Compound Control Device and Method for Gas Film Thickness and Input Voltage of Ultrasonic Suspension Bearing

Abstract

The invention discloses a composite control device and method for the air film thickness and input voltage of an ultrasonic suspension bearing, which includes a main shaft, an ultrasonic suspension bearing, an ultrasonic suspension bearing cage, a laser displacement sensor, a laser position measurement controller, an electric control displacement stage, a stepping motor, a signal generator, a power amplifier and an industrial control computer; the ultrasonic suspension bearing is fixed on the ultrasonic suspension bearing cage, and the ultrasonic bearing cage is fixed on the electric control displacement stage; the ultrasonic suspension bearing is connected to the power amplifier through a cable; the power amplifier is connected to the signal generator through a cable; the signal generator is connected to the industrial control computer through a cable; the laser displacement sensor is connected to the laser position measurement controller; the laser position measurement controller is connected to the industrial control computer through a cable. The invention can actively control the voltage and air film thickness of the ultrasonic suspension bearing, make the bearing in the best working state, and improve the control effect of the spindle rotor rotation error.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic suspension bearings, and particularly to a composite control device and method for the air film thickness and input voltage of an ultrasonic suspension bearing. Background Art

[0002] An ultrasonic suspension bearing is a new type of non-contact bearing using ultrasonic suspension technology. Its principle is to use the radiation force generated by the high-frequency vibration of piezoelectric materials to suspend an object. When the vibration frequency reaches above 16 kHz and the suspension height is small enough, it conforms to the near-field ultrasonic principle. At this time, the radiation force is the near-field ultrasonic suspension force (abbreviated as ultrasonic suspension force), and the bearing based on this technology is a near-field ultrasonic suspension bearing (abbreviated as ultrasonic suspension bearing). This technology has the advantages of simple structure, a large adjustment range of suspension force and driving force, and no additional effect on the object to be operated.

[0003] Currently, there has been research on applying ultrasonic suspension bearings to the spindle field to improve the rotational accuracy of the spindle rotor. However, in actual applications, the ultrasonic suspension force is comprehensively affected by the air film thickness and voltage (here the voltage is the input voltage of the piezoelectric material of the ultrasonic suspension bearing). When the rotor tilts or is eccentric, the optimal working parameters of the ultrasonic bearing also change accordingly. A single working parameter combination can no longer enable the ultrasonic suspension bearing to achieve the best error control effect. Therefore, how to ensure that the ultrasonic suspension bearing is always under the optimal working parameters has become the key to improving the rotational error control effect of the spindle rotor. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the present invention proposes a composite control device and method for the air film thickness and input voltage of an ultrasonic suspension bearing, realizing the automatic adjustment of the air film thickness and input voltage of the ultrasonic suspension bearing and ensuring that the ultrasonic suspension bearing is in the best working state.

[0005] The technical solution of the present invention is as follows:

[0006] A composite control device for the air film thickness and input voltage of an ultrasonic suspension bearing, comprising a spindle, an ultrasonic suspension bearing, an ultrasonic suspension bearing cage, a laser displacement sensor, a laser position measurement controller, an electric control displacement stage, a stepping motor, a signal generator, a power amplifier, and an industrial control computer;

[0007] The ultrasonic suspension bearing is fixed on the ultrasonic suspension bearing cage, and the ultrasonic bearing cage is fixed on the electric control displacement stage; the ultrasonic suspension bearing is connected to the power amplifier through a cable; the power amplifier is connected to the signal generator through a cable; the signal generator is connected to the industrial control computer through a cable;

[0008] The laser displacement sensor is connected to the laser position measurement controller; the laser position measurement controller is connected to the industrial control computer through a cable.

[0009] Furthermore, there are two laser displacement sensors, which are vertically placed and point to the end of the main shaft rotor shaft.

[0010] Furthermore, the electric control displacement stage has two paths of X and Y. The two paths of electric control displacement stages are respectively controlled by stepping motors, and the stepping motors are connected to the industrial control computer through cables.

