JPH04203525A - Control for electromagnetic bearing type rotor - Google Patents

Abstract

PURPOSE:To simplify the tuning of a control system by setting the phase delaying region of an electromagnetic bearing control circuit in the vicinity of the characteristic frequency of the measurement-disabled mode of a rotor and assembling the characteristic vibration mode having the lower characteristic frequency than that in the observation-disabled mode into an observer, having the mode as numerical value model. CONSTITUTION:A controlled system 7 inputs a dispacement signal (y) and a control force (u) into an observer 8, where the speed signal which is necessary for the state feedback and can not be observed is calculated by a numerical model assembled in the observer 8. The control force (u) is allowed to act on a rotor by the calculation to the above-described state quantity by a feedback gain calculator 9, and the rotor is held at a neutral position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic bearing type rotary control system that controls the oscillation of bending vibration of a rotor supported by an electromagnetic bearing.

[Conventional technology]

An example of a rotor 1 supported by electromagnetic bearings is shown in FIG. The left bearing 2 is a ball bearing, and the right bearing 3 is an electromagnetic bearing controlled by electromagnetic force. The control system of such an electromagnetic bearing type rotor will be explained with reference to FIG. The electromagnetic bearing is composed of magnetic poles in the X direction and in the
The transfer function of a controller that controls an electromagnetic bearing is calculated by a control circuit 5 such as the following, a control current is sent to the electromagnet 3 by a power amplifier 6, and the electromagnetic force is used to hold the rotor 1 at the center of the bearing. , as shown in Figure 4, the gain increases at intermediate frequencies, and as the frequency increases, the gain decreases, and
The phase is delayed. For this reason, the natural frequency Ω becomes unstable in a stationary floating state, which may result in an oscillation phenomenon in the bending mode of the rotor shaft 1- when supported by an electromagnetic bearing. This is the case shown in FIG. 4 where the gain and phase are small, and at the frequency of the natural frequency Ω, the gain is high but the phase is delayed, so oscillation occurs. When the gain and phase are medium, oscillation does not occur because the phase is leading at the natural frequency Ω, but the natural frequency Ω. In this case, the phase is delayed and oscillation occurs. Further, when the gain and phase are large, the phase leads at the natural frequency Ω4 and there is no oscillation, but at the natural frequency Ω4 above that, the phase lags and oscillates.

As mentioned above, in general, the natural frequency Ω1 of the rotation range of the rotor. Regarding Ω2, although it is stably controlled by the controller, the natural frequency Ω of the bending motor with a frequency higher than the rated rotation speed oscillates, making stable levitation impossible, and due to the oscillation of this mode, the natural frequency Several Ω0. The damping ratio at Ω2 cannot be set high, making tuning difficult.

In order to suppress the oscillation of this bending mode, the literature Matsu
Shita, 0. ．． et all"Rotor Vib
rationSimulation Method
forActive Magnetic Bearin
g Control, “2nd International
nal Symposium on Magnetic
Bearing July 12-14.1990.
Tokyo.

Japan.

In this case, a notch filter whose frequency is matched to the natural frequency Ω3 is provided.

[Problem to be solved by the invention]

However, the conventional technology lacks consideration of the vibration characteristics of the rotor. In other words, the natural frequency of the rotor changes as it rotates due to the rotor's rotation effect (gyro effect).
Even if a notch filter is provided whose frequency matches the natural frequency of the rotor when it is stopped, the frequency will deviate when the rotor is rotating, and the natural frequency will oscillate, so that no effect can be expected. , f.

In order to realize a notch filter with high damping effect, fine adjustment of circuit elements is essential, and tuning of the controller requires a great deal of effort.

Preventing higher-order mode oscillation by creating a phase inversion region near the natural frequency of the pin support of the shaft system is possible if the natural vibrations of the shaft system are sufficiently far apart, but the bending mode of the shaft This may be difficult to achieve when the natural frequencies of are close to each other.

The purpose of the present invention is to effectively enhance the spring stiffness and damping characteristics of an electromagnetic bearing by suppressing the oscillation of higher-order bending modes of the rotor and increasing the feedback gain of the control system.
An object of the present invention is to provide an electromagnetic bearing control method that can obtain stable high-speed rotation with low vibration.

[Means to solve the problem]

In order to achieve the above object, the present invention sets a phase delay region of the electromagnetic bearing control circuit near the natural frequency of the unobservable mode of the rotor. In addition, the controller is constructed by incorporating a natural vibration mode lower than the natural frequency of the unobservable mode into the observer as a numerical model.

