Dynamic Safety Integrity Level Adjustment for Train Measurement Devices
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Solution Overview
Problem
Current train protection and control systems face operational constraints due to imprecise measurement values and large confidence intervals, particularly at higher safety integrity levels, leading to reduced speed or increased safety distances, which are not efficiently managed by existing devices.
Innovation Solution
A device that allows for flexible specification of safety integrity levels, enabling calculation of confidence intervals based on the specified level, allowing the same device to operate at different safety integrity levels, from SIL1 to SIL4, and can be dynamically adjusted during operation based on application or situation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high safety integrity level (SIL4) is specified for the device, then safety reliability is improved, but the confidence interval of measurement values increases leading to operational constraints
Solution Approach 1:
The device dynamically adjusts the confidence interval based on the specified safety integrity level. When SIL4 is required, a larger confidence interval is calculated to ensure safety; when lower SIL is acceptable, a smaller confidence interval is used to improve operational performance. This dynamic adaptation resolves the contradiction by making the confidence interval flexible rather than fixed.
Solution Approach 2:
The confidence interval parameter is changed according to the safety integrity level requirement. The device allows operators to specify different SIL levels (1-4), and automatically adjusts the confidence interval parameter accordingly. This parameter change enables the system to balance between safety reliability and measurement precision based on operational needs.
2Reliability
If a large confidence interval is used to ensure high safety integrity level, then safety reliability is improved, but operational performance deteriorates due to speed reductions and increased safety distances
Solution Approach 1:
The system dynamically adapts operational parameters based on the specified safety integrity level. When SIL4 is specified, conservative operations with larger safety distances and speed reductions are applied. When lower SIL levels are acceptable, the system transitions to more aggressive operations with smaller safety margins, thereby improving productivity while maintaining adequate safety.
Solution Approach 2:
Operational parameters such as speed limits and safety distances are changed based on the confidence interval derived from the specified safety integrity level. This allows the system to optimize productivity by using smaller safety margins when high safety integrity is not required, while still ensuring safety when SIL4 is specified.
3Adaptability or versatility
If the device is designed to operate at multiple safety integrity levels, then adaptability is improved, but device complexity increases
Solution Approach 1:
The device is designed with multi-functionality to operate at multiple safety integrity levels (SIL1-SIL4) using the same hardware platform. By implementing a universal architecture that can accommodate different SIL requirements through software configuration and dynamic parameter adjustment, the device avoids the complexity of maintaining separate hardware systems for each safety level.
Data Source
AI summary
A device for determining at least one measurement value related to a location and/or one or more movement variables of a track-bound vehicle. The device is configured such that a safety integrity level can be specified for the device. The device additionally ascertains a confidence interval which depends on the respective specified safety integrity level in response to the measurement value or at least one of the measurement values. The device can be used in a flexible manner and at the same time reduces operational constraints due to imprecise measurement values and large confidence intervals connected thereto. There is also described a method for operating such a device.