JPH0514811B2 - - Google Patents

Description

Detailed Description of the Invention <<Industrial Application Field>> The present invention is applicable to magnetically levitated objects that are levitated and held by magnetic force, such as the rotor of a magnetic bearing type spindle of a machine tool or the conveyor levitator of a magnetically levitated transfer device. Regarding a control device.

<<Prior Art>> Conventionally, the floating position of a magnetically levitated object (hereinafter referred to as "levitating object") is controlled by feedback of a detection signal from a position sensor.

For example, in the case of a rotor with a magnetic bearing type spindle, two locations in the longitudinal direction of the rotor are kept floating by the magnetic force of electromagnets, the floating position is detected by a position sensor, and the detection signal of this position sensor is sent to a bridge circuit or other device. A processing circuit controls the excitation current of the electromagnet so that the rotor is held floating at a predetermined reference position (target position).

Further, in this control, parallel mode control and tilt mode control are separately controlled, which separately control the parallel state and tilted state of the rotor.

<<Problems to be Solved by the Invention>> However, in the conventional floating object control device described above, the floating object is kept floating at a predetermined position by feedback control, but the weight of the floating object, etc. If this changes, the robot cannot levitate to a predetermined target position, resulting in an unstable levitation condition.

For example, in the case of a machine tool rotor, when a tool such as a grindstone or cutter attached to the tip of the rotor is replaced, the rotor's center of gravity, mass, etc.
Due to changes in the moment of inertia, parallel force, and tilting force, it is not possible to maintain the levitation at the initial predetermined reference position.
Problems such as an unstable floating state and a decrease in dynamic rigidity sometimes occurred.

Further, in the case of transportation by a magnetic levitation transportation device, the weight of the transportation floating body changes due to changes in the weight of the transported object, replacement of the transportation arm, etc., and the above-mentioned problems may occur.

<<Means for Solving the Problems>> The present invention has been made to solve the above problems, and its configuration is based on the rotor of a magnetic bearing type spindle of a machine tool or the conveyance floating body of a magnetic levitation conveyance device. It consists of a magnetically levitated object that is levitated and held by an electromagnet, a position sensor that detects the floating position of the magnetically levitated object, and a control means that processes the detection signal detected by the position sensor and performs feedback control. In a control device for a magnetically levitated body, which adjusts the excitation current of the electromagnet to levitate and hold the magnetically levitated body at a predetermined position, the control means includes any one of the mass, moment of inertia, or center of gravity position of the magnetically levitated body. An input means is added for inputting the amount of change when one or more changes, and a correction circuit is provided for correcting the control conditions of the magnetically levitated body corresponding to the amount of change inputted by the input means. It is characterized by being

<<Operation>> In the present invention, when the mass, moment of inertia, and position of the center of gravity of the floating body change, this fact is input to the control means, and the floating position is controlled based on the changed values.

<<Example>> Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of the apparatus of the present invention, in which a is a spindle of a machine tool equipped with a rotor 1 as a floating body. This rotor 1
A grindstone serving as a tool is detachably provided at one end of the rotor 1, and the rotor 1 is held floating in the radial direction by front shaft electromagnets 3a, 3b and rear shaft electromagnets 4a, 4b.

The radial position of the rotor 1 is detected by front shaft position sensors 5a, 5b and rear shaft position sensors 6a, 6b provided adjacent to the front shaft and rear shaft electromagnets 3a, 3b and 4a, 4b, and their detection signals are It is sent to a control means described later.

The bearing in the axial direction of the rotor 1 is carried out by floating and holding a ring member 1' provided on the rotor 1 by the magnetic force of electromagnets 7a to 7d, and the adjustment of this levitation holding force is performed by position sensors 8a and 8b. ′
This is performed by detecting the position of , and controlling this detection signal as feedback by a control means to be described later.

Rotation of the rotor 1 is performed by an induction coil 9. That is, the induction coil 9 is configured to generate a rotating magnetic field by a driving means (not shown) and rotate the rotor 1 as a rotor at a predetermined number of rotations.

