Crash Detection Arrangement With Dynamic Threshold Adjustment
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Solution Overview
Problem
Conventional crash detection systems struggle to differentiate between high-speed and low-speed crashes within a short time frame, leading to potential unnecessary activation of safety devices in low-speed crashes, as the determination of crash severity is heavily dependent on the stiffness of vehicle parts rather than the impact severity.
Innovation Solution
A crash detection arrangement that calculates a classification parameter based on the acceleration signal during a classification time period before the initiation criterion is met, modifying the crash evaluation algorithm to set dynamic threshold values for determining the severity of the crash, allowing for early and appropriate activation of safety devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the processor processes the acceleration signal for a predetermined length of time to determine change in velocity, then the crash severity evaluation becomes more accurate, but the response time for safety device activation is delayed
Solution Approach 1:
The system performs preliminary classification of the crash signal within the first 8 milliseconds to determine whether the event is a hard or soft crash before completing the full velocity change calculation. This preliminary action allows the system to make early decisions about safety device activation without waiting for the complete processing period, thus reducing response time while maintaining evaluation accuracy.
Solution Approach 2:
The crash detection process is segmented into two distinct phases: a classification phase (first 8 milliseconds) that determines crash type, and a subsequent evaluation phase that completes the velocity change calculation. This segmentation allows independent optimization of each phase, enabling early activation decisions based on classification results while the full evaluation continues in parallel.
2Loss of time
If the predetermined acceleration threshold is set low to detect severe crashes early, then the response time improves, but false activation in low-speed crashes increases
Solution Approach 1:
The system dynamically adjusts the threshold for safety device activation based on the crash classification. For hard crashes (high deceleration), a lower velocity change threshold is applied, enabling rapid activation. For soft crashes (low deceleration), a higher threshold is applied, preventing false activation. This dynamic threshold adjustment allows the system to respond quickly to severe crashes while maintaining reliability in low-speed events.
Solution Approach 2:
The system changes the evaluation parameters (threshold values) based on the classification results. When a hard crash is classified, the system uses parameters optimized for rapid detection and activation. When a soft crash is classified, different parameters are used that require higher velocity change to trigger activation, thereby preventing false positives while maintaining appropriate response time for each crash type.
3Measurement precision
If the crash detection system waits for the full processing period to determine crash severity, then the evaluation accuracy improves, but the safety device activation is delayed
Solution Approach 1:
The system performs preliminary classification of the crash signal within the first 8 milliseconds to determine whether the event is a hard or soft crash before completing the full velocity change calculation. This preliminary action allows the system to make early decisions about safety device activation without waiting for the complete processing period, thus reducing response time while maintaining evaluation accuracy.
Solution Approach 2:
The system uses feedback from the classification phase to adjust the evaluation process. When a hard crash is detected in the classification phase, the system activates safety devices based on this intermediate information rather than waiting for full processing. The feedback loop allows the system to adapt its response strategy based on real-time signal characteristics, balancing accuracy and speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables swift and accurate differentiation between high-speed and low-speed crashes, ensuring timely and appropriate deployment of safety devices, reducing the risk of unnecessary activation during low-speed events.
Implementation Method 1
The crash sensor is usually an accelerometer which is connected to a processor within the control unit to provide a signal to the processor which is indicative of the acceleration applied to the vehicle
Data Source
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AI summary
A crash detection arrangement, to be installed in a motor vehicle, for detecting a crash and providing a control signal for controlling a safety device in the event that a crash is detected, the arrangement comprising an accelerometer and a control unit, the accelerometer being arranged to supply a signal to the control unit which is indicative of the acceleration of the vehicle, the control unit being adapted to: calculate a classification parameter based on the value of the signal from the accelerometer during a classification time period, which includes an interval of time before an initiation criterion was fulfilled; modify a crash evaluation algorithm in dependence upon the classification parameter; and perform the crash evaluation algorithm upon fulfilment of the initiation criterion to produce the control signal.