JP2008190943A - Absolute displacement-speed measuring sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absolute displacement-speed measuring sensor for measuring a low frequency applied to a vibration control in a building, applied to a displacement measurement when a major earthquake occurs even if the sensor is compact, and preventing a DC component from being generated in a measuring signal regardless of an installation state of the sensor. <P>SOLUTION: The absolute displacement-speed measuring sensor 10 comprises: a weight 2 built in a housing 1, and supported by a spring 3 and a damper 4; an actuator 6 actuated so as to immobilizing the weight within a measuring range; a relative speed sensor 5 for detecting a speed between the weight 2 and the housing 1; and a controller for controlling a motion of the weight. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The first application field of the present invention is a sensor for measuring vibration displacement, which is indispensable for controlling vibration caused by road surface vibration of a three-story and four-story ordinary house that has been increasing in recent years. The dominant frequency of the road surface vibration is approximately 3 Hz, but the natural frequency of the building is also approximately 3 Hz. Therefore, the building resonates and causes a large shake, thereby impairing the comfort. For active vibration control of a building, it is an indispensable requirement to feed back the absolute displacement and absolute velocity signals of the building to the controller for control. Of course, it can also be used to control the shaking of high-rise buildings and tower structures.
The second field of use is feedback control of active vibration isolation devices. There are skyhook damping and skyhook spring technologies in the vibration isolation technology. To utilize this technology, it is essential to measure the absolute speed and absolute displacement of the vibration isolation table.
The third field of use is earthquake observation. Although it is expected that the ground will shake to about 50 cm when a huge earthquake occurs, there is currently no method for measuring such ground displacement. The present invention can solve this problem.

JP 2003-130628 A

  For example, Patent Document 1 proposes an absolute velocity / displacement detection method and an absolute velocity / absolute displacement sensor using the method.

  In the prior art, seismo type acceleration sensors and speed sensors are used as building vibration control sensors. The acceleration sensor has a frequency that can be measured below a natural frequency determined by a weight housed in a casing and a spring that supports the weight, and the speed sensor has a frequency that can be measured near the natural frequency. Therefore, vibration measurement at a low frequency is possible, and it is widely used for controlling the shaking of the main tower of a high-rise building or long suspension bridge. However, in the linear quadratic optimal control theory (LQ optimal control theory) which is the most common control theory at present, the control variables to be controlled are displacement and speed. Therefore, measurement of absolute displacement and absolute velocity is indispensable for vibration control of buildings, but both cannot directly measure absolute displacement. Therefore, two stages of integrators are used in the case of an acceleration sensor, and one stage is used in the case of a speed sensor, but the integrator has a problem of drift. If the integrator contains even a small amount of DC signal, it is integrated, and drifting varies with time regardless of the signal to be measured. If there is a drift, the weight may move freely, resulting in loss of control. To solve this problem, an integrator with no drift must be constructed, which makes the sensor extremely expensive.

Since the speed sensor has only one integrator, it is relatively insensitive to drift, but it must be designed to have a low natural frequency, so the weight is large and a weak spring must be used. Miniaturization is difficult and handling is difficult.
In order to solve the problem, for example, an absolute displacement / velocity sensor as shown in Patent Document 1 has been proposed, which uses a relative displacement sensor arranged between a weight and a housing. Yes. Relative displacement is measured using a gap sensor, strain gauge, or optical signal, but it is difficult to obtain a relative displacement signal stably in a narrow space, and the sensor itself is expensive. . Another problem is the effect of the weight of the weight. When the sensor is installed, if it is attached to the installation surface with a slight tilt, the position of the weight changes due to its own weight, and thus the displacement signal is biased. Since the deviation appears as a DC signal of relative displacement, it has a bad influence on the control signal. Therefore, the DC component must be removed every time a sensor is installed.

