Weak-coupling six-degree-of-freedom parallel mechanism and construction method thereof

Abstract

The invention provides a weak coupling six-degree-of-freedom parallel mechanism and a construction method thereof, and relates to the technical field of parallel mechanisms. The mechanism comprises a movable platform, a fixed platform and six motion branch chains connecting the movable platform and the fixed platform; the six movement branch chains comprise the first movement branch chain, the second movement branch chain, the third movement branch chain, the fourth movement branch chain, the fifth movement branch chain and the sixth movement branch chain, the fifth movement branch chain and the first movement branch chain are the same in structure, and the sixth movement branch chain and the second movement branch chain are the same in structure. When the first moving pair, the fourth rotating pair, the eighth rotating pair, the fifth moving pair, the sixth moving pair and the eighteenth rotating pair are driving pairs, the moving platform realizes six-degree-of-freedom movement of three movements and three rotations; the weak coupling six-degree-of-freedom parallel mechanism construction method has the advantages of being high in rigidity, high in bearing capacity, simple in motion control, large in working space and the like, meanwhile, the good motion decoupling performance is achieved, and motion control and trajectory planning are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of parallel mechanisms, and particularly relates to a weakly coupled six-degree-of-freedom parallel mechanism and a construction method thereof. Background Art

[0002] Six-degree-of-freedom parallel mechanisms are widely used in fields such as automobiles, ships, airplanes, and aerospace equipment. However, the coupling of such mechanisms is relatively strong. The strong coupling will increase the complexity of its control system, reduce the motion accuracy of the mechanism, and restrict the application of the mechanism. Compared with strongly coupled mechanisms, weakly coupled mechanisms have advantages such as high motion accuracy, easy dynamic modeling, and simple control, and have good application prospects in the field of high-precision robots.

[0003] In most cases, the load-bearing and stiffness characteristics in the gravity direction have a great influence on the working performance of the mechanism. By decoupling the degrees of freedom in the gravity direction, the output accuracy of the mechanism in the gravity direction can be improved. However, the branches of traditional weakly coupled parallel mechanisms contain closed-loop units, with complex structures, and the stiffness and load-bearing capacity in the decoupled degree-of-freedom direction are poor. There is a lack of a high-precision weakly coupled six-degree-of-freedom parallel mechanism for large-load applications. Therefore, it is necessary to design a weakly coupled six-degree-of-freedom parallel mechanism and a construction method thereof. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a weakly coupled six-degree-of-freedom parallel mechanism and a construction method thereof. Through the mutual cooperation of six motion chains, each motion chain adopts a combined structure of rotating pairs, prismatic pairs, and cylindrical pairs, enabling the moving platform to achieve six-degree-of-freedom motion of three translations and three rotations, increasing the attitude working space of the mechanism, making it meet the requirements of large load and high precision, and at the same time having good motion decoupling, which is beneficial to motion control and trajectory planning.

[0005] The present invention provides a weakly coupled six-degree-of-freedom parallel mechanism, which includes a moving platform, a fixed platform, and six kinematic chains connecting the moving platform and the fixed platform. The six kinematic chains include a first kinematic chain, a second kinematic chain, a third kinematic chain, a fourth kinematic chain, a fifth kinematic chain, and a sixth kinematic chain. The first kinematic chain includes a first slide rail, a first connecting rod, a second connecting rod, a third connecting rod, and a first base. The first end of the first connecting rod is connected to the moving end of the first slide rail through a first cylindrical pair, the second end of the first connecting rod is connected to the first end of the second connecting rod through a first translational pair, the second end of the second connecting rod is connected to the first end of the third connecting rod through a first rotational pair, the second end of the third connecting rod is connected to the first base through a first universal hinge, and the first universal hinge includes a second rotational pair and a third rotational pair. The second kinematic chain includes a second slide rail, a slider, a fourth connecting rod, a fifth connecting rod, a sixth connecting rod, and a second base. The slider is connected to the second slide rail through a second translational pair, the slider is connected to the first end of the fourth connecting rod through a fourth rotational pair, the second end of the fourth connecting rod is connected to the first end of the fifth connecting rod through a third translational pair, the second end of the fifth connecting rod is connected to the first end of the sixth connecting rod through a fifth rotational pair, the second end of the sixth connecting rod is connected to the second base through a second universal hinge, and the second universal hinge includes a sixth rotational pair and a seventh rotational pair. The third kinematic chain includes a third base, a seventh connecting rod, an eighth connecting rod, a ninth connecting rod, and a fourth base. The top of the third base is connected to the first end of the seventh connecting rod through an eighth rotational pair, the second end of the seventh connecting rod is connected to the first end of the eighth connecting rod through a third universal hinge, the third universal hinge includes a ninth rotational pair and a tenth rotational pair, the second end of the eighth connecting rod is connected to the first end of the ninth connecting rod through a fourth translational pair, the second end of the ninth connecting rod is connected to the fourth base through a fourth universal hinge, and the fourth universal hinge includes an eleventh rotational pair and a twelfth rotational pair. The fourth kinematic chain includes a fifth base, a tenth connecting rod, an eleventh connecting rod, a twelfth connecting rod, and a sixth base. The top of the fifth base is connected to the first end of the tenth connecting rod through a fifth universal hinge, the fifth universal hinge includes a thirteenth rotational pair and a fourteenth rotational pair, the second end of the tenth connecting rod is connected to the first end of the eleventh connecting rod through a fifth translational pair, the second end of the eleventh connecting rod is connected to the first end of the twelfth connecting rod through a fifteenth rotational pair, the second end of the twelfth connecting rod is connected to the sixth base through a sixth universal hinge, and the sixth universal hinge includes a sixteenth rotational pair and a seventeenth rotational pair.

