A space two-movement and one-rotation compliant parallel positioning system with large travel and high precision

Abstract

The invention discloses a large-stroke and high-precision spatial two-movement and one-rotation compliant parallel positioning system, which belongs to the field of mechanical structure design and manufacturing. Four piezoelectric actuators are used to realize the movement of three degrees of freedom of two movements (y direction and z direction) and one rotation (x direction) of a moving platform. The moving platform and each piezoelectric actuator are respectively connected by two compliant branches, and the two different compliant branches are respectively composed of a bridge displacement amplifier and two flexible U hinges and two wedge blocks; a displacement amplifier and two flexible R hinges and two wedge blocks. The bridge displacement amplifier is the core component of the compliant branch, which plays the role of outputting the driver displacement and amplifying the driving stroke, and enables the moving platform to perform a composite movement of large-stroke movement and large-stroke rotation in space under the flexible U pair and the flexible R side effect.

Description

Technical Field

[0001] The invention belongs to the field of mechanical structure design and manufacturing, and discloses a space two-movement one-rotation compliant parallel positioning system with large stroke and high precision. Background Art

[0002] At present, the common existing technology in the industry is as follows: In industrial applications, the three-degree-of-freedom parallel robot mechanism with two translations and one rotation has important applications, but there is relatively little research on this degree-of-freedom parallel mechanism. At the same time, with the increasing advancement of science and technology, traditional rigid mechanisms have been unable to meet the ever-increasing needs in the field of high-end machinery manufacturing. Unlike traditional rigid mechanisms, compliant mechanisms are a new type of generalized mechanism that uses elastic deformation to complete the transmission and conversion of force and motion. This type of mechanism actively uses the deformation of rods or elastic elements to improve and enhance the performance of the mechanism. Since the elastic element replaces the rigid kinematic pair, the compliant mechanism avoids problems such as noise, friction and wear caused by the clearance of the kinematic pair. At the same time, this type of mechanism has manufacturing characteristics such as less assembly, even no assembly required, easy to achieve integrated processing, easy miniaturization, and product advantages such as high precision, high reliability, low manufacturing cost and maintenance cost. With these unique advantages, compliant mechanisms have been widely used instead of traditional rigid mechanisms in high-tech fields such as precision engineering, aerospace, bioengineering, and microelectromechanical systems (MEMS). However, due to the structural characteristics of compliant hinges, if the appropriate method is not used to design the compliant mechanism, only a very small stroke can be achieved. There has not yet been a two-translation-one-rotation compliant parallel mechanism that meets the requirements of accuracy, has a large motion stroke, and is miniaturized. Even research on compliant mechanisms of this type of freedom is relatively rare.

[0003] In summary, the problems of the existing technology are: the traditional two-translation-one-rotation compliant mechanism is difficult to achieve micron-level precision; the general compliant parallel mechanism can only have a small motion stroke, and the stroke size mainly depends on the stroke size of the drive device; at present, there are relatively few studies on parallel mechanisms with two translations and one rotational freedom, and even fewer studies on compliant mechanism models with this type of freedom. At the same time, the general compliant U-shaped hinge is large in size and low in precision, which is difficult to meet the high-precision and miniaturization characteristics of the compliant parallel mechanism.

[0004] Difficulty and significance of solving the above technical problems: The traditional two-translation and one-rotation mechanism is limited by the manufacturing process level and is difficult to achieve micron-level movement. It is necessary to use the characteristics of the compliant mechanism, combine the traditional mechanism design method with the compliant mechanism, and select a suitable compliant hinge to replace the rigid hinge in the traditional mechanism, so as to achieve the micron-level precision goal. Usually, it is difficult to achieve a larger stroke of the compliant parallel mechanism by relying solely on a piezoelectric actuator. The bridge displacement amplifier is used in this mechanism because it can amplify the input displacement of the piezoelectric actuator. The improved two-translation and one-rotation three-degree-of-freedom mechanism of the present invention solves the problem of small output stroke of the mechanism. While the stroke of the mechanism is amplified, the flexible hinge, especially the U-shaped hinge, usually has low rotation accuracy due to its large size, and it is difficult to meet the design requirements. The improved new U-shaped hinge of the present invention makes the hinge have the characteristics of small size and compact structure. At the same time, it can also withstand large concentrated stress. Within the specified stroke range, the stress is usually less than the yield limit of the material. Two flexible branches are designed according to the characteristics of flexible hinges. After replacing the branches of the traditional two-translation and one-rotation parallel mechanism, the positioning system can achieve three-degree-of-freedom motion with two translations and one rotation and micron-level precision while retaining the characteristics of large stroke and miniaturization. It is widely used in integrated circuit manufacturing, EMS, high-precision positioning platforms and other fields. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a spatial two-movement and one-rotation compliant parallel positioning system with large stroke and high precision.

