Steering Wheel Electrostatic Sensor Failure Diagnosis
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Solution Overview
Problem
Existing steering wheel systems with electrostatic capacitance sensors lack effective failure diagnosis methods for open and short circuit failures, leading to potential erroneous contact detection and reduced accuracy.
Innovation Solution
A steering wheel unit equipped with an electrostatic capacitance sensor, an energizing unit, and a failure diagnosis unit that performs continuous or periodic short circuit diagnosis when the vehicle is on and open circuit diagnosis when the power is switched on, using calculated impedance comparisons and contact detection variations to accurately diagnose failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electrostatic capacitance sensor is provided on the steering wheel to detect human body contact, then contact detection capability is improved, but failure diagnosis capability deteriorates
Solution Approach 1:
The system performs preliminary failure diagnosis by detecting open circuit failures when the vehicle power is turned on, before the driver makes contact with the steering wheel. This preliminary action ensures the sensor is functioning correctly before actual contact detection begins, resolving the contradiction by establishing reliability前提 for measurement precision.
Solution Approach 2:
The control unit continuously monitors the electrostatic capacitance sensor output and compares it against expected values. When deviations indicating potential failures are detected, the system provides feedback through warning signals to the driver. This feedback mechanism maintains both contact detection accuracy and failure diagnosis capability simultaneously.
2Reliability
If continuous failure diagnosis is performed to improve reliability, then diagnostic accuracy is improved, but false positive detection increases
Solution Approach 1:
Open circuit failure diagnosis is performed as a preliminary check when the vehicle is powered on but before the driver contacts the steering wheel. This timing ensures that any detected failures are genuine and not caused by transient contact conditions, thereby improving diagnostic accuracy while minimizing false positives.
Solution Approach 2:
The system performs failure diagnosis periodically at specific intervals (when power is on and at predetermined timings during operation) rather than continuously. This periodic approach maintains diagnostic accuracy while reducing the likelihood of false positive detections that could occur with constant monitoring under all conditions.
3Loss of time
If open circuit failure diagnosis is performed when power is switched on, then diagnostic timing is improved, but detection accuracy deteriorates due to potential contact
Solution Approach 1:
The system performs open circuit failure diagnosis at the predetermined timing when the vehicle power is turned on, which is before the driver typically makes contact with the steering wheel. This preliminary timing selection ensures both timely diagnosis and accurate detection by avoiding the period when contact is likely to occur.
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
Enhances the accuracy of failure diagnosis by performing open circuit failure detection at appropriate timings and using additional sensors for short circuit monitoring, improving the reliability of contact detection and reducing false positives.
Implementation Method 1
detect contact of a human body with respect to a steering wheel of a vehicle by an electrostatic capacitance sensor
Implementation Method 2
an energizing unit configured to pass an alternating current to the electrode
Data Source
AI summary
A steering wheel unit is equipped with an electrode which is provided on a steering wheel and constitutes an electrostatic capacitance sensor, a sensor circuit that passes an alternating current to the electrode, a comprehensive control unit adapted to energize the sensor circuit at a time of failure diagnosis, and a failure diagnosis unit that performs a short circuit failure diagnosis continuously or periodically when a power source of a vehicle is on, and performs an open circuit failure diagnosis when the power source of the vehicle is switched from off to on.