Railroad Vehicle Location System with Sensor Bias Correction
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Solution Overview
Problem
Current systems for determining the location and location uncertainty of railroad vehicles face challenges in accuracy and reliability, particularly in dark territory and when dealing with inertial sensor errors and GPS instability.
Innovation Solution
A system that combines a global positioning system receiver, a predetermined track map, motion sensors with positive bias error correction, and an acceleration sensor, processed by a processor to verify sensor data, determine slip or slide conditions, and correct bias errors, thereby improving location and uncertainty determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motion sensors are used to determine change in location of the railroad vehicle, then the system can provide continuous location tracking, but the positive bias error accumulates over time reducing measurement precision
Solution Approach 1:
The system uses GPS position fixes as feedback to detect and correct accumulated bias errors in motion sensors. When a GPS fix is obtained, the system compares the GPS-derived position with the position calculated from motion sensors, identifies the bias error, and applies corrections to subsequent motion sensor measurements, thereby maintaining long-term accuracy.
Solution Approach 2:
The system dynamically changes the operational parameters of the location determination by switching between motion sensor-based continuous tracking and GPS-based periodic correction. This parameter change allows the system to exploit the continuous nature of motion sensors while periodically resetting accumulated errors using GPS references.
2Measurement precision
If GPS is used to determine position of the railroad vehicle, then location accuracy can be improved, but GPS signals may be unavailable in dark territory or tunnels
Solution Approach 1:
The system merges multiple location determination methods (GPS, motion sensors, acceleration sensors, odometer) into a unified hybrid navigation system. This combination allows the system to use GPS when available for high accuracy and switch to inertial and wheel-based methods when GPS is unavailable, ensuring continuous operation across all environments.
Solution Approach 2:
The system dynamically adapts its operational mode based on GPS availability. When GPS signals are present, the system uses GPS-based positioning with correction of motion sensor biases. When GPS signals are lost (in dark territory or tunnels), the system transitions to inertial navigation using acceleration sensors and motion sensors, maintaining operational versatility.
3Reliability
If multiple sensors are used to determine location and correct errors, then reliability and accuracy are improved, but device complexity increases
Solution Approach 1:
The processor performs multiple functions using the same sensor inputs: it determines basic position, calculates bias errors, detects slip/slide conditions, and applies corrections. This multi-functionality approach allows the system to achieve high reliability through comprehensive sensor utilization without proportionally increasing hardware complexity.
Solution Approach 2:
The system uses its own sensor data to self-diagnose and self-correct errors. The motion sensors and acceleration sensors monitor the vehicle's movement, and the processor automatically detects bias errors and slip/slide conditions, then applies corrections without external intervention, maintaining reliability while minimizing additional system complexity.
4Productivity
If motion sensors with positive bias error are used for continuous tracking, then productivity is improved, but manufacturing precision of the sensors cannot be enhanced to eliminate the bias
Solution Approach 1:
The system converts the harmful positive bias error into a detectable and correctable parameter. By continuously monitoring the discrepancy between motion sensor-based position and GPS-based position (when available), the system identifies the bias error and applies corrections, transforming the inherent sensor deficiency into a manageable parameter that does not compromise tracking productivity.
Data Source
AI summary
A system includes a global positioning system receiver to determine position of a railroad vehicle, a predetermined track map of possible coordinates of the vehicle, motion sensors providing a positive bias error to determine change in location of the vehicle, an acceleration sensor to determine acceleration of the vehicle, and a processor to vitally determine the location and the location uncertainty of the vehicle on the track map. The processor verifies one motion sensor with another motion sensor, determines a slip or slide condition of the vehicle from one of the motion sensors, determines speed and position of the vehicle from the acceleration sensor during the slip or slide condition, verifies the position of the vehicle from the global positioning system receiver based upon the track map, and corrects the positive bias error of the motion sensors using the position of the vehicle from the global positioning system receiver.