Ultrasonic motor driven turntable

Abstract

An ultrasonic motor-driven turntable includes a base, a locking nut, a preload nut, a disc spring, an ultrasonic motor rotor assembly, an ultrasonic motor stator assembly, a shaft system assembly, a high-precision angle encoder, a spline coupling, an annular nut, and a turntable bottom cover. The high-precision servo turntable uses an ultrasonic motor as the drive device, the shaft system assembly as the motion carrier, and the high-precision angle encoder as the sensor to form a closed-loop feedback system, collaboratively outputting precise angular displacement. This invention's high-precision turntable, driven by an ultrasonic motor, features high positioning accuracy, fast response speed, and large holding torque. The shaft system assembly employs a back-to-back high-precision angular contact bearing design, enabling the shaft system to withstand axial and radial loads. Furthermore, a self-lubricating bushing coupling design between the shaft system assembly and the ultrasonic motor rotor provides buffering and vibration absorption in both axial and radial directions, improving shaft rotation accuracy, ensuring shaft stability, and extending the turntable's lifespan.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology and relates to a high-precision turntable based on ultrasonic motor drive. Background Technology

[0002] Turntables are widely used in the field of space laser communication. As a coarse tracking mechanism in laser communication, the positioning accuracy, response speed, and rotational speed stability of the turntable have a significant impact on the establishment of laser communication links. Currently, traditional laser communication coarse tracking mechanisms use electromagnetic motors for driving, with gears and other reduction transmissions between the motor and the shaft system. The movement of these components generates backlash, hysteresis, and vibration, making it difficult to achieve high precision, and the reducers also occupy a large amount of space.

[0003] Ultrasonic motors utilize the inverse piezoelectric effect of piezoelectric ceramics and ultrasonic vibration to generate motion and torque. The microscopic deformation of the material is amplified through mechanical resonance and frictional coupling, transforming it into macroscopic rotor motion, which serves as power output to drive other loads. Compared to traditional motors, ultrasonic motors offer advantages such as faster response speed, higher positioning accuracy, and higher displacement resolution. Therefore, high-precision turntables driven by ultrasonic motors are becoming a development trend.

[0004] Prior Art 1: Invention Title: A Two-Dimensional Precision Turntable Driven by an Ultrasonic Motor, Publication No. CN114576507B. This invention uses the same principle for both position and pitch axis driving, employing a hollow ultrasonic motor-driven two-dimensional precision turntable and forming a closed-loop feedback system using a high-precision encoder as a sensor. In this invention, the ultrasonic motor rotor and shaft are directly rigidly connected by screws, lacking a buffer and vibration-damping design. During rotor rotation, vibration affects the bearing's rotational accuracy. Furthermore, the preload of the ultrasonic motor is adjusted by changing the spring length through the nut position. The spring pressure is first applied to the bearing and then transmitted to the ultrasonic motor stator. Since the spring is a constant-stiffness elastic element, changing its length results in varying preload on the ultrasonic motor stator, affecting the motor's positioning accuracy and rotational stability. In this invention, a limiting bracket is installed on the stator, and a spring and a steel ball are installed on the bracket to limit the movement. The limiting bracket is only designed as a single one, which will cause uneven force on the stator and the stator may wobble during operation. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a high-precision turntable based on ultrasonic motor drive, which can output precise angular displacement and features fast response speed, large holding torque, and high stability.

[0006] This invention is implemented as follows: a high-precision turntable driven by an ultrasonic motor includes a base, a locking nut, a preload nut, a disc spring, an ultrasonic motor rotor assembly, an ultrasonic motor stator assembly, a shaft system assembly, a high-precision angle encoder, a spline coupling, an annular nut, and a turntable bottom cover plate. The ultrasonic motor rotor assembly includes an ultrasonic motor rotor, a self-lubricating bushing coupling, and a circular washer; the ultrasonic motor stator assembly includes a piezoelectric stator shaft, a self-lubricating straight sleeve bearing, an ultrasonic motor stator, a locating pin, and screws; the shaft system assembly includes a turntable output shaft, a bearing sleeve, a high-precision angular contact bearing, a bearing outer ring retainer, and a bearing inner ring retainer.

