Inertial sensor

Abstract

An inertial sensor includes an oscillator, a drive unit for oscillating the oscillator, a sensor for sensing the amount of inertia applied to the oscillator, and a failure diagnosis unit disposed between the oscillator and the drive unit. The drive unit includes a reference potential supply unit for supplying a reference potential to the oscillator, and a drive signal supply unit for supplying a drive signal to the oscillator based on a monitor signal received from the oscillator. The failure diagnosis unit includes a diagnosis unit for diagnosing a failure based on the value of a current supplied by the reference potential supply unit to the oscillator. The inertial sensor having this structure can detect a failure in the drive unit or the oscillator.

The invention claimed is: 
     
       1. An inertial sensor comprising:
 an oscillator; 
 a drive unit for oscillating the oscillator; 
 a sensor for sensing an amount of angular velocity applied to the oscillator; and 
 a failure diagnosis unit disposed between the oscillator and the drive unit, wherein 
 the drive unit includes:
 a reference potential supply unit amplifier for supplying a reference potential to an electrode of the oscillator; and 
 a drive signal supply unit for supplying a drive signal to the oscillator based on a monitor signal received from the oscillator, and 
 
 wherein the failure diagnosis unit measures the reference potential and includes:
 a diagnosis unit for diagnosing a failure based on a value of a current supplied by the reference potential supply unit to the oscillator in the drive unit or the oscillator based on the reference potential, and being disposed between the reference potential supply amplifier and the electrode of the oscillator.   
 
     
     
       2. The inertial sensor of  claim 1 , wherein
 the diagnosis unit diagnosis the failure in the drive unit based on a value of a current supplied by the reference potential supply amplifier to the electrode of the oscillator, 
 the diagnosis unit includes:
 a maximum value calculator for outputting a maximum value of the current; 
 a minimum value calculator for outputting a minimum value of the current; 
 a first comparator for outputting a failure signal when the maximum value is larger than a predetermined upper threshold; 
 a second comparator for outputting a failure signal when the minimum value is smaller than a predetermined lower threshold; and 
 a failure signal output unit for outputting a failure signal when one of the first comparator and the second comparator outputs a failure signal. 
 
 
     
     
       3. The inertial sensor of  claim 2 , wherein further comprising:
 a second failure diagnosis unit disposed between the oscillator and the drive unit, for diagnosing a failure in the drive unit or the oscillator; and 
 the failure signal output unit outputs different failure signals depending on whethera second failure signal output unit that outputs a failure signal when the failure signal output unit receives a failure signal from the first comparator or from the second comparatordiagnosis unit or the second diagnosis unit. 
 
     
     
       4. The inertial sensor of  claim 1 , wherein
 the diagnosis unit includes:
 a full-wave rectifier for full-wave rectifying the a voltage value of the reference potential; 
 a low-pass filter for smoothing an output signal from the full-wave rectifier; and 
 a comparator for outputting a failure signal when an output signal from the low-pass filter is smaller than a predetermined threshold. 
 
 
     
     
       5. The inertial sensor of  claim 1 , wherein
 the failure diagnosis unit includes:
 a resistor connected in series between the reference potential supply unit amplifier and the electrode of the oscillator; and 
 an amplifier for amplifying a voltage difference between both ends of the register resistor, wherein 
 
 the diagnosis unit diagnoses a failure based on a voltage value received from the amplifier. 
 
     
     
       6. The inertial sensor of  claim 5 , wherein
 the diagnosis unit includes:
 a maximum value calculator for outputting a maximum value of the current; 
 a minimum value calculator for outputting a minimum value of the current; 
 a first comparator for outputting a failure signal when the maximum value is larger than a predetermined upper threshold; 
 a second comparator for outputting a failure signal when the minimum value is smaller than a predetermined lower threshold; and 
 a failure signal output unit for outputting a failure signal when one of the first comparator and the second comparator outputs a failure signal. 
 
 
     
     
       7. The inertial sensor of  claim 5 , wherein
 the diagnosis unit includes:
 a full-wave rectifier for full-wave rectifying the a voltage value of the reference potential; 
 a low-pass filter for smoothing an output signal from the full-wave rectifier; and 
 a comparator for outputting a failure signal when an output signal from the low-pass filter is smaller than a predetermined threshold. 
 
 
     
     
       8. An inertial sensor comprising:
 an oscillator;   a drive unit for oscillating the oscillator;   a sensor for sensing an amount of angular velocity applied to the oscillator; and   a failure diagnosis unit for diagnosing a failure in the drive unit or the oscillator,   wherein the drive unit includes:
 a reference potential supply amplifier for supplying a reference potential to an electrode of the oscillator; and 
 a drive signal supply unit for supplying a drive signal to the oscillator based on a monitor signal received from the oscillator, and 
   wherein the failure diagnosis unit receives the reference potential, and diagnoses the failure by measuring the reference potential.