Parallel mechanism with planar closed loop and movement method thereof

Abstract

The invention discloses a parallel mechanism with a planar closed loop and a movement method of the parallel mechanism. The parallel mechanism comprises a static platform, a movable platform and three branch chains connected with the static platform and the movable platform. The three branch chains comprise a plane closed loop connected with the static platform and two connecting rods connected through a U pair, and the tops of the connecting rods are connected with the movable platform; by controlling the movement configuration change of the planar closed loop, the parallel mechanism can realize the output of four movement modes including three rotational degrees of freedom, three movement degrees of freedom, two rotational degrees of freedom and one movement degree of freedom, and two movement degrees of freedom and one rotational degree of freedom, and the mutual free switching among the four modes. According to the parallel mechanism, a planar closed loop is combined with a conventional parallel mechanism, and the parallel mechanism has the advantages of multiple motion modes, convenience in conversion, simplicity and convenience in control operation, small motion inertia and convenience in explosion-proof design, and has wide application prospects in the field of additive manufacturing or subtractive manufacturing and special fields (such as underground coal mines and aerospace equipment) with high explosion-proof requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of robots and relates to a novel parallel mechanism with four motion modes and a motion method with a planar closed-loop circuit. Background Art

[0002] A parallel mechanism can be defined as a closed-loop mechanism in which a moving platform and a static platform are connected by at least two independent kinematic chains, the moving platform has two or more degrees of freedom, and is driven in parallel. It has the advantages of high precision, high rigidity, and high speed, and is widely used in aerospace, industrial production, and medical fields.

[0003] Traditional parallel mechanisms have defects in structural design, such as high complexity, difficulty in control, and lack of flexibility, which to a certain extent limit their wide application. At the same time, due to the limitations of the motion mode, traditional parallel mechanisms often cannot effectively achieve the expected motion effects when facing complex and changeable working environments and tasks, thus affecting the performance and reliability of the overall system.

[0004] At present, a single parallel mechanism that can realize four motion modes including three rotational degrees of freedom, two rotational degrees of freedom and one mobile degree of freedom, two mobile degrees of freedom and one rotational degree of freedom, and three mobile degrees of freedom is rarely used. A new parallel mechanism that can realize conversion of multiple motion modes through fewer branches and driving components has become a technical problem that needs to be urgently solved in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a parallel mechanism with a planar closed loop and a motion method thereof, so as to solve the problem that the existing parallel mechanism has a relatively simple structure and cannot meet the needs of multiple working mode conversion. The parallel mechanism combines the planar closed loop with the traditional parallel mechanism to form a parallel mechanism with four motion modes: three degrees of freedom in movement, three degrees of freedom in rotation, two degrees of freedom in movement and one degree of freedom in rotation, and two degrees of freedom in rotation and one degree of freedom in movement. The parallel mechanism has the advantages of multiple motion modes and convenient conversion, simple control operation, small motion inertia, and convenient explosion-proof design. It has broad application prospects in the fields of additive manufacturing, subtractive manufacturing, and special fields with high explosion-proof requirements (such as underground coal mines and aerospace equipment).

[0006] The present invention is achieved through the following technical solutions.

[0007] One aspect of the present invention provides a parallel mechanism with a planar closed loop, comprising a static platform, a dynamic platform and three branch chains connecting the static platform and the dynamic platform;

[0008] The three branch chains include a planar closed loop connected to the static platform and two connecting rods connected by a U pair, and the top of the connecting rod is connected to the dynamic platform;

[0009] By controlling the changes in the motion configuration of the planar closed-loop circuit, the dynamic platform of the parallel mechanism can achieve the output of four motion modes: three rotational degrees of freedom, three mobile degrees of freedom, two rotational degrees of freedom and one mobile degree of freedom, and two mobile degrees of freedom and one rotational degree of freedom, as well as free switching between these four modes.

[0010] Preferably, the planar closed loop includes a frame fixed on a static platform, with two ends of the frame connecting a third link and a first link as a driving component, the tops of the first link and the third link are hinged to the second link, and the top of the second link is hinged to the branch chain link.