[0007] Preferably, the ultrasonic motor rotor assembly and the shaft assembly are connected by an interference fit via a self-lubricating bushing coupling;

[0008] Preferably, the preload between the ultrasonic motor rotor assembly and the ultrasonic motor stator assembly is achieved by changing the shape of the disc spring. The preload nut is positioned at different locations on the turntable output shaft to apply a certain pressure to the disc spring, which is then applied to the ultrasonic motor rotor assembly.

[0009] Preferably, the ultrasonic motor stator assembly is connected to the base via four symmetrically distributed piezoelectric stator shafts and a self-lubricating straight sleeve bearing with clearance fit.

[0010] Preferably, the turntable output shaft adopts a stepped shaft design and is designed with an interference fit with the ultrasonic motor rotor assembly. It has four corresponding planes as positioning surfaces, and provides axial and radial friction forces. The turntable output shaft is connected to the high-precision angle encoder by a spline coupling and is tightened and fixed with a ring nut.

[0011] Preferably, the self-lubricating bushing coupling adopts a wire-cut groove design and is made of polyoxymethylene.

[0012] Compared with the prior art, the beneficial effects of this invention are as follows:

[0013] 1) The ultrasonic motor rotor assembly and shaft assembly are connected by an interference fit of a self-lubricating bushing coupling, which has a self-lubricating effect and can play a certain role in buffering and vibration absorption during movement, which can play a huge role in the stability and life of the turntable.

[0014] 2) The length of the disc spring is changed by using a double nut design (locking nut and preload nut). The pressure generated by the deformation of the disc spring is applied to the ultrasonic motor rotor assembly. The double nut design ensures the nuts are locked in place, increasing reliability. The disc spring has variable stiffness characteristics. When the disc spring deformation reaches the zero stiffness range of its operating range, the disc spring's efficiency is optimal, and the preload applied to the ultrasonic motor is also optimal, maximizing the ultrasonic motor's working efficiency.

[0015] 3) The four stator shafts are symmetrically distributed and fitted with self-lubricating straight sleeve bearings on the base. The symmetrical distribution ensures that the stator is subjected to uniform force. At the same time, the use of self-lubricating straight sleeve bearings can buffer and absorb vibration in both the axial and radial directions. This ensures that the position of the stator is absolutely fixed and there is no risk of rigid vibration. This has a certain effect on the stability and accuracy of the turntable. Attached Figure Description

[0016] Figure 1 This is an isometric view of a high-precision turntable driven by an ultrasonic motor, as described in an embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional view of a high-precision turntable driven by an ultrasonic motor in an embodiment of the present invention.

[0018] Figure 3 This is a cross-sectional view of the ultrasonic motor rotor assembly in an embodiment of the present invention.

[0019] Figure 4 This is a cross-sectional view of the ultrasonic motor stator assembly in an embodiment of the present invention.

[0020] Figure 5 This is a cross-sectional view of the turntable shaft system assembly in an embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram of the interference fit assembly of the ultrasonic motor rotor assembly in an embodiment of the present invention.

[0022] Figure 7 This is an isometric view of the ultrasonic motor stator assembly in an embodiment of the present invention.

[0023] Numbering in the diagram: 1-Base; 2-Locking nut; 3-Preload nut; 4-Disc spring; 5-Ultrasonic motor rotor assembly; 6-Ultrasonic motor stator assembly; 7-Shaft assembly; 8-High-precision angle encoder; 9-Spline coupling; 10-Ring nut; 11-Turntable bottom cover plate; 12-Ultrasonic motor rotor; 13-Self-lubricating bushing coupling; 14-Circular washer; 15-Piezoelectric stator shaft; 16-Self-lubricating straight sleeve bearing; 17-Ultrasonic motor stator; 18-Positioning pin; 19-Screw; 20-Turntable output shaft; 21-Bearing sleeve; 22-High-precision angular contact bearing; 23-Bearing outer ring pressure ring; 24-Bearing inner ring pressure ring. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 , Figure 2 As shown, the present invention provides a high-precision turntable based on ultrasonic motor drive, including a base 1, a locking nut 2, a preload nut 3, a disc spring 4, an ultrasonic motor rotor assembly 5, an ultrasonic motor stator assembly 6, a shaft assembly 7, a high-precision angle encoder 8, a spline coupling 9, an annular nut 10, and a turntable bottom cover plate 11.

