CN101290808B - A three-degree-of-freedom ultra-precision micro-motion table - Google Patents

Abstract

The invention discloses a three-degree-of-freedom ultra-precision micro-motion workbench. The movement of the workbench in the X, Y and θ directions is provided by four linear motors vertically arranged on the outer frame and the inner frame of the micro-motion table. The stator is installed on the inner side of the outer frame, and the linear motor stator is installed on the outer side of the inner frame. The outer frame is vertically supported by four circular air bearings installed at the four corners of the bottom of the outer frame, and the inner frame is vertically supported by annular air bearings and circular vacuum preloaded suction cups respectively. The position information of the micro-movement stage is measured by the first and second planes installed vertically on the object platform with laser interferometer. A three-degree-of-freedom ultra-precision micro-motion worktable proposed by the present invention can realize large load, large inertia, and high-precision motion. The positioning accuracy in the Y direction can reach 5nm, and the rotation angle accuracy is 0.25μrad. The invention can be used in photolithography machines, ultra-precision numerical control machine tools, biological chip scanners and other equipment.

Description

A three-degree-of-freedom ultra-precision micro-motion table

technical field

The invention relates to a precision device, specifically a three-degree-of-freedom ultra-precision micro-motion workbench, which can be applied to high-precision system technical fields such as photolithography equipment, precision machine tools, and precision measurement equipment, and can also be used in bioengineering equipment.

Background technique

The nano-scale micro-motion worktable provides a precise positioning and fast-moving object-carrying platform for nano-manufacturing and measurement. With the development of ultra-precision machining and measurement equipment such as integrated circuit manufacturing, the demand for nano-scale micro-motion workbench is increasing, and the performance of the workbench is also very high. At present, there are PI, Anord, and Feinmess companies in the international market that can manufacture micro-motion stages. Among them, the micro-motion stage manufactured by PI company is driven by a planar motor, which can achieve nanometer precision, but can only bear a load of about 235g; The micro-motion stage made by Feinmess can only perform short-stroke and low-precision micro-motion, but the precision is low and can only reach the micron level; High-speed, high-precision occasions.

The Chinese patent document with the publication number CN1921026A and the publication date of February 28, 2007 provides a "X-Y-θ three-degree-of-freedom micro-motion platform", which realizes three-degree-of-freedom movement and control by a secondary mechanical structure. The elastic support mechanical structure realizes three-axis linkage, and is driven by three linear motors. The driving forces of the two motors in the X direction are not on the same axis. The X direction movement is transmitted to the internal platform through elastic support, and the Y direction movement is controlled by The Y-direction motor is directly driven. The platform uses a precision grating sensor to feed back the position signal to form a closed-loop motion control system, and its positioning accuracy is only 150nm. The positioning accuracy of the platform is low, and since the X-direction movement needs to be transmitted through the elastic support, an error of elastic deformation is introduced, which is difficult to control.

Contents of the invention

The object of the present invention is to provide a three-degree-of-freedom ultra-precision micro-motion workbench, which has the characteristics of large load, large inertia, small stroke and high precision.

The invention provides a three-degree-of-freedom ultra-precision micro-motion workbench, which is characterized in that four circular air bearings are symmetrically installed at the four corners of the bottom of the outer frame, and the circular vacuum preloaded suction cups are embedded in the annular air bearings , the annular air bearing is connected with the support frame, the circular vacuum preloaded suction cup, the annular air bearing and the support frame form a vacuum preloaded air foot, which is installed at the bottom of the inner frame to support the inner frame of the micro-motion stage, The central axis of the air foot coincides with the central axis of the inner frame;

The outer frame is a hollow cuboid, and the inner frame is a cuboid with grooves around the outer frame; the first to fourth linear motor stators are symmetrically installed on the geometric centers of the four side walls inside the outer frame. The fourth linear motor mover is symmetrically installed on the geometric centers of the four side walls of the inner frame, and the first to fourth linear motor stators are respectively suspended in the grooves of the first to fourth linear motor movers;

The object-carrying platform is installed on the inner frame, and the first and second plane mirrors are bonded on the object-carrying platform. The material and shape of the first and second plane mirrors are the same. The first plane mirror is parallel to one side of the object-carrying platform. form an angle of 90 degrees with the centerline of the second plane mirror.

