Angular Rate Sensor Malfunction Detection Circuit
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Solution Overview
Problem
Existing malfunction detection circuits for angular rate sensors lack high accuracy due to variations in driving impedance caused by factors like foreign matter attachment, temperature, and aging, especially with the downsizing of vibrators and the transition to semiconductor-type sensors, which affects zero point and sensitivity.
Innovation Solution
A sensing circuit with a malfunction detection system that includes a low-pass filter to generate a follow-up signal for setting a normal voltage range, using this signal to determine if the error voltage is within a defined range, and employing a latch circuit and timer to differentiate between momentary and long-lasting malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional malfunction detection circuit is used, then the detection is simple, but the detection accuracy is low due to variations in driving impedance caused by temperature, aging, and foreign matter attachment
Solution Approach 1:
The patent applies preliminary action by generating reference voltages in advance that represent the normal range of error voltage variations due to temperature and aging. These reference voltages are stored in the malfunction detection circuit before actual malfunction detection occurs, enabling accurate comparison when malfunctions are detected without requiring complex real-time analysis of all possible variation sources
Solution Approach 2:
The patent uses reference voltages as an intermediary element to mediate between the error voltage signal and the malfunction detection logic. By introducing these reference voltages that represent normal operational variations, the circuit can distinguish between acceptable variations (temperature, aging) and actual malfunctions (foreign matter attachment) without directly analyzing all underlying causes
2Volume of moving object
If the vibrator is downsized to semiconductor type, then the device size is reduced, but the detection accuracy deteriorates due to increased sensitivity to foreign matter attachment
Solution Approach 1:
The patent extracts the malfunction detection function from the vibrator itself and places it in a separate detection circuit that monitors the error voltage. This allows the vibrator to be downsized to semiconductor type while the detection circuit independently analyzes signals for foreign matter attachment, separating the size-reduction benefit from the detection accuracy requirement
Solution Approach 2:
The patent replaces mechanical monitoring of vibrator performance with an electrical signal analysis system. By substituting mechanical inspection with electronic detection of error voltage variations, the system can detect foreign matter attachment on miniaturized semiconductor vibrators through electrical signal characteristics rather than mechanical measurements
Data Source
AI summary
A sensing circuit for a vibration type of angular rate sensor comprises a vibrator, driving unit, follow-up signal forming unit, normal voltage-range setting unit, and determining unit. The driving unit drives the vibrator to vibrate at a predetermined amplitude by using, as a feedback signal, an error voltage signal in which an amplitude of vibration of the vibrator is reflected. The follow-up signal forming unit forms, by using the error voltage signal, a follow-up signal following up the error voltage signal at changes which are gentler than changes in the error signal. The normal voltage-range setting unit sets a range of a normal voltage for the error voltage signal by using the follow-up signal. The determining unit determines whether or not the sensor circuit is in a malfunctioning condition, by using an estimation as to whether or not the error voltage signal is within the range of the normal voltage.