[0027] The structural diagram of ultrasonic motor rotor assembly 5 is shown below. Figure 3 As shown, it includes an ultrasonic motor rotor 12, a self-lubricating bushing coupling 13, and a circular shim 14. The ultrasonic motor rotor 12 and the self-lubricating bushing coupling 13 are connected by an interference fit and are fully positioned by four tangent planes on the inner hole of the ultrasonic motor rotor 12. The circular shim 14 and the self-lubricating bushing coupling 13 are connected by a clearance fit.

[0028] The structural diagram of ultrasonic motor stator assembly 6 is shown below. Figure 4 As shown, the system includes a piezoelectric stator shaft 15, a self-lubricating straight sleeve bearing 16, an ultrasonic motor stator 17, locating pins 18, and screws 19. The ultrasonic motor stator 17 is connected and fixed to the piezoelectric stator shaft 15 by four locating pins 18 and four screws 19. The inner hole of the self-lubricating straight sleeve bearing 16 is connected to the four piezoelectric stator shafts 15 by a clearance fit, and the outer circle of the four self-lubricating straight sleeve bearings 16 is connected to the four inner holes on the base 1 by a clearance fit.

[0029] The structural schematic diagram of the turntable shaft system assembly 7 is shown below. Figure 5 As shown, the assembly includes a turntable output shaft 20, a bearing sleeve 21, a high-precision angular contact bearing 22, a bearing outer ring retainer 23, and a bearing inner ring retainer 24. The turntable output shaft 20 is connected to the inner rings of a pair of high-precision angular contact bearings 22 by a clearance fit and is completely fixed together by the bearing inner ring retainer 24 and screws. The outer rings of the pair of high-precision angular contact bearings 22 are connected to the bearing sleeve 21 by a clearance fit and are completely fixed together by the bearing outer ring retainer 23 and screws.

[0030] The bearing sleeve 21 on the shaft assembly 7 is connected to the base 1 by screws. It is necessary to ensure the coaxiality of the output shaft 20 and the central shaft of the base 1. The shoulder of the threaded end of the output shaft 20 is connected to the self-lubricating bushing coupling 13 on the ultrasonic motor rotor assembly 5 by an interference fit. The disc spring 4 is located between the preload nut 3 and the circular washer 14. The preload nut 3 and the output shaft 20 are designed with a threaded fit. By changing the position of the preload nut 3 on the output shaft 20, the disc spring 4 can be deformed. The pressure generated by the deformation of the disc spring 4 is applied to the ultrasonic motor rotor assembly 5, thereby applying a preload force between the stator and the rotor of the ultrasonic motor.

[0031] Locking nut 2 is screwed onto output shaft 20 to prevent preload nut 3 from loosening. Turntable bottom cover plate 11 is connected and fixed to base 1 by screws through circumferentially distributed through holes. The inner ring of high-precision angle encoder 8 is connected to turntable output shaft 20 through spline coupling 9 and fixed by ring nut 10. At the same time, the outer ring of high-precision angle encoder 8 is connected and fixed to base 1 by screws through circumferentially distributed through holes.

