Automotive Radar Alignment Using Multi-Target Corner Reflectors
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Solution Overview
Problem
Current automotive radar alignment methods are error-prone, especially when dealing with variant vehicle configurations, as they rely on precise mounting tolerances and are susceptible to misalignment due to unknown heights and lateral positions of radar sensor units.
Innovation Solution
A system using multiple corner reflectors positioned at different distances from the radar sensor unit, forming a pattern with two horizontally and two vertically aligned targets, minimizes interference and allows for accurate alignment by determining and adjusting the elevation and azimuth of the radar sensor unit, even when mounted at different heights or lateral positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single corner reflector is used for radar alignment, then the alignment process is simple, but the signal-to-noise ratio is low and mounting tolerances must be very tight
Solution Approach 1:
The alignment system is divided into multiple independent corner reflectors (at least three, preferably four or more) positioned at different locations and distances from the radar sensor unit. Each reflector provides an independent measurement signal, allowing the system to segment the alignment task into multiple observations that can be processed to determine elevation and azimuth misalignment angles.
Solution Approach 2:
The patent introduces multiple spatial dimensions by positioning corner reflectors at different distances from the radar sensor unit along the longitudinal axis, and at different lateral and vertical positions. This multi-dimensional arrangement creates a three-dimensional measurement geometry that enables accurate determination of both elevation and azimuth angles without requiring tight mounting tolerances.
2Measurement precision
If three angle positions are used to determine vertical misalignment, then the measurement is more accurate, but three separate measurements are needed and the process becomes complex
Solution Approach 1:
Multiple corner reflectors are combined into a single alignment system where all reflectors are measured simultaneously by the radar sensor unit. The processing system combines the signals from all reflectors to calculate both elevation and azimuth misalignment angles in a unified process, eliminating the need for sequential three-position measurements.
Solution Approach 2:
The corner reflectors serve multiple functions simultaneously: they provide reference targets for both elevation and azimuth alignment, enable measurements at different distances to improve signal-to-noise ratio, and create a multi-dimensional measurement geometry. This multi-functionality reduces the overall complexity compared to separate measurement procedures.
3Adaptability or versatility
If the radar sensor unit is mounted behind the bumper for aesthetic reasons, then the vehicle appearance is improved, but the alignment becomes more difficult as the sensor is out of view
Solution Approach 1:
Corner reflectors are introduced as intermediary objects that mediate the alignment measurement process. Since the radar sensor unit is out of direct view behind the bumper, the corner reflectors serve as intermediate targets that the radar waves can reach and reflect back to the sensor, enabling indirect measurement and alignment of the hidden sensor unit.
4Reliability
If multiple corner reflectors at different distances are used, then the signal-to-noise ratio is improved and mounting tolerances are greater, but the alignment apparatus becomes more complex
Solution Approach 1:
The alignment apparatus is segmented into multiple corner reflectors positioned at different distances from the radar sensor unit. This segmentation provides diverse signal paths and improves the signal-to-noise ratio by allowing the system to select or combine signals from reflectors at optimal distances, while the modular nature of adding reflectors keeps the complexity manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the signal-to-noise ratio and reduces misalignment errors, providing greater mounting tolerances and ensuring accurate radar sensor unit alignment, especially for units integrated behind vehicle bumpers, by utilizing multiple targets to account for mislocation and misalignment.
Implementation Method 1
transmitting a radar wave from the radar sensor unit toward the pattern of targets and receiving at the radar sensor unit, radar waves reflected by the pattern of targets
Implementation Method 2
receiving at the radar sensor unit, radar waves reflected by the pattern of targets
Implementation Method 3
interference between reflected radar waves of the plural reflectors is minimized during calibration
Data Source
AI summary
A method and apparatus for determining misalignment of a radar sensor unit mounted to a vehicle includes providing targets on an alignment apparatus. A vehicle is located at predetermined location on a test station an exact given distance from the alignment apparatus. The actual locations and distances of the targets from each other and from radar sensor unit of the vehicle at the test station are known and pre-stored. At least one target is a greater distance from the vehicle than the other targets. The targets receive and return a radar wave from the radar sensor unit. The radar sensor unit determines locations and distances of the targets and compares with the given or actual locations and distances of the targets to determine misalignment of the radar sensor unit. A calibration program automatically calibrates azimuth and elevation to adjust for misalignment.