A four-degree-of-freedom vibration isolation platform based on Stewart-derived structure

Abstract

The present invention provides a four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure, comprising a top plate, legs, and a base. The top plate and the base have the same structural dimensions and are both triangles with three corners cut off. Six legs are installed between the top plate and the base, three of which are vertically installed between the three corners of the top plate and the base and are connected to the top plate and the base respectively through Hooke's hinges, and the other three legs are installed between the three edges on the same side of the top plate and the base, with an angle of 45° between the top plate and the base, and are connected to the top plate and the base respectively through ball joints. The system of the present invention can achieve vibration control of four degrees of freedom (up and down, front and back, left and right, and rotation around the z-axis) with a range of 0.1Hz to 200Hz. It has a wide vibration isolation bandwidth and precise positioning. It can be adapted to different types of precision instruments and has a wide range of applications and strong versatility.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor dedicated devices, in particular to a four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure. Background Art

[0002] At present, the semiconductor industry is developing rapidly. The precision requirements of semiconductor production equipment are getting higher and higher. The equipment is becoming more and more sensitive to environmental requirements such as micro-vibration. A small amount of micro-vibration will reduce the output yield of the equipment or even cause the equipment to malfunction. Therefore, isolation of micro-vibration is becoming more and more important.

[0003] The Stewart platform parallel mechanism, with its high stiffness, strong load-bearing capacity, and lack of cumulative positional errors, complements serial mechanisms in applications and has become a research hotspot in space mechanics. Currently, Stewart platform parallel mechanisms are widely used in industries such as aviation, aerospace, submarine operations, underground mining, and manufacturing and assembly. Traditional Stewart platforms use hydraulic cylinders to drive their legs, making them bulky, inaccurate, and subject to limitations. To improve positioning accuracy, Stewart platforms using linear motors and piezoelectric actuators have emerged. While these improvements have resulted in significantly reduced load-bearing capacity, there are also Stewart platforms using servo motors, which offer better positioning accuracy than hydraulic cylinders, but they still cannot meet the requirements for micro-vibration control. Furthermore, traditional Stewart platform systems have limited stiffness and are limited in their application, resulting in a narrow range of applications and poor versatility. Summary of the Invention

[0004] The object of the present invention is to provide a four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure to solve the problems existing in the above-mentioned background technology.

[0005] The technical solution of the present invention is implemented as follows: a four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure, comprising a top plate, legs and a base, wherein the top plate and the base have the same structural dimensions and are both triangles with three corners cut off, and six legs are installed between the top plate and the base, three of the legs are respectively installed vertically between the three corners of the top plate and the base and are respectively connected to the top plate and the base through Hooke's hinges, and the other three legs are respectively installed between the three sides on the same side of the top plate and the base, with an angle of 45° between the top plate and the base and are respectively connected to the top plate and the base through ball joints, and the legs include a shell, and a servo motor is installed on the inner side of the bottom of the shell. The top of the servo motor is connected to the screw, and a ball screw nut is mounted on the outside of the screw, and a first guide rod is mounted on the top of the ball screw nut and the outside of the screw, a permanent magnet is installed on the top of the first guide rod, a second guide rod is installed vertically above the permanent magnet, an electromagnet is installed at the bottom of the second guide rod, an air spring is installed at the bottom of the servo motor, a support rod is installed vertically in the middle of the bottom of the air spring, a bearing is installed on the lower part of the screw near the servo motor and on the inside of the shell, a guide rail is installed on the top of the shell, an air intake pipe is opened at the bottom of the air spring, a pneumatic valve is installed on the air intake pipe, an acceleration sensor is installed on the second guide rod, and a controller is also installed on the top of the base.

[0006] Furthermore, the top plate and the base are both made of stainless steel plates.

[0007] Furthermore, the second guide rod passes through the guide rail and is slidably connected to the guide rail.

