A two-rotary-degree-of-freedom synchronous control precision rotary table device and error compensation method

Abstract

The application discloses a two-rotary-freedom-degree synchronous control precision rotary table device and an error compensation method, and belongs to the technical field of precision measurement and instrument technology. The device is composed of an X-axis rotary control unit I, a Y-axis rotary control unit II and a position and posture measurement and control unit III. The X-axis and Y-axis rotary control units are independent of each other, and can realize the synchronous precise control of two-freedom-degree rotation. The position and posture measurement and control unit can realize zero position calibration, rotation compensation and device tensioning. The application also provides the two-rotary-freedom-degree synchronous control precision rotary table device and the error compensation method. The displacement deviation value is converted into a rotary compensation value through a linear grating ruler, and a new method is adopted to compensate the transmission error and the back-lash caused by multi-stage transmission, so as to overcome the insufficient precision of two-freedom-degree rotation synchronous control and the miniaturization problem of the precision rotary table device.

Description

Technical Field

[0001] This invention relates to a precision turntable device for synchronous control of two rotational degrees of freedom and an error compensation method, belonging to the field of precision measurement technology and instrument technology. Background Technology

[0002] With the development of technology, the requirements for the rotational accuracy of precision turntables in mechanical equipment are becoming increasingly higher. Precise control of rotation has become a key technology in precision manufacturing and measurement. The rotational accuracy of precision turntables directly affects the performance of the whole machine and has a wide range of applications in the fields of defense industry, aerospace, and precision manufacturing.

[0003] Currently, there are few multi-degree-of-freedom turntable devices and error compensation methods for synchronous rotation control. On the one hand, multi-stage transmission errors in the equipment inevitably affect the accuracy of rotation. For example, introduced transmission errors and hysteresis can severely affect the rotation accuracy at the end of the turntable device. Correspondingly, error compensation methods have become the main means of solving this problem. On the other hand, miniaturization of multi-degree-of-freedom turntable devices is both a mainstream demand and a current research challenge. The reason why turntable devices are difficult to miniaturize is that conventional rotation control involves coaxially mounting a circular grating with the turntable. The rotation is controlled by quantifying the rotation on the circular grating. The denser the scale lines, the more accurate the rotation control, but the larger the corresponding circular grating volume. In addition, denser scale lines often mean a more expensive circular grating. For example, a precision-grade circular grating with a diameter of 20cm costs more than 50,000 yuan, making it difficult to promote and apply multi-degree-of-freedom rotation control turntable devices. In summary, there is a significant market demand for existing precision turntables for synchronous control of multiple degrees of freedom, improved rotation accuracy, and miniaturization of turntable devices.

[0004] To overcome the above problems, this invention discloses a precision turntable device and error compensation method for synchronous control of two rotational degrees of freedom. It comprehensively considers and upgrades the shortcomings of existing precision turntables, and innovatively adopts a new method of linearly compensating for rotational deviation by using mutually independent multi-degree-of-freedom rotational control units. This not only enables precise synchronous control of the rotational amounts of the X and Y axes through error compensation, but also miniaturizes the precision turntable device and promotes the application of multi-degree-of-freedom precision turntables. Summary of the Invention

[0005] This invention addresses the problem of insufficient accuracy in synchronous control of two-degree-of-freedom rotation caused by transmission errors and backlash introduced by multi-stage transmission in precision rotary tables. It provides a synchronous X and Y axis rotation control unit that converts rotational quantities into length quantities, thereby achieving rotational accuracy control and compensation.

[0006] This invention innovates upon existing turntable devices in terms of principle. The basic ideas are: 1. The multi-degree-of-freedom rotation control units are independent of each other, enabling both synchronous rotation control of multiple axes and precise single-axis control of a specific rotation amount. 2. A new error compensation method is proposed to achieve accurate compensation of the rotation amount. The actual linear displacement is read by a grating reading head, and the deviation between the actual and theoretical belt linear displacement is used to obtain the precise number of motor compensation pulses, thereby improving the control accuracy of the rotation amount.

