JPH03503932A - Accelerometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Accelerometer The present invention relates to a transducer, particularly for vehicle steering and guidance. This relates to a small transducer used as an accelerometer for idance). eyes like this One of the known miniature transducers used in It has the shape of a tuning fork with branches and is supported inside a frame structure that acts as an inertial mass. However, this device includes a tension-sensitive filament that is There is a restriction that only acceleration along the axis cannot be detected. Furthermore, the output of the converter It is sensitive to temperature changes and therefore requires some compensation.

The present invention has two objectives. The first purpose is to measure the acceleration along two or three axes. The second purpose is to provide a transducer that can measure tension. , configured so that common-mode effects (such as temperature-dependent output fluctuations) are virtually eliminated. , so that little or no temperature compensation is required.

The invention therefore provides a central support and at least two an annular inertial mass connected to a central support by a filament; One filament elongates in response to the relative movement of the central support with respect to the amount One of the filaments contracts, and a sensor means for detecting such expansion and contraction is provided between the two filaments. A transducer integrated into the filament is provided.

The transducer may be monolithic and may be manufactured from any resilient material, such as silicone. Out When using silicon wafers etc. as the source material, to form the desired configuration. Conventional photolithography and etching techniques may be used.

It is preferred, but not essential, that the plurality of filaments have the same dimensions.

Constructed with two diametrically opposed filaments on either side of a central support The transducer of the present invention can be used as a single-axis accelerometer. two filaments Acceleration along the connecting axis of the filament elongates one filament due to the inertial mass effect. the other filament. incorporated into each of the two filaments The sensor means detects a difference indicating the magnitude of the given acceleration (+*Bnitude). Designed to give output.

The transducer of the invention comprises three or more filaments each incorporating sensor means. By placing it around the central support, the acceleration components along two orthogonal axes can be An embodiment including four filaments with zero equal spacing that may be configured to detect: This embodiment is particularly preferred because it has an excellent common-mode rejection effect inherent in this structure. This will be explained in detail below.

Especially when deploying only two filaments, the central support and inertial mass to restrict relative rotation, or relative movement between the two along an axis perpendicular to their common plane. is desirable.

In this case no sensor means shall be incorporated to couple the support to the inertial mass. One or more filamentary tie bars may be distributed around the support.

The transducer of the present invention allows the transducer to detect acceleration components along three orthogonal axes. The tension sensitive filament may include a plurality of tension sensitive filaments configured to of such a converter The configuration will be explained in more detail below.

In one embodiment of the invention, the sensor means comprises a semiconductor wire injected into the filament. may include a strain gauge. Precisely controlled amounts of impurities provide the desired property values.

Changes in tension within the filament change the resistance of the strain gauge, which is Measured by tonbridge. This type of sensor has a single-axis or multi-axis transducer structure. Can be used to create

In another embodiment, the filament is vibrated laterally. Each filament is a filament The dimensions of the filament, the tension applied to the filament, and the modulus of the material from which the filament is made. and has a natural vibration frequency as a number between density. against tension changes within the filament. A frequency change occurs accordingly. The measured value of the change in frequency is used to It is possible to measure the magnitude of acceleration caused by In this example, the filament starts vibrating and It is necessary to provide means to maintain it. For this purpose, for example, the piezoelectricity of the transducer material can be Take advantage of effects or thermomechanical properties. If silicone is selected, zinc oxide or piezoelectric layer of barium titanate or barium titanate can be sputtered onto the filament. It is. This technique is known in the field of electroacoustics.

Alternatively, thermomechanical excitation of the thermal expansion of a silicon transducer (which has a high intrinsic thermal conductivity) Can be used as a mechanism. This technology can be effectively used in conventional diaphragm turgor pressure sensors. It is used.

A thermal resistor is embedded in each filament by ion implantation, and a current is applied to each filament. The resulting periodic temperature changes pass through each resistor at the natural frequency of the filament. expands and contracts, resulting in a mechanical excitation force.

Filament vibrations are deposited on each filament and connected to a frequency measuring circuit can be detected by a piezoelectric layer. Alternatively, thermally induced expansion and contraction within the second injection resistor may induce strain in the area. When this resistor is excited with constant current, this resistor has A measurable voltage at the vibrational frequency will result.

Either piezoelectric or resistive elements can be used to excite or sense single- or multi-axis transducers. It can be used as a support means. The vibrating filament is perpendicular to the plane of the support and inertial mass. May be designed to oscillate in a straight plane or support and inertial mass flat. In the form of a tuning fork with two branches designed to vibrate in phase with each other in a plane. There may be or the transducer is designed to oscillate in the plane of the support It may be a thick and narrow filament.

