Six-degree-of-freedom fully decoupled series-parallel mechanism containing closed-loop unit and construction method thereof

Abstract

The present invention belongs to the technical field of parallel mechanisms and provides a six-degree-of-freedom fully decoupled serial-parallel mechanism containing closed-loop units, including a 2R parallel mechanism and a 3T1R parallel mechanism. The 2R parallel mechanism includes a first moving platform, a first fixed platform, and a first mechanism branch disposed between the first moving platform and the first fixed platform. The 3T1R parallel mechanism includes a second moving platform, a second fixed platform, and a second mechanism branch disposed between the second moving platform and the second fixed platform, wherein the first fixed platform is connected to the second moving platform via the second mechanism branch. Based on screw theory, the present invention adopts a method of constructing closed-loop units by decoupling sub-mechanisms. The overall parallel mechanism is split into multiple sub-parallel mechanisms for design based on the motion characteristics of the degrees of freedom. The branches contain closed-loop units to achieve independent output of force and torque in the X, Y, and Z directions of the moving platform. The present invention also provides a method for constructing a six-degree-of-freedom fully coupled parallel mechanism, simplifying the method and process for designing a fully coupled parallel mechanism.

Description

Technical Field

[0001] The present invention belongs to the technical field of parallel mechanisms, and in particular relates to a six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit and a construction method thereof. Background Art

[0002] With the rapid development of robotics technology, robots are increasingly widely used in many industries. The operating environment of robots is ever-changing, and higher requirements are placed on the robot's mechanical configuration. Currently, there are two main types of robot mechanisms: parallel mechanisms and serial mechanisms. Among them, the serial mechanism has a large working space and a simple structure, but has low rigidity and large cumulative errors, making it unsuitable for high-precision tasks. Compared with the serial mechanism, the parallel mechanism has the advantages of small cumulative errors, high precision, good dynamic response, and large load-bearing capacity. The serial-parallel mechanism combines the advantages of both serial and parallel mechanisms. It has a large working space, compact structure, and good dynamic response characteristics. It has broad application prospects in aerospace, machine tools, and mobile robots.

[0003] Existing serial-parallel mechanisms consist of two mechanisms connected in series, resulting in weaker load-bearing capacity than parallel mechanisms. Furthermore, most existing serial-parallel mechanisms exhibit strong coupling. While serial-parallel mechanisms are widely used in many fields, there is a lack of six-degree-of-freedom, fully decoupled serial-parallel mechanisms with closed-loop units that can be applied in heavy-duty industrial applications and possess high load-bearing capacity. Therefore, it is necessary to propose a six-degree-of-freedom, fully decoupled serial-parallel mechanism with closed-loop units and a method for its construction. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a six-degree-of-freedom fully decoupled serial-parallel mechanism containing closed-loop units and a construction method thereof. Based on the spiral theory, a method of constructing closed-loop units separately by decoupling sub-mechanisms is adopted. The overall parallel mechanism is split into multiple sub-parallel mechanisms for design according to the motion characteristics of the degrees of freedom. The branches contain closed-loop units, and the rotational degrees of freedom and the mobile degrees of freedom are completely decoupled, realizing independent output of forces and torques in the X, Y, and Z directions of the moving platform. It has both large load-bearing capacity and decoupling characteristics, and has the advantages of simple control and higher output accuracy.

