CN114393566B

CN114393566B - Light-weight high-speed four-degree-of-freedom cable-driven parallel robot

Info

Publication number: CN114393566B
Application number: CN202210068017.5A
Authority: CN
Inventors: 邵珠峰; 段金昊; 张兆坤; 霍晔; 刘汉擎
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-01-20
Filing date: 2022-01-20
Publication date: 2023-09-08
Anticipated expiration: 2042-01-20
Also published as: CN114393566A

Abstract

The invention discloses a lightweight high-speed four-degree-of-freedom cable-driven parallel robot which comprises a static platform, a dynamic platform, a cable-driven branched chain and a central branched chain. The movable platform comprises an outer platform, an inner platform, a transmission mechanism and an actuator; the four groups of cable driving branched chains are respectively positioned at the front side, the rear side, the left side and the right side of the center of the static platform; parallel ropes of the left and right groups of rope driving branched chains are connected to the left side and the right side of the outer platform, and parallel ropes of the front and rear groups of rope driving branched chains are connected to the front side and the rear side of the inner platform; the central branched chain always tightens four groups of parallel ropes; when the four-rope-driven SCARA mechanism works, the roller driving assemblies of the four groups of rope-driven branched chains control respective parallel ropes, so that the movable platform has three-dimensional translational freedom degrees, the inner platform is driven by the parallel ropes of the two groups of rope-driven branched chains which are arranged in a front-back opposite mode, and further the actuator has one-dimensional rotational freedom degrees through the inner platform driving transmission mechanism, and therefore four-degree SCARA movement is achieved. The invention has the advantages of light weight, high movement efficiency and the like.

Description

Light-weight high-speed four-degree-of-freedom cable-driven parallel robot

Technical Field

The invention relates to the technical field of parallel robots, in particular to a lightweight high-speed four-degree-of-freedom cable-driven parallel robot.

Background

In many industries such as food, medicine, new energy, logistics, 3C electronics, etc., a large number of robots are needed to pick, arrange and package products at high speed. The high-speed robot is an important component of an industrial robot, and has become core equipment for improving efficiency, reducing cost and improving quality in the field of sorting and packaging, and has large demand and wide demand range.

The tail end of the high-speed robot is generally provided with different types of grabbing tools or grabbing hands according to different grabbing objects, the robot body is required to have a space positioning function on the tail end, the tail end can realize three-degree-of-freedom space translation and one rotational degree of freedom along an axis of a fixed direction so as to adjust the posture of the grabbing object, and finally 4-degree-of-freedom SCARA motion is realized, namely, translation motion in a three-dimensional space is added with one rotational motion along the axis of the fixed direction.

The existing high-speed robots are rigid mechanisms and can be divided into two major types of serial robots and parallel robots according to different configurations. The serial robot has the characteristics of large working space and good flexibility, but the moving branched chains are stacked layer by layer, and the inertia of moving parts is large, so that the terminal speed and the acceleration of the serial robot are low, and the power consumption is high. Compared with a serial robot, the parallel robot has improved speed and efficiency, but is oriented to the development trend of light, flexible and intelligent equipment and the increasingly complex and changeable production requirements, and the performance of the parallel robot is still provided with a bottleneck to be broken through, which is specifically shown in the following steps: (1) The motion branched chain adopts a rigid rod piece, so that the further reduction of the quality of the motion part and the further improvement of the motion efficiency are limited; (2) A large number of complex hinges such as spherical hinges are used in the motion branched chains, so that the motion range of the movable platform is limited; (3) The driving unit needs to use a precise speed reducer with a large reduction ratio, a spherical hinge and other precise transmission parts, so that the cost is high.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention aims to provide a lightweight high-speed four-degree-of-freedom cable-driven parallel robot which has the advantages of light weight, high motion efficiency, simple structure, large motion range and low cost, and can realize high-speed grabbing and picking.

According to an embodiment of the invention, a lightweight high-speed four-degree-of-freedom cable-driven parallel robot comprises:

a static platform;

the movable platform is positioned below the static platform at intervals and comprises an outer platform, an inner platform, a transmission mechanism and an actuator, wherein the outer platform comprises an outer upper platform and an outer lower platform, the left side and the right side of the outer upper platform are fixedly connected, the inner platform and the transmission mechanism are positioned between the outer upper platform and the outer lower platform, the transmission mechanism is respectively connected with the outer platform and the inner platform, and the actuator is positioned below the movable platform and is connected with the transmission mechanism;

the four groups of cable driving branched chains are respectively positioned at the front side, the rear side, the left side and the right side of the center of the static platform; each group of cable driving branched chains comprises a roller driving assembly, a pulley assembly and parallel ropes, wherein the roller driving assembly and the pulley assembly are arranged on the static platform, the parallel ropes are wound on the roller driving assembly and are guided by the pulley assembly to be connected to the movable platform, the parallel ropes of two groups of cable driving branched chains which are oppositely arranged left and right are correspondingly connected to the left and right opposite sides of the outer platform, and the parallel ropes of two groups of cable driving branched chains which are oppositely arranged front and back are correspondingly connected to the front and back opposite sides of the inner platform;

The two ends of the central branched chain are respectively connected with the center of the static platform and the top center of the movable platform and are used for tensioning four groups of parallel ropes all the time;

when the four-wire-driven chain type SCARA mechanism works, the roller driving assemblies of the four groups of wire-driven branched chains respectively control the retraction and the extension of the respective parallel ropes correspondingly, so that the movable platform has three-dimensional translational freedom degrees, the inner platform is driven by the parallel ropes of the two groups of wire-driven branched chains which are arranged in a front-back opposite mode, and the transmission mechanism is driven by the inner platform, so that the actuator has one-dimensional rotational freedom degrees around the central axis of the actuator, and therefore four-degree-of-freedom SCARA movement is realized.

The lightweight high-speed four-degree-of-freedom cable-driven parallel robot provided by the embodiment of the invention has the advantages that firstly, the inner platform is driven by the parallel ropes, and then the actuator is enabled to have one-dimensional rotation freedom degree around the central axis of the actuator by the inner platform driving transmission mechanism, and an additional driving unit is not required to be arranged on the movable platform to drive the actuator to rotate, so that the overall quality of the movable platform can be effectively reduced, and the parallel robot provided by the invention can realize the tasks of high-speed grabbing, sorting and the like with low cost and high efficiency. Secondly, the four groups of rope driving branched chains replace a rigid rod piece moving branched chain in the prior art to drive the movable platform, on one hand, the mass of the parallel robot can be greatly reduced, and the parallel robot can easily realize high speed and acceleration, so that the moving efficiency of the robot is greatly improved, the load brought by the mass of the robot is smaller, and the energy consumption for driving the robot to move is smaller; on the other hand, each group of cable driving branched chains avoids complex hinges such as spherical hinges and the like which are used in a large number of rigid rod piece moving branched chains in the prior art, and has low cost and simple structure. Thirdly, four groups of parallel ropes are tensioned all the time by arranging a central branched chain, so that the driving redundancy of a movable platform is avoided, the overall rigidity of the parallel robot is improved, the robot has better high-speed/high-acceleration performance, and high dynamic motion can be realized. Fourth, the parallel robot of the invention has the advantages of strong load capacity and high precision of the rigid parallel mechanism and also has the advantages of low inertia and large working space of the cable driving mechanism by adopting the cable driving parallel mechanism.

According to some embodiments of the invention, in each group of the rope driving branched chains, the number of ropes in the parallel ropes is two, the number of the pulley assemblies is two, each pulley assembly of two groups is provided with a rope outlet point for leading out a single rope in the parallel ropes, the movable platform is provided with two rope connecting points respectively and correspondingly connected with the two ropes, and the two rope outlet points and the two rope connecting points are sequentially connected to form a parallelogram all the time.

According to some embodiments of the invention, in each group of the rope driving branched chains, two ropes are always parallel and synchronously wound and unwound under the drive of the roller driving assembly.

According to some embodiments of the invention, a tension sensor is provided at each of the rope connection points, the tension sensor being used for rope force monitoring.

According to some embodiments of the invention, the roller driving assembly includes a roller mount fixedly mounted on an upper surface of the stationary platform, a roller rotatably supported on the roller mount, one end of the parallel rope wound around the roller, and a servo motor driving the roller to rotate in a forward and reverse direction to change a length of the parallel rope between the pulley assembly and the movable platform.

According to some embodiments of the invention, the servo motor is provided with an encoder.