[0011] Preferably, a notch is provided at one end of the frame, and the third connecting rod slides in the notch through a slider at its end; and the other end of the frame is hinged to the first connecting rod.

[0012] Preferably, a tension spring is connected near the hinged ends of the first connecting rod and the second connecting rod.

[0013] Preferably, the second connecting rod is a T-shaped rod, the two ends of the bottom are hinged to the first connecting rod and the third connecting rod respectively, and the top of the T-shaped rod is hinged to the branch link.

[0014] Another aspect of the present invention provides a motion method of the parallel mechanism with a planar closed loop, wherein when the planar closed loop is driven by the first connecting rod to work, the parallel mechanism with a planar closed loop comprises the following two motion configurations:

[0015] When the slider slides in the slot, the tension spring fixes the first connecting rod and the second connecting rod so that no relative rotation occurs. At this time, the planar closed loop is a crank slider mechanism, which is in the first motion configuration;

[0016] If the slider is located at the extreme position where the slot is far away from one end of the first connecting rod, the tension spring bears the axial load, and the first connecting rod and the second connecting rod rotate relative to each other. At this time, the planar closed loop is a hinged four-bar mechanism, which is the second motion configuration.

[0017] Preferably, the three rotational degrees of freedom motion modes of the parallel mechanism are:

[0018] If the planar closed loops of the three branch chains are all in the first configuration, the slider slides in the slot, and the tension spring fixes the first connecting rod and the second connecting rod so that no relative rotation occurs.

[0019] Preferably, the three degrees of freedom motion modes of the parallel mechanism are:

[0020] When the planar closed loops of the three branch chains are all in the second configuration, the tension spring bears the axial load, and the first connecting rods and the second connecting rods of the three branch chains rotate relative to each other.

[0021] Preferably, the motion modes of the parallel mechanism with two rotational degrees of freedom and one translational degree of freedom are:

[0022] Among the three branch chains, the planar closed loop of one branch chain is in the second configuration, the tension spring bears the axial load, and relative rotation occurs between the first connecting rod and the second connecting rod of one branch chain; the planar closed loops of the other two branch chains are in the first configuration, and the tension springs of the two branch chains fix the first connecting rod and the second connecting rod so that relative rotation does not occur.

[0023] Preferably, the motion modes of the parallel mechanism with two degrees of freedom of movement and one degree of freedom of rotation are:

[0024] Among the three branch chains, the planar closed loop of one branch chain is in the first configuration, and the tension spring of one branch chain fixes the first connecting rod and the second connecting rod so that relative rotation does not occur; when the planar closed loops of the other two branch chains are in the second configuration, the tension spring bears axial load, and relative rotation occurs between the first connecting rod and the second connecting rod of the other two branch chains.

[0025] The present invention adopts the above technical solution, which has the following beneficial effects:

[0026] 1. The present invention combines a planar closed-loop circuit with a traditional parallel mechanism to form a new parallel mechanism with four motion modes: three rotational degrees of freedom, three mobile degrees of freedom, two rotational degrees of freedom and one mobile degree of freedom, and two mobile degrees of freedom and one rotational degree of freedom. This solves the problem that the existing parallel mechanism has a relatively single structure and cannot meet the needs of multiple working mode conversions.

[0027] 2 The present invention can achieve smart switching of motion modes by changing the different configurations of the planar closed loop circuit without changing the driving mode, thereby simplifying the control steps and having better operability.

[0028] 3. All driving components of the present invention are located on the static platform, which has the advantages of simple structure, efficient power transmission, easier control, more stable mechanism movement, etc. compared with the driving pair located on the branch chain.

[0029] 4. The driving components and control components of the parallel mechanism are all within the envelope space formed by the moving platform and the static platform, which facilitates the explosion-proof design of the mechanism and enables it to be applied to some special environments with high explosion-proof requirements (such as underground coal mines and aerospace equipment).

