System and method for diagnosing characteristics of acceleration sensor

• US 5,506,454 A
• Filed: 05/10/1993
• Issued: 04/09/1996
• Est. Priority Date: 03/20/1991
• Status: Expired due to Fees

• Current Assignee: Hitachi Automotive Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Automotive Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Suzuki, Masayoshi, Fujita, Hirokazu, Matsukura, Tetsuo, Matsumoto, Masahiro, Hanzawa, Keiji
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Krishnan, Aditya
• Application Number:
  US08/059,069
• Time in Patent Office: 1,065 Days
• Field of Search: 307/10.1, 307/9.1, 280/734-736, 340/466, 340/467, 340/457, 340/429, 340/436-438, 180/272-273, 310/311, 310/317, 310/315, 310/319, 310/324, 310/326, 310/329
• US Class Current: 307/10.1
• CPC Class Codes: B60R 21/01 Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents electrical circuits for transmission of signals between steering wheel and the vehicle itself B60R16/027; for electrically actuating belt retractor locking means B60R22/343
• CPC Class Codes: B60R 21/0173 Diagnostic or recording means therefor
• CPC Class Codes: G01P 15/04 for indicating maximum value
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups
• CPC Class Codes: G01R 31/007 using microprocessors or computers

Abstract

An apparatus for diagnosing the characteristic of an acceleration sensor and a method for diagnosis thereof are disclosed. The acceleration sensor includes a movable electrode (or mass part) displaced in accordance with an acceleration and a fixed electrode disposed opposite to the movable electrode. In a diagnosis mode, a signal for diagnosis is applied to the fixed electrode so that an electrostatic force as a force corresponding to a predetermined acceleration is generated between the fixed electrode and the movable electrode. In the case where the acceleration sensor is sound, the movable electrode or mass part is normally displaced. A failure of the acceleration sensor, the deterioration thereof in performance, a change in characteristic thereof caused from the lapse of time, or the like is self-diagnosed by detecting a change in capacitance between the movable electrode and the fixed electrode upon generation of the diagnosis signal. The force corresponding to the predetermined acceleration may be an electromagnetic force or a mechanical oscillation based on a piezoelectric element.

Claims

1. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part applies one of an electrostatic force, an electromagnetic force and an external mechanical oscillation to said mass part on the basis of said diagnosis signal, wherein the acceleration sensor is a capacitance type acceleration sensor which detects the acceleration from a change in capacitance between a movable electrode serving as said mass part and a fixed electrode disposed opposite to said movable electrode, said means for applying said force corresponding to said predetermined acceleration to said mass part includes signal applying means for applying said diagnosis signal to said fixed electrode to generate an electrostatic force for displacing said movable electrode, and said self-diagnosing means detects a change in capacitance between said movable electrode and said fixed electrode upon generation of said diagnosis signal to diagnose the acceleration sensor.

9. An apparatus according to claim 1, wherein when said diagnosis signal is generated, a battery supply voltage is applied directly to said fixed electrode.

2. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part applies one of an electrostatic force, an electromagnetic force and an external mechanical oscillation to said mass part on the basis of said diagnosis signal, wherein the acceleration sensor is piezoresistive type acceleration sensor provided with a dead weight which serves as said mass part and an elastic support with a piezoresistive member which supports said dead weight, said means for applying said force corresponding to said predetermined acceleration to said mass part includes a fixed electrode for the exclusive use for diagnosis disposed opposite to said dead weight and signal applying means for applying said diagnosis signal to said fixed electrode to generate an electrostatic force for displacing said dead weight, and said self-diagnosing means detects a change in resistance value of said piezoresistive member or a change in capacitance between said dead weight and said fixed electrode upon generation of said diagnosis signal to diagnose the acceleration sensor.

3. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part includes a coil for generating an electromagnetic force on the basis of said diagnosis signal, said coil being wound about the acceleration sensor.

10. An apparatus according to claim 3, wherein when said diagnosis signal is generated, a battery supply voltage is applied directly to said fixed electrode.

4. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part applies one of an electrostatic force, an electromagnetic force and an external mechanical oscillation to said mass part on the basis of said diagnosis signal, wherein said self-diagnosing means has a function of diagnosing the presence and/or absence of a failure of the acceleration sensor from said diagnosis signal and the value of the output of the acceleration sensor or said diagnosis signal and a temporal change of the output value of the acceleration sensor until it reaches a predetermined level.

5. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part applies one of an electrostatic force, an electromagnetic force and an external mechanical oscillation to said mass part on the basis of said diagnosis signal, wherein said self-diagnosing means has a function of self-diagnosing a static characteristic of the acceleration sensor from said diagnosis signal and the value of the output of the acceleration sensor, said status characteristic of the acceleration sensor being a sensor output value characteristic which is to be primarily obtained for the acceleration.

6. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said means for applying said force corresponding to said predetermined acceleration to said mass part applies one of an electrostatic force, an electromagnetic force and an external mechanical oscillation to said mass part on the basis of said diagnosis signal, wherein said self-diagnosing means has a function of diagnosing a dynamic characteristic of the acceleration sensor from said diagnosis signal and a temporal change of the value of the output of the acceleration sensor until it reaches a predetermined level, said dynamic characteristic of the acceleration sensor being a sensor output transient response for the acceleration.

7. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said diagnosis signal is amplified using a charge pump circuit configured into an integrated circuit form and an amplified signal voltage is applied to said means for applying said force corresponding to said predetermined acceleration.

8. An apparatus for self-diagnosing a characteristic of an acceleration sensor provided with a mass part displaced in accordance with an acceleration for converting the displacement of said mass part into an electric signal to detect the acceleration of a moving object, comprising means for applying a force corresponding to a predetermined acceleration to said mass part by applying a signal for diagnosis to the acceleration sensor, means for self-diagnosing the characteristic of the acceleration sensor from an output of the acceleration sensor upon generation of said diagnosis signal, means for giving notice of a failure of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines the failure of the acceleration sensor, and means for correcting an output characteristic of the acceleration sensor in the case where the result of self-diagnosis by said self-diagnosing means determines that the output characteristic of the acceleration sensor has a change which is caused from a lapse of time, wherein said diagnosis signal is amplified using a transformer and an amplified signal voltage is applied to said means for applying said force corresponding to said predetermined acceleration.