Parallel robot mechanism based on metamorphic four-bar mechanism

Abstract

According to the parallel robot mechanism based on the metamorphic four-bar mechanism, the working state of the metamorphic parallel mechanism can be changed only through mode switching of the metamorphic four-bar mechanism, and any movement 3T, one-rotation-three-movement 1R3T, two-rotation-three-movement 2R3T and three-rotation-three-movement 3R3T in the space can be switched; the three branch chains are completely the same in structure and easy to manufacture, meanwhile, the system complexity is greatly reduced, and the three-branch-chain parallel mechanism can be applied to the industrial environment with the tail end posture requirement changing and is suitable for various application scenes.

Description

Technical Field

[0001] The invention relates to the technical field of robots, in particular to a parallel robot mechanism based on a metamorphic four-bar mechanism. Background Art

[0002] Parallel mechanisms are currently attracting much attention in the field of industrial robots due to their high precision, high stiffness, rapid response, and excellent load performance, and have been widely used in processing, automated production lines, motion simulators, and other application fields. As metamorphic mechanisms are gradually used in the field of robotics, the application of reconfigurable mechanisms based on metamorphic mechanisms that can freely switch motion modes according to changes in demand is also increasing. For example, the patent with publication number CN117484480A discloses a new type of symmetrical variable cell parallel mechanism that can add a rotating axis. By controlling the fourth rotating pair to move in the arc groove of the arc groove pin pair, the number of overlapping branch center points can be controlled to achieve switching of 1R2T (one rotation and two movements), 2R2T (two rotations and two movements), and 3R2T (three rotations and two movements), wherein R represents rotational movement and T represents translational movement; however, the degree of freedom of movement of the mechanism is 2T, that is, movement can only be achieved within a plane, and the fourth rotating pair 26 is moved in the arc groove of the arc groove pin pair 27 to control the position of the branch center point, thereby changing the working state of the mechanism. The mechanism is relatively complex, which affects the application scenario of the mechanism. Summary of the invention

[0003] In order to solve the problems of limited freedom of movement and complex control of existing metamorphic parallel mechanisms, the present invention provides a parallel robot mechanism based on a metamorphic four-bar mechanism, which can achieve spatial movement and has greater flexibility in position than the metamorphic four-bar mechanism. At the same time, the metamorphosis of the parallel mechanism is achieved through the bifurcation motion characteristics of the metamorphic four-bar mechanism, thereby reducing the complexity of the mechanism.

[0004] The technical solution of the present invention is as follows: a parallel robot mechanism based on a metamorphic four-bar mechanism, comprising: a fixed platform and a moving platform, wherein the fixed platform and the moving platform are connected in parallel via three branches of the same structure; Features: Each of the branch chains comprises: a cylindrical pair 1, a branch chain rotation pair, a variable cell four-bar mechanism and a cylindrical pair 2 which are connected in sequence; the cylindrical pair 1 is mounted on the fixed platform, and the cylindrical pair 2 is connected to the moving platform; The variable cell four-bar mechanism comprises: a universal joint first, a variable cell rotation joint first, a universal joint second and a variable cell rotation joint second; The four kinematic pairs are connected end to end by a connecting rod structure to form a quadrilateral, and the opposite sides of the quadrilateral are equal; the two universal joints are not directly connected, and the two rotating pairs are not directly connected; Each universal joint includes two mutually perpendicular rotating shafts m and n; the rotating shafts m and n are always kept perpendicular to the two connecting rods connected to the universal joint. The axis direction of the rotation axis of the first cylindrical pair and the rotation axis of the branch chain rotation pair are the same, and are always parallel to the fixed platform; The two parallel connecting rods in the metamorphic four-bar mechanism are connected to the branch chain rotation pair and the cylindrical pair 2 in the branch chain respectively, and the two connecting rods are respectively recorded as: frame 1 and frame 2; the universal joint rotating shaft that is perpendicular to the frame 1 and the frame 2 is the rotating shaft m; The frame connected to the branch chain rotating pair is parallel to the rotating shaft of the branch chain rotating pair; The rotation axis m of the universal joint connected to the second frame is coaxial with the rotation axis of the second cylindrical joint.