[0030] The invention has novel design, strong structural bearing capacity, large working space, flexible control, can be used for work in complex scenes, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 It is a schematic diagram of the structure of a parallel mechanism with a planar closed loop of the present invention;

[0033] Figure 2 It is a schematic diagram of a planar closed loop structure of a parallel mechanism with a planar closed loop of the present invention;

[0034] Figure 3 It is a schematic diagram of the position relationship of two connecting rods connecting a planar closed loop and a moving platform of a parallel mechanism with a planar closed loop of the present invention;

[0035] Figure 4 It is a schematic diagram of the first configuration of a planar closed loop of a parallel mechanism with a planar closed loop of the present invention;

[0036] Figure 5 It is a schematic diagram of the second configuration of a planar closed loop of a parallel mechanism with a planar closed loop of the present invention;

[0037] Figure 6 It is a schematic diagram of the motion mode configuration of three rotational degrees of freedom of a parallel mechanism with a planar closed loop of the present invention;

[0038] Figure 7 It is a schematic diagram of the motion mode configuration of a parallel mechanism with a planar closed loop and two rotational degrees of freedom and one translational degree of freedom of the present invention;

[0039] Figure 8 It is a schematic diagram of the motion mode configuration of a parallel mechanism with a planar closed loop and two degrees of freedom of movement and one degree of freedom of rotation of the present invention;

[0040] Fig. 9 The present invention is a schematic diagram of the motion mode configuration of three mobile degrees of freedom of a parallel mechanism with a planar closed loop.

[0041] Description of reference numerals:

[0042] 1. Static platform; 2. Branch chain; 3. Moving platform; 21. Planar closed loop; 211. First connecting rod; 212. Second connecting rod; 213. Third connecting rod; 214. Frame; 215. Tension spring; 216. Slider; 217. Notch; 22. RU connecting rod; 23. UR connecting rod; 241. First rotating pair; 242. Universal joint; 243. Second rotating pair. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0044] The present invention provides a novel parallel mechanism with a planar closed loop, such as Figure 1 As shown, it includes a static platform 1, a dynamic platform 3 and three branch chains 2 connecting the static platform and the dynamic platform.

[0045] The three branch chains 2 have the same structure. The branch chain 2 includes two connecting rods and a planar closed loop 21 connected by a revolute pair and a universal joint. The planar closed loop 21 is connected to the static platform 1. Among the two connecting rods, one is a UR connecting rod 23 connected to the dynamic platform 3, and the other is a RU connecting rod 22 connected to the planar closed loop 21.

[0046] like Figure 2 As shown, each branch chain mid-plane closed loop 21 includes a frame 214 fixed on the static platform 1, the first link 211 and the third link 213 are connected at both ends of the frame 214, the first link 211 and the third link 213 are hinged at the top of the second link 212, and the second link 212 is hinged at the top of the RU link 22. Among them, the frame 214 is hinged with the first link 211 and is slidably connected with the third link 213; a notch 217 is provided at one end of the frame 214, and a slider 216 is provided at the bottom of the third link 213, and the third link 213 slides in the notch 217 through the slider 216; the revolving pair connecting the first link 211 and the frame 214 is connected to the rotating drive motor to drive the first link 211 to rotate. A tension spring 215 is connected near the hinged end of the first link 211 and the second link 212. The second connecting rod 212 is a T-shaped rod, the two ends of the bottom are hinged to the first connecting rod 211 and the third connecting rod 213 respectively, and the top of the T-shaped rod is hinged to the RU connecting rod 22.

[0047] like Figure 3 As shown, in addition to the planar closed loop 21 and the UR connecting rod 23 and the RU connecting rod 22, the three branch chains also include a first rotating pair 241, a second rotating pair 243 and a universal joint 242; the lower end of the RU connecting rod 22 in each branch chain is connected to the second connecting rod 212 of the planar closed loop 21 through the first rotating pair 241, the upper end of the UR connecting rod 23 is connected to the moving platform 3 through the second rotating pair 243, and the RU connecting rod 22 and the UR connecting rod 23 are connected through the universal joint 242.

