Patent Publication Number: US-8523162-B2

Title: Toggle type with one axial positioning machine

Description:
FIELD OF THE INVENTION 
     The present invention relates to a positioning platform, and more particularly to a toggle-type with one axial positioning platform. 
     BACKGROUND OF THE INVENTION 
     Machines establish the groundwork of manufacturing industry, due to all products are produced by machines. Furthermore, machine tools establish the groundwork of mechanical industry due to all manufacturing processes require machine tool. Therefore, with the development in industry and the advancement in technology, the machine tool industry will be progressed as well. Because bio-medical industry, telecommunication industry and optoelectronic industry ramp recently, current related products have developed to be more miniaturized, for example, micro optical components of high-speed signal transmission, micro-sensors, micro holes of optical fibers and photolithography. Accordingly, the micro/meso-scale manufacturing technology is the key point in the oncoming fabrication technology. 
     In industrial applications, precise machining is based on high precision positioning technology. Therefore, how to enhance precise positioning is an important index in promotion of industry. The difficulties of the precise positioning technology resulted from too many uncertain factors. Generally, the factors, which are not concerned in large-scale positioning, should be concerned in micro/nano scale positioning. 
     The wet etching, plasma etching, LIGA process, electron beam, ion beams and so on are used in nano-scaled machining, thus resulting in the development of micro-electro mechanical system (MEMS). Generally speaking, MEMS technology is applied in the fabrication of about 2D to 2.5D geometry, and the relative precision of fabrication is limited to about 10-1 to 10-2 millimeter. However, for many 3-D miniaturized products having requirements of higher precision and complex shape, the MEMS technology is not able to meet the requirements. Besides, another bottleneck of the MEMS technology is that it can not be applied to metallic material or other diversified materials. Furthermore, scanning tunneling microscope (STM) or atomic force microscope need to be used in nano-scaled fabrication, but the operation speed is lower and the technique is not mature yet. 
     Currently, machine tools of multi-axles are serial connected mechanism. This serial connected mechanism, which is similar to cantilever beams, has a larger working area, but it may deform or have displacement due to external loading or its weight. Therefore, only the conventional servo system of serial connected mechanism of higher precision may achieve the precision of sub-micron or even nano-meter scaled. However, the requirements of the related control technique are very strict, and the cost of the whole equipment is effectively increased. Besides, machines features the piezoelectric actuators also have the problems of smaller stroke and hysteresis. 
     Generally, platforms of meso-scale machine tools, such as milling machines, are being directly placed on ballscrews and then driven by motors to move. Intrinsic or extrinsic vibration will affect machine tools operation and precision at the same time. Refer to  FIG. 1 ,  FIG. 1  shows a Taiwanese patent publication No. 302862, which discloses a toggle-type positioning platform, as a prior art. A screw rod  202  connects with a second platform  204  by a linkage  206 , wherein the moving direction of the second platform  204  is perpendicular to the screw rod  202 . When the screw rod driven by a motor  208  to rotate, the linkage  206  and the second platform  204  start to move along a predetermined path  210 . To overcome the aforesaid disadvantages, the linkage  206  being disposed between the screw rod  202  and the second platform  204 . Since the length L of the linkage  206  is fixed and the displacement of one end of the linkage  206  on the screw rod  202  is known, therefore the perpendicular distance H from the connecting portion to the screw rod  202  can be calculated from the trigonometric and geometric relationship. According to the numerical analysis data of the prior art, when the displacement of the screw is very small, the smaller distance H and higher positioning precision ΔH may be attained. Therefore, the length of the linkage, the displacement of the screw rod, the angle between the linkage and screw rod and other factors may affect the resolution and sensitivity of the platform. The method described above may provide higher precision of the machine tool, but the move speed of the platform is relatively low. Therefore, the present invention discloses tri-joints with one axial toggle-type machine to overcome the aforesaid disadvantages. Moreover, by the calculation of trigonometric functions, the precision of the platform can be less affected by extrinsic force and vibration and, at the same time, increase the move speed of the platform. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a toggle-type with one axial positioning machine with enhanced precision and faster moving speed, which extreme delicate, complex driving server is no longer required. 
