CN111421565A - Pulley type under-actuated three-joint mechanical finger structure - Google Patents

Abstract

The invention discloses a pulley type underactuated three-joint mechanical finger structure, comprising a transmission box, the transmission box is connected with three underactuated fingers through a support device, and a differential mechanism composed of two-stage movable pulleys in series is arranged on the support device. The actuating mechanism is covered with a steel wire rope. One end of the steel wire rope is connected with the transmission box, and the other end is connected with the fingertips of the three underactuated fingers. The three underactuated fingers are evenly distributed at 120°, and each underactuated finger has three degrees of freedom. . The invention has the advantages of simple structure, reasonable design, flexible and reliable grasping, and good shape and sealing characteristics.

Description

A pulley-type underactuated three-joint mechanical finger structure

technical field

The invention belongs to the technical field of mechanical production, and particularly relates to a pulley-type underactuated three-joint mechanical finger structure.

Background technique

Due to the comprehensive development of industrial automation and the continuous improvement of science and technology, the improvement of work efficiency is imminent. Pure manual labor cannot meet the requirements of industrial automation. Therefore, advanced equipment must be used to produce automated machinery to replace human labor and meet the needs of industrial automation. Among them, the manipulator is one of the important products in its development process. It not only improves the efficiency of labor production, but also replaces human beings to complete high-intensity, dangerous, repetitive and boring work, reducing human labor intensity, which can be said to kill two birds with one stone. In the machinery industry, manipulators are more and more widely used. It can be used for assembly of parts, handling, loading and unloading of processed workpieces, especially in automatic CNC machine tools and combined machine tools.

At present, manipulators have developed into an important part of flexible manufacturing systems and flexible manufacturing cells. The machine tool and the manipulator together form a flexible processing system or flexible manufacturing unit, which can save a huge workpiece conveying device, has a compact structure, and is highly adaptable. However, at present, the level of industrial manipulator technology and its engineering application in my country is still far from that of foreign countries. The scale of application and the level of industrialization are low. The research and development of manipulators directly affects the improvement of the level of automated production in my country's machinery industry. Economically , technical considerations are very necessary. Therefore, it is of great significance to carry out the research and design of the manipulator.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a pulley-type underactuated three-joint mechanical finger structure in view of the above-mentioned deficiencies in the prior art, which can realize the grasping operation by driving a three-finger, three-joint manipulator by a single motor, and the manipulator can adapt to the diameter of the manipulator. About 100mm spherical and various special-shaped objects, and the grasping is reliable, with good shape sealing characteristics.

The present invention adopts following technical scheme:

A pulley type underactuated three-joint mechanical finger structure, comprising a transmission box, the transmission box is connected with three underactuated fingers through a support device, the support device is provided with a differential mechanism composed of two-stage movable pulleys in series, and the differential mechanism is sleeved There is a steel wire rope, one end of the steel wire rope is connected to the transmission box, and the other end is connected to the fingertips of the three underactuated fingers respectively through the differential mechanism. The three underactuated fingers are evenly distributed at 120°, and each underactuated finger has three degrees of freedom. .

Specifically, the supporting device includes a fixing plate, which is arranged on the transmission box and is connected to the holding plate through three guide rods.

Further, a first sliding block and a second sliding block are respectively provided on the two adjacent guide rods, and the first sliding block and the second sliding block are correspondingly provided with a first movable pulley and a second movable pulley; one end of the wire rope is connected to the transmission The steel wire arranged in the box is connected around the shaft, and the other end is connected with the fingertips of the three under-actuated fingers respectively through the first movable pulley and the second movable pulley.

Further, the wire rope includes a first wire rope, a second wire rope and a third wire rope, one end of the first wire rope is connected with the motor in the transmission box, and the other end is fixed on the first slider; one end of the second wire rope is connected with an under-driven The fingertips of the fingers are connected, and the other end is connected with the second sliding block through the first movable pulley; the third wire rope is wound on the second movable pulley, and the two ends are respectively connected with the fingertips of the remaining two underactuated fingers.

Specifically, the underactuated finger includes a first phalanx, a second phalanx and a third phalanx, one end of the first phalanx is axially connected to the base joint, the other end is axially connected to one end of the second phalanx, and the second phalanx is axially connected to the base joint. The other end of the shaft is connected to one end of the third phalanx.