According to some embodiments of the invention, the servo motor has a current sensor therein for rope force monitoring.

According to some embodiments of the invention, the pulley assembly comprises an upper pulley assembly and a lower pulley assembly; the upper pulley assembly is positioned above the static platform and comprises an upper pulley seat and an upper pulley; the upper pulley seat is fixed on the upper surface of the static platform, and the upper pulley is rotatably supported on the upper pulley seat; the lower pulley assembly is positioned below the static platform and comprises a sleeve, a rotating seat, two groove pulleys and two transverse cylinders; the sleeve penetrates through the static platform and is fixed with the static platform, and the top of the rotating seat is rotatably sleeved at the lower end of the sleeve; the axes of the two groove pulleys are positioned on the same horizontal plane, and the two groove pulleys are tangentially arranged side by side and rotatably supported on the rotating seat; the two transverse cylinders are positioned below the two groove pulleys and at the same height, and the axes of the two transverse cylinders are perpendicular to the axes of the two groove pulleys; the two transverse cylinders are adjacently and rotatably supported on the rotating seat side by side, and a slit is formed between the two transverse cylinders; after being led out from the roller driving assembly, a single rope in the parallel ropes passes through the upper pulley and then sequentially downwards passes through the sleeve, the grooves corresponding to the tangent positions of the two groove pulleys and the slits in front of the two transverse cylinders, and is connected with the movable platform.

According to some embodiments of the invention, the pulley assembly further comprises an additional pulley assembly, a pressurized pulley assembly, and a pressure sensor; the additional pulley component is positioned above the static platform and comprises an additional pulley seat and an additional pulley, the additional pulley seat is fixed on the upper surface of the static platform, and the additional pulley is rotatably supported on the additional pulley seat; the compression pulley assembly is positioned below the static platform and comprises a compression pulley seat and a compression pulley, the compression pulley is rotatably supported on the compression pulley seat, and the pressure sensor is fixed between the compression pulley seat and the lower surface of the static platform; after being led out from the roller driving assembly, a single rope in the parallel ropes passes through the additional pulley, then passes downwards through the static platform, passes through the compression pulley, then passes upwards through the static platform, and passes through the upper pulley.

According to some embodiments of the invention, the central branch comprises a tensioning unit, an upper end hinge and a lower end hinge; the upper end of the tensioning unit is connected with the center of the static platform through the upper end hinge, and the lower end of the tensioning unit is connected with the center of the outer upper platform through the lower end hinge.

According to some embodiments of the invention, the tensioning unit is a passive tensioning unit or an active tensioning unit.

According to some embodiments of the invention, the passive tensioning unit comprises a rigid rod and a first spring; the upper end hinge consists of a first universal hinge and a first movable pair, an inner ring, a middle ring and an outer ring are respectively arranged from inside to outside, a first rotary pair is arranged between the inner ring and the middle ring, a second rotary pair is arranged between the middle ring and the outer ring, and the rotation axis of the first rotary pair is mutually perpendicular to the rotation axis of the second rotary pair, so that the first universal hinge is formed, the outer ring is fixed in a central hole of the static platform, and a second bearing is arranged on the inner ring; the upper end of the rigid rod piece passes through the second axial bearing, so that a first moving pair is formed; the lower end hinge is a second universal hinge or a first spherical hinge, and the lower end of the rigid rod piece is connected with the lower end hinge; the first spring is always in a compressed state and sleeved on the rigid rod piece, and two ends of the first spring are respectively connected with the upper end hinge and the lower end hinge.

According to some embodiments of the invention, the passive tensioning unit is a cylinder, the upper end hinge is a third universal hinge or a second spherical hinge, the lower end hinge is a fourth universal hinge or a third spherical hinge, the upper end of the cylinder is connected with the upper end hinge, and the lower end of the cylinder is connected with the lower end hinge.

According to some embodiments of the invention, the active tensioning unit is an electric push rod, the upper end hinge is a fifth universal hinge or a fourth spherical hinge, the lower end hinge is a sixth universal hinge or a fifth spherical hinge, the upper end of the electric push rod is connected with the upper end hinge, and the lower end of the electric push rod is connected with the lower end hinge.

According to some embodiments of the invention, the active tensioning unit is a hydraulic cylinder, the upper end hinge is a seventh universal hinge or a sixth spherical hinge, the lower end hinge is an eighth universal hinge or a seventh spherical hinge, the upper end of the hydraulic cylinder is connected with the upper end hinge, and the lower end of the hydraulic cylinder is connected with the lower end hinge.

According to some embodiments of the invention, the transmission mechanism comprises a screw rod and a screw nut, the upper end and the lower end of the screw rod are respectively rotatably supported at the center of the outer upper platform and the center of the outer lower platform, the screw nut is arranged on the screw rod, the inner platform is provided with a central hole, the inner platform is sleeved and fixed on the periphery of the screw nut through the central hole, and the actuator is coaxially fixed at the lower end of the screw rod.

According to some embodiments of the invention, the transmission mechanism further comprises a polish rod and a second spring, wherein the polish rod passes through the through hole of the inner platform, the upper end and the lower end of the polish rod are respectively fixed on the outer upper platform and the outer lower platform correspondingly, and the second spring is sleeved on the polish rod in a compressed state and is positioned between the outer upper platform and the inner platform.

According to some embodiments of the invention, the transmission further comprises a second linear bearing mounted in the bore, the polished rod passing through the second linear bearing.

According to some embodiments of the invention, the transmission comprises a transverse support shaft, a transverse bevel gear, a rotation shaft, and a horizontal bevel gear; the transverse supporting shaft extends in a left-right direction between the outer upper platform and the outer lower platform, and the left end and the right end of the transverse supporting shaft are respectively fixed with the outer platform; the inner platform is rotatably supported on the transverse support shaft; the transverse bevel gear is arranged on the inner platform; the rotary shafts are vertically arranged and rotatably supported on the center of the outer lower platform and the transverse supporting shaft; the horizontal bevel gear is arranged on the rotating shaft and meshed with the transverse bevel gear; the actuator is coaxially fixed at the lower end of the rotating shaft.

According to some embodiments of the invention, there are two horizontal bevel gears, one of which is located above the lateral support shaft, and the other of which is located below the lateral support shaft; the transverse bevel gears are two half-split bevel gears, one half-split bevel gear is positioned on the left side of the rotating shaft and meshed with one of the two horizontal bevel gears, and the other half-split bevel gear is positioned on the right side of the rotating shaft and meshed with the other of the two horizontal bevel gears.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:

fig. 1 is a schematic structural diagram of a lightweight high-speed four-degree-of-freedom cable-driven parallel robot according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a drum driving assembly according to an embodiment of the present invention.

Fig. 3 is a schematic structural view of a pulley assembly according to an embodiment of the present invention.

Fig. 4 is an exploded view of the lower pulley assembly of fig. 3.

Fig. 5 is a schematic view of another pulley assembly according to an embodiment of the invention.

Fig. 6 is a schematic view of the structure of the movable platform and the central branched chain in an embodiment of the present invention, wherein the central branched chain is schematically shown to include a rigid rod and a first spring.

Fig. 7 is a schematic structural view of a first universal hinge according to an embodiment of the present invention.

Fig. 8 is a schematic structural view of a movable platform and a central branched chain in another embodiment of the present invention, wherein the central branched chain includes a cylinder.

Fig. 9 is a schematic structural view of a movable platform and a central branched chain according to still another embodiment of the present invention, wherein the central branched chain includes an electric push rod.

Fig. 10 is a schematic view of the structure of the movable platform and the central branched chain in a further embodiment of the present invention, wherein the central branched chain is schematically shown to include a hydraulic cylinder.

FIG. 11 is a schematic view of a third universal joint according to an embodiment of the present invention.

Fig. 12 is a schematic structural diagram of a movable platform according to an embodiment of the present invention.

Fig. 13 is a cross-sectional view of fig. 12.

Fig. 14 is a schematic structural view of another movable platform according to an embodiment of the present invention.

Fig. 15 is a cross-sectional view of fig. 14.

