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WO1989010568A1 - Transducteur - Google Patents

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Publication number
WO1989010568A1
WO1989010568A1 PCT/GB1989/000440 GB8900440W WO8910568A1 WO 1989010568 A1 WO1989010568 A1 WO 1989010568A1 GB 8900440 W GB8900440 W GB 8900440W WO 8910568 A1 WO8910568 A1 WO 8910568A1
Authority
WO
WIPO (PCT)
Prior art keywords
filaments
transducer
filament
support
inertial mass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1989/000440
Other languages
English (en)
Inventor
Dennis John Miles
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
UK Secretary of State for Defence
Original Assignee
UK Secretary of State for Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by UK Secretary of State for Defence filed Critical UK Secretary of State for Defence
Publication of WO1989010568A1 publication Critical patent/WO1989010568A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/097—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by vibratory elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
    • G01P2015/0822—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass
    • G01P2015/0825—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass
    • G01P2015/0828—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass the mass being of the paddle type being suspended at one of its longitudinal ends

Definitions

  • This invention relates to transducers and in particular, to miniature transducers used for measuring acceleration and having applications in vehicle navigation and guidance.
  • One type of miniature accelerometer known for this purpose is made from silicon and comprises a tension-sensitive filament formed as a double-ended tuning fork and supported within a framework which functions as an inertial mass.
  • this device has the limitation of being sensitive to temperature fluctuations and therefore requires some form of compensation.
  • An object of the present invention is to configure a plurality of tension-sensing elements so that common mode effects such as temperature-dependent output fluctuations are virtually eliminated and therefore little or no form of compensation is necessary.
  • the present invention therefore consists of a transducer comprising a support, an inertial mass connected thereto by at least two filaments, whereby movement of the support relative to the inertial mass in a certain direction causes a corresponding extension of one filament and compression of another, and sensing means incorporated in said two filaments for detecting said extension and compression.
  • the transducer may be of unitary construction and made from any elastic material, for example, silicon. Conventional photolithography and etching techniques may then be used to form the desired configuration if a silicon wafer or the like is used as a starting material.
  • the sensing means may comprise semi-conductor strain-gauges implanted in the filaments. An accurately adjusted amount of impurity can give the desired characteristics. A variation in tension in the filaments gives rise to a change in strain-gauge resistance which can be measured by a Wheatstone bridge.
  • the filaments are caused to vibrate transversely.
  • Each filament has a natural frequency of vibration whose value is a function of the dimensions of the filament, the tension applied to it and the elastic modulus and density of the material from which it is constructed. Any variation in tension in the filament will cause a corresponding change in frequency. Measurement of this frequency change can then be used to determine the magnitude of any acceleration to which the transducer has been subjected.
  • This embodiment requires the provision of means for initiating and sustaining the vibrations of the filaments. This may be achieved, for example, by exploiting the piezo-electric effect or the thermo-mechanical properties of the transducer material. If silicon has been chosen then it is possible to sputter a piezo-electric layer of zinc oxide or barium titanate onto the filaments. This technique is known in the field of electro-acoustics.
  • the thermal expansion of a silicon transducer (which has an Inherently high thermal conductivity) can be used as a thermo-mechanical drive mechanism.
  • This technique has hitherto been applied successfully to diaphragm pressure sensors.
  • a heating resistor is embedded in each filament by ion implantation and an alternating current at the natural frequency of vibration of each filament Is passed through each resistor.
  • the resulting cyclic temperature changes cause the filaments to expand and contract which results in a mechanical driving force. Vibrations of the filaments may be detected by a piezo-electric layer deposited onto each filament and connected to a frequency measuring circuit.
  • the thermally induced expansion and contraction may induce strains in a second implanted resistor.
  • the vibrating filaments may be arranged to vibrate in a plane perpendicular to the plane of the support and inertial mass or they may be double-ended tuning forks whose tines vibrate in anti-phase with one another and in the plane of the support and inertial mass. It is preferable, though not essential far the dimensions of the filaments to be such that the measured effect of the said compression and extension are substantially equal and opposite.
  • Figure 1 is a perspective view of the embodiment