[0006] The present invention is implemented as follows: a large-stroke high-precision space two-movement one-rotation flexible parallel positioning system, the large-stroke high-precision space two-movement one-rotation flexible parallel positioning system is provided with:

[0007] 4 piezoelectric actuators;

[0008] The upper and lower platforms are connected to the piezoelectric actuator by flexible branches of "UPU" and "RPR";

[0009] The bridge displacement amplifier is the core component of the two types of flexible branches. The "UPU" flexible branch consists of a bridge displacement amplifier, two wedge blocks, and two flexible U hinges; the "RPR" flexible branch consists of a bridge displacement amplifier, two wedge blocks, and two flexible R hinges.

[0010] Furthermore, the two pairs of flexible branch components are symmetrically divided into 360° angles and evenly distributed on the upper plane of the fixed platform. In the "UPU" branch, the flexible U hinge, wedge block, bridge displacement amplifier, wedge block, and flexible U hinge are connected in series from bottom to top; in the "RPR" branch, the flexible R hinge, wedge block, bridge displacement amplifier, wedge block, and flexible R hinge are connected in series from bottom to top;

[0011] The flexible U-hinge is further a compact flexible Hooke's hinge, which is composed of two pairs of orthogonal semi-biaxial compliant hinges, and the two rotation axes of the U-hinge intersect at an orthogonal point.

[0012] Furthermore, the fixed platform and two pairs of flexible hinges close to the fixed platform are installed and assembled in sequence, and the threaded end surface of the fixed platform cooperates with the lower end surfaces of each flexible hinge, and is connected from bottom to top with bolts.

[0013] The rotating shaft of the flexible R hinge connected to the fixed platform is parallel to the side of the fixed platform, and the axis of the end face of the flexible U hinge connected to the fixed platform is parallel to the side of the fixed platform.

[0014] Furthermore, the four wedge-shaped blocks close to the fixed platform plane have their lower sides facing the inner side of the platform and their higher sides facing the outer side of the platform;

[0015] The four wedge-shaped blocks close to the plane of the moving platform have their lower sides facing the outer side of the platform and their higher sides facing the inner side of the platform.

[0016] Furthermore, one end of the eight wedge blocks close to the bridge displacement amplifier is fixed to the two end faces of the amplifier and connected with bolts. The bolts are screwed from one side of the amplifier to one side of the wedge blocks. The other end faces of the wedge blocks are welded to the flexible U hinge and the flexible R hinge respectively.

[0017] Furthermore, the flexible unit of the bridge displacement amplifier is composed of 8 leaf springs, and for the convenience of assembly and positioning, the two input ends are configured as bosses, one side of which has a groove.

[0018] Furthermore, the four piezoelectric actuators are placed in four bridge displacement amplifiers respectively.

[0019] The end of the piezoelectric actuator matches the boss end face of the bridge displacement amplifier and is connected by bolts, and the bolts are screwed from one side of the bridge displacement amplifier at the respective corresponding positions toward one side of the driver.

[0020] The output end of the piezoelectric actuator is horizontally placed at the center point of the groove on the end surface of another boss of the bridge displacement amplifier.

[0021] Furthermore, the lower plane of the moving platform and two pairs of flexible hinges close to the moving platform are installed and assembled in sequence, and the threaded end surface of the moving platform cooperates with the upper end surfaces of each flexible hinge, and is connected from top to bottom with bolts.