[0011] The composite control method for the air film thickness of the ultrasonic suspension bearing includes the following steps:

[0012] 1) Start the main shaft to make the main shaft rotor in a moving state;

[0013] 2) The signal generator outputs a high-frequency signal, and the voltage is amplified by the power amplifier to make the ultrasonic suspension bearing generate high-frequency vibration to control the rotational error of the main shaft rotor;

[0014] 3) Use two laser displacement sensors. At every time interval, that is, time step ΔT, measure the radial displacement S of the main shaft rotor under high-speed movement. The measurement time interval is 0.1 ms. S n (n = 1, 2, 3...) is the displacement signal measured at different time steps, and the displacement signal is converted into a digital signal and input into the industrial control computer;

[0015] 4) The industrial control computer processes the collected signals to obtain the rotor motion trajectory, and compares the radial displacement S at the previous time step n-1 with the radial displacement S at this time step n to obtain the difference, and output a voltage control signal and a control signal for the electric control displacement stage; Since the ultrasonic suspension effect can effectively suppress the rotational error of the rotor, including the eccentricity error, the displacement direction of the rotor under acoustic suspension can be judged by the difference in the radial displacement of adjacent time steps measured by the two sensors, so as to control the voltage and the air film thickness of the bearing.

[0016] 5) After receiving the voltage control signal, the power amplifier changes the output voltage. At the same time, the two electric control displacement stages drive the ultrasonic suspension bearing to displace in the X-axis direction and the Y-axis direction to change the air film thickness of the bearing, so that the ultrasonic suspension bearing is under the best working parameters.

[0017] Furthermore, in step 4), if the radial displacement S measured at the previous time step n-1 and the radial displacement S at this time step n the difference S n -S n-1is a positive value, indicating that the rotor has a positive eccentricity relative to its initial axis of rotation. Under the action of ultrasonic suspension, it tends to move in the negative direction and return to its initial axis of rotation. At this time, the system should output a signal to increase the voltage of the ultrasonic suspension bearing in the positive region, and at the same time drive the ultrasonic bearing to move in the positive direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing; if the radial displacement S measured in the previous time step n-1 and the radial displacement S in this time step n The difference S n -S n-1 is a negative value, indicating that the rotor has a negative eccentricity relative to its initial axis of rotation. Under the action of ultrasonic suspension, it tends to move in the positive direction and return to its initial axis of rotation. At this time, the system should output a signal to reduce the voltage of the ultrasonic suspension bearing in the positive region, and at the same time drive the ultrasonic bearing to move in the negative direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing.

[0018] Further, in step 5), when the radial displacement S in the previous time step n-1 and the radial displacement S in this time step n The difference is less than 1×10 -7 m, indicating that the rotational error cannot be reduced any further and the rotor has returned to its initial axis of rotation. At this time, the voltage and air film thickness are the optimal parameters, and the ultrasonic suspension bearing is in the best working state.

[0019] The beneficial effects of the present invention are as follows: The structure of the present invention is simple, easy to use, and has good control effect; it can actively control the voltage and air film thickness of the ultrasonic suspension bearing, so that the bearing is in the best working state and improve the control effect of the rotational error of the spindle rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 is a schematic diagram of the ultrasonic suspension bearing load under the eccentric state of the rotor of the present invention;

[0022] Figure 3 is a flowchart of the active control of the air film thickness and voltage of the ultrasonic suspension bearing of the present invention;

[0023] In the figure: 1, industrial control computer; 2, signal generator; 3, power amplifier; 4, laser displacement sensor; 5, ultrasonic suspension bearing; 6, ultrasonic suspension bearing cage; 7, electric control displacement table; 8, stepping motor; 9, main shaft; 10, laser position measurement controller. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] As Figure 1As shown, the composite control device for the air film thickness and input voltage of an ultrasonic suspension bearing includes an industrial control computer 1, a main shaft 9, an ultrasonic suspension bearing 5, an ultrasonic suspension bearing cage 6, a laser displacement sensor 4, a laser position measurement controller 10, an electric control displacement stage 7, a stepping motor 8, a signal generator 2, and a power amplifier 3.

