A completely decoupled two-rotation and one-movement parallel mechanism

Abstract

The present invention provides a completely decoupled two-rotation-one-movement parallel mechanism, which has three degrees of freedom, namely, rotation in two directions and movement in one direction. When the first cylindrical pair in the first branch motion chain is input as an active pair alone, the movable platform has one rotational degree of freedom; when the first moving pair in the second branch motion chain is input as an active pair alone, the movable platform has another rotational degree of freedom; when the linear displacements of the first and second cylindrical pairs in the first branch motion chain and the third branch motion chain are simultaneously input as active pairs, and the input displacements are the same, the movable platform has one movement degree of freedom. The three branch motion chains of the parallel mechanism have a specific relationship in motion, and the velocity Jacobian matrix thereof is a triangular matrix, which has completely decoupled kinematic characteristics. Through the arrangement relationship of the three branch motion chains, the carrying capacity of the parallel mechanism is improved, so that it has a good development prospect in the fields of robots, machine tools, aerospace, etc.

Description

Technical Field

[0001] The invention relates to the technical field of industrial robots, and in particular to a completely decoupled two-rotation-one-movement parallel mechanism. Background Art

[0002] The parallel mechanism connects the fixed platform and the moving platform through two or more branch chains to form a special multi-closed loop structure. As a new type of mechanism, the parallel mechanism has the characteristics of high precision, small cumulative error, large load capacity, and compact structure compared with the traditional series mechanism. It has been widely used in high-precision and cutting-edge technology fields such as industrial robots, parallel machine tools, and aerospace.

[0003] A low-DOF parallel robot mechanism refers to a robot mechanism with 2 to 5 DOF. Compared with a 6-DOF parallel robot mechanism, a low-DOF parallel robot mechanism has the advantages of higher stiffness, precision and load-bearing capacity. In recent years, it has become one of the hot spots in the field of mechanism research. In particular, a two-transfer and one-shift three-DOF parallel robot mechanism has good application prospects in practical applications due to its easy-to-implement motion control and trajectory planning. It can be applied to motion simulators, coordinate measuring machines, machining centers, etc. For this reason, domestic scholars have studied and designed many such mechanisms, but most of the existing parallel robot mechanisms still have problems such as strong motion coupling, small workspace, and difficult control. Summary of the invention

[0004] The purpose of the present invention is to provide a completely decoupled two-rotation and one-motion parallel mechanism to solve the problems of strong motion coupling, poor decoupling and small working space of the parallel mechanism existing in the prior art.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a completely decoupled two-rotation and one-movement parallel mechanism, including a fixed platform, a moving platform and three branch kinematic chains, the three branch kinematic chains are respectively a first branch kinematic chain, a second branch kinematic chain and a third branch kinematic chain, wherein:

[0006] The first branch kinematic chain includes a first cylindrical pair connected to the fixed platform at one end, a universal joint connected to the movable platform at one end, and a first rotating pair arranged therebetween, the two ends of the first rotating pair being connected to the first cylindrical pair and the universal joint through a first connecting rod and a second connecting rod respectively, and the axis of the first cylindrical pair, the axis of the first rotating pair, and the inner axis of the universal joint are arranged in parallel;

[0007] The second branch kinematic chain includes a first moving pair, a second rotating pair, a third rotating pair and a ball pair which are sequentially connected by a connecting rod, the free ends of the first moving pair and the ball pair are respectively connected to the fixed platform and the moving platform, and the axes of the second rotating pair and the third rotating pair are parallel;

[0008] The third branch kinematic chain includes a second cylindrical pair and a fourth rotation pair connected by a connecting rod, the free ends of the second cylindrical pair and the fourth rotation pair are respectively connected to the fixed platform and the movable platform, and the axes of the second cylindrical pair and the fourth rotation pair are located in the same plane and are arranged perpendicular to each other;

[0009] The first cylindrical pair, the second cylindrical pair and the first moving pair are all power input ends and are respectively connected to drive motors.

[0010] Furthermore, the axis of the second rotation pair, the axis of the fourth rotation pair and the outer axis of the universal joint are arranged in parallel.

[0011] Furthermore, the axis of the first cylindrical pair and the axis of the second cylindrical pair are arranged in parallel, and both axes are perpendicular to the axis of the fourth rotation pair.