[0005] The present invention provides a six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit, which includes a 2R parallel mechanism and a 3T1R parallel mechanism. The second moving platform of the 3T1R parallel mechanism is connected to the first fixed platform of the 2R parallel mechanism. The 2R parallel mechanism includes a first moving platform, a first fixed platform and a first mechanism branch provided between the first moving platform and the first fixed platform. The first mechanism branch includes a first motion branch, a second motion branch, a third motion branch, a fourth motion branch and a fifth motion branch. The fourth motion branch has the same structure as the first motion branch and is an RPU configuration. The fifth motion branch has the same structure as the second motion branch and is UPR configuration, the third motion branch is RR configuration, the fourth motion branch and the first motion branch are symmetrically arranged about the seventh rotational secondary axis, and the fifth motion branch and the second motion branch are symmetrically arranged about the eighth rotational secondary axis, so as to realize the rotation of the first moving platform around the X direction and the Y direction; the first motion branch includes a first articulated seat, a first connecting rod, a first sleeve and a second articulated seat, the first articulated seat is connected to the first end of the first connecting rod through a first rotational pair, the second end of the first connecting rod is inserted into the first sleeve and connected to the first sleeve through a first moving pair, and the bottom end of the first sleeve is connected to the second through a first universal joint. The second motion branch comprises a third articulated seat, a second connecting rod, a second sleeve and a fourth articulated seat, the third articulated seat is connected to the first end of the second connecting rod through a second universal joint, the second end of the second connecting rod is inserted into the second sleeve and is connected to the second sleeve through a second moving pair, the second sleeve is connected to the fourth articulated seat through a sixth rotation pair, the third motion branch comprises a fifth articulated seat, a third connecting rod and a sixth articulated seat, the fifth articulated seat is connected to the first end of the third connecting rod through a seventh rotation pair, and the second end of the third connecting rod is connected to the sixth articulated seat through an eighth rotation pair; the 3T1R parallel mechanism The invention comprises a second moving platform, a second fixed platform and a second mechanism branch provided between the second moving platform and the second fixed platform, wherein the second mechanism branch comprises a sixth motion branch, a seventh motion branch, an eighth motion branch, a ninth motion branch and a tenth motion branch, wherein the sixth motion branch, the seventh motion branch, the ninth motion branch and the tenth motion branch have the same configuration and are all RPPP configurations, the ninth motion branch and the sixth motion branch are symmetrically arranged about a ninth moving secondary axis, and the seventh motion branch and the tenth motion branch are symmetrically arranged about a seventh moving secondary axis, so as to realize translation of the second moving platform along the X direction, the Y direction and the Z direction and rotation about the Z direction;The sixth kinematic branch includes a first connecting member, a fourth connecting rod, a fourth sleeve, a first slide rail, and a first connecting frame. The first connecting member is connected to the first end of the fourth connecting rod via a ninth rotational pair. The second end of the fourth connecting rod is connected to the fourth sleeve via a third rotational pair. The fourth sleeve is connected to the first connecting frame via a fifth and sixth rotational pairs, respectively. The fifth and sixth rotational pairs are symmetrical about the axis of the third rotational pair. The first connecting frame is connected to the first slide rail via a fourth rotational pair. The eighth kinematic branch includes a second slide rail, a fifth connecting rod, a sixth connecting rod, a seventh connecting rod, and a third slide rail. The second slide rail is connected to the first end of the fifth connecting rod via a seventh rotational pair. The second end of the fifth connecting rod is connected to the first end of the sixth connecting rod via an eighth rotational pair. The second end of the sixth connecting rod is connected to the first end of the seventh connecting rod via a tenth rotational pair. The second end of the seventh connecting rod is connected to the third slide rail via a ninth rotational pair.

[0006] Preferably, the first articulated seat, the third articulated seat and the fifth articulated seat in the first mechanism branch are all connected to the first moving platform, and the second articulated seat, the fourth articulated seat and the sixth articulated seat in the first mechanism branch are all connected to the first fixed platform.

[0007] Preferably, the first connecting member and the second slide rail in the second mechanism branch are connected to the second movable platform, and the first slide rail and the third slide rail in the second mechanism branch are connected to the second fixed platform.

[0008] Preferably, the first universal joint includes a second rotation pair and a third rotation pair, the second rotation pair axis is perpendicular to the third rotation pair axis, the second universal joint includes a fourth rotation pair and a fifth rotation pair, the fourth rotation pair axis is perpendicular to the fifth rotation pair axis.

[0009] Preferably, the axis relationship between the moving pairs in the 2R parallel mechanism is: the first rotation secondary axis is perpendicular to the first moving secondary axis, the first moving secondary axis is perpendicular to the third rotation secondary axis, the fifth rotation secondary axis is perpendicular to the second moving secondary axis, the second moving secondary axis is perpendicular to the sixth rotation secondary axis, the seventh rotation secondary axis is perpendicular to the eighth rotation secondary axis, the first rotation secondary axis, the third rotation secondary axis, and the fourth rotation secondary axis are parallel to the seventh rotation secondary axis, and the second rotation secondary axis, the fifth rotation secondary axis, and the sixth rotation secondary axis are parallel to the eighth rotation secondary axis.