[0007] To achieve the above objectives and principles, the technical solution of this invention is as follows:

[0008] A precision turntable device for synchronous control of two rotational degrees of freedom consists of three parts: an X-axis rotation control unit I, a Y-axis rotation control unit II, and a posture measurement and control unit III.

[0009] The X-axis rotation control unit I includes a front servo motor 1, an X-axis 2, a support bearing seat 3, and a support platform 4;

[0010] The front servo motor 1 is connected to the X-axis 2 by a coupling. The X-axis 2 is fixedly supported by the support bearing seat 3 and is rigidly connected to the support platform 4.

[0011] The front servo motor 1, X-axis 2, support bearing seat 3 and support platform 4 control the rotation accuracy of probe 11 around X-axis 2. According to the required rotation amount of X-axis 2, the front servo motor 1 runs the corresponding number of pulses to drive X-axis 2 to rotate, thereby realizing the control of the rotation accuracy of probe 11 around X-axis 2.

[0012] The Y-axis rotation control unit II includes a left-side servo motor 5, a short shaft 6, a short shaft bearing seat 7, a bevel gear set 8, a Y-axis 9, a turntable 10, a probe 11, a turntable bearing seat 12, and a limiter 22;

[0013] The left servo motor 5 is bolted to the left side of the support platform 4. The left servo motor 5 is connected to the short shaft 6 by a coupling. The short shaft 6 is fixedly supported by the short shaft bearing seat 7. The short shaft bearing seat 7 is bolted to the turntable bearing seat 12.1. The short shaft 6 is keyed to the bevel gear set 8. The bevel gear set 8 is keyed to the Y-axis 9. The Y-axis 9 is rigidly connected to the turntable 10. The X-axis 2 and the Y-axis 9 are mutually perpendicular axes. The intersection of the two axes is located at the center of the turntable 10. The probe 11 is bolted to the turntable 10. The Y-axis 9 is fixedly supported by the turntable bearing seat 12. The turntable bearing seat 12 is bolted to the support platform 4. A limiter 22 is installed at the right end of the Y-axis 9.

[0014] The left servo motor 5, short shaft 6, bevel gear set 8, Y-axis 9, turntable 10 and turntable bearing seat 12 control the rotation accuracy of probe 11 around Y-axis 9. The left servo motor 5 runs the corresponding number of pulses to drive the short shaft 6 to rotate. The short shaft 6 drives the Y-axis 9 to rotate through the bevel gear set 8. Since the bevel gear set 8 has transmission error and backlash, it is necessary to compensate for the rotation amount to achieve the rotation accuracy control of probe 11 around Y-axis 9.

[0015] The limiter 22 is used to limit the rotation of the Y-axis 9, which controls the displacement of the belt 13.3. Limiting the rotation of the Y-axis 9 ensures that the grating reading head 14 can always be fixed on the upper side of the belt 13.3.

[0016] The pose measurement and control unit III includes a turntable 10, a probe 11, a turntable bearing seat 12, a belt device 13, a grating reading head 14, a linear grating ruler 15, a grating support 16, a sliding bearing seat 17, a support shaft 18, a slider 19, a slide rail 20, a tension spring 21, a CCD support 23, and a CCD camera 24.

[0017] The probe 11 is bolted to the turntable 10. A CCD camera 24 is placed directly behind the probe 11 and the turntable 10 via a CCD support 23. A belt assembly 13 is installed between turntable bearing housings 12.2 and 12.3. Pulleys 13.1 and 13.2 are respectively mounted on the Y-axis 9 and the support shaft 18. The belt 13.3 is connected to pulleys 13.1 and 13.2. The Y-axis 9 is fixedly supported by the turntable bearing housing 12, and the support shaft 18 is fixedly supported by a sliding bearing housing 17. The turntable bearing housing 12 is bolted to the support platform 4. Above, the sliding bearing seat 17 is fixed to the slider 19 by bolts. The grating support 16.1 is installed above the turntable bearing seat 12.2 and the turntable bearing seat 12.3 by bolts. The grating support 16.2 is installed above the sliding bearing seat 17.1 and the sliding bearing seat 17.2 by bolts. A linear grating ruler 15 is installed between the grating support 16.1 and the grating support 16.2. The grating reading head 14 is fixed to the belt 13.3. The slider 19 is stuck in the slide rail 20. The slide rail 20 is fixed to the support platform 4 by positioning plate and bolts. A tension spring 21 is installed on the inner side of the slide rail 20.

