Weather Radar Gimbal Calibration Using Optical Encoder
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Solution Overview
Problem
The precision of weather-radar systems is limited by the quality of angular sensors, leading to calibration inaccuracies and high costs associated with high-precision sensors, while existing calibration methods, such as one-point calibration with digital protractors, fail to provide sufficient accuracy.
Innovation Solution
A method using a higher precision encoder to measure and compensate for errors in lesser precision sensors by generating and storing data on a radar system, which is then smoothed to improve position-control accuracy, employing optical encoder sensors to characterize and correct angular position errors introduced by resolvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision angular sensors are used, then measurement precision is improved, but device cost increases
Solution Approach 1:
A calibration table is introduced as an intermediary data structure that stores pre-calculated correction values. This calibration table acts as a mediator between the low-precision angular sensor and the desired high-precision output, allowing the system to achieve accurate measurements without requiring expensive high-precision sensors. The calibration table contains correction values that compensate for sensor errors across the full range of motion.
Solution Approach 2:
The system performs preliminary calibration by rotating the antenna through its full range of motion and storing correction values in a calibration table before normal operation. This preliminary action captures all necessary correction data that will be applied during subsequent measurements, enabling high-precision operation without requiring expensive real-time sensors.
2Ease of operation
If simple one-point calibration is used, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The calibration approach transitions from a static one-point calibration to a dynamic multi-point calibration that captures the antenna's behavior across its entire range of motion. The system dynamically rotates through multiple angular positions and collects correction data at each position, creating a comprehensive calibration table that adapts to the actual performance characteristics of the specific antenna-sensor assembly.
Solution Approach 2:
The calibration process changes multiple parameters simultaneously - angular position, correction values, and calibration data structure. By varying the angular position through the full range of motion and recording correction values at each position, the system creates a detailed calibration table that captures nonlinear errors and provides accurate corrections across all operating conditions.
3Ease of manufacture
If calibration data with discontinuities is used, then ease of manufacture is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary smoothing of the calibration data during the calibration phase, before normal operation begins. This preliminary action eliminates discontinuities and large corrections from the calibration table, ensuring that the antenna control system will operate smoothly during normal use without requiring excessive power to handle large correction values.
Data Source
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AI summary
A method of calibrating antenna-position detection associated with a radar system 300, the radar system including a first gimbal 30 and a first angle sensor 60 configured to detect an angular position of the first gimbal, includes mounting a second angle sensor 70 to the first gimbal configured to detect an angular position of the first gimbal. The first gimbal is rotated through each angular position of a set of the angular positions. A first set of data is generated with the first angle sensor that characterizes a detected angular position of the first gimbal. A second set of data is generated with the second angle sensor that characterizes a detected angular position of the first gimbal. A third data set is determined comprising differences, between the first and second data sets, in detected angular position at each first-gimbal angular position. The third data set is stored in a memory device 340.