Three-finger dexterous hand driven by wire traction mechanism

Abstract

The invention discloses a three-fingered dexterous hand driven by a wire traction mechanism. The three-fingered dexterous hand can realize full-drive and non-coupling characteristics. The robot dexterous hand is composed of fingers, a palm, a driving motor and a tensioning mechanism. The finger part is provided with an index finger, a middle finger and a thumb, the index finger is provided with four joints, the middle finger is provided with four joints, and the thumb is provided with three joints. And each joint is controlled by a corresponding motor. The whole robot dexterous hand has eleven degrees of freedom. The joints are physically uncoupled within an error allowable range, that is, the joints do not interfere with one another in movement. According to the robot dexterous hand, small objects can be grabbed, and objects such as shuttlecocks can be grabbed skillfully.

Description

Technical Field

[0001] The present invention relates to the technical field of design and production of robot dexterous hands, and in particular to a three-finger dexterous hand driven by a wire-pulling mechanism. Background Art

[0002] The 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. The human hand is one of the important organs of the human body. With a hand with five fingers separated, we can grasp tools and complete a series of other actions. In addition to the eyes that perceive information and the brain that processes information, the hands that can perform fine operations are also an important reason for humans to have high intelligence. 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. Different dexterous hands often use different structures and methods in terms of transmission methods, the correspondence between the number of joints and drive sources, and different structures and methods ultimately constitute a dexterous hand. Depending on the structure and method, the performance of the dexterous hand will also be affected. Because the motor is too large to be directly installed at the joint of the dexterous hand, a transmission method is needed to place the motor at the rear. The main transmission methods are connecting rod transmission, gear transmission, belt transmission and linear transmission. Among them, linear transmission has the advantages of small footprint and flexible arrangement, which is suitable for use in dexterous hands. At the same time, linear transmission requires a corresponding tensioning mechanism. How to reduce the size of the tensioning mechanism is a research topic in the design of linear transmission.

[0004] According to the correspondence between the number of joints and driving sources, dexterous hands can be divided into two categories: underactuated dexterous hands and fully-actuated dexterous hands. The number of driving sources of fully-actuated dexterous hands is equal to the number of joints of the controlled dexterous hands, while the number of controlled joints of underactuated dexterous hands is more than the number of driving sources. Relatively speaking, underactuated dexterous hands are smaller in size and easier to control, but have fewer degrees of freedom, such as DART Hand and SSSA MyH Hand; fully-actuated dexterous hands are larger in size and more difficult to control, but have more degrees of freedom and can achieve more complex control effects, such as Shadow Hand and MLR Hand. At the same time, for fully-actuated dexterous hands, "joint decoupling" is a very important issue. Fully-actuated dexterous hands have more joints and smaller space, and there should be no coupling between these joints, otherwise it will lead to the inability to control the dexterous hands. The current decoupling methods include hardware decoupling and software decoupling, that is, solving the decoupling problem through hardware design and indirectly solving the decoupling problem through software design. At the same time, the number of fingers of fully-actuated dexterous hands is difficult to customize, and it is difficult to change the number of fingers according to needs, so the modular design of fingers is also an important research topic.

[0005] Both the fully-actuated and under-actuated dexterous hands have their own advantages and disadvantages. Although the fully-actuated dexterous hands have many degrees of freedom, most of them are very expensive, and the coupling problem is usually solved entirely by software, which places high demands on the accuracy of the dexterous hands and increases the damage rate of the dexterous hands. In summary, the low-cost mechanical non-coupled fully-actuated dexterous hands have a high research value. Summary of the invention

[0006] The present invention aims to address the deficiencies of the prior art and to provide a three-finger dexterous hand driven by a wire-pulling mechanism.

[0007] The object of the present invention is achieved through the following technical solutions: a three-finger dexterous hand driven by a wire-pulling mechanism, comprising: an index finger, a middle finger and a thumb fixed on a palm base; the palm base is connected to a motor base containing a motor, and parallel mechanisms are formed between each finger and each knuckle;

[0008] The knuckles of the index finger, middle finger and thumb are connected by bidirectional cords, and the knuckles are divided by a master-slave double guide rail method.