Reference numeral b denotes a control means, and its basic configuration includes a parallel mode processing system path A, an inclined mode processing system path B, and both processing system paths A, It consists of cross processing paths C, D, E, and F connected between B and B.

The parallel mode processing system path A and the tilt mode processing system path B include position processing circuits 10a and 10b that process position signals from the front shaft position sensors 5a and 5b and the rear shaft position sensors 6a and 6b, respectively, and a parallel mode control circuit. 11. A tilt mode control circuit 12 and drive circuits 13a to 13d that supply excitation current to each electromagnet 3a to 4b based on output signals from both of these control circuits 11 and 12 are provided, and each processing system path A ~F is provided with a multiplication circuit as a correction circuit, which will be described later.

c is an input means, which includes a mass setting device 30, a moment of inertia setting device 31, and a center of gravity position setting device 32.
It consists of This input means c is configured so that when the weight of the rotor 1 changes due to tool replacement or the like, a signal corresponding to the change is inputted to the above-mentioned control means b via a variable resistor.

Before explaining the operation of this embodiment, changes in the center of gravity position and inclination angle due to changes in floating weight will be explained with reference to FIG.

Now, the rotor 1 before tool conversion is the front shaft sensor 5.
The position is detected as _d1 by sensors a and 5b, while the position is detected as _d2 by rear axle sensors 6a and 6b. It is also assumed that the center of gravity position G of the rotor 1 is located at a position ₁ from the front axle side (front axle position sensors 5a, 5b) and at a position ₂ from the rear axle side (rear axle position sensors 6a, 6b). Note that the floating position of the rotor 1 in this state is controlled by the control means b to a predetermined target position, that is, parallel (d _G =0) and with an inclination angle of 0.
The excitation currents of both electromagnets 3a, 3b and 4a, 4b are controlled so that (θ'=0).

By the way, when the tool (grindstone 2) is replaced, the center of gravity position changes from G, ₁ , ₂ to G',' ₁ ,' ₂ due to the difference in weight between the tool before replacement and that tool. Due to this change, the center of gravity movement amount changes from the initial center of gravity movement amount d _G to d′ _G. These center of gravity movement amounts are illustrated by solid line and broken line vectors, and these can be expressed by the equation shown below.

d _G = ₂ / ₁ + ₂ d ₁ + ₁ / ₁ + ₂ d ₂ ...(1) d′ _G =′ ₂ /′ ₁ +′ ₂ d ₁ +′ ₁ /′ ₁ +′ ₂
d ₂ =' ₂ / ₁ + ₂ d ₁ +' ₁ / ₁ + ₂ d ₂ ...(2) Also, the inclination angle changes to θ', which is expressed by the following formula.

tanθ'= _d1 - _d2 /' ₁ +' ₂ = _d1 - _d2 / ₁ + ₂
...(3) Furthermore, according to Steiner's theorem, the moment of inertia I of the rotor 1 in the inclination direction is I=I ₀ +W _G ²
+I _T +M _T ² (W is the weight of the rotor 1, I _T is the moment of inertia of the tool, M is its weight, and _T is the distance between the center of gravity of the tool and the center of gravity G' of the rotor 1).

Therefore, when the input means c inputs the mass change amount ΔM from the mass setter 30 when changing the tool, the control signal M' corresponding to this is outputted, and the moment of inertia setter 31 outputs the control signal M' corresponding to the mass change ΔM. When the moment of inertia change ΔJ is input, a control signal J' corresponding to this is output, and when the center of gravity position after tool exchange is input from the center of gravity position setter 32, the control signal _J' corresponding to this is output. ,′ ₁ ,′ ₂
is output.

Note that by determining the above-mentioned ΔM, ΔJ, and _G in advance for each tool to be replaced, these can be easily inputted via the variable resistor at the time of tool replacement.

Among the control operations of this embodiment having the above-described configuration, changes in the center of gravity position, inclination angle, mass change, and moment of inertia change will be explained.

