Work Vehicle Azimuth Correction During GNSS-Denied Steering
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Solution Overview
Problem
Existing work vehicles face challenges in maintaining accurate azimuth angle estimation during dead reckoning operations due to accumulated drift errors when GNSS signal reception is hindered by obstacles, leading to instability in automatic steering.
Innovation Solution
A control system that utilizes a combination of GNSS and IMU sensors to estimate the work vehicle's position and azimuth angle, incorporating an extended Kalman filter to correct azimuth errors by calculating the rate of change in azimuth error, ensuring stable steering control during transitions in GNSS reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead reckoning is performed using IMU signals when GNSS signals are unavailable, then positioning can continue in obstructed environments, but azimuth angle estimation accuracy deteriorates due to accumulated drift errors
Solution Approach 1:
The system pre-calculates the rate of change in azimuth error during periods when GNSS signals are available (first state). This preliminary calculation stores correction characteristics that can be applied later when GNSS signals are unavailable, allowing the system to compensate for drift errors without real-time GNSS data.
Solution Approach 2:
The system continuously monitors the difference between the first azimuth angle (from GNSS/INS integration) and the second azimuth angle (from IMU only) to calculate the rate of change in azimuth error. This feedback mechanism enables dynamic correction of drift errors during dead reckoning operation, improving azimuth angle estimation accuracy while maintaining positioning availability.
2Duration of action of stationary object
If the system switches to dead reckoning mode when GNSS reliability decreases, then positioning continuity is maintained, but steering control accuracy deteriorates due to drift errors
Solution Approach 1:
The system prepares correction data by calculating the rate of change in azimuth error during GNSS-available periods. This preliminary preparation ensures that when switching to dead reckoning mode, the system already has correction characteristics ready to apply, maintaining steering control accuracy throughout the transition and duration of GNSS-denied operation.
Solution Approach 2:
The system dynamically changes the azimuth angle parameter by applying correction based on the pre-calculated rate of change in azimuth error. This parameter adjustment compensates for drift errors in real-time during dead reckoning, maintaining steering control accuracy while preserving positioning continuity throughout the operation.
3Adaptability or versatility
If the system uses only IMU data for azimuth angle estimation during dead reckoning, then positioning can operate without GNSS signals, but estimation errors accumulate over time
Solution Approach 1:
The system performs preliminary calculation of the rate of change in azimuth error during periods when GNSS signals are available. This advance preparation creates a correction model that can be applied during dead reckoning operation, enabling the system to operate adaptably in obstructed environments while compensating for IMU drift errors through the pre-established correction relationship.
Solution Approach 2:
The system implements feedback by continuously calculating the difference between GNSS-based azimuth angle and IMU-based azimuth angle to determine the rate of change in azimuth error. This feedback loop enables the system to adapt to drift conditions and apply appropriate corrections, maintaining measurement precision while preserving the ability to operate in GNSS-obstructed environments.
Data Source
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Figure 3
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AI summary
A work vehicle includes a positioning system to output first chronological data, an inertial measurement system to output second chronological data based on measurement values from an acceleration sensor and an angular velocity sensor, and a controller to, in a first state when positioning by the positioning system is possible, consecutively estimate a first azimuth angle based on the first and second chronological data, consecutively estimate a second azimuth angle based on the second chronological data, calculate a rate of change in azimuth error of the second azimuth angle based on a difference between the consecutively-estimated first and second azimuth angles in the first state, and, in a second state associated with a decreased reliability of positioning, perform steering control based on an azimuth angle resulting from causing the second azimuth angle estimated based on the second chronological data to be corrected based on the rate of change in azimuth error.