JPS6120201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic levitation control device with a simple configuration that can control the gap length between a ferromagnetic material and a DC electromagnet to be constant and stable.

FIG. 1 is a schematic configuration diagram showing a conventional magnetic levitation control device used in magnetic levitation trains and the like. In FIG. 1, reference numeral 1 denotes a DC electromagnet having an excitation coil 1b wound around 1a, and this DC electromagnet 1 is placed opposite to a ferromagnetic body 2 such as a rail. The DC electromagnet 1 is supplied with an excitation current from the power amplifier 3 and generates an attractive force against the ferromagnetic material 2, and is balanced with the ferromagnetic material 2 with a predetermined gap in balance with its own weight. There is. The length x of the gap is detected by a displacement meter 4, and compared with a predetermined value by a gap length setting device 5. Furthermore, the signals subjected to the comparison and determination are subjected to series compensation in a series compensation circuit 6. The power amplifier 3 performs feedback control of the excitation force, that is, the attraction force, of the DC electromagnet 1 based on the series-compensated control information, and maintains the length x of the gap constant.

However, since such feedback control alone has poor follow-up response to changes in the gap length x, the accelerometer 7 is used to detect acceleration information of changes in the position of the DC electromagnet 1. Then, the control information is compensated for the second derivative using this acceleration information, and the first derivative is compensated for using the velocity information obtained by integrating the acceleration information in the integrating circuit 8. In this way, the gap length x is stably controlled.

However, such a conventional device requires an accelerometer with an expensive and complicated mechanism, resulting in the disadvantage that the entire device becomes large and expensive.

Furthermore, since the accelerometer 7 must be installed in a floating part, for example, in a device configured such that the ferromagnetic body 2 floats and moves as shown in FIG. It must be installed on the side of the In that case, there was a drawback that it was very difficult to transmit the electrical signal from the accelerometer 7 to the control circuit of the fixed electromagnet 1. For this reason, it could not be used in floating type turntable devices, etc., which have been developed in recent years. Further, even when a speedometer is used in place of the accelerometer 7, a similar problem occurs.

The present invention was made in consideration of these circumstances, and its purpose is to be able to manufacture the device at low cost with a simple configuration without using expensive and large-scale equipment such as accelerometers, and to achieve levitation. An object of the present invention is to provide a magnetic levitation control device that can easily and stably control a turntable device or the like.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the same embodiment. In FIG. 2, the DC electromagnet 1, the ferromagnetic material 2, and the chain length setting device 5 are the same as those in FIG. 1 described above, and detailed explanation thereof will be omitted here. In FIG. 2, numeral 4 is a displacement meter composed of a Colpitts oscillation circuit and a negative output circuit. This displacement meter 4 is attached to the DC electromagnet 1 facing the ferromagnetic body 2, and generates a negative polarity voltage proportional to the length x of the gap between the DC electromagnet 1 and the ferromagnetic body 2. ing. The output signal of this displacement meter 4 is supplied to an operational amplifier 14 via a series circuit of a resistor 11 and a capacitor 12 and a resistor 13 in parallel. Further, the output signal of the gap length setting device 5 is supplied to the operational amplifier 14 via a resistor 15. On the other hand, the output signal of the operational amplifier 14 is supplied to the base of a transistor 25 whose collector is connected to the power supply (+Vcc). This transistor 25 has its emitter grounded via the excitation coil 1b and the resistor 16 in series, and amplifies the power of the input signal to excite the DC electromagnet 1. Further, the transistor 25
A part of the output signal is fed back to the input terminal of the operational amplifier 14 via the resistor 17.
Furthermore, a diode 18 is connected in the forward direction from the input end to the output end of the operational amplifier 14.
This diode 18 prevents the application of a negative voltage to the base of the transistor 25. Further, a capacitor 19 is inserted between the base and emitter of the transistor 25 to prevent high frequency noise from being applied to the base of the transistor 25. On the other hand, a voltage drop occurs in the resistor 16 due to the current flowing therein. This voltage drop is supplied to the operational amplifier 14 via a resistor 20 and a capacitor 21 in series. Further, the output signal of the displacement meter 4 is voltage-divided by a variable resistor 22, and this voltage-divided signal is passed through a resistor 23 to the resistor 2.
0 and the connection point of the capacitor 21.

