As the leading high-precision positioning manufacturer in China, the scale of R&D personnel such as technology research and development, operation and maintenance, and data solving accounts for about 80%, and the proportion of R&D personnel with bachelor's degree or above is about 90%, of which master's and doctoral degrees account for more than 30%.
On June 14, 2023, at the 5th 2023 Autonomous Driving Map and Positioning Conference, Hu Gongsheng, an expert in Beijing Liufen Technology Solutions, said that the development and application of technology is inseparable from the scene, and in the context of L2-L4 and V2X, different requirements for high-precision positioning of vehicles are put forward. At present, the industry's mainstream high-precision GNSS positioning architecture for intelligent driving includes GNSS chips, IMUs, wheel speed meters, positioning engines, deflection plug-ins, etc. The Six-point PPP-RTK provides fast convergence, centimeter-level precision positioning services by introducing precision orbit, clock difference, code/phase deviation and atmospheric delay products.
Hu Gongsheng | Beijing Liufen Technology Solution Expert
The following is a summary of the speeches:
As a high-precision positioning manufacturer of domestic heads, Beijing Liufen Technology has maintained a rapid development state since its establishment in 2017. With high-precision positioning technology as the core, Liufen Technology is committed to becoming a manufacturer of high-precision positioning solutions trusted by users.
High-precision positioning application scenarios for intelligent driving
Technology development and application are inseparable from the scene. In the two scenarios of autonomous driving L2 and V2X, vehicles put forward different requirements for high-precision positioning.
Taking intelligent driving scenarios as an example, vehicles need to achieve lane-level positioning to ensure that the positioning accuracy of all scenarios is maintained. Taking application scenarios such as V2X and vehicle-road coordination as an example, many car owners need high-precision positioning functions in addition to communication functions on V2X to ensure accurate position judgment, so as to meet the requirements of safety warnings and lane-level information reminders.
Based on this, the current intelligent driving positioning architecture may be shown in the figure below, with the absolute positioning technology of GNSS+IMU+RTK, as well as relative positioning means such as lidar and vision.
Source: Six Cent Technology
In fact, absolute positioning and visual positioning belong to the category of sensors, and everyone should work together to ensure that the vehicle meets the high-precision positioning needs of different scenarios in accordance with the requirements of the OEM.
High-precision GNSS positioning architecture for intelligent driving
Liufen Technology focuses on RTK services, with RTK technology as the core, to provide users with high-precision positioning solutions. We will focus on the high-precision GNSS positioning architecture of mainstream OEMs in intelligent driving and make three classifications:
The first category is the hardware level, which requires a positioning chip or GNSS module, plus the IMU chip or module, including the access of the vehicle wheel speedometer, all belong to the hardware category.
The second category is the need for the vehicle to obtain RTK data services from the six-point platform through the 4G/5G communication network.
The third category is a crucial field, namely positioning algorithm engines. In addition to positioning engines, for safety reasons, the vehicle also needs to integrate deflection plug-ins before mass production. When the positioning engine outputs the algorithm and obtains the result, a certain amount of deflection is added through the deflection plug-in to finally obtain the position information.
At present, the hardware architecture of the OEM is slightly different, but most of the hardware, software, algorithms and service elements required are shown in the figure below.
Source: Six Cent Technology
Based on this, Liufen Technology provides functional safety software based on RTK services, positioning engines and deflection plug-ins, which we call Monitor, to provide different types of combined solutions to serve OEMs, Tier1 and other customers.
About Six-Cent Brilliant PPP-RTK
First of all, let's introduce the six-point star products based on PPP-RTK technology.
PPP-RTK technology integrates PPP and RTK positioning technology to provide fast convergence, centimeter-level precision positioning services by introducing precision orbit, clock difference, code/phase deviation and atmospheric delay products. Compared with RTK services, Sixpoint Star has server-side integrity monitoring and ASIL-B certification for terminal algorithm functional safety.
The positioning performance of PPP-RTK is mainly divided into three levels:
The first is the positioning accuracy level, PPP-RTK six-point star, under a fixed point, the convergence horizontal accuracy can reach 10-30cm. The convergence time is 15s-50s. In practice, it depends on different scenarios and measured results.
The second is the service advertising mode, PPP-RTK supports 4G or 5G communication network advertising, and supports the transmission of satellites through Lband communication iPad to solve the problem that the vehicle can still receive differential positioning service functions in areas without network or weak network.
The third point is related to security, we already have server-side integrity monitoring, including public safety authentication at the terminal algorithm level.
Observing the evolution trend of RTK technology for intelligent driving, at present, mainstream OEMs and other scenarios will use NRTK more. We compare NRTK and PPP-RTK from both a technical and commercial perspective.
