (the left visual field is displayed on the left side of the monitoring device, and the right visual field is displayed on the right side of the monitoring device), while the R46 rule stipulates that the monitor is arranged according to the position relative to the driver's reference eye point (the left visual field is displayed on the left side of the reference eye point, and the right visual field is displayed on the right side of the reference eye point). According to R46 regulations, monitors similar to the current exterior rear-view mirrors can be installed, while monitors installed in the central control position instead of traditional mirrors are not allowed.
Functional safety: Since the camera monitoring system is a safety related electronic system, ISO 16505 requires that its functional safety requirements be considered in the development process, so ISO 16505 refers to other existing functional safety standards. The R46 regulation does not refer to other standards. It has its own framework, which supports the adoption of methods that can avoid or control software and hardware systems and random failures. Therefore, the regulation provides several standards that have been verified by technical institutions to develop appropriate safety schemes, including documentation and verification. The key requirement of the safety plan is to ensure that the driver is notified of any electrical/electronic failure in the CMS (for example, by sending an alarm signal).
4 Other relevant UN regulations on CMS
In addition to R46 regulations, there are other UN regulations that will also affect the integrated installation of CMS in vehicles. This section outlines other requirements that must be considered in the development process to ensure that the product complies with relevant regulations.
4.1 UN-R10 (electromagnetic compatibility)
UN-ECE R10 describes the requirements for electromagnetic compatibility (EMC) (i.e. emission and immunity of electromagnetic radiation). As the camera monitoring system is a safety related electronic system, it must have anti magnetic field or electric field characteristics. Therefore, the R46 regulation requires that the camera monitoring system meet the technical requirements of R10.
4.2 UN-R21 (interior decoration)
The requirements in R46 relate to the influence of passengers on the devices for indirect vision inside the vehicle (such as Class I interior rear-view mirrors, etc.) and the influence of other road users (such as pedestrians, etc.) on the devices for indirect vision outside the vehicle (such as Class III exterior rear-view mirrors, etc.). The impact requirements are verified by dynamic pendulum impact testing. The R46 regulation clearly stipulates that as long as the vehicle is approved according to the requirements of R21 regulation, the CMS monitor does not need to do the pendulum impact test.
Regulation R21 specifies the requirements to avoid injuries to occupants due to body impact on the interior. This regulation is limited to M1 vehicles (passenger cars). Although the interior rear-view mirror is not subject to R21 regulation, this regulation needs to be considered because the CMS monitor is within the scope of this regulation. Several requirements in the R21 regulation (such as the radius of curvature of the convex part, material hardness and energy dissipation of the material) are related to different head impact zones. Therefore, it is not possible to answer in general whether the requirements and tests are applicable to CMS monitors and which requirements and tests are applicable to CMS monitors. Depending on the position of the monitor in the vehicle. Therefore, the integrated installation of the monitor needs to be carefully evaluated to ensure compliance with the head impact requirements of R21 regulation.
4.3 UN-R48 (Installation of Lighting and Light Signaling Devices)
R48 specifies the requirements for the installation of lighting and light signalling devices for vehicles of categories M and N, including trailers (category O). The purpose of this regulation is to ensure minimum road lighting first, and then to ensure that other road users can fully identify the vehicle. The regulations require passenger cars (M1) to be equipped with two side direction indicator lamps. When installed on the vehicle, these lamps must meet specific requirements regarding geometric visibility (angle) and photometry (illuminance). In some passenger cars, the side direction indicator lamp is integrally installed in the exterior rear-view mirror (Class III) housing. If CMS is used to replace the rear-view mirror, the turn indicator lamp needs to be rearranged. Therefore, the rearrangement of turn indicator lamps needs to be carefully evaluated to ensure compliance with the relevant requirements of R48 regulation.
4.4 UN-R95 (side impact protection)
According to the requirements of R95 regulation on CMS, after the impact test, any internal device or component shall not have sharp projections or serrated edges that significantly increase the risk of injury to passengers, which is related to the integrated installation of monitors in the vehicle.
4.5 UN-R125 (front view)
The obstruction to the driver's direct vision caused by the installation of the device for indirect vision shall be minimized. The impact on the integrated installation of monitors. Due to the lower seat position and the relatively higher upper edge of the front door, the limited available space between the instrument panel and these planes is obviously not suitable for the integrated installation of CMS monitors. The latest R125 amendment proposes that the monitors can be exempted in the following cases: vehicles equipped with certified traditional rear-view mirrors as standard configuration, CMS can be selected to replace the certified rear-view mirror. The CMS shall not be more blocked than the rear-view mirror, and the position of the monitor shall be as close as possible to the position of the replaced rear-view mirror.
5 Conclusion
With the development of electronic and intelligent automobile and the improvement of relevant standard systems, more and more automobile enterprises begin to equip CMS to replace traditional mirrors. With the promotion of national standard revision and the improvement of relevant testing and certification capabilities, there will be mass production models equipped with CMS in China in the near future.
How to improve the mass production details such as anti glare, anti fog and defrosting, distortion correction, transmission rate, etc. of electronic rear-view mirrors when the regulations are released soon? Welcome to join the Aibang Automotive Electronic Rearview Mirror CMS Exchange Group to discuss with people in the industry such as Huayang, BOE Jingdian, Guangzhou Rongsheng, Yuxing Electronics, Qingdao Jidong, Hansitong, Xinyang Rongle, Yuanfeng Technology, Sunny, Oufei Light, Qiu Tiwei, Helitai, United Optoelectronics, Tianshi Jinggong, Xinli, Jinkang Optoelectronics, Haowei, etc.