Reference numerals:

lightweight high-speed four-degree-of-freedom cable-driven parallel robot 1000

Static platform 1

Movable platform 2

Center hole 221 of outer upper platform 211 of outer platform 21, outer lower platform 212 and inner platform 22 of outer platform 21

Second spring 234 of screw rod 231 screw rod nut 232 polish rod 233 of transmission mechanism 23

The second linear bearing 235 transversely supports the shaft 236 transversely to the bevel gear 237 rotation shaft 238

Horizontal bevel gear 239 actuator 24

Rope-driven branched chain 3

Roller 312 servo motor 313 reducer 314 of roller mounting seat 311 of roller driving assembly 31

Coupler 315 encoder 316 pulley assembly 32 upper pulley assembly 321 upper pulley mount 3211

Upper pulley 3212 upper pulley shaft 3213 lower pulley assembly 322 sleeve 3221 rotates the seat 3222

Grooved pulley 3223, horizontal bearing 3224, horizontal bearing 3225, bearing shaft 3226, and horizontal cylinder shaft 3227

Additional pulley assembly 323 additional pulley mount 3231 additional pulley 3232 additional pulley shaft 3233

Compression pulley assembly 324 compression pulley mount 3241 compression pulley 3242 compression pulley shaft 3243

Pressure sensor 325 parallel ropes 33

Central branched chain 4

First universal hinge 421 of upper end hinge 42 of first spring 412 of rigid rod 411 of tensioning unit 41

The inner ring 4211, the middle ring 4212, the outer ring 4213, the first rotation pair 4214, the second rotation pair 4215

First moving pair 422 second axial bearing 4221 lower end hinge 43 cylinder 413

Third universal hinge 423, third inner ring 4231, third middle ring 4232, third outer ring 4233

Third revolute pair 4234 fourth revolute pair 4235 electric push rod 414 hydraulic cylinder 415

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.

A lightweight high-speed four-degree-of-freedom cable-driven parallel robot 1000 according to an embodiment of the present invention is described below with reference to fig. 1 to 15.

As shown in fig. 1 to 15, a lightweight high-speed four-degree-of-freedom cable-driven parallel robot 1000 according to an embodiment of the present invention includes a stationary platform 1, a movable platform 2, a cable-driven branch 3, and a central branch 4. The movable platform 2 is positioned below the static platform 1 at intervals, the movable platform 2 comprises an outer platform 21, an inner platform 22, a transmission mechanism 23 and an actuator 24, the outer platform 21 comprises an outer upper platform 211 and an outer lower platform 212, the left side and the right side of the outer upper platform 211 and the left side of the outer lower platform 212 are fixedly connected, the inner platform 22 and the transmission mechanism 23 are positioned between the outer upper platform 211 and the outer lower platform 212, the transmission mechanism 23 is respectively connected with the outer platform 21 and the inner platform 22, and the actuator 24 is positioned below the movable platform 2 and is connected with the transmission mechanism 23; four groups of cable driving branched chains 3 are arranged, and the four groups of cable driving branched chains 3 are respectively positioned at the front side, the rear side, the left side and the right side of the center of the static platform 1; each group of cable driving branched chains 3 comprises a roller driving assembly 31, a pulley assembly 32 and parallel ropes 33, wherein the roller driving assembly 31 and the pulley assembly 32 are arranged on the static platform 1, the parallel ropes 33 are wound on the roller driving assembly 31 and are guided by the pulley assembly 32 to be connected to the movable platform 2, the parallel ropes 33 of the two groups of cable driving branched chains 3 which are oppositely arranged left and right are correspondingly connected to the left and right opposite sides of the outer platform 21, and the parallel ropes 33 of the two groups of cable driving branched chains 3 which are oppositely arranged front and back are correspondingly connected to the front and back opposite sides of the inner platform 22; two ends of the central branched chain 4 are respectively connected with the center of the static platform 1 and the top center of the movable platform 2 and are used for tensioning four groups of parallel ropes 33 all the time; when the four-wire drive chain mechanism works, the roller drive assemblies 31 of the four groups of wire drive branched chains 3 respectively control the retraction and the extension of the respective parallel ropes 33 correspondingly, so that the movable platform 2 has three-dimensional translational freedom, the inner platform 22 is driven by the parallel ropes 33 of the two groups of wire drive branched chains 3 which are arranged in a front-back opposite mode, and the actuator 24 has one-dimensional rotational freedom around the central axis of the actuator through the inner platform 22 driving the transmission mechanism 23, and therefore four-degree-of-freedom SCARA motion is realized.

Specifically, the static platform 1 is fixed relative to the movable platform 2 during use, and has fixing and mounting functions, so as to provide mounting connection positions and interfaces for functional components, for example, the drum driving component 31 and the pulley component 32. The movable platform 2 is located below the static platform 1 at intervals, the movable platform 2 comprises an outer platform 21, an inner platform 22, a transmission mechanism 23 and an actuator 24, the outer platform 21 comprises an outer upper platform 211 and an outer lower platform 212, the left side and the right side of the outer upper platform 211 and the left side and the right side of the outer lower platform 212 are fixedly connected, the inner platform 22 and the transmission mechanism 23 are located between the outer upper platform 211 and the outer lower platform 212, the transmission mechanism 23 is connected with the outer platform 21 and the inner platform 22 respectively, and the actuator 24 is located below the movable platform 2 and is connected with the transmission mechanism 23. It can be understood that the inner platform 22 is located between the outer upper platform 211 and the outer lower platform 212 to form a layered movable platform 2, the inner platform 22 can move relative to the outer platform 21 to drive the transmission mechanism 23 to move, and the transmission mechanism 23 converts and outputs corresponding movement of the inner platform 22 into rotation around a vertical axis, so as to drive the actuator 24 connected to the transmission mechanism 23 to rotate one-dimensionally around the central axis of the actuator 24, thereby realizing the adjustment of the pose of an object on the actuator 24, that is, realizing the planar rotation freedom degree through the layered movable platform 2, without installing an additional driving unit on the movable platform 2, effectively reducing the movement quality and realizing low-cost and high-efficiency robot equipment. The actuator 24 may be a gripping tool or gripping hand of different kinds to implement the gripping function of the robot terminal.

The four groups of cable driving branched chains 3 are respectively positioned at the front side, the rear side, the left side and the right side of the center of the static platform 1, and in particular, in fig. 1, the four groups of cable driving branched chains 3 can be uniformly distributed in circumference at the center of the static platform 1. Each set of cable driven branches 3 comprises a roller driving assembly 31, a pulley assembly 32 and a parallel rope 33, wherein the roller driving assembly 31 and the pulley assembly 32 are arranged on the static platform 1, and the parallel rope 33 is wound on the roller driving assembly 31 and is connected to the movable platform 2 after being guided by the pulley assembly 32. Wherein the drum driving assembly 31 is used for providing power to drive the parallel ropes 33 wound on the drum driving assembly 31 to move so as to change the length of the parallel ropes 33 between the pulley assembly 32 and the movable platform 2. By a rational arrangement of four sets of pulley assemblies 32, on the one hand, the pulley assemblies 32 are used for guiding and reversing the parallel ropes 33, i.e. changing the extending direction of the parallel ropes 33, for example as shown in fig. 1, so that the parallel ropes 33 penetrate downwards through the stationary platform 1; on the other hand, when the drum driving assembly 31 adjusts the length of the parallel ropes 33 between the pulley assembly 32 and the movable platform 2, it is ensured that the parallel ropes 33 move very smoothly. Four sets of parallel ropes 33 are used for controlling the brake platform 2, so that the brake platform 2 can realize three-degree-of-freedom spatial translation, and three rotational degrees of freedom of the brake platform 2 are limited, namely, the outer platform 21 can perform three-dimensional translation relative to the static platform 1 and cannot rotate, and the motion of the brake platform 2 can be more stable and efficient. Therefore, the parallel robot drives the movable platform 2 through the four groups of cable driving branched chains 3 instead of the rigid rod 411 moving branched chains in the prior art, on one hand, the mass of the parallel robot can be greatly reduced, so that the parallel robot can easily realize high speed and acceleration, the moving efficiency of the robot is greatly improved, the load brought by the mass of the robot is smaller, and the energy consumption for driving the robot to move is smaller; on the other hand, each group of cable driving branched chains 3 avoids complex hinges such as spherical hinges and the like which are used in a large number of movement branched chains of the rigid rod piece 411 in the prior art, and has simple structure and low cost.

