Work Vehicle Steering Control for GNSS-Loss Azimuth Drift
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Solution Overview
Problem
Existing work vehicles face challenges in maintaining accurate positioning and steering due to drift errors in azimuth angles during dead reckoning operations, particularly when GNSS signals are obstructed by obstacles, leading to reduced reliability and stability in automatic steering.
Innovation Solution
A work vehicle system that utilizes a positioning system, inertial measurement system, and a controller to estimate and correct azimuth angles by calculating a rate of change in azimuth error, ensuring stable steering control during transitions from reliable to unreliable GNSS conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead reckoning is performed using IMU signals when GNSS signals are obstructed, then the work vehicle can maintain steering control without GNSS, but the azimuth angle estimation accumulates drift errors over time
Solution Approach 1:
The system continuously monitors the difference between the first azimuth angle (from positioning system) and the second azimuth angle (from IMU) to calculate drift error and its rate of change. This feedback mechanism allows the system to detect and correct azimuth angle drift in real-time, maintaining measurement precision while preserving the ability to operate without GNSS signals.
Solution Approach 2:
The system calculates the rate of change in azimuth error during periods when GNSS signals are available (first state) and stores this information for later use. This preliminary action prepares correction data in advance, so when GNSS signals become obstructed (second state), the system can apply pre-calculated correction rates to maintain accurate azimuth angle estimation.
2Productivity
If the system switches to dead reckoning mode when GNSS reliability decreases, then the vehicle can continue operation, but positioning accuracy deteriorates due to accumulated drift
Solution Approach 1:
The control device continuously compares the first position (from positioning system) and second position (from IMU integration) to calculate positioning drift. This feedback allows the system to maintain continuous operation while correcting position estimation errors, thereby preserving positioning accuracy during dead reckoning mode.
Solution Approach 2:
The system pre-calculates drift error characteristics during reliable GNSS operation and stores correction parameters. When switching to dead reckoning mode, these pre-prepared correction data enable the system to maintain positioning accuracy without interrupting continuous operation.
3Adaptability or versatility
If the system uses only IMU-based azimuth angle estimation during dead reckoning, then the vehicle can operate independently of GNSS, but steering accuracy decreases due to drift errors
Solution Approach 1:
The system implements continuous feedback by comparing IMU-based azimuth angle with positioning system-based azimuth angle. This feedback loop enables the system to operate independently of GNSS while maintaining steering accuracy through real-time correction of drift errors based on the calculated rate of change in azimuth error.
Solution Approach 2:
The system prepares correction data for azimuth angle drift during periods of reliable GNSS operation. This preliminary preparation of correction parameters allows the system to switch to independent IMU-based operation while maintaining steering accuracy through application of pre-calculated correction rates.
Data Source
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.