[0008] Furthermore, the controller is connected to the servo motor, the electromagnet and the acceleration sensor through cables.

[0009] Furthermore, the guide rail is a ceramic guide rail, which not only has a guiding function but also can prevent the magnetic field in the support legs from interfering with the operation of the precision instrument above the top plate.

[0010] The beneficial effects of the present invention are:

[0011] The present invention can change the system stiffness to meet the requirements of different precision instruments by changing the pressure of the air spring according to the different vibration properties of the precision instruments.

[0012] The present invention is based on the Stewart structure. By adjusting three of the legs to a vertical direction and connecting them to the top plate and base through Hooke hinges, its load-bearing capacity is improved. At the same time, the load-bearing structure composed of a servo motor and a ball screw is adopted to meet the load-bearing requirement of 500kg.

[0013] The present invention changes the rotary drive into linear motion through the combination of a servo motor and a ball screw, thereby meeting the vibration isolation of high-frequency vibration sources of 50Hz to 200Hz, and realizing the vibration isolation of low-frequency vibration sources of 0.1Hz to 50Hz through magnetic drive. By controlling the direction of the electromagnet current to change the attractive and repulsive forces with the permanent magnet, the driving mode can be changed for high-frequency and low-frequency vibration sources.

[0014] The three legs of the system of the present invention are vertically connected to the top plate and the base through Hooke's joints, and the other three legs are connected to the top plate and the base at a 45° angle through ball joints. It can achieve vibration control of 0.1Hz~200Hz in four degrees of freedom: up and down, front and back, left and right, and rotation around the z-axis. It has a wide vibration isolation bandwidth and precise positioning. It can be adapted to different models of precision instruments, has a wide range of applications, and is highly versatile. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention.

[0016] Figure 2 Schematic diagram of the structure of the support legs.

[0017] In the figure, 1-top plate, 2-support leg, 201-housing, 202-servo motor, 203-screw, 204-ball screw nut, 205-first guide rod, 206-permanent magnet, 207-second guide rod, 208-electromagnet, 209-air spring, 210-support rod, 211-bearing, 212-guide rail, 213-intake pipe, 214 pneumatic valve, 3-base, 4-acceleration sensor, 5-controller, 6-Hook's hinge, 7-ball joint. Implementation Method

[0018] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] like Figure 1-2As shown, a four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure includes a top plate 1, legs 2 and a base 3. The top plate 1 and the base 3 have the same structural dimensions and are both triangles with three corners cut off. The six legs 2 are installed between the top plate 1 and the base 3. Three of the legs 2 are vertically installed between the three corners of the top plate 1 and the base 3 and are connected to the top plate 1 and the base 3 respectively through Hooke's hinges 6. The other three legs 2 are installed between the three edges on the same side of the top plate 1 and the base 3, with an angle of 45° between the top plate 1 and the base 3 and are connected to the top plate 1 and the base 3 respectively through ball joints 7. The legs 2 include a shell 201, a servo motor 202 is installed on the inner side of the bottom of the shell 201, the top of the servo motor 202 is connected to the screw 203, and a ball screw is sleeved on the outer side of the screw 203. Nut 204, a first guide rod 205 is mounted on the top of the ball screw nut 204 and the outside of the screw 203, a permanent magnet 206 is installed on the top of the first guide rod 205, a second guide rod 207 is installed vertically above the permanent magnet 206, an electromagnet 208 is installed at the bottom of the second guide rod 207, an air spring 209 is installed at the bottom of the servo motor 202, a support rod 210 is installed vertically in the middle of the bottom of the air spring 209, a bearing 211 is installed on the lower part of the screw 203 near the servo motor 202 and the inside of the housing 202, a guide rail 212 is installed on the top of the housing 201, an air intake pipe 213 is opened below one side of the air spring 209, a pneumatic valve 214 is installed on the air intake pipe 213, an acceleration sensor 4 is installed on the second guide rod 207, and a controller 5 is also installed on the top of the base 3.