  • Figure 2 is a plan view of the embodiment
  • Figure 3 is a cross-section along the line A-A of Figure 2
  • Figure 4 is a circuit diagram of a transducer drive and measurement circuit.
  • the embodiment is fabricated from a silicon wafer and comprises a support 1 and an inertial mass 2 connected together by three filaments 3, 4 and 5, two of which (4 and 5) are co-planar.
  • Filament 3 is located in the common plane of the upper face of the support 1 and inertial mass 2 and the filaments 4 and 5 are located in the common plane of the lower face of the support and inertial mass.
  • the three filaments 3, 4 and 5 are displaced laterally from one another allowing ease of manufacture by an etching process from opposite directions of the silicon wafer.
  • the particular configuration of the filaments ensures that the transducer has sons degree of torsional rigidity and also enables the provision of a differential output with good common mode rejection.
  • the support 1 and inertial mass 2 are typically 0.4 mm deep and the filaments have dimensions of, typically, 1 mm ⁇ 50 ⁇ m ⁇ 50 ⁇ m.
  • the transducer shown in Figure 2 is sensitive to accelerations or components thereof along one axis only, shown as the Z axis (see Figure 1).
  • An acceleration of the support 1 in the Z direction will cause the filaments 4 and 5 to be tensloned and the filament 3 to be compressed, owing to the presence of the inertial mass 2.
  • Sensing means incorporated in each of the filaments 3 and 4 comprise a vibrator for initiating and sustaining vibrations of each filament and a detector for monitoring the frequency of such vibrations.
  • the sensing means for the filaments comprise, in each case, a pair of implanted heating resistors 6 and 7, one of each pair acting as the vibrator and the other, as the detector.
  • the outputs from each detector are differenced to give a signal related to the applied acceleration.
  • the support of the trnasducer is attached to a vehicle, for example, whose accelerations are to be monitored.
  • a sense resistor R S is supplied with a constant current (of 5 mA) from a power supply Vs via a transistor 9.
  • a drive resistor R D is supplied with an alternating drive voltage and a DC bias from the output of an operational amplifier 10.
  • R S and R D correspond to the resistor pair 6 of Figure 2.
  • Two more operational amplifiers 11 and 12 amplify the alternating sense voltage of approximately 5 mV peak to peak developed across the sense resistor R S and apply it to an input of the operational amplifier 10.
  • Two diodes 13 and 14 limit the output signal appearing on line 15 to 4 volts.
  • the alternating drive voltage (of 4V peak to peak) supplied to the drive resistor R D causes thermal expansion and contraction of the filament 3.
  • this mechanical distortion of the filament induces strains in the sense resistor R S causing its resistance to vary sinusoidally.
  • a DC bias of 2V is applied in order that the voltage applied to the resistor swings from 0 to +4V so that only one heating pulse is generated in each cycle ie the sense voltage developed across the sense resistor R S oscillates at the same frequency as the drive voltage.
  • the oscillator circuit 8 has a quality factor Q of approximately 2000 and runs at, typically, 60 kHz.
  • a transducer embodied as shown in the drawings has a sensitivity of, typically, 20 Hz/g (where g is the acceleration due to gravity) over an operating range of ⁇ 100 g. Its differential form of output provides the advantage of nullifying any common-mode effects brought about, for example, by ambient temperature fluctuations.
  • the filament 5 of Figures 1 and 2 also incorporates a vibrator and detector similar to those of the filaments 3 and 4.
  • This provides the transducer with a means for measuring acceleration in the y direction if desired, by comparing f 4 with f 5 (where f 5 is the frequency of vibration of the filament 5 when subjected to n applied acceleration).
  • f 5 is the frequency of vibration of the filament 5 when subjected to n applied acceleration.
  • it enables any error in the z axis acceleration measurement, introduced by a simultaneous acceleration along the y axis, to be accounted for by making the following frequency comparisons f5 + -t
  • a transducer in accordance with the invention is not restricted solely to operation in conjunction with the closed loop circuit of Figure 4. Those skilled in the electronics art will be aware of possible commonplace alternative choices of components and their values which will still achieve the desired results. Furthermore, the transducer will function satisfactorily with an open-loop circuit.
  • the transducer may be used for navigation and guidance of vehicles although it is not limited to this application.
  • Three single axis transducers may be strapped to the vehicle and provide output signals relating to acceleration thereof in three, for example orthogonal, directions. Such information may be processed by the vehicle's navigation and guidance computer along with additional navigational data in order to guide the vehicle on some chosen trajectory.
  • the simplicity of the transducer's construction enables a robust and low-cost navigation and guidance system to be realised.
  • the transducer as an accelerometer, it will be appreciated that it may alternatively be used as a pressure or force sensor.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Gyroscopes (AREA)

