CN101231386A - Dynamic Correction System of Torsion Angle of Rotary Shaft Rotational Axis of Rolling Friction Drive for Extremely Large Astronomical Telescope - Google Patents

Abstract

The dynamic correction system for the torsion angle of the rotating shaft of the extremely large astronomical telescope is a rolling friction transmission. The rotation axes of the driving wheel and the driven wheel are arranged in parallel. The driving motor, the driving wheel and the support bearing form the structure of the driving wheel. The rotating support point is mounted on the pillar; the driving wheel structure is installed on the left end of the connecting lever, and the right end of the connecting lever is equipped with a balance weight; there is also a length gauge for real-time detection of the up and down movement of the connecting lever, and a signal input control system for the length gauge; The rightmost end of the connecting lever is equipped with an adjustment mechanism: a steel ball is set on the upper and lower ends of the rightmost end of the connecting lever in a freely rotatable manner, and there is a gap between the connecting lever and the driving bracket. The correction motor is controlled by the control system. The invention can detect the torsion angle of the rotation axis of the driving wheel and the driven wheel in real time and perform online adjustment. It avoids the "jump" caused by the torsion angle and ensures the stable operation of the telescope.

Description

Dynamic Correction System of Torsion Angle of Rotary Shaft Rotational Axis of Rolling Friction Drive for Extremely Large Astronomical Telescope

technical field

The invention relates to a mechanical transmission device, in particular to a dynamic correction system for the torsion angle of a rotating shaft of a rolling friction transmission of a very large astronomical telescope. This invention is funded by the National Natural Science Foundation of China.

Background technique

Outer circle rolling friction transmission has been applied in large astronomical telescopes due to its simple structure, no backlash, relatively convenient installation, commissioning and maintenance. For example, the 10-meter-caliber Keck astronomical telescope in the United States and the 8-meter-caliber Gemini astronomical telescope, etc., and the 4-meter-caliber LAMOST astronomical telescope currently under development in China also uses outer circular rolling friction transmission. Ideally, the rotation axes of the driving wheel and the driven wheel of the outer circular rolling friction transmission should be parallel in space. However, due to reasons such as installation and long-term operation, the relative positions of the rotation axes of the driving wheel and the driven wheel will change, that is, there is an angle between them in space. The schematic diagram of the included angle is shown in Figure 1 and Figure 2. The angle β between the rotation axes of the driving wheel and the driven wheel in the radial direction is called the inclination angle, and the angle θ in the tangential direction is called the torsion angle. Friction transmission works under the action of positive pressure, so under the action of positive pressure, the inclination angle β will disappear or become very small, which has little effect on the transmission.

But the existence of twist angle is very harmful. A friction drive with a torsion angle is similar to a torsion wheel friction drive. Due to the existence of the torsion angle θ, the friction force F _d generates an axial component force F _t on the rotation axis of the driven wheel through the torsion angle θ.

F _t =F _d ×sinθ

The function of Ft is to cause the driven wheel to move in the axial direction. But in general, the driven wheel is heavy and rigid, while the driving wheel is relatively weak, so it will cause the driving wheel to move in the opposite direction. The specific performance is that the driving wheel has elastic deformation in a certain direction. In particular, the elastic deformation of the supporting rod of the driving wheel occurs. As time goes by, the elastic deformation of the member is also increasing. When the restoring force of the elastic deformation of the rod accumulates to a certain extent and exceeds the axial friction force between the driving wheel and the driven wheel, the driving wheel will "jump" back to the equilibrium position, that is, slide each other. Make the movement between the driving wheel and the driven wheel asynchronous. The transmission accuracy of astronomical optical telescopes is usually about 0.2 arc seconds, and the tracking error caused by "snap jump" is much higher than 0.2 arc seconds. For multi-target fiber optic spectroscopic telescopes, it means that the target celestial body that was originally aligned will be partially or even completely offset from the fiber optic head. The observation of a large number of optical fiber spectra only emerged in the 1990s. Therefore, two methods are usually used to solve this problem: one is to abandon this set of data, and the other is to adjust the mechanical structure. The time for the astronomical telescope to obtain a set of observation data varies, and sometimes the exposure time reaches 1.5 hours. The observation time of a telescope at night is only about 6 hours. Therefore, this problem seriously affects the observation efficiency of astronomical telescopes. For example. LAMOST aims at 4,000 target celestial objects at a time and tracks them continuously for 1.5 hours. This "snap" will lead to the waste of all previous efforts. For astronomical telescopes whose working time is very precious, this seriously affects the working efficiency and output of the telescope. If the mechanical structure is readjusted, it will take a long time and a large workload.