Parallel ropes 33 of two sets of cable driven branches 3 disposed opposite left and right are respectively connected to opposite left and right sides of the outer platform 21, and parallel ropes 33 of two sets of cable driven branches 3 disposed opposite front and rear are respectively connected to opposite front and rear sides of the inner platform 22 (as shown in fig. 1). When the actuator 24 needs to rotate, the inner platform 22 can be driven to move by controlling two groups of parallel ropes 33 which are connected to the inner platform 22 and are oppositely arranged in front and back, and then the inner platform 22 drives the transmission mechanism 23 to move, so that the actuator 24 correspondingly rotates in one dimension around the central axis of the actuator, and the posture of an object grabbed on the actuator 24 is adjusted. That is, the rotation power of the actuator 24 is derived from two groups of cable driving branched chains 3 which are oppositely arranged in front and back, so that an additional driving unit is not required to be installed on the movable platform 2, the moving mass is effectively reduced, and the robot equipment with low cost and high efficiency is realized. The two ends of the central branched chain 4 are respectively connected with the center of the static platform 1 and the top center of the movable platform 2 and are used for tensioning four groups of parallel ropes 33 all the time. Specifically, regardless of whether the movable platform 2 is in a stationary state or a moving state, the central branched chain 4 always applies a pushing force to the stationary platform 1 and the movable platform 2, and the pushing force opposes the pulling force of the parallel ropes 33, so that the parallel ropes 33 are always in tension, redundancy in driving the movable platform 2 is avoided, and the whole robot forms a tensile integral structure. The arrangement of the central branched chain 4 improves the overall rigidity of the parallel robot, so that the parallel robot has better high-speed/high-acceleration performance; on the other hand, the parallel ropes 33 are always in a tensioning state, so that the driving and restraining capabilities of the parallel ropes 33 on the movable platform 2 are ensured, and meanwhile, the fact that the parallel ropes 33 are always in the tensioning state is also an important condition that the parallel ropes 33 always form a parallelogram.

When the four-wire drive mechanism works, the roller drive assemblies 31 of the four groups of wire drive branched chains 3 respectively control the retraction and the extension of the respective parallel ropes 33 correspondingly, so that the length of the parallel ropes between the pulley assemblies 32 and the movable platform 2 can be effectively changed, the movable platform 2 has three-dimensional translational freedom degree, the inner platform 22 is driven by the parallel ropes 33 of the two groups of wire drive branched chains 3 which are arranged in a front-back opposite mode, and the actuator 24 has one-dimensional rotational freedom degree around the central axis of the actuator through the inner platform 22 driving transmission mechanism 23, so that four-degree-of-freedom SCARA motion is realized.

The lightweight high-speed four-degree-of-freedom cable-driven parallel robot 1000 according to the embodiment of the invention has the advantages that firstly, the inner platform 22 is driven by the parallel ropes 33, and then the actuator 24 is driven by the transmission mechanism 23 through the inner platform 22 to have one-dimensional rotation freedom degree around the central axis of the actuator, and an additional driving unit is not required to be arranged on the movable platform 2 to drive the actuator 24 to rotate, so that the overall quality of the movable platform 2 can be effectively reduced, and the parallel robot can realize the tasks of high-speed grabbing, sorting and the like with low cost and high efficiency. Secondly, the four groups of rope driving branched chains 3 replace a rigid rod piece 411 moving branched chain in the prior art to drive the movable platform 2, on one hand, the mass of the parallel robot can be greatly reduced, and the parallel robot can easily realize high speed and acceleration, so that the moving efficiency of the robot is greatly improved, the load brought by the mass of the robot is smaller, and the energy consumption for driving the robot to move is smaller; on the other hand, each group of cable driving branched chains 3 avoids complex hinges such as spherical hinges and the like which are used in a large number of movement branched chains of the rigid rod piece 411 in the prior art, and has low cost and simple structure. Thirdly, four groups of parallel ropes 33 are tensioned all the time by arranging the central branched chain 4, so that the driving redundancy of the movable platform 2 is avoided, the overall rigidity of the parallel robot is improved, the robot has better high-speed/high-acceleration performance, and high dynamic movement can be realized. Fourth, the parallel robot of the invention has the advantages of strong load capacity and high precision of the rigid parallel mechanism and also has the advantages of low inertia and large working space of the cable driving mechanism by adopting the cable driving parallel mechanism.

According to some embodiments of the present invention, in each set of cable-driven branched chains 3, the number of the ropes in the parallel ropes 33 is two, the number of the pulley assemblies 32 is two, each pulley assembly 32 in two sets has one cable outlet point for leading out a single rope in the parallel ropes 33, the movable platform 2 has two cable connection points respectively corresponding to the two ropes, the two cable outlet points and the two cable connection points are sequentially connected to form a parallelogram all the time, and the two cable outlet points and the two cable connection points in each set of cable-driven branched chains 3 are sequentially connected to form a parallelogram all the time. The motion of the movable platform 2 is controlled by four groups of parallel ropes 33 which always form a parallelogram, so that the movable platform 2 can realize three-degree-of-freedom space translation, and three rotational degrees of freedom of the movable platform 2 are limited, and the motion of the movable platform 2 is more stable and efficient. Simultaneously, the inner platform 22 is driven to move by two groups of parallel ropes 33 which are arranged in a front-back opposite mode, and then the inner platform 22 drives the transmission mechanism 23 to move, so that the actuator 24 correspondingly rotates in one dimension around the central axis of the actuator 24, and the posture of an object grabbed on the actuator 24 is adjusted. In addition, the number of the parallel ropes 33 is two, which is advantageous for simplifying the robot structure.

According to some embodiments of the present invention, in each group of cable-driven branches 3, two parallel ropes 33 are always parallel and synchronously retracted under the drive of the drum drive assembly 31. In this way, it is ensured that two ropes in the set of parallel ropes 33 are always parallel to drive the movable platform 2 to implement three degrees of freedom spatial translation, while restricting three degrees of freedom of rotation of the movable platform 2. In a specific example, the number of the rollers 312 in the same roller driving assembly 31 is one, and one end of each of the two ropes in the same parallel rope 33 is wound around the roller 312 of the roller driving assembly 31, so that the simultaneous winding and unwinding of the two ropes in the group of parallel ropes 33 can be simply and conveniently realized.

According to some embodiments of the invention, a tension sensor is provided at each rope connection point, the tension sensor being used for rope force monitoring. In this way, on the one hand, the parallel ropes 33 can be subjected to deformation compensation in the control system of the robot according to the monitoring data of the tension sensor so as to improve the positioning control precision of the movable platform 2; on the other hand, the situation that the cable force of the parallel rope 33 is too large or too small can be known in time according to the monitoring data of the tension sensor so as to be processed, and the control effect of the parallel rope 33 on the movable platform 2 is ensured, for example, when the cable force is too large, the parallel rope 33 may break, when the cable force is too small, the parallel rope 33 may have the problems of virtual traction, loosening and the like, and the control effect of the parallel rope 33 on the movable platform 2 can be influenced.

According to some embodiments of the present invention, the roller driving assembly 31 includes a roller mounting seat 311, a roller 312 and a servo motor 313, the roller mounting seat 311 is fixedly mounted on the upper surface of the stationary platform 1, the roller 312 is rotatably supported on the roller mounting seat 311, one end of the parallel rope 33 is wound on the roller 312, the servo motor 313 drives the roller 312 to rotate in a forward and reverse direction, so as to change the length of the parallel rope 33 between the pulley assembly 32 and the movable platform 2, and further control the movable platform 2 to perform three-degree-of-freedom spatial translation, and limit three rotational degrees of freedom of the movable platform 2, so that the movement of the movable platform 2 is smoother and more efficient.

As shown in fig. 2, in one specific example, the drum drive assembly 31 includes a drum mount 311, a drum 312, a servo motor 313, a decelerator 314, and a coupling 315. The decelerator 314 and the servo motor 313 are coaxially and fixedly arranged and mounted on the roller mounting seat 311, a spiral groove for winding the parallel ropes 33 is engraved on the roller 312, an output shaft of the decelerator 314 is fixedly connected with a central rotating shaft of the roller 312 through a coupler 315 and coaxially arranged, and the roller mounting seat 311 is fixedly mounted on the static platform 1.

According to some embodiments of the invention, the servo motor 313 is equipped with an encoder 316. The encoder 316 is provided to measure the rotation angle of the servo motor 313 in real time and feed back to the control system of the parallel robot of the present invention to perform closed loop control of the length of the parallel ropes 33.

According to some embodiments of the present invention, the servo motor 313 has a current sensor therein for rope force monitoring. In this way, on the one hand, the parallel ropes 33 can be subjected to deformation compensation in the control system of the robot according to the monitoring data of the current sensor so as to improve the positioning control precision of the movable platform 2; on the other hand, the situation that the cable force of the parallel rope 33 is too large or too small can be timely obtained according to the monitoring data of the current sensor so as to be processed, and the control effect of the parallel rope 33 on the movable platform 2 is ensured, for example, when the cable force is too large, the parallel rope 33 may break, when the cable force is too small, the parallel rope 33 may have the problems of virtual traction, slackening and the like, and the control effect of the parallel rope 33 on the movable platform 2 can be influenced.