As described above, the following 1. must be solved by the prior art. To 6. There is a problem like this.
1. 1. Construction of an absolute displacement / speed sensor that does not generate drift in a simple way. 2. Construction of absolute displacement / velocity sensor that can be measured from low frequency applicable to building vibration control. 3. Construction of an absolute displacement sensor that can be applied to both small and large earthquake displacement measurement. 4. Construction of an absolute displacement sensor that does not cause a direct current component in the measurement signal depending on the sensor installation status. 5. Construction of weight support method that can stably move sensor weight in one direction. Construction of an absolute displacement / speed sensor that meets the above requirements in a simple and inexpensive way

  The absolute displacement / velocity measuring sensor of the present invention includes a weight built in a housing and supported by a spring and a damper, an actuator that operates to immobilize the weight within the measurement range, and the weight and the housing. It consists of a relative speed sensor that detects the speed between them and a controller that controls the movement of the weight.

  In a preferred example of the absolute displacement / speed measurement sensor of the present invention, the controller includes a differentiation circuit, an integration circuit, an amplification circuit, and an addition circuit. From the relative speed measured by the speed sensor, a relative acceleration signal, a relative displacement is provided. A controller that creates a signal and an amplified signal of a relative speed, synthesizes these signals by multiplying them by an appropriate magnification, and performs feedback control so that the movement of the weight is fixed within the measurement range.

  In a preferred example of the absolute displacement / speed measurement sensor according to the present invention, the actuator and the relative speed sensor are composed of a magnetic circuit made of a permanent magnet and a moving coil so that the movement of the weight is fixed within the measurement range. It is arranged so as to be sandwiched for control.

  A preferred example of the absolute displacement / velocity measuring sensor of the present invention has a pair of springs attached only for the purpose of supporting the weight so that it can move in one direction regardless of the deviation of the weight due to gravity.

  In a preferred example of the absolute displacement / speed measurement sensor of the present invention, the vibration measurement range is expanded to a low frequency by performing negative feedback control of the relative acceleration signal and positive feedback control of the relative displacement signal. It has become.

  In a preferred example of the absolute displacement / velocity measuring sensor of the present invention, a large displacement can be measured in spite of its small size by negative feedback control of the relative acceleration signal.

In order to solve the above-described problems, the present invention includes means shown for each of the following items.
1. A relative speed sensor for detecting a relative speed signal between the casing and the weight is provided, and an acceleration signal and a displacement signal are generated by differentiating and integrating the relative speed. Furthermore, a feedback control system for driving the actuator with these three types of signals is constructed. In the feedback system, even if a drift is generated by the integrator in the circuit, there is a function to suppress it, so no drift occurs.
2. According to the positive feedback of relative displacement, there is a function to weaken the action of the spring. In addition, there is a function of actively increasing the mass of the weight by negative feedback of relative acceleration. By effectively utilizing these two types of feedback, the natural frequency is lowered, and an absolute displacement / speed sensor capable of measuring from a low frequency is constructed.
3. The function of actively increasing the mass of the weight by negative feedback of the relative acceleration reduces the natural frequency and also suppresses the relative displacement. This is a discovery that the movement of the weight is reduced even if the displacement measuring surface to which the housing is attached vibrates greatly. This discovery can be applied to small-scale and large-earthquake displacement measurements.
4). If a relative speed sensor that detects the relative speed signal between the housing and the weight is provided and the displacement signal can be measured based on that sensor, the sensor signal will always be zero when the sensor is installed. Does not occur.
5. Unless the weight is moved only in one direction, it is not possible to accurately obtain a relative velocity signal in one direction. Therefore, the weight may have a pair of springs supported from both sides.
6). According to the present invention, it is possible to construct an absolute displacement / velocity sensor that satisfies the above requirements by a simple and inexpensive method.

  The measuring range of seismo displacement sensor, which is generally considered suitable for vibration control, is that the gain and phase above the natural frequency of the sensor itself are both constant, and it is difficult to measure at low frequencies. There was a problem. In the present invention, a servomechanism is incorporated, and the state quantity of the sensor is fed back, thereby lowering the natural frequency and enabling the low frequency measurement. Since the integrating circuit and the differentiating circuit are incorporated in the feedback system, the drift problem inherent in the conventional method for obtaining the absolute displacement by integrating twice from the acceleration sensor does not occur in the absolute displacement / speed sensor of the present invention.

