A wire-pulling mechanism driven three-fingered dexterous hand

Abstract

The application discloses a three-fingered dexterous hand driven by a wire traction mechanism, which can realize full drive and non-coupling characteristics. The robot dexterous hand is composed of fingers, a palm, driving motors and a tensioning mechanism. The finger part has three fingers, i.e. an index finger, a middle finger and a thumb, wherein the index finger has four joints, the middle finger has four joints, and the thumb has three joints. Each joint is controlled by a corresponding motor. The whole robot dexterous hand has eleven degrees of freedom. Within the error allowable range, each joint realizes physical non-coupling, i.e. the motion of each joint does not interfere with each other. The robot dexterous hand can realize the grasping of small objects and can skillfully grasp objects such as shuttlecocks.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of robot dexterous hand design and production, and particularly relates to a three-finger dexterous hand driven by a wire pulling mechanism. BACKGROUND

[0002] A robot dexterous hand is a new type of end effector. It is a robot product designed and manufactured to achieve functions similar to human hands. Human hands are one of the important organs of the human body. With five-fingered hands, we can grasp tools and complete a series of other actions. Human beings have high intelligence. In addition to the eyes that perceive information and the brain that processes information, the hands that can achieve fine operation are also important reasons. Research on the design and production of robot dexterous hands is of great significance to industrial production, scientific research and other aspects.

[0003] There are many classifications of dexterous hands. In terms of the correspondence between transmission methods, joints and the number of driving sources, different structures and methods are often used in different dexterous hands. Different structures and methods eventually form dexterous hands, and the performance of the dexterous hands will be affected according to the different structures and methods. Because the motor is too large, it cannot be directly installed at the joint of the dexterous hand, so a transmission method is needed to make the motor rear-mounted. The transmission methods mainly include link transmission, gear transmission, belt transmission and wire transmission. Among them, the wire transmission has the advantages of small occupied volume and flexible arrangement, and is suitable for use in dexterous hands. At the same time, the wire transmission needs a corresponding tensioning mechanism, and how to reduce the size of the tensioning mechanism is a research topic of wire transmission design.

[0004] According to the correspondence between the number of joints and the number of driving sources, it can be divided into two categories: underactuated dexterous hand and fully actuated dexterous hand. The number of driving sources of the fully actuated dexterous hand is equal to the number of joints controlled by the dexterous hand, while the number of joints controlled by the underactuated dexterous hand is greater than the number of driving sources. Relatively speaking, the underactuated dexterous hand has smaller volume, easier control, but smaller degree of freedom, such as DART Hand, SSSA MyH Hand, etc.; the fully actuated dexterous hand has larger volume, more difficult control, but more degree of freedom, and can achieve more complex control effect, such as Shadow Hand, MLR Hand, etc. At the same time, for the fully actuated dexterous hand, "joint decoupling" is a very important problem. There are many joints in the fully actuated dexterous hand and the space is small. These joints cannot be coupled, otherwise it will be difficult to control the dexterous hand. The current decoupling methods include hardware decoupling and software decoupling, that is, solving the non-coupling problem through hardware design and indirectly solving the non-coupling problem through software design. At the same time, the number of fingers of the fully actuated dexterous hand is difficult to customize, and it is difficult to change the number of fingers according to the demand, so the modular design of the fingers is also an important research topic.

[0005] Both full-drive dexterous hand and under-drive dexterous hand have advantages and disadvantages, wherein the full-drive dexterous hand has more degrees of freedom, but most of the cost is very high, and the coupling problem is usually solved completely by using software, which puts high requirements on the accuracy of the dexterous hand and increases the damage rate of the dexterous hand. SUMMARY

[0006] The present application aims at the deficiencies of the prior art, and provides a three-finger dexterous hand driven by a wire pulling mechanism.

[0007] The present application aims at the deficiencies of the prior art, and provides a three-finger dexterous hand driven by a wire pulling mechanism.

[0008] The knuckles in the index finger, middle finger and thumb are connected by a bidirectional wire rope, and the knuckles are divided by a master-slave double guide rail mode.

[0009] Further, the index finger, middle finger and thumb are modularized fingers, which are composed of a first curved knuckle, a second curved knuckle, a third curved knuckle and a fourth swing knuckle, wherein the index finger and middle finger strictly comply with the modularized finger structure, the thumb has three knuckles and lacks the fourth swing knuckle, and the third curved knuckle of the thumb is replaced by a heterogeneous third curved knuckle.

