Autonomous Mobility Position Estimation via Wheel Odometry
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Solution Overview
Problem
Autonomous mobility apparatuses face challenges in continuing movement when GPS satellite signal reception is degraded due to obstacles, leading to suspended operations and difficulty in reaching destinations, especially with low-precision DGPS sensors and the need for precise route information setup.
Innovation Solution
The autonomous mobility apparatus includes a storage unit for the moving route, a current position acquiring unit, a wheel driving system, and a control unit that calculates wheel revolutions based on past movement data to estimate position and adjust direction using magnetic sensors, allowing continuous movement even without GPS signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the autonomous mobility apparatus stops to wait for GPS signal recovery, then the position estimation accuracy is maintained, but the productivity and ability to reach destination deteriorate
Solution Approach 1:
The patent implements dynamic switching between GPS-based positioning and odometry-based dead reckoning. When GPS signal is available, the system uses GPS for accurate position estimation. When GPS signal is lost, the system dynamically transitions to using wheel revolution counting and stored route information to continue navigation, allowing the apparatus to maintain movement without stopping while preserving position accuracy through the fallback mechanism
Solution Approach 2:
The system pre-stores route information including sequential position data and wheel revolution counts before GPS signal loss occurs. This preliminary action enables the apparatus to continue navigation using the stored odometry data when GPS becomes unavailable, eliminating the need to stop and wait for signal recovery while maintaining reasonable position estimation accuracy
2Device complexity
If the autonomous mobility apparatus uses low-precision DGPS sensor to reduce cost, then the device complexity is reduced, but the measurement precision of position deteriorates
Solution Approach 1:
The patent combines multiple positioning methods (GPS reception, odometry-based dead reckoning using wheel revolution counters, and pre-stored route information) into a hybrid navigation system. This merging allows the use of simple, low-cost sensors while achieving accurate position estimation through the complementary strengths of each method, particularly the odometry data that accumulates precise movement information over time
Solution Approach 2:
The system uses feedback from wheel revolution counters to continuously update and refine position estimates during GPS-denied periods. By comparing expected wheel revolutions based on stored route information with actual measured revolutions, the system can detect and correct positioning drift, maintaining accuracy without requiring expensive high-precision sensors
3Measurement precision
If the autonomous mobility apparatus stores detailed wheel feature values for each route section, then the measurement precision of position is improved, but the device complexity and ease of operation deteriorate due to troublesome setup
Solution Approach 1:
The system performs preliminary measurement and storage of wheel revolution data during normal GPS-operational phases. By accumulating and storing the relationship between wheel revolutions and actual distance traveled during periods when GPS is available, the system pre-calibrates odometry parameters without requiring manual setup, reducing the complexity burden while maintaining position calculation accuracy during GPS-denied operation
Data Source
AI summary
A mobility apparatus (10) includes a position acquiring unit (3) that acquires a current position using a satellite; a control unit (1) that controls wheels (7a, 7b) along a route based on the acquired current position; and number-of-revolutions measuring units (8a, 8b) that measure numbers of revolutions of the wheels (7a, 7b). If acquiring the current position using the satellite is disabled, the control unit (1) calculates distances per revolution of the wheels (7a, 7b) from a moving distance by using the satellite and the numbers of revolutions of the wheels (7a, 7b) measured during the period in which the mobility apparatus has moved by the moving distance, calculates numbers of revolutions of the wheels (7a, 7b) at a distance by which the mobility apparatus is to move after acquiring the current position is disabled, and causes the wheels (7a, 7b) to rotate by the calculated numbers of revolutions.