     In one embodiment, the toggle-type with one axial positioning machine includes a first platform, a motor disposed on the platform, a ballscrew disposed on the first platform and coupled to the motor such that the motor drives the ballscrew rotation, a second platform disposed on the first platform with back and forth movement along a pre-determined direction, a linear bearing covering the ballscrew and moving along the ballscrew and with rotation of the ballscrew, a first link fastened to a lower part of the linear bearing and parallel to the ballscrew, a second link, and a third link between the second link and the second platform. The pre-determined direction is parallel to the ballscrew. The first link moves with the linear bearing. The second link, between the first link and the second link, is perpendicular to the third link. The ballscrew rotates to drive the first link, the second link, and the third link to move the second platform along the per-determined direction. 
     Each two of the first link, the second link, and the third link are connected by a bolt. The toggle-type with one axial positioning machine further comprises two rails disposed on outer sides of the second platform and between the first platform and the second platform. 
     The toggle-type with one axial positioning machine further comprises a fixed axis fastened on the second link. A position of the fixed axis can be any position of the second link. The fixed axis controls relative movement of the ballscrew and the second platform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a prior art. 
         FIG. 2  is a schematic diagram for illustrating principle structure of tri-joints with one axial according to an embodiment of the present invention. 
         FIG. 3  is a schematic diagram for illustrating theoretical structure of tri-joints with one axial according to an embodiment of the present invention. 
         FIG. 4  is a schematic diagram for illustrating sketch structure of toggle-type with one axial positioning machine according to an embodiment of the present invention. 
         FIG. 5  is a diagram for illustrating a comparison between theoretical value and measured values of moving distance versus motor rotating loops of the toggle-type with one axial positioning machine. 
         FIG. 6  is a sample photograph of the toggle-type with one axial positioning machine according to this invention. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The present invention provides a toggle type with one axial positioning platform. For complete understanding of the present invention, the following description will describe in detail the method steps and the components. The present invention is not limited by the specified particulars of the radiation emitting semiconductor devices that are familiar to persons skilled in the art. In addition, well-known components or method steps are not described in detail so as to avoid any additional limitation. The preferable embodiments of the present invention are described in detail. In addition to the detailed descriptions, the present invention also can be applied to other embodiments. Therefore, the scope of the present invention is not limited, and is dependent on the following claims. 
     This invention is designed by using tri-joints with one axial principle, as shown in  FIG. 2 . In  FIG. 2 , an upper portion and a lower portion are demonstrated for better understanding. In  FIG. 2 , the tri-joints indicate AB, BC and DE. With a line from A to E, two proportional triangles with different directions are formed. An intersect C, formed by the line AE and line BD and a fixed point, separates the two proportional triangles. The aforesaid principle explains that ratio of input and output is determined by the two proportional triangles. Hence, to know one triangle can verify the relationship of input and output. 
     This invention, by using Euler&#39;s law, calculates movement of a rigid body with a fixed point; that&#39;s a rotation around an axis. In order to express this invention more clearly, please refer to  FIG. 3 . The trigonometric function expression can be:
 
