JP2767136B2 - Control device for magnetic bearing spindle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for a magnetic bearing spindle, and more particularly to a control device when an active control type magnetic bearing spindle is used as a spindle for deep hole cylindrical inner surface grinding.

[Prior Art] For example, when precisely grinding the inner surface of a long cylinder, honing is usually performed after grinding with an air spindle equipped with a long quill. However, according to this method, since the compliance of the long quill is high, there is a drawback that the quill is elastically deformed by the back force of the grinding resistance, and the inner surface shape after processing follows that before processing. On the other hand, a processing method is conceivable in which the inner surface shape is measured first, and the spindle main body is vibrated in order to change the cutting amount according to the data. However, this method has a drawback that a large power loss occurs and it is difficult to operate at a high speed.

[Problems to be Solved by the Invention] The magnetic bearing spindle supports the main shaft in a non-contact manner by a magnetic force, and the gap between the touchdown bearing and the main shaft is several hundred microns. The magnetic bearing spindle can vibrate only the main shaft by changing the command value of the main shaft support position within this gap range. Thus, the above-described problem of operating at high speed can be solved. However, there is a problem that the damping coefficient of the magnetic bearing is small, the target value command always involves overshoot, and the position of the grindstone at the tip of the quill differs from the command position due to the elastic deformation of the long quill.

Therefore, a main object of the present invention is to create a model of a grinding machine system in consideration of elastic deformation of a long quill when precisely grinding the inner surface of a long cylinder or the like, and using an observer based on this model. An object of the present invention is to provide a magnetic bearing spindle control device that controls the position of a grindstone or the like and controls the bearing stiffness in accordance with the grinding force.

Means for Solving the Problems The invention according to a first aspect is a control device for controlling a magnetic bearing spindle in which a long quill for inner surface grinding of a deep hole cylinder is mounted on a main shaft, wherein a front portion of the main shaft is provided. Front magnetic bearing for magnetically levitating and supporting, a rear magnetic bearing for magnetically levitating and supporting the rear part of the main shaft, and front displacement detecting means for detecting a displacement of a front part of the main shaft, A rear displacement detecting means for detecting a rear displacement of the main shaft, a current value flowing through each of the front magnetic bearing and the rear magnetic bearing,
Based on the detected outputs of the front displacement detecting means and the rear displacement detecting means, and the respective differential outputs, the position and the displacement speed of the grindstone portion of the long quill for deep hole cylindrical inner surface grinding mounted on the main shaft are estimated. And a control means for controlling the front magnetic bearing and the rear magnetic bearing by correcting the target value with the value estimated by the estimating means.

[Operation] A control device for a magnetic bearing spindle according to the present invention includes:
The long quill for grinding the inner surface of a deep hole cylinder, which is an elastic body of distributed constant system, is concentrated into a cantilever beam with the mass concentrated at the tip, and the current value flowing through the front magnetic bearing and the rear magnetic bearing, and the front and rear parts Based on the displacement and the respective differential signals, the position and the displacement speed of the grindstone portion are estimated, and the target value is corrected with the estimated value. Thus, when the inner surface of a long cylinder or the like is precisely ground, a grinding force corresponding to the shape of the workpiece can be applied to the grindstone portion, and the problem that the shape after processing follows the shape before processing can be solved.

FIG. 1 is a schematic block diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing an outline of a magnetic bearing spindle.

In the magnetic bearing spindle, as shown in FIG. 2, a main shaft 7 is supported by a front magnetic bearing 1 and a rear magnetic bearing 4 in a non-contact manner by a magnetic force. The front magnetic bearing 1 includes a front electromagnet 2 and a front sensor 3, and the rear magnetic bearing 4 includes a rear electromagnet 5 and a rear sensor 6. A long quill 25 is attached to the tip of the main shaft 7, and a grindstone is attached to the tip of the long quill 25.
26 are installed. When pressure Fd is applied to the grindstone part 26,
The long quill 25 is bent. Therefore, in the present invention, the long quill 25 is concentrated into a cantilever beam in which the mass is concentrated on the grindstone part 26, and a model of the entire magnetic bearing spindle including the quill is created. Estimate position and displacement velocity.

For this purpose, as shown in FIG. 1, the current value of the front electromagnet 2, the output of the front sensor 3 and its differential signal, the current value of the rear electromagnet 5, the output of the rear sensor 6 and its differential signal are used as a grinding wheel. The position and speed are given to the observer 21.