[0006] Preferably, the first slide rail, the second slide rail, the third base, and the fifth base are respectively connected to the fixed platform, and the first base, the second base, the fourth base, and the sixth base are respectively connected to the moving platform.

[0007] Preferably, the arrangement relationship of the axes of the kinematic pairs in the six kinematic branches is such that the axis of the first cylindrical pair is parallel to the axis of the third revolute pair, the axis of the first revolute pair coincides with the axis of the first prismatic pair, the axis of the first prismatic pair is perpendicular to the axis of the first cylindrical pair, and the axes of the first revolute pair, the second revolute pair, and the third revolute pair are perpendicular to each other.

[0008] Preferably, the axis of the fourth revolute pair is perpendicular to the axis of the third prismatic pair, the axis of the fifth revolute pair coincides with the axis of the third prismatic pair, the axes of the second prismatic pair, the fourth revolute pair, and the seventh revolute pair are parallel to each other, and the axes of the fifth revolute pair, the sixth revolute pair, and the seventh revolute pair are perpendicular to each other.

[0009] Preferably, the axes of the tenth revolute pair and the twelfth revolute pair form a reference plane. The structures of the fifth kinematic branch and the first kinematic branch are the same, and the structures of the sixth kinematic branch and the second kinematic branch are the same. The first kinematic branch and the fifth kinematic branch are symmetrically arranged with respect to the reference plane, and the second kinematic branch and the sixth kinematic branch are symmetric with respect to the reference plane.

[0010] Preferably, the axes of the eighth revolute pair, the ninth revolute pair, and the tenth revolute pair are perpendicular to each other, the axis of the ninth revolute pair is parallel to the axis of the eleventh revolute pair, the axis of the tenth revolute pair is parallel to the axis of the twelfth revolute pair, the axis of the fourth prismatic pair is perpendicular to both the axis of the tenth revolute pair and the axis of the eleventh revolute pair, the axes of the fifteenth revolute pair, the sixteenth revolute pair, and the seventeenth revolute pair are perpendicular to each other, the axis of the thirteenth revolute pair is parallel to the axis of the eighteenth revolute pair in the sixth kinematic branch, the thirteenth revolute pair is parallel to the second cylindrical pair in the fifth kinematic branch, the axis of the eighth revolute pair is perpendicular to the axis of the first cylindrical pair, and the axes of the fourth revolute pair, the tenth revolute pair, and the eighteenth revolute pair intersect.

[0011] Preferably, the first prismatic pair, the fourth revolute pair, the eighth revolute pair, the fifth prismatic pair, the sixth prismatic pair of the fifth kinematic branch, and the eighteenth revolute pair of the sixth kinematic branch are all driving pairs. By controlling the driving pairs, the moving platform can achieve six-degree-of-freedom motion of three translations and three rotations.