[0005] It is further characterized by: The angle between the cylindrical pair 2 and the upper end surface of the moving platform is denoted as angle a, and the value range of angle a is: 0° <a<90°; The cylindrical pair one on the three branch chains is a driving pair, and the input motion is realized by a motor; It also includes a branch link one; The fixed platform is rod-shaped, and a protruding connection block is provided on the side of the midpoint of the frame 1 away from the universal joint and the rotating joint; a sleeve is provided at one end of the branch chain link 1, and the sleeve is sleeved on the fixed platform to form the cylindrical joint 1; the other end of the branch chain link 1 is a U-shaped structure, and the U-shaped structure and the connection block of the frame 1 constitute the branch chain rotating joint; The rod-shaped fixed platform constitutes the rotation axis of the cylindrical pair 1 and is always parallel to the rotation axis of the branch chain rotating pair and the frame 1; The cylindrical pair 2 includes: a sleeve and a slide rod; one end of the sleeve is connected to the frame 2 and is coaxial with the rotation axis m of the universal joint connected to the frame 2; one end of the slide rod is inserted from the other end of the sleeve and movably installed in the inner cavity of the sleeve to form a cylindrical pair; the other end of the slide rod is fixedly connected to the moving platform.

[0006] The present application provides a parallel robot mechanism based on a metamorphic four-bar mechanism. The working state of the metamorphic parallel mechanism can be changed simply by switching the mode of the metamorphic four-bar mechanism. The mechanism can switch between any movement 3T, one turn and three shifts 1R3T, two turns and three shifts 2R3T, and three turns and three shifts 3R3T in space. The three branch chain structures in the present application are exactly the same and easy to manufacture. At the same time, the system complexity is greatly reduced. The mechanism can be used in industrial environments that require changes in the terminal posture and is suitable for various application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a structural diagram of the Pa mode of the metamorphic four-bar mechanism; Figure 2 It is the coaxial state of Pa mode; Figure 3 It is the transition state of the metamorphic four-bar mechanism; Figure 4 It is the Ra mode coaxial state 2; Figure 5 It is a structural diagram of the Ra mode of the variable cell four-bar mechanism; Figure 6 It is a schematic diagram of the overall structure of the 3T working mode of the present invention.

[0008] Figure 7 It is a structural schematic diagram of the 3T1R working mode of the present invention; Figure 8 It is a structural schematic diagram of the 3T2R working mode of the present invention; Fig. 9 It is a structural schematic diagram of the 3T3R working mode of the present invention; Fig.10 Schematic diagram of the branched chain structure.

[0009] In the figure, 1 is a fixed platform; 2 first branch chain; 21 first cylindrical pair 1; 22 first branch chain rotation pair; 23 first variable cell four-bar mechanism; 24 first cylindrical pair 2; 3 second branch chain; 31 second cylindrical pair 1; 32 second branch chain rotation pair; 33 second variable cell four-bar mechanism; 34 second cylindrical pair 2; 4 the third branch chain; 41 the third cylindrical pair 1; 42 the third branch chain rotation pair; 43 the third variable cell four-bar mechanism; 44 the third cylindrical pair 2; 5 moving platform; 51 connecting structure; 231 Frame 1; 232 Universal joint 1; 233 Rotation joint 1 for metamorphic cells; 234 Frame 2; 235 Universal joint 2; 236 Rotation joint 2 for metamorphic cells; 237 Frame 3; 238 Frame 4; 241 sleeve; 242 slide rod; 6 chain connecting rods one. DETAILED DESCRIPTION

[0010] like Figure 1 to Figure 10 As shown, the present application includes a parallel robot mechanism based on a metamorphic four-bar mechanism, which includes: a fixed platform 1 and a moving platform 5, and the fixed platform 1 and the moving platform 5 are connected in parallel through three branches with the same structure.