[0012] Furthermore, a circular arc track matching with the first moving pair is provided on the fixed platform, and the axis of the second cylindrical pair is perpendicular to the plane where the circular arc track is located and passes through the center of the circular arc track.

[0013] Furthermore, the fourth revolving pair is located at the center of the moving platform, and the universal joint, the fourth revolving pair and the ball pair are sequentially arranged along the length direction of the moving platform and are distributed on the same straight line.

[0014] Furthermore, the second rotation pair is connected to the third rotation pair via a fourth connecting rod, and the free ends of the second rotation pair and the third rotation pair are connected to the first moving pair and the ball pair via a third connecting rod and a fifth connecting rod, respectively.

[0015] Furthermore, the second cylindrical pair and the fourth rotation pair are connected via a sixth connecting rod.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention has three degrees of freedom, namely, rotation in two directions and movement in one direction. When the first cylindrical pair in the first branch motion chain is input as an active pair alone, the movable platform has one degree of freedom of rotation; when the first moving pair in the second branch motion chain is input as an active pair alone, the movable platform has another degree of freedom of rotation; when the linear displacements of the first and second cylindrical pairs in the first branch motion chain and the third branch motion chain are simultaneously input as active pairs, and the input displacements are the same, the movable platform has one degree of freedom of movement. The three branch motion chains of the parallel mechanism have a specific relationship in motion, and their velocity Jacobian matrix is ​​a triangular matrix with completely decoupled kinematic characteristics. Through the arrangement relationship of the three branch motion chains, the carrying capacity of the parallel mechanism is improved, so that it has good development prospects in the fields of robots, machine tools, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1It is a schematic diagram of the overall structure of a completely decoupled two-rotation and one-movement parallel mechanism of the present invention;

[0018] Figure 2 It is a schematic diagram of the distribution of the universal joint, ball joint and the fourth rotation joint on the moving platform. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] A completely decoupled two-rotation-one-movement parallel mechanism, such as Figure 1 As shown, it includes a fixed platform 10 and a movable platform 20, and L1, L2, and L3 represent the first, second, and third branch motion chains respectively.

[0021] The first branch kinematic chain L1 includes a first cylindrical pair C11, a first rotation pair R12 and a universal joint U13, one end of the first cylindrical pair C11 and one end of the universal joint U13 are directly connected to the fixed platform 10 and the moving platform 20 respectively, and the first rotation pair R12 is connected to the other ends of the first cylindrical pair C11 and the universal joint U13 through the first connecting rod 1-1 and the second connecting rod 1-2 respectively. Among them, the axis of the first cylindrical pair C11, the axis of the first rotation pair R12 and the axis of the universal joint U13 connected to the second connecting rod 1-2, i.e., the inner axis, are parallel to each other.

[0022] The second branch kinematic chain L2 includes a first moving pair P21, a second rotating pair R22, a third rotating pair R23 and a ball pair S24. The first moving pair P21 and the ball pair S24 are directly connected to the fixed platform 10 and the moving platform 20 respectively, the second rotating pair R22 is connected to the first moving pair P21 and the third rotating pair R23 through the third connecting rod 2-1 and the fourth connecting rod 2-2 respectively, and the third rotating pair R23 is connected to the ball pair S24 through the fifth connecting rod 2-3. Among them, the axes of the second rotating pair R22 and the third rotating pair R23 are parallel.

[0023] The third branch kinematic chain L3 includes a second cylindrical pair C31 and a fourth rotation pair R32. The second cylindrical pair C31 and the fourth rotation pair R32 are respectively connected to the fixed platform 10 and the moving platform 20, and the fourth rotation pair R32 is connected to the second cylindrical pair C31 through the sixth connecting rod 3-1. The axis of the second cylindrical pair C31 and the axis of the fourth rotation pair R32 are in the same plane and perpendicular to each other.

[0024] To further optimize the present solution, the axes of the two rotation pairs in the second branch motion chain L2, the axis of the fourth rotation pair R32 in the third branch motion chain L3, and the axis of the universal joint U13 connected to the moving platform 20, i.e., the outer axis, are all arranged parallel to each other.

[0025] To further optimize the present solution, the axis of the first cylinder pair C11 is parallel to the axis of the second cylinder pair C31 and is perpendicular to the axis of the fourth rotation pair R32 in the third branch kinematic chain L3.