[0012] Preferably, the axes of the first cylindrical pair, the fourth revolute pair, and the fourteenth revolute pair are parallel to each other, the axis of the thirteenth revolute pair is parallel to the axis of the eighteenth revolute pair in the sixth kinematic branch, the thirteenth revolute pair is parallel to the second cylindrical pair in the fifth kinematic branch, the axis of the eighth revolute pair is perpendicular to the axis of the first cylindrical pair, and the axes of the fourth revolute pair, the tenth revolute pair, and the eighteenth revolute pair intersect.

[0013] Preferably, the third revolute pair axis, the seventh revolute pair axis, and the sixteenth revolute pair axis are parallel to each other. The seventeenth revolute pair axis is parallel to the nineteenth revolute pair axis in the sixth kinematic chain, and the seventeenth revolute pair axis is parallel to the twentieth revolute pair axis in the fifth kinematic chain. The third revolute pair axis, the twelfth revolute pair axis, and the twentieth revolute pair axis intersect.

[0014] In a second aspect, the present invention also provides a construction method for a weakly coupled six-degree-of-freedom parallel mechanism, including the following steps:

[0015] S1. Divide the six-degree-of-freedom parallel mechanism into a decoupling plane with 2T xy 1R z degrees of freedom and a coupling space with 2R xy 1T z degrees of freedom, such that the transmissive force screw acting on the moving platform by the planar degrees of freedom does not constrain the spatial degrees of freedom, and the translational degrees of freedom in the x and y directions are completely decoupled. The decoupling condition for the weakly coupled six-degree-of-freedom mechanism is:

[0016]

[0017] where (m = i, j where i = 1, 2, j = 3, 4, 5, 6) represents the transmissive force screws of each branch, represents the kinematic screw of translation in the x direction, represents the kinematic screw of translation in the y direction, represents the kinematic screw of rotation about the z axis, represents the kinematic screws of other degrees of freedom, T represents translation, and R represents rotation;

[0018] S2. According to the transmissive force screw of the i-th decoupling branch and the driving screw having a constant reciprocal product, find the form of the driving screw of the decoupling branch. The fact that the reciprocal product of the transmissive force screw of the decoupling branch and the driving screw is a constant is expressed as:

[0019] S3. According to the transmissive force screw of the i-th decoupling branch and the non-driving screw having a zero reciprocal product, find the form of the non-driving screw of the decoupling branch. The fact that the reciprocal product of the transmissive force screw of the decoupling branch and the non-driving screw is zero is expressed as:

[0020] S4. According to the transmissive force screw of the non-decoupling branch not constraining the decoupling kinematic screw Under the conditions, calculate the non - decoupled branch transmission force screw In the form of, the non - decoupled branch transmission force screw Does not constrain the decoupled motion screw The condition is expressed as:

[0021] S5. According to the non - decoupled branch transmission force screw In the form of, follow steps S2 and S3 to obtain the non - decoupled branch driving screw And the non - driving screw In the form of;

[0022] S6. Combine the driving screw Of the decoupled branch in step S2 with the non - driving screw Of the decoupled branch in step S3 to obtain a decoupled chain that meets the motion requirements; Combine the driving screw Of the non - decoupled branch and the non - driving screw Of the non - decoupled branch to obtain a non - decoupled chain that meets the motion requirements;

[0023] S7. Arrange each decoupled chain and non - decoupled chain to obtain a weakly - coupled six - degree - of - freedom parallel mechanism.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The weakly - coupled six - degree - of - freedom parallel mechanism of the present invention enables the moving platform to achieve six - degree - of - freedom motion of three translations and three rotations through the mutual cooperation of six motion chains. Each motion chain adopts a combined structure of revolute pairs, prismatic pairs and cylindrical pairs, and has the advantages of compact structure, high output precision, high stiffness, strong load - bearing capacity, simple motion control and large working space. At the same time, it also has good motion decoupling, which is beneficial to motion control and trajectory planning. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the overall structure schematic diagram of the weakly - coupled six - degree - of - freedom parallel mechanism of the present invention;

[0027] Figure 2 is the structure schematic diagram of the first motion chain in the present invention;

[0028] Figure 3 is the structure schematic diagram of the second motion chain in the present invention;

[0029] Figure 4 is the structure schematic diagram of the third motion chain in the present invention;

[0030] Figure 5 is the structure schematic diagram of the fourth motion chain in the present invention;

[0031] Figure 6 It is the flow chart of the construction method of the weakly coupled six-degree-of-freedom parallel mechanism of the present invention.

