JP3470315B2 - Tilt sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt sensor, and more particularly to a tilt sensor which obtains tilt angle information in an angle range of 0 to 360 ° by a uniaxial acceleration sensor.

[0002]

2. Description of the Related Art When an attitude of an object is measured by using an acceleration sensor, usually, the input axis of the acceleration sensor is set to each of the three orthogonal axes set on the object, and the gravitational acceleration received by each acceleration sensor. The posture of the object can be accurately measured by calculating the inclination of each axis from the vertical direction based on the magnitude of the component. By the way, a small measuring device for inspecting the inside of a water pipe or a thin pipe such as a pipe of a heat exchanger, and a small measuring device for inspecting the inside of the esophagus or intestine of a human body such as a gastroscope is equipped with an inclination sensor. Then, the posture of the small measuring device may be recognized and controlled. This type of small measuring device is applied to the inside of a water pipe, the inside of a thin tube of a heat exchanger, or a small diameter such as the esophagus or intestinal tract of the human body, so the device is configured accordingly. The case is also small in diameter and has a very small internal volume. In some cases, there is no room to install the acceleration sensor on each of the three orthogonal axes described above in the case where the diameter is small and the internal volume is extremely small.

The posture of the small measuring device can be recognized by the tilt sensor in which the acceleration sensor is installed only in one axis direction, without installing the acceleration sensor corresponding to each of the three orthogonal axes in the small measuring device. Here, the acceleration sensor of the tilt sensor, the attitude angle of the sensor, and the sensor output will be described with reference to FIG. In Fig. 8 (a), a small measuring device rotates,
It is a figure which shows the inclined part, 1 is an acceleration sensor, 10 shows the small measuring device in which the acceleration sensor 1 was installed. The acceleration sensor 1 is installed in the small measuring instrument 10 with its input axis aligned with the vertical axis of the small measuring instrument 10. Here, the small measuring device 10 has 60
3 at the position where the posture is rotated and
The posture angle is shown rotated by 00 °.

FIG. 8B is a diagram showing the relationship between the rotation angle of the acceleration sensor and the sensor output. The acceleration sensor 1 outputs the maximum sensor output 1g when its input axis coincides with the gravity direction axis. In the figure, 1 g is normalized to 1 and displayed. Then, the sensor output changes in proportion to the cosine of the rotation angle measured from the gravity direction axis. Figure 8
In (b), the area surrounded by ◯ corresponds to the rotation angles of 60 ° and 300 °, and the sensor output is reduced to 1/2. The acceleration sensor 1 produces the same sensor output where the rotation angles correspond to 60 ° and 300 °. That is, the acceleration sensor 1 generates the same sensor output corresponding to the two inclination angles of 60 ° and 300 ° that the small measuring device 10 rotates. It is not possible to specify which of the two tilt angles of the small measuring device 10, namely 60 ° and 300 °, is the actual tilt angle of the small measuring device 10. The uniaxial tilt sensor in this case is
Normally, it is used only as an inclination sensor for detecting an inclination angle within 0 to 180 °.

[0005]

SUMMARY OF THE INVENTION The present invention specifies the tilt angle of a small measuring device in the tilt angle range of 0 to 360 ° even when the acceleration sensor can be housed and mounted only in one direction of the small measuring device. The present invention provides a tilt sensor that solves the above-mentioned problems.

[0006]

A tilt sensor for detecting the magnitude of gravity input to an acceleration sensor 1 to measure the tilt of an input shaft of the acceleration sensor with respect to the direction of gravity is a uniaxial acceleration sensor 1. The acceleration sensor 1 is provided around the rotation axis set perpendicularly to the input axis of the acceleration sensor 1.
A tilt sensor is provided which includes a rotary vibration applying device that rotationally vibrates, and a polarity determining device that determines the polarity in the tilt direction around the rotation axis of the acceleration sensor 1 based on a signal synchronized with the rotary vibration.