[0026] To further optimize this solution, the first moving pair P21 in the second branch motion chain L2 moves along the circular track, and the axis of the second cylindrical pair C31 in the third branch motion chain L3 is perpendicular to the plane of the circular track and passes through the center of the circular track.

[0027] To further optimize this solution, Figure 2 As shown, the universal joint U13 in the first branch motion chain L1 and the ball joint S24 in the second branch motion chain L2 are distributed on both sides of the moving platform 20, the fourth rotation joint R32 in the third branch motion chain L3 is located at the center of the moving platform 20, and the three are distributed on the same straight line.

[0028] In this embodiment, the kinematic pairs connected to the fixed platform 10 in the three branch kinematic chains are selected as active pairs, among which the first cylindrical pair C11 in the first branch kinematic chain L1 and the second cylindrical pair C31 in the third branch kinematic chain L3 both use linear displacement as the main input.

[0029] The control principle of the present invention is as follows: the active pair is driven by a servo motor, and the moving platform 20 is powered by three branch kinematic chains. The first drive motor drives the first cylindrical pair C11 in the first branch kinematic chain L1, so that the moving platform 20 rotates around the axis direction of the fourth rotation pair R32 in the third branch kinematic chain L3; the second drive motor drives the first moving pair P21 in the second branch kinematic chain L2, so that the moving platform 20 rotates around the axis direction of the second cylindrical pair C31 in the third branch kinematic chain L3. The first drive motor and the third drive motor drive the first cylindrical pair C11 in the first branch kinematic chain L1 and the second cylindrical pair C31 in the third branch kinematic chain L3, respectively, so that the moving platform 20 moves along the axis direction of the second cylindrical pair C31 in the third branch kinematic chain L3, thereby realizing the parallel mechanism with two rotations and one movement in space. Three degrees of freedom.

[0030] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A completely decoupled two-rotation-one-movement parallel mechanism, comprising a fixed platform, a moving platform and three branch kinematic chains, characterized in that: The three branch kinematic chains are the first branch kinematic chain, the second branch kinematic chain and the third branch kinematic chain, where: The first branch kinematic chain includes a first cylindrical pair connected to the fixed platform at one end, a universal joint connected to the movable platform at one end, and a first rotating pair arranged therebetween, the two ends of the first rotating pair being connected to the first cylindrical pair and the universal joint through a first connecting rod and a second connecting rod respectively, and the axis of the first cylindrical pair, the axis of the first rotating pair, and the inner axis of the universal joint are arranged in parallel; The second branch kinematic chain includes a first moving pair, a second rotating pair, a third rotating pair and a ball pair which are sequentially connected by a connecting rod, the free ends of the first moving pair and the ball pair are respectively connected to the fixed platform and the moving platform, and the axes of the second rotating pair and the third rotating pair are parallel; The third branch kinematic chain includes a second cylindrical pair and a fourth rotation pair connected by a connecting rod, the free ends of the second cylindrical pair and the fourth rotation pair are respectively connected to the fixed platform and the movable platform, and the axes of the second cylindrical pair and the fourth rotation pair are located in the same plane and are arranged perpendicular to each other; The first cylindrical pair, the second cylindrical pair and the first movable pair are all power input ends and are respectively connected to drive motors; the axis of the second rotating pair, the axis of the fourth rotating pair and the outer axis of the universal joint are arranged in parallel; the axis of the first cylindrical pair and the axis of the second cylindrical pair are arranged in parallel, and the axes of both are perpendicular to the axis of the fourth rotating pair; a circular arc track matching the first movable pair is opened on the fixed platform, and the axis of the second cylindrical pair is perpendicular to the plane where the circular arc track is located and passes through the center of the circular arc track; the fourth rotating pair is located at the center of the moving platform, and the universal joint, the fourth rotating pair and the ball pair are arranged in sequence along the length direction of the moving platform and the three are distributed on the same straight line; the second rotating pair and the third rotating pair are connected by a fourth connecting rod, and the free ends of the second rotating pair and the third rotating pair are connected to the first movable pair and the ball pair by the third connecting rod and the fifth connecting rod respectively.

2. A completely decoupled two-rotation-one-movement parallel mechanism according to claim 1, characterized in that: The second cylindrical pair is connected to the fourth rotation pair via a sixth connecting rod.

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