Dual Evaluation Circuit for Steering Switch Fault Detection
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Solution Overview
Problem
Existing circuit arrangements for evaluating the switching states of actuating elements in motor vehicles, such as steering column switches, are prone to incorrect evaluations due to deteriorating contact quality, leading to potential safety hazards, and lack sufficient fault diagnosis capabilities, especially in detecting short circuits and soft shorts between contact surfaces.
Innovation Solution
A circuit arrangement with two evaluation circuits and a movable contact means that connects to a reference potential, allowing for separate switching and diagnosis modes, enabling reliable detection of switching states and fault diagnosis by evaluating output signals from both active and deactivated evaluation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single evaluation circuit is used to evaluate switching states, then the device complexity is low, but the reliability is insufficient due to contact quality deterioration and inability to detect faults
Solution Approach 1:
The evaluation system is divided into two independent evaluation circuits (first evaluation circuit and second evaluation circuit), each capable of independently evaluating switching states. This segmentation allows one circuit to perform evaluation while the other performs self-diagnosis, thereby improving overall reliability without requiring a complete system redesign
Solution Approach 2:
The circuit arrangement performs self-diagnosis in advance by using the deactivated evaluation circuit to check for faults before the active circuit begins its evaluation task. This preliminary action ensures that any contact quality issues or internal faults are detected before they can compromise the evaluation reliability
2Reliability
If two evaluation circuits are used to improve reliability, then the reliability increases, but the device complexity increases
Solution Approach 1:
Each evaluation circuit is designed to be multi-functional: it can serve as an active evaluation circuit or be deactivated to perform self-diagnosis. This universality means that the same hardware structure performs different functions at different times, reducing the need for additional dedicated diagnostic components and thereby limiting the increase in device complexity
Solution Approach 2:
The circuit arrangement operates in periodic cycles where one evaluation circuit is activated for evaluation while the other is deactivated for self-diagnosis, and their roles are periodically swapped. This periodic action allows continuous monitoring and evaluation without requiring both circuits to operate simultaneously, thus managing complexity while maintaining high reliability
3Area of stationary object
If contact surfaces are placed close together to reduce space, then the area is reduced, but short circuits between contact surfaces cannot be reliably detected
Solution Approach 1:
The self-diagnosis function provides continuous feedback about the condition of contact surfaces and internal circuitry. By monitoring output signals during both active and deactivated states, the system can detect abnormal current paths indicating short circuits between closely spaced contact surfaces, thereby maintaining reliability despite reduced spacing
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 provides a highly reliable and secure evaluation of switching states, enabling easy and reliable fault detection, thereby ensuring accurate determination of the actuating element's position and enhancing safety in safety-critical applications.
Implementation Method 1
a first evaluation circuit with a first voltage divider, which has first node points and a first tap for tapping off a first output signal of the first evaluation circuit
Data Source
AI summary
The invention relates to a circuit arrangement (100) for evaluating at least two switching states of an actuating element, having a moveable contact means (110) which is connectable to the actuating element, a first evaluation circuit (140a) with a first voltage divider, which has first node points (K1a, K2a, K3a, K4a, K5a) and a first tap (150a) for tapping off a first output signal (A1, A3, A5) of the first evaluation circuit (140a), at least one second evaluation circuit (140b) with a second voltage divider, which has second node points (K1b, K2b, K3b, K4b, K5b) and a second tap (150a) for tapping off a second output signal (A2, A4, A6) of the second evaluation circuit (140b), first contact surfaces (121a, 122a, 123a, 124a, 125a) which are each electrically connected to one of the first node points (K1a to K5a), and second contact surfaces (121b, 122b, 123b, 124b, 125b) which are each electrically connected to one of the second node points (K1b to k5b), wherein via the movable contact means (110), depending on the switching state of the actuating element at least one of the first contact surfaces (121a to 125a) and/or at least one of the second contact surfaces (121b and 125b) are electrically connectable to a predetermined reference potential (P). The invention also relates to a method for operating a circuit arrangement (100), and to a switching device having a circuit arrangement (100).