[0032] Main reference signs:

[0033] The first moving branch chain 1, the first slide rail 11, the first connecting rod 12, the second connecting rod 13, the third connecting rod 14, the first base 15, the first cylindrical pair C1, the first prismatic pair P1, the first revolute pair R1, the first universal hinge U1, the second revolute pair R2, the third revolute pair R3, the second moving branch chain 2, the second slide rail 21, the slider 22, the fourth connecting rod 23, the fifth connecting rod 24, the sixth connecting rod 25, the second base 26, the second prismatic pair P2, the fourth revolute pair R4, the third prismatic pair P3, the fifth revolute pair R5, the second universal hinge U2, the sixth revolute pair R6, the seventh revolute pair R7, the third moving branch chain 3, the third base 31, the seventh connecting rod 32, the eighth connecting rod 33, the ninth connecting rod 34, the fourth base 35, the eighth revolute pair R8, the third universal hinge U3, the ninth revolute pair R9, the tenth revolute pair R10, the fourth prismatic pair P4, the fourth universal hinge U4, the eleventh revolute pair R11, the twelfth revolute pair R12, the fourth moving branch chain 4, the fifth base 41, the tenth connecting rod 42, the eleventh connecting rod 43, the twelfth connecting rod 44, the sixth base 45, the fifth universal hinge U5, the thirteenth revolute pair R13, the fourteenth revolute pair R14, the fifth prismatic pair P5, the fifteenth revolute pair R15, the sixth universal hinge U6, the sixteenth revolute pair R16, the seventeenth revolute pair R17, the fifth moving branch chain 5, the sixth prismatic pair P6, the twentieth revolute pair R20, the sixth moving branch chain 6, the eighteenth revolute pair R18, the nineteenth revolute pair R19, the moving platform 7, the fixed platform 8. Specific embodiments

[0034] To elaborate on the technical content, structural features, achieved objectives and effects of the present invention, the following will be described in detail with reference to the accompanying drawings of the specification.

[0035] The weakly coupled six-degree-of-freedom parallel mechanism of the present invention, as Figure 1 shown, includes a moving platform 7, a fixed platform 8, and six moving branch chains connecting the moving platform 7 and the fixed platform 8. The six moving branch chains include the first moving branch chain 1, the second moving branch chain 2, the third moving branch chain 3, the fourth moving branch chain 4, the fifth moving branch chain 5, and the sixth moving branch chain 6. The fifth moving branch chain 5 has the same structure as the first moving branch chain 1, and the sixth moving branch chain 6 has the same structure as the second moving branch chain 2.

[0036] As Figure 2As shown in the figure, the first kinematic chain 1 includes a first slide rail 11, a first connecting rod 12, a second connecting rod 13, a third connecting rod 14, and a first base 15. The first end of the first connecting rod 12 is connected to the moving end of the first slide rail 11 through a first cylindrical pair C1. The second end of the first connecting rod 12 is connected to the first end of the second connecting rod 13 through a first sliding pair P1. The second end of the second connecting rod 13 is connected to the first end of the third connecting rod 14 through a first rotating pair R1. The second end of the third connecting rod 14 is connected to the first base 15 through a first universal hinge U1. The first universal hinge U1 includes a second rotating pair R2 and a third rotating pair R3. The axis of the first cylindrical pair C1 is parallel to the axis of the third rotating pair R3. The axis of the first rotating pair R1 coincides with the axis of the first sliding pair P1. The axis of the first sliding pair P1 is perpendicular to the axis of the first cylindrical pair C1. The axes of the first rotating pair R1, the second rotating pair R2, and the third rotating pair R3 are perpendicular to each other.

[0037] As Figure 3 shown in the figure, the second kinematic chain 2 includes a second slide rail 21, a slider 22, a fourth connecting rod 23, a fifth connecting rod 24, a sixth connecting rod 25, and a second base 26. The slider 22 is connected to the second slide rail 21 through a second sliding pair P2. The slider 22 is connected to the first end of the fourth connecting rod 23 through a fourth rotating pair R4. The second end of the fourth connecting rod 23 is connected to the first end of the fifth connecting rod 24 through a third sliding pair P3. The second end of the fifth connecting rod 24 is connected to the first end of the sixth connecting rod 25 through a fifth rotating pair R5. The second end of the sixth connecting rod 25 is connected to the second base 26 through a second universal hinge U2. The second universal hinge U2 includes a sixth rotating pair R6 and a seventh rotating pair R7. The axis of the fourth rotating pair R4 is perpendicular to the axis of the third sliding pair P3. The axis of the fifth rotating pair R5 coincides with the axis of the third sliding pair P3. The axes of the second sliding pair P2, the fourth rotating pair R4, and the seventh rotating pair R7 are parallel to each other. The axes of the fifth rotating pair R5, the sixth rotating pair R6, and the seventh rotating pair R7 are perpendicular to each other.