According to a second aspect of the present invention, in the inclination sensor according to the first aspect, the polarity determining device is the acceleration sensor 1
An inclination sensor having a multiplier 4 for multiplying the acceleration signal by a reference signal which is a signal synchronized with the rotational vibration of the acceleration signal output by and which represents the polarity in the rotational vibration direction. Further, in a tilt sensor according to a third aspect of the invention, the rotational vibration applying device is the acceleration sensor 1.
A vibration applying actuator 6 having a piezoelectric element 62 that causes a rotary vibration on a rotary vibration mounting plate 61 on which is mounted;
The vibration applying drive circuit 5 for driving the vibration applying actuator 6 is constituted, and the tilt sensor in which the vibration applying drive circuit 5 is connected to the multiplier 4 is configured.

Further, claim 4: claim 1 and claim 2
In the tilt sensor described in any of the above, the rotation vibration applying device is composed of a rotation operation unit 6 ′ for connecting to and operating the acceleration sensor 1 and detecting rotation of the rotation operation unit 6 ′. The inclination sensor is provided with the device 5'and applies the detection signal of the rotation detector 5'to the multiplier 4 as a signal synchronized with the rotational vibration. Further, claim 5: claim 4
In the tilt sensor described in 1), the rotation detector 5 ′ constitutes an tilt sensor that is any one selected from an encoder, a gyro, and a biaxial acceleration sensor.

Further, in the tilt sensor according to the sixth aspect, the rotation detector 5'is a mounted camera, a storage device for storing a picked-up image signal, an image moving direction successive comparison unit, and a comparison result. Based on the above, an inclination sensor composed of a rotation polarity detecting section for detecting the rotation polarity was constructed. And claim 7: In the tilt sensor according to any one of claims 5 and 6, the rotary operation part 6 ′ constitutes a tilt sensor which is a cable connected to the acceleration sensor 1 and extending.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram illustrating an embodiment of a tilt sensor, and FIG. 2 is a diagram illustrating a principle of determining an angle range of 0 to 360 ° by a uniaxial acceleration sensor. In FIG. 1, reference numeral 1 denotes one acceleration sensor included in the tilt sensor. The uniaxial acceleration signal detected by the acceleration sensor 1 is input to the amplifier 2 and amplified, and the amplified acceleration signal is supplied to the inclination amount calculator 3 and the multiplier 4. The tilt amount calculator 3 calculates the tilt amount of the acceleration sensor 1 based on the acceleration signal detected by the acceleration sensor 1. Rotational vibration within a certain rotation angle range is applied to the acceleration sensor 1 by a vibration applying actuator 6 which will be described later with reference to FIG. The AC drive signal generated by the vibration applying drive circuit 5 is applied to the vibration applying actuator 6 having a piezoelectric element, whereby the vibration applying actuator 6 is rotationally vibrated within a certain rotation angle range. The acceleration sensor 1 is a vibration applying actuator 6
The rotary vibration generated by the vibration applying actuator 6 is transmitted to the acceleration sensor 1 by being mounted and coupled to the rotary mounting plate. As a result, the acceleration sensor 1 is rotationally vibrated within a certain angular range in the rotational vibration cycle generated by the vibration applying actuator 6. The AC drive signal generated by the vibration applying drive circuit 5 is also supplied to the multiplier 4. The multiplier 4 is the amplifier 2
The amplified acceleration signal input from the AC drive signal is multiplied by the AC drive signal input from the vibration applying drive circuit 5, and the multiplication result is input to the polarity determiner 7. The polarity determiner 7 receives the multiplication result of the multiplier 4 and averages it to determine the polarity of the inclination angle of the acceleration sensor 1. Reference numeral 8 is a tilt angle indicator. The tilt angle indicator 8 has the tilt amount calculated by the tilt amount calculator 3,
And the polarity determined by the polarity determiner 7 is displayed.