[0010] Preferably, the axis relationship between the moving pairs in the 3T1R parallel mechanism is: the ninth rotation secondary axis is perpendicular to the third moving secondary axis, the ninth rotation secondary axis and the fifth moving secondary axis are parallel to the sixth moving secondary axis, the fifth moving secondary axis and the sixth moving secondary axis are respectively perpendicular to the fourth moving secondary axis, the seventh moving secondary axis is perpendicular to the eighth moving secondary axis, the seventh moving secondary axis is perpendicular to the ninth moving secondary axis, the eighth moving secondary axis is collinear with the tenth rotation secondary axis, the fourth moving secondary axis is parallel to the ninth moving secondary axis, the fourth moving secondary axis is perpendicular to the tenth moving secondary axis, the ninth rotation secondary axis is parallel to the eleventh rotation secondary axis, and the ninth rotation secondary axis is perpendicular to the seventh moving secondary axis.

[0011] In a second aspect, the present invention further provides a method for constructing a six-degree-of-freedom fully decoupled serial-parallel mechanism including a closed-loop unit, which comprises the following steps:

[0012] S1. Based on the degree of freedom and decoupling requirements of the mechanism, the complete decoupling condition is proposed, in which the reciprocal product of the branch transmission force spiral matrix and the output motion spiral matrix of the 3T1R parallel mechanism and the 2R parallel mechanism is a diagonal matrix, and the transmission force spiral form of the mechanism motion branch is determined;

[0013] S2, according to the force transmission spiral in the same branch chain Ti With drive screw $ ai The condition that the reciprocal product is a non-zero constant is used to find the driving spiral of the i-th branch kinematic chain;

[0014] S3, according to the transmission force spiral $ Ti In the same branch chain, except for the driving spiral ai External non-driven spiral ki The inverse characteristics determine the non-driving helix of the i-th branch ki ;

[0015] S4, according to the driving motion spiral $ ai and non-driven spirals ki The type of branch is sorted according to the different order of branch connectivity and kinematic pairs, and the i-th basic decoupled kinematic branch is synthesized;

[0016] S5. Combining the closed-loop unit construction criteria with the complete decoupling condition of the sub-mechanism, construct the i-th redundant drive branch chain that is completely consistent with the basic decoupling branch chain structure and is driven synchronously. Construct a closed-loop unit containing the basic decoupling branch chain without destroying the decoupling characteristics of the mechanism.

[0017] S6. Let i take different values ​​and repeat steps S2-S5 to obtain m basic decoupling branches and m redundant drive branches;

[0018] S7. Combine the m basic decoupled motion branches and m redundant drive branches of the designed planar sub-parallel mechanism and spatial sub-parallel mechanism to obtain two rotation sub-mechanisms and three movement and one rotation sub-mechanisms. Connect the two sub-mechanisms in series to obtain a six-degree-of-freedom fully decoupled series-parallel mechanism.

[0019] Preferably, the complete decoupling condition of the 3T1R parallel mechanism in step S1 is:

[0020]

[0021] Where $ Ti (i=1,2,3,4) is the force transmission spiral of the i-th branch, $ j (j=1, 2, 3, 4) is the output motion spiral of the j-th branch.

[0022] Preferably, the complete decoupling condition of the 2R parallel mechanism in step S1 is:

[0023]

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

[0025] The six-degree-of-freedom fully decoupled serial-parallel mechanism containing closed-loop units of the present invention and the construction method thereof are based on the screw theory and adopt the method of constructing closed-loop units separately by decoupling sub-mechanisms. The overall parallel mechanism is split into multiple sub-parallel mechanisms for design according to the motion characteristics of the degrees of freedom. The branches contain closed-loop units, and the rotational degree of freedom and the mobile degree of freedom are completely decoupled, realizing independent output of forces and torques in the X, Y, and Z directions of the moving platform. It has both large load-bearing capacity and decoupling characteristics, and has the advantages of simple control and higher output accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the whole six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit of the present invention;

[0027] Figure 2 Schematic diagram of the 2R mechanism in the six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit of the present invention;

[0028] Figure 3 Schematic diagram of the first kinematic branch in the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit of the present invention;

[0029] Figure 4 Schematic diagram of the second kinematic branch in the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit of the present invention;

[0030] Figure 5 Schematic diagram of the third kinematic branch in the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit of the present invention;

[0031] Figure 6 Schematic diagram of a 3T1R parallel mechanism of a six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit according to the present invention;

[0032] Figure 7a and Figure 7b Schematic diagram of the sixth kinematic branch in the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit of the present invention;

[0033] Figure 8 Schematic diagram of the eighth kinematic branch in the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit of the present invention;

[0034] Figure 9 The figure is a flow chart of a construction method of a six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit according to the present invention.