[0038] As Figure 4As shown in the figure, the third kinematic chain 3 includes a third base 31, a seventh link 32, an eighth link 33, a ninth link 34, and a fourth base 35. The top of the third base 31 is connected to the first end of the seventh link 32 through an eighth revolute pair R8. The second end of the seventh link 32 is connected to the first end of the eighth link 33 through a third universal joint U3. The third universal joint U3 includes a ninth revolute pair R9 and a tenth revolute pair R10. The second end of the eighth link 33 is connected to the first end of the ninth link 34 through a fourth prismatic pair P4. The second end of the ninth link 34 is connected to the fourth base 35 through a fourth universal joint U4. The fourth universal joint U4 includes an eleventh revolute pair R11 and a twelfth revolute pair R12. The axes of the eighth revolute pair R8, the ninth revolute pair R9, and the tenth revolute pair R10 are perpendicular to each other. The axis of the ninth revolute pair R9 is parallel to the axis of the eleventh revolute pair R11. The axis of the tenth revolute pair R10 is parallel to the axis of the twelfth revolute pair R12. The axis of the fourth prismatic pair P4 is perpendicular to the axes of the tenth revolute pair R10 and the eleventh revolute pair R11.

[0039] As Figure 5 shown in the figure, the fourth kinematic chain 4 includes a fifth base 41, a tenth link 42, an eleventh link 43, a twelfth link 44, and a sixth base 45. The top of the fifth base 41 is connected to the first end of the tenth link 42 through a fifth universal joint U5. The fifth universal joint U5 includes a thirteenth revolute pair R13 and a fourteenth revolute pair R14. The second end of the tenth link 42 is connected to the first end of the eleventh link 43 through a fifth prismatic pair P5. The second end of the eleventh link 43 is connected to the first end of the twelfth link 44 through a fifteenth revolute pair R15. The second end of the twelfth link 44 is connected to the sixth base 45 through a sixth universal joint U6. The sixth universal joint U6 includes a sixteenth revolute pair R16 and a seventeenth revolute pair R17. The axes of the fifteenth revolute pair R15, the sixteenth revolute pair R16, and the seventeenth revolute pair R17 are perpendicular to each other. The axis of the thirteenth revolute pair R13 is parallel to the axis of the seventeenth revolute pair R17. The axis of the fourteenth revolute pair R14 is parallel to the axis of the sixteenth revolute pair R16. The axis of the fifth prismatic pair P5 is perpendicular to the axis of the fourteenth revolute pair R14. The axis of the fifteenth revolute pair R15 coincides with the axis of the fifth prismatic pair P5.

[0040] As Figures 1 to 6As shown in the figure, the first slide rail 11, the second slide rail 21, the third base 31 and the fifth base 41 are respectively connected to the fixed platform 8, and the first base 15, the second base 26, the fourth base 35 and the sixth base 45 are respectively connected to the moving platform 7. The axes of the tenth revolute pair R10 and the twelfth revolute pair R12 form a reference plane. The first kinematic chain 1 and the fifth kinematic chain 5 are symmetrically arranged with respect to the reference plane, and the second kinematic chain 2 and the sixth kinematic chain 6 are symmetric with respect to the reference plane. The axis of the first cylindrical pair C1, the axis of the fourth revolute pair R4 and the axis of the fourteenth revolute pair R14 are parallel to each other. The axis of the thirteenth revolute pair R13 is parallel to the axis of the eighteenth revolute pair R18 in the sixth kinematic chain 6. The thirteenth revolute pair R13 is parallel to the second cylindrical pair C2 in the fifth kinematic chain 5. The axis of the eighth revolute pair R8 is perpendicular to the axis of the first cylindrical pair C1. The axes of the fourth revolute pair R4, the tenth revolute pair R10 and the eighteenth revolute pair R18 intersect. The axes of the third revolute pair R3, the seventh revolute pair R7 and the sixteenth revolute pair R16 are parallel to each other. The axis of the seventeenth revolute pair R17 is parallel to the axis of the nineteenth revolute pair R19 in the sixth kinematic chain 6. The axis of the seventeenth revolute pair R17 is parallel to the axis of the twentieth revolute pair R20 in the fifth kinematic chain 5. The axes of the third revolute pair R3, the twelfth revolute pair R12 and the twentieth revolute pair R20 intersect. The first prismatic pair P1, the fourth revolute pair R4, the eighth revolute pair R8, the fifth prismatic pair R5, the sixth prismatic pair P6 of the fifth kinematic chain 5 and the eighteenth revolute pair R18 of the sixth kinematic chain 6 are all driving pairs. By controlling each driving pair, the moving platform 7 realizes six-degree-of-freedom motion of three translations and three rotations.