Further, a first drive wheel is provided on the connection shaft between the first knuckle and the base joint, and a second drive wheel is provided on the connecting shaft at the joint of the first knuckle and the second knuckle, and the second knuckle is connected with the second knuckle. A third driving wheel is arranged on the connecting shaft at the joint of the three knuckles.

Further, the first knuckle is provided with a first fixed pulley, and the second knuckle is provided with a second fixed pulley.

Further, a first spring is provided between the first knuckle and the base joint; a second spring is provided between the first knuckle and the second knuckle; a third knuckle is provided between the second knuckle and the third knuckle spring.

Specifically, a stepper motor is arranged in the transmission box, the stepper motor is connected with the driving bevel gear through the coupling, the driving bevel gear is meshed with the driven bevel gear sleeved on the wire around the shaft, and the two ends of the wire around the shaft are respectively It is movably connected with the protective housing through the bearing.

Compared with the prior art, the present invention at least has the following beneficial effects:

The present invention is a pulley-type underactuated three-joint mechanical finger structure, which has 9 degrees of freedom and is driven by a motor; the transmission mechanism is composed of two sets of movable pulleys connected in series. When one finger is blocked and cannot continue to rotate, the other two fingers can still continue to rotate until they fully contact the grasped object; the underactuation between the three underactuated fingers uses an actuator to drive the flexion and extension of the three fingers Action, using a differential mechanism composed of two-stage movable pulleys in series, is not only self-adaptive - that is, when one or more fingers are fixed and cannot continue to move due to resistance from contacting the grasped object, other fingers can continue to move, and When all fingers are in stable contact with the object to be grasped, the driving force should be distributed evenly to each finger through the under-actuated mechanism, and a relatively large grasping force should be ensured as far as possible during stable grasping. The object is reliable and the design is convenient and beautiful, and the three fingers are evenly distributed at 120°.

Further, the differential structure composed of two-stage movable pulleys is also one of the important conditions for realizing the underactuated principle of the manipulator. When one or more fingers are blocked and cannot continue to move due to obstacles, other fingers can continue to move due to the existence of the movable pulley, and continue to transmit the force to the next link.

Further, the support device plays the role of connecting the upper and lower parts, the fixed plate is connected with the base joint to carry the entire finger part, and the guide rod in the middle is equipped with a slider. The three guide rods not only play the role of guide rails, but also provide mechanical support. In the selection of length, width and height, according to kinematic analysis, it is determined after clarifying the length of the rope contraction and elongation when the fingers open or close the grasped object.

Further, the three underactuated fingers are respectively fixed on the holding plate of the support device through the corresponding base joints, and the proximal joint, the middle joint and the distal joint each have one degree of freedom, which not only reduces the structural complexity of the fingers, but also reduces the complexity of the fingers. Meet the requirements of envelope grabbing.

Further, the transmission box is mainly responsible for providing motion and power to the manipulator. More importantly, the reasonable design of the transmission box can ensure the under-drive effect and adaptive performance of the manipulator, and realize the simultaneous driving of three fingers and six by one drive motor. When one or two fingers are blocked from touching the grasped object and cannot continue to grasp, the other fingers can still continue to bend until they fully touch the grasped object.

To sum up, the present invention has simple structure, reasonable design, flexible and reliable grasping, and good shape-closing characteristics.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Fig. 2 is the finger structure diagram of the present invention, wherein, (a) is a structure diagram, (b) is a transmission diagram;

Fig. 3 is the motion diagram of different finger piece transmission mechanism of the present invention;

FIG. 4 is a schematic diagram of the overall layout scheme of the finger according to the present invention;

Fig. 5 is the schematic diagram of the transmission box of the present invention;

6 is a schematic diagram of a guide rod and a support according to the present invention;

FIG. 7 is an assembly diagram of a manipulator finger of the present invention.

Among them: 1. Transmission box; 2. Fixed plate; 3. Slider; 3-1. First slider; 3-2. Second slider; 4. Moving pulley; 4-1. First moving pulley; 4-2 .Second moving pulley; 5. Guide rod; 6. Steel wire rope; 6-1. The first wire rope; 6-2. The second wire rope; 6-3. The third wire rope; 7. Retaining plate; Underactuated fingers; 9-1. First knuckle; 9-2. Second knuckle; 9-3. Third knuckle; 10. First drive wheel; 11. First fixed pulley; 12. Second drive 13. The second fixed pulley; 14. The third driving wheel; 15. The first spring; 16. The second spring; 17. The third spring; . Protective housing; 22. Driven bevel gear.