[0035] Main reference numerals:

[0036] 2R parallel mechanism 1, first moving platform 11, first fixed platform 15, first motion branch 12, first articulated seat 121, first connecting rod 122, first sleeve 123, second articulated seat 124, second motion branch 13, third articulated seat 131, second connecting rod 132, second sleeve 133, fourth articulated seat 134, third motion branch 14, fifth articulated seat 141, third connecting rod 142, sixth articulated seat 143, fourth motion branch 16, fifth motion branch 17, 3T1R parallel mechanism 2, second moving platform 51, second fixed platform 53, sixth motion branch 52, first connecting member 521, fourth connecting rod 522, fourth sleeve 523, first slide rail 524, first connecting frame 525, seventh motion branch 54, eighth motion branch Dynamic branch chain 55, second sliding rail 551, fifth connecting rod 552, sixth connecting rod 553, seventh connecting rod 554, third sliding rail 555, ninth moving branch chain 56, tenth moving branch chain 57, first rotating pair R1, second rotating pair R2, third rotating pair R3, fourth rotating pair R4, fifth rotating pair R5, sixth rotating pair R6, seventh rotating pair R7, eighth rotating pair R8, ninth rotating pair R9, tenth rotating pair R10, eleventh rotating pair R11, first moving pair P1, second moving pair P2, third moving pair P3, fourth moving pair P4, fifth moving pair P5, sixth moving pair P6, seventh moving pair P7, eighth moving pair P8, ninth moving pair P9, tenth moving pair P10, first universal joint U1, second universal joint U2. DETAILED DESCRIPTION

[0037] To fully describe the technical content, structural features, objectives and effects of the present invention, the following is a detailed description with reference to the accompanying drawings.

[0038] The six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit of the present invention is as follows: Figure 1 As shown, it includes a 2R parallel mechanism 1 and a 3T1R parallel mechanism 2 , and the second moving platform 51 of the 3T1R parallel mechanism is connected to the first fixed platform 15 of the 2R parallel mechanism 1 .

[0039] like Figure 2 As shown, the 2R parallel mechanism 1 includes a first moving platform 11, a first fixed platform 15 and a first mechanism branch chain provided between the first moving platform 11 and the first fixed platform 15. The first mechanism branch chain includes a first motion branch chain 12, a second motion branch chain 13, a third motion branch chain 14, a fourth motion branch chain 16 and a fifth motion branch chain 17. The fourth motion branch chain 16 has the same structure as the first motion branch chain 12 and is both an RPU configuration. The fifth motion branch chain 17 has the same structure as the second motion branch chain 13 and is both a UPR configuration. The third motion branch chain 14 is an RR configuration. The fourth motion branch 16 and the first motion branch 12 are symmetrically arranged about the axis of the seventh rotation pair R7, and the fifth motion branch 17 and the second motion branch 13 are symmetrically arranged about the axis of the eighth rotation pair R8, so as to realize the rotation of the first moving platform 11 around the X direction and the Y direction; the first articulated seat 121, the third articulated seat 131, and the fifth articulated seat 141 in the first mechanism branch are all connected to the first moving platform 11, and the second articulated seat 124, the fourth articulated seat 134, and the sixth articulated seat 143 in the first mechanism branch are all connected to the first fixed platform 15.

[0040] like Figure 3 As shown, the first moving branch 12 includes a first articulated seat 121, a first connecting rod 122, a first sleeve 123 and a second articulated seat 124. The first articulated seat 121 is connected to the first end of the first connecting rod 122 through the first rotating pair R1. The second end of the first connecting rod 122 is inserted into the first sleeve 123 and is connected to the first sleeve 123 through the first moving pair P1. The bottom end of the first sleeve 123 is connected to the second articulated seat 124 through the first universal joint U1. The first universal joint U1 includes a second rotating pair R2 and a third rotating pair R3. The axis of the second rotating pair R2 is perpendicular to the axis of the third rotating pair R3.