The invention provides a three-degree-of-freedom ultra-precision micro-motion workbench aiming at the bottleneck of small stroke, high precision and large load encountered in the development of the existing ultra-precision motion platform. The present invention utilizes the characteristics of large load of linear motors, and overcomes the shortcomings of low precision and single degree of freedom of linear motors by coordinating and controlling the combination of four linear motors, and realizes planar motion with large load, high precision and three degrees of freedom. The workbench proposed by the present invention adopts a single-layer structure, uses a laser interferometer for signal measurement and feedback, and is directly driven by 4 linear motors, and the X and Y motors are on the same plane, so there is no motion transmission, which reduces the The error transmission improves the precision of the micro-motion stage, and the positioning accuracy can reach 5nm. Specifically, the present invention has the following effects and advantages:

(1) Four linear motors are used for plane three-degree-of-freedom movement, which overcomes the disadvantage of small load of plane motors and can be used in large-load, multi-degree-of-freedom workplaces;

(2) The air-floating support structure ensures that the vertical stiffness is much greater than the direction of motion, so that the vertical fluctuations of the platform are extremely small when the platform moves, and the plane movement accuracy of the platform is not affected;

(3) The linear motor stator is fixed on the outer frame, does not participate in the movement of the micro-motion table, and will not increase the motion load of the micro-motion table;

(4) During the motion process, the stator of the linear motor is suspended in the groove of the mover, and there is no direct mechanical contact between the stator and the mover, no wear, and no motion error will be caused.

Description of drawings

Fig. 1 is the structural schematic diagram of the three-degree-of-freedom ultra-precision micro-motion workbench of the present invention;

Fig. 2 is a sectional view of A-A shown in Fig. 1 .

Detailed ways

The structure and working principle of the present invention are further described below in conjunction with design examples and accompanying drawings. The design can be used as a micro-motion stage in ultra-precision positioning equipment, the strokes in the X and Y directions are not greater than ±1mm, and the adjustment range in the angular direction is less than 0.002rad.

As shown in Figures 1 and 2, the present invention includes the following components: outer frame 1, first to fourth linear motor stators 2, 11, 17, 19, first to fourth linear motor movers 3, 10, 16, 18 , inner frame 4, first connecting plate 5, second connecting plate 9, loading platform 6, first plane mirror 7, second plane mirror 8, air bearing support frame 12, annular air bearing 13, circular vacuum preload Suction cup 14 , base 15 , first and second circular air bearings 20 , third and fourth circular air bearings 21 .

Four circular air bearings 20 are respectively symmetrically installed at four corners of the bottom of the outer frame 1 to support the outer frame 1 of the micro-motion table, so that the outer frame 1 is suspended on the base 15 . The circular vacuum preloaded suction cup 14 is embedded in the annular air bearing 13, and the annular air bearing 13 is connected with the support frame 12 by bolts, and the air foot with vacuum preload composed of the three passes through the outer frame 1 and is installed in the inner frame The bottom of 4 supports the inner frame 4 of the micro-motion platform, and the central axis of the air foot coincides with the central axis of the inner frame 4. The outer frame 1 can be connected with other external systems, and can also be fixed on the base. The outer frame is a hollow cuboid, and the first to fourth linear motor stators 2 , 11 , 17 , 19 are symmetrically installed on the geometric centers of the four side walls inside the outer frame 1 , as shown in FIG. 2 . The first to fourth linear motor movers 3 , 10 , 16 , 18 are symmetrically installed on the geometric centers of the four outer walls of the inner frame 4 . The first to fourth linear motor stators 2, 11, 17, 19 are respectively suspended in the slots of the first to fourth linear motor movers 3, 10, 16, 18, and there is no direct mechanical contact between the stators and the movers. The inner frame 4 is connected to the loading platform 6 through the first connecting plate 5 and the second connecting plate 9, the first connecting plate 5 and the second connecting plate 9 are symmetrically installed on the top of the inner frame 4, and the center connecting line passes through the inner frame 4 Center of the long side. The first plane mirror 7 and the second plane mirror 8 that are used for laser measurement are bonded on the object-carrying platform 6, and the material and shape of the first plane mirror 7 and the second plane mirror 8 are all identical, and the first plane mirror 7 and the object-carrying platform 6 are installed. The corresponding sides are parallel, and the centerlines of the first plane mirror 7 and the second plane mirror 8 form an included angle of 90 degrees.