[0010] Further, each knuckle of the index finger, middle finger and thumb is made of resin material, and the connecting pieces between the knuckles are composed of micro bearings.

[0011] Further, the bidirectional wire rope connection comprises:

[0012] The rotating shafts in the active joints of each knuckle are provided with circular grooves, and the circular grooves have two positionally opposite holes, and each hole is fixed with a wire rope, and the two wire ropes are wound in the circular groove in different directions;

[0013] The wire ropes at the active joints are divided by the master-slave double guide rail mechanism and pass through the guide rails in the knuckles and palm to reach the rotating shaft of the driving motor.

[0014] The rotating shaft of the driving motor is also provided with a circular groove, and the circular groove has two positionally opposite holes, and each hole is fixed with a wire rope, and the two wire ropes are wound in the circular groove in different directions, and the wire ropes are connected with the tensioning mechanism.

[0015] Further, the master-slave double guide rail mode realizes the branch line, specifically including: the knuckles include a master guide rail and a slave guide rail, each knuckle connected wire rope enters the slave guide rail, and the wire rope enters the next knuckle part and enters the master guide rail.

[0016] Further, the wire rope is connected with the tensioning mechanism, specifically including:

[0017] At the rotating shaft of the driving motor, the two wire ropes pass through the hole of the circular groove, and are knotted with each other in the circular groove, the knot is connected with the spring, and the tensioning of the wire rope is realized through the spring-based tensioning mechanism.

[0018] Further, the spring-based tensioning mechanism includes a spring, a fixed rod, a limiting rod and a limiting device, one end of the spring is connected with the wire rope, the other end is connected with the fixed rod, the fixed rod is fixed in position through the two limiting rods, and the two limiting rods pass through the limiting groove of the limiting device to adjust the fixed rod and control the elongation of the spring.

[0019] Further, the spring is located above the motor and on the center line of the motor.

[0020] Further, the motor is internally provided with an encoder for capturing the rotation angle of the motor.

[0021] Further, the device further includes a single-chip microcomputer device for reading the angle value of the encoder and sending a control instruction to the motor.

[0022] The beneficial effects of the present application are:

[0023] Firstly, the present application solves the problem of too large size of high degree of freedom dexterous hand through the transmission mode and bidirectional connection scheme of wire transmission, and realizes the design of dexterous hand with the size of human hand.

[0024] Secondly, the present application solves the problem of serious hardware coupling of high degree of freedom dexterous hand through the master-slave double guide rail scheme, and realizes the design of hardware decoupling and full-drive dexterous hand.

[0025] Thirdly, the present application solves the problem of difficult customization of high degree of freedom dexterous hand through the modularized finger design, and achieves the effect that the number of fingers can be increased or reduced according to the demand.

[0026] Fourthly, the spring-based tensioning mechanism constructed by the present application solves the problem of too large size of the tensioning mechanism, and can realize the size adjustment of the tensioning force with small size. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of a three-fingered dexterous hand driven by a wire pulling mechanism proposed by the present application;

[0028] Figure 2is a schematic diagram of a two-way wire rope connecting mode proposed by the present application;

[0029] Figure 3 is a schematic diagram of the corresponding rotation relationship of the two-way wire rope connecting mode proposed by the present application;

[0030] Figure 4 is a schematic diagram of the internal guide rail of the dexterous hand proposed by the present application;

[0031] Figure 5 is a schematic diagram of the non-coupling principle of the dexterous hand proposed by the present application;

[0032] Figure 6 is a physical diagram of the comparison between the dexterous hand and the human hand proposed by the present application;

[0033] Figure 7 is a grasping badminton experiment diagram of the dexterous hand proposed by the present application. DETAILED DESCRIPTION

[0034] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0035] The embodiment of the present application provides a three-fingered dexterous hand driven by a wire pulling mechanism, which is used to realize a low-cost dexterous hand and dexterous operation.

[0036] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] Please refer to Figure 1 The mechanical non-coupling fully-driven dexterous hand composed of three fingers disclosed in the present application is used to realize more dexterous operation and grasping of small objects. It includes index finger 17, middle finger 16, thumb 18, palm base 10, motor base 1, motor 28 and tensioning mechanism 27.