According to some embodiments of the present invention, as shown in fig. 3 and 4, the pulley assembly 32 includes an upper pulley assembly 321 and a lower pulley assembly 322; the upper pulley assembly 321 is positioned above the static platform 1 and comprises an upper pulley seat 3211 and an upper pulley 3212; an upper pulley block 3211 is fixed on the upper surface of the stationary platform 1, and an upper pulley 3212 is rotatably supported on the upper pulley block 3211; the upper pulley assembly 321 serves to guide and divert the parallel ropes 33 and may make the parallel ropes 33 smoother when moving relative to the upper pulley assembly 321. The lower pulley assembly 322 is positioned below the stationary platform 1 and comprises a sleeve 3221, a rotating base 3222, two grooved pulleys 3223 and two transverse cylinders 3224; the sleeve 3221 passes through the static platform 1 and is fixed with the static platform 1, and the top of the rotating seat 3222 is rotatably sleeved at the lower end of the sleeve 3221; that is, the rotating base 3222 can rotate around the central axis of the sleeve 3221 along with the movement of the parallel ropes 33, so that a single rope can be ensured to be always positioned in the central plane where the two groove pulleys 3223 are positioned during the movement of the parallel ropes 33, and on one hand, the rope can be prevented from being separated from the groove pulleys 3223; on the other hand, the abrasion between the rope and the grooved pulley 3223 is reduced, the service life of the rope is prolonged, and the influence on the rotation process of the rope is reduced. The axes of the two grooved pulleys 3223 are positioned on the same horizontal plane, and the two grooved pulleys 3223 are supported on the rotating base 3222 in a side-by-side tangential manner and rotatable manner; the two transverse cylinders 3224 are located below the two groove pulleys 3223 and at the same height, and the axes of the two transverse cylinders 3224 are perpendicular to the axes of the two groove pulleys 3223; two lateral cylinders 3224 are supported on the rotating base 3222 adjacently side by side and rotatably, and a slit is formed between the two lateral cylinders 3224; the provision of a slit between the two cross cylinders 3224 serves to protect the rope from severe wear between the rope and the rotating mount 3222 and may further limit the rope to the center plane in which the two grooved pulleys 3223 are located, preventing the rope from disengaging from the grooved pulleys 3223. After being led out from the roller driving assembly 31, a single rope in the parallel ropes 33 passes through the upper pulley 3212 and then sequentially passes through the sleeve 3221, the corresponding grooves of the two groove pulleys 3223 at the tangent position and the slits in front of the two transverse cylinders 3224 downwards to be connected with the movable platform 2. The arrangement of the corresponding grooves of the two groove pulleys 3223 of the lower pulley assembly 322 at the tangents serves to guide the rope and prevent the rope from falling off the lower pulley assembly 322.

In a specific example, as shown in fig. 4, the upper pulley assembly 321 includes an upper pulley seat 3211, an upper pulley 3212 and an upper pulley shaft 3213, the upper pulley 3212 is rotatably mounted on the upper pulley seat 3211 by the upper pulley shaft 3213, and the upper pulley assembly 321 and the drum driving assembly 31 are both fixed on the upper surface of the stationary platform 1. It will be appreciated that the upper sheave assembly 321 serves to guide and divert the rope and may provide smoother movement of the rope relative to the upper sheave assembly 321. The lower pulley assembly 322 includes a sleeve 3221, a rotating mount 3222, two grooved pulleys 3223, two transverse cylinders 3224, a horizontal bearing 3225, two bearing shafts 3226, and two transverse cylinder shafts 3227. The rotating base 3222 includes an upper rotating base and two lower rotating bases, the two lower rotating bases are symmetrically and fixedly arranged on the lower surface of the upper rotating base, an installation position is provided for the groove pulley 3223 and the transverse cylinder 3224, the sleeve 3221 is of a hollow structure for a rope to pass through, the sleeve 3221 passes through the static platform 1 and is fixed with the static platform 1, and the upper rotating base is rotatably arranged at the lower end of the sleeve 3221 through the horizontal bearing 3225, so that the whole rotating base 3222 can rotate around the central axis of the sleeve 3221 relative to the static platform 1 along with the movement of the rope, and the rope is ensured to be always positioned in the central planes of the two groove pulleys 3223; the two groove pulleys 3223 are positioned between the two lower rotating seats, the axes of the two groove pulleys 3223 are positioned on the same horizontal plane, the two groove pulleys 3223 are supported on the two lower rotating seats in a side-by-side tangential manner and respectively and rotatably through two bearing shafts 3226, grooves are correspondingly formed at the tangential positions of the two groove pulleys 3223, the diameter of each groove is slightly larger than that of a rope, and the groove pulleys 3223 are used for guiding the rope and can prevent the rope from falling off the groove pulleys 3223; the two transverse cylinders 3224 are located below the two groove pulleys 3223 and are located at the same height, the axes of the two transverse cylinders 3224 are perpendicular to the axes of the two groove pulleys 3223, the two transverse cylinders 3224 are respectively rotatably sleeved on the two transverse cylinder shafts 3227, the two transverse cylinder shafts 3227 are respectively installed on the two lower rotating seats, the two transverse cylinder shafts 3227 are supported on the rotating seats 3222 in a side-by-side adjacent mode, a slit is formed between the two transverse cylinders 3224, the slit in front of the two transverse cylinders 3224 of the lower pulley assembly 322 is used for protecting ropes, serious abrasion between the ropes and the rotating seats 3222 is avoided, and the ropes can be further limited in the central plane where the two groove pulleys 3223 are located, so that the ropes are prevented from being separated from the groove pulleys 3223.

According to some embodiments of the present invention, as shown in fig. 5, the pulley assembly 32 further includes an additional pulley assembly 323, a compression pulley assembly 324, and a pressure sensor 325; the additional pulley assembly 323 is located above the static platform 1 and comprises an additional pulley seat 3231 and an additional pulley 3232, the additional pulley seat 3231 is fixed on the upper surface of the static platform 1, the additional pulley 3232 is rotatably supported on the additional pulley seat 3231, for example, the additional pulley 3232 can be sleeved on the additional pulley shaft 3233, and further rotatably mounted on the additional pulley seat 3231 through the additional pulley shaft 3233; the compression pulley assembly 324 is located below the static platform 1 and includes a compression pulley seat 3241 and a compression pulley 3242, the compression pulley 3242 is rotatably supported on the compression pulley seat 3241, for example, the compression pulley 3242 may be sleeved on a compression pulley shaft 3243, and further rotatably mounted on the compression pulley seat 3241 through the compression pulley shaft 3243; a pressure sensor 325 is fixed between the pressure pulley seat 3241 and the lower surface of the static platform 1, and the pressure sensor 325 is used for monitoring the pressure applied by the pressure pulley assembly 324; after being led out of the drum drive assembly 31, the individual ropes of the parallel ropes 33 pass over an additional pulley 3232, down through the stationary platform 1, over a compression pulley 3242, and up through the stationary platform 1, over an upper pulley 3212. It will be appreciated that the additional pulley 3232 and the compression pulley 3242 may each act to direct the rope through the additional pulley 3232 and compression pulley 3242, as shown in fig. 5, and then through the stationary platform 1 downwardly and upwardly. The pressure sensor 325 is provided for monitoring the pressure applied by the rope to the pressure-receiving pulley 3242, wherein when the ropes on both sides of the pressure-receiving pulley 3242 are vertically disposed up and down, the pressure monitored by the pressure sensor 325 is twice the rope force on the ropes, so that the pressure sensor 325 can transmit the monitored pressure back to the control system of the parallel robot of the present invention to calculate the rope force on the ropes. In this way, on the one hand, the parallel ropes 33 can be subjected to deformation compensation in the control system of the robot according to the monitoring data of the pressure sensor 325 so as to improve the positioning control precision of the movable platform 2; on the other hand, the situation that the cable force of the parallel rope 33 is too large or too small can be known in time according to the monitoring data of the pressure sensor 325 so as to process, and the control effect of the parallel rope 33 on the movable platform 2 is ensured, for example, when the cable force is too large, the parallel rope 33 may break, when the cable force is too small, the parallel rope 33 may have the problems of virtual traction, loosening and the like, and the control effect of the parallel rope 33 on the movable platform 2 is affected.