[Effect]

According to the above configuration, it is possible to prevent the oscillation of higher-order mode bending vibration that exceeds the rotor's rated rotation speed, which allows the gain of the control circuit to be set high, achieving stable high-speed rotation, and simplifying the tuning of the control system. can be converted into

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. Fifth
The figure shows the natural vibration mode of the rotor shaft system.

Ω1 is a rigid body mode in which the shaft vibrates linearly without bending deformation, and Ω2 to Ω indicate bending modes of the shaft.

Comparing the displacement at the position of the electromagnetic bearing 3 in each mode, the displacement in the Ω mode is almost zero. In the case of electromagnetic bearings, the displacement sensor is installed near the bearing, so when the rotor vibrates, the Ω, ~Ω, and Ω6 modes can be detected, but even if the Ω mode can be detected, its value is extremely small. becomes. Therefore, it can be said that it is a difficult mode to observe. In other words, even if this mode of vibration occurs in the shaft system, the output of the displacement sensor will be small, so the force generated from the electromagnet will also be small, and even if the phase of the control circuit's transfer function is in the frequency domain of this mode. Even if the phase is delayed, the Ω mode will not be excited.

In this way, it is shown that the natural vibration mode includes a mode in which oscillation is easy and a mode in which oscillation is difficult.

FIG. 6 shows a state feedback type control loop using an observer. Controlled object 7 is displacement signal y
and the control force U are input to the observer 8, and the observer 8
Now, a speed signal that is necessary for state feedback and cannot be observed is calculated using a numerical model that is incorporated into the observer 8. The fee 1 is calculated by the pack gain calculator 9 on such state quantity, and the control force U is applied to the rotor to maintain the rotor at the neutral position.

Figure 7 shows the mathematical model of observer 8 and (2) the Ω of Figure 5.
It is a Bode diagram of the controller when □ and Ω2 are considered. Once the gain characteristics become high and the frequency becomes high,
The seven-phase characteristic with decreasing gain has a phase lead up to around 100 Hz, but a phase lag in the high frequency range.

FIG. 8 shows the gain characteristics of the open loop transfer function of the control system when the Bode diagram of the controller shown in FIG. 7 is applied. Ω,
There is a phase lead at the natural frequency of Ω2, but Ω,
At the natural frequency of , the phase delay is jx and the gain is OdB.
This shows that oscillation occurs. Also, Ω.

It is shown that oscillation occurs as if Ω.

Figure 9 shows the mathematical model to be incorporated into the observer.Ω1~
Ω, are taken into consideration. Under this condition, Ω1~
It can be seen that Ω1 becomes stable, but Ω becomes unstable.

This shows that the natural vibration mote, which was not taken into account by the observer, becomes unstable.

Figure 1 shows the i'i'T observation mode 1-Ω shown in Figure 5.
Ω1 to Ω in front of. This is the case when considering the mathematical model of the mode. The mode 1- of Ω, ~Ω, is naturally one phase advanced and stable, and the mode Ω, which is phase delayed, has a sufficiently low gain and does not oscillate.

〔Effect of the invention〕

According to the present invention, since the higher-order bending natural vibration mode does not oscillate, it is possible to increase the feedback gain of the control system, and it is possible to provide an electromagnetic bearing with high rigidity and high damping. Furthermore, the number of natural vibration modes to be incorporated into the observer has been determined.

In addition, since the stability of higher-order modes is ensured, tuning of the control system is simplified, resulting in an easy-to-use electromagnetic bearing controller.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a one-loop transfer function showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of an electromagnetic bearing rotor, Fig. 3 is a system diagram of an electromagnetic bearing control loop, and Fig. 4 is a diagram of rotor vibration. Characteristics and Controller 1 - Characteristic diagram of the roller. Figure 5 is an explanatory diagram of the vibration mode of the rotor shaft. Figure 6 is a block diagram of the observer type feedback control loop. Figure 7 is the controller when considering two vibration modes. 8 is an explanatory diagram of the open-loop transfer function in FIG. 7, and FIG. 9 is an explanatory diagram of the open-loop transfer function when three vibration modes are considered. 2... ball bearing, 3... electromagnetic bearing, 4...
Basic sensor, 5... Controller, 6... Power amplifier, 7... Controlled object, 8... Observer, 9...
Feedpa 1st Qin 2'l-3rd mouth 5th mouth 6th Miryo 7's

Claims (1)

[Claims] 1. In an electromagnetic bearing control system for a rotor supported by an electromagnetic bearing, control of an electromagnetic bearing type rotor is characterized in that the phase inversion region of the control circuit is made to coincide with the vicinity of the natural vibration of an unobservable mode of the rotor shaft system. method.