JP2001253528A - Control method for ultrasonic floating power and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for ultrasonic floating power by direct control of an oscillator capable of carrying out speedy and precise floating control of a floating object by accelerating convergence of oascillation of the floating object by directly controlling high frequency voltage applied on the ultrasonic oscillator and controlling amplitude of the oscillator and its device. SOLUTION: A control device of ultrasonic floating power is furnished with an ultrasonic oscillator electric power source 1, an oscillator 3 having a horn 4, a solid relay 2 provided between the ultrasonic oscillator electric power source 1 and the oscillator 3, a glass disc 5 to be set on the horn 4, a CCD laser displacement sensor 6 to measure floating height of this glass disc 5, an electronic controller 8 to take in a data from this sensor 6 and a means to on-and-off-control the solid relay 2 by an output signal from the electronic controller 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling an ultrasonic levitation force, and more particularly to a method and an apparatus for controlling an ultrasonic levitation force by directly controlling a vibrator.

[0002]

2. Description of the Related Art Heretofore, if planes are arranged at a very short gap interval in parallel with the vibration surface of an ultrasonic vibrator, a repulsive force is generated between the vibration surface and the plane due to sound pressure. It has already been proposed to use the ultrasonic levitation force due to this repulsion force as a non-contact actuator.
No. 2, "floating device", Japanese Patent Application Laid-Open No. H11-40645, "Cluster tool type single-wafer processing device provided with an ultrasonic type levitating and conveying mechanism", Japanese Patent Application Laid-Open No. H10-312659, "Magnetic Disk Drive", Japanese Patent Application Laid-Open No. 7-242317 entitled "Object Conveying Device Equipped with Object Levitating Device".

[0003] Further, as a dissertation, an ultrasonic transfer system using levitation force / conveyance force [Reference (1): Hashimoto
Koike and Ueba, "Journal of the Japan Society for Precision Engineering", Vol. 63, no.
7, pp. 947-950 (1999)], Reference (2): Hashimoto / Koike / Ueba, "Measurement and Control", Vol.
38, no. 2, pp. 105-108 (1999)]
And the ultrasonic bearing used as the supporting force [Reference (3):
Isobe / Kusojin / Kojima, Journal of the Japan Society of Precision Engineering, Vol. 65, N
o. 3, pp. 438-442 (1999)].

[0004] In the future, as the use of ultrasonic power becomes more general, the demand for its accuracy is expected to be much higher than at present. For example, it is expected that stabilization and vibration control of floating objects, control of non-contact conveyance speed, non-contact positioning control, etc. will be required from the level of simply floating as in the case of electromagnetic force levitation According to the above-mentioned reference (1), as a method of controlling the ultrasonic repulsive force in the near future, a standing wave / a traveling wave is generated on a plate surface by using a plurality of transducers as a source / sink of a wave. A method of holding / positioning in the lateral direction by using this method has been proposed.

On the other hand, according to the above-mentioned reference (2), a piezoelectric element is used as a vibrator, a DC bias is applied to a high-frequency voltage for excitation, and the overall length of the piezoelectric element is changed by controlling the bias voltage. A method of controlling the repulsive force indirectly by controlling the gap interval with the gap is used.

[0006]

The above-mentioned conventional techniques are respectively useful, but in each case, the ultrasonic transducer (or the voltage for exciting the vibration) is used.
Is always in a steady state, and ultrasonic waves are generated at a constant output.

However, conventionally, in the control requiring higher accuracy, there is a possibility that the dynamics between the gap interval and the repulsive force cannot be ignored due to mutual interference between the ultrasonic sound field and the control object. Alternatively, in the case of positioning control in which the gap distance itself becomes a problem, it is necessary to control the gap distance and the repulsive force independently.

[0008] In response to such a demand, it is difficult to address these problems by a method of controlling the gap distance.