 R 2− R 3− R 4− R 1=0  (1)
 
 ae   jθ     2     −be   jθ     3     −ce   jθ     4     −de   jθ     1   =0  (2)
 
with Euler&#39;s laws:
 
 a (cos θ 2   +j  sin θ 2 )− b (cos θ 3   +j  sin θ 3 )− c (cos θ 4   +j  sin θ 4 )− d (cos θ 1   +j  sin θ 1 )=0  (3)
 
x component:
 
 a  cos θ2− b  cos θ3− c  cos θ4− d  cos θ1=0  (4)
 
so,
 
 a  sin θ2− b  cos θ2− c  sin θ 4 − d= 0  (5)
 
y component:
 
 a  sin θ2− b  sin θ3− c  sin θ4=0  (6),
 
wherein d is an independent variable, a, b, c, and θ 4  are known, and θ 2  and θ 3  can be solved. Because R 2  and R 3  are equal, Δθ of θ 2  and θ 3  are equal.
 
     
       
         
           
             
               
                 
                   
                     
                       
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     With the above deduction, the upper and lower triangles are proportional, and input of d can give output value. 
     Back to  FIG. 2 , position of the fixed point C in line BD can determine sizes of the two proportional triangles, and proportional ratio of the upper and lower triangles are length DC to length BC. Therefore, distance DE can be obtained by using distance of line AB times ratio of length DC to length BC. In other words, output can be obtained by a precise input to increase precision of a platform. 
     One embodiment is disclosed according to above theory. Please refer to  FIG. 4 , a toggle-type positioning platform includes a first platform  102 , a motor  104  disposed on the first platform  102 , a ballscrew  110  disposed on the first platform  102  and coupled to the motor  104  such that the motor  104  can drive the ballscrew rotating, a second platform disposed on the first platform  102  and moved back and forth along a pre-determined direction  126 , wherein the pre-determined direction  126  is anti-parallel to direction of the movement of the ballscrew, and a linear bearing covering the ballscrew  110  and moving with rotation of the ballscrew  110 . The toggle-type positioning platform also includes a first link  114  fastened to upper portion of the linear bearing  108  and parallel to the ballscrew  110  and moved with the linear bearing  108 , a second link  116 , and a third link  118 . the second link  116 , between the first link  116  and the third link  118 , is perpendicular to both first link  114  and third link  118 . The third link  118  is between the second link  116  and the second platform  120 , wherein rotation of the ballscrew  110  can drive the first link  114 , the second link  116 , and the third link  118  moving to move the second platform along the pre-determined direction  126 . In order to rotate the ballscrew  110  stable, an L-support  112  is provided for supporting the ballscrew  110 . 
     Next, the second platform  120  can move along the pre-determined direction  126  by using two rails  122 . Length of the rails  122  can be about length of the pre-determined direction  126 . Direction of the rails  122  can be parallel to the ballscrew  110 . The rails  122  can be between the first platform  102  and the second platform  120 , and can disposed on two opposite sides of the second platform  120 . The first platform can have a trench (not shown in the  FIG. 4 ) and the second platform  120  can move along the trench, wherein the trench can be V shape, U shape, or other shapes. 
     Then, the opposite ends of the first link  114  connect to the linear bearing  108  and the second link  116  respectively. The first link  114  and the second link  116  form a right angle. The opposite ends of the second link  116  connect to the first link  114  and the third link  118  respectively. The first link  114  is parallel to the third link  118 , and the second link  116  is perpendicular to both the first link  114  and the third link  118 . Further, a fixed axis  128  is disposed on the second link  116 . The fixed axis  128  can make the opposite two ends of the second link  116  free rotation without movement and therefore can change angles to the first link  114  and the third link  118 . The two opposite ends of the third link  118  connect to the second link  116  and the second platform  120 . The connections among three links are buckled by a first bolt  124   b , a second bolt  124   d  and C-hooks, and hence the angles between any two links and be varied. While the ballscrew  110  is rotated by the motor  104 , the liner bearing  108  covering on the ballscrew  110  can move back or forth with rotation of the ballscrew  110 . because the first link  114  is fastened to the lower portion of the liner bearing  108 , and while the linear bearing  108  moves with the ballscrew  110 , angles between each of the three links can be varied. The second platform  120  is then moved along the pre-determined direction  126  by the movement of the three links. 
     Then, a LASER meter is used to measure movement of the second platform  120 . Placing a beam splitter in front of the LASER meter and a reflecting mirror on the second platform and then aligned for reflecting LASER beam. A measuring method is as follows. The beam splitter is used for splitting the LASER beam into a reference beam and a beam to be measured when it enters. The beam to be measured is then reflected back on the same path by the reflecting mirror and meets the reference beam. After analyzed by a computer, the displacement of the second platform can be known. 
     Table 1 is numerical analysis data of the toggle-type with one axial positioning platform according to one embodiment of the present invention, wherein the data is calculated by the measuring method described in the above paragraph. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Loops 
                 Detect value 
                 Distance 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 0.033 
                 0.0073 
               