[0041] As Figure 6 shown, a construction method for a weakly coupled six-degree-of-freedom parallel mechanism includes the following steps:

[0042] S1. Divide the six-degree-of-freedom parallel mechanism into a decoupling plane 2T xy 1R z degree of freedom and a coupling space 2R xy 1T z degree of freedom, so that the transmission force screw of the planar degree of freedom acting on the moving platform does not restrict the spatial degree of freedom, and the translational degrees of freedom in the x and y directions are completely decoupled. The decoupling condition for the weakly coupled six-degree-of-freedom mechanism is:

[0043]

[0044] In the formula, (m = i, j where i = 1, 2, j = 3, 4, 5, 6) represents the transmission force screws of each branch, represents the motion screw of translational motion in the x direction, represents the motion screw of translational motion in the y direction, represents the motion screw of rotational motion in the z direction, The kinematic screws representing other degrees of freedom, T represents translation, and R represents rotation.

[0045] S2. According to the transmission force screw of the i-th decoupling branch and the driving screw having a constant reciprocal product, the driving screw of the decoupling branch is obtained in the form. The transmission force screw of the decoupling branch and the driving screw having a constant reciprocal product is expressed as:

[0046] S3. According to the transmission force screw of the i-th decoupling branch and the non-driving screw having a zero reciprocal product, the non-driving screw of the decoupling branch is obtained in the form. The transmission force screw of the decoupling branch and the non-driving screw having a zero reciprocal product is expressed as:

[0047] S4. According to the condition that the transmission force screw of the non-decoupling branch does not constrain the decoupling kinematic screw $i, the form of the transmission force screw of the non-decoupling branch is obtained. The condition that the transmission force screw of the non-decoupling branch does not constrain the decoupling kinematic screw $i is expressed as:

[0048] S5. According to the form of the transmission force screw of the non-decoupling branch , following steps S2 and S3, the driving screw and the non-driving screw of the non-decoupling branch are obtained in the form.

[0049] S6. The driving screw of the decoupling branch in step S2 is combined with the non-driving screw of the decoupling branch in step S3 to obtain a decoupling link chain that meets the motion requirements; the driving screw of the non-decoupling branch and the non-driving screw of the non-decoupling branch in step S5 are combined to obtain a non-decoupling link chain that meets the motion requirements.

[0050] S7. The decoupling link chains and non-decoupling link chains are arranged to obtain a weakly coupled six-degree-of-freedom parallel mechanism.

[0051] The construction method of the weak-coupling six-degree-of-freedom parallel mechanism of the present invention enables the moving platform 7 to achieve six-degree-of-freedom motion of three translations and three rotations through the mutual cooperation of six kinematic chains. Each kinematic chain adopts a combined structure of revolute pairs, prismatic pairs and cylindrical pairs, and has the advantages of compact structure, high output precision, high stiffness, strong load-bearing capacity, simple motion control and large working space. At the same time, it also has good motion decoupling, which is beneficial to motion control and trajectory planning.