Accordingly, the present invention hastens the convergence of the vibration of a floating object by directly controlling the high-frequency voltage applied to the ultrasonic vibrator and controlling the amplitude of the vibrator, thereby achieving rapid and rapid convergence.
It is an object of the present invention to provide an ultrasonic levitation force control method and device capable of performing accurate levitation control of a levitation object.

[0010]

According to the present invention, in order to achieve the above object, there is provided a method for controlling an ultrasonic levitation force, wherein a levitation height of an object to be levitated on a vibrator having a horn is determined. By monitoring and directly controlling the vibrator, high-speed convergence of the vibration of the levitation object is performed at the steady levitation distance of the levitation object.

[2] In the method of controlling an ultrasonic levitation force according to the above [1], the power of the vibrator is turned off at a position where the levitation object exceeds a steady levitation distance, and The power supply of the vibrator is turned on at a position where the flying distance is reduced.

[3] In the control device for the ultrasonic levitation force,
An ultrasonic vibrator / power supply, a vibrator having a horn, a solid state relay provided between the ultrasonic vibrator / power supply and the vibrator, and a floating object set on the horn; A sensor for measuring the flying height of the object, an electronic controller for capturing data from the sensor, and an output signal from the electronic controller for turning on / off the solid-state relay;
Off control means.

[4] The ultrasonic levitation force control device according to [3], wherein the horn surface is circular, and the levitation object is a disk corresponding to the horn.

[5] In the ultrasonic levitation force control device according to the above [3], the sensor is a CCD laser displacement sensor.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, the levitation of the control object by the ultrasonic levitation force will be described.

As shown in FIG. 3, a floating object (floating disk) 102 having a mass m and a radius a is provided above a piston sound source 101 which makes a piston movement at a constant velocity amplitude, at a distance h sufficiently shorter than the wavelength. It is assumed that it is emerging. The fluid particles vibrate only in the upper and lower z-directions and have no radial r-component.

If the velocity potential in the gap between the piston sound source 101 and the levitating object 102 is φ, the sound field is approximated by a plane wave.

[0019]

(Equation 1)

## EQU1 ## Here, k = ω / c ₀ is the wave number (ω is the angular frequency c ₀ of the sound wave, the sound speed). At z = 0, the piston sound source has a velocity amplitude of u ₁ , and at z = h, the levitating object 102 moves up and down at a speed u _{2 of the} same frequency as the sound source.

[0021]

(Equation 2)

From the boundary condition of

[0023]

(Equation 3)

## EQU1 ## The sound pressure is obtained from the relationship of p = jρ ₀ ωφ. In particular, the sound pressure p ₁ at the lower surface z = h of the levitating object 102 is

[0025]

(Equation 4)

Here, ρ ₀ is the density of air in the levitation gap. When the gap is sufficiently smaller than the wavelength and kh≪1 is satisfied, sinkh ≒ kh, coskh ≒ 1, and the sound pressure in the gap does not depend on the position z and is almost constant.

[0027]

(Equation 5)

Is taken. When sound waves by buoyant object vibrates but is emitted in the positive z-direction, the radiation impedance at this time is z _r, from Newton's equation of motion,

[0029]

(Equation 6)

## EQU1 ## Therefore, as u ₂ ,

[0031]

(Equation 7)

Is obtained. Here, σ = m / s = m / πa ²
Is the mass per unit area of the levitating object 102.

As described above, P ₁ is represented by the vibration velocity u ₂ of the piston sound source from the two equations (4) and (7), and gives the following result.

[0034]

(Equation 8)

The following can be understood from these relational expressions. The radiation impedance is determined by the product of the medium density and the speed of sound, and does not depend on the state of the wave. Therefore, Z _r ≒ ρ ₀ c ₀
May be approximated. In addition, an object having a σ of about 1 kg / m ² or more is targeted, and the vibration frequency of the sound source is 20 k
Hz is used.

Therefore, σω = 8.18 × 10 ⁵ (kg /
m ² s) and ρ ₀ c ₀ ≒ 414 kg / m ² s (ρ ₀ =
1.2 kg / m ³ , c ₀ = 344 m / s).