[0020] The top plate 1 and the base 3 are both made of stainless steel plates.

[0021] The second guide rod 207 passes through the guide rail 212 and is slidably connected to the guide rail 212 .

[0022] The controller 5 is connected to the servo motor 202 , the electromagnet 208 and the acceleration sensor 4 via cables.

[0023] The guide rail 212 is a ceramic guide rail, which not only has a guiding function but also can prevent the magnetic field in the support leg 2 from interfering with the operation of the precision instrument above the top plate 1.

[0024] During installation, the precision instrument is installed on the top plate 1. According to the requirements of the precision instrument, the air pressure of the air spring 209 is adjusted by controlling the pneumatic valve 214 to adjust the stiffness of the entire system to meet the load-bearing and stiffness requirements of the top precision instrument.

[0025] During operation, the precision instrument generates vibrations, which are then collected by the acceleration sensor 4 and transmitted to the controller 5. When the vibration source is high-frequency, the controller 5 first controls the direction and magnitude of the current in the electromagnet 208, causing an attractive force to appear between the electromagnet 208 and the permanent magnet 206. At this point, the first guide rod 205 and the second guide rod 207 are tightly connected together, becoming one. The controller 5 then controls the servo motor 202 to drive, transforming the rotational drive into a linear drive through the cooperation of the lead screw 203 and the ball screw nut 204. This then drives the first guide rod 205 and the second guide rod 207 to extend and retract, achieving high-frequency vibration isolation. When the vibration source is low-frequency, the controller 5 stops the servo motor 202 and controls the direction and magnitude of the current in the electromagnet 208, causing a repulsive force to appear between the electromagnet 208 and the permanent magnet 206. This then drives the second guide rod 207 to extend and retract, achieving low-frequency vibration isolation. Furthermore, the six legs 2 move independently, achieving vibration isolation in four degrees of freedom: up and down, front and back, left and right, and rotation about the z-axis.

[0026] 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, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure, comprising a top plate, legs, and a base, characterized in that: The top plate and the base have the same structural dimensions, both being triangles with three corners cut off. There are six legs installed between the top plate and the base, three of which are vertically installed between the three corners of the top plate and the base and are connected to the top plate and the base respectively through Hooke's hinges, and the other three of which are installed between the three sides on the same side of the top plate and the base, with an angle of 45° between the top plate and the base and are connected to the top plate and the base respectively through ball joints. The legs include a housing, a servo motor is installed on the inner side of the bottom of the housing, the top of the servo motor is connected to the screw, and a ball screw nut is mounted on the outer side of the screw. A first guide rod is mounted on the top of the ball screw nut and the outside of the screw, a permanent magnet is installed on the top of the first guide rod, a second guide rod is installed vertically above the permanent magnet, an electromagnet is installed at the bottom of the second guide rod, an air spring is installed at the bottom of the servo motor, a support rod is installed vertically in the middle of the bottom of the air spring, a bearing is installed at the lower part of the screw near the servo motor and on the inside of the outer shell, a guide rail is installed on the top of the outer shell, an air intake pipe is opened below one side of the air spring, a pneumatic valve is installed on the air intake pipe, an acceleration sensor is installed on the second guide rod, and a controller is also installed on the top of the base.

2. The four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure according to claim 1, characterized in that: The top plate and the base are both made of stainless steel plates.

3. The four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure according to claim 1, characterized in that: The second guide rod passes through the guide rail and is slidably connected to the guide rail.

4. The four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure according to claim 1, characterized in that: The controller is connected with the servo motor, the electromagnet and the acceleration sensor through cables.

5. The four-degree-of-freedom vibration isolation platform based on a Stewart-derived structure according to claim 1, characterized in that: The guide rail is a ceramic guide rail, which not only has a guiding function but also can prevent the magnetic field in the support legs from interfering with the operation of the precision instruments above the top plate.

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