Application of 9D lidar in the field of body-in-white online detection

Summary of this article

The latest dynamic 9D laser radar (9D LADAR) launched by API brand has greatly improved the efficiency of non-contact detection of body-in-white based on conventional laser radar, and has convincing excellent performance in speed, accuracy, flexibility, portability, repeatability and other aspects.

Problems encountered in production

With the development of human civilization and science and technology, the automobile industry has entered a new stage. In order to produce more excellent automobile products, the requirements for automobile manufacturing technology continue to rise. In the manufacturing process, smaller tolerance and higher efficiency are the key elements of the current automobile manufacturing process. According to Forest&Sullivan's 2019 white paper "A Paradigm Shift of In-Line Inspection in Body-in-White", 97% of the industry sample respondents believe that the improvement of internal efficiency is the key factor of Industry 4.0 system.
One of the key points is the dimension inspection process. The industry is promoting the concept of measuring the moving BIW on the assembly line. The proposal of this concept means that hundreds of high-precision measurements will be completed quickly on the production line, and the whole detection process will not delay the operation of the production line. This is a major challenge for the detection process.
Forest&Sullivan's analysis of the size measurement system in 2019 showed that Laser Radar technology is the "best in class" technology to provide online detection of body-in-white. It said: "Laser Radar is a fully automatic and multifunctional system, which introduces non-contact measurement into the production line. The system can run without targets and detect with high accuracy. This is a novel method, which has good measurement capability for surface and feature details, and its function can meet all the requirements of body-in-white dimension detection. Laser Radar The measuring system has advantages over traditional CMM or other measuring equipment in many aspects, especially in terms of convenience and efficiency. "
API has always been paying close attention to the latest concepts and objectives of the industry for online detection of body-in-white. Through a large number of industry surveys and exchanges, it was learned that the current laser radar measurement technology could not really fully achieve the highest goal of online detection, and then based on the brand's accumulation in the field of high-performance sensors, high-precision dimensional measurement in the past 40 years, and targeted combination with the actual needs of the industry, The new dynamic 9D laser radar (9D LADAR) has been developed, which has greatly improved and improved compared with the traditional laser radar in many aspects, such as accuracy, efficiency, flexibility, repeatability, and so on, providing the automobile manufacturers with a measurement solution closer to the highest manufacturing standard in the industry.

Figure 1: API 9D lidar body-in-white inspection

Breakthrough dimensioning solutions
API brand 9D laser radar (9D LADAR) adopts optical frequency domain interferometry (OFCI), which is the world's first laser radar equipment based on laser interferometry and capable of non-contact measurement. It has extremely high measurement accuracy and extraordinary measurement efficiency, and can quickly capture workpiece size and surface geometric data.
The 9D lidar based on OFCI technology will generate broad-spectrum optical interference, detect interference signals and collect measurement data when working. Its sensitivity is more than 100 times higher than that of conventional lidar, so it can provide higher measurement accuracy and better measurement efficiency than conventional lidar. The 9D laser radar provides measurement accuracy of micron level, data acquisition rate of 20kHz, and is not easy to be affected by external environment during measurement, effectively avoiding the problems such as large influence of material reflectivity, limited range of incidence angle, and susceptibility to environmental noise in the use of conventional laser radar.
Technical improvement of 9D lidar compared with conventional lidar
1. Speed: 9D laser radar (9D LADAR) collects measurement data at 20000 points per second, and the scanning speed reaches 0.2 seconds/cm ². At present, it is known that conventional laser radar only has a data acquisition rate of up to 1000 points/second and a maximum of 1 second/cm ² The scanning speed of.
2. Accuracy: 3D measurement accuracy of 9D lidar is 25 μ m+6 μ M/m, while the 3D accuracy of conventional lidar is 20 μ m+14.5 μ m/m.
3. Flexibility: 9D laser radar has a horizontal ± 320 ° angle range, and the incidence angle ≥ 85 °; Conventional laser radar usually only has horizontal ± 180 ° horizontal angle range and 45 ° incidence angle.
4. Portability: The 9D laser radar is compact in design, with integrated control box, and the overall weight is only 10.4 kg; However, the weight of conventional lidar is usually up to 30 kg, and it is equipped with an additional external control box. In terms of size, the 9D laser radar is also smaller than the conventional laser radar, which is more convenient to load in the industrial robot and gantry three coordinates or integrate in the production line.
5. Repeatability: the average repeatability error of 9D lidar is 35 μ m. 150 for conventional lidar μ m.

Solve the problems encountered in the production of conventional laser radar
In actual production, the measurement of a body-in-white often requires hundreds of positions that must be detected. In some links, the conventional laser radar measurement technology cannot achieve the best measurement effect due to its own functions and characteristics. The advent of the 9D laser radar (9D LADAR) has overcome the problems encountered by the conventional laser radar in actual production in the following aspects:
Problem 1: In the measurement, every time the position of the conventional laser radar changes, it must reposition its position relative to the body-in-white. Based on its performance, the realization of this positioning process is relatively cumbersome, and needs frequent cooperation with the scanning of the "positioning ball" to achieve, so that accurate measurement can continue to be carried out for the target body-in-white. Based on its own principle and excellent performance, the 9D laser radar greatly simplifies and even completely avoids the use of the positioning ball (Radian Laser Tracker cooperates with real-time accurate positioning).
Problem 2: The biggest problem of conventional lidar technology is the scanning speed. At present, the scanning speed of conventional lidar system is only 1000 points per second, while the scanning speed of API 9D lidar can reach 20000 points per second, which solves the problem of relatively slow measurement speed of conventional lidar in efficiency.
Problem 3: incident angle capability. The current conventional laser radar system can achieve accurate measurement of 45 ° incidence angle; The 9D laser radar can accurately measure parts with an incident angle of more than 85 °. This means that compared with conventional lidar, 9D lidar can measure the same amount of data by moving less positions.

Figure 3: API 9D lidar body-in-white measurement based on real-time and accurate positioning of Radian laser tracker

Joint solution of 9D lidar and 6-DOF laser tracker
For operations with extreme measurement accuracy requirements, the solution (as shown in Figure 3) of the combination of the 9D laser radar and Radian laser tracker of the same API brand can be used. At the same time, the Radian laser tracker can be used to provide real-time tracking and positioning for the 9D laser radar when the efficient and non-contact scanning function of the 9D laser radar is used to obtain a large amount of point cloud data. In this way, not only a large amount of point cloud data is obtained quickly and efficiently, but also the robot posture is infinitely accurate, which truly achieves the combination of extreme high accuracy and high efficiency.
conclusion
With faster scanning speed, wider range of incidence angle and higher data sampling rate, using API 9D laser radar (9D LADAR) for body-in-white measurement can improve the work efficiency by 4 times or more than using conventional laser radar; When there is a demand for extreme measurement accuracy, it can also cooperate with the API Radian laser tracker to conduct global real-time tracking, positioning and scanning measurement, which ensures the high quality and high standard of measurement and provides the ultimate measurement accuracy assurance while efficient detection.