[0026] The laser displacement sensor 4 is connected to the laser position measurement controller 10; the laser position measurement controller 10 is connected to the industrial control computer 1 through a cable; two laser displacement sensors 4 are vertically placed and point to the end of the main shaft 9; the ultrasonic suspension bearing 5 is fixed on the ultrasonic suspension bearing cage 6; the ultrasonic suspension bearing 5 is connected to the power amplifier 3 through a cable; the power amplifier 3 is connected to the signal generator 2 through a cable; the signal generator 2 is connected to the industrial control computer 1 through a cable; the ultrasonic bearing cage 6 is fixed on two electric control displacement stages 7; the two electric control displacement stages 7 are controlled by the stepping motor 8; the stepping motor 7 is connected to the industrial control computer 1 through a cable.

[0027] Figure 2 In it, O is the coordinate origin, and X and Y respectively represent the X-axis and Y-axis directions of the coordinate axes.

[0028] As Figure 3 shown, the composite control method for the air film thickness and input voltage of an ultrasonic suspension bearing includes the following steps:

[0029] 1) Start the main shaft. When the main shaft rotor is in a stable motion state.

[0030] 2) The signal generator outputs a high-frequency signal of 20 kHz. After the voltage is amplified by the power amplifier, it is input into the ultrasonic suspension bearing. The ultrasonic suspension bearing vibrates under the excitation of the high-frequency signal to generate an ultrasonic suspension force, and the ultrasonic suspension force acts on the main shaft to control the rotational error of the main shaft rotor.

[0031] 3) Use two laser displacement sensors to measure the radial displacement S of the main shaft rotor under high-speed motion every time interval (i.e., time step ΔT). The measurement time interval is 0.1 ms. S n (n = 1, 2, 3...) is the displacement signal measured at different time steps, and the displacement signal is converted into a digital signal and input into the industrial control computer.

[0032] 4) The industrial control computer processes the data to obtain the rotor motion trajectory, compares the displacement difference between the previous time step and this time step, and outputs a voltage control signal and a control signal for the electric control displacement stage.

[0033] Since the ultrasonic suspension effect can effectively suppress the rotational error of the rotor, including the eccentricity error, the displacement direction of the rotor under acoustic suspension can be judged by the difference in the radial displacement of adjacent time steps measured by the two sensors, so as to control the voltage and the air film thickness of the bearing.

[0034] Taking the sensor placed in the positive direction of the x-axis as an example: If the radial displacement S of the X-axis measured in the previous time step n-1 and the radial displacement S of this time step n The difference S n -S n-1 is positive, it indicates that the rotor has a positive X-axis eccentricity relative to its initial rotation axis center at this time, and there is a tendency to move in the negative X-axis direction and return to its initial rotation axis center under the action of ultrasonic suspension. At this time, the system should output a signal to increase the voltage of the ultrasonic suspension bearing in the positive X-axis region, and at the same time drive the ultrasonic bearing to move in the positive X-axis direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing; If the radial displacement S of the X-axis measured in the previous time step n-1 and the radial displacement S of this time step n The difference S n -S n-1 is negative, it indicates that the rotor has a negative X-axis eccentricity relative to its initial rotation axis center at this time, and there is a tendency to move in the positive X-axis direction and return to its initial rotation axis center under the action of ultrasonic suspension. At this time, the system should output a signal to decrease the voltage of the ultrasonic suspension bearing in the positive X-axis region, and at the same time drive the ultrasonic bearing to move in the negative X-axis direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing.

[0035] 5) After receiving the voltage control signal, the power amplifier changes the output voltage. After receiving the control signal, the two-way electric control displacement stage can drive the ultrasonic suspension bearing to displace in the X-axis direction and the Y-axis direction, changing the air film thickness of the ultrasonic suspension bearing. When the displacement difference between the previous time step and this time step is less than 1×10 -7 m, it means that the rotational error cannot be reduced any further. At this time, the voltage and the air film thickness are the optimal parameters, and the ultrasonic suspension bearing is in the best working state.

[0036] Figure 3 In the above, S is the displacement of the spindle rotor measured by the laser displacement sensor.

[0037] The content described in the embodiments of this specification is only a partial enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be limited only to the specific forms stated in the embodiments. The protection scope of the present invention extends to equivalent technical means that can be conceived by those skilled in the art based on the technical concept of the present invention.