[0011] Each branch chain includes: a cylindrical pair 1, a branch chain rotating pair, a metamorphic four-bar mechanism, and a cylindrical pair 2 connected in sequence; the cylindrical pair 1 is installed on the fixed platform 1, and the cylindrical pair 2 is connected to the moving platform 5. The metamorphic four-bar mechanism includes: a universal pair 1, a rotating pair 1 for metamorphosis, a universal pair 2, and a rotating pair 2 for metamorphosis. The four kinematic pairs are sequentially connected by link structures at the head and tail to form a quadrilateral, and the opposite sides of the quadrilateral are equal; the two universal pairs are not directly connected, and the two rotating pairs are not directly connected. Each universal pair includes two mutually perpendicular rotating shafts m and n; the rotating shafts m and n are always perpendicular to the two connecting rods connected to the universal pair respectively. The axis directions of the rotating shaft of the cylindrical pair 1 and the rotating shaft of the branch chain rotating pair are the same and are always parallel to the fixed platform 1. The two mutually parallel connecting rods in the metamorphic four-bar mechanism are respectively connected to the branch chain rotating pair and the cylindrical pair 2 in the branch chain, and the two connecting rods are respectively denoted as: frame 1 and frame 2; the universal pair rotating shaft perpendicular to frame 1 and frame 2 is the rotating shaft m. The frame 1 connected to the branch chain rotating pair is parallel to the rotating shaft of the branch chain rotating pair. The rotating shaft m of the universal pair connected to frame 2 is coaxial with the rotating shaft of the cylindrical pair 2.

[0012] In the technical solution of this application, the moving platform 5 is provided with binding forces by three branch chains to realize motion. Specifically, when implemented, the included angle between the cylindrical pair 2 and the upper end face of the moving platform 5 is denoted as: included angle a, as Figure 6 shown. The value range of the included angle a is: 0° < a < 90°, ensuring that the binding force couples given by each branch chain to the moving platform are linearly independent, and further ensuring that the moving platform 5 can flexibly and accurately realize motions in all directions.

[0013] The first branch chain 2, the second branch chain 3, and the third branch chain 4 in this application have exactly the same structure. They are all CR(rPa)C branch chains, and the mode switching of the metamorphic parallel mechanism is completed by the mode switching of the metamorphic four-bar mechanism 23 in each branch chain. Among them, C represents a cylindrical pair and is the active driving pair of this mechanism, R represents a rotating pair, rPa represents a metamorphic four-bar mechanism, and the CR(rPa)C branch chain represents a branch chain sequentially connected in series in the order of cylindrical pair - rotating pair - metamorphic four-bar mechanism pair - cylindrical pair. As Figure 1 and Fig.10 shown, taking the first branch chain 2 as an example to illustrate the detailed structure of the branch chain and the metamorphic four-bar mechanism.

[0014] As Figure 1 shown, the first metamorphic four-bar mechanism 23 includes: a universal pair 1 232, a rotating pair 1 for metamorphosis 233, a universal pair 2 235, and a rotating pair 2 for metamorphosis 236 connected in sequence at the head and tail; the four kinematic pairs are connected by four connecting rods: frame 1 231, frame 2 234, frame 3 237, and frame 4 238 to form a quadrilateral, where the lengths of frame 1 231 and frame 2 234 forming the opposite sides are the same, and the lengths of frame 3 237 and frame 4 238 are the same.

[0015] Universal joint 1 232 and universal joint 235 are located at two ends of the diagonal line of the quadrilateral, and metamorphic rotation joint 1 233 and metamorphic rotation joint 2 236 are located at two ends of the diagonal line of the quadrilateral.

[0016] The universal joint 1 232 includes two mutually perpendicular rotating shafts m1 and n1; the universal joint 1 232 is connected to the frame 1 231 and the frame 3 237 respectively. During the movement, the rotating shaft n1 always remains perpendicular to the frame 3 237, and the rotating shaft m1 always remains perpendicular to the frame 1 231.

[0017] The universal joint 235 includes two mutually perpendicular rotating shafts m2 and n2; the universal joint 235 is connected to the frame 234 and the frame 4 238 respectively; during the movement, the rotating shaft n2 always remains perpendicular to the frame 4 238, and the rotating shaft m2 always remains perpendicular to the frame 2 234.