[0041] like Figure 4 As shown, the second moving branch 13 includes a third articulated seat 131, a second connecting rod 132, a second sleeve 133 and a fourth articulated seat 134. The third articulated seat 131 is connected to the first end of the second connecting rod 132 through a second universal joint U2. The second universal joint U2 includes a fourth rotating pair R4 and a fifth rotating pair R5. The axis of the fourth rotating pair R4 is perpendicular to the axis of the fifth rotating pair R5. The second end of the second connecting rod 132 is inserted into the second sleeve 133 and is connected to the second sleeve 133 through the second moving pair P2. The second sleeve 133 is connected to the fourth articulated seat 134 through the sixth rotating pair R6.

[0042] like Figure 5As shown, the third motion branch 14 includes a fifth articulated seat 141, a third connecting rod 142 and a sixth articulated seat 143. The fifth articulated seat 141 is connected to the first end of the third connecting rod 142 through the seventh rotation pair R7, and the second end of the third connecting rod 142 is connected to the sixth articulated seat 143 through the eighth rotation pair R8.

[0043] The axis relationship between the moving pairs in the 2R parallel mechanism 1 is: the axis of the first rotating pair R1 is perpendicular to the axis of the first moving pair P1, the axis of the first moving pair P1 is perpendicular to the axis of the third rotating pair R3, the axis of the fifth rotating pair R5 is perpendicular to the axis of the second moving pair P2, the axis of the second moving pair P2 is perpendicular to the axis of the sixth rotating pair R6, the axis of the seventh rotating pair R7 is perpendicular to the axis of the eighth rotating pair R8, the axis of the first rotating pair R1, the axis of the third rotating pair R3, the axis of the fourth rotating pair R4 are parallel to the axis of the seventh rotating pair R7, and the axis of the second rotating pair R2, the axis of the fifth rotating pair R5, the axis of the sixth rotating pair R6 are parallel to the axis of the eighth rotating pair R8.

[0044] like Figure 6 As shown, the 3T1R parallel mechanism 2 includes a second moving platform 51, a second fixed platform 53 and a second mechanism branch provided between the second moving platform 51 and the second fixed platform 53. The second mechanism branch includes a sixth motion branch 52, a seventh motion branch 54, an eighth motion branch 55, a ninth motion branch 56 and a tenth motion branch 57. The sixth motion branch 52, the seventh motion branch 54, the ninth motion branch 56 and the tenth motion branch 57 have the same configuration and are all RPPP configurations. The ninth motion branch 56 and the sixth motion branch 52 are symmetrically arranged about the axis of the ninth moving pair P9, and the seventh motion branch 54 and the tenth motion branch 57 are symmetrically arranged about the axis of the seventh moving pair P7, so as to realize the translation of the second moving platform 51 along the X direction, the Y direction and the Z direction and the rotation around the Z direction. The first connecting member 521 and the second slide rail 551 in the second mechanism branch are connected to the second moving platform 51, and the first slide rail 524 and the third slide rail 555 in the second mechanism branch are connected to the second fixed platform 53.

[0045] Figure 7a and Figure 7b As shown, the sixth moving branch 52 includes a first connecting member 521, a fourth connecting rod 522, a fourth sleeve 523, a first slide rail 524 and a first connecting frame 525. The first connecting member 521 is connected to the first end of the fourth connecting rod 522 through the ninth rotating pair R9, the second end of the fourth connecting rod 522 is connected to the fourth sleeve 523 through the third moving pair P3, the fourth sleeve 523 is connected to the first connecting frame 525 through the fifth moving pair P5 and the sixth moving pair P6 respectively, the fifth moving pair P5 and the sixth moving pair P6 are symmetrical about the axis of the third moving pair P3, and the first connecting frame 525 is connected to the first slide rail 524 through the fourth moving pair P4.

[0046] like Figure 8 As shown, the eighth motion branch 55 includes a second slide rail 551, a fifth link 552, a sixth link 553, a seventh link 554 and a third slide rail 555. The second slide rail 551 is connected to the first end of the fifth link 552 through the seventh moving pair P7, the second end of the fifth link 552 is connected to the first end of the sixth link 553 through the eighth moving pair P8, the second end of the sixth link 553 is connected to the first end of the seventh link 554 through the tenth rotation pair R10, and the second end of the seventh link 554 is connected to the third slide rail 555 through the ninth moving pair P9.

