JPH03231316A - Magnetic bearing controller - Google Patents

Abstract

PURPOSE:To improve the positioning accuracy of an axis by performing the switch between the output of a pseudo error signal generator and a position error signal consisting of the difference between a position command signal and the signal of a position sensor in accordance with the position of the axis. CONSTITUTION:A window comparator 8 outputs a signal to decide whether the output V of a position densor 4a is kept in a range of Vn<V<Vf or not. A pseudo error signal generator 10 receives the outputs A of the sensor 4a and the output B of the comparator 8 to produce two types of signals and outputs one of these two signals. If an axis 15 of a magnetic bearing is positioned out of a range of measurement to the position sensors 21 and 22, a changeover switch 9 conducts in a b-c section and is turned on at the side of the generator 10. A pseudo signal is produced when the position of the axis 15 is larger than a target position. Then the axis 15 moves in the direction where X is reduced. Meanwhile a position error signal consisting of the difference between a position error signal and a position command signal is outputted when the position of the axis 15 is smaller than the target position. Then the axis 15 moves in the direction where X is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for a five-degree-of-freedom control type magnetic bearing.

BACKGROUND OF THE INVENTION In recent years, machine tool main spindles that use five-degree-of-freedom controlled magnetic bearings to rotate at high speeds of RPM or higher have been put into practical use. The five-degree-of-freedom control type magnetic bearing used for these main shafts is composed of two radial magnetic bearings and one thrust magnetic bearing. As shown in FIG. 7, a radial magnetic bearing generally includes two sets of electromagnets 2a, 2b for the X-axis circumference and the Y-axis on an XY plane perpendicular to the axis of the main shaft 1.
3a.

3b, an X-axis position sensor, and a Y-axis position sensor 4C. Each of these position sensors 4a, 4b.

4C detects the displacement of the main shaft in the X-axis direction and Y-axis direction, amplifies the deviation from a constant position command signal, performs signal processing, and then amplifies the power to control the electromagnets of the X-axis circumferential and Y-axis electromagnets. It is designed to control power. The thrust magnetic bearing has two electromagnets 2c around the Z-axis, assuming that the axis of the main shaft is the Z-axis.

3c and a Z-axis position sensor. The position sensor detects the displacement of the main shaft in the Z-axis direction, amplifies the deviation from a fixed position command signal, processes the signal, and then amplifies the power to control the electromagnetic force of the Z-axis electromagnet. There is.

Problems to be Solved by the Invention In the five-degree-of-freedom control type magnetic bearing as described above, the positioning accuracy of the main shaft depends on the accuracy and resolution of the position detection sensor. This problem is important for machine tool spindles that require high machining accuracy, and high-precision and high-resolution sensors are required to perform high-precision positioning. Position detection sensors for magnetic bearings require a sensor with a wide measurement range that covers the range of motion of the shaft, but sensors with a wide measurement range generally have low resolution, making it difficult to perform highly accurate positioning. I had an issue.

Therefore, the present invention provides a magnetic bearing control device for solving the above-mentioned evacuation problem.

Means for Solving the Problem In a control device for a magnetic bearing, two types of pseudo position error signals are generated, and a determination is made as to whether the shaft position is closer or farther than the target position relative to the position detection sensor. A pseudo error signal generator is provided to output one of the signals, and when the shaft position is outside the measurement range of the position detection sensor, the output of the pseudo error signal generator is used as a position error signal, and the shaft position is measured by the position detection sensor. When within the range, positioning is performed within the measurement range of the position detection sensor by using the difference between the position command signal and the signal of the position detection sensor as a position error signal.

According to the present invention, when the shaft position is outside the measurement range of the position detection sensor, the pseudo error signal generator determines whether the shaft position is closer or farther than the target position with respect to the position detection sensor. Either one of two types of pseudo error signals is output. Since the shaft position is outside the measurement range of the position detection sensor, the output of this pseudo error signal generator becomes a position error signal, and the shaft moves in the direction of the target position. If the shaft position is within the measurement range of the position detection sensor, the position error signal is switched to the difference between the position command signal and the sensor signal, so that normal position control is performed. Therefore, there is no need for a position detection sensor with a wide measurement range that covers the entire range of motion of the bearing, and a high-resolution sensor with the minimum necessary measurement range can be used.