By the way, the displacement meter 4 is constructed as follows. The collector of the NPN type transistor 41 is grounded via a tuned circuit in which a detection coil 44 is connected in parallel to a series circuit consisting of capacitors 42 and 43. The detection coil 44 is
The DC electromagnet 1 is arranged opposite to the ferromagnetic material 2.
It is attached to the ferromagnetic material 2, and its Q changes according to the distance from the ferromagnetic material 2.
Further, the base of the transistor 41 is connected to a resistor 45.
It is connected to the power supply (-Vcc) via a low resistor 46. Further, the emitter of the transistor 41 is connected to the power supply (-Vcc) via a resistor 47 and to the connection point of the capacitors 42 and 43. The Colpitts oscillation circuit constructed in this manner oscillates and outputs a sine wave having a frequency determined by the capacitances of the capacitors 42 and 43 and the inductance of the detection coil 44. Furthermore, the amplitude of the sine wave changes depending on the change in Q of the detection coil 44. That is, the amplitude level of the output signal changes depending on the gap length x between the DC electromagnet 1 and the ferromagnetic material 2. Such a sine wave is supplied to a diode 49 via a resistor 48, and the negative polarity voltage of the sine wave is detected. This negative voltage is smoothed by a smoothing circuit consisting of a resistor 50 and a capacitor 51 connected in parallel, and becomes a negative DC voltage. The level of this DC voltage is proportional to the amplitude of the sine wave. Therefore, the size of the gap length x is detected from the level of the DC voltage. This DC voltage is output as an output signal of the displacement meter 4.

In this device configured in this manner, the operational amplifier 14 compares and determines the output signal of the displacement meter 4 inputted via the resistor 13 and the output signal of the gap length setting device 5 inputted via the resistor 15. Compensated in series. The gain K ₁ of this series compensation is the resistance 1
The resistance values of 3, 15, and 17 are respectively R ₁ , R ₂ ,
When R ₃ (R ₁ =R ₂ ), it is expressed as K ₁ =R ₃ /R ₁ .
Further, the operational amplifier 14 performs first differentiation on the output signal of the displacement meter 4, which is input through a resistor 11 and a capacitor 12 in series. The transfer function G _v related to this first-order differential is the resistance value of the resistor 11, R ₄ ,
If the capacitance of the capacitor 12 is ₁ , then G _v =C ₁・R ₃・S/1+C ₁・R ₄・S (however,
S is represented by Laplace operator). Further, the excitation current of the DC electromagnet 1 is fed back to the input terminal of the operational amplifier 14 via a resistor 20 and a capacitor 21 in series. Gain K _i due to this feedback
are the resistance values of the resistors 16 and 20, respectively.
Assuming R ₅ and R ₆ , it is expressed as K _i =R ₅ ·R ₃ /R ₆ . Incidentally, the capacitor 21 is used to cut off the DC component, and its capacitance _C2 is sufficiently large. The transfer function of DC cut by this capacitor 21 is expressed as _{G i =} C ₂ ·R ₆ ·S/1+C ₂ ·R ₆ ·S. Furthermore, the variable resistor 22 and the resistor 23 are used to add the output signal of the displacement meter 4 to the feedback signal, and if the voltage dividing ratio of the variable resistor 22 is k and the resistance value is _R7 , then the gain thereof is K _H is expressed as K _H =k·R ₃ /R ₇ .

By the way, the control system of the main body of the DC electromagnet 1 is shown as follows. That is, the equation of motion of the DC electromagnet 1 is Md ² x/dt ² = M・g−F(x,i)...(1) F(x,i)=β(i/x) ² ...(2) becomes. However, M: weight of the entire floating section, g: gravitational velocity, F: attraction force of the DC electromagnet 1, β: proportionality constant, i: exciting current.

Moreover, the voltage equation in the DC electromagnet 1 is shown as follows.

e=R・i+d/dx{L(x),i}=R・i+L _p di/dt−I _p /X _p (L _p −L
_a ) dx/dt... (3) However, e: Supply voltage, R: The sum of the low resistance value of the exciting coil 1b and the resistance value _R5 of the resistor 16, L
(x): Self-inductance of exciting coil 1b,
L _p : Self-inductance of exciting coil 1b in steady state, L _a : Leakage inductance of exciting coil 1 b, X _p : Steady part of gap length x, I _p : Steady part of exciting current i.

Furthermore, if we consider minute changes,
From equations (1), (2), and (3), M・d ² /dt ²・Δx=−ΔF(x, i) ...(4) ΔF(x, i)=|∂F/∂x| _p・Δx+｜∂F/
∂i｜ _p・Δi=−2Fo/Xo・Δx+2Fo/Io・Δi…
…(5) Δe=R・Δi+L _p・d/dt・Δx −I _p /X _p (L _p −L _a )d/dt・Δx……(6
) becomes. Therefore, the control system of this embodiment device is based on the third
Shown as shown. In addition, in FIG. 3, the part surrounded by the broken line A shows the control system of the main body of the DC electromagnet 1. Further, K _p is a proportionality constant of the displacement meter 4, and K ₂ is a power amplification gain (K ₂ =1) of the transistor 25.

Next, the operation of this embodiment device will be explained. The output signal Δe _x of the displacement meter 4 is expressed as the transfer function Gv
The signal Δe _v obtained via the above output signal Δ
It is approximately 90° in phase ahead of e _x , and is a signal corresponding to velocity. Therefore, the signal Δe
By superimposing _v on the series-compensated signal, first-order differential compensation will be performed. In addition, from the block diagram shown in FIG.
The relationship with is shown by the following equation.