[0047] The axis relationships between the kinematic pairs in the 3T1R parallel mechanism 2 are as follows: the axis of the ninth rotation pair R9 is perpendicular to the axis of the third mobile pair P3; the axis of the ninth rotation pair R9, the axis of the fifth mobile pair P5, and the axis of the sixth mobile pair P6 are parallel; the axes of the fifth mobile pair P5 and the sixth mobile pair P6 are respectively perpendicular to the axis of the fourth mobile pair P4. The axis of the seventh mobile pair P7 is perpendicular to the axis of the eighth mobile pair P8; the axis of the seventh mobile pair P7 is perpendicular to the axis of the ninth mobile pair P9; the axis of the eighth mobile pair P8 is collinear with the axis of the tenth rotation pair R10; the axis of the fourth mobile pair P4 is parallel to the axis of the ninth mobile pair P9; the axis of the fourth mobile pair P4 is perpendicular to the axis of the tenth mobile pair P10; the axis of the ninth rotation pair R9 is parallel to the axis of the eleventh rotation pair R11; and the axis of the ninth rotation pair R9 is perpendicular to the axis of the seventh mobile pair P7.

[0048] The following is a further description of the six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit and its construction method in conjunction with the embodiments of the present invention:

[0049] like Figure 9 As shown, the construction method of a six-degree-of-freedom fully decoupled series-parallel mechanism including a closed-loop unit includes the following steps:

[0050] S1. Based on the mechanism's degrees of freedom and decoupling requirements, the complete decoupling condition is proposed, in which the reciprocal product of the branch transmission force spiral matrix and the output motion spiral matrix of the 3T1R parallel mechanism and the 2R parallel mechanism is a diagonal matrix, and the transmission force spiral form of the mechanism's motion branch is determined.

[0051] The complete decoupling conditions of the 3T1R parallel mechanism are:

[0052]

[0053] Where $ Ti (i=1,2,3,4) is the force transmission spiral of the i-th branch, $ j (j=1, 2, 3, 4) is the output motion spiral of the j-th branch.

[0054] The complete decoupling condition of the 2R parallel mechanism is:

[0055]

[0056] S2, according to the force transmission spiral in the same branch chain Ti With drive screw $ ai Under the condition that the reciprocal product is a non-zero constant, find the driving screw of the i-th branch kinematic chain.

[0057] S3, according to the transmission force spiral $ Ti In the same branch chain, except for the driving spiral ai External non-driven spiral ki The inverse characteristics determine the non-driving helix of the i-th branch ki .

[0058] S4, according to the driving motion spiral $ ai and non-driven spirals ki According to the different sorting of branch connectivity and kinematic pairs, the i-th basic decoupled kinematic branch is synthesized.

[0059] S5. Combining the closed-loop unit construction criteria with the complete decoupling conditions of the sub-mechanisms, construct the i-th redundant drive branch that is completely consistent with the basic decoupling branch structure and driven synchronously. Construct a closed-loop unit containing the basic decoupling branch without destroying the decoupling characteristics of the mechanism.

[0060] S6. Let i take different values ​​and repeat steps S2-S5 to obtain m basic decoupling branches and m redundant drive branches.

[0061] S7. Combine the m basic decoupled motion branches and m redundant drive branches of the designed planar sub-parallel mechanism and spatial sub-parallel mechanism to obtain two rotation sub-mechanisms and three movement and one rotation sub-mechanisms. Connect the two sub-mechanisms in series to obtain a six-degree-of-freedom fully decoupled series-parallel mechanism.

[0062] The six-degree-of-freedom fully decoupled serial-parallel mechanism containing closed-loop units of the present invention and the construction method thereof are based on the screw theory and adopt a method of constructing closed-loop units separately by decoupling sub-mechanisms. The overall parallel mechanism is split into multiple sub-parallel mechanisms for design according to the motion characteristics of the degrees of freedom. The branches contain closed-loop units, and the rotational degrees of freedom and the mobile degrees of freedom are completely decoupled, realizing independent output of forces and torques in the X, Y, and Z directions of the moving platform. It has both large load-bearing capacity and decoupling characteristics, and has the advantages of simple control and higher output accuracy.