[0022] The rotating shaft of the flexible R hinge connected to the moving platform is parallel to the side of the moving platform, and the axis of the end face of the flexible U hinge connected to the moving platform is parallel to the side of the moving platform.

[0023] To sum up, the advantages and positive effects of the present invention are: four piezoelectric actuators are used to realize two translations (along the y and z axes) and one rotation (along the x axis) of the moving platform, and the upper and lower platforms are connected to each piezoelectric actuator by two pairs of flexible branch chains "UPU" branches and "RPR" branches. The bridge displacement amplifier is the core component of the two pairs of flexible branches, among which the "RPR" flexible branch component is composed of two flexible R hinges, two wedge blocks and a bridge displacement amplifier; the "UPU" flexible branch component is composed of two flexible U hinges, two wedge blocks and a bridge displacement amplifier. The displacement output by the piezoelectric actuator is amplified several times through the bridge displacement amplifier to achieve a larger stroke of the moving platform. The translational positioning resolution of most existing two-translation and one-rotation positioning platforms can reach 0.05mm, and the rotational positioning resolution is only 0.5mrad, while the translational positioning resolution of most two-translation and one-rotation flexible parallel mechanisms can reach 0.1um, and the rotational positioning resolution can reach 1μrad. At the same time, the moving pair of the traditional flexible parallel mechanism is directly replaced by a driver, and the U pair is composed of two rotating pairs superimposed, with a small stroke and a large volume. The large-stroke and high-precision spatial two-motion-one-rotation compliant parallel positioning system in the present invention combines the advantages of the traditional two-translation-one-rotation three-degree-of-freedom parallel mechanism with the advantages of the compliant mechanism. In addition, after adding a bridge displacement amplifier and adopting a new U-hinge, the positioning accuracy of the mechanism can reach the micron level, the stroke can reach several times the stroke of the driver, and the size of the mechanism becomes more compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system in space provided by an embodiment of the present invention.

[0025] Figure 2 It is a schematic diagram of the "RPR" flexible branch chain provided by an embodiment of the present invention.

[0026] Figure 3 It is a schematic diagram of a "UPU" flexible branch chain provided in an embodiment of the present invention.

[0027] Figure 4 Schematic diagram of a wedge block provided by an embodiment of the present invention.

[0028] Figure 5 It is a schematic diagram of a flexible R hinge provided in an embodiment of the present invention.

[0029] Figure 6 Schematic diagram of a driving device provided by an embodiment of the present invention.

[0030] Figure 7 It is a schematic diagram of a flexible U-hinge provided in an embodiment of the present invention.

[0031] In the figure: 1. moving platform; 2. flexible R hinge; 3. flexible U hinge; 4. piezoelectric actuator; 5. bridge displacement amplifier; 6. wedge block; 7. fixed platform. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The present invention adopts a driving component composed of a bridge displacement amplifier and a piezoelectric actuator as the moving pair of the flexible parallel mechanism, so that a large-stroke and high-precision spatial two-movement and one-rotation flexible parallel positioning system can achieve a larger stroke. At the same time, a compact flexible U-hinge is adopted, so that the flexible mechanism can meet the miniaturization characteristics while also achieving high-precision requirements.

[0034] like Figure 1 As shown, the large-stroke and high-precision spatial two-movement and one-rotation flexible parallel positioning system provided by an embodiment of the present invention includes: a moving platform, a flexible U-hinge, a wedge block, a bridge displacement amplifier, a piezoelectric actuator, a wedge block, and a flexible R-hinge.

[0035] The large-stroke and high-precision spatial two-movement and one-rotation flexible parallel positioning system mainly consists of three parts: a moving platform, a base platform, and two pairs of different branch chains, one of which is composed of a flexible R hinge, a bridge displacement amplifier, and a wedge block, and the other branch chain is composed of a flexible U hinge, a bridge displacement amplifier, and a wedge block.