[0018] The probe 11 and CCD camera 24 are used to achieve zero-position calibration of the probe 11. The probe 11 emits a linear laser, which is received by the CCD camera 24. The position and length of the laser beam determine whether the probe 11 is at the initial position of the X-axis 2 and Y-axis 9. In imaging, when the linear laser is perpendicular to the horizontal line, the probe 11 reaches the initial position of the X-axis 2. When the linear laser is at its longest position on the vertical line, the probe 11 reaches the initial position of the Y-axis 9. When both are reached simultaneously, the probe 11 is at the zero position.

[0019] The left servo motor 5, belt 13.3, and grating reading head 14 use a compensation method to compensate for the rotation of the Y-axis 9. The grating reading head 14 can read the actual displacement data of the belt 13.3 when the Y-axis 9 rotates in real time. Then, the deviation value between the actual displacement data and the theoretical displacement data is converted into a pulse number to drive the left servo motor 5 to run, thereby compensating for the rotation of the Y-axis 9 and realizing the precision control of the rotation of the probe 11 around the Y-axis 9.

[0020] The tension spring 21 provides preload to the belt device 13. When the tension spring 21 is in a compressed state, it provides elastic force to the slider 19 to the outside of the support platform 4, so that the belt 13.3 is in a taut state.

[0021] An error compensation method, wherein the calculation of the compensation rotation amount is performed according to the following steps:

[0022] 1) Calibrate the initial position. Use a CCD camera to adjust the probe to the zero position.

[0023] 2) Coarse adjustment of Y-axis rotation. In order to accurately control the Y-axis rotation as b, the rotation of the Y-axis is converted into the linear displacement of the belt using belt drive. The motor runs for B pulses to initially obtain the Y-axis rotation b0.

[0024] B=N×(b÷360) (1)

[0025] Where b represents the rotation around the Y-axis, B represents the number of motor pulses, N represents the number of motor pulses for one revolution around the Y-axis, and b0 represents the coarse adjustment rotation.

[0026] 3) Initial compensation for Y-axis rotation. The belt displacement deviation value ΔL is converted into motor pulse count N to compensate for the Y-axis rotation.

[0027] ΔL=Lactual-Ltheoretical(2)

[0028] Lli = S × (b ÷ 360) (3)

[0029] Ncomplement = N × (ΔL ÷ S) (4)

[0030] Where S is the circumference of the belt around the pulley, Ncomplement is the number of motor error compensation pulses, and Lactual is the actual belt displacement read in real time by the grating reading head. 理 ΔL represents the theoretical displacement of the belt, and ΔL represents the belt displacement deviation.

[0031] 4) Fine-tune the Y-axis rotation. After the initial compensation of the Y-axis rotation, read the L value again. 实 We obtain ΔL, and use ΔL to convert into pulse count to run the motor to compensate for the rotation amount. We repeat step three multiple times until ΔL = 0, thus achieving precise control of the Y-axis rotation amount as b.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention can simultaneously and precisely control the rotation of multiple axes, enabling both single-axis rotation control of the X-axis or Y-axis, and synchronous rotation control of two rotational degrees of freedom of the X-axis and Y-axis.

[0034] 2. In this invention, a linear grating ruler is used to convert the displacement deviation value into a rotation compensation amount, thereby achieving rotational accuracy control and compensation, which can improve the control accuracy of the rotation amount of the precision turntable.

[0035] 3. In this invention, a linear grating ruler is used instead of a circular grating, which reduces costs, simplifies installation, and enables the miniaturization of the device.

