Capacitive Headrest Sensor for Precise Positioning
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Solution Overview
Problem
Existing headrest adjusting devices in motor vehicles often result in incorrect positioning, leading to potential head and neck injuries during crashes due to inadequate detection of the head's vertical and horizontal alignment relative to the headrest, as they can only sense extreme distances and not convex or concave curvatures effectively.
Innovation Solution
A capacitive proximity sensor with at least three transmitting or receiving electrodes, integrated into the headrest, that determines the headrest's position by analyzing capacitance values to accurately set the vertical target position, distinguishing between the head and neck, and includes a control unit to drive motorized adjustments for precise alignment, with optional additional electrodes for horizontal adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive proximity sensor with three electrodes is used to detect head position, then the headrest can be adjusted vertically, but the system cannot reliably distinguish between head and neck positions due to limited detection capability
Solution Approach 1:
The sensor is divided into multiple independently controllable electrode pairs arranged vertically. Each electrode pair can be activated separately to create alternating electric fields at different vertical positions, enabling the system to scan through different height levels and detect capacitance changes corresponding to head versus neck positions.
Solution Approach 2:
The sensor activates electrode pairs in alternating sequences, creating periodic alternating electric fields that sweep through the vertical detection range. This periodic activation pattern allows the control unit to compare capacitance values across different vertical positions and identify the target position where the head contacts the headrest.
2Productivity
If the headrest is adjusted quickly to the target position, then adjustment time is reduced, but the system may overshoot the target position
Solution Approach 1:
The control unit continuously monitors capacitance values from the electrode pairs during headrest adjustment and uses this feedback to determine when the target position is reached. The system compares real-time capacitance measurements against expected patterns to detect the moment of head contact, enabling precise stopping control that prevents overshooting while maintaining fast adjustment speeds.
3Device complexity
If only vertical adjustment is implemented, then the device complexity is reduced, but the headrest cannot be optimally positioned horizontally relative to the head
Solution Approach 1:
The same capacitive sensor with multiple electrode pairs serves dual functions: detecting vertical head position and providing information for horizontal positioning. By analyzing capacitance patterns across different electrode pairs, the system can infer horizontal offset and trigger horizontal adjustment, allowing one sensor to guide both vertical and horizontal positioning without requiring separate detection systems.
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 solution reliably avoids system-caused misadjustments by accurately determining the headrest's position relative to the occupant's head, ensuring the headrest is correctly aligned to minimize injury risk during crashes, and allows for precise and rapid adjustment without overshooting the target position.
Implementation Method 1
a capacitive proximity sensor with at least three transmitting or receiving electrodes, integrated into the headrest, that determines the headrest's position by analyzing capacitance values
Implementation Method 2
The prior art adjusting device uses the physical effect that the capacitance of the electrode arrangement due to the presence of the head in the alternating electric field changes in a characteristic manner
Data Source
AI summary
An adjusting device for a headrest of a motor vehicle seat is specified. The adjusting device comprises, in a first variant, a capacitive proximity sensor integrated into or designed for integration into the headrest having at least three transmitting electrodes spaced apart vertically from one another and having a common receiving electrode. In a second variant of the adjusting device, the proximity sensor has at least three receiving electrodes spaced apart vertically from one another and has a common transmitting electrode. In both variants, the adjusting device also has an actuating drive for motorized vertical adjustment of the headrest relative to the vehicle seat, as well as a control unit. The control unit here is designed to drive the transmitting electrodes or transmitting electrode for emission of an alternating electric field to determine from the received electrical signals detected from the receiving electrode or the receiving electrodes, respective associated measured capacitance values that contain information about the capacitance produced between each of the transmitting electrodes or receiving electrodes and the common receiving electrode or transmitting electrode, and to drive the actuating drive to establish a vertical target position of the headrest relative to the head position of a vehicle occupant as a function of the measured capacitance values.