[0036] The large-stroke and high-precision spatial two-movement and one-rotation flexible parallel positioning system is driven by a total of four bridge-type displacement amplifiers in parallel. A single bridge-type displacement amplifier has a built-in piezoelectric actuator. The actuator telescopic rod actively retracts and extends to push the amplifier to move, and the force transmission movement enables the flexible hinges in the "UPU" branch and the "RPR" branch to move as required. Finally, the moving platform can perform three-degree-of-freedom motions with two translations and one rotation according to the required micron-level accuracy and path.

[0037] The large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system has a bridge displacement amplifier on the piezoelectric actuator. When the mechanism branch chain is driven, if there is no bridge displacement amplifier, the displacement of the moving platform of the compliant mechanism is smaller than the displacement of the driver, resulting in a smaller stroke of the moving platform. At the same time, according to the properties of the compliant hinge, the R-type hinge is similar to a leaf spring and will not cause stress concentration. Under the same size, only the U-type hinge will cause stress concentration. Without the U pair used in this chapter, the mechanism will produce buckling motion under the action of a large force, which will cause the entire mechanism to fail to operate normally.

[0038] The specific installation steps of the large-stroke, high-precision spatial two-movement and one-rotation compliant parallel positioning system provided by the embodiment of the present invention are as follows:

[0039] (1) A base platform is fixed to the isolation platform by bolts;

[0040] (2) Two pairs of flexible branch components are symmetrically divided into 360° angles and evenly distributed on the plane of the fixed platform. The U pair in the "UPU" branch and the R pair in the "RPR" branch are fixed to the platform base by bolts and connected from bottom to top. The rotating axis of the flexible R hinge connected to the fixed platform is parallel to the side of the fixed platform, and the axis of the end face of the flexible U hinge connected to the fixed platform is parallel to the side of the fixed platform.

[0041] (3) The four wedge-shaped blocks close to the plane of the fixed platform have their lower sides facing the inner side of the platform and their higher sides facing the outer side of the platform and the four hinges whose bottom surfaces are connected to the fixed platform are respectively welded and fixed.

[0042] (4) The lower end surfaces of the four bridge displacement amplifiers are matched with the other end surface of the wedge block that is close to the fixed platform and has not yet been assembled and are connected by bolts, and the bolts are unscrewed from one side of the bridge displacement amplifier to the other side of the wedge block.

[0043] (5) The ends of the four piezoelectric actuators are respectively matched with the end faces of the bosses without grooves of the bridge displacement amplifier and connected by bolts. The bolts are screwed from the amplifier side to the driver side at their respective corresponding positions to generate a pre-tightening force at the contact end.

[0044] (6) The output end of the piezoelectric actuator is aligned with the center of the boss groove on the other side of the bridge displacement amplifier, and is an interference fit.

[0045] (7) The upper end surface of the bridge displacement amplifier is assembled with four wedge blocks close to the moving platform and connected with bolts, and the bolts are screwed from one side of the bridge displacement amplifier to the wedge blocks. The higher side of the wedge block close to the moving platform faces the inside of the platform, and the lower side faces the outside of the platform.

[0046] (8) The unmatched sides of the four wedge blocks close to the moving platform are respectively welded and fixed to the unassembled R pair in the RPR branch chain and the unassembled U pair in the UPU branch chain.

[0047] (9) The lower plane of the moving platform and the two pairs of flexible hinges close to the moving platform are installed and assembled in sequence. The threaded end face of the moving platform matches with the upper end faces of each flexible hinge, and they are connected from top to bottom with bolts. The rotating shaft of the flexible R hinge connected to the fixed platform is parallel to the side of the fixed platform, and the axis of the end face of the flexible U hinge connected to the fixed platform is parallel to the side of the fixed platform.

