Rail Vehicle Position Integrity Using Track-Constrained UKF
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Solution Overview
Problem
Existing vehicle positioning systems for rail vehicles require significant infrastructure and are prone to failures due to inadequate maintenance, leading to inaccuracies and a need for higher safety integrity levels (SIL) like SIL 4, which current techniques struggle to achieve.
Innovation Solution
A vehicle positioning system utilizing track-constrained unscented Kalman filters (UKF) on SIL 0 platforms, combined with protection level functions on SIL 4 platforms, to estimate and validate vehicle position, ensuring reliability and accuracy by using IMU, odometry, and localization sensors, with statistical methods to maintain integrity risk below 10−9 per hour.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If track circuit and axle counting technique are used for positioning, then positioning can be achieved, but significant and expensive infrastructure is required and maintenance failures occur
Solution Approach 1:
The patent replaces mechanical/physical infrastructure (track circuits, axle counting blocks) with a sensor-based system using IMU, odometry, and localization sensors to achieve positioning without extensive physical installations on the track bed
Solution Approach 2:
The patent uses virtual positioning models and algorithmic processing to create a digital representation of vehicle position, eliminating the need for physical track circuits and axle counting infrastructure
2Measurement precision
If RFID transponder reader and tachometer technique are used for positioning, then positioning can be achieved, but significant infrastructure is required and positioning accuracy fails due to wheel spin or slide
Solution Approach 1:
The patent replaces mechanical wheel-based measurement (tachometer) with sensor-based measurement (IMU, odometry) that is not affected by wheel spin or slide, eliminating the source of positioning inaccuracy
Solution Approach 2:
The patent introduces localization sensors and odometry as intermediary measurement systems that indirectly determine position through sensor data fusion, avoiding direct dependence on wheel rotation measurements that can be inaccurate
3Reliability
If existing positioning techniques are used, then positioning can be achieved, but safety integrity level 4 compliance cannot be demonstrated
Solution Approach 1:
The patent implements continuous feedback through protection level functions that monitor positioning integrity and provide real-time verification, enabling demonstration of SIL 4 compliance through active safety monitoring
Solution Approach 2:
The patent performs preliminary safety assessments and integrity checks before positioning operations, using statistical methods to pre-verify system reliability and ensure integrity risk remains below 10^-9 per hour
Data Source
AI summary
A system and method of supervising vehicle positioning of a vehicle along a guideway where the vehicle comprising a supervisory controller, at least two controllers communicatively connected with the supervisory controller, an inertial measurement unit (IMU) and a speed measurement sensor includes receiving, by the controllers, speed measurements from the speed measurement sensor and motion measurements from the inertial measurement unit. The two controllers each estimate the along-track position of the vehicle using a track constrained UKF function based on the received speed measurements and motion measurements. The system executes protection level and protection level supervision functions on the supervisory controller to validate the along-track position estimates. The protection level supervision function uses a Stanford diagram verification technique.