[0036] 4. The error compensation method used in this invention can compensate for the transmission error and backlash introduced by multi-stage transmission. Attached Figure Description

[0037] Figure 1 Overall drawing of a precision turntable device with synchronous control of two rotational degrees of freedom

[0038] Figure 2 Position and attitude measurement and control unit III zero-position calibration structure diagram

[0039] Figure 3 Position and attitude measurement and control unit III rotation compensation structure diagram

[0040] Figure 4 Position and attitude measurement and control unit III tensioning structure diagram

[0041] Figure 5 Zero-position calibration ray diagram

[0042] Figure 6 Compensation for Y-axis rotation and belt displacement diagram

[0043] Figure 7 Spatial structure diagram with mutually perpendicular X and Y axes

[0044] Figure 8 Flowchart of synchronous control for two rotational degrees of freedom

[0045] In the diagram, 1-front servo motor, 2-X-axis, 3-support platform bearing housing, 4-support platform, 5-left servo motor, 6-short shaft, 7-short shaft bearing housing, 8-bevel gear set, 9-Y-axis, 10-turntable, 11-probe, 12-turntable bearing housing, 13-belt device, 14-grating reading head, 15-linear grating ruler, 16-grating support, 17-sliding bearing housing, 18-support shaft, 19-slider, 20-slide rail, 21-tension spring, 22-limiter, 23-CCD support, 24-CCD camera. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] The working principle of this invention is as follows: Figure 1-7 As shown, a precision turntable device for synchronous control of two rotational degrees of freedom consists of three parts: an X-axis rotation control unit I, a Y-axis rotation control unit II, and a pose measurement and control unit III. The error compensation method and synchronous control method of this invention are illustrated in the following flowcharts. Figure 8 As shown.

[0048] Example 1: Adjust the probe 11 to rotate 20 degrees around the Y-axis 9.

[0049] The X-axis rotation control unit I includes a front servo motor 1, an X-axis 2, a support bearing seat 3, and a support platform 4;

[0050] The front servo motor 1 is connected to the X-axis 2 by a coupling. The X-axis 2 is fixedly supported by the support bearing seat 3 and is rigidly connected to the support platform 4.

[0051] The front servo motor 1, X-axis 2, support bearing seat 3 and support platform 4 control the rotation accuracy of probe 11 around X-axis 2. According to the required rotation amount of X-axis 2, the front servo motor 1 runs the corresponding number of pulses to drive X-axis 2 to rotate, thereby realizing the control of the rotation accuracy of probe 11 around X-axis 2.

[0052] The Y-axis rotation control unit II includes a left-side servo motor 5, a short shaft 6, a short shaft bearing seat 7, a bevel gear set 8, a Y-axis 9, a turntable 10, a probe 11, a turntable bearing seat 12, and a limiter 22;

[0053] The left servo motor 5 is bolted to the left side of the support platform 4. The left servo motor 5 is connected to the short shaft 6 by a coupling. The short shaft 6 is fixedly supported by the short shaft bearing seat 7. The short shaft bearing seat 7 is bolted to the turntable bearing seat 12.1. The short shaft 6 is keyed to the bevel gear set 8. The bevel gear set 8 is keyed to the Y-axis 9. The Y-axis 9 is rigidly connected to the turntable 10. The X-axis 2 and the Y-axis 9 are mutually perpendicular axes. The intersection of the two axes is located at the center of the turntable 10. The probe 11 is bolted to the turntable 10. The Y-axis 9 is fixedly supported by the turntable bearing seat 12. The turntable bearing seat 12 is bolted to the support platform 4. A limiter 22 is installed at the right end of the Y-axis 9.

[0054] The left servo motor 5, short shaft 6, bevel gear set 8, Y-axis 9, turntable 10 and turntable bearing seat 12 control the rotation accuracy of probe 11 around Y-axis 9. The left servo motor 5 runs the corresponding number of pulses to drive the short shaft 6 to rotate. The short shaft 6 drives the Y-axis 9 to rotate through the bevel gear set 8. Since the bevel gear set 8 has transmission error and backlash, it is necessary to compensate for the rotation amount to achieve the rotation accuracy control of probe 11 around Y-axis 9.

[0055] The limiter 22 is used to limit the rotation of the Y-axis 9, which controls the displacement of the belt 13.3. Limiting the rotation of the Y-axis 9 ensures that the grating reading head 14 can always be fixed on the upper side of the belt 13.3.

[0056] The pose measurement and control unit III includes a turntable 10, a probe 11, a turntable bearing seat 12, a belt device 13, a grating reading head 14, a linear grating ruler 15, a grating support 16, a sliding bearing seat 17, a support shaft 18, a slider 19, a slide rail 20, a tension spring 21, a CCD support 23, and a CCD camera 24.