Δi=-(I _p・M・S ² /2F _p )・Δx + (I _p /X _p )・Δx ...(7) On the other hand, the relationship between acceleration Δα and the above minute change Δx is shown by the following formula. It can be done.

Δα=S ²・Δx ……(8) From equations (7) and (8), Δα=−2F _p /I _p・M {Δi−(I _p /X _p )・
Δx}...(9) Therefore, the gain of the conventional accelerometer 7 is
Assuming Ka, the gains K _i and K _H are set as follows.

Ki=2F _p /I _p・M・Ka K _H =1/Kp・2F _p /X _p・M・Ka=1/Kp(
I _p /X _p )K _i By setting the gains K _i and K _H in this way, the feedback signal can be made to match the output signal of the conventional accelerometer 7. Therefore, by performing the current feedback, 2
Order differential compensation will be performed. Since the excitation force of the DC electromagnet 1 is controlled according to the above-mentioned compensated control signals, the gap length x is kept constant.
Moreover, it becomes possible to hold it stably.

If each constant in the control system described above is set as follows, for example, the Bode diagram of this control system will be as shown in FIG.

Kp = 6000 [v/m], K ₁ = 10, K ₂ = 1, L _p =
0.335 [H], R = 28.3 [Ω], I _p = 0.197 [A],
X _p =0.5×10 ^-3 [m], M=1.33 [Kg], F _p =13.1
[N], K _L = 88 [V・sec/m], Ki = 1000 [V/
A], K _H = 6, T _i = 0.1 [sec], Kv = 0.2 [V・
sec/m] T _v =6×10 ^-4 [sec].

As is clear from the Bode diagram shown in Figure 4,
The phase margin θ〓 is θ〓=75°, and the gain surplus G
〓 is G〓=10dB. Furthermore, since the gain [dB] at the phase intersection point is negative, it can be seen that the control by the device of this embodiment is stable.

In this way, in this device, the output signal of the displacement meter 4 and the output signal of the gap length setter 5 are compared and determined, and the output signal of the displacement meter 4 is differentiated and fed back to this comparatively determined signal. Then, first-order differential compensation is performed, and second-order differential compensation (acceleration compensation) is performed by feeding back the excitation current of the DC electromagnet 1. Therefore, the gap length x can be controlled to be constant and stable. Furthermore, there is an advantage that the above-described simple configuration can be manufactured at low cost without using an expensive accelerometer or the like.

Note that this invention is not limited to the embodiments described above. For example, the displacement meter 4 is the DC electromagnet 1
Any device that generates a voltage of negative polarity in proportion to the length x of the gap between the magnetic material 2 and the ferromagnetic material 2 can be used. Although the series compensation is proportional compensation using an amplifier, it is also possible to perform integral compensation (compensation for reducing the steady-state deviation to zero) using an amplifier and an integrator. Further, the variable resistor 22 and the resistor 23 improve the current feedback compensation, and can be removed if the current feedback compensation alone can provide compensation sufficiently close to second-order differential compensation. Furthermore, it goes without saying that the transfer characteristics of each of the circuits may be determined as appropriate depending on the specifications of the device. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

As explained above, according to the present invention, the magnetic levitation control can be manufactured at low cost with a simple configuration without using the conventionally required accelerometer, etc., and is particularly suitable for controlling levitated turntable devices, etc. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional magnetic levitation control device, FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram for explaining the operation of the embodiment. FIG. 4 is a Bode diagram for explaining the operation of the embodiment. 1... DC electromagnet, 2... Ferromagnetic material, 3... Power amplifier, 4... Displacement meter, 5... Gap length setting device,
6...Series compensation circuit, 7...Accelerometer, 8...Integrator circuit, 11, 13, 15, 16, 17, 20,
23... Resistor, 12, 19, 21... Capacitor, 14... Operational amplifier, 25... Transistor, 18... Diode, 22... Variable resistor.

Claims (1)

[Claims] 1. An electromagnet disposed opposite to a ferromagnetic material, and a displacement meter that detects the gap length between the ferromagnetic material and the electromagnet;
A differentiation circuit that differentiates the output signal of the displacement meter to obtain a first-order differential compensation element, a current feedback circuit that obtains a signal approximating a second-order differential compensation element from changes in the excitation current of the electromagnet, and a current feedback circuit that obtains a signal that approximates the second-order differential compensation element from changes in the excitation current of the electromagnet, and the displacement meter. excitation of the magnet according to a control value obtained by adding an output signal of the differentiation circuit and an output signal of the feedback circuit to the result of the comparison and judgment; A magnetic levitation control device comprising an electromagnet drive circuit that controls current.