According to some embodiments of the invention, the central branch 4 comprises a tensioning unit 41, an upper end hinge 42 and a lower end hinge 43; the upper end of the tension unit 41 is connected to the center of the stationary platform 1 by an upper end hinge 42, and the lower end of the tension unit 41 is connected to the center of the outer upper platform 211 by a lower end hinge 43. The upper end hinge 42 and the lower end hinge 43 are provided to allow the two ends of the tension unit 41 to have a corresponding degree of freedom of movement so that the tension unit 41 can swing correspondingly with the movement of the movable platform 2. The two ends of the tensioning unit 41 are respectively connected with the center of the static platform 1 and the center of the outer upper platform 211 through the upper end hinge 42 and the lower end hinge 43, no matter the outer platform 21 is in a static state or a moving state, the tensioning unit 41 always applies a pushing force to the outer platform 21, the pushing force is opposite to the pulling force of the parallel ropes 33, so that the parallel ropes 33 are always tensioned, the whole robot forms a tensioning integral structure, the integral rigidity of the parallel robot is improved, meanwhile, the parallel ropes 33 are always tensioned, the driving and restraining capacity of the parallel ropes 33 and the important condition that the parallel ropes 33 always form a parallelogram are ensured, the high-speed/high-acceleration performance of the robot can be effectively improved, and the moving platform 2 can realize high-speed stable movement.

According to some embodiments of the invention, the tensioning unit 41 is a passive tensioning unit or an active tensioning unit. The passive tensioning unit is to tension the rope in a passive manner, for example by applying an auxiliary tensioning force to the movable platform 2 by a spring or by applying an auxiliary tensioning force to the movable platform 2 by a cylinder 413; the active tensioning unit is used for tensioning the rope in an active manner, for example, a hydraulic cylinder 415 or an electric push rod 414 is used for applying a proper auxiliary tensioning force to the movable platform 2 by actively adjusting the thrust or the length output by the hydraulic cylinder 415 or the electric push rod 414. The parallel ropes 33 are tensioned by the tensioning units 41, so that the redundancy of driving the movable platform 2 is avoided, the control is easy, the movement space of the movable platform 2 is larger, and the cost is low.

According to some embodiments of the present invention, as shown in fig. 6 and 7, the passive tensioning unit includes a rigid rod 411 and a first spring 412; the upper end hinge 42 consists of a first universal hinge 421 and a first movable pair 422, wherein the first universal hinge 421, the first movable pair 4214, the second movable pair 4215 and the second movable pair 4215 are respectively arranged between the inner ring 4211 and the middle ring 4212, the first movable pair 4214 and the second movable pair 4213 from inside to outside, the rotation axis of the first movable pair 4214 is perpendicular to the rotation axis of the second movable pair 4215, so that the first universal hinge 421 is formed, the outer ring 4213 is fixed in the central hole 221 of the static platform 1, and the second axial bearing 4221 is arranged on the inner ring 4211; it will be appreciated that the inner ring 4211 may rotate about the central axis of the first pair of rotation 4214 and the middle ring 4212 may rotate about the central axis of the second pair of rotation 4215 to provide the first universal joint 421 with two degrees of rotational freedom. The upper end of the rigid rod 411 passes through the second bearing 4221, thereby constituting a first moving pair 422; it will be appreciated that the rigid rod 411 may move up and down along the second bearing 4221 to increase or decrease the length of the rigid rod 411 between the movable platform 2 and the stationary platform 1 following the movement of the movable platform 2. The lower end hinge 43 is a second universal hinge or a first spherical hinge, and the lower end of the rigid rod piece 411 is connected with the lower end hinge 43; it will be appreciated that the lower hinge 43 has two degrees of rotational freedom so that the passive tensioning unit can follow the motion of the movable platform 2 with a corresponding swing. The first spring 412 is always in a compressed state and sleeved on the rigid rod 411, and two ends of the first spring 412 are respectively connected with the upper end hinge 42 and the lower end hinge 43, so that due to the characteristics of the spring, the spring in the compressed state can generate elastic force opposite to the compression direction to act on the upper end hinge 42 and the lower end hinge 43, and further act on the static platform 1 and the movable platform 2, so that the tension of the rope is opposed to the tension of the rope, and the tensioning of the rope is realized. It should be noted that, the passive tensioning unit of this embodiment may select springs with different stiffness and length parameters according to the load, acceleration and stiffness requirements of the parallel robot of the present invention, so as to provide an adaptive tensioning force for the rope when in use, and reduce the load and energy consumption caused by the introduction of the spring force while effectively tensioning the parallel rope 33.

According to some embodiments of the present invention, as shown in fig. 8, the passive tensioning unit is a cylinder 413, the upper end hinge 42 is a third universal hinge 423 or a second spherical hinge, the lower end hinge 43 is a fourth universal hinge or a third spherical hinge, the upper end of the cylinder 413 is connected to the upper end hinge 42, and the lower end of the cylinder 413 is connected to the lower end hinge 43. Here, the third universal hinge 423 or the second spherical hinge is used to make the upper end of the air cylinder 413 have two rotational degrees of freedom, so that the upper end of the air cylinder 413 may swing around the center of the upper end hinge 42 along with the movement of the movable platform 2, and the fourth universal hinge or the third spherical hinge is used to make the lower end of the air cylinder 413 have two rotational degrees of freedom, that is, the lower end of the air cylinder 413 may swing along with the movement of the movable platform 2. It should be noted that, the passive tensioning unit in this embodiment may replace the cylinders 413 of different types according to the load, acceleration and rigidity requirements of the parallel robot according to the present invention, and the cylinders 413 may dynamically adjust the air supply pressure, so as to provide an adaptive tensioning force for the parallel ropes 33, and reduce the load and energy consumption caused by the introduction of the thrust of the cylinders 413 while effectively tensioning the parallel ropes 33.

In a specific example, as shown in fig. 11, the third universal joint 423 includes a third inner ring 4231, a third middle ring 4232, and a third outer ring 4233 from inside to outside, a third rotation pair 4234 is provided between the third inner ring 4231 and the third middle ring 4232, a fourth rotation pair 4235 is provided between the third middle ring 4232 and the third outer ring 4233, and a rotation axis of the third rotation pair 4234 is perpendicular to a rotation axis of the fourth rotation pair 4235, so as to form the third universal joint 423.

According to some embodiments of the present invention, as shown in fig. 9, the active tensioning unit is an electric putter 414, the upper end hinge 42 is a fifth universal hinge or a fourth spherical hinge, the lower end hinge 43 is a sixth universal hinge or a fifth spherical hinge, the upper end of the electric putter 414 is connected to the upper end hinge 42, and the lower end of the electric putter 414 is connected to the lower end hinge 43. Specifically, the electric push rod 414 adopts a position closed-loop control, a force closed-loop control or a force position hybrid control mode to actively adjust the length or the thrust output by the electric push rod 414, so as to provide an adaptive tensioning force for the parallel ropes 33, effectively ensure the tensioning of the ropes, reduce the load and the energy consumption caused by the thrust of the electric push rod 414, and provide a pulling force for the electric push rod 414 when the load on the movable platform 2 is overlarge, thereby improving the load capacity of the parallel robot. The active tensioning unit of the embodiment can replace the electric push rod 414 with different types according to the load, acceleration and rigidity requirements of the parallel robot so as to adapt to different use requirements.

Further, the shape and the structure of the fifth universal hinge are the same as those of the third universal hinge 423, and the fifth universal hinge also comprises a third inner ring 4231, a third middle ring 4232 and a third outer ring 4233 from inside to outside, a third revolute pair 4234 is arranged between the third inner ring 4231 and the third middle ring 4232, a fourth revolute pair 4235 is arranged between the third middle ring 4232 and the third outer ring 4233, and the rotation axis of the third revolute pair 4234 is mutually perpendicular to the rotation axis of the fourth revolute pair 4235.