[0037]

(Equation 9)

The condition (1) is also satisfied. Considering the above conditions, the above equation (8) becomes

[0039]

(Equation 10)

Is approximated. From these results, p ₁ , u ₂
It can be seen that both have frequency dependence.

When the levitating object is moving, the radiation force of Langevin is upward on the lower surface.

[0042]

[Equation 11]

On the upper surface,

[0044]

(Equation 12)

Where F = F ₁ −F ₂ is the own weight mg of the object.
(G is the gravitational acceleration)

[0046]

(Equation 13)

Is obtained. In addition, the conditional expression (9-1) described above is satisfied.
From in inducing the expression _{(13) | Z r u 2} | 2 / ρ
The term ₀ c ₀ ² is excluded. The above equation (10) is substituted into the above equation (13) to summarize h.

[0048]

[Equation 14]

Is derived. Here, it is noted that h has a finite value even if u ₁ = 0. In other words, the object is levitated even if no sound wave is emitted. However, it is considered that the levitation distance due to the presence of the second term on the right side of Expression (14) is very small and can be ignored. Therefore

[0050]

(Equation 15)

This is represented by According to other research reports

[0052]

(Equation 16)

Although there are differences in the coefficients, the dependencies of the variables are the same. The difference in the coefficients seems to be due to the fact that the basic formula for calculating the radiation power is different.

Incidentally, if the vibration speed u ₂ of the levitating object 102 is added, the above equation (10) and the above equation (1)
From 5)

[0055]

[Equation 17]

Is constant regardless of the magnitudes of u ₁ and h. It can be understood that the vibration speed u ₂ of the levitating object 102 contributes to the reciprocal of the surface density σ, that is, the heavier the object, the harder it is to vibrate.

FIG. 1 is a configuration diagram of an ultrasonic levitation control system showing an embodiment of the present invention.

In this figure, reference numeral 1 denotes an ultrasonic vibrator / power supply system (power supply section of a welder), and an ultrasonic welder SONOPET-150 manufactured by Seidensha Electronics Co., Ltd.
B, that is, composed of a vibrating part and an oscillating part, the vibrating part uses a Langevin-type bolted PZT vibrator, the oscillating part has a nominal output of 150 W, an oscillating frequency of 28.5 kHz, and an oscillating method of oscillating feedback and automatic tracking. Input is AC100V, 3.
OA was used.

The tip of the vibrator 3 has a diameter of 3
A horn 4 having a thickness of 0 mm was attached. The horn 4 has a function of amplifying the amplitude. The material manufactured by Seidensha Electronics Co., Ltd. is duralumin, the vibration surface radius is 15 mm, and the amplitude is 0 to 0.
5 μm.

The horn 4 has the same diameter and a thickness of 1.85.
A glass disk 5 which is a floating object as a floating object having a diameter of 3.2 mm and a mass of 3.23 g was placed thereon, and the glass disk 5 was raised. At this time, since a very weak restoring force is generated in the lateral direction, a complete levitation state occurs when the power supply to the vibrator 3 is started.

A control circuit is added to the levitation system. The ultrasonic vibrator / power supply system 1 includes an oscillator and a power amplifier, and a solid state relay (solid state relay) 2 is connected to a power line between the power supply output and the vibrator 3.
And a simple on / off control is performed by a command from an electronic controller (DSP and digital computer) 8 based on the height of the glass disk 5 measured by the CCD laser displacement sensor 6.

Here, the CCD laser displacement sensor 6 is
The model is a sensor head LK-030, an amplifier unit LK-2000, a reference distance of 30 mm, a measurement range of ± 5 mm, a resolution of 1 μm, and a sampling period of 512 μs. The CCD laser displacement sensor 6 is a floating type. The displacement of the flying height of the object can be measured with high accuracy.