First, if the grindstone 2 is not replaced, it is held floating at the initial target position. That is, input means c
There is no change in each output corresponding to the output signals M', J', ' ₁ and ' ₂ output from the center of gravity position G.
(prescribed front axle distance ₁ , rear axle distance ₂ ), front axle position
d ₁ , rear shaft position d ₂ , mass M and moment of inertia J
Based on this, feedback control is performed to reach a predetermined reference position. In other words, in this case, as in the conventional case, the position signals d ₁ /( ₁ + ₂ ) and d ₂ /( ₁ + ₂ ) from both position processing circuits 10a and 10b are sent to the parallel mode processing system path A and the tilt mode processing system. cross processing circuits C and D, which include inverter circuits 14 and 15 and are connected to both processing circuits A and B by subtraction circuits 16 and 17, and a multiplication circuit as a correction circuit to be described later. Parallel mode and tilt mode are separated and controlled by cross processing system paths E and F connected to paths A and B by an adder circuit to be described later. At this time, the parallel mode control circuit 11 and the slope mode control circuit 12 provided in the parallel mode processing system path A and the slope mode processing system path B process the control signals so as to maintain them stably, thereby each Drive circuits 13a-13 for electromagnets 3a-4b
The excitation current is controlled via d.

By the way, when a tool is replaced, the mass M of the replaced tool is determined by the mass setting device 30, the moment of inertia J is determined by the moment of inertia setting device 31, and the center of gravity positions _G , ' ₁ , and ' ₂ are determined by the center of gravity position setting device. 32.

From the mass setting device 30, it corresponds to the change in mass.
The output signal M' is sent out, but since this change affects only the parallel mode control, it is processed into the parallel mode by the multiplier circuit 18, which is one of the correction circuits provided before the parallel mode control circuit 11. Multiplyed with the signal.

The moment of inertia setter 31 sends out an output signal J' corresponding to the change in the moment of inertia, but since this change affects only the tilt mode control, it is provided before the tilt mode control circuit 12. Multiplication circuit 1, which is one of the correction circuits
9, the signal is multiplied by the tilt mode signal.

The center of gravity position setter 32 indicates the change in the center of gravity position.
Output signals ′ ₁ and ′ ₂ corresponding to _G are sent out,
These are multiplication circuits 20 and 21 as correction circuits provided before and after the parallel mode control circuit 11, and multiplication circuits 2 provided in cross processing circuits E and F.
2 and 23.

Therefore, from the multiplier circuit 20, (d ₁ ′ ₂ )/
( ₁ + ₂ ), and from the multiplier circuit 22 (d ₂ ′ ₁ )/ ₁
+ ₂ ) are obtained, and these output signals are added in the adder circuit 24 provided before the parallel mode control circuit 11 to obtain the new center of gravity position G' as shown in equation (2) above. Output is made.

On the other hand, since the output of the position detection circuit 10a is inputted to the adder 16 of the slope mode processing path B via the inverter 14 of the cross processing path C, the slope angle θ' is determined by the above-mentioned The inclination angle θ' shown by equation (3) is output.

Next, control operations for parallel force and tilt force will be explained. This control operation is performed by the parallel mode control circuit 11.
This is performed by the multiplication circuit 21 in the subsequent stage and the multiplication circuit 23 provided in the cross processing path F.

That is, as shown in Fig. 2 F ₁ and F ₂ ,
F1 is installed on the front shaft position sensor 5a, 5b side of rotor _1.
A parallel force (front axis parallel force) is acting, and a parallel force F ₂ (rear axis parallel force) is acting on the rear axis position sensors 6a and 6b. Therefore, the total parallel force F ₀ is F ₀ = _F1
It can be shown as +F ₂ .

On the other hand, the tilting force of the rotor 1 is T ₀ = F ₁ when the rotor 1 _is initially not replaced with a tool.
₁ −F _{2 2} (provided that the distances from the center of gravity to the electromagnet installation position and the sensor installation position are the same). Therefore, from equation (2) above, front axis parallel force F ₁ = (T ₀ / ₁ + ₂ + ₂ / ₁ + ₂ F ₀ ) and rear axis parallel force F ₂ = ₁ / ₁ + ₂ F ₀ −T ₀ / ₁ + ₂ ) is derived, and the above F ₁ and F ₂ are derived from the adder circuits 17 and 25.
is output.