Therefore, there is an urgent need to adopt a dynamic system of real-time detection and real-time correction to detect and adjust the torsion angle of the driving wheel and driven wheel axis of rotation in time before the "jump" occurs, so that the transmission system works in a stable state. However, there is no technical solution for completing this task in the prior art.

Contents of the invention

In view of the above-mentioned problems in the prior art, the purpose of this application is to provide a dynamic correction system for the torsion angle of the rotating shaft of the rolling friction transmission of a very large astronomical telescope. By adopting this dynamic correction system, the rotation axis of the driving wheel and the rotation axis of the driven wheel are always kept parallel in the tangential direction during the friction transmission process, ensuring that the movement of the driving wheel and the driven wheel are synchronized, avoiding the occurrence of "jump" phenomenon, and ensuring that the telescope Can work stably.

The technical scheme adopted in the present invention is: a dynamic correction system for the torsion angle of the rolling friction transmission rotating shaft of a very large astronomical telescope. The structure is characterized in that it is provided with a connecting lever, which is mounted on the pillar through a rotating support point, and the connecting lever can rotate around the supporting point relative to the pillar; the driving wheel structure is installed on the left end of the connecting lever (relative to The right end of the connecting lever is equipped with a balance weight; the right end of the connecting lever is provided with a length meter for real-time detection of the up and down movement of the connecting lever, and the signal of the length meter is input into the control system through the data line; The rightmost end of the lever is equipped with an adjustment mechanism. The structure of the adjustment mechanism is: a steel ball is respectively set up and down the rightmost end of the connecting lever. The two steel balls are installed on the bracket in a freely rotatable manner and connected with the There is a gap between the rightmost ends of the levers; at the same time, a correction motor is provided to drive the bracket to move up and down, and the correction motor is controlled by the control system according to the signal fed back by the length gauge.

If there is a torsion angle between the rotation axis of the driving wheel and the rotation axis of the driven wheel, the frictional force has a component force in the axial direction, and this force will cause the driving wheel (friction wheel) to move in the axial direction. The length gauge can detect this movement in real time and feed back the signal to the control system. The control system drives the bracket of the adjustment mechanism to move up and down according to the signal, and adjusts the rightmost end of the connecting lever through the steel ball. Realize the real-time adjustment of the torsion angle.

In the present invention, under the action of the driving wheel structure and the balance weight, the connecting lever is balanced relative to the rotation support point. this point is very important. Only when the balance of the connecting lever is ensured, can the component force of the frictional force in the axial direction be easily detected, thereby detecting the change of the torsion angle, and then making corresponding adjustments. Otherwise, the axial component force of the friction force will be disturbed by the unbalanced force, and the torsion angle cannot be detected and adjusted. The unbalanced moment is controlled within 0.5N-m. If the weight of the driving wheel structure changes, the balance can be adjusted by adjusting the position of the balance weight on the connecting lever.

In order to reduce the influence of friction torque, rolling bearings with a small friction coefficient are used at the rotating support point, and the friction torque is about 0.2N-m.

Various frictional moments in the lever balance structure should be small, and its value is generally one-tenth of the axial component moment.

The length meter is used to detect the up and down movement of the connecting lever in real time. The distance between the length meter and the rotating support point should be as long as possible, so that the up and down movement of the driving wheel can be amplified, which is convenient for the detection of the length meter. At the same time, the detection resolution of the length meter can also be reduced. requirements. Therefore, the length gauge is generally set on the right side of the balance weight.

The steel ball of the adjustment mechanism is not in contact with the connecting lever at ordinary times, and there is a gap h between the two. The h value is determined according to the length of the lever arm connecting the lever, generally around 2mm. The connecting lever is symmetrical with respect to the positions of the upper and lower steel balls.

The invention solves the technical difficulties in the traditional solutions. The dynamic correction system of the present invention can detect on-line and real-time the torsion angles of the rotation axis of the driving wheel and the rotation axis of the driven wheel in the outer circular rolling friction transmission, and can perform online adjustment according to the detection situation. The "jump" caused by the torsion angle is avoided, the stable operation of the telescope is guaranteed and the use efficiency of the telescope is improved.

