Abstract:
Both shifting rate and positioning precision of a three-link toggle type positioning platform can be increased by using mechanism of three-link concept in this invention.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a positioning platform and machine tool, and more particularly to a three-link toggle type positioning platform and machine tool. 
         [0003]    2. Description of the Related Art 
         [0004]    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 optoelectronical 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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    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  64  connects with a second platform  14  by a linkage  62 , wherein the moving direction of the second platform  14  is perpendicular to the screw rod  64 . When the screw rod  64  driven by a motor  46  to rotate, the linkage  62  and the second platform  14  start to move along a predetermined path  54 . To overcome the aforesaid disadvantages, the linkage  62  being disposed between the screw rod  64  and the second platform  14 . Since the length L of the linkage  62  is fixed and the displacement of one end of the linkage  62  on the screw rod  64  is known, therefore the perpendicular distance H from the connecting portion to the screw rod  64  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 a three-link toggle type apparatus 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 
       [0009]    To achieve the aforesaid object and industrial demands, the present invention discloses a three-link toggle type positioning platform which comprises a first platform, a first motor, a first ballscrew, a second platform, a first linkage, a second linkage and a third linkage. The first motor is disposed on the first platform. The first ballscrew is disposed on the first platform and coupled to the first motor, wherein the first motor is suitable for driving the first ballscrew to rotate. The second platform is disposed on the first platform, wherein the second platform is suitable for moving back and fourth alternately along a first predetermined path, wherein a first angle is existed between an extended direction of the first predetermined path and the first ballscrew. The second linkage is fixed on a first base, and is parallel to the first ballscrew and the second platform. The first linkage is disposed between the first ballscrew and the second linkage for connection, wherein a second angle is existed between the first ballscrew and the first linkage. The third linkage is disposed between the second linkage and the second platform, wherein a third angle is existed between the second linkage and the third linkage. Moreover, the first linkage, the second linkage and the third linkage are driven simultaneously by the rotation of the first ballscrew, such that the second platform is driven to move along the first predetermined path. 
         [0010]    According to the present invention, the first angle of the three-link toggle type positioning platform is about 90°. 
         [0011]    According to the present invention, the second angle of the three-link toggle type positioning platform is between about 0° to 90°. 
         [0012]    According to the present invention, the third angle of the three-link toggle type positioning platform is between about 0° to 90°. 
         [0013]    According to the present invention, the three-link toggle type positioning platform comprises two first linear bearings penetrate a first slide rail respectively, wherein the two first linear bearings are disposed on bilateral sides of the second platform and between the second platform and the first platform. 
         [0014]    According to the present invention, the two first linear bearings of the three-link toggle type positioning platform are perpendicular to the first ballscrew. 
         [0015]    According to the present invention, the two opposite ends of the first linkage of the three-link toggle type positioning platform are connected to the first ballscrew and the second linkage by a ball bearing and a bolt. 
         [0016]    According to the present invention, the two opposite ends of the second linkage of the three-link toggle type positioning platform are connected to the first linkage and the first base by the ball bearing and the bolt. 
         [0017]    The present invention further provides a three-link toggle type machine tool which comprises a first three-link toggle type positioning platform and a second three-link toggle type positioning platform. The first three-link toggle type positioning platform comprises a first platform, a first motor, a first ballscrew, a second platform, a first linkage, a second linkage, and a third linkage. The first motor is disposed on the first platform. The first ballscrew is disposed on the first platform and coupled to the first motor, wherein the first motor is suitable for driving the first ballscrew to rotate. The second platform is disposed on the first platform, wherein the second platform is suitable for moving back and fourth alternately along a first predetermined path, wherein a first angle is existed between an extended direction of the first predetermined path and the first ballscrew. The second linkage is fixed on a first base, wherein the second linkage is parallel to the first ballscrew and the second platform. The first linkage is disposed between the first ballscrew and the second linkage, wherein a second angle is existed between the first balscrew and the firstlinkage. The third linkage is disposed between the second linkage and the second platform, wherein a third angle is existed between the second linkage and the third linkage. Moreover, the first linkage, the second linkage and the third linkage are driven simultaneously by the rotation of the first ballscrew, such that the second platform is driven to move along the first predetermined path. 