First of all, NRTK is a regional-level service, and its technical characteristics determine that it does not need to build too many base stations in a wide area area. From the service data, NRTK advertises the original observation based on the virtual reference site; PPP-RTK technology advertises the five types of differential data mentioned above. Therefore, for NRTK technology, the vehicle or other terminal is limited by the performance of its own or the actual physical base station around the vehicle during use, while the PPP-RTK base station density is relatively low and the range is wider. PPP-RTK can smoothly switch between PPP, PPP-AR, PPP-RTK services based on the service data content.
RTK service solution selection is the focus of customer and OEM concerns. Overall, the advantage of NRTK technology is that compared with PPP-RTK, NRTK has higher positioning accuracy and lower implementation threshold. As a service provider, Liufen Technology has built about 3,000 RTK base stations across the country to provide users with stable and reliable NRTK services. In addition, NRTK has a unified standard protocol, based on which its software architecture will be more flexible in the implementation process.
The disadvantage of NRTK is that it is difficult for domestic service providers to build websites abroad, so to a certain extent, its use is more limited to China. In addition, due to the large number of base stations, it is difficult to achieve server-side integrity monitoring from the software level from an engineering point of view. At present, OEMs will prefer PPP-RTK services when it comes to functional safety.
The advantages of PPP-RTK are obvious, on the one hand, it can achieve a globally integrated solution with global partners, and on the other hand, it can also meet the server-side integrity monitoring and terminal functional safety design.
The disadvantage of PPP-RTK is that it has lower positioning accuracy than NRTK in the same scenario. And there will be fewer suppliers of PPP-RTK technology that are relatively mature. Moreover, the algorithms and services of PPP-RTK have higher requirements for hardware computing resources.
Six Points' "Monitor + Security Plug-in" technical solution
In order to ensure the security of national geographic information, all commercial map products must be deflected and encrypted by the deflection encryption algorithm of the Institute of Survey. Since the map is deflected and encrypted accordingly, the vehicle terminal equipment needs to integrate the location security plug-in provided by the Institute of Surveying and Technology before mass production or on the road to ensure that the positioning results of the vehicle terminal match the map.
In addition, the integrated location security plug-in for vehicle terminals introduces some jitter. Therefore, OEMs and Tier1 have requirements for functional safety and need to estimate jitter. Based on this, Liufen Technology launched the technical solution of "Monitor + Security Plug-in".
Monitor software has four main functions: first, we will monitor the input of the location security plug-in to ensure the validity of its input; Second, monitor the output of the location security plug-in to ensure the validity of its output; Third, monitor the running status of the location security plug-in, including abnormal states such as blocking and memory overflow. Fourth, and the core, the Monitor software will synchronously output the protection level of position jitter errors generated by the location safety plug-in in real time.
Based on these four functions, when the vehicle integrates high-precision positioning capability, after the deflection plug-in, we will still effectively estimate the jitter introduced to ensure the functional safety of the positioning process. In addition, Monitor software follows the ASPICE (Level 2) development process from conceptual design to system design, to unit testing, and finally to system integration testing, which meets the requirements of ISO26262 (ASIL-B) functional safety level.
At present, our products have been mass-produced and delivered at other Global OEMs.
Summary and outlook
For intelligent driving, high-precision positioning is a system engineering, to achieve very good results, it needs to include three aspects:
The first aspect is critical GNSS hardware. At present, when we carry out high-precision positioning, there are many types of hardware architectures, for example, based on all domain control forms or based on domain control + P-box forms, which involves us and the main engine factory to design the overall hardware architecture. At the same time, about the choice of GNSS chip or module; About IMU performance and integration; GNSS antenna selection, when we choose the antenna, we also need to pay attention to the vehicle antenna layout and hardware terminal placement.
The second aspect is the positioning engine and algorithm level. For algorithms, each OEM has different considerations, and some hope that service providers or algorithm providers can implement combined navigation algorithms; Some only need the RTK algorithm about who is responsible for the algorithm, as well as deep coupling and loose coupling problems, customers need to combine their own hardware and computing power resources for comprehensive consideration. In addition, technical requirements such as the need to support functional safety and the defined format of the algorithm output need to be considered.
The third area, in the area of location services, we need to determine whether we need PPP-RTK services or NRTK services. Including the framework and epoch of the unified coordinate system, we need to determine whether to deploy a proprietary service platform or directly accept the public services provided by the service provider. In addition, after the release of the production car, it is necessary to clarify how the service account will be activated. The promotion of GNSS high-precision positioning in the field of intelligent driving also requires the joint efforts of industry partners of hardware, algorithms and service manufacturers to ensure the best high-precision positioning solutions.
(The above content is from the keynote speech "High-precision Positioning Solutions for Intelligent Driving" delivered by Hu Gongsheng, a Beijing Liufen Technology Solution Expert, at the 5th Autonomous Driving Map and Positioning Conference 2023 on June 14, 2023.) ）