               
                 2 
                 0.0403 
                 0.0016 
               
               
                 3 
                 0.0419 
                 0.0018 
               
               
                 4 
                 0.0437 
                 0.0112 
               
               
                 5 
                 0.0549 
                 0.0907 
               
               
                 6 
                 0.1456 
                 0.0962 
               
               
                 7 
                 0.2418 
                 0.0953 
               
               
                 8 
                 0.3371 
                 0.0879 
               
               
                 9 
                 0.425 
                 0.1024 
               
               
                 10 
                 0.5274 
                 0.101 
               
               
                 11 
                 0.6284 
                 0.0963 
               
               
                 12 
                 0.7247 
                 0.0978 
               
               
                 13 
                 0.8225 
                 0.1005 
               
               
                 14 
                 0.923 
                 0.0978 
               
               
                 15 
                 1.0208 
                 0.0975 
               
               
                 16 
                 1.1183 
                 0.1 
               
               
                 17 
                 1.2183 
                 0.0931 
               
               
                 18 
                 1.3114 
                 0.0949 
               
               
                 19 
                 1.4063 
                 0.094 
               
               
                 20 
                 1.5003 
                 0.0972 
               
               
                 21 
                 1.5975 
                 0.0953 
               
               
                 22 
                 1.6928 
                 0.1057 
               
               
                 23 
                 1.7985 
                 0.1001 
               
               
                 24 
                 1.8986 
                 0.0991 
               
               
                 25 
                 1.9977 
                 0.0996 
               
               
                 26 
                 2.0973 
                 0.098 
               
               
                 27 
                 2.1953 
                 0.0933 
               
               
                 28 
                 2.2886 
                 0.1082 
               
               
                 29 
                 2.3968 
                 0.1007 
               
               
                 30 
                 2.4975 
                 0.0964 
               
               
                 31 
                 2.5939 
                 0.1001 
               
               
                 32 
                 2.694 
                 0.1018 
               
               
                 33 
                 2.7958 
                 0.0992 
               
               
                 34 
                 2.895 
                 0.0974 
               
               
                 35 
                 2.9924 
                 0.1026 
               
               
                 36 
                 3.095 
                 0.0995 
               
               
                 37 
                 3.1945 
                 0.101 
               
               
                 38 
                 3.2955 
                 0.1 
               
               
                 39 
                 3.3955 
                 0.1003 
               
               
                 40 
                 3.4958 
                 0.0977 
               
               
                 41 
                 3.5935 
                 0.0935 
               
               
                 42 
                 3.687 
                 0.1028 
               
               
                 43 
                 3.7898 
                 0.0997 
               
               
                 44 
                 3.8895 
                 0.1003 
               
               
                 45 
                 3.9898 
                 0.1042 
               
               
                 46 
                 4.094 
                 0.0997 
               
               
                 47 
                 4.1937 
                 0.099 
               
               
                 48 
                 4.2927 
                 0.0937 
               
               
                 49 
                 4.3864 
                 0.1053 
               
               
                 50 
                 4.4917 
                 0.0992 
               
               
                 51 
                 4.5909 
                 0.0972 
               
               
                 52 
                 4.6881 
                 0.1028 
               
               
                 53 
                 4.7909 
                 0.1024 
               
               
                 54 
                 4.8933 
                 0.0981 
               
               
                 55 
                 4.9914 
                 0.1024 
               
               
                 56 
                 5.0938 
                 0.092 
               
               
                 57 
                 5.1858 
                 0.0973 
               
               
                 58 
                 5.2831 
                 0.1101 
               
               
                 59 
                 5.3932 
                 0.0955 
               
               
                 60 
                 5.4887 
                 0.1025 
               
               
                 61 
                 5.5912 
                 0.1006 
               
               
                 62 
                 5.6918 
                 0.1045 
               
               
                 63 
                 5.7963 
                 0.1003 
               
               
                 64 
                 5.8966 
                 0.0996 
               
               
                 65 
                 5.9962 
                 0.1006 
               
               
                 66 
                 6.0968 
                 0.0984 
               
               
                 67 
                 6.1952 
                 0.1019 
               
               
                 68 
                 6.2971 
                 0.0998 
               
               
                 69 
                 6.3969 
                 0.0998 
               
               
                   
               
            
           
         
       
     
     From the table 1, a relationship between measured values of moving distance versus motor rotating loops of the toggle-type with one axial positioning machine is shown in  FIG. 5 . In this embodiment, number of motor&#39;s rotation loops is only to 69, but all data in the Table 1 can derive moved distance of the second platform in this invention. It is obvious that differences, between theoretical value to measured value from the first loop to the fourth loop in  FIG. 5  and refer to the Table 1, have a great value. It may be incurred by tolerances of the motor or ballscrew. When the motor rotates about more than five loops, each measured moved distance is about 0.1 mm for each loop. The theoretical value of each moved distance is 0.1 mm for each loop, and averaged measured value is about 0.09972, with an error 0.00028 mm. Hence, this invention can reach movement accuracy to five digits under rotation. By using this movement average value times total loops and multiplied by position of the fixed point C on the second link, moved distance of the second platform can be calculated. All experience data depend on material selected, but will not be discussed in this invention. A sample is shown in  FIG. 6  for reference. 
     This invention discloses a toggle-type with one axial positioning machine with enhanced precision. Further, moving speed in this invention can be faster than single-link toggle type mechanism. Moreover, high precision and high resolution can be provided without using extreme delicate, complex driving server. 
     Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.