[0038] Wherein the index finger 17, middle finger 16, and the thumb 18 are all modular fingers. The modular fingers are composed of the first curved finger joint 6, the second curved finger joint 7, the third curved finger joint 8, and the fourth swing finger joint 9. The first curved joint 2, the second curved joint 3, the third curved joint 4, and the fourth swing joint 5 are the corresponding joints of the above-mentioned finger joints. The index finger and the middle finger strictly comply with the structure of the modular finger, and the thumb, on the basis of the modular finger, omits the fourth swing finger joint 9 and makes changes to the third curved finger joint 8, using a heteromorphic third curved finger joint 19, and the heteromorphic third curved joint 30 is the corresponding joint of the above-mentioned finger joint. The micro bearing 29 and the shaft are used to connect the finger joints together. The micro bearing 29 is fixed on the next finger joint and connected with the shaft of the current finger joint, so as to realize the fixation. The index finger 17 and the middle finger 16 each have one swing degree of freedom and three rotation degrees of freedom. The thumb 18 has three rotation degrees of freedom, wherein the heteromorphic third curved finger joint 19 simulates the rotation process of the human thumb. Through the modular design, the dexterous hand can be more conveniently customized in terms of the number of fingers.

[0039] Please refer to Figure 2 In the above-mentioned mechanical non-coupling full-drive dexterous hand, the present example proposes a two-way wire rope connection mode, aiming to connect the controlled joint shaft and the driving motor shaft. The two-way connection mode realizes the clockwise and counterclockwise bidirectional rotation of a single driving motor driving a single joint. The connection mode is as follows:

[0040] Figure 2 The two rotating shafts on the left and right sides represent the controlled joint rotating shaft and the rotating shaft 20 and the driving motor rotating shaft 15. The first wire rope 25 and the second wire rope 26 represent two wire ropes driving the controlled joint counterclockwise and clockwise respectively. When the controlled joint rotating shaft 20 moves counterclockwise, the second wire rope 26 is pulled to move, and the first wire rope 25 follows the controlled joint to move. When the controlled joint moves clockwise, the first wire rope 25 is pulled to move, and the second wire rope 26 follows the controlled joint to move. According to the two-way connection mode, the first wire rope 25 and the second wire rope 26 are fixed after winding around the controlled joint rotating shaft 20 and the motor rotating shaft 15 once respectively, and the first fixed point 21, the second fixed point 22, the third fixed point 23, and the fourth fixed point 24. When moving clockwise and counterclockwise, the movement distance of the first wire rope 25 and the second wire rope 26 is consistent at all times, and the force is consistent at all times, thereby ensuring symmetry and realizing single-joint control by a single driving motor.

[0041] The connection mode realizes that the movement distance of the two wire ropes is consistent at all times, and the force is consistent at all times, and there is no problem of out of step. Single-motor stable control of a single joint is realized.

[0042] Please refer to Figure 3The rotation relationship corresponding to the above-mentioned bidirectional wire rope connection mode is a quasi-linear relationship. The rotation relationship corresponding to the above-mentioned bidirectional wire rope connection mode should be linear in theory, and there is a certain error due to factors such as friction and elastic change of wire rope length, but the error is small, and the relationship between the driving motor 28 and the controlled joint rotation angle during joint rotation basically follows a linear function. The error is relatively large at about 0 degrees, and the error is about 3 degrees. While the accuracy is relatively high at other positions, the error is below 3 degrees. Since the motor 28 of the device is controlled by specifying the absolute position to rotate, there is no cumulative error, and the error below 3 degrees can be ignored under the condition that the accuracy requirement is not high. The rotation angle formula is as follows:

[0043] θ1=Nθ2

[0044] The above-mentioned bidirectional wire rope connection relationship realizes single driving motor control of single rotation joint. The single driving motor can drive the rotation joint to move clockwise and counterclockwise in two directions, and the rotation relationship is quasi-linear, with a fixed error of about 3 degrees.