         [0018]    The second three-link toggle type positioning platform is disposed on the first three-link toggle type positioning platform, wherein the second three-link toggle type positioning platform comprises a second motor, a second ballscrew, a third platform, a fourth linkage, a fifth linkage, and a sixth linkage. The second motor is disposed on the second platform. The second ballscrew is disposed on the second platform and coupled to a second motor, wherein the second motor is suitable for driving the second ballscrew to rotate. The third platform is disposed on the second platform, wherein the third platform is suitable for moving back and fourth alternately along a second predetermined path, wherein a fourth angle is existed between an extended direction of the second predetermined path and the second ballscrew. The fourth linkage is disposed between the second ballscrew and the fifth linkage, wherein a fifth angle is existed between the second ballscrew and the fourth linkage. The fifth linkage is fixed on a second base, and is parallel to the second ballscrew and the third platform. The sixth linkage is disposed between the fifth linkage and the third platform, wherein a sixth angle is existed between the fifth linkage and the sixth linkage. Moreover, the fourth linkage, the fifth linkage and the sixth linkage are driven simultaneously by the rotation of the second ballscrew, such that the third platform is driven to move along the second predetermined path. 
         [0019]    According to the present invention, the first angle of the three-link toggle type machine tool is about 90°. 
         [0020]    According to the present invention, the second angle of the three-link toggle type machine tool is between about 0° to 90°. 
         [0021]    According to the present invention, the third angle of the three-link toggle type machine tool is between about 0° to 90°. 
         [0022]    According to the present invention, the fourth angle of the three-link toggle type machine tool is about 90°. 
         [0023]    According to the present invention, the fifth angle of the three-link toggle type machine tool is between about 0° to 90°. 
         [0024]    According to the present invention, the sixth angle of the three-link toggle type machine tool is between about 0° to 90°. 
         [0025]    According to the present invention, the three-link toggle type machine tool further comprises two first linear bearings penetrate a first slide rail respectively, wherein the two first linear bearings are disposed on the bilateral sides of the second platform and between the first platform and the second platform. 
         [0026]    According to the present invention, the three-link toggle type machine tool further comprises two second linear bearings penetrate a second slide rail respectively, wherein the two second linear bearings are disposed on the bilateral sides of the third platform and between the second platform and the third platform. 
         [0027]    According to the present invention, the two first linear bearings are perpendicular to the first ballscrew. 
         [0028]    According to the present invention, the two second linear bearings are perpendicular to the second ballscrew. 
         [0029]    According to the present invention, the two opposite ends of the first linkage are connected to the first ballscrew and the second linkage by the ball bearing and the bolt. 
         [0030]    According to the present invention, the two opposite ends of the second linkage are connected to the first linkage and the first base by ball the bearing and the bolt. 
         [0031]    According to the present invention, the two opposite ends of the third linkage are connected to the second linkage and the second platform by the ball bearing and the bolt. 
         [0032]    According to the present invention, the two opposite ends of the fourth linkage are connected to the second ballscrew and the fifth linkage by the ball bearing and the bolt. 
         [0033]    According to the present invention, the two opposite ends of the sixth linkage are connected to the fifth linkage and the third platform by the ball bearing and the bolt. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    The invention will be described according to the appended drawings in which: 
           [0035]      FIG. 1  shows a Taiwanese patent publication No. 302862 disclosing a toggle-type positioning platform; 
           [0036]      FIG. 2  shows a schematic diagram of a three-link structure; 
           [0037]      FIG. 3  is a theoretical curve diagram showing a relation between a number of turns of motor and a moving distance of platform; 
           [0038]      FIG. 4  shows a top view showing a three-link toggle type positioning platform of the present invention; 
           [0039]      FIG. 5  shows a solid diagram of a three-link toggle type positioning platform according to the present invention; 
           [0040]      FIG. 6  shows a solid diagram of a three-link toggle type machine tool according to the present invention; 
           [0041]      FIG. 7  is numerical analysis data of the first three-link toggle type positioning platform according to one embodiment of the present invention; and 
           [0042]      FIG. 8  is a curve diagram showing a relation between the theoretical value of a number of turns of motor and a moving distance of platform and that of the measuring value of a three-link toggle type positioning platform according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    The present invention provides a three-link toggle type 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. 
         [0044]    The present invention is based on a three-link theorem which is shown by a schematic diagram of a three-link structure in  FIG. 2 . According to the diagram, we can substitute each angle and distance into two trigonometric equations below. 
       Input: 
       [0045]      4 a ×sin(θ 2 )− b ×cos(θ 3 )=73.87+ c     (1)
 