[0048] The UR connecting rods 23 of the three branches of the present invention are respectively equidistantly connected to the edges of the moving platform 3, and the frames 214 of the planar closed loop 21 are respectively equidistantly connected to the edges of the static platform 1. When the first connecting rod 211 drives the planar closed loop 21 to work, the planar closed loop includes the following two configurations:

[0049] like Figure 4As shown, when the slider 216 slides in the slot 217, the tension spring 215 fixes the first connecting rod 211 and the second connecting rod 212 so that relative rotation does not occur. At this time, the planar closed loop 21 is a crank slider mechanism in the first configuration.

[0050] like Figure 5 As shown, if the slider 216 is located at the extreme position where the slot 217 is away from one end of the first connecting rod 211, the tension spring 215 bears the axial load, and the first connecting rod 211 and the second connecting rod 212 rotate relative to each other. At this time, the planar closed loop 21 is a hinged four-bar mechanism, which is in the second configuration.

[0051] The parallel mechanism with a planar closed-loop circuit of the present invention has the following four motion modes, including three rotational degrees of freedom, two rotational degrees of freedom and one translational degree of freedom, two translational degrees of freedom and one rotational degree of freedom, and three translational degrees of freedom, all of which are driven by the rotating pairs on each branch chain.

[0052] like Figure 6 As shown, if the planar closed loops 21 of the three branch chains 2 are all in the first configuration, the slider 216 slides in the slot 217, and the tension spring 215 fixes the first link 211 and the second link 212 so that there is no relative rotation. The parallel mechanism has a three-degree-of-freedom motion mode.

[0053] like Figure 7 As shown, if the planar closed-loop circuit 21 of one of the three branch chains 2 is in the second configuration, the tension spring 215 bears the axial load, and relative rotation occurs between the first connecting rod 211 and the second connecting rod 212 of one branch chain; when the planar closed-loop circuit 21 of the other two branch chains is in the first configuration, the tension springs 215 of the two branch chains fix the first connecting rod 211 and the second connecting rod 212 so that relative rotation does not occur, and the parallel mechanism has two rotational degrees of freedom and one translational degree of freedom motion mode.

[0054] like Figure 8 As shown, if the planar closed-loop circuit 21 of one branch chain among the three branches 2 is in the first configuration, the tension spring 215 of one branch chain fixes the first connecting rod 211 and the second connecting rod 212 so that relative rotation does not occur; when the planar closed-loop circuit 21 of the other two branches is in the second configuration, the tension spring 215 bears the axial load, and relative rotation occurs between the first connecting rod 211 and the second connecting rod 212 of the other two branches; the parallel mechanism has a motion mode with two degrees of freedom of movement and one degree of freedom of rotation.

[0055] like Fig. 9 As shown, if the planar closed loops 21 of the three branch chains 2 are all in the second configuration, the tension spring 215 bears the axial load, and relative rotation occurs between the first connecting rod 211 and the second connecting rod 212 of the three branch chains; the parallel mechanism has a three-degree-of-freedom motion mode.

[0056] Therefore, the novel parallel mechanism with a planar closed loop of the present invention can realize four motion modes including three rotational degrees of freedom, two rotational degrees of freedom and one mobile degree of freedom, two mobile degrees of freedom and one rotational degree of freedom, and three mobile degrees of freedom through the driving components at the bottom of each branch chain, which can effectively achieve the expected motion effect, thereby improving the performance and reliability of the overall system, and has the advantages of multiple motion modes and convenient conversion, simple control operation, small motion inertia, and convenient explosion-proof design. The mechanism of the present invention can be applied to work in complex situations, and has broad application prospects in the fields of additive manufacturing, subtractive manufacturing, and special fields with high explosion-proof requirements (such as underground coal mines and aerospace equipment).

[0057] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A parallel mechanism with a planar closed loop, characterized in that: It comprises a static platform (1), a dynamic platform (3) and three branch chains (2) connecting the static platform and the dynamic platform; The three branch chains include a planar closed loop (21) connected to the static platform (1) and two connecting rods connected by a U pair, and the top of the connecting rod is connected to the dynamic platform (3); By controlling the change in the motion configuration of the planar closed loop (21), the moving platform (3) of the parallel mechanism can realize the output of four motion modes: three rotational degrees of freedom, three mobile degrees of freedom, two rotational degrees of freedom and one mobile degree of freedom, and two mobile degrees of freedom and one rotational degree of freedom, as well as free switching between the four modes.