According to some embodiments of the present invention, as shown in fig. 10, the active tensioning unit is a hydraulic cylinder 415, the upper end hinge 42 is a seventh universal hinge or a sixth spherical hinge, the lower end hinge 43 is an eighth universal hinge or a seventh spherical hinge, the upper end of the hydraulic cylinder 415 is connected to the upper end hinge 42, and the lower end of the hydraulic cylinder 415 is connected to the lower end hinge 43. Specifically, the hydraulic cylinder 415 adopts a position closed-loop control, a force closed-loop control or a force position hybrid control mode, and the length or the thrust output by the hydraulic cylinder 415 is actively adjusted, so that the adaptive tensioning force is provided for the parallel ropes 33, the tensioning of the ropes is effectively ensured, the load and the energy consumption caused by the thrust of the hydraulic cylinder 415 are reduced, and when the load on the movable platform 2 is overlarge, the hydraulic cylinder 415 can also provide the pulling force, so that the load capacity of the parallel robot is improved. The active tensioning unit of the embodiment can replace hydraulic cylinders 415 with different types according to the load, acceleration and rigidity requirements of the parallel robot so as to adapt to different use requirements.

Further, the seventh universal joint has the same shape and structure as the third universal joint 423, and also includes a third inner ring 4231, a third middle ring 4232, and a third outer ring 4233 from inside to outside, a third rotation pair 4234 is provided between the third inner ring 4231 and the third middle ring 4232, a fourth rotation pair 4235 is provided between the third middle ring 4232 and the third outer ring 4233, and a rotation axis of the third rotation pair 4234 is perpendicular to a rotation axis of the fourth rotation pair 4235.

According to some embodiments of the present invention, as shown in fig. 12 and 13, the transmission mechanism 23 includes a screw rod 231 and a screw rod nut 232, upper and lower ends of the screw rod 231 are rotatably supported at the center of the outer upper platform 211 and the center of the outer lower platform 212, respectively, for example, upper and lower ends of the screw rod 231 may be rotatably supported at the center of the outer upper platform 211 and the center of the outer lower platform 212, respectively, through bearings, the screw rod nut 232 is disposed on the screw rod 231, the screw rod 231 is screw-coupled with the screw rod nut 232, the inner platform 22 has a central hole 221, the inner platform 22 is fastened to the outer circumference of the screw rod nut 232 through the central hole 221, and the actuator 24 is coaxially fixed to the lower end of the screw rod 231. When the actuator 24 is required to rotate around the central axis of the actuator, two groups of parallel ropes 33 connected to the inner platform 22 are synchronously wound and unwound at a specific speed, when the length of the parallel ropes 33 between the movable platform 2 and the pulley assembly 32 is reduced, the inner platform 22 moves upwards relative to the outer platform 21, so that the screw rod 231 is driven to rotate along one direction, the screw rod 231 can drive the actuator 24 to rotate along one direction, and when the length of the parallel ropes 33 between the movable platform 2 and the pulley assembly 32 is increased, the inner platform 22 can push the inner platform 22 downwards relative to the outer platform 21 through the self gravity or the thrust generated by other arranged components to the inner platform 22, so that the inner platform 22 can drive the screw rod 231 to rotate along the other direction, and the screw rod 231 can also drive the actuator 24 to rotate along the opposite direction, so that the one-dimensional rotation freedom degree of the actuator 24 around the central axis of the actuator is realized.

As shown in fig. 12 and 13, in some embodiments of the present invention, the transmission mechanism 23 further includes a polish rod 233 and a second spring 234, the polish rod 233 passes through the through hole of the inner platform 22, the upper end and the lower end of the polish rod 233 are respectively fixed on the outer upper platform 211 and the outer lower platform 212, and the second spring 234 is sleeved on the polish rod 233 in a compressed state and is located between the outer upper platform 211 and the inner platform 22. Here, the polish rod 233 is provided to guide the movement of the inner stage 22 so that the inner stage 22 can move in the axial direction of the polish rod 233, with the movement being smoother. On the one hand, when the inner platform 22 moves downwards, the second spring 234 can provide pushing force for the inner platform 22 to move downwards, and compared with a mode of driving the inner platform 22 to move downwards by self gravity, the mode of pushing the inner platform 22 to move downwards by the second spring 234 is more efficient and controllable; on the other hand, the ropes connected to the inner platform 22 and the outer platform 21 are ensured to be tensioned, and uncontrolled movement of the inner platform 22 along the direction of the polish rod 233 is avoided. It should be noted that, when the passive tensioning unit includes the rigid rod 411 and the first spring 412, the total stiffness of the second spring 234 is smaller than the total stiffness of the first spring 412, because if the total stiffness of the second spring 234 is greater than the total stiffness of the first spring 412, when the parallel rope 33 drives the moving platform 2 to move upwards, the first spring 412 is first extruded to deform, so that the overall position of the moving platform 2 is changed, and therefore, the normal use of the parallel robot of the present invention can be satisfied only when the total stiffness of the second spring 234 is smaller than the total stiffness of the first spring 412.

Specifically, the polished rods 233 are symmetrically provided in plural, for example, two, four, etc., at a pitch, and when four polished rods 233 are provided, as shown in fig. 12, the inner platform 22 is good in motion smoothness.

According to some embodiments of the present invention, as shown in fig. 12 and 13, the transmission mechanism 23 further includes a second linear bearing 235, the second linear bearing 235 being installed in the perforation, and the polish rod 233 passing through the second linear bearing 235. The second linear bearing 235 can make the movement of the inner platform 22 relative to the polish rod 233 smoother, and reduce friction between the polish rod 233 and the inner platform 22.

According to some embodiments of the present invention, as shown in fig. 14 and 15, the transmission mechanism 23 includes a lateral support shaft 236, a lateral bevel gear 237, a rotation shaft 238, and a horizontal bevel gear 239; the transverse support shaft 236 extends in the left-right direction between the outer upper platform 211 and the outer lower platform 212, and the left end and the right end of the transverse support shaft 236 are respectively fixed with the outer platform 21; the inner platform 22 is rotatably supported on a lateral support shaft 236; a transverse bevel gear 237 is provided on the inner platform 22; the rotating shaft 238 is vertically arranged, and the rotating shaft 238 is rotatably supported on the center of the outer lower platform 212 and the lateral support shaft 236; a horizontal bevel gear 239 is provided on the rotation shaft 238, the horizontal bevel gear 239 being meshed with the transverse bevel gear 237; the actuator 24 is coaxially fixed to the lower end of the rotation shaft 238. When the actuator 24 is required to rotate around the central axis of the actuator, one group of parallel ropes 33 in two groups of parallel ropes 33 connected to the inner platform 22 is controlled to be retracted, and the other group of parallel ropes 33 in the two groups of parallel ropes 33 is controlled to be released, so that the inner platform 22 rotates around the transverse support shaft 236 relative to the outer platform 21, the transverse bevel gear 237 mounted on the inner platform 22 rotates along with the inner platform, the horizontal bevel gear 239 meshed with the inner platform is driven to rotate around the axis of the rotating shaft 238, and the horizontal bevel gear 239 rotates to drive the rotating shaft 238 to rotate, so that the actuator 24 connected to the lower end rotates around the vertical axis, and the one-dimensional rotation freedom degree of the actuator 24 around the central axis of the inner platform is realized.

Further, as shown in fig. 14 and 15, there are two horizontal bevel gears 239, one of which 239 is located above the lateral support shaft 236, and the other horizontal bevel gear 239 is located below the lateral support shaft 236; the transverse bevel gears 237 are two and each a half bevel gear, one of which is located on the left side of the rotation shaft 238 and meshes with one of the two horizontal bevel gears 239, and the other of which is located on the right side of the rotation shaft 238 and meshes with the other of the two horizontal bevel gears 239. It can be appreciated that by arranging two sets of horizontal bevel gears 239 and transverse bevel gears 237 which are meshed with each other, the force is dispersed, the whole force is symmetrical, and the force transmission is stable.

In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A lightweight high-speed four-degree-of-freedom cable-driven parallel robot, comprising:

a static platform;

when the four-wire-driven type linear actuator works, the roller driving assemblies of the four groups of wire-driven branched chains respectively control the retraction and the extension of the respective parallel ropes correspondingly, so that the movable platform has three-dimensional translational freedom degrees, the inner platform is driven by the parallel ropes of the two groups of wire-driven branched chains which are oppositely arranged front and back, and the transmission mechanism is driven by the inner platform, so that the actuator has one-dimensional rotational freedom degrees around the central axis of the actuator, and four-degree-of-freedom movement is realized; the transmission mechanism comprises a screw rod and a screw rod nut, the upper end and the lower end of the screw rod are respectively rotatably supported at the center of the outer upper platform and the center of the outer lower platform, the screw rod nut is arranged on the screw rod, the inner platform is provided with a central hole, the inner platform is sleeved and fixed on the periphery of the screw rod nut through the central hole, and the actuator is coaxially fixed at the lower end of the screw rod; or the transmission mechanism comprises a transverse supporting shaft, a transverse bevel gear, a rotating shaft and a horizontal bevel gear; the transverse supporting shaft extends in a left-right direction between the outer upper platform and the outer lower platform, and the left end and the right end of the transverse supporting shaft are respectively fixed with the outer platform; the inner platform is rotatably supported on the transverse support shaft; the transverse bevel gear is arranged on the inner platform; the rotary shafts are vertically arranged and rotatably supported on the center of the outer lower platform and the transverse supporting shaft; the horizontal bevel gear is arranged on the rotating shaft and meshed with the transverse bevel gear; the actuator is coaxially fixed at the lower end of the rotating shaft.