Detailed ways

Please refer to FIG. 1 and FIG. 7 , a pulley-type underactuated three-joint mechanical finger structure of the present invention includes a power system, a transmission system, a support device and an underactuated finger 9 . The power system includes a transmission case 1, a support device is arranged on the transmission case 1, there are three underactuated fingers 9, which are arranged at intervals on the top of the support device, and a transmission system is arranged on the support device. The transmission system includes a steel wire rope 6, one end of the steel wire rope 6 is connected to the power input end, and the other end is fixed at the steel rings of the fingertips of three underactuated fingers and 9 fingers respectively through a differential mechanism composed of two-stage movable pulleys in series, and the whole finger passes through the steel wire rope. 6 and the drive wheel installed at each joint to transmit power and motion.

Please refer to FIG. 6, the support device includes a fixed plate 2, a guide rod 5 and a holding plate 7; the transmission system includes a slider 3, a pulley 4 and a wire rope 6; the fixed plate 2 is arranged on the transmission case 1, and the guide rods 5 include three, One end is connected to the fixing plate 2, the other end is connected to the holding plate 7, the three guide rods 5 are arranged at intervals, and the two adjacent guide rods 5 are respectively provided with a first slider 3-1 and a second slider 3-2 , the first sliding block 3-1 and the second sliding block 3-2 are correspondingly provided with a first movable pulley 4-1 and a second movable pulley 4-2; , and the other end is connected to the three underactuated fingers 9 through the first movable pulley 4-1 and the second movable pulley 4-2 respectively.

3 and 4, the wire rope 6 includes a first wire rope 6-1, a second wire rope 6-2 and a third wire rope 6-3, and the first movable pulley 4-1 is set on the first movable pulley 4-1 through the first slider 3-1 On the guide rod, the second movable pulley 4-2 is set on the second guide rod through the second slider 3-2; one end of the first wire rope 6-1 is fixed on the wire winding shaft, and is connected to the wire through the bevel gear and the coupling. The motor in the transmission box 1 is connected, and the other end is fixed on the first sliding block 3-1, which is responsible for transmitting the power generated by the motor to the first sliding block 3-1; one end of the second wire rope 6-2 passes through the first driving wheel 10. The first fixed pulley 11, the second driving wheel 12, the second fixed pulley 13, and the third driving wheel 14 are connected to the fingertip of an underactuated finger 9, which is responsible for driving the bending motion of the finger, and the other end passes through the first The movable pulley 4-1 is connected with the second sliding block 3-2 to transmit power to the second sliding block 3-2; the third wire rope 6-3 is wound on the second movable pulley 4-2, and both ends pass through the corresponding first The driving wheel 10 , the first fixed pulley 11 , the second driving wheel 12 , the second fixed pulley 13 , and the third driving wheel 14 are connected with the fingertips of the other two underactuated fingers 9 and are responsible for driving the two remaining underactuated fingers 9 finger bending motion.

Please refer to FIG. 5 , the bottom of the transmission box 1 is equipped with a stepper motor. The stepper motor is connected with the driving bevel gear 18 through a coupling. , the two ends of the wire around the shaft 15 are movably connected to the protective housing 21 through the bearing 20, the power generated by the stepping motor is sequentially transmitted to the driving bevel gear 18, the driven bevel gear 22 meshing with it, the wire around the shaft 19 and the driven bevel gear 22. The bevel gear 18 rotates together, and at the same time, the first wire rope 6-1 is wound on the wire winding shaft 15, transmitting the force to the next system.

Please refer to Figure 2. Through the functional analysis of the human hand, it is found that most of the grasping and operating processes of the human hand are mainly completed by the thumb, index finger and middle finger. The ring finger and the little finger mainly play an auxiliary role. In order to reduce the complexity of the mechanism, the fingers The number is 3. The underactuated fingers 9 include a first phalanx 9-1, a second phalanx 9-2 and a third phalanx 9-3, and each of the underactuated fingers 9 has three degrees of freedom, in order to grasp objects reliably and to facilitate design For aesthetics, the three underactuated fingers 9 are evenly distributed at 120° on the holding plate 7 .

The base joint 8 is axially connected to one end of the first phalanx 9-1, the other end of the first phalanx 9-1 is axially connected to one end of the second phalanx 9-2, and the other end of the second phalanx 9-2 is axially connected to the second phalanx 9-2. One end of the third phalanx 9-3 is axially connected. A first drive wheel 10 is arranged on the connecting shaft of the first phalanx 9-1 and the base joint 8, and a second driving wheel 10 is arranged on the connecting shaft of the joint connection between the first phalanx 9-1 and the second phalanx 9-2. A third driving wheel 14 is provided on the wheel 12, the connecting shaft where the second phalanx 9-2 and the third phalanx 9-3 are articulated.