[0057] The probe 11 is bolted to the turntable 10. A CCD camera 24 is placed directly behind the probe 11 and the turntable 10 via a CCD support 23. A belt assembly 13 is installed between turntable bearing housings 12.2 and 12.3. Pulleys 13.1 and 13.2 are respectively mounted on the Y-axis 9 and the support shaft 18. The belt 13.3 is connected to pulleys 13.1 and 13.2. The Y-axis 9 is fixedly supported by the turntable bearing housing 12, and the support shaft 18 is fixedly supported by a sliding bearing housing 17. The turntable bearing housing 12 is bolted to the support platform 4. Above, the sliding bearing seat 17 is fixed to the slider 19 by bolts. The grating support 16.1 is installed above the turntable bearing seat 12.2 and the turntable bearing seat 12.3 by bolts. The grating support 16.2 is installed above the sliding bearing seat 17.1 and the sliding bearing seat 17.2 by bolts. A linear grating ruler 15 is installed between the grating support 16.1 and the grating support 16.2. The grating reading head 14 is fixed to the belt 13.3. The slider 19 is stuck in the slide rail 20. The slide rail 20 is fixed to the support platform 4 by positioning plate and bolts. A tension spring 21 is installed on the inner side of the slide rail 20.

[0058] The probe 11 and CCD camera 24 are used to achieve zero-position calibration of the probe 11. The probe 11 emits a linear laser, which is received by the CCD camera 24. The position and length of the laser beam determine whether the probe 11 is at the initial position of the X-axis 2 and Y-axis 9. In imaging, when the linear laser is perpendicular to the horizontal line, the probe 11 reaches the initial position of the X-axis 2. When the linear laser is at its longest position on the vertical line, the probe 11 reaches the initial position of the Y-axis 9. When both are reached simultaneously, the probe 11 is at the zero position.

[0059] The left servo motor 5, belt 13.3, and grating reading head 14 use a compensation method to compensate for the rotation of the Y-axis 9. The grating reading head 14 can read the actual displacement data of the belt 13.3 when the Y-axis 9 rotates in real time. Then, the deviation value between the actual displacement data and the theoretical displacement data is converted into a pulse number to drive the left servo motor 5 to run, thereby compensating for the rotation of the Y-axis 9 and realizing the precision control of the rotation of the probe 11 around the Y-axis 9.

[0060] The tension spring 21 provides preload to the belt device 13. When the tension spring 21 is in a compressed state, it provides elastic force to the slider 19 to the outside of the support platform 4, so that the belt 13.3 is in a taut state.

[0061] Given that belt 13.3 has a circumference S around pulley 13.1 and the left servo motor 5 generates N pulses per revolution around Y-axis 9, and probe 11 is adjusted to zero, the left servo motor 5 generates B pulses to drive the short shaft 6 to rotate. B is calculated as follows:

[0062] B = N × (20 ÷ 360) (5)

[0063] Where B is the number of motor pulses and N is the number of motor pulses for one revolution of the Y-axis.

[0064] The short shaft 6 drives the Y-axis 9 to rotate via the bevel gear set 8. The probe 11 follows the rotation of the Y-axis 9. After the left servo motor 5 runs for B pulses, the grating reading head 14 reads the actual displacement of the belt 13.3 during the rotation of the Y-axis 9, and then converts the displacement deviation value ΔL into the number of motor pulses N. 补 ΔL and N 补 Calculation as follows

[0065] ΔL=L 实 -L 理 (6)

[0066] N 补 =N×(ΔL÷S) (7)

[0067] Among them, L 实 To enable the grating reading head to read the actual belt displacement in real time, L 理 Let N be the theoretical displacement of the belt, ΔL be the belt displacement deviation, S be the belt circumference around the pulley, and N be the displacement of the belt. 补 This is the number of pulses used to compensate for motor errors.