As the digital computer in the electronic controller [DSP (Digital Signal Processor) and Digital Computer] 8, NEC Model PC9821 Ra. 300 is used to capture measured data and to enter control programs into the DSP. The DSP is manufactured by MTT, model LOR
Y Turbo DSP4400C, which realizes high-speed signal processing, is a 32-bit floating point type system.

The flying distance of the flying object is measured by the CCD laser displacement sensor 6, and the measurement data is sent to the FFT analyzer via a sensor controller, not shown, though not shown. This FFT analyzer is used to grasp the flying distance of an object.

Next, the control target will be described.

In the present invention, attention is paid to the above-mentioned object floating phenomenon using ultrasonic vibration, and electric vibration control of the floating object is performed. The greatest advantage of ultrasonic levitation is that unlike electromagnetic levitation, any object can be levitated, regardless of magnetic material. Therefore, in this embodiment, the glass disk 5 which is a non-magnetic material is levitated. When the diameter of the vibrating surface of the ultrasonic horn 4 and the diameter of the glass disk 5 were devised to be the same, complete non-contact floating was achieved. Table 1 shows the parameters of the glass disk 5.

[0067]

[Table 1]

Next, a floating control method of a floating object will be described.

When inputting a control input, measurement data is input to the DSP of the electronic controller 8 via the sensor amplifier 7,
The control voltage is output based on a program command produced in the digital computer. Output to solid state relay (AC
Solid state relay) 2 was connected. The solid state relay 2 is connected to the ultrasonic vibrator / power supply system 1 and the vibrator 3
Electric high-speed switching is realized by being sandwiched between the main bodies. In this solid state relay 2, the input side voltage is 2.
When the voltage becomes 5 to 24 V, the output side circuit is closed. Therefore, erroneous ON / OFF due to the effect of voltage overshoot
The input voltage to the solid state relay 2 was set to 3 V so as to prevent the switching off and to perform the switching on and off as fast as possible. Here, the solid state relay 2 is a JEL SYST
Made of EM CO, model A2P-202 KZ06, input side is 2.5 ~ 24V, output side is 50 ~ 25V.

FIG. 2 is a flowchart for controlling a flying object according to an embodiment of the present invention.

As shown in FIG. 3, first, the steady floating distance h of the glass disk (floating object) 5 is calculated by the equation (1) as described above.
Determined in 6). That is, h = (c ₀ / {2ω) · √
(Ρ ₀ · u ₁ / σg), a position slightly higher than the steady flying height h of the glass disk 5 is set in advance to the first control reference flying height position H ₁ (off position of the power supply of the vibrator), and steady flying. the slightly lower position the distance h is set to the electronic control unit 8 and the second control reference flying height H ₂ as a control target value (step S1).

[0072] Then, if the glass disc 5 exceeds the control reference flying height position H ₁ (step S2), and turn off the oscillator 3, the floating force is made to be inoperative in a glass disk 5 (step S3) . Then, the glass disk 5 elevated dropped, when below its control reference flying height position H ₂ (step S4), and turn on the vibrator 3, stop the fall of the glass disk 5 again to float ( Step S
5) As described above, the computer (PC982) of the electronic controller 8
The program was set in 1). Therefore, the glass disk 5
Can be converged (step S6).

Here, the control reference flying height position H ₁ is
A position slightly higher than the steady flying distance h (0.6 mm) was set, and active vibration control for high-speed on-off switching at various positions was performed.

FIG. 4 shows a time history response of the height of the glass disk when energization (= floating) is started without performing the control of the present invention. As is apparent from this figure, immediately after the power is turned on, the glass disk jumps greatly due to the impact accompanying the start of energization, and it takes about 0.8 seconds for the vibration to converge.

On the other hand, the floating of the glass disk was 0.75
FIG. 5 shows a result obtained by adding control to turn off when the distance is equal to or larger than mm and turn on when the distance is equal to or smaller than mm.

As is apparent from this figure, the large-amplitude vibration is almost converged in the first cycle, and the effect of the control is clearly shown. That is, the general vibration converges in about 0.1 second.