Description of drawings

Figure 1 shows the angle β between the axis of rotation of the driving wheel and the driven wheel in the radial direction, which is called the inclination angle;

Figure 2 shows the angle θ between the axis of rotation of the driving wheel and the driven wheel in the tangential direction, which is called the torsion angle;

Fig. 3 is a schematic diagram of the structure of the present invention.

Detailed ways

Embodiment 1, a dynamic correction system for the torsion angle of the rotating shaft of the rolling friction transmission of the extremely large astronomical telescope. Referring to Fig. 3: the driving motor 1 is connected with the driving wheel 2 through a coupling, the connecting lever 5 is mounted on the pillar 11 through the rotating support point 4, and the connecting lever 5 can rotate around the supporting point relative to the pillar 11. The driving wheel structure (comprising drive motor 1, driving wheel 2 and support bearing 3) is fixedly connected to the left end of the connecting lever 5 (relative to the pillar 11, the same below), and the right end of the connecting lever 5 is equipped with a balance weight 6, so that the connecting lever 5 is balanced under the effect of driving wheel structure and balance weight with respect to rotating supporting point 4. The unbalanced moment is controlled within 0.5N-m. At the same time, in order to reduce the influence of friction torque, rolling bearings with a small friction coefficient are used at the rotating support point, and the friction torque is about 0.2N-m. If the weight of the driving wheel structure changes, the balance can be adjusted by adjusting the position of the balance weight 6 on the connecting lever 5 . The length meter 10 is used to detect the up and down movement of the connecting lever in real time. The distance between the length meter 10 and the rotating support point 4 is as long as possible, as shown in Figure 3, so that the up and down movement of the driving wheel can be amplified to facilitate the detection of the length meter. It can also reduce the requirements for the detection resolution of the length gauge. The signal of the length gauge is input into the control system through the data line. The rightmost end of the connecting lever is equipped with an adjusting mechanism 8, and the steel ball 7 of the adjusting mechanism does not contact the connecting lever 5 at ordinary times, and there is a gap h between the two. The h value is determined according to the length of the lever arm of the connecting lever 5, generally about 2 millimeters, and the connecting lever 5 is symmetrical with respect to the positions of the upper and lower steel balls. The control system drives the adjustment mechanism 8 through the drive motor 9 according to the signal fed back by the length meter, so as to realize the real-time adjustment of the torsion angle.

Claims (6)

1. maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system, the driving wheel of friction gearing and the shaft axis of engaged wheel be arranged in parallel, drive motor, driving wheel and spring bearing constitute the driving wheel structure, it is characterized in that, be provided with one and connect lever, this connects lever by rotating strong point frame on pillar, connects lever and can rotate around the strong point with respect to pillar; Described driving wheel structure is installed on the left end that connects lever, is furnished with damper weight at the right-hand member of this connection lever; Be provided with the length gauge that real-time detection connects the upper and lower motion of lever at the right-hand member that connects lever, the signal of this length gauge is by the data line input control system; At the low order end that connects lever adjusting mechanism is housed, the structure of this adjusting mechanism is: upper and lower a steel ball is set respectively what connect the lever low order end, but these two steel balls are rack-mount with free rotation mode, and leave a gap between the lever low order end with being connected; Simultaneously, also be provided with the upper and lower mobile correction motor of driving arm, this revises motor by the signal controlling of control system according to the length gauge feedback.

2. maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system according to claim 1 is characterized in that, the unbalanced moments of described driving wheel structure and damper weight is controlled in the 0.5N-m.

3. maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system according to claim 1 is characterized in that, the rolling bearing that rotation strong point place adopts, and its friction torque is about 0.2N-m.

4. maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system according to claim 1 is characterized in that various moment of frictions are little in the lever balance structure, and its value is 1/10th of axial thrust load moment.

5. maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system according to claim 1 is characterized in that described length gauge is arranged on the right side of damper weight.

6. according to the described maximum astronomical telescope rollig friction transmission rotational axis torsion angle dynamic correction system of one of claim 1～5, it is characterized in that, the steel ball of adjusting mechanism at ordinary times be connected gap width between the lever in 2 millimeter.

Images