Mounting a sensor prototype to the vibration plane, it shows the frequency response of the ratio between the displacement u and relative displacement signal e _D of the measurement surface in FIG. In FIG. 4, all feedback control is performed by performing positive feedback for the relative displacement and relative velocity and negative feedback for the relative acceleration. When feedback is not performed, it can be read that the natural frequency is about 5 Hz (frequency at which the phase lag is 90 degrees) although strong attenuation is included. Adding a positive feedback of relative speed to this can also reduce the attenuation. The effect of the present invention is that the natural frequency is reduced from about 5 Hz to 1 Hz by performing all feedback of relative displacement, relative speed, and relative acceleration. The measurement range that can be used when positive feedback of relative velocity is performed is from 10 Hz to 100 Hz, but is expanded from 2 Hz to 80 Hz by all feedback. The gain is also reduced by about 20 dB, which indicates that a displacement measurement of 10 times the sensor stroke is possible. Of course, a lower natural frequency can be determined. In some cases, the present invention reduces the natural frequency to 0.5 Hz. In this case, the frequency that can be used as the vibration control sensor is 0.8 Hz or more. Such a sensor having frequency characteristics can be used in the first and second application fields described above.

  Next, an example of an embodiment of the present invention will be described in more detail based on an example shown in the figure. The present invention is not limited to these examples.

FIG. 5 shows a signal principle diagram of a conventional seismo type sensor. The conventional seismo sensor 30 has a structure in which an internal mass m is supported by a spring 32 and a damper 33, and detects a relative displacement (ux) due to a measurement surface displacement u and an absolute displacement x of the internal mass. The amplification gain K _a by the detector upon detection is applied, the signal is converted into an electrical signal. This signal becomes a relative displacement signal, which is differentiated by the differentiation circuit 34 to obtain a relative velocity signal.

  The natural frequency ωn and the damping ratio ζ of this sensor are expressed by Equation 1 as follows.

The measurement range of Seismo type displacement sensor is a range where both gain and phase equal to or higher than the natural frequency of the sensor itself are constant. Therefore, if the natural frequency of the sensor itself can be lowered, measurement in the low frequency region becomes possible. Here, in order to reduce the natural frequency of the sensor, as can be seen from Equation 1, it is necessary to increase the internal mass or decrease the spring constant. However, this has the disadvantage that the sensor becomes brittle, creates structural defects, and becomes larger.
Therefore, in this example, by incorporating a servo mechanism into the conventional Seismo type sensor and feeding back the state quantity of the sensor, the spring element, damping element, and mass element of the sensor are actively controlled, and they are unique without structural deterioration. Reduce the frequency and adjust the damping ratio.

The principle of the absolute displacement / speed signal sensor of this example is shown in FIG. In this sensor 10, a weight 2 having a mass m is provided in a housing 1 attached to a measurement surface. The displacement of the measurement surface is u, and the displacement of the weight is x. This weight is supported in the housing 1 by a support spring 3 having a spring constant k and a damper 4 having a damping coefficient c. In order to support it stably, it is desirable to support the weight 2 with a pair of springs and dampers. The relative speed of the weight 2 is detected by a relative speed sensor 5 including a magnetic circuit made of a permanent magnet and a moving coil 21 housed therein. The structure of the actuator 6 that actively drives the weight 2 is preferably the same as that of the speed sensor. As a result, a symmetrical structure sandwiching the weight 2 is formed, and the weight 2 can be stably moved in one direction. The relative velocity signal v (v = du / dt−dx / dt) detected by the relative velocity sensor 5 is converted into _a voltage velocity signal e _V by the amplifier Ka, and the absolute acceleration signal e _A is passed through the differentiating circuit 7. Made. Further, a relative displacement signal e _D is obtained through the integrating circuit 8. _{R A, C A, R D} , the _{C D} is a resistor and a capacitor for determining the constants _{T A = R A C A,} T D = R D C D when the differentiating circuit 7 integrating circuit 8. Within this controller, multiplied by the speed gain constant K _V to the speed signal, multiplied by an acceleration gain constant K _A to the relative acceleration signal, by multiplying the displacement gain constant, K _D, the relative displacement signal, the control signal e _C by adding them the make, drives the actuator 6 with a force coefficient K _f.