Abstract

Un transducteur destiné au mesurage de l'accélération est réalisé dans une tranche de silicium et comporte trois filaments (3, 4) et (5) qui assurent l'interconnexion d'un support (1) avec une masse inerte (2). Ces filaments font office d'articulations permettant le mouvement de la masse inerte par rapport au support. L'inertie de la masse (2), couplée à une accélération du support (1) dans le sens des z, engendre une compression du filament (3) et un allongement des filaments (4 et 5). Les signaux produits par des moyens de détection sensibles aux variations de tension et incorporés dans les filaments (3 et 4) sont différenciés pour donner un signal en corrélation avec l'accélération appliquée. Dans un mode de réalisation, on fait vibrer les filaments au moyen de l'une de deux résistances de chauffage implantées, leurs fréquences de résonance étant déterminées par n'importe quelles forces externes qui leur sont appliquées. La deuxième résistance sert à détecter des vibrations, et les deux résistances font partie d'un circuit électrique en boucle fermée.
PCT/GB1989/000440 1988-04-25 1989-04-25 Transducteur Ceased WO1989010568A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8809757.1 1988-04-25
GB888809757A GB8809757D0 (en) 1988-04-25 1988-04-25 Transducer

Publications (1)

Publication Number Publication Date
WO1989010568A1 true WO1989010568A1 (fr) 1989-11-02

Family

ID=10635807

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1989/000440 Ceased WO1989010568A1 (fr) 1988-04-25 1989-04-25 Transducteur

Country Status (2)

Country Link
GB (1) GB8809757D0 (fr)
WO (1) WO1989010568A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5170665A (en) * 1989-08-08 1992-12-15 Denis Janiaud Accelerometric sensor with flectional vibratory beams
WO1999049323A1 (fr) * 1998-03-24 1999-09-30 Daimlerchrysler Ag Microcapteur dote d'une structure resonnante
US5962786A (en) * 1995-09-26 1999-10-05 Onera (Office National D'eudes Et De Recheres Aerospatiales) Monolithic accelerometric transducer
JP2011203228A (ja) * 2010-03-26 2011-10-13 Toshiba Corp 加速度センサ
JPWO2013089079A1 (ja) * 2011-12-12 2015-04-27 株式会社村田製作所 加速度センサ
CN111650401A (zh) * 2020-06-03 2020-09-11 西安交通大学 一种同平面贴装的金属基集成式谐振加速度计

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4479385A (en) * 1982-09-23 1984-10-30 The United States Of America As Represented By The Department Of Energy Double resonator cantilever accelerometer
GB2174500A (en) * 1985-05-04 1986-11-05 Stc Plc Accelerometer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4479385A (en) * 1982-09-23 1984-10-30 The United States Of America As Represented By The Department Of Energy Double resonator cantilever accelerometer
GB2174500A (en) * 1985-05-04 1986-11-05 Stc Plc Accelerometer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Transducers '85, 1985, Int. Conference on Solid-State Sensors and Actuators, IEEE, (New York, NY, US) T.S.J. LAMMERINK et al.: "Integrated Thermally Excited Resonant Diaphragm Pressure Sensor", pages 97-100 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5170665A (en) * 1989-08-08 1992-12-15 Denis Janiaud Accelerometric sensor with flectional vibratory beams
US5962786A (en) * 1995-09-26 1999-10-05 Onera (Office National D'eudes Et De Recheres Aerospatiales) Monolithic accelerometric transducer
WO1999049323A1 (fr) * 1998-03-24 1999-09-30 Daimlerchrysler Ag Microcapteur dote d'une structure resonnante
US6389898B1 (en) 1998-03-24 2002-05-21 Daimlerchrysler Ag Microsensor with a resonator structure
JP2011203228A (ja) * 2010-03-26 2011-10-13 Toshiba Corp 加速度センサ
US8497672B2 (en) 2010-03-26 2013-07-30 Kabushiki Kaisha Toshiba Acceleration sensor
JPWO2013089079A1 (ja) * 2011-12-12 2015-04-27 株式会社村田製作所 加速度センサ
CN111650401A (zh) * 2020-06-03 2020-09-11 西安交通大学 一种同平面贴装的金属基集成式谐振加速度计
CN111650401B (zh) * 2020-06-03 2021-05-07 西安交通大学 一种同平面贴装的金属基集成式谐振加速度计

Also Published As

Publication number Publication date
GB8809757D0 (en) 1988-06-02

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