         [0000]        b ×sin(θ 3 )−4 a ×cos(θ 2 )= d    (2)
 
         [0046]    The expression in Equation (1) can be converted as: 
         [0000]      cos(θ 3 )=(4 a ×sin(θ 2 )−( c+ 73.87))/ b  
 
         [0047]    Then by applying Pythagorean Theorem, the above equation can be converted as: 
         [0000]        b ×sin(θ 3 )=( b 2−(4 a ×sin(θ 2 )− c ) 2 ) 1/2  
 
         [0048]    By substituting the above equation into Equation (2), the following equation can be obtained. 
         [0000]      ( b 2−(4 a ×sin(θ 2 )− c ) 2 ) 0.5 −4 a ×cos(θ 2 )− d= 0   (3)
 
       Output: 
       [0049]        a ×sin(θ 2 )+ B ×cos(θ 4 )= C    (4)
 
         [0000]        a ×cos(θ 2 )− B ×cos(θ 4 )= D    (5)
 
         [0050]    The expression in Equation (4) can be converted as: 
         [0000]      sin(θ 4 )=( C−a× sin(θ 2 ))/ B  
 
         [0051]    Then by applying Pythagorean Theorem, the above equation can be converted as: 
         [0000]        B ×cos(θ 4 )=( B 2−( C−a ×sin(θ 2 ) 2 ) 1/2 )
 
         [0052]    By substituting the above equation into Equation (5), the following equation can be obtained. 
         [0000]        a ×cos(θ 2 )−( B 2−( C−a ×sin(θ 2 ) 2 ) 1/2 )−( D+ 106.9445)=0   (6)
       where parameter a, b, c, d, B, C, θ 2 , θ 3  and θ 4  are clearly shown in  FIG. 2 , where a moving distance of platform D and a number of turns of motor c are unknown, and the following Equation (7) and (8) can be obtained by substituting the above parameters into Equation (3) and (6).       
 
         [0000]      (22500−(200×sin(θ 2 )−( c+ 73.87)) 2 ) 0.5 −200×cos(θ 2 )−90=0   (7)
 
         [0000]      (50×cosd(θ 2 )+(14400−(100−50×sind(θ 2 )) 2 ) 0.5 )−( D+ 106.93)=0   (8)
 