The relative acceleration is negative feedback, the transfer function of the displacement signal e _D the relative velocity and relative displacement with respect to the measurement surface displacement u when the positive feedback is expressed by Equation 2.

Further, the transfer function of the speed signal e _V is represented by Equation 3.

  When the natural frequency ωn and the damping ratio ζ are obtained from Equation 2, the following Equation 4 and Equation 5 are obtained.

FIG. 2 is a frequency response diagram showing the effect of relative displacement feedback. By performing positive feedback of relative displacement, the natural frequency is reduced. Conversely, when the negative feedback K _D of a negative natural frequency increases. The range that can be used as the absolute displacement sensor is that the gain is 0 dB, that is, u = e _D. Therefore, if e _D is measured, the absolute displacement u of the measurement surface can be measured. Since the range where the gain is 0 dB is the use range as the absolute displacement sensor, the measurement range is expanded to a low frequency by the positive feedback of the relative displacement. From another point of view, by observing the displacement of the measurement surface from the weight by creating a dynamic immovable state on the weight, observe the movement of the ground from the satellite around which the weight travels around the earth. It plays the role of GPS.

  Although the natural frequency could be reduced by negative feedback of relative acceleration, this feedback has another effect. The amplitude ratio between the displacement u of the measurement surface and the relative displacement ux when the relative acceleration feedback is applied is expressed by Equation 6.

  Since such an amplitude ratio is expressed by Equation 6, if the relative acceleration is negatively fed back, the measurable amplitude can be expanded. FIG. 3 is also a frequency response showing the effect of relative acceleration feedback. Due to the negative feedback of the relative acceleration, the natural frequency decreases and the gain also decreases. The meaning of this decrease in gain is that the denominator becomes larger as the negative feedback gain of the relative acceleration is increased, as shown in Equation 6, so that a large measurement surface displacement can be measured with a small relative displacement.

It is explanatory drawing regarding the principle of the sensor of this invention. It is explanatory drawing regarding the effect of a displacement feedback. It is explanatory drawing regarding the effect of relative acceleration feedback. It is explanatory drawing regarding the frequency response which performed all the feedback which shows the effect of this invention. It is explanatory drawing regarding a seismograph type displacement sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Weight 3 Support spring 4 Damper 5 Relative speed sensor 6 Actuator 7, 34 Differentiating circuit 8 Integration circuit 10 Absolute speed / absolute displacement sensor 21 Moving coil

Claims (6)

  A weight built in the housing and supported by a spring and a damper; an actuator that operates to immobilize the weight within a measurement range; a relative speed sensor that detects a speed between the weight and the housing; Absolute displacement / velocity sensor consisting of a controller that controls the movement of the robot.   The controller has a differentiation circuit, an integration circuit, an amplification circuit, and an addition circuit, and creates a relative acceleration signal, a relative displacement signal, and an amplification signal of the relative speed from the relative speed measured by the speed sensor, and an appropriate magnification for these signals. The absolute displacement / velocity measuring sensor according to claim 1, comprising a controller that performs feedback control so that the movement of the weight is immovable within the measurement range by combining the two.   The actuator and the relative speed sensor are composed of a magnetic circuit made of a permanent magnet and a moving coil, and are arranged so as to be sandwiched in order to control the movement of the weight so as not to move within the measurement range. Item 3. The absolute displacement / speed measurement sensor according to Item 1 or 2.   4. The spring according to claim 1, further comprising a pair of springs attached only to support the weight so that the weight can move in one direction regardless of a bias due to gravity of the weight. 5. Absolute displacement / speed sensor.   3. The absolute displacement / velocity measuring sensor according to claim 2, wherein the vibration measurement range is expanded to a low frequency by performing negative feedback control of a relative acceleration signal and positive feedback control of a relative displacement signal. .   6. The absolute displacement / velocity measuring sensor according to claim 5, wherein a large displacement can be measured with a negative feedback control of a relative acceleration signal.

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