[0063] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit, characterized in that: It includes a 2R parallel mechanism and a 3T1R parallel mechanism, wherein the second moving platform of the 3T1R parallel mechanism is connected to the first fixed platform of the 2R parallel mechanism. The 2R parallel mechanism includes a first moving platform, a first fixed platform, and a first mechanism branch provided between the first moving platform and the first fixed platform. The first mechanism branch includes a first motion branch, a second motion branch, a third motion branch, a fourth motion branch, and a fifth motion branch. The fourth motion branch has the same structure as the first motion branch and is an RPU configuration. The fifth motion branch has the same structure as the second motion branch and is a UPR configuration. The third motion branch is an RR configuration. The fourth motion branch is symmetrically arranged with the first motion branch about the seventh rotation secondary axis, and the fifth motion branch is symmetrically arranged with the second motion branch about the eighth rotation secondary axis, so as to realize the rotation of the first moving platform around the X direction and the Y direction. The first motion branch includes a first articulated seat, a first connecting rod, a first sleeve and a second articulated seat, the first articulated seat is connected to the first end of the first connecting rod through a first rotating pair, the second end of the first connecting rod is inserted in the first sleeve and connected to the first sleeve through a first moving pair, and the bottom end of the first sleeve is connected to the second articulated seat through a first universal joint; the second motion branch includes a third articulated seat, a second connecting rod, a second sleeve and a fourth articulated seat, the third articulated seat is connected to the first end of the second connecting rod through a second universal joint, the second end of the second connecting rod is inserted in the second sleeve and connected to the first sleeve through a first moving pair The second movable pair is connected to the second sleeve, and the second sleeve is connected to the fourth articulated seat via a sixth rotational pair. The third kinematic branch includes a fifth articulated seat, a third connecting rod, and a sixth articulated seat. The fifth articulated seat is connected to the first end of the third connecting rod via a seventh rotational pair, and the second end of the third connecting rod is connected to the sixth articulated seat via an eighth rotational pair. The first universal joint includes a second rotational pair and a third rotational pair, and the axis of the second rotational pair is perpendicular to the axis of the third rotational pair. The second universal joint includes a fourth rotational pair and a fifth rotational pair, and the axis of the fourth rotational pair is perpendicular to the axis of the fifth rotational pair. The 3T1R parallel mechanism includes a second moving platform, a second fixed platform, and a second mechanism branch provided between the second moving platform and the second fixed platform. The second mechanism branch includes a sixth motion branch, a seventh motion branch, an eighth motion branch, a ninth motion branch, and a tenth motion branch. The sixth motion branch, the seventh motion branch, the ninth motion branch, and the tenth motion branch have the same configuration and are all RPPP configurations. The ninth motion branch and the sixth motion branch are symmetrically arranged about the ninth moving secondary axis, and the seventh motion branch and the tenth motion branch are symmetrically arranged about the seventh moving secondary axis, so as to realize the translation of the second moving platform along the X direction, the Y direction, and the Z direction and the rotation around the Z direction. The sixth motion branch includes a first connecting member, a fourth connecting rod, a fourth sleeve, a first slide rail and a first connecting frame, the first connecting member is connected to the first end of the fourth connecting rod through a ninth rotating pair, the second end of the fourth connecting rod is connected to the fourth sleeve through a third moving pair, the fourth sleeve is connected to the first connecting frame through a fifth moving pair and a sixth moving pair respectively, the fifth moving pair and the sixth moving pair are symmetrical about the axis of the third moving pair, and the first connecting frame is connected to the first slide rail through the fourth moving pair; the eighth motion branch includes a second slide rail, a fifth connecting rod, a sixth connecting rod, a seventh connecting rod and a third slide rail, the second slide rail is connected to the first end of the fifth connecting rod through the seventh moving pair, the second end of the fifth connecting rod is connected to the first end of the sixth connecting rod through the eighth moving pair, the second end of the sixth connecting rod is connected to the first end of the seventh connecting rod through the tenth rotating pair, and the second end of the seventh connecting rod is connected to the third slide rail through the ninth moving pair.

2. The six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit according to claim 1, characterized in that: The first articulated seat, the third articulated seat and the fifth articulated seat in the first mechanism branch are all connected to the first moving platform, and the second articulated seat, the fourth articulated seat and the sixth articulated seat in the first mechanism branch are all connected to the first fixed platform.