[0018] The metamorphic four-bar mechanism in the present application, denoted as rPa, can switch between two modes: a parallelogram mechanism (denoted as Pa) and an anti-parallelogram mechanism (denoted as Ra).

[0019] by Figure 1 The state shown is the initial state, in which the rotation axis n1 of the universal joint 232, the rotation axis of the metamorphic rotation joint 233, the rotation axis n2 of the universal joint 235 and the rotation axis of the metamorphic rotation joint 236 are parallel to each other; at the same time, the rotation axis m1 of the universal joint 232 and the rotation axis m2 of the universal joint 235 are located in the plane where the metamorphic four-bar mechanism 23 is located. At this time, the metamorphic four-bar mechanism is equivalent to a parallelogram mechanism Pa, which is equivalent to a moving pair. In the plane where the metamorphic four-bar mechanism is located, the frame 1 231 and the frame 2 234 can achieve relative position movement.

[0020] When the variable cell four-bar mechanism moves to the point where the rotation axis m1 of the universal joint 1 232 and the rotation axis m2 of the universal joint 235 are coaxial, as shown in FIG. Figure 2 The rotation axis u shown is the rotation axis formed by the coaxiality of m1 and m2; the first metamorphic four-bar mechanism 23 can rotate around this coaxial axis u. Once the mechanism starts to rotate around the rotation axis u, the rotation axis n1 of the universal joint 1 232, the rotation axis of the metamorphic rotation joint 1 233, the rotation axis n2 of the universal joint 235 and the rotation axis of the metamorphic rotation joint 2 236, these four axes no longer maintain a parallel relationship with each other, as shown in FIG. Figure 3 The metamorphic four-bar mechanism continues to rotate around this coaxial u until the four axes are parallel to each other again. In this state, m1 and m2 are coaxial u again, and the metamorphic four-bar mechanism becomes an antiparallelogram mechanism Ra, as shown in Figure 4 shown.

[0021] exist Figure 4In the state shown, the metamorphic four-bar mechanism is equivalent to a revolute pair, and the rotation axis v is a dynamic rotation axis, which passes through the intersection of the frame three 237 and the frame four 238 and is perpendicular to the plane where the metamorphic four-bar mechanism is located. When the frame one 231 is fixed, the frame two 234 can realize rotation in the plane where the metamorphic four-bar mechanism is located based on the rotation axis v, as shown in FIG. Figure 5 shown.

[0022] Metamorphosis four-bar mechanism 23 through Figure 1-Figure 5 The method shown completes the switching from mode Pa to mode Ra. The switching from mode Ra to mode Pa can be performed by Figure 1-5 The reverse process is completed.

[0023] like Fig.10 As shown, the first branch chain 2 includes: four kinematic pairs connected in sequence from bottom to top: a first cylinder pair 1 21, a first branch chain rotation pair 22, a first variable cell four-bar mechanism 23, and a first cylinder pair 24; the first cylinder pair 1 21 is installed on the fixed platform 1, and the first cylinder pair 24 is connected to the moving platform 5.

[0024] Each branch chain also includes a branch chain connecting rod 1. There are many ways to install the branch chain and the fixed platform. In this embodiment, the fixed platform 1 is set to a rod shape. A protruding connecting block 239 is set on the side of the midpoint of the frame 1 231 away from the universal joint 1 232 and the variable cell rotation joint 2 236. A sleeve is set at one end of the branch chain connecting rod 1 6, and the sleeve is sleeved on the fixed platform 1 to form the first cylindrical joint 1 21; the other end of the branch chain connecting rod 1 6 is a U-shaped structure, and the U-shaped structure and the connecting block 239 of the frame 1 231 form the first branch chain rotation joint 22.

[0025] The rod-shaped fixed platform 1 constitutes the rotation axis of the first cylindrical pair 21 and is always parallel to the rotation axis of the first branch chain rotating pair 22 and the frame 1 231.

[0026] The cylindrical pair is composed of a rotation pair and a translation pair, so it has two degrees of freedom. The cylindrical pair 1 and the cylindrical pair 2 in the present application can both realize the movement of two degrees of freedom, but the specific structures are different.