The application of rotational vibration to the acceleration sensor 1 will be described with reference to FIG. FIG. 3A is a diagram conceptually explaining the capacitance type acceleration sensor 1 by exaggerating the electrode spacing. The acceleration sensor 1 includes an upper electrode 11, a lower electrode 12, and a central electrode 13 forming a pendulum. The central electrode 13 is coupled to the supporting portion 132 via the hinge 131. In this acceleration sensor 1, the lower surface of the left side of the upper electrode 11 is electrically insulated and joined to the upper surface of the support portion 132, and the upper surface of the left side of the lower electrode 12 is electrically insulated and joined to the lower surface of the support portion 132. It is done and joined in one. In this case, the central electrode 13, the upper electrode 11 and the lower electrode 1
A gap is naturally formed between the two. Referring to FIG. 3B, FIG. 3B is a diagram for explaining the capacitance-voltage conversion of the acceleration sensor 1 corresponding to the displacement of the central electrode 13 due to the application of acceleration. The oscillation output of the oscillator 50 is applied between the center electrode 13 and the upper electrode 11 and the lower electrode 12, and the rectified output corresponding to the displacement of the center electrode 13 is taken out via the amplifier 51 and the diode 52, respectively.
Both of these outputs are applied to the inverting input and the non-inverting input of the operational amplifier 53, and the DC voltage output corresponding to the displacement of the central electrode 13 is added and output.

Referring to FIG. 4, this is a diagram for explaining the mounting of the acceleration sensor 1 shown in FIG. 3 on the vibration applying actuator. FIG. 4A is a view of the acceleration sensor 1 attached to the vibration applying actuator as viewed from above, and FIG. 4B is a view of the long side of FIG. 4A as viewed from the side. 4 (c) is a side view of the short side of FIG. 4 (a), FIG. 4 (d) is a diagram for explaining the rotary vibration attachment plate, and FIG. 4 (e) is a rotation of the vibration applying actuator. It is a figure explaining a vibration.

Referring to FIG. 4 (d), the rotary vibration mounting plate 61 has a notch 610 communicating with the outer side extending from the short side of one corner to the other corner along both opposing short sides. To form. As a result, the fixed portion 611 is formed on the short side of the rotary vibration attachment plate 61, and the hinge portion 612 is formed on the long side of the fixed portion 611. A free end portion 613 is formed on the other long side facing each other so as to correspond to the hinge portion 612. The capacitance type acceleration sensor 1 is bonded and fixed to the central portion of the rotary vibration mounting plate 61. The piezoelectric element 62 also made of an elongated piece is joined and fixed to the diaphragm 63 made of an elongated piece to form the diaphragm 63 that operates similarly to a bimetal. The piezoelectric element 62, to which the piezoelectric element 62 is bonded and fixed, expands and contracts in the longitudinal direction of the piezoelectric element 62 when a voltage is applied to the piezoelectric element 62. Here, when one end portion of the vibrating plate 63 is fixed, the piezoelectric element 62 expands and contracts in the length direction, and the other end portion of the vibrating plate 63 rotationally vibrates as a fixed end fulcrum. The vibrating plate 63 has one end fixed to the vicinity of the hinge 612 in the fixed portion 611 via the support column 64. The other end of the diaphragm 63 is joined and fixed to the free end 613 facing the hinge 612 via the support column 64.

Referring to FIG. 4 (e), when an oscillating voltage is applied to the piezoelectric element 62, the vibrating plate 63 operates as a bimetal, and the free end portion 613 of the rotary vibrating mounting plate 61 has the support 6
The other end of the vibrating plate 63 is rotationally oscillated via the motor 4. The acceleration sensor 1 installed in the small measuring device 10 produces an average output proportional to the cosine of the tilt angle of 1 g. Since the acceleration sensor 1 is attached to the vibration applying actuator 6 and rotationally vibrates in the rotational inclination direction of the acceleration sensor 1, the inclination angle of the acceleration sensor 1 itself rotationally vibrates. Referring to FIG. 2, the acceleration sensor 1
The output change for a short time fluctuates slightly as indicated by the arrows of increase and decrease. This fluctuation is caused by, for example, the inclination angle 6 in the circle.
In the vicinity of 0 °, the output when the acceleration sensor 1 rotates clockwise due to rotational vibration slightly decreases from the average value, and when it rotates counterclockwise, the output slightly increases from the average value. On the contrary, in the vicinity of the inclination angle of 300 ° in the circle, the output when the acceleration sensor 1 rotates clockwise due to rotational vibration slightly increases from the average value, and when it rotates counterclockwise, It slightly decreases from the average value.