At this time, the control is limited to the switching to be turned on immediately after the control is once turned off, and it is considered that the shock at the time of re-input has advantageously acted on the vibration suppression.

As described above, according to the present invention, by directly controlling the vibrator, the ultrasonic levitation force is controlled, the high-frequency voltage applied to the ultrasonic vibrator is directly controlled, and the amplitude of the vibrator is reduced. By performing the control, the convergence of the vibration of the object to be levitated is accelerated, and the floating control of the object to be levitated quickly and accurately can be performed.

Further, while identifying the dynamics of the vibrator system, it is also possible to change the ultrasonic output continuously and smoothly.

With the above configuration, the gap distance and the repulsive force can be controlled independently.
Further, it is easy to identify the dynamics between the gap interval and the repulsive force, and to perform control in consideration of the dynamics.

Further, according to the present invention, non-contact vibration control and non-contact precision positioning control by ultrasonic repulsion become more practical, and they are used for non-magnetic material vibration control and micro-mechanical non-contact processing. It can be expanded to support.

The present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0083]

As described above, according to the present invention, the following effects can be obtained.

(1) By directly controlling the vibrator,
By directly controlling the high-frequency voltage applied to the ultrasonic vibrator and controlling the amplitude of the vibrator, the convergence of the vibration of a wide range of floating objects that is not limited to the material is accelerated, and the rapid and accurate Flying control can be performed.

(2) Since the convergence of the vibration of the object to be levitated can be accelerated, rapid and accurate levitation control of a wide variety of levitation objects including a magnetic substance as the object to be levitated, and consequently, control of the conveyance control thereof. The place that contributes to practical use is significant.

(3) Non-contact vibration control and non-contact precision positioning control by ultrasonic repulsion become more practical.
They can be developed for vibration control of non-magnetic material and non-contact processing / support of micro mechanism.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ultrasonic levitation control system showing an embodiment of the present invention.

FIG. 2 is a control flowchart of a floating object according to the embodiment of the present invention.

FIG. 3 is a diagram showing a basic model of ultrasonic levitation.

FIG. 4 is a diagram showing a correspondence of a floating time of a glass disk which is a conventional floating body.

FIG. 5 is a diagram showing the correspondence of the floating time of the glass disk by the ultrasonic levitation control system according to the embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 ultrasonic transducer / power supply system (oscillator and power supply amplifier) 2 solid state relay 3 transducer 4 horn 5 glass disk (floating object) 6 CCD laser displacement sensor 7 sensor amplifier 8 electronic controller (DSP mounted) 101 piston sound source 102 levitating object (floating disk)

Claims (5)

[Claims] 1. A method for controlling an ultrasonic levitation force, wherein a levitation height of a levitation object on a vibrator having a horn is monitored, and the levitation is performed at a steady levitation distance of the levitation object by direct control of the vibrator. A method for controlling an ultrasonic levitation force, wherein a high-speed convergence of a vibration of an object is performed. 2. The method of controlling an ultrasonic levitation force according to claim 1, wherein a power of said vibrator is turned off at a position where said levitation object exceeds a steady levitation distance, and a steady levitation distance of said levitation object is set. A method for controlling the ultrasonic levitation force, wherein the power of the vibrator is turned on at a position where the vibration is lowered. 3. An ultrasonic levitation force control device,
(A) an ultrasonic transducer / power supply, (b) a transducer having a horn, (c) a fixed relay provided between the ultrasonic transducer / power supply and the transducer, and (d) the horn. A floating object set above, (e) a sensor for measuring the flying height of the floating object, (f) an electronic controller for capturing data from the sensor, and (g) an electronic controller. Means for controlling on / off of the solid state relay by an output signal of the ultrasonic levitation force. 4. The ultrasonic levitation force control device according to claim 3, wherein the surface of the horn has a circular shape, and the object to be levitated is a disk corresponding to the horn. Control device. 5. An ultrasonic levitation force control device according to claim 3, wherein said sensor is a CCD laser displacement sensor.