[0027] The cylindrical pair 2 includes: a sleeve and a slide rod. Fig.10 As shown, one end of the sleeve 241 is connected to the frame 234 and is coaxial with the rotating axis m2 of the universal joint 235 connected to the frame 234; one end of the slide rod 242 is inserted from the other end of the sleeve 241 and movably installed in the inner cavity of the sleeve 241 to form a cylindrical pair; the other end of the slide rod 242 is fixedly connected to the moving platform 5 through the connecting structure 51.

[0028] The axis directions of the rotation axis of the first cylindrical pair 21 and the rotation axis of the first branch chain rotation pair 22 are the same, and are always parallel to the fixed platform 1.

[0029] The frame 1 231 is parallel to the rotation axis of the first branch chain rotation pair 22. The rotation axis m2 of the universal joint 235 is coaxial with the rotation axis of the first cylindrical joint 24.

[0030] The cylindrical pair 1 on the three branches is the driving pair, and the input motion is realized by the motor. The driving motor of each branch drives the cylindrical pair 1 to rotate, and then the trend branch drives the moving platform to move; during the movement process, due to the mutual influence between the three branches, the cylindrical pair 1 of each branch will follow, that is, move on the moving platform 1.

[0031] When the first metamorphic four-bar mechanism 23 of the first branch chain 2, the second metamorphic four-bar mechanism 33 of the second branch chain 3, and the third metamorphic four-bar mechanism 43 of the third branch chain 4 are all in mode Pa, as shown in FIG. Figure 6 As shown, the degree of freedom of the moving platform 5 is 3T, and the moving platform 5 can move in any direction in the xyz space, that is, realize pure movement.

[0032] by Figure 6 Based on the state of, driven by the driving motor, the first cylindrical pair 21, the second cylindrical pair 31, and the third cylindrical pair 41 rotate at different angles with the rod-shaped fixed platform 1 as the axis, and the forces of the three parallel branches affect each other. Because of the existence of the first cylindrical pair 24, the universal joint 1 232 and the universal joint 235, the first variable cell four-bar mechanism 23 rotates and deforms from the Pa mode to the Ra mode.

[0033] When the first metamorphic four-bar mechanism 23 of the first branch chain 2 is in mode Ra, the second metamorphic four-bar mechanism 33 of the second branch chain 3 and the third metamorphic four-bar mechanism 43 of the third branch chain 4 are in mode Pa, as shown in FIG. Figure 7 As shown, the degree of freedom of the moving platform 5 is 1R3T, and the moving platform 5 can move in the xyz space and rotate in one dimension around the rotation axis l1. The rotation axis l1 of the moving platform 5 is perpendicular to the normal line p2 of the plane where the metamorphic four-bar mechanism of the second branch chain is located and perpendicular to the normal line p3 of the plane where the third metamorphic four-bar mechanism of the third branch chain is located.

[0034] When the first metamorphic four-bar mechanism 23 of the first branch chain 2 and the second metamorphic four-bar mechanism 33 of the second branch chain 3 are in mode Ra, and the third metamorphic four-bar mechanism 43 of the third branch chain 4 is in mode Pa, as shown in FIG. Figure 8 As shown, the degree of freedom of the moving platform 5 is 2R3T, and the moving platform 5 can move in space and rotate in two dimensions. The moving platform 5 has two rotation axes l1 and l2, and the two linearly independent rotation axes l1 and l2 are both perpendicular to the normal line p3 of the plane where the third branched metamorphic four-bar mechanism is located.

[0035] When the second metamorphic four-bar mechanism 33 of the second branch chain 3 and the third metamorphic four-bar mechanism 43 of the third branch chain 4 are both in mode Ra, as shown in FIG. Fig. 9As shown, the dynamic platform 5 has 3R3T degrees of freedom, and can move in space and perform three-dimensional rotation in space around any axis in space.

