Force Sensing Resistor Auxiliary Trace for Disconnection Detection
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Solution Overview
Problem
Current pressure sensitive transducer assemblies fail to easily detect disconnection from the control circuit, as they provide the same output voltage for both disconnection and rest states, making it difficult to diagnose issues like bad contact, loss of preload, and electronics failures, especially in critical applications like the automotive industry.
Innovation Solution
Incorporating an auxiliary trace with a constant resistance on the force sensing resistor that is not dependent on applied force, allowing for the detection of preload loss and electronics failures, and using a specific pattern of connection pins to differentiate disconnection from rest states, enabling more accurate diagnostic capabilities without additional connection pins or costly testing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard force sensing resistor is used without preload, then the assembly can detect pressure, but it cannot distinguish between disconnection and rest states
Solution Approach 1:
The force sensing resistor is segmented into multiple independent traces (first trace, second trace, third trace) instead of a single continuous trace. This segmentation allows each trace to serve different functions: the first two traces form the sensitive area for pressure detection, while the third trace provides a reference path that remains unaffected by pressure, enabling distinction between disconnection and rest states.
Solution Approach 2:
The third trace acts as an intermediary reference element that is electrically connected to the control circuit but mechanically isolated from the pressure-sensitive area. This intermediary trace provides a stable reference signal that allows the control circuit to differentiate between actual pressure events and disconnection events by comparing signals from the pressure-sensitive traces against the reference trace.
2Reliability
If preloaded force sensing resistor is used, then the substrates are touching in rest state, but the output voltage remains constant for disconnection and preload loss
Solution Approach 1:
The force sensing resistor is divided into multiple traces where the third trace serves as a reference that is not affected by preload changes. This segmentation enables the control circuit to compare the resistance of the pressure-sensitive traces against the stable reference trace, allowing detection of preload loss and other abnormalities.
Solution Approach 2:
The invention utilizes changes in resistance parameters of the force sensing resistor traces to detect different states. The third trace provides a constant reference resistance, while the first and second traces exhibit resistance changes based on applied pressure or preload conditions, enabling diagnostic capability through parameter comparison.
3Measurement precision
If additional contact pins or wires are added for testing, then continuity and connection can be checked, but the cost and complexity increase
Solution Approach 1:
The third trace serves multiple functions: it acts as a reference for pressure detection, enables disconnection detection, provides preload condition monitoring, and facilitates diagnostic capabilities. This multi-functionality eliminates the need for additional dedicated test pins or wires, reducing connector complexity while maintaining comprehensive diagnostic accuracy.
Solution Approach 2:
The diagnostic functionality is merged into the existing force sensing resistor structure by incorporating the third reference trace within the same component. This integration combines the sensing and diagnostic functions into a single element, avoiding the need for separate testing hardware and reducing overall system complexity.
4Manufacturing precision
If visual check or camera testing is used, then connector insertion can be verified, but assembly time and costs increase
Solution Approach 1:
The force sensing resistor with its third reference trace performs self-diagnosis by providing electrical signals that indicate its own connection status and operational condition. This self-service capability eliminates the need for external visual inspection or camera testing, allowing automated electrical verification that is faster and more integrated into the manufacturing process.
Solution Approach 2:
The mechanical visual inspection process is replaced with an electrical detection system using the third reference trace. The control circuit electrically verifies connector insertion and assembly correctness through resistance measurements, substituting slow visual methods with rapid automated electrical testing that increases productivity.
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 allows for cost-effective and easy implementation of diagnostic features that can detect disconnection, preload loss, and electronics failures, providing a warning signal for potential assembly issues and improving the accuracy of preload condition detection without increasing assembly time or costs.
Implementation Method 1
a force sensing resistor with connection means, said force sensing resistor comprising: first and second substrates each having inner surfaces, wherein at least one of the substrates is flexible in order to move towards the other one of the substrates in response to an applied force
Implementation Method 2
the resistive layer contacts and electrically connects fingers of the first set and fingers of the second set together with a resistance dependent upon resistivity of the resistive layer and dependent upon the applied force
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Pressure sensitive transducer assembly (14) comprising a force sensing resistor (16), said force sensing resistor comprising: first and second substrates (20, 22); at least a first and a second electrically conductive traces (28, 30) on the inner surface of the first substrate including interdigitated fingers (32, 34) defining a sensitive area (36); and a resistive layer (38) facing the sensitive area, characterized by an auxiliary trace (50) on the inner surface of the first substrate connecting the first trace to the second trace through a constant resistance (51) which is not dependent on the force applied to the substrates, said resistance (51) being of a value largely greater than the value of the resistance which can be measured indirectly between the fingers (32, 34) when an external force is applied to the substrates. A system and a control method are also proposed.