         [0054]    Then utilizing a software called MATLAB to calculate Equation (7) and (8). Since the known angel θ 2  is 90°, according to  FIG. 1 , the moving distance of platform D can be obtained by substituting the number of turns of motor c into Equation (7) and (8).  FIG. 3  is a theoretical curve diagram showing a relation between the number of turns of motor and the moving distance of platform, wherein the number of turns of motor and the moving distance of platform are in direct proportion, that is to say, when the number of turns of motor increases, the moving distance of platform will increase, too. Further, a slope value of the theoretical curve is large in the beginning. However, when the motor reached 98 turns, the moving distance of platform is significantly slowing down, thereby decreasing the slope value of the theoretical curve. In other words, according to the theoretical value, the present invention not only increases the moving speed of the platform but also improves the precision thereof. 
         [0055]      FIG. 4  is a top view showing a three-link toggle type positioning platform of the present invention. According to one embodiment, the present invention discloses a three-link toggle type positioning platform  10  which comprises a first platform  12 , a first motor  46 , a first ballscrew  32 , a second platform  14 , a first linkage  34 , a second linkage  36  and a third linkage  38 . The first motor  46  is disposed on the first platform  12 . The first ballscrew  32  is disposed on the first platform  12  and coupled to the first motor  46 , wherein the first motor  46  is suitable for driving the first ballscrew  32  to rotate. The second platform  14  is disposed on the first platform  12 , wherein the second platform  14  is suitable for moving back and fourth alternately along a first predetermined path  54 , wherein a first angle  22  is existed between an extended direction of the first predetermined path  54  and the first ballscrew  32 . The second linkage  36  is fixed on a first base  48 , and is parallel to the first ballscrew  32  and the second platform  14 . The first linkage  34  is disposed between the first ballscrew  32  and the second linkage  36 , wherein a second angle  24  existed between the first ballscrew  32  and the first linkage  34 . The third linkage  38  is disposed between the second linkage  36  and the second platform  14 , wherein a third angle  26  is existed between the second linkae  36  and the third linkage  38 . Moreover, the first linkage  34 , the second linkage  36  and the third linkage  38  are driven simultaneously by the rotation of the first ballscrew  32 , such that the second platform  14  is driven to move along the first predetermined path  54 . 
         [0056]    Further,  FIG. 5  shows a solid diagram of a three-link toggle type positioning platform according to the present invention. The aforesaid second platform  14  can move back and fourth along the first predetermined path  54  with the help of a first linear bearing  44  and a first slide rail  42 . The present invention comprises a first linear bearing  44  penetrates a first slide rail  42 , wherein two opposite ends of the first slide rail  42  are fixed on respective supporting frames  50 . The length of the first slide rail  42  is equal to that of the first predetermined path  54 . The moving direction of the first linear bearing  44  and the first slide rail  42  is perpendicular to the first ballscrew  32 . Furthermore, the first linear bearing  44  and the first slide rail  42  are disposed between the first platform  12  and the second platform  14  and fixed on two opposite sides of the third platform  14 . Due to the first linear bearing  44  is a long-shaped cylindrical tube, which is made of iron or other material, the second platform  14  can not being fixed on it. In the present embodiment, the first linear bearing  44  is fixed in a stable long-shaped quadrate tube in order to form a flat surface which disposed between the second platform  14  and the third platform  70  to avoid roatation. The second platform  14  may have a guide groove and the third platform  70  is suitable for moving along the guide groove. The guide groove has a cross-section of V-shape, U-shape, or other shapes. Besides, the present embodiment further comprises a ball bearing. The ball bearing is disposed on the second platform  14  and is between the second platform  14  and the third platform  70 , and therefore the second platform  14  may move along the first predetermined path  54 . In brief, the ball bearing may move along the guide groove (not shown). 
         [0057]    The connecting structure for three-link linkage is to connect two opposite ends of the first linkage  34  with the first ballscrew  32  and the second linkage  36 , and a second angle  24  is existed between the first ballscrew  32  and the fisrdt linkage  34 . One opposite end of the second linkage  36  is fixed on the first base  48 , wherein the first base  48  can support the second linkage  36 . One end of the third linkage  38  connects to the second linkage  36  where near the first base  48 . Moreover, one opposite end of the third linkage  38  connects the second platform, wherein a third angle  26  is existed between the second linkage  36  and the third linkage  38 . 
         [0058]    Due to one end of the second linkage  36  is connected to the first base  48  by a ball bearing and a bolt so as to function as a fixed axle, the second linkage  36  can only move left and right. When the first ballscrew  32  is driven by the first motor  46  to rotate, the first linkage  34 , the second linkage  36  and the third linkage  38  are driven simultaneously by the first ballscrew  32  and cause the second angle  24  and the third angle  26  changing along with their movement. Since the second linkage  36  is fixed on the first base  48 , the third linkage is non-movable. Moreover, in order to connect three linkages with the second base  14  and the first ballscrew  32  on a same horizontal plane, the three linkages have a supporting frame  50  which supports the three linkages having the same height as the second base  14  and the first ballscrew  32 . In that way, the suspended three linkages can apply force properly. 