Therefore, by using the multiplier 4, the acceleration signal detected by the acceleration sensor 1 and input through the amplifier 2 is switched, that is, synchronized, by the polarity of the drive signal supplied from the vibration applying drive circuit 5. Detection is performed and the result is input to the polarity determiner 7 and averaged. Referring to FIG.
By this averaging, a DC signal for polarity determination, which becomes a negative acceleration signal at an inclination angle of 60 °, is obtained.
At °, a DC signal for polarity determination, which is a positive acceleration signal, is obtained. Hereinafter, the polarity determination by this synchronous detection is shown in FIG.
Will be described with reference to.

FIG. 5 is a diagram for explaining the operation in the vicinity of an inclination angle of 300 °. In this case, the output of the acceleration sensor forming the synchronous detection and the signal indicating the polarity also become the polarity of the inclination of the acceleration sensor obtained by the polarity of the DC signal obtained by multiplication and averaging. In the vicinity of the inclination angle of 300 °, the inclination polarity of the acceleration sensor is positive. Synchronous detection can also be processed digitally. That is, in the case of digital processing, the polarity can be determined by sampling the output of the acceleration sensor at a timing synchronized with the applied rotational vibration, holding the sampled data alternately, and comparing the magnitudes directly. .

Regarding the magnitude of the inclination, the acceleration sensor 1
Output θ can be obtained in the range of 0 <θ <180 ° by θ = cos ⁻¹ (output). However, 180 ° <θ <360
Since the same output is obtained even in the range of °, both ranges are displayed on the display unit and either is selected by the polarity determination signal. Thereby, only one acceleration sensor 1 can be used to display the tilt angle in the angle range of 360 ° or in the angle range of −180 ° to + 180 °.

In FIG. 1, an inclination sensor can be constructed by using independent individual circuits and display tables as the inclination amount calculator 3, the multiplier 4, the polarity determiner 7, and the inclination angle indicator 8. However, all the signals supplied from the amplifier 2 and the vibration applying drive circuit 5 can be read into the arithmetic processing unit CPU and processed by software. In FIG. 1, the vibration applying actuator 6 is used to apply rotational vibration to the acceleration sensor 1. However, a small measuring device 10 for inspecting the inside of a thin tube generally has an integrated cable fed from the outside of the thin tube. ing. in this case,
The rotation of the cable that occurs when the small measuring device 10 is operated via the cable is synchronized with the rotation of the small measuring device 10 including the acceleration sensor 1. In this case, the rotation of the cable when the small measuring device 10 is operated via the cable is substituted for the rotation by the vibration applying actuator 6 without using the vibration applying actuator 6 for the rotational vibration of the acceleration sensor 1. This will be described with reference to FIG. 6. Since the place where the small measuring device 10 is operated is not usually limited in size so that there is no room for positioning and installing various devices, a rotary encoder, a gyro, An axial acceleration sensor and other devices for detecting the rotation polarity are installed as the rotation detection unit 5'regardless of their shape and dimensions. Then, the operation of the small measuring device 10 performed via the cable is treated as the rotation operation unit 6 ′, and the rotation by this rotation operation unit 6 ′ is detected by the rotation detection unit 5 ′.
And the detection result is read into the arithmetic processing unit CPU and processed by software, the same operation and effect as when the vibration applying actuator 6 is used can be obtained. The rotation vibration by the rotation operation unit 6'is irregular and discontinuous, but it can be sufficiently used as a signal indicating the polarity.