The micro-motion stage proposed by the present invention is directly driven by four linear motors 2-3, 10-11, 16-17, 18-19 without any intermediate transmission links, which eliminates mechanical errors, reduces control difficulty, and is easy to realize precision position. Under the coordinated action of four motors 2-3, 10-11, 16-17, 18-19, the planar three-degree-of-freedom movement of the micro-motion table is realized. The specific process is: driving two X-direction linear motors 2-3, 10-11 generates the required X-direction motion, drives 2 Y-direction linear motors 16-17, 18-19 to generate the required Y-direction motion, through 4 motors 2-3, 10-11, 16-17, 18 A fit of -19 produces the desired angle of rotation. Driven by the motor, the first to fourth linear motor movers 3, 10, 16, and 18 drive the loading platform 6 to move together, so that the loading platform moves relative to the outer frame 1 and the first to fourth linear motor stators 2, 11 , 17, 19 inching. Due to the support of the air flotation system 12, 13, 14, 20, the vertical stiffness of the micro-movement table is very high, which ensures that the vertical error will not affect the motion accuracy when the platform moves. The platform is detected, controlled and driven by a closed-loop control system composed of a laser interferometer and a driving mechanism to achieve fast and precise positioning.

The three-degree-of-freedom ultra-precision micro-motion workbench carries the object and carries out the specific movement process from point to point as follows: When the target provided by the host computer is determined, the X-direction motor movers 3, 10 and the Y-direction motor movers 16, 18 follow the The numerical commands provided by the control system move relative to the X-direction motor stators 2, 11 and Y-direction motor stators 17, 19, and the linear motor movers 3, 10, 16, 18 drive the loading platform 6 to the required position; according to the laser interferometer feedback information, the system calculates the actual position of the silicon chip on the micro-motion table and the error with the target position, and the motor performs precise positioning after receiving the instruction to eliminate the error; the closed-loop control system repeats the detection and action until the positioning accuracy reaches 5nm and 0.25μrad Require.

The platform can be used in biotechnology equipment such as ultra-precision CNC machine tools, lithography machines, precision measuring equipment, biochip spotters, and biochip scanners.

Claims (1)

1. 3 freedom degree ultra-precise micro displacement workbench is characterized in that:

Four circular air-bearings (20) symmetry respectively are installed in four jiaos of outside framework (1) bottom, circular vacuum pretension sucker (14) is embedded in the annular air-bearing (13), annular air-bearing (13) is connected with bracing frame (12), circular vacuum pretension sucker (14), annular air-bearing (13) and bracing frame (12) are formed the gas foot of band vacuum pretension, this gas foot is installed in the bottom of inner frame (4) with supporting micropositioner inner frame (4), and the central shaft of gas foot overlaps with the central shaft of inner frame (4);

Outside framework (1) is the rectangular parallelepiped of hollow, and inner frame (4) is for being positioned at the rectangular parallelepiped that has groove all around of outside framework (1); On the geometric center that is installed in four inner sidewalls of outside framework (1) of first to fourth linear motor stator electric (2,11,17,19) symmetry, first to fourth linear motor rotor (3,10,16,18) symmetry is installed on the geometric center of four sidewalls of inner frame (4), and first to fourth linear motor stator electric (2,11,17,19) is suspended in respectively in the groove of first to fourth linear motor rotor (3,10,16,18);

Article carrying platform (6) is installed on the inner frame (4), first, second level crossing (7,8) is bonded on the article carrying platform (6), the material of first, second level crossing (7,8) is identical with shape, first level crossing (7) is parallel with a limit of article carrying platform (6), and the center line of first level crossing (7) and second level crossing (8) is the angle of 90 degree.

Images