         [0059]    Additionally, the second linkage  36  is connected to the first linkage  34  and the third linkage  38 . When the first ballscrew  32  is driven by the first motor  46  to rotate, the three linkages are driven simultaneously by the rotation of the first ballscrew  32 . The second angle  24  and the third angle  26  would change due to the movements of the three linkages, such that the second platform  14  is driven to move along the first predetermined path  54 . 
         [0060]    In the present invention, the first angle is existed between the extended directions of the second platform  14  and the first ballscrew  32 , wherein the first angle is about 90°. The second angle is existed between the first linkage  34  and the third linkage  38 , wherein the second angle is between about 0° to 90°. Further, the third angle is existed between the second linkage  36  and the third linkage  38 , wherein the third angle is between about 0° to 90°. 
         [0061]    The first ballscrew  32 , the first linkage  34 , the second linkage  36 , the third linkage  38 , the second platform  14  and the first base  48  are connected by the ball bearing and the bolt in order to decrease frictions therebetween and to decrease the load of the first motor  46 . 
         [0062]    The present invention further provides a three-link toggle type machine tool, as shown in  FIG. 6 , which comprises a first three-link toggle type positioning platform  10  and a second three-link toggle type positioning platform  20 , wherein the first three-link toggle type positioning platform  10  and the second three-link toggle type positioning platform  20  are stacked to form the three-link toggle type machine tool. In addition, a first predetermined path  54  of the first three-link toggle type positioning platform  10  is perpendicular to a second predetermined path  94  of the second three-link toggle type positioning platform  20 . 
         [0063]    Please refer to  FIG. 5  since the detail structure of the first three-link toggle type positioning platform  10  does not show in  FIG. 6 . The first three-link toggle type positioning platform  10  comprises a first platform  12 , a first motor  46 , a first ballscrew  32 , a second platform  14 , a first linkage  34 , a second linkage  36  and a third linkage  38 . The first motor  46  is disposed on the first platform  12 . The first ballscrew  32  is disposed on the first platform  12  and coupled to the first motor  46 , wherein the first motor  46  is suitable for driving the first ballscrew  32  to rotate. The second platform  14  is disposed on the first platform  12 , wherein the second platform  14  is suitable for moving back and fourth alternately along a first predetermined path  54 , wherein a first angle  22  is existed between an extended direction of the first predetermined path  54  and the first ballscrew  32 . The second linkage  36  is fixed on a first base  48  and is parallel to the first ballscrew  32  and the second platform  14 . The first linkage  34  is disposed between the first ballscrew  32  and the second linkage  36 , wherein a second angle  24  is existed between the first ballscrew  32  and the first linkage  34 . The third linkage  38  is disposed between the second linkage  36  and the second platform  14 , wherein a third angle  26  is existed between the second linkage  36  and the third linkage  38 . Moreover, the first linkage  34 , the second linkage  36  and the third linkage  38  are driven simultaneously by the rotation of the first ballscrew  32 , such that the second platform  14  is driven to move along the first predetermined path  54 . 
         [0064]    Referring to  FIG. 6 , the second three-link toggle type positioning platform  20  is disposed on the first three-link toggle type positioning platform  10 , wherein the second three-link toggle type positioning platform  20  comprises a second motor  90 , a second ballscrew  78 , a third platform  70 , a fourth linkage  80 , a fifth linkage  82 , and a sixth linkage  84 . The second motor  90  is disposed on the second platform  14 . The second ballscrew  78  is disposed on the second platform  14  and coupled to a second motor  90 , wherein the second motor  90  is suitable for driving the second ballscrew  78  to rotate. The third platform  70  is disposed on the second platform  14 , wherein the third platform  70  is suitable for moving back and fourth alternately along a second predetermined path  94 , wherein a fourth angle  72  is existed between an extended direction of the second predetermined path  94  and the second ballscrew  78 . The fourth linkage  80  is disposed between the second ballscrew  78  and the fifth linkage  82 , wherein a fifth angle  74  is existed between the second ballscrew  78  and the fourth linkage  80 . The fifth linkage  82  is fixed on a second base  92  and is parallel to the second ballscrew  78  and the third platform  70 . The sixth linkage  84  is disposed between the fifth linkage  82  and the third platform  70 , wherein a sixth angle  76  is existed between the fifthlinkage  82  and the sixth linkage  84 . Moreover, the fourth linkage  80 , the fifth linkage  82  and the sixth linkage  84  are driven simultaneously by the rotation of the second ballscrew  78 , such that the third platform  70  is driven to move along the second predetermined path  94 . 