A transducer with a central support and an annular inertial mass has one installation (of the central support). The landing point can be attached to the accelerating body, as opposed to the outer support and the central inertial mass. Transducers with A strain difference occurs between the filaments when the strain does not occur at another point, and this accelerates The present invention eliminates this drawback. There is.

Another advantage of the invention is that it is designed to cancel common mode effects due to, for example, ambient temperature fluctuations. The difference is that a differential converter output can be obtained.

Some embodiments of the invention will be described below based on the accompanying drawings.

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line ■--■ in FIG.

FIG. 3 is a plan view of the second embodiment.

FIG. 4 is a plan view of the third embodiment.

FIG. 5 is a sectional view taken along the line -V in FIG. 4.

Figure 6 shows thermal excitation and measurement of a suitable transducer for use with any of the above embodiments. It is a circuit diagram of a circuit.

According to Figures 1 and 2, acceleration components along two orthogonal axes (x, y) are measured. The transducer has an inertial mass of 2 by four equally spaced filaments 3, 4, 5. The supports, masses and filaments, including support 1 connected to ．． Etched from a 4+*m silicon slice, the outer diameter of the transducer is approximately 10 mm. The dimensions of the filament are typically 1 mm x 50 μm x 50 μm. of use In some cases, for example, the central support of the transducer is installed on the vehicle whose acceleration is to be monitored. For example, assuming that the subject vehicle is accelerated along the X axis, there is an inertial mass. As a result, filament 6 expands and filament 4 contracts. These changes Therefore, the natural vibration frequencies of the two filaments change, with the former increasing and the latter increasing. The amount of zero frequency deviation that decreases by the same amount as increases in is a function of the applied acceleration.

Formula this: %formula%) [In the formula, f is the vibration frequency of the filament 6 when acceleration ag is applied in the X direction. Wave number, - is the mass of inertial mass 2, fo is the vibration frequency of the filament when acceleration is 0 k is a known constant regarding the dimensions of the filament and its elasticity. Wear.

In most cases, the breaking strain is reached before a 10% change in frequency occurs. In most cases, the value of the factor km is small.

Therefore, the approximate formula: %formula%) is obtained. Regarding filament 4, filament 4 is equal to filament 6, etc. With new dimensions, a similar formula: mf, Therefore, by measuring the frequency difference f, −f, (at a given fo), a , can be measured.

The filaments 4 and 6 have different dimensions and the vibration frequencies under zero acceleration are equal. If not, this generally results in the value of ax obtained under zero acceleration conditions being zero. No, there is no need to prevent frequency fixation (frequency 1ock) In some applications, this phenomenon is acceptable and even advantageous.

one of a pair of injected thermal resistors in each of the four filaments, i.e. the excitation resistor The device RD (see Figure 1) places all four filaments in a plane perpendicular to the support surface. to force horizontal vibration. This vibration frequency is determined by the resistance of the other of the four filaments. sensor resistor R5. Appropriate excitation and acceleration along two axes can be detected and measured.

Each filament needs to be connected to a separate circuit.

A second embodiment of the present invention is shown in FIG. Laments 7.8, 9.10 have typical thicknesses of 0.41 and Manufactured from a single silicon slice with a diameter of 10 cm. filament 7 ~10 is formed into a tuning fork shape with two branches to limit the vertical movement of the inertial mass. has the same thickness as the inertial mass. The two branches of each filament are electrically driven resistors (not shown) injected into the support 1 in the plane of the support 1. It is forced to vibrate in opposite phase. Sensor resistor injected into filament is the natural vibration frequency caused by an applied acceleration along the x or y axis. Changes can be detected.

4 and 5 show the third embodiment. In this embodiment, the machining is performed along three orthogonal axes. Speed detection is possible. This embodiment has a similar structure to the first embodiment, with the center It has a support 11, an annular inertial mass 12, and four filaments p, q, r, and s. , further incorporates two additional filament cocoons and n.

The filament wires are injected and serve as the excitation resistor and sensor resistor, respectively. (not shown), and can cooperate with this resistor to measure acceleration in two directions. . filament p.

q and the resistors coupled to these filaments can measure the acceleration in the X direction.

filaments r, S and resistors (not shown) coupled to these filaments The pair may measure acceleration in the y direction.

As a variation of the above embodiment, the transducer may include a plate-shaped filament and a tuning fork-shaped filament. It may also be constituted by mixing with

It is necessary to connect each of the above embodiments to the excitation and measurement circuits by connecting the appropriate circuits. The operation of this circuit shown in FIG. 6 and connected to the embodiment of FIG. 1 will now be described.