[0048] (10) The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system, characterized in that: The invention comprises an upper platform, a lower platform, a piezoelectric actuator and a bridge displacement amplifier; the piezoelectric actuator is installed in the bridge displacement amplifier; the upper platform and the lower platform are connected by four groups of flexible branch components; the bridge displacement amplifier is a core part of the flexible branch components; the four piezoelectric actuators of the four groups of flexible branch components realize the movement of the moving platform in three degrees of freedom, namely, two movements in the y direction and the z direction and one rotation in the x direction; The four sets of flexible branch components include two pairs of "UPU" flexible branches and two pairs of "RPR" flexible branches; One pair of compliant branches "UPU" consists of a bridge displacement amplifier I, two U-shaped hinges and two wedge blocks I, and the other compliant branch "RPR" consists of a bridge displacement amplifier II, two R-shaped hinges and two wedge blocks II; Two pairs of flexible branch components are symmetrically divided into 360° angles and evenly distributed on the upper plane of the fixed platform; and in the "UPU" flexible branch, the flexible U hinge I, the first wedge block I, the bridge displacement amplifier I, the second wedge block I, and the flexible U hinge II are connected in series from bottom to top; in the "RPR" flexible branch, the flexible R hinge I, the first wedge block II, the bridge displacement amplifier II, the second wedge block II, and the flexible R hinge II are connected in series from bottom to top.

2. The large-stroke, high-precision, two-movement-one-rotation compliant parallel positioning system of claim 1, characterized in that: The flexible U-hinge is a compact flexible Hooke's hinge, which consists of two pairs of orthogonal semi-biaxial compliant hinges, and the two rotation axes of the U-hinge intersect at the orthogonal point.

3. The large-stroke, high-precision, two-movement-one-rotation compliant parallel positioning system of claim 1, characterized in that: The fixed platform and two pairs of flexible hinges close to the fixed platform are installed and assembled in sequence, and the end surface of the fixed platform with threads is matched with the lower end surface of each flexible hinge, and bolts are used to connect them from bottom to top.

4. The large-stroke, high-precision, two-movement-one-rotation compliant parallel positioning system of claim 3, characterized in that: The rotating shaft of the flexible R hinge connected to the fixed platform is parallel to the side of the fixed platform, and the axis of the end face of the flexible U hinge connected to the fixed platform is parallel to the side of the fixed platform.

5. The large-stroke, high-precision, two-movement-one-rotation compliant parallel positioning system of claim 1, characterized in that: The four wedge-shaped blocks close to the fixed platform plane have their lower sides facing the inner side of the platform and their higher sides facing the outer side of the platform; the four wedge-shaped blocks close to the moving platform plane have their lower sides facing the outer side of the platform and their higher sides facing the inner side of the platform.

6. The large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system of claim 1, characterized in that: One end of the 8 wedge blocks close to the bridge displacement amplifier is fixed to the two end faces of the amplifier and connected with bolts. The bolts are screwed from one side of the amplifier to one side of the flexible hinge. The other end faces of the wedge blocks are welded and fixed to the flexible U hinge and the flexible R hinge.

7. The large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system of claim 1, characterized in that: The flexible unit of the bridge displacement amplifier is composed of 8 leaf springs, and for assembly and positioning, the two input ends are set as bosses, one side of the boss has a groove to facilitate the fixation of the driver output end.

8. The large-stroke, high-precision, two-movement-one-rotation compliant parallel positioning system of claim 1, characterized in that: The four piezoelectric actuators are placed in the four bridge displacement amplifiers respectively; the ends of the piezoelectric actuators match with the boss end faces of the bridge displacement amplifiers and are connected by bolts, and the bolts are screwed from one side of the bridge displacement amplifier at the corresponding positions toward the driver side; the output end of the piezoelectric actuator is horizontally placed at the center point of the groove on the other end face of the bridge displacement amplifier.

9. The large-stroke, high-precision, two-movement, one-rotation compliant parallel positioning system of claim 1, characterized in that: The lower plane of the moving platform and the two pairs of flexible hinges close to the moving platform are installed and assembled in sequence. The threaded end face of the moving platform cooperates with the upper end faces of each flexible hinge, and bolts are used to connect them from top to bottom. The rotating shaft of the flexible R hinge connected to the moving platform is parallel to the side of the moving platform where it is located, and the axis of the end face of the flexible U hinge connected to the moving platform is parallel to the side of the moving platform where it is located.

Images