The first drive wheel 10 is fixedly connected to the first phalanx 9-1, the second drive wheel 12 is fixedly connected to the second phalanx 9-2, and the third drive wheel 13 is fixedly connected to the third guide 9-3.

The base joint 8 of the finger is fixed on the holding plate 7, a torsion spring 15 is installed between the first knuckle 9-1 and the base knuckle 8, and a torsion is installed between the second knuckle 9-2 and the first knuckle. Spring 16, a torsion spring 17 is installed between the third knuckle 9-3 and the second knuckle. The torsion spring provides a certain spring force to ensure that the finger is normally open when the natural state of the object is not grasped.

The wire rope is wound into the first driving wheel 10 from below, around the first driving wheel 10 for one week, then passes through the first fixed pulley 11, and then winds into the second driving wheel 12 from below, and then goes around the second driving wheel 12 for one round, and then passes through the second fixed pulley 11. The pulley 13 goes around the third driving wheel 14 from below, goes around the driving wheel 14 once, and is finally fixed to the fingertip.

Since the wire rope can only bear the tension force, not the pressure or thrust, the manipulator needs to maintain a normally open state, pull the wire rope to bend the fingers to grasp, and the manipulator relies on the torsion spring at the joint to restore the initial position, so the torsion spring needs to be installed with a certain amount of The initial angle to ensure the normally open state of the finger. However, according to the design principle of the finger, the stiffness of the spring at each joint directly affects the motion state of the finger. Therefore, it is necessary to comprehensively consider various factors to select the stiffness of the spring. Through calculation, the stiffness of the torsion spring of each joint can be preliminarily determined, and then the installation can be determined. After calculation, the initial angle when the torsion spring is installed is initially determined to be 80°. However, considering the error between the calculation and the actual model, the installation of the torsion spring should have a certain margin. Therefore, when designing the structure of the manipulator finger, it is necessary to design an adjustable device to realize the installation of the initial angle of the torsion spring. A certain range of adjustment to ensure a reliable and compact normally open state of the fingers. At the same time, in order to ensure the order in which the knuckles are gradually bent when grasping the object, the stiffnesses of the torsion springs 15, 16, and 17 are sequentially increased.

The working principle of a pulley-type underactuated three-joint mechanical finger structure of the present invention is as follows:

The wire rope is wound around the three driving pulleys 10 , 12 , 14 . When the wire rope is pulled, frictional force is generated between the wire rope and the driving pulley, and a rotational torque is generated on the driving pulleys 10 , 12 , and 14 . Since the spring force of the spring 15 is small and the spring force of the springs 16 and 17 is large, it is difficult for the wire rope 6 to pull the second driving wheel 12 and the third driving wheel 14 to rotate around the corresponding axes at the beginning, so the three knuckles 9-1 , 9-2 and 9-3 as a whole, under the action of the first drive wheel 10 to overcome the restraint force of the spring 15 to rotate around the base joint 8 to realize the rotation of the base joint; when the first knuckle 9-1 contacts the object At this time, it cannot continue to rotate. At this time, the tension of the wire rope 6 increases, and the wire rope 6 pulls the second driving wheel 12 to overcome the binding force of the second spring 16, so that the second knuckle 9-2 and the third knuckle 9-3 are integrated as a whole. Rotate around the proximal joint. When the second knuckle 9-2 touches the object, it cannot continue to rotate. At this time, the tension of the wire rope 6 is further increased, and the wire rope 6 pulls the third driving wheel 14 to overcome the binding force of the third spring 17, so that the third knuckle 9-3 Rotate around the far joint. Until it stops when it touches the object, the rotation of the far joint is finally realized, and the grasping is finally realized.

The reason why the underactuated manipulator of the present invention can simultaneously drive three fingers to perform bending motion through one motor mainly depends on the principle of the moving pulley. Moving, if the force on both sides of the wire rope is uneven, the movable pulley can also rotate around its own axis. If the two ends of the wire rope are respectively fixed on the fingertips of the two fingers, then the wire rope can drive the two fingers to move at the same time, and if two movable pulleys are connected in series, one output end of the first-stage movable pulley is directly connected to a Drive the finger, and the other output end is connected to the second-stage movable pulley, then the two movable pulleys in series can drive the three under-actuated fingers to bend at the same time.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention all fall within the scope of the claims of the present invention. within the scope of protection.