A section showing the oscillation circuit 13 for maintaining and detecting the oscillation of the filament 4 in FIG. Referring to FIG. A current (approximately 5-^) is supplied. The excitation resistor Rn is connected to the output of the operational amplifier 15. Excitation ^Ct pressure and DC bias are supplied. Two additional operational amplifiers 16J 7 is for detecting the peak peak value of approximately 5 mV generated by the sensor resistor Rs. The signal is amplified and applied to the input of the operational amplifier 15. The two diodes 18 and 19 are The output signal appearing on pin 20 is limited to 4V.

The excitation ^C voltage (peak value 4V) supplied to the excitation resistor RD is a filament Component 4 is expanded and contracted by heat. This mechanical strain of the filament causes sensor resistor R9 inducing a resistance wire strain in the resistor and changing the resistance of this resistor sinusoidally. change. As a result of the voltage applied to the resistor swinging from Ov to +4v, each so that only one heat pulse occurs per cycle, i.e. through the sensor resistor R8. Apply a DC bias of 2cm so that the detection voltage oscillates at the same frequency as the excitation voltage. The Q value of one oscillation circuit 13 that applies the voltage is approximately 2000, and this oscillation circuit typically Operates at 60kHz. Connect the frequency of the output signal on line 20 to filament 6 acceleration in the X-axis direction by comparing it with the frequency obtained from an equal circuit The measurement value of is obtained.

At this final stage shown in FIG. 6, the signal difference fa L generated by the comparator 21 is a, is provided to a standardization device (sea 1er) 22 to provide an output 23 indicating the magnitude of be provided. Using two additional oscillator circuits connected to filaments 3 and 5 Accordingly, the acceleration in the y-axis direction can also be measured in the same manner.

The transducers shown in the embodiments of FIGS. 1 to 5 are of ±10 It has a sensitivity of about 20 Hz/g in the X-axis and y-axis directions in the 0 g operating range. Figure 5 The example has a higher sensitivity of 100 Hz/g in the Z-axis direction. which fruit In the example, for example, a well-known frequency multiplication method using a phase-locked loop is used. can improve sensitivity.

The converter of the present invention is not limited to use in conjunction with the closed loop circuit of FIG. Those skilled in the art of electronics will be able to provide alternative components to the described elements and desired results. Values can be easily selected. Additionally, both converters in this section can be combined with an open-loop circuit. It can function satisfactorily.

The transducer may be used for vehicle steering and guidance, but is not limited to this use.3 When a shaft transducer or a combination of a two-shaft transducer and a single-shaft transducer is connected to a vehicle, the Output signals relating to the acceleration of the vehicle along three intersecting directions are provided.

The above information can be combined with additional maneuver data to guide the vehicle on any chosen trajectory. The structure of the converter is simple and can be processed by the vehicle's steering and guidance computer together with the converter. The simplicity creates a robust and inexpensive steering and guidance system.

In the above description, the transducer was explained as an accelerometer, but the transducer can also be used as a pressure sensor or as an accelerometer. It will be appreciated that it can also be used as a force sensor.

Copy and translation of written amendment) Submission (Article 184-8 of the Patent Law) October 2+, 1990 Toshi Ueki, Commissioner of the Japan Patent Office, Sencho 1, Patent issue Display of application PCT/GB 89100441, title of invention Accelerometer 3. Patent applicant Address: United Kingdom, London, Nis.W.l.A.2.H. B, Whitehall (no street address) Name: United Kingdom 4. Manager, Yamada Building 5, 1-1-14 Shinjuku, Shinjuku-ku, Tokyo, amendment form. Date of submission: June 13, 1990 6. List of attached documents Accelerometer The present invention relates to a transducer, particularly for vehicle navigation and guidance. This relates to a small transducer used as an accelerometer for like this One of the known miniature transducers used for this purpose is made from silicon and has two Supported inside a frame structure that acts as an inertial mass and has the shape of a tuning fork with branches of However, this device includes a tension-sensitive filament that is There is a restriction that only acceleration along the line can be detected. Furthermore, the output of the converter It is sensitive to temperature changes and therefore requires some compensation.

The purpose of the present invention is to detect multiple tension sensing elements in phase (such as temperature-dependent output fluctuations). Configured to virtually eliminate effects, requiring little or no temperature compensation The goal is to make it happen.