By the way, due to the tool change, the center of gravity of rotor 1 is
When the force changes to G', the above-mentioned tilting force T ₀ changes to T'. This tilting force T′ is T′=F ₁ ′ ₁ −F ₂ ′ ₂ . This equation can be transformed into T'=F ₁ ' ₁ - (F ₀ - F ₁ ) _{' 2} , from which F ₁ is derived, and F ₂ is derived in the same way. Furthermore,′ ₁ +′ ₂ = ₁ +
By substituting ₂ , the following formula is obtained.

F ₁ = T ₀ / ₁ + ₂ + _{' 2} / ₁ + ₂ F ₀ ... (4) F ₂ = ' ₁ / ₁ + ₂ F ₀ + T ₀ / ₁ + ₂ ... (5) Therefore, parallel ' ₁ of the center of gravity position output after tool change is sent to the multiplication circuit 21 after the mode control circuit 11.
By inputting ' 2 to the multiplication circuit 23 of the cross processing circuit F, the addition circuit ₁ provided in each mode control processing circuit A, B is inputted.
7 and 25, outputs of parallel force and tilt force corresponding to (4) and (5) above can be obtained. As a result, excitation current is supplied to each of the electromagnets 3a to 3b in each drive circuit 13a to 13d, and the floating position of the rotor 1 is controlled.

As described above, in this embodiment, when a tool is replaced, the mass, moment of inertia, and center of gravity position corresponding to the tool are input from the input means c, so the control means b adjusts the control conditions for the rotor 1 based on the inputs. corrected and controlled by the true mass, moment of inertia and center of gravity position of the rotor 1.

Therefore, since the rotor 1 is maintained under appropriate control conditions, a floating holding force with a stable predetermined rigidity force can be obtained.

In addition, although the above-mentioned embodiment showed an example of a rotor as a floating body, this may also be used as a conveyance floating body of a magnetic levitation conveyance device. Further, although the mass, moment of inertia, and center of gravity position of the floating object are input, it is also possible to input any one or two of these to perform simple control.

Furthermore, even in the case where the parallel and tilt modes are not separated and are controlled independently, it is of course possible to similarly correct the control conditions for the mass, moment of inertia, and position of the center of gravity of the floating body.

<<Effects>> The present invention reduces the mass of the floating object when tools etc. are replaced.
When the moment of inertia or the position of the center of gravity changes, these are input, so the control means corrects the control conditions of the floating object based on the input, and performs control based on the true mass, moment of inertia, or position of the center of gravity of the floating object. be done.

For this reason, the floating body is maintained under appropriate control conditions, so that it can have the effect of being kept floating with a stable predetermined rigidity force or floating holding force.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of the apparatus of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the positions of the centers of gravity of floating bodies. 1... Rotor (magnetic levitation body), 2... Grinding wheel (tool), 3a, 3b, 4a, 4b... Electromagnet, 5a,
5b, 6a, 6b...Position sensor, 10a, 10
b...position detection circuit, 11...parallel mode control circuit, 12...tilt mode control circuit, 13a-13
d...drive circuit, a...spindle, b...control means, c...input means.

Claims (1)

[Scope of Claims] 1. A magnetically levitated body that is levitated and held by an electromagnet, such as a rotor of a magnetic bearing type spindle of a machine tool or a conveyor levitated body of a magnetically levitated conveyance device, and a position sensor that detects the floating position of the magnetically levitated body. and a control means for processing the detection signal detected by the position sensor and performing feedback control, and the control means adjusts the excitation current of the electromagnet to levitate and hold the magnetically levitated object at a predetermined position. In the control device for a floating object, the control means is further provided with input means for inputting changes in any one or more of the mass, moment of inertia, or center of gravity of the magnetically levitating object, and A control device for a magnetically levitated body, comprising a correction circuit that corrects control conditions for the magnetically levitated body in accordance with a change inputted by the input means.