Claims

1. A composite control method for the air film thickness and input voltage of an ultrasonic suspension bearing, based on a composite control device for the air film thickness and input voltage of an ultrasonic suspension bearing, characterized in that, The device includes a main shaft, an ultrasonic suspension bearing, an ultrasonic suspension bearing cage, a laser displacement sensor, a laser position measurement controller, an electric control displacement stage, a stepping motor, a signal generator, a power amplifier and an industrial control computer; The ultrasonic suspension bearing is fixed on the ultrasonic suspension bearing cage. The ultrasonic suspension bearing cage, as a metal bracket for fixing the ultrasonic suspension bearing, is installed on the electric control displacement stage. The ultrasonic suspension bearing is connected to the power amplifier through a cable. The power amplifier is connected to the signal generator through a cable. The signal generator is connected to the industrial control computer through a cable; The laser displacement sensor is connected to the laser position measurement controller. The laser position measurement controller is connected to the industrial control computer through a cable; The method includes the following steps: 1) Start the main shaft to make the main shaft rotor in a moving state; 2) The signal generator outputs a high-frequency signal, which is amplified in voltage by the power amplifier, so that the ultrasonic suspension bearing generates high-frequency vibration to control the rotational error of the main shaft rotor; 3) Two laser displacement sensors are adopted, and at each time interval, namely the time step , the radial displacement of the main shaft rotor under high-speed movement is measured S . The measurement time interval is 0.1 ms, which is the displacement signal measured at different time steps, and the displacement signal is converted into a digital signal and input into the industrial control computer; 4) The industrial control computer processes the collected signals to obtain the rotor motion trajectory, and compares the radial displacement at the previous time step with the radial displacement at this time step to obtain the difference, and outputs the voltage control signal and the control signal for the electric control displacement stage; 5) After receiving the voltage control signal, the power amplifier changes the output voltage. At the same time, the two-way electric control displacement stage drives the ultrasonic suspension bearing to displace in the X-axis direction and the Y-axis direction, thereby changing the bearing air film thickness, so that the ultrasonic suspension bearing is under the best working parameters.

2. The composite control method for the gas film thickness and input voltage of the ultrasonic suspension bearing according to claim 1, characterized in that There are two laser displacement sensors, which are vertically placed and point to the end of the main shaft rotor.

3. The composite control method for the air film thickness and input voltage of the ultrasonic suspension bearing according to claim 1, wherein The electric control displacement stage has two paths of X and Y. The two paths of electric control displacement stage are respectively controlled by stepping motors, and the stepping motors are connected to the industrial control computer through cables.

4. The composite control method for the air film thickness and input voltage of the ultrasonic suspension bearing according to claim 1, wherein In step 4), if the radial displacement measured at the previous time step and the radial displacement at this time step has a difference that is positive, it indicates that the rotor has a positive eccentricity relative to its initial axis of rotation. Under the action of ultrasonic suspension, it tends to move in the negative direction and return to its initial axis of rotation. At this time, the system should output a signal to increase the voltage of the ultrasonic suspension bearing in the positive region, and at the same time drive the ultrasonic bearing to move in the positive direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing; if the radial displacement measured at the previous time step and the radial displacement at this time step has a difference that is negative, it indicates that the rotor has a negative eccentricity relative to its initial axis of rotation. Under the action of ultrasonic suspension, it tends to move in the positive direction and return to its initial axis of rotation. At this time, the system should output a signal to decrease the voltage of the ultrasonic suspension bearing in the positive region, and at the same time drive the ultrasonic bearing to move in the negative direction, so that the rotor is centered in the structural position inside the air film of the ultrasonic bearing.

5. The composite control method for the air film thickness and input voltage of an ultrasonic suspension bearing according to claim 1, characterized in that In step 5), when the difference between the radial displacement at the previous time step and the radial displacement at this time step is less than m, it means that the rotational error cannot be reduced any further, and the rotor has returned to the initial axis of rotation. At this time, the voltage and the gas film thickness are the optimal parameters, and the ultrasonic suspension bearing is in the optimal working state.​​​​​​

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