The invention therefore provides a central support and at least two annular inertial mass connected to a central support by a filament; One filament caused by the relative movement of the central support to the inertial mass within elongation of one filament and corresponding contraction of the other filament, indicating the amount of said movement. Sensor means configured to provide a differential output is incorporated into the two filaments. Provided is a converter characterized in that:

The scope of the claims 1. a central support (1) and at least two fillers coplanar with the central support; an annular inertial mass (2) connected to the central support by a member (3,5). a transducer comprising: a central support (1) relative to an inertial mass (2) in a common plane; Elongation of one filament caused by relative motion and correspondence of the other filament a sensor configured to detect a contraction that occurs and provide a differential output indicative of the amount of said movement; characterized in that the sensor means (Ro, Rs) are incorporated into two filaments. converter.

2. Relative rotation between the central support and the inertial mass or along an axis perpendicular to their common plane. The central support (1) is connected to the inertial mass (2) in order to limit the relative movement between the two. Claim 1, further comprising one or more filamentary tie bars tying the Transducer as described.

3. The sensor means comprises a semiconductor strain gauge injected into the filament. The converter according to claim 1 or 2, characterized in that:

4. The sensor means includes a vibrator that starts and maintains vibration of the filament. and a detector that monitors the natural vibration frequency of the filament. The converter according to claim 1 or 2.

5. A claim characterized in that the resonator (Ro) and the detector (Rs) are thermal resistors. Converter according to claim 4.

6. Vibrate in a plane perpendicular to the common plane of the support (1) and inertial mass (2) At least two filaments are arranged in claim 4 or 5. or the converter according to 5.

7. At least two filaments are in the shape of a two-pronged tuning fork, and the support (1 ) and inertial mass (2) with branches arranged to vibrate in antiphase in a common plane. 7. A converter according to any one of claims 4 to 6.

8. At least two filaments are thick and narrow filaments and support From claim 4, characterized in that it is arranged to vibrate within the plane of (1). 7. The converter according to any one of 7.

9. Inertia in the direction perpendicular to the common plane of the central support (1) and the inertial mass (2) including means for detecting relative movement of the central support with respect to the mass; a first filament (ρ) interconnecting corresponding surfaces with the magnetic mass; a second interconnecting the corresponding opposing surfaces of the central support and the inertial mass adjacent to the center support; a filament (-), the first or second filament produced by the movement; elongation of one filament and corresponding contraction of the other filament to indicate the amount of said movement. Sensor means configured to provide a differential output between said first and second filaments. Any one of claims 1 or 3 to 7, characterized in that it is incorporated into a component. Transducer described in Section.

10. The method according to claims 1 to 9, characterized in that it is manufactured from a silicon wafer. Converter according to any one of the items.

international search report -m--＾-”””N@PCT/GB 89100441 International Search Report

Claims (1)

[Claims] 1. a central support (1) and at least two fillers coplanar with the central support; an annular inertial mass (2) connected to the central support by a member (3,5). one frame in response to the relative movement of the central support (1) with respect to the inertial mass (2). A transducer in which one filament expands and another filament contracts; Sensor means are incorporated into said two filaments (3, 5) to detect A converter characterized by: 2. Relative rotation between the central support and the inertial mass or along an axis perpendicular to their common plane. The central support (1) is connected to the inertial mass (2) in order to limit the relative movement between the two. Claim 1, further comprising one or more filamentary tie bars tying the Transducer as described. 3. the sensor means comprises a semiconductor strain gauge injected into the filament; The converter according to claim 1 or 2, characterized in that: 4. The sensor means comprises a vibrator that initiates and maintains vibration of the filament. and a detector that monitors the natural vibration frequency of the filament. The converter according to claim 1 or 2. 5. A claim characterized in that the resonator (RD) and the detector (RS) are thermal resistors. Converter according to claim 4. 6. to vibrate in a plane perpendicular to the common plane of the support (1) and the inertial mass (2). At least two filaments are arranged in claim 4 or 5. or the converter according to 5. 7. At least two filaments are in the shape of a two-pronged tuning fork, and the support (1 ) and inertial mass (2) with branches arranged to vibrate in antiphase in a common plane. 7. A converter according to any one of claims 4 to 6. 8. At least two filaments are thick and narrow filaments and support From claim 4, characterized in that it is arranged to vibrate within the plane of (1). 7. The converter according to any one of 7. 9. The support (1) and the inertial mass (2) are placed close to each other on the common surface of the opposing surfaces. contains two filaments (p, m), whose acceleration perpendicular to said plane is Stretch one filament, contract the other filament, detect the expansion and contraction, and Sensor means configured to provide a differential output indicative of the magnitude of the acceleration 8. Any one of claims 1 to 7, characterized in that it is incorporated into one filament. Converter according to item 1. 10. Claims 1 to 9, characterized in that it is manufactured from a silicon wafer. Converter according to any one of the items.