Gyrometer Calibration via Odometric Feedback
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Solution Overview
Problem
Current methods for vehicle navigation without GNSS, such as inertial and odometry, face limitations in accuracy and reliability, especially in complex environments and low-speed maneuvers, due to susceptibility to errors and the need for precise sensor calibration.
Innovation Solution
A method that calibrates a gyrometer using a model linking estimated and measured angular speeds, incorporating recursive filtering and optimization, with odometer data from at least two wheels to determine calibration parameters and minimize differences between gyrometer and odometric estimates, allowing for accurate movement estimation and orientation calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential odometry is used to estimate vehicle motion, then navigation can be performed without GNSS, but the method introduces significant errors due to wheel slippage, non-parallel wheels, and variable parameters
Solution Approach 1:
The patent combines gyroscope measurements with differential odometry measurements to create a hybrid navigation system. The gyroscope provides accurate angular velocity data that compensates for the errors inherent in differential odometry, while the odometry provides complementary information about vehicle motion. This merging of two measurement systems resolves the contradiction by maintaining navigation reliability without sacrificing measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the gyroscope measurements are used to correct and calibrate the differential odometry estimates in real-time. The system continuously compares the two measurement sources and uses the more reliable gyroscope data to adjust the odometry calculations, thereby maintaining high measurement precision while preserving the ability to navigate without GNSS.
2Measurement precision
If a gyroscope is used to determine heading, then accurate orientation can be achieved, but the gyroscope requires calibration to eliminate bias and scale factor errors that accumulate over time
Solution Approach 1:
The patent implements a self-calibration mechanism where the system uses differential odometry measurements during straight-line driving to automatically determine and correct gyroscope bias and scale factor errors. Instead of requiring external calibration equipment or complex manual procedures, the system serves its own calibration needs by exploiting natural driving conditions, thereby maintaining high heading precision without increasing device complexity.
Solution Approach 2:
The patent dynamically adjusts gyroscope calibration parameters (bias and scale factor) based on observed driving conditions and differential odometry comparisons. The system changes these parameters in real-time to optimize measurement precision, using statistical methods to identify and correct drift without requiring complex external calibration procedures.
3Ease of operation
If straight-line trajectory conditions are required for gyroscope calibration, then calibration can be performed using simple methods, but the calibration is restrictive and cannot be performed during turns or accelerated motion
Solution Approach 1:
The patent transitions from static calibration requirements (straight-line only) to dynamic calibration capabilities that work during various driving conditions including turns and acceleration. The system dynamically adapts its calibration approach based on the current motion state, using different measurement combinations and correction algorithms appropriate for each driving scenario, thereby maintaining ease of operation while significantly improving adaptability.
Solution Approach 2:
The patent performs preliminary identification of driving conditions and selects appropriate calibration strategies in advance. By detecting whether the vehicle is in straight-line motion, turning, or accelerating, the system prepares and applies the most suitable calibration method proactively, ensuring that calibration can proceed effectively under diverse conditions without requiring complex real-time adjustments.
4Measurement precision
If classical inertial navigation methods are used with high-precision sensors, then accurate position tracking can be achieved, but the position error increases proportionally to the square of time due to constant acceleration errors
Solution Approach 1:
The patent implements continuous calibration and correction of inertial navigation measurements using differential odometry data throughout the navigation process. Instead of performing calibration only at discrete time points, the system continuously compares gyroscope-derived position with odometry-derived position and applies real-time corrections, thereby maintaining high position measurement precision and preventing error accumulation over time.
Solution Approach 2:
The patent uses differential odometry as an intermediary reference system to correct the drift in inertial navigation measurements. The odometry measurements serve as a mediator that provides an independent check on the inertial navigation results, allowing the system to identify and correct accumulation errors without requiring external GNSS reference, thereby reducing position error growth over time.
Data Source
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AI summary
The invention relates to a method of calibrating a gyrometer (11) installed in a vehicle (1), said method being characterised in that it comprises the following steps: (a) acquiring, using the gyrometer (11), a measured angular velocity of the vehicle (1) and, using means (20) for measuring at least one magnitude that is representative of the angular velocity of the vehicle (1), acquiring measured values of said at least one magnitude that is representative of the angular velocity of the vehicle (1); and (b) determining, using data processing means (21), values of at least one parameter for calibrating the gyrometer (11), minimising a gap between a first estimated angular velocity of the vehicle (1) and a second estimated angular velocity of the vehicle (1), wherein - the first estimated angular velocity of the vehicle (1) is a function of the measured angular velocity and calibration parameters of the gyrometer (11), and - the second estimated angular velocity of the vehicle (1) is a function of the measured values of the at least one magnitude that is representative of the angular velocity of the vehicle (1).