Dead Reckoning Position Verification System
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Solution Overview
Problem
Autonomous and semi-autonomous machines face challenges in accurately detecting position errors due to slow changes in GPS signals, which can lead to incorrect positioning, especially in environments with noise and propagation delays.
Innovation Solution
A system that includes a position sensing system, a dead reckoning system, and a controller to determine an initialization position, calculate a position using dead reckoning, and compare it to the sensed position, generating an error signal if the difference exceeds a predefined threshold, thereby verifying the accuracy of the sensed position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If GPS signals are used to determine machine position, then the machine can operate autonomously or semi-autonomously, but errors in GPS signals such as multi-path effects, system noise, and propagation delays make error detection difficult
Solution Approach 1:
The patent introduces dead reckoning as an intermediary system to verify GPS position data. The dead reckoning system independently calculates position based on motion sensors and compares it with GPS readings, acting as a mediator to detect GPS errors without requiring additional GPS satellites or complex signal processing
Solution Approach 2:
The system implements feedback by continuously comparing dead reckoning position estimates with GPS measured positions. When discrepancies exceed a threshold, the system generates error signals and can switch to relying on dead reckoning, creating a closed-loop verification mechanism that improves reliability while maintaining autonomous operation
2Speed
If GPS position changes are small and occur slowly, then the machine is moving slowly, but detecting errors in such small position changes is more difficult
Solution Approach 1:
The system performs preliminary dead reckoning calculations continuously to establish expected position changes before GPS errors manifest. By pre-calculating where the machine should be based on its motion, the system can detect even small GPS errors that occur during slow movement, as the dead reckoning provides a baseline for comparison
3Measurement precision
If additional systems like IMU are added to supplement GPS, then position accuracy during GPS signal intervals is improved, but system complexity increases
Solution Approach 1:
The dead reckoning system serves multiple functions: it provides position estimation during GPS outages, verifies GPS accuracy during normal operation, and detects GPS errors through comparison. This multi-functionality improves measurement precision without proportionally increasing system complexity, as the same dead reckoning infrastructure serves both navigation and verification purposes
Data Source
AI summary
A system for determining an error in a sensed position of a machine includes a position sensing system, a dead reckoning system, and a controller. The controller is configured to determine a difference between a sensed position and a calculated position determined by dead reckoning. The difference is compared to an error threshold defining a maximum acceptable distance between the sensed position of the machine and the calculated position of the machine and an error signal generated if the difference exceeds the error threshold. A pair of offset dead reckoning processes may be used.