[0052] The embodiments described above are only used to describe the preferred embodiments of the present invention, rather than to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A weakly-coupled six-degree-of-freedom parallel mechanism, characterized in that, It includes a moving platform, a fixed platform, and six kinematic chains connecting the moving platform and the fixed platform. The six kinematic chains include a first kinematic chain, a second kinematic chain, a third kinematic chain, a fourth kinematic chain, a fifth kinematic chain, and a sixth kinematic chain; The first kinematic chain includes a first slide rail, a first connecting rod, a second connecting rod, a third connecting rod, and a first base. The first end of the first connecting rod is connected to the moving end of the first slide rail through a first cylindrical pair, the second end of the first connecting rod is connected to the first end of the second connecting rod through a first moving pair, the second end of the second connecting rod is connected to the first end of the third connecting rod through a first rotating pair, the second end of the third connecting rod is connected to the first base through a first universal hinge, and the first universal hinge includes a second rotating pair and a third rotating pair; The second kinematic chain includes a second slide rail, a slider, a fourth connecting rod, a fifth connecting rod, a sixth connecting rod, and a second base. The slider is connected to the second slide rail through a second moving pair, the slider is connected to the first end of the fourth connecting rod through a fourth rotating pair, the second end of the fourth connecting rod is connected to the first end of the fifth connecting rod through a third moving pair, the second end of the fifth connecting rod is connected to the first end of the sixth connecting rod through a fifth rotating pair, the second end of the sixth connecting rod is connected to the second base through a second universal hinge, and the second universal hinge includes a sixth rotating pair and a seventh rotating pair; The third kinematic chain includes a third base, a seventh connecting rod, an eighth connecting rod, a ninth connecting rod, and a fourth base. The top of the third base is connected to the first end of the seventh connecting rod through an eighth rotating pair, the second end of the seventh connecting rod is connected to the first end of the eighth connecting rod through a third universal hinge, the third universal hinge includes a ninth rotating pair and a tenth rotating pair, the second end of the eighth connecting rod is connected to the first end of the ninth connecting rod through a fourth moving pair, the second end of the ninth connecting rod is connected to the fourth base through a fourth universal hinge, and the fourth universal hinge includes an eleventh rotating pair and a twelfth rotating pair; The fourth kinematic chain includes a fifth base, a tenth connecting rod, an eleventh connecting rod, a twelfth connecting rod, and a sixth base. The top of the fifth base is connected to the first end of the tenth connecting rod through a fifth universal hinge, the fifth universal hinge includes a thirteenth rotating pair and a fourteenth rotating pair, the second end of the tenth connecting rod is connected to the first end of the eleventh connecting rod through a fifth moving pair, the second end of the eleventh connecting rod is connected to the first end of the twelfth connecting rod through a fifteenth rotating pair, the second end of the twelfth connecting rod is connected to the sixth base through a sixth universal hinge, and the sixth universal hinge includes a sixteenth rotating pair and a seventeenth rotating pair.

2. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The first slide rail, the second slide rail, the third base, and the fifth base are respectively connected to the fixed platform, and the first base, the second base, the fourth base, and the sixth base are respectively connected to the moving platform.

3. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, characterized in that, The layout relationship of the axes of the kinematic pairs in the six kinematic chains is such that the axis of the first cylindrical pair is parallel to the axis of the third revolute pair, the axis of the first revolute pair coincides with the axis of the first prismatic pair, the axis of the first prismatic pair is perpendicular to the axis of the first cylindrical pair, and the axes of the first revolute pair, the second revolute pair, and the third revolute pair are mutually perpendicular.

4. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The axis of the fourth revolute pair is perpendicular to the axis of the third prismatic pair, the axis of the fifth revolute pair coincides with the axis of the third prismatic pair, the axes of the second prismatic pair, the fourth revolute pair, and the seventh revolute pair are mutually parallel, and the axes of the fifth revolute pair, the sixth revolute pair, and the seventh revolute pair are mutually perpendicular.

5. The weakly coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The axes of the tenth revolute pair and the twelfth revolute pair form a reference plane. The fifth kinematic chain and the first kinematic chain have the same structure. The sixth kinematic chain and the second kinematic chain have the same structure. The first kinematic chain and the fifth kinematic chain are symmetrically arranged with respect to the reference plane, and the second kinematic chain and the sixth kinematic chain are symmetric with respect to the reference plane.

6. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The axes of the eighth revolute pair, the ninth revolute pair, and the tenth revolute pair are mutually perpendicular. The axis of the ninth revolute pair is parallel to the axis of the eleventh revolute pair. The axis of the tenth revolute pair is parallel to the axis of the twelfth revolute pair. The axis of the fourth prismatic pair is perpendicular to both the axis of the tenth revolute pair and the axis of the eleventh revolute pair. The axes of the fifteenth revolute pair, the sixteenth revolute pair, and the seventeenth revolute pair are mutually perpendicular. The axis of the thirteenth revolute pair is parallel to the axis of the seventeenth revolute pair. The axis of the fourteenth revolute pair is parallel to the axis of the sixteenth revolute pair. The axis of the fifth prismatic pair is perpendicular to the axis of the fourteenth revolute pair. The axis of the fifteenth revolute pair coincides with the axis of the fifth prismatic pair.

7. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, characterized in that The first prismatic pair, the fourth revolute pair, the eighth revolute pair, the fifth prismatic pair, the sixth prismatic pair of the fifth kinematic chain, and the eighteenth revolute pair of the sixth kinematic chain are all driving pairs. By control, the moving platform realizes six-degree-of-freedom motion of three translations and three rotations.

8. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The axes of the first cylindrical pair, the fourth revolute pair, and the fourteenth revolute pair are mutually parallel. The axis of the thirteenth revolute pair is parallel to the axis of the eighteenth revolute pair in the sixth kinematic chain. The thirteenth revolute pair is parallel to the second cylindrical pair in the fifth kinematic chain. The axis of the eighth revolute pair is perpendicular to the axis of the first cylindrical pair. The axes of the fourth revolute pair, the tenth revolute pair, and the eighteenth revolute pair intersect.

9. The weakly-coupled six-degree-of-freedom parallel mechanism according to claim 1, wherein The axes of the third revolute pair, the seventh revolute pair, and the sixteenth revolute pair are mutually parallel. The axis of the seventeenth revolute pair is parallel to the axis of the nineteenth revolute pair in the sixth kinematic chain. The axis of the seventeenth revolute pair is parallel to the axis of the twentieth revolute pair in the fifth kinematic chain. The axes of the third revolute pair, the twelfth revolute pair, and the twentieth revolute pair intersect.

10. A construction method of the weakly-coupled six-degree-of-freedom parallel mechanism according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Divide the six-degree-of-freedom parallel mechanism into a decoupling plane of 2T xy 1R z degrees of freedom and a coupling space of 2R xy 1T z degrees of freedom, such that the transmission force screw of the planar degrees of freedom acting on the moving platform does not constrain the spatial degrees of freedom, and the translational degrees of freedom in the x and y directions are completely decoupled. The decoupling condition for the weakly coupled six-degree-of-freedom mechanism is as follows: wherein, $ Tm (m = i, j where i = 1, 2, j = 3, 4, 5, 6) represents the transmission force screw of each branch, $1 represents the motion screw of translation in the x direction, $2 represents the motion screw of translation in the y direction, $3 represents the motion screw of rotation in the z direction, $4, $5, $6 represent the motion screws of other degrees of freedom, T represents translation, and R represents rotation; S2. According to the transmission force screw of the $i$-th decoupling branch Ti and the driving screw ai with a constant reciprocal product, find the form of the driving screw of the decoupling branch ai . The transmission force screw of the decoupling branch Ti and the driving screw ai with a constant reciprocal product is expressed as: S3. According to the transmission force screw of the i-th decoupling branch Ti and the non-driving screw bi whose reciprocal product is zero, find the form of the non-driving screw bi of the decoupling branch. The fact that the reciprocal product of the transmission force screw Ti of the decoupling branch and the non-driving screw bi is zero is expressed as: S4. According to the non-decoupled branch transmission force screw Tj Without restricting the decoupling motion screw $i$, find the non-decoupled branch transmission force screw Tj In the form of, the non-decoupled branch transmission force screw Tj Without restricting the decoupling motion screw $i$ is expressed as: S5. According to the form of the transmission force screw of the non-decoupled branch Tj , the driving screw ci of the non-decoupled branch and the non-driving screw di of the non-decoupled branch can be obtained according to steps S2 and S3; S6. Combine the driving helix of the decoupling branch in step S2 ai with the non-driving helix of the decoupling branch in step S3 bi to obtain a decoupling branch chain that meets the motion requirements; Combine the driving helix of the non-decoupling branch in step S5 ci and the non-driving helix of the non-decoupling branch di to obtain a non-decoupling branch chain that meets the motion requirements; S7. Arrange each decoupling chain and non-decoupling chain to obtain a weakly coupled six-degree-of-freedom parallel mechanism.

Images