Compressive Sensor Packaging for Pedestrian Impact Detection
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Solution Overview
Problem
Current pedestrian impact detection systems face challenges in extending sensitive areas to vehicle front end corners, where glancing impacts may not provide sufficient compression for compressive sensors to operate effectively, and existing designs often prioritize occupant safety over pedestrian impact sensor integration, leading to non-linear load transfer characteristics that complicate sensor integration and adaptability across different vehicle models.
Innovation Solution
A compressive sensor system with adjustable response characteristics is developed, utilizing energy absorbers with different compressibility in series and parallel arrangements, combined with multiple energy absorbing materials to manage load transfer and enhance sensitivity, allowing for flexible tuning and improved detection of impacts at various vehicle areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If compressive sensors are installed at vehicle front end corners to extend sensitive area, then pedestrian impact detection coverage is improved, but glancing impacts at corners do not provide sufficient compression for sensor operation
Solution Approach 1:
A reaction force member is introduced as an intermediary element between the impactor and the compressive sensor. This mediator converts glancing impacts at corner locations into effective compressive forces on the sensor by providing a surface against which reaction forces can act, enabling reliable sensor operation even when direct compression is insufficient
Solution Approach 2:
The reaction force member changes the force transmission parameters by redirecting impact forces through its geometry and material properties. It transforms the force vector from a glancing blow into a compressive load on the sensor, effectively altering how impact energy is transmitted to the sensing element
2Strength
If energy absorbing cross beam structure is used to meet low speed impact requirements, then occupant safety is improved, but the structure does not extend laterally to outer front corners providing reaction force
Solution Approach 1:
The energy absorption function is segmented into two separate components: the energy absorbing cross beam for central impact zones and the reaction force member for lateral corner zones. This segmentation allows each component to be optimized for its specific function and location, with the reaction force member extending laterally to corners where the cross beam does not reach
Solution Approach 2:
The reaction force member extends the energy management system into the lateral dimension at corner locations where the traditional cross beam structure does not reach. This dimensional extension provides the necessary reaction force geometry for corner-mounted sensors without compromising the central energy absorption capability
3Measurement precision
If compressive sensor assembly is designed with inherent sensitivity characteristics, then sensor response is optimized, but the sensor is not adaptable for use over multiple vehicle product lines
Solution Approach 1:
The sensor system is made dynamically adjustable through the reaction force member, which can be configured with different geometries, materials, and mounting positions. This dynamic configurability allows the same sensor assembly to be adapted to different vehicle product lines by modifying the reaction force member rather than redesigning the entire sensor system
Solution Approach 2:
The reaction force member serves multiple functions: it provides structural support, transmits impact forces, enables sensor mounting, and acts as a tuning element for sensor sensitivity. This multi-functionality allows a single component to address multiple design requirements across different vehicle platforms, enhancing product line adaptability
4Reliability
If vehicle front end components are designed to meet damageability and injury criteria, then safety requirements are satisfied, but component stiffness versus compressibility balance creates non-linear load transfer characteristics complicating sensor integration
Solution Approach 1:
The reaction force member acts as an intermediary that linearizes the load transfer path to the sensor. By providing a dedicated force transmission path independent of the non-linear energy absorption characteristics of the cross beam, it simplifies the load transfer characteristics and makes sensor integration more predictable and less complex
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
The system provides repeatable and adaptable impact detection capabilities, effectively responding to diverse impact conditions across the vehicle front end, including corners, while maintaining cost-effectiveness and manufacturability, enhancing pedestrian impact mitigation without compromising vehicle styling or damageability criteria.
Implementation Method 1
energy absorbers with different compressibility in series and parallel arrangements, combined with multiple energy absorbing materials to manage load transfer
Implementation Method 2
the sensor tube is compressed, generating a gas pressure pulse in the tube which is transmitted to a pressure sensor, thereby detecting the impact
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A sensor assembly for a motor vehicle adapted for sensing impacts including pedestrian impacts. The sensor assembly includes first and second energy absorbing elements formed of differing materials which couple an applied force to the vehicle to a compressive force acting on a compressive sensor element. The first and second energy absorbers are combined in a manner to tune the response between the applied force and forces acting on the compressive sensor to provide desired response characteristics. The first and second energy absorbers can be configured to produce force flow paths which further aid in response tuning. Another embodiment utilizes an energy absorber having a shaped cross section which focuses and balances impact force is applied to the compressive sensor.