[0068] Left servo motor 5 operates N 补 The number of motor pulses is used to compensate for the rotation of the Y-axis (9). After the initial compensation of the rotation, the actual displacement of the belt (13.3) is read again, and the deviation value ΔL is converted into the number of pulses N. 补 Run the left servo motor 5 repeatedly until ΔL = 0, thus rotating the probe 11 20 degrees around the Y-axis.

[0069] Example 2: Adjust the probe 11 to rotate 20 degrees around the Y-axis 9 and 40 degrees around the X-axis 2.

[0070] Given that the number of pulses generated during one revolution of X-axis 2 is N, and using CCD camera 24 to adjust probe 11 to zero, as shown in Example 1, while adjusting probe 11 to rotate 20 degrees around Y-axis 9, the number of pulses generated by front servo motor 1 is A. A is calculated as follows:

[0071] A = N × (40 ÷ 360) (8)

[0072] Where A is the number of motor pulses and N is the number of motor pulses for one revolution of the X-axis.

[0073] The probe 11 is made to rotate synchronously around the X-axis 2 and the Y-axis 9, and finally the probe 11 rotates 20 degrees around the Y-axis 9 and 40 degrees around the X-axis 2.

Claims

1. A precision turntable device for synchronous control of two rotational degrees of freedom, characterized in that, It consists of three parts: X-axis rotation control unit I, Y-axis rotation control unit II, and posture measurement and control unit III; The X-axis rotation control unit I includes a front servo motor (1), an X-axis (2), a support bearing seat (3), and a support platform (4); The front servo motor (1) is connected to the X-axis (2) by a coupling. The X-axis (2) is fixedly supported by the support bearing seat (3) and is rigidly connected to the support platform (4). The rotation accuracy of the probe (11) around the X-axis (2) is controlled by the front servo motor (1), the X-axis (2), the support bearing seat (3) and the support (4). According to the required rotation amount of the X-axis (2), the front servo motor (1) runs the corresponding number of pulses to drive the X-axis (2) to rotate, thereby realizing the rotation accuracy control of the probe (11) around the X-axis (2). The Y-axis rotation control unit II includes a left servo motor (5), a short shaft (6), a short shaft bearing seat (7), a bevel gear set (8), a Y-axis (9), a turntable (10), a probe (11), a turntable bearing seat (12), and a limiter (22); The left servo motor (5) is bolted to the left side of the support platform (4). The left servo motor (5) is connected to the short shaft (6) by a coupling. The short shaft (6) is fixedly supported by the short shaft bearing seat (7). The short shaft bearing seat (7) is bolted to the first turntable bearing seat (12.1). The short shaft (6) is keyed to the bevel gear set (8). The bevel gear set (8) is keyed to the Y-axis (9). The Y-axis (9) is rigidly connected to the turntable (10). The X-axis (2) and the Y-axis (9) are mutually perpendicular axes. The intersection of the two axes is located at the center of the turntable (10). The probe (11) is bolted to the turntable (10). The Y-axis (9) is fixedly supported by the turntable bearing seat (12). The turntable bearing seat (12) is bolted to the support platform (4). A limiter (22) is installed at the right end of the Y-axis (9). The rotation accuracy of the probe (11) around the Y-axis (9) is controlled by the left servo motor (5), short shaft (6), bevel gear set (8), Y-axis (9), turntable (10) and turntable bearing seat (12). The left servo motor (5) runs the corresponding number of pulses to drive the short shaft (6) to rotate. The short shaft (6) drives the Y-axis (9) to rotate through the bevel gear set (8). Since the bevel gear set (8) has transmission error and backlash, it is necessary to compensate for the rotation amount to achieve the rotation accuracy control of the probe (11) around the Y-axis (9). The limiter (22) is used to limit the rotation of the Y-axis (9), which controls the displacement of the belt (13.3). Limiting the rotation of the Y-axis (9) ensures that the grating reading head (14) is always fixed on the upper side of the belt (13.3). The pose measurement and control unit III includes a turntable (10), a probe (11), a turntable bearing seat (12), a belt device (13), a grating reading head (14), a linear grating ruler (15), a grating support (16), a sliding bearing seat (17), a support shaft (18), a slider (19), a slide rail (20), a tension spring (21), a CCD support (23), and a CCD camera (24). The probe (11) is bolted to the turntable (10). A CCD camera (24) is placed directly behind the probe (11) and the turntable (10) via a CCD support (23). A belt assembly (13) is installed between the second turntable bearing housing (12.2) and the third turntable bearing housing (12.3). The first pulley (13.1) and the second pulley (13.2) are respectively mounted on the Y-axis (9) and the support shaft (18). The belt (13.3) is connected to the first pulley (13.1) and the second pulley (13.2). The Y-axis (9) is fixedly supported by the turntable bearing housing (12). The support shaft (18) is fixedly supported by the sliding bearing housing (17). The turntable bearing housing (12) is bolted to the support platform (4). On the slide (19), the sliding bearing seat (17) is fixed to the slider (19) by bolts. The first grating support (16.1) is installed above the second turntable bearing seat (12.2) and the third turntable bearing seat (12.3) by bolts. The second grating support (16.2) is installed above the first sliding bearing seat (17.1) and the second sliding bearing seat (17.2) by bolts. A linear grating ruler (15) is installed between the first grating support (16.1) and the second grating support (16.2). The grating reading head (14) is fixed on the belt (13.3). The slider (19) is stuck in the slide (20). The slide (20) is fixed to the support platform (4) by positioning plate and bolts. A tension spring (21) is installed on the inner side of the slide (20). The zero-position calibration function of the probe (11) is realized by the probe (11) and the CCD camera (24). The probe (11) emits a linear laser which is received by the CCD camera (24). The position and length of the light are used to determine whether the probe (11) is at the initial position of the X-axis (2) and Y-axis (9). In imaging, when the linear laser is perpendicular to the horizontal line, the probe (11) reaches the initial position of the X-axis (2). When the linear laser is at its longest position on the vertical line, the probe (11) reaches the initial position of the Y-axis (9). When both are reached at the same time, the probe (11) is at the zero position. The Y-axis (9) rotation compensation is achieved by the left servo motor (5), belt (13.3) and grating reading head (14) using a compensation method. The grating reading head (14) can read the actual displacement data of the belt (13.3) when the Y-axis (9) rotates in real time. Then, the deviation value between the actual displacement data and the theoretical displacement data is converted into the number of pulses to drive the left servo motor (5) to run, and to compensate for the Y-axis (9) rotation, so as to realize the accuracy control of the probe (11) rotation around the Y-axis (9). The posture measurement and control unit III is equipped with a tensioning structure to provide pre-tension for the belt device (13) and realize the movement of the belt (13.3) parallel to the support platform (4).

