Pedestrian Sensing System with Piezoelectric Bumper Sensors
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Solution Overview
Problem
Current pedestrian sensing systems for vehicles, particularly in taller vehicles with a bonnet leading edge height greater than 760 mm, struggle to meet the requirement of a total response time less than the pedestrian Head Impact Time due to limited sensing capabilities and deployment mechanisms, which are also prone to false activations from non-pedestrian objects.
Innovation Solution
The implementation of multiple piezoelectric sensors directly attached to the vehicle bumper fascia, generating voltage signals upon impact, with a processing system that compares these signals to predetermined thresholds to differentiate between pedestrian and non-pedestrian impacts, and triggers hood deployment only when necessary, thereby reducing response time and avoiding false activations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensors are placed away from the fascia surface to meet manufacturer requirements, then false activations from non-pedestrian objects are reduced, but sensing time increases and response capability deteriorates
Solution Approach 1:
The patent introduces an intermediary processing system that analyzes sensor signals to distinguish between pedestrian and non-pedestrian impacts. Multiple sensors (accelerometers, pressure sensors, contact sensors) are positioned at optimal locations, and their signals are processed by a control unit that applies algorithms to differentiate impact types, thereby reducing false activations without requiring sensors to be placed far from the fascia surface.
Solution Approach 2:
The sensing system is divided into multiple independent sensor units distributed across the bumper fascia. Each sensor monitors a specific zone, and the control unit processes signals from each sensor individually before making a deployment decision. This segmentation allows for precise localization of impacts and better differentiation between pedestrian and non-pedestrian objects.
2Adaptability or versatility
If the bonnet leading edge height is increased for taller vehicles, then vehicle design flexibility is improved, but the time available for hood deployment before head impact decreases
Solution Approach 1:
The system performs preliminary sensing and analysis of impact characteristics before the actual head impact occurs. By detecting the impact event early through the sensor array and processing the signal to confirm it is a pedestrian impact, the system initiates hood deployment in advance, ensuring the hood reaches the safe position within the reduced Head Impact Time available in taller vehicles.
Solution Approach 2:
The hood deployment mechanism uses dynamic control with variable speed actuation. The hood actuator adjusts its movement speed based on the detected impact severity and remaining time before head contact, enabling faster deployment in taller vehicles where time is more critical, while maintaining controlled deployment in standard-height vehicles.
3Reliability
If pressure tubes are embedded in bumper foam behind the fascia, then false activations are reduced, but sensing time increases to 22-25 milliseconds and deployment width is limited
Solution Approach 1:
The patent merges multiple sensing technologies (accelerometers, pressure sensors, contact sensors) into a single integrated sensing system on the bumper fascia. This combination allows the system to leverage the fast response of surface-mounted sensors while using signal processing algorithms to achieve the false activation resistance previously obtained only by embedding sensors deep in the foam structure.
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
This solution enables a rapid response time of approximately 8-10 milliseconds, allowing for effective hood deployment before pedestrian impact and distinguishing between deployable and non-deployable events, thus enhancing safety in taller vehicles while avoiding unnecessary deployments.
Implementation Method 1
fixing at least two piezoelectric sensors to a vehicle bumper fascia; reading an electrical signal defining a voltage signal from each of the at least two piezoelectric sensors, the voltage signal from each of the at least two piezoelectric sensors generated in response to an impact of an object with the fascia
Data Source
AI summary
A method for operating an automobile vehicle pedestrian sensing system includes: embedding multiple piezoelectric sensors in a vehicle bumper fascia, each generating a voltage in response to an impact of an object with the fascia; retrieving multiple threshold values from a memory, each assigned to one of the sensors; reading the voltage from each of the sensors; grouping individual sensors into multiple different logic circuits, each including at least two of the sensors; determining for each sensor in each of the logic circuits if the voltage is greater than the assigned threshold value; creating a positive signal following any one of the logic circuits when the voltage is determined to be greater than the assigned threshold value for the sensors grouped into the one of the logic circuits; and generating a hood deployment system deployment signal when the positive signal is output from all of the logic circuits.