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

FIG. M1 shows a control device for a five-degree-of-freedom control type magnetic bearing in an embodiment of the present invention. 1 is the main axis, 2a.

2b, 3a, 3b are electromagnets for radial magnetic bearings, 2c,
3c is an electromagnet for thrust magnetic bearing; 4a;

4b and 4c are position sensors, 5 is a power amplifier circuit, 6 is a signal processing circuit, 7 is a comparator, and 8 is a window comparator, which detects whether the output V of the position detection sensor is in the range of V<V. Outputs a signal for discrimination. 9 is a changeover switch, and the output from window comparator 8 allows a-C to be changed.
Either the terminal or b and c becomes conductive. Reference numeral 10 denotes a pseudo error signal generator, which has a configuration as shown in FIG. A is the output of the position detection sensor, and B is the output of the window comparator 8. In the pseudo error signal generator, CR
Two types of signals as shown in FIGS. 3 and 4 are generated by charging and discharging the circuit, and one of the signals is output by discriminating the output value of the position sensor using 11 comparators. FIG. 5 is a diagram showing the positional relationship between the position detection sensors 21, 22 and the shaft 15, and FIG. 6 is a graph showing the relationship between the output of the position detection sensor and the shaft position. When the axis position is outside the measurement range of the position detection sensor and is further away from the position detection sensor than the target position (X>Xf), the changeover switch 9 conducts between b and c, making it similar to The error signal generator side is turned on. In the pseudo error signal generator, the changeover switches 12 and 13 conduct between e and f and h and i, respectively, to generate signals as shown in FIGS. 3 and 4. Since the changeover switch 14 conducts between j and 3, a pseudo error signal as shown in Fig. 3 is output, and the axis moves in the direction where X is small.On the other hand, when the axis position is closer to the target position (X
<Xn), the terminals -e of the 14 changeover switches become conductive, so a pseudo error signal as shown in FIG. 4 is output, and the axis moves in the direction in which X becomes larger. When the shaft moves and enters the measurement range of the sensor (X <

Effects of the Invention According to the present invention, the position error signal created by taking the difference between the output of the pseudo error signal generator, the position command signal, and the position signal detected by the sensor is switched according to the shaft position. It is possible to use a high-accuracy, high-resolution sensor with a limited measurement range. As a result, the positioning accuracy of the shaft can be improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a control device for a 5-degree-of-freedom control type magnetic bearing in an embodiment of the present invention, Fig. 2 is a block diagram of a pseudo error signal generator, and Figs. 3 and 4 are pseudo error signal characteristic diagrams. , Fig. 5 is a diagram showing the positional relationship between the position detection sensor and the shaft, Fig. 6 is a diagram showing the relationship between the output of the position detection sensor and the shaft position, and Fig. 7 is the control of the conventional 5 degrees of freedom control type magnetic bearing. It is a block diagram of a device. 1...Main shaft, 2a, 2b, 3a, 3b...
...Radial magnetic bearing electromagnet, 2c, 3c...
・・Illustrated electromagnet for magnetic bearings, 4a, 4b, 4c・・
...Position sensor, 5...Power amplification circuit, 6
... Signal processing circuit, 7 ... Comparator, 8
...Window comparator, 9.12.13
．． 14... Changeover switch, 10...
- Pseudo error signal generator, 11... Comparator.

Claims (1)

[Claims] In a control device for a 5-degree-of-freedom control type magnetic bearing, two types of pseudo position error signals are generated, and it is determined whether the shaft position is closer or farther than the target position with respect to the position detection sensor. A pseudo error signal generator is provided to output a signal,
When the shaft position is outside the measurement range of the position detection sensor, the output of the pseudo error signal generator is used as the position error signal, and when the shaft position is within the measurement range of the position detection sensor, the position command signal and the position are used as the position error signal. 1. A control device for a magnetic bearing, characterized in that the shaft is positioned within a measurement range of a position detection sensor by using a difference between signals of the detection sensor.