Claims (9)

1. The pulley type under-actuated three-joint mechanical finger structure is characterized by comprising a transmission case (1), wherein the transmission case (1) is connected with three under-actuated fingers (9) through a supporting device, a differential mechanism formed by connecting two stages of movable pulleys in series is arranged on the supporting device, a steel wire rope (6) is sleeved on the differential mechanism, one end of the steel wire rope (6) is connected with the transmission case (1), the other end of the steel wire rope is respectively connected with finger tips of the three under-actuated fingers (9) through the differential mechanism, the three under-actuated fingers (9) are uniformly distributed at 120 degrees, and each under-actuated finger (9) has three degrees of freedom.

2. The pulley type under-actuated three-joint mechanical finger structure according to claim 1, wherein the supporting device comprises a fixing plate (2), the fixing plate (2) is arranged on the transmission case (1) and connected with a retaining plate (7) through three guide rods (5), the retaining plate (7) is provided with three base joints (8), and the three base joints (8) are correspondingly connected with three under-actuated fingers (9).

3. The pulley type under-actuated three-joint mechanical finger structure according to claim 2, wherein a first sliding block (3-1) and a second sliding block (3-2) are respectively arranged on two adjacent guide rods (5), and a first movable pulley (4-1) and a second movable pulley (4-2) are correspondingly arranged on the first sliding block (3-1) and the second sliding block (3-2); one end of the steel wire rope (6) is connected with a steel wire shaft (19) arranged in the transmission case (1), and the other end of the steel wire rope is respectively connected with the fingertips of the three under-actuated fingers (9) through a first movable pulley (4-1) and a second movable pulley (4-2).

4. The pulley type under-actuated three-joint mechanical finger structure according to claim 3, wherein the steel wire rope (6) comprises a first steel wire rope (6-1), a second steel wire rope (6-2) and a third steel wire rope (6-3), one end of the first steel wire rope (6-1) is connected with a motor in the transmission case (1), and the other end of the first steel wire rope is fixed on the first sliding block (3-1); one end of a second steel wire rope (6-2) is connected with the fingertip of an under-actuated finger (9), and the other end of the second steel wire rope is connected with a second sliding block (3-2) through a first movable pulley (4-1); a third steel wire rope (6-3) is wound on the second movable pulley (4-2), and two ends of the third steel wire rope are respectively connected with the finger tips of the remaining two under-actuated fingers (9).

5. The pulley type under-actuated three-joint mechanical finger structure according to claim 1, wherein the under-actuated finger (9) comprises a first knuckle (9-1), a second knuckle (9-2) and a third knuckle (9-3), one end of the first knuckle (9-1) is connected with the base joint (8) through a shaft, the other end of the first knuckle is connected with one end of the second knuckle (9-2) through a shaft, and the other end of the second knuckle (9-2) is connected with one end of the third knuckle (9-3) through a shaft.

6. The pulley type under-actuated three-joint mechanical finger structure according to claim 5, wherein a first driving wheel (10) is arranged on a connecting shaft of the first knuckle (9-1) and the base joint (8), a second driving wheel (12) is arranged on a connecting shaft at the joint of the first knuckle (9-1) and the second knuckle (9-2), and a third driving wheel (14) is arranged on a connecting shaft at the joint of the second knuckle (9-2) and the third knuckle (9-3).

7. The pulley type under-actuated three-joint mechanical finger structure according to claim 5, wherein a first fixed pulley (11) is arranged on the first knuckle (9-1), and a second fixed pulley (13) is arranged on the second knuckle (9-2).

8. The pulley type under-actuated three-joint mechanical finger structure according to claim 5, wherein a first spring (15) is arranged between the first knuckle (9-1) and the base joint (8); a second spring (16) is arranged between the first knuckle (9-1) and the second knuckle (9-2); a third spring (16) is arranged between the second knuckle (9-2) and the third knuckle (9-3).

9. The pulley type under-actuated three-joint mechanical finger structure according to claim 1, wherein a stepping motor is arranged in the transmission case (1), the stepping motor is connected with a driving bevel gear (18) through a coupler, the driving bevel gear (18) is engaged with a driven bevel gear (22) sleeved on a steel wire shaft (19), and two ends of the steel wire shaft (19) are movably connected with a protective shell (21) through bearings (20).

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