3. The six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit according to claim 1, characterized in that: The first connecting member and the second slide rail in the second mechanism branch are connected to the second movable platform, and the first slide rail and the third slide rail in the second mechanism branch are connected to the second fixed platform.

4. The six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit according to claim 1, characterized in that: The axis relationship between the moving pairs in the 2R parallel mechanism is as follows: the first rotation secondary axis is perpendicular to the first moving secondary axis, the first moving secondary axis is perpendicular to the third rotation secondary axis, the fifth rotation secondary axis is perpendicular to the second moving secondary axis, the second moving secondary axis is perpendicular to the sixth rotation secondary axis, the seventh rotation secondary axis is perpendicular to the eighth rotation secondary axis, the first rotation secondary axis, the third rotation secondary axis, and the fourth rotation secondary axis are parallel to the seventh rotation secondary axis, and the second rotation secondary axis, the fifth rotation secondary axis, and the sixth rotation secondary axis are parallel to the eighth rotation secondary axis.

5. The six-degree-of-freedom fully decoupled serial-parallel mechanism containing a closed-loop unit according to claim 1, characterized in that: The axis relationship between each moving pair in the 3T1R parallel mechanism is as follows: the ninth rotation secondary axis is perpendicular to the third moving secondary axis, the ninth rotation secondary axis and the fifth moving secondary axis are parallel to the sixth moving secondary axis, the fifth moving secondary axis and the sixth moving secondary axis are respectively perpendicular to the fourth moving secondary axis, the seventh moving secondary axis is perpendicular to the eighth moving secondary axis, the seventh moving secondary axis is perpendicular to the ninth moving secondary axis, the eighth moving secondary axis is collinear with the tenth rotation secondary axis, the fourth moving secondary axis is parallel to the ninth moving secondary axis, the fourth moving secondary axis is perpendicular to the tenth moving secondary axis, the ninth rotation secondary axis is parallel to the eleventh rotation secondary axis, and the ninth rotation secondary axis is perpendicular to the seventh moving secondary axis.

6. A method for constructing a six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit according to any one of claims 1 to 5, characterized in that: It includes the following steps: S1. Based on the degree of freedom and decoupling requirements of the mechanism, the complete decoupling condition is proposed, in which the reciprocal product of the branch transmission force spiral matrix and the output motion spiral matrix of the 3T1R parallel mechanism and the 2R parallel mechanism is a diagonal matrix, and the transmission force spiral form of the mechanism motion branch is determined; S2, according to the force transmission spiral in the same branch chain Ti With drive screw $ ai The condition that the reciprocal product is a non-zero constant is used to find the driving spiral of the i-th branch kinematic chain; S3, according to the transmission force spiral $ Ti In the same branch chain, except for the driving spiral ai External non-driven spiral ki The inverse characteristics determine the non-driving helix of the i-th branch ki ; S4, according to the driving motion spiral $ ai and non-driven spirals ki The type of branch is sorted according to the different order of branch connectivity and kinematic pairs, and the i-th basic decoupled kinematic branch is synthesized; S5. Combining the closed-loop unit construction criteria with the complete decoupling condition of the sub-mechanism, construct the i-th redundant drive branch chain that is completely consistent with the basic decoupling branch chain structure and is driven synchronously. Construct a closed-loop unit containing the basic decoupling branch chain without destroying the decoupling characteristics of the mechanism. S6. Let i take different values ​​and repeat steps S2-S5 to obtain m basic decoupling branches and m redundant drive branches; S7. Combine the m basic decoupled motion branches and m redundant drive branches of the designed planar sub-parallel mechanism and spatial sub-parallel mechanism to obtain two rotation sub-mechanisms and three movement and one rotation sub-mechanisms. Connect the two sub-mechanisms in series to obtain a six-degree-of-freedom fully decoupled series-parallel mechanism.

7. The method for constructing a six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit according to claim 6, characterized in that: The complete decoupling condition of the 3T1R parallel mechanism in step S1 is: ； Where $ Ti (i=1,2,3,4) is the force transmission spiral of the i-th branch, $ j (j=1,2,3,4) is the output motion spiral of the j-th branch.

8. The method for constructing a six-degree-of-freedom fully decoupled series-parallel mechanism containing a closed-loop unit according to claim 6, characterized in that: The complete decoupling condition of the 2R parallel mechanism in step S1 is: 。

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