[0045] Please refer to Figure 4 In the above-mentioned mechanically uncoupled fully driven dexterous hand, guide rails are designed in each knuckle and palm base, including main guide rail 31 and slave guide rail 32. The wire ropes pass through the specially designed guide rails to realize the uncoupled design between each joint. Taking the first curved knuckle of the index finger as an example, the dexterous hand wire rope arrangement method is as follows:

[0046] For the first curved knuckle of the index finger, the two wire ropes controlling the first curved joint of the index finger pass through the first fixed point 21 and the second fixed point 22 respectively, and are knotted near the rotating shaft part, thereby fixing the wire head. The two wire ropes pass through the slave guide rail of the second curved knuckle of the index finger, and then enter the main guide rail of the second curved knuckle of the index finger through the slave guide rail of the second curved knuckle of the index finger. Then pass through the main guide rail of the third curved knuckle of the index finger and the main guide rail of the fourth swing knuckle of the index finger, and finally pass through the palm guide rail. After winding around the rotating shaft 15, the two wire ropes pass through the rotating shaft hole, and the two wire ropes intersect in the rotating shaft and are knotted. The knot of the two wire ropes is connected with the spring 14 of the tensioning mechanism 27, thereby realizing the stable tension design.

[0047] Please refer to Figure 5 The two joint control wire ropes of the above-mentioned dexterous hand are connected in the manner shown in Figure 3 . The main-slave double guide rail mode is adopted to realize the uncoupled design. In this example, a simplified model is adopted for the joints of the dexterous hand: it is assumed that the distance d1 between the axis center line and the front and rear knuckles is equal to the distance d2, and both are denoted as d. The knuckles are simplified as cuboids with a height of l. The guide wires of the two error wiring modes are circular arcs between the two knuckles. The main-slave guide rail and guide rail wire are the wiring methods adopted by the device, and the lengths of the rotating front and rear joints are d a , D a; record the uppermost end of two finger joints error winding as the first kind of error winding, the length of rotating before and after the joint is d b , b ; record the lowermost end of two finger joints error winding as the second kind of error winding, the length of rotating before and after the joint is d c , c .

[0048] The length of the three winding joints before rotating is:

[0049] d a =2

[0050]

[0051] The length of the three winding joints after rotating is:

[0052] D a =2d

[0053]

[0054] The difference before and after rotating is:

[0055] D a -d a =0

[0056]

[0057] Therefore, in the simplified model, the winding of the device has no coupling, and the length of the winding before and after rotating changes in the other two winding methods, indicating that the other two winding methods will have coupling. At the same time, in the winding method of the device, the two lines of the same joint are parallel in the guide rail, so when the controlled joint rotates, the length change of the two lines is equal at all times, and there is no problem of line rope loosening or tightening, that is, there is no symmetry problem. Therefore, the guide rail design of the device can solve the problems of non-coupling and asymmetry.

[0058] The device also designs a tensioning mechanism based on a spring 14, please refer to Figure 1 The lower end of the spring 14 is connected to the two lines after knotting, the upper end of the spring 14 is connected to the fixed rod 12, the fixed rod 12 is placed below the limiting rod 13, the limiting rod 13 passes through the limiting slot of the limiting device 11, thereby fixing the position of the limiting rod 13, and further fixing the position of the fixed rod 12 and the length of the spring 14. By adjusting the position of the limiting slot through which the limiting rod 13 passes, the length of the spring 14 is adjusted, and the size of the tensioning force is adjusted.

[0059] The above tensioning mechanism can adjust the length of the line rope when the length of the line rope elastically deforms within a certain range, so that the line rope always maintains a tensioned state.

[0060] The above device realizes the mechanical dexterous hand design of 11 active degrees of freedom of three fingers through the modular finger design, the bidirectional wire rope connection mode, the master-slave double-rail split design and the tensioning mechanism. Due to the characteristics of the bidirectional wire rope connection mode, the dexterous hand can rotate the joint through external force in the power-off state, and the joint angle can be recorded by using the motor code disc.

[0061] The general flow of the above dexterous hand operation is as follows:

[0062] Step 1, power off, set the initial pose of the motor, rotate the 11 joints by external force, and rotate the joints to the target pose.

[0063] Step 2, power on, record the motor code disc readings. The readings are the positions to which the joints need to be rotated to rotate the dexterous hand to the target pose.

[0064] Step 3, repeat the above steps 1 and 2, set multiple poses and record the code disc readings, and set multiple pose states of the dexterous hand in the movement process.

[0065] Step 4, input the motor control instructions corresponding to the set multiple pose states, and complete the operation.