2. The lightweight high-speed four-degree-of-freedom rope-driven parallel robot according to claim 1, wherein in each group of rope-driven branched chains, the number of ropes in the parallel ropes is two, the number of pulley assemblies is two, each pulley assembly in two groups is provided with a rope outlet point for leading out a single rope in the parallel ropes, the movable platform is provided with two rope connecting points respectively and correspondingly connected with the two ropes, and the two rope outlet points and the two rope connecting points are sequentially connected to form a parallelogram all the time.

3. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 1 or 2, wherein in each group of the cable-driven branched chains, two ropes are always parallel and synchronously wound and unwound under the drive of the roller driving assembly.

4. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 2 wherein a tension sensor is provided at each of the cable connection points for cable force monitoring.

5. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 1, wherein the drum driving assembly includes a drum mount fixedly mounted on an upper surface of the stationary platform, a drum rotatably supported on the drum mount, one end of the parallel rope wound on the drum, and a servo motor driving the drum to rotate in a forward and reverse direction to change a length of the parallel rope between the pulley assembly to the movable platform.

6. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 5 wherein the servo motor is equipped with an encoder.

7. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 5 wherein the servo motor has a current sensor therein for rope force monitoring.

8. The lightweight high speed four degree of freedom cable driven parallel robot of claim 1 wherein the pulley assembly includes an upper pulley assembly and a lower pulley assembly;

the upper pulley assembly is positioned above the static platform and comprises an upper pulley seat and an upper pulley; the upper pulley seat is fixed on the upper surface of the static platform, and the upper pulley is rotatably supported on the upper pulley seat;

the lower pulley assembly is positioned below the static platform and comprises a sleeve, a rotating seat, two groove pulleys and two transverse cylinders; the sleeve penetrates through the static platform and is fixed with the static platform, and the top of the rotating seat is rotatably sleeved at the lower end of the sleeve; the axes of the two groove pulleys are positioned on the same horizontal plane, and the two groove pulleys are tangentially arranged side by side and rotatably supported on the rotating seat; the two transverse cylinders are positioned below the two groove pulleys and at the same height, and the axes of the two transverse cylinders are perpendicular to the axes of the two groove pulleys; the two transverse cylinders are adjacently and rotatably supported on the rotating seat side by side, and a slit is formed between the two transverse cylinders; after being led out from the roller driving assembly, a single rope in the parallel ropes passes through the upper pulley and then sequentially downwards passes through the sleeve, the grooves corresponding to the tangent positions of the two groove pulleys and the slits in front of the two transverse cylinders, and is connected with the movable platform.

9. The lightweight high speed four degree of freedom cable driven parallel robot of claim 8 wherein the pulley assembly further comprises an additional pulley assembly, a compression pulley assembly and a pressure sensor; the additional pulley component is positioned above the static platform and comprises an additional pulley seat and an additional pulley, the additional pulley seat is fixed on the upper surface of the static platform, and the additional pulley is rotatably supported on the additional pulley seat; the compression pulley assembly is positioned below the static platform and comprises a compression pulley seat and a compression pulley, the compression pulley is rotatably supported on the compression pulley seat, and the pressure sensor is fixed between the compression pulley seat and the lower surface of the static platform; after being led out from the roller driving assembly, a single rope in the parallel ropes passes through the additional pulley, then passes downwards through the static platform, passes through the compression pulley, then passes upwards through the static platform, and passes through the upper pulley.

10. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 1, wherein the central branched chain includes a tensioning unit, an upper end hinge, and a lower end hinge; the upper end of the tensioning unit is connected with the center of the static platform through the upper end hinge, and the lower end of the tensioning unit is connected with the center of the outer upper platform through the lower end hinge.

11. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 10, wherein the tensioning unit is a passive tensioning unit or an active tensioning unit.

12. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 11, wherein the passive tensioning unit includes a rigid rod and a first spring; the upper end hinge consists of a first universal hinge and a first movable pair, an inner ring, a middle ring and an outer ring are respectively arranged from inside to outside, a first rotary pair is arranged between the inner ring and the middle ring, a second rotary pair is arranged between the middle ring and the outer ring, and the rotation axis of the first rotary pair is mutually perpendicular to the rotation axis of the second rotary pair, so that the first universal hinge is formed, the outer ring is fixed in a central hole of the static platform, and a second bearing is arranged on the inner ring; the upper end of the rigid rod piece passes through the second axial bearing, so that a first moving pair is formed; the lower end hinge is a second universal hinge or a first spherical hinge, and the lower end of the rigid rod piece is connected with the lower end hinge; the first spring is always in a compressed state and sleeved on the rigid rod piece, and two ends of the first spring are respectively connected with the upper end hinge and the lower end hinge.

13. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot according to claim 11, wherein the passive tensioning unit is a cylinder, the upper end hinge is a third universal hinge or a second spherical hinge, the lower end hinge is a fourth universal hinge or a third spherical hinge, the upper end of the cylinder is connected with the upper end hinge, and the lower end of the cylinder is connected with the lower end hinge.

14. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 11,

the active tensioning unit is an electric push rod, the upper end hinge is a fifth universal hinge or a fourth spherical hinge, the lower end hinge is a sixth universal hinge or a fifth spherical hinge, the upper end of the electric push rod is connected with the upper end hinge, and the lower end of the electric push rod is connected with the lower end hinge.

15. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 11,

the active tensioning unit is a hydraulic cylinder, the upper end hinge is a seventh universal hinge or a sixth spherical hinge, the lower end hinge is an eighth universal hinge or a seventh spherical hinge, the upper end of the hydraulic cylinder is connected with the upper end hinge, and the lower end of the hydraulic cylinder is connected with the lower end hinge.

16. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot according to claim 1, wherein when the transmission mechanism comprises a screw rod and a screw nut, the upper end and the lower end of the screw rod are rotatably supported at the center of the outer upper platform and the center of the outer lower platform respectively, the screw nut is arranged on the screw rod, the inner platform is provided with a central hole, the inner platform is sleeved and fixed on the periphery of the screw nut through the central hole, and the actuator is coaxially fixed at the lower end of the screw rod, the transmission mechanism further comprises a polish rod and a second spring, the polish rod penetrates through the through hole of the inner platform, the upper end and the lower end of the polish rod are correspondingly fixed on the outer upper platform and the outer lower platform respectively, and the second spring is sleeved on the polish rod in a compressed state and is positioned between the outer upper platform and the inner platform.

17. The lightweight high speed four degree of freedom cable drive parallel robot of claim 16 wherein the drive mechanism further includes a second linear bearing mounted in the bore through which the polish rod passes.

18. The lightweight high-speed four-degree-of-freedom cable-driven parallel robot of claim 1,

when the transmission mechanism comprises a transverse supporting shaft, a transverse bevel gear, a rotating shaft and a horizontal bevel gear; the transverse supporting shaft extends in a left-right direction between the outer upper platform and the outer lower platform, and the left end and the right end of the transverse supporting shaft are respectively fixed with the outer platform; the inner platform is rotatably supported on the transverse support shaft; the transverse bevel gear is arranged on the inner platform; the rotary shafts are vertically arranged and rotatably supported on the center of the outer lower platform and the transverse supporting shaft; the horizontal bevel gear is arranged on the rotating shaft and meshed with the transverse bevel gear; when the actuator is coaxially fixed at the lower end of the rotating shaft, two horizontal bevel gears are arranged, one horizontal bevel gear is positioned above the transverse supporting shaft, and the other horizontal bevel gear is positioned below the transverse supporting shaft; the transverse bevel gears are two half-split bevel gears, one half-split bevel gear is positioned on the left side of the rotating shaft and meshed with one of the two horizontal bevel gears, and the other half-split bevel gear is positioned on the right side of the rotating shaft and meshed with the other of the two horizontal bevel gears.