2. The parallel mechanism with a planar closed loop according to claim 1, characterized in that: The planar closed loop (21) comprises a frame (214) fixed on the static platform (1), the two ends of the frame (214) are connected to a third connecting rod (213) and a first connecting rod (211) as a driving component, the tops of the first connecting rod (211) and the third connecting rod (213) are hinged to the second connecting rod (212), and the top of the second connecting rod (212) is hinged to the branch chain connecting rod.

3. The parallel mechanism with a planar closed loop according to claim 2, characterized in that: A notch (217) is provided at one end of the frame (214), and the third connecting rod (213) slides in the notch (217) through a slider (216) at its end; the other end of the frame (214) is hinged to the first connecting rod (211).

4. The parallel mechanism with a planar closed loop according to claim 2, characterized in that: A tension spring (215) is connected near the hinged ends of the first connecting rod (211) and the second connecting rod (212).

5. The parallel mechanism with a planar closed loop according to claim 2, characterized in that: The second connecting rod (212) is a T-shaped rod, the two ends of the bottom are respectively hinged to the first connecting rod (211) and the third connecting rod (213), and the top of the T-shaped rod is hinged to the branch link.

6. The motion method of a parallel mechanism with a planar closed loop according to any one of claims 1 to 5, characterized in that: When the first connecting rod (211) drives the planar closed loop (2) 1 to work, the planar closed loop includes the following two motion configurations: When the slider (216) is located in the slot (217) and slides, the tension spring (215) fixes the first connecting rod (211) and the second connecting rod (212) so that relative rotation does not occur. At this time, the planar closed loop (21) is a crank slider mechanism, which is in a first motion configuration; When the slider (216) is located at the extreme position where the notch (217) is away from one end of the first connecting rod (211), the tension spring (215) bears the axial load, and relative rotation occurs between the first connecting rod (211) and the second connecting rod (212). At this time, the planar closed loop (21) is a hinged four-bar mechanism, which is in the second motion configuration.

7. The motion method of the parallel mechanism with a planar closed loop according to claim 6, characterized in that: The three rotational degrees of freedom motion modes are: If the planar closed loops (21) of the three branch chains (2) are all in the first configuration, the slider (216) slides in the slot (217), and the tension spring (215) fixes the first connecting rod (211) and the second connecting rod (212) so that relative rotation does not occur.

8. The motion method of the parallel mechanism with a planar closed loop according to claim 6, characterized in that: The three degrees of freedom of movement modes are: When the planar closed loops (21) of the three branch chains (2) are all in the second configuration, the tension spring (215) bears the axial load, and relative rotation occurs between the first connecting rods (211) and the second connecting rods (212) of the three branch chains.

9. The motion method of the parallel mechanism with a planar closed loop according to claim 6, characterized in that: The motion mode with two rotational degrees of freedom and one translational degree of freedom is: Among the three branch chains (2), the planar closed loop (21) of one branch chain is in the second configuration, the tension spring (215) bears the axial load, and relative rotation occurs between the first connecting rod (211) and the second connecting rod (212) of one branch chain; and the planar closed loops (21) of the other two branch chains are in the first configuration, and the tension springs (215) of the two branch chains fix the first connecting rod (211) and the second connecting rod (212) so that relative rotation does not occur.

10. The motion method of the parallel mechanism with a planar closed loop according to claim 6, characterized in that: The motion pattern with two translational degrees of freedom and one rotational degree of freedom is: Among the three branch chains (2), the planar closed loop (21) of one branch chain is in a first configuration, and the tension spring (215) of one branch chain fixes the first connecting rod (211) and the second connecting rod (212) so that relative rotation does not occur; When the planar closed loops (21) of the other two branch chains are in the second configuration, the tension spring (215) bears the axial load. The first connecting rod (211) and the second connecting rod (212) of the other two branch chains rotate relative to each other.

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