The observer 21 is provided for estimating the position displacement speed of the grindstone unit 26 based on the current values of the front electromagnet 2 and the rear electromagnet 5, the respective outputs of the front sensor 3 and the rear sensor 6, and the respective differential signals. Can be Observer
The value of the position of the grindstone 26 estimated by 21 is used as a front sensor correction signal and a rear sensor correction signal as adders 19 and 20.
Given individually.

The adder 19 adds the front sensor correction signal to the detection signal of the front sensor 3 and provides the same to the comparator 8. Further, the adder 20 adds the rear sensor correction signal to the detection output of the rear sensor 6 and provides the same to the comparator 13. The comparator 8 subtracts the output of the adder 19 from the target value and supplies it to the PID control circuit 9, and the comparator 13 subtracts the output of the adder 20 from the target value and supplies it to the PID control circuit 14. The PID control circuits 9 and 14 perform arithmetic processing on the applied signals and output control signals to be applied to the front electromagnet 2 and the rear electromagnet 5. Outputs of the PID control circuits 9 and 14 are supplied to adders 10 and 15, respectively.

Further, the pressure Fd applied to the grindstone part 26 measured directly or indirectly is given to the compensation circuit 12, the output of the compensation circuit 12 is given to the adders 10, 15, and the output of the PID control circuits 9, 14 is given to each output. The signals are added and supplied to the power amplifiers 11 and 16.
The power amplifiers 11 and 16 respectively drive the front electromagnet 2 and the rear electromagnet 5 based on the applied control signals.

[Effects of the Invention] As described above, according to the present invention, a long quill of an elastic body, which is a distributed constant, is concentrated into a cantilever beam in which mass is concentrated on the grindstone portion, and the entire magnetic bearing spindle including the long quill is provided. Based on this model, based on the current values flowing through the front magnetic bearing and the rear magnetic bearing, the displacement of the front and rear parts, and the respective differential signals, the inner surface grinding of the deep hole cylinder attached to the main shaft Since the position and displacement speed of the grindstone portion of the long quill are estimated and the target value is corrected with the estimated value, it is possible to apply a grinding pressure according to the workpiece shape to the grinding tool.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of one embodiment of the present invention.
FIG. 2 is a diagram showing an outline of a magnetic bearing spindle. In the figure, 1 is a front magnetic bearing, 2 is a front electromagnet, 3 is a front sensor, 4 is a rear magnetic bearing, 5 is a rear electromagnet, 6 is a rear sensor, 7 is a main shaft, 8, 13 are comparators, 9 , 14 are PID control circuits, 10, 15, 19, 20 are adders, 11, 16 are power amplifiers, 12
Denotes a compensation circuit, 17 and 18 denote differentiators, 25 denotes a long quill, and 26 denotes a grindstone unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-60492 (JP, A) JP-A-63-191571 (JP, A) JP-A-1-234162 (JP, A) JP-A-1- 127254 (JP, A) JP-A-63-13918 (JP, A) JP-A-1-240267 (JP, A) JP-A-1-316168 (JP, A) JP-A-59-89820 (JP, A) JP-A-57-65416 (JP, A) JP-A-57-65415 (JP, A) JP-A-1-137302 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24B 41/04 F16C 32/04 G05D 3/12

Claims (1)

(57) [Claims] 1. A control device for a magnetic bearing spindle for controlling a magnetic spindle in which a long quill for inner surface grinding of a deep hole cylinder is mounted on a main shaft, for magnetically levitating and supporting a front portion of the main shaft. A front magnetic bearing, a rear magnetic bearing for magnetically levitating and supporting a rear portion of the main shaft, a front displacement detecting unit for detecting a front displacement of the main shaft, and detecting a rear displacement of the main shaft. For the rear displacement detection means, based on the current value flowing in each of the front magnetic bearing and the rear magnetic bearing, the detection output of each of the front displacement detection means and the rear displacement detection means, and the respective differential signal Estimating means for estimating the grinding wheel position and displacement speed of a long quill for deep hole cylindrical inner surface grinding attached to the spindle, and correcting the target value with the value estimated by the estimating means Serial provided with a control means for controlling the front magnetic bearing and a rear magnetic bearing control device of the magnetic bearing spindle.