[0032] The present invention provides a high-precision turntable based on ultrasonic motor drive, the working process of which is as follows:

[0033] On the output shaft of a high-precision turntable driven by an ultrasonic motor, a load requiring high-precision angular displacement, such as a laser communication optical receiving system, is connected by screws. When the laser communication system requires the high-precision turntable to output an angle α (0° < α < 360°), the system controller issues a specific position command (output angular displacement α) to the ultrasonic motor. After the ultrasonic motor rotor receives the drive voltage signal, it drives the shaft assembly, the high-precision angle encoder connected to the shaft assembly, and the laser communication optical receiving system. At this time, the high-precision angle encoder will feed back an actual angular displacement value α1 to the controller. The controller will calculate a difference Δ = α1 - α between the actual angular displacement α1 and the input angular displacement α, and convert this difference into a drive voltage signal for the ultrasonic motor, which is then input to the ultrasonic motor drive end to complete one closed-loop control. This process is repeated several times until the actual value measured by the high-precision angle encoder is within the allowable accuracy range, thus completing one high-precision angular displacement output.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision turntable based on ultrasonic motor drive, characterized in that, Includes base (1), locking nut (2), preload nut (3), disc spring (4), ultrasonic motor rotor assembly (5), ultrasonic motor stator assembly (6), shaft assembly (7), angle encoder (8), spline coupling (9) and ring nut (10); The shaft assembly (7) includes a turntable output shaft (20), a bearing sleeve (21), and a pair of angular contact bearings (22); the inner rings of the turntable output shaft (20) and the pair of angular contact bearings (22) are connected by a clearance fit, and the outer rings of the pair of angular contact bearings (22) are connected to the bearing sleeve (21) by a clearance fit; the bearing sleeve (21) is connected to the base (1) and ensures the coaxiality of the turntable output shaft (20) and the central axis of the base (1); The ultrasonic motor rotor assembly (5) includes an ultrasonic motor rotor (12) and a self-lubricating bushing coupling (13); the ultrasonic motor rotor (12) and the self-lubricating bushing coupling (13) are interference-fitted, and the inner hole of the self-lubricating bushing coupling (13) is interference-fitted with the turntable output shaft (20); the ultrasonic motor rotor assembly (5) and the shaft system assembly (7) are clearance-fitted through the self-lubricating bushing coupling (13); The ultrasonic motor stator assembly (6) includes a piezoelectric stator shaft (15), a self-lubricating straight sleeve bearing (16), an ultrasonic motor stator (17), a positioning pin (18), and a screw (19); the ultrasonic motor stator (17) and the four circumferentially distributed piezoelectric stator shafts (15) are positioned by the positioning pin (18) and fixed by the screw (19); the piezoelectric stator shafts (15) are mounted on the base (1) by the self-lubricating straight sleeve bearing (16); The preload nut (3) is threadedly engaged with the turntable output shaft (20). By changing the position of the preload nut (3) on the turntable output shaft (20), the disc spring (4) is deformed. The pressure generated by the deformation of the disc spring (4) is applied to the ultrasonic motor rotor assembly (5), thereby applying a preload force between the ultrasonic motor stator and rotor. The locking nut (2) is screwed onto the turntable output shaft (20). The inner ring of the angle encoder (8) is connected to the turntable output shaft (20) through a spline coupling (9) and fixed by an annular nut (10). The outer ring of the angle encoder (8) is connected to the base by screws through circumferentially distributed through holes. The ultrasonic motor stator assembly (6) is connected to the base (1) by four symmetrically distributed piezoelectric stator shafts (15) and a self-lubricating straight sleeve bearing (16) through an interference fit. The self-lubricating bushing coupling (13) adopts a wire-cut groove design and is made of polyoxymethylene.

2. The high-precision turntable based on ultrasonic motor drive according to claim 1, characterized in that, The magnitude of the preload between the ultrasonic motor rotor assembly (5) and the ultrasonic motor stator assembly (6) is achieved by changing the shape of the disc spring (4). The preload nut (3) is positioned at different locations on the turntable output shaft (20) to apply a certain pressure to the disc spring (4), which is then applied to the ultrasonic motor rotor assembly (5).

3. The high-precision turntable based on ultrasonic motor drive according to claim 1, characterized in that, The turntable output shaft (20) adopts a stepped shaft design and provides radial friction.

4. The high-precision turntable based on ultrasonic motor drive according to claim 1, characterized in that, The ultrasonic motor rotor assembly (5) also includes a circular washer (14), which is connected to the self-lubricating bushing coupling (13) by a clearance fit. The disc spring (4) is located between the preload nut (3) and the circular washer (14).

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