Referring to FIG. 7, when the small measuring device 10 is equipped with a camera such as a gastric camera, this mounted camera is used as a device for detecting the rotation polarity of the rotation detecting section 5 '. That is, the rotation is detected by processing the captured image signal corresponding to the rotation of the camera by the rotation operation unit 6 ′. The image signal at a certain moment output from the on-board camera is stored in the storage device, which direction the image is rotated is compared with the image at the next moment, and the rotation polarity signal can be obtained from the comparison result. .

[0020]

As described above, according to the present invention, the uniaxial acceleration sensor is mechanically modulated in the rotational direction, and the obtained tilt measurement data is synchronously detected with the polarity in the rotational direction. In general, it is possible to obtain tilt angle information in an angular range that cannot be obtained only with a single-axis speed sensor. That is, even if only one acceleration sensor can be accommodated and attached due to the limited shape and size, it is possible to obtain the tilt angle information in the angle range of 0 to 360 °.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example.

FIG. 2 is a diagram showing a rotation angle-sensor output characteristic of an acceleration sensor.

FIG. 3 is a diagram illustrating a capacitance type acceleration sensor.

FIG. 4 is a diagram illustrating a vibration applying actuator.

FIG. 5 is a diagram for explaining polarity determination by synchronous detection.

FIG. 6 is a diagram illustrating another embodiment.

FIG. 7 is a diagram illustrating still another embodiment.

FIG. 8 is a diagram illustrating a conventional example.

[Explanation of symbols]

1 Accelerometer 4 multiplier 5 Vibration application drive circuit 6 Vibration application actuator 61 Rotational vibration mounting plate 62 Piezoelectric element

Claims (7)

(57) [Claims] 1. An inclination sensor that detects the magnitude of gravity input to an acceleration sensor to measure the inclination of an input axis of the acceleration sensor with respect to the direction of gravity. The inclination sensor includes a uniaxial acceleration sensor, and the input axis of the acceleration sensor is A polarity determination device that includes a rotational vibration applying device that rotationally vibrates the acceleration sensor around a rotation axis that is set vertically, and that determines the polarity of the acceleration sensor around the rotation axis in the tilt direction based on a signal synchronized with the rotational vibration. An inclination sensor, comprising: 2. The tilt sensor according to claim 1, wherein the polarity determination device accelerates a reference signal that is a signal synchronized with the rotational vibration of the acceleration signal output from the acceleration sensor and that represents the polarity in the rotational vibration direction. A tilt sensor having a multiplier for multiplying a signal. 3. The tilt sensor according to claim 2, wherein the rotary vibration applying device includes a vibration applying actuator having a piezoelectric element that causes rotary vibration on a rotary vibration mounting plate on which an acceleration sensor is mounted, and a vibration applying actuator. And a vibration applying drive circuit for driving the vibration applying drive circuit, wherein the vibration applying drive circuit is connected to a multiplier. 4. The tilt sensor according to any one of claims 1 and 2, wherein the rotary vibration applying device is composed of a rotary operation unit which is connected to an acceleration sensor and operates the acceleration sensor. An inclination sensor comprising a rotation detector for detecting rotation vibration, and applying a detection signal of the rotation detector to the multiplier as a signal synchronized with the rotation vibration. 5. The tilt sensor according to claim 4, wherein the rotation detector is any one selected from an encoder, a gyro, and a biaxial acceleration sensor. 6. The tilt sensor according to claim 4, wherein the rotation detector includes an on-board camera, a storage device for storing a picked-up image signal, an image movement direction successive comparison unit, and a rotation polarity based on the comparison result. An inclination sensor comprising a rotation polarity detection unit for detecting. 7. The tilt sensor according to claim 5, wherein the rotary operation part is a cable which is connected to the acceleration sensor and extends.