2. An error compensation method for a precision turntable device with synchronous control of two rotational degrees of freedom as described in claim 1, characterized in that, The calculation of the compensation rotation amount is performed according to the following steps: 1) Calibrate the initial position by using a CCD camera to adjust the probe to zero; 2) Coarsely adjust the Y-axis rotation. In order to accurately control the Y-axis rotation to b, the rotation of the Y-axis is converted into the linear displacement of the belt using belt drive. The motor runs for B pulses to initially obtain the Y-axis rotation b0. B=N×(b÷360) (1) Where b physically represents the amount of rotation around the Y-axis, B is the number of motor pulses, N is the number of motor pulses for one revolution of the Y-axis, and b0 is the coarse adjustment rotation amount; 3) Initial compensation for Y-axis rotation, converting the belt displacement deviation value ΔL into the number of motor pulses N. 补 The running motor compensates for the Y-axis rotation. ΔL=L 实 -L 理 (2) L 理 =S×(b÷360) (3) N 补 =N×(ΔL÷S) (4) Where S is the circumference of the belt around the pulley, and N 补 L is the number of operating pulses for motor error compensation. 实 To enable the grating reading head to read the actual belt displacement in real time, L 理 ΔL is the theoretical displacement of the belt, and ΔL is the belt displacement deviation. 4) Fine-tune the Y-axis rotation. After the initial compensation of the Y-axis rotation, read L again. 实 We obtain ΔL, and use ΔL to convert it into the number of pulses to run the motor to compensate for the rotation amount. We repeat step 3) multiple times until ΔL = 0, so that the rotation amount of the Y-axis is controlled to be b, thus achieving precise control of the rotation amount of the Y-axis.

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