[0036] The parallel robot mechanism of the present application switches between the two modes of the traditional parallelogram mechanism and the anti-parallelogram mechanism by designing a new type of four-bar mechanism in the branch chain. The variable cell parallel mechanism formed based on this new variable cell four-bar mechanism can change the rotational freedom and realize the switching of four motion modes of 3T, 3T1R, 3T2R, and 3T3R. The three branch chains in the present application have the same structure and are symmetrically distributed, with balanced force and improved rigidity, which is conducive to the modularization and standardization of the design and convenient manufacturing. The dynamic platform in the present application can achieve three-dimensional rotation at most, and compared with the existing parallel robot mechanism, it can achieve more complex posture adjustment and movement. The present application utilizes the structural properties of the proposed new variable cell four-bar mechanism itself to switch the motion mode, which can not only achieve accurate motion mode switching, but also reduce the complexity of the system.

Claims

1. A parallel robot mechanism based on a metamorphic four-bar mechanism, comprising: A fixed platform and a movable platform, wherein the fixed platform and the movable platform are connected in parallel via three branch chains of the same structure; Features: Each of the branch chains comprises: a cylindrical pair 1, a branch chain rotation pair, a variable cell four-bar mechanism and a cylindrical pair 2 which are connected in sequence; the cylindrical pair 1 is mounted on the fixed platform, and the cylindrical pair 2 is connected to the moving platform; The variable cell four-bar mechanism comprises: a universal joint first, a variable cell rotation joint first, a universal joint second and a variable cell rotation joint second; The four kinematic pairs are connected end to end by a connecting rod structure to form a quadrilateral, and the opposite sides of the quadrilateral are equal; the two universal joints are not directly connected, and the two rotating pairs are not directly connected; Each universal joint includes two mutually perpendicular rotating shafts m and n; the rotating shafts m and n are always kept perpendicular to the two connecting rods connected to the universal joint. The axis direction of the rotation axis of the first cylindrical pair and the rotation axis of the branch chain rotation pair are the same, and are always parallel to the fixed platform; The two parallel connecting rods in the metamorphic four-bar mechanism are connected to the branch chain rotation pair and the cylindrical pair 2 in the branch chain respectively, and the two connecting rods are respectively recorded as: frame 1 and frame 2; the universal joint rotating shaft that is perpendicular to the frame 1 and the frame 2 is the rotating shaft m; The frame connected to the branch chain rotating pair is parallel to the rotating shaft of the branch chain rotating pair; The rotation axis m of the universal joint connected to the second frame is coaxial with the rotation axis of the second cylindrical joint.

2. A parallel robot mechanism based on a metamorphic four-bar mechanism according to claim 1, characterized in that: The angle between the cylindrical pair 2 and the upper end surface of the moving platform is denoted as angle a, and the value range of angle a is: 0° <a<90°。 3. The parallel robot mechanism based on the metamorphic four-bar mechanism according to claim 1, characterized in that: The cylindrical pair on the three branch chains is a driving pair, and the input motion is realized by a motor.

4. The parallel robot mechanism based on the metamorphic four-bar mechanism according to claim 1, characterized in that: It also includes a branch link one; The fixed platform is rod-shaped, and a protruding connecting block is provided on the side of the midpoint of the frame one away from the universal joint and the rotating joint; a sleeve is provided at one end of the branch chain connecting rod one, and the sleeve is sleeved on the fixed platform to form the cylindrical joint one; the other end of the branch chain connecting rod one is a U-shaped structure, and the U-shaped structure and the connecting block of the frame one constitute the branch chain rotating joint.

5. A parallel robot mechanism based on a metamorphic four-bar mechanism according to claim 4, characterized in that: The rod-shaped fixed platform constitutes the rotation axis of the cylindrical pair 1 and is always parallel to the rotation axis of the branch chain rotating pair and the frame 1.

6. The parallel robot mechanism based on the metamorphic four-bar mechanism according to claim 1, characterized in that: The cylindrical pair 2 includes: a sleeve and a slide rod; one end of the sleeve is connected to the frame 2 and is coaxial with the rotation axis m of the universal joint connected to the frame 2; one end of the slide rod is inserted from the other end of the sleeve and movably installed in the inner cavity of the sleeve to form a cylindrical pair; the other end of the slide rod is fixedly connected to the moving platform.

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