         [0065]    The aforesaid third platform  70  can move back and fourth along the second predetermined path  94  with the help of a second linear bearing  88  and a second slide rail  86 . The present invention comprises a second linear bearing  88  penetrates a second slide rail  86 , wherein two opposite ends of the second slide rail  86  are fixed on repective supporting frames  50 . The length of the second slide rail  86  is equal to that of the second predetermined path  94 . The moving direction of the second linear bearing  88  and the second slide rail  86  is perpendicular to the second ballscrew  78  and the first predetermined path  54 . Furthermore, the second linear bearing  88  and the second slide rail  86  are disposed between the second platform  14  and the third platform  70  and fixed on the bilateral sides of the third platform  70 . Due to the second linear bearing  88  is a long-shaped cylindrical tube, which is made of iron or other materials, the third platform  70  can not being fixed on it. In the present embodiment, the second linear bearing  88  is fixed in a stable long-shaped quadrate tube in order to form a flat surface, which is disposed between the second platform  14  and the third platform  70  to avoid rotation. The second platform  14  may have a guide groove and the third platform  70  is suitable for moving along the guide groove. The guide groove has a cross-section of V-shape, U-shape, or other shapes. Besides, the present embodiment further comprises a ball bearing. The ball bearing is disposed on the second platform  14  and is between the second platform  14  and the third platform  70 , and therefore the third platform  70  may move along the second predetermined path  94 . In brief, the ball bearing may move along the guide groove (not shown). 
         [0066]    The connecting structure for three-link linkage is to connect two opposite ends of the fourth linkage  80  with the second ballscrew  78  and the fifth linkage  82 , wherein a fifth angle  74  is existed between the second ballscrew  78  and the fourth linkage  80 . One opposite end of the fifth linkage  82  is fixed on the second base  92 , wherein the second base  92  can support the fifth linkage  82 . One end of the sixth linkage  84  connects to the fifth linkage  52  where near the second base  92 . Moreover, one opposite end of the sixth linkage  84  connects the third platform  70 , wherein a sixth angle  76  is existed between the fifth linkage  82  and the sixth linkage  84 . 
         [0067]    Due to one end of the fifth linkage  82  is connected to the second base  92  by a ball bearing and a bolt  52  so as to function as a fixed axle, the fifth linkage  82  can only move left and right. When the second ballscrew  78  is driven by the second motor  90  to rotate, the fourth linkage  80 , the fifth linkage  82  and the sixth linkage  84  are driven simultaneously by the second ballscrew  78  and cause the fifth angle  74  and the sixth angle  76  changing along with their movement. Since the fifth linkage  82  is fixed on the second base  92 , the third linkage is non-movable. Moreover, in order to connect three linkages with the third base  70  and the second ballscrew  78  on a same horizontal plane, the three linkages have a supporting frame  50  which supports the three linkages having the same height as the third base  70  and the second ballscrew  78 . In that way, the suspended three linkages can apply force properly. 
         [0068]    Additionally, the fifth linkage  82  is connected to the fourth linkage  80  and the sixth linkage  84 . When the second ballscrew  78  is driven by the second motor  90  to rotate, the three linkages are driven simultaneously by the rotation of the second ballscrew  78 . The fifth angle  74  and the sixth angle  76  would change due to the movements of the three linkages, such that the third platform  70  is driven to move along the second predetermined path  94 . 
         [0069]    In the present invention, the fourth angle is existed between the extended directions of the third platform  70  and the second ballscrew  78 , wherein the fourth angle is about 90°. The fifth angle is existed between the fourth linkage  80  and the fifth linkage  82 , wherein the fifth angle is between about 0° to 90°. Further, the sixth angle is existed between the fifth linkage  82  and the sixth linkage  84 , wherein the sixth angle is between about 0° to 90°. 
         [0070]    The second ballscrew  78 , the fourth linkage  80 , the fifth linkage  82 , the sixth linkage  84 , the third platform  70  and the second base  92  are connected by the ball bearing and the bolt  52  in order to decrease frictions therebetween and to decrease the load of the second motor  90 . 
         [0071]    Then, a LASER meter is being used to measure the amount of movement of the second platform  14  of the first three-link toggle type positioning platform  10 . 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 minor and meets the reference beam. After analyzed by a computer, the displacement of the second platform can be known. 
         [0072]      FIG. 7  is numerical analysis data of the first three-link toggle type positioning platform according to one embodiment of the present invention, wherein the data is calculated by the measuring method described in the above paragraph. 
         [0073]    The relationship between number of turns of motor and amount of movement of platform can be calculated according to the data shown in  FIG. 7  and being compared with theoretical value in  FIG. 8 . The maximum number of turns of motor in the present invention is only 50 turns less than that of the theory which has 100 turns. However, according to the data collected from 5 to 50 turns of the motor, the amount of movement of the second platform in one embodiment is very similar to theoretical value, that is, when the number of turns of motor in one embodiment of the present invention reaches 100 turns, the resulting value will be similar to theoretical value, too. Although the materials used in the present embodiment may have large effect to the experimental data, it is not under discussion here. 
         [0074]    The present invention provides a positioning platform with a toggle-type mechanism to improve its positioning precision. Moreover, the present invention provides a positioning platform with a three-link toggle type mechanism which makes it move faster than a single-link toggle type mechanism 
         [0075]    The above-described embodiment of the present invention is intended to be illustrative only. Numerous alternative embodiments may be devised by persons skilled in the art without departing from the scope of the following claims.