Modern DUT Motion Options
Ludwig Mair, Business Development Manager Radar, NOFFZ Technologies
Autonomous driving and the associated sensor technology are currently experiencing an enormous push in development. For this vision to become reality and to ensure higher safety standards, not only more but also larger radar sensors will be installed in vehicles in the medium term. These sensors can detect their surroundings in even greater detail, allowing potential hazards to be recognized earlier.
In order to effectively validate and calibrate the various sensors, high-precision test systems are required that fulfil the specific requirements of these new sensor types. Both in the development phase and in sensor production, these test systems play a crucial role in ensuring that the calibrated radar sensors can guarantee the safety and performance of autonomous vehicles.
Requirements
The requirements for test systems for the validation and end-of-line (EOL) testing of radar sensors vary depending on the application and function of the sensor. Depending on the specified test requirements, different testers with measurement setups such as DFF (Direct Far Field) or CATR (Compact Antenna Test Range) are used.
For validation, flexibility and accuracy are crucial. The test systems must cover a variety of test scenarios to ensure the functionality and performance of the radar sensor under different conditions. High accuracy is required to enable precise measurements of the sensor parameters.
EOL test, on the other hand, focuses on reliability and automation. The test systems must be robust and reliable to withstand the demands of high-volume production. Fully automated test systems are required to ensure fast and efficient testing of radar sensors during the manufacturing process. They should also be scalable to ensure flexibility and cost-effectiveness.
The radar sensor’s function also plays an important role in determining the requirements for test systems. Short-range radar sensors must be able to precisely detect objects in the immediate vicinity of the vehicle. Mid-range radars require moderate range and resolution to cover medium distances. Long-range radars detect targets that are at a greater distance. Radar test systems must have the ability to represent all these different requirements in a compact design to validate or calibrate the respective sensor. Accurate test systems are essential for high-resolution imaging radars in order to capture and forward detailed object information with the radar sensors once they have been calibrated. This information is then analyzed in algorithms and converted into detected objects. There are also newly introduced variants such as forward-looking radar (FLR) and in-cabin sensing systems (ICS).
Overall, there are differentiated requirements for radar sensor test systems in terms of flexibility, accuracy, footprint, reflection suppression, test time and price, depending on the application (validation/EOL) and the type of sensor (short/mid/long range, imaging, FLR, ICS).
Current State of Development
To calibrate the sensor, it is necessary for it to be positioned horizontally (azimuth) and vertically (elevation) in relation to the target to determine the antenna characteristics of the radar sensor. Depending on the specific requirements of the test system, various positioning systems are available.
Fig. 1: The three common technologies for radar sensor motion within the NOFFZ test chamber:
(left) two independent actuators, (centre) a goniometer and (right) a robot.
Common options include robots, goniometers and customized, proprietary multi-axis positioning systems. Each of these systems offers different advantages in terms of flexibility, accuracy, speed and complexity.
Robots, for example, ensure a high degree of flexibility and are able to carry out complex movements. Goniometers guarantee precise positioning in azimuth and elevation. Proprietary multi-axis positioning systems can be customized to the specific requirements of the test but may offer less flexibility for future applications.
The state of the art lies in the continuous development of these positioning systems to realize an optimal balance between flexibility, accuracy and cost for sensor calibration.
NOFFZ Platform Solution – 6-Axis Robot
Our test system solutions include goniometers and other proprietary multi-axis positioning systems as well as the use of 6-axis robots from our partner Mitsubishi Electric. These robots are used both in laboratory operation and specifically for high-volume applications in series production. The use of a robot offers maximum flexibility for the motion of the sensor and enables a variety of measuring and testing functions to be carried out for different requirements.
Fig. 2: Integration of a 6-axis robot in an absorber chamber of a NOFFZ test system for precise and flexible positioning of the radar sensor during calibration.
The robots we use are characterized by their high precision, reliability and versatility. They enable complex motion patterns in all 6 degrees of freedom. In particular, the basic coordinate system can be freely selected.
With the help of an individual robot programming, the sensor motion can be customized and offers an optimal solution for a variety of applications in the field of sensor calibration. In order to optimize the accuracy of the robot path movement during the sensor motion, the system-related deviations from the ideal movement can be recorded using a special measuring method and taken into account in a path correction.
The use of 6-axis robots opens up new possibilities for sensor calibration and offers an efficient and reliable solution for both laboratory operation and series production.
Advantages of 6-axis robots
- Maximum flexibility for a wide range of motion requirements in 6 degrees of freedom (X, Y, Z, roll, pitch, yaw)
- Programming to different sensor placement positions for dual nest requirements to increase production throughput
- High movement speeds for fast and efficient test execution
- Adaptation to different sensor types by means of individual test specimen holders
- Integrated quick-change adapter for quick changeover to different sensor types
- Adaptation to different sensor types using individual test specimen holders
- Oscillating motion of the radar sensor in the target direction possible, e.g. for in-cabin monitoring applications
- Use for radome characterization to evaluate radar radiation properties
NOFFZ Platform Solution – Turntable with Coupled Goniometer
In addition to robots, we also use a specially developed 2-axis positioning system in our test systems. This method is suitable for laboratory operation as well as for small and medium volumes in production.
The 2-axis positioning system consists of a combination of a turntable and an attached goniometer. The turntable represents the azimuth movement, while the goniometer controls the elevation. Both movement axes are aligned with the beam center of the radar sensor in order to move the sensor in each of the two individual directions as well as together.
Advantages of the goniometer
- High positioning accuracy of the sensor motion around its beam center
- Adaptation to different sensor types by means of individual test specimen holders
- Integrated quick-change adapter for quick changeover to different sensor types
- Compact design with low reflection cross-section
- Best possible reflection suppression due to very good coverage with absorber material
- Cost-effective multi-axis positioning for laboratory, validation and small and medium volumes in series production
- Can be integrated into existing test chambers
Fig. 3: A goniometer on a turntable for precise positioning of the radar sensor in azimuth and elevation within a NOFFZ radar test system.
Our high-precision 2-axis and 6-axis positioning systems offer customized solutions for the validation and calibration of radar sensors. They guarantee maximum flexibility, accuracy and efficiency both in the laboratory and in series production. With our innovative test systems, you are ideally equipped to meet the increasing demands of autonomous vehicle sensor technology and maximize safety and performance.