[0066] Please refer to Figure 6 , Figure 6 for the dexterous hand to grasp the shuttlecock experiment. The motor 28 is controlled by the control board STM32 to rotate, thereby controlling the rotation of each joint of the dexterous hand. Please refer to Figure 6 (a) in Figure 6 , place the dexterous hand to the specified position, set the rotation angle of each joint of the dexterous hand through the above dexterous hand operation process, rotate each motor to rotate each joint to the specified angle, please refer to Figure 6 (b) in Figure 6 , and finally complete the grasping operation of the shuttlecock.

[0067] Please refer to Figure 7 , Figure 7 for the comparison between the dexterous hand of the present application and the human hand. The size of the dexterous hand is close to that of the human hand. The fingers are arranged as the index finger 17, the middle finger 16 and the thumb 18, and there are 11 degrees of freedom. Among them, the index finger 17 has one swing degree of freedom and three bending degrees of freedom; the middle finger has one swing degree of freedom and three bending degrees of freedom; the thumb 18 has three bending degrees of freedom. Meanwhile, the dexterous hand also includes a set of wire rope tensioning mechanism 27, and the whole hand includes fingers, palms, driving motors and tensioning mechanisms, and the volume is close to that of the human hand.

[0068] The above embodiment is used to explain and illustrate the present application, but not to limit the present application. Any modification and change made to the present application within the spirit and protection scope of the claims of the present application all fall within the protection scope of the present application.

Claims

1. A three-finger dexterous hand driven by a wire-pulling mechanism, characterized in that: include: The index finger, middle finger and thumb are fixed on the palm base; the palm base is connected to the motor base containing the motor, and a parallel mechanism is formed between each finger and each knuckle; The knuckles of the index finger, middle finger and thumb are connected by a bidirectional cord, and the knuckles are connected by a master-slave dual guide rail method; the bidirectional cord connection includes: The rotating shaft in the active joint of each knuckle is provided with a circular groove, and there are two holes in the circular groove at opposite positions. A rope is fixed in each hole, and the two ropes are wound in the circular groove in different directions. The wire rope at the active joint is divided into two parts by the master-slave dual guide rail mechanism and passes through the guide rails in each knuckle and palm to reach the rotating shaft of the drive motor; The rotating shaft of the driving motor is also provided with a circular groove, and there are two holes in the circular groove at opposite positions, and a rope is fixed in each hole. The two ropes are respectively wound in the circular groove in different directions, and the ropes are connected to the tensioning mechanism. The master-slave dual guide rail method for implementing line division specifically includes: the finger joint includes a main guide rail and a slave guide rail, the rope connected to each finger joint enters the slave guide rail, and is merged into the main guide rail when the rope enters the next finger joint.

2. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 1, characterized in that: The index finger, middle finger and thumb are modular fingers, which consist of a first curved knuckle, a second curved knuckle, a third curved knuckle and a fourth swinging knuckle. The index finger and middle finger strictly conform to the modular finger structure, the thumb has three knuckles and lacks the fourth swinging knuckle, and the third curved knuckle of the thumb is replaced by an isomorphic third curved knuckle.

3. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 1, characterized in that: The knuckles of the index finger, middle finger and thumb are made of resin material, and the connecting parts between the knuckles are all composed of micro bearings.

4. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 1, characterized in that: The connection between the wire rope and the tensioning mechanism specifically includes: At the rotating shaft of the drive motor, two ropes pass through the holes of the circular groove and are knotted together inside the circular groove. The knot is connected to the spring, and the ropes are tensioned by a spring-based tensioning mechanism.

5. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 4, characterized in that: The spring-based tensioning mechanism includes: a spring, a fixing rod, a limiting rod and a limiting device. One end of the spring is connected to the rope, and the other end is connected to the fixing rod. The fixing rod is fixed in position by two limiting rods. The two limiting rods pass through the limiting slots of the limiting device to adjust the fixing rod and control the elongation of the spring.

6. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 5, characterized in that: The spring is located above the motor and on the center line of the motor.

7. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 1, characterized in that: An encoder is installed inside the motor to capture the rotation angle of the motor.

8. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 7, characterized in that: The device also includes a single chip microcomputer device for reading the encoder angle value and sending control instructions to the motor.

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