[0009] Furthermore, 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, wherein the index finger and middle finger strictly conform to the modular finger structure, the thumb has three knuckles, lacks the fourth swinging knuckle, and the third curved knuckle of the thumb is replaced by a heterogeneous third curved knuckle.

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

[0011] Furthermore, the bidirectional cord connection includes:

[0012] 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, and a wire rope is fixed at each hole, and the two wire ropes are respectively wound in the circular groove in different directions;

[0013] The wire rope at the active joint is divided into two lines through the master-slave double guide rail mechanism, passes through the guide rails in each knuckle and palm, and reaches the rotating shaft of the drive motor;

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

[0015] Furthermore, the master-slave dual guide rail method for realizing line division specifically includes: the finger joint includes a main guide rail and a slave guide rail, the wire rope connected to each finger joint enters the slave guide rail, and merges into the main guide rail when the wire rope enters the next finger joint.

[0016] Furthermore, the connection between the wire rope and the tensioning mechanism specifically includes:

[0017] At the rotating shaft of the driving motor, two ropes pass through the holes of the circular groove and are knotted together inside the circular groove. The knotted part is connected to the spring, and the ropes are tensioned by a spring-based tensioning mechanism.

[0018] Furthermore, the spring-based tensioning mechanism includes: a spring, a fixed rod, a limit rod and a limit device, one end of the spring is connected to the rope, and the other end is connected to the fixed rod, the fixed rod is fixed in position by two limit rods, and the two limit rods pass through the limit slots of the limit device to adjust the fixed rod and control the elongation of the spring.

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

[0020] Furthermore, an encoder is installed inside the motor to capture the rotation angle of the motor.

[0021] Furthermore, the device also includes a single chip microcomputer device for reading the encoder angle value and sending control instructions to the motor.

[0022] Beneficial effects of the present invention:

[0023] First: The present invention solves the problem of the high-freedom dexterous hand being too large by adopting a linear transmission mode and a two-way connection scheme design, and realizes the design of a dexterous hand the size of a human hand.

[0024] Second: The present invention solves the problem of severe hardware coupling of the high-degree-of-freedom dexterous hand through the master-slave dual-guide rail design, and realizes hardware decoupling and full-drive dexterous hand design.

[0025] Third: The present invention solves the problem that high-degree-of-freedom dexterous hands are difficult to customize by adopting a modular finger design, thereby achieving the effect of increasing or decreasing the number of fingers according to needs.

[0026] Fourth: The spring-based tensioning mechanism constructed by the present invention solves the problem of the tensioning mechanism being too large in size, and can adjust the tensioning force with a smaller volume. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2It is a schematic diagram of a connection method of a bidirectional cord proposed by the present invention;

[0029] Figure 3 It is a schematic diagram of the rotation relationship corresponding to the connection method of the bidirectional rope proposed by the present invention;

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

[0031] Figure 5 Schematic diagram of the non-coupling principle of the dexterous hand proposed by the present invention;

[0032] Figure 6 It is a physical picture comparing the dexterous hand proposed by the present invention with a human hand;

[0033] Figure 7 This is a diagram of an experiment of grabbing a badminton with the dexterous hand proposed by the present invention. DETAILED DESCRIPTION

[0034] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0035] An embodiment of the present invention provides a three-finger dexterous hand driven by a wire-pulling mechanism, which is used to achieve a low-cost dexterous hand and dexterous operation.

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention is clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Please refer to Figure 1 The present invention discloses a mechanically non-coupled fully-driven dexterous hand composed of three fingers, which is used to achieve more dexterous operation and grasping of smaller objects. It includes an index finger 17, a middle finger 16, a thumb 18, a palm base 10, a motor base 1, a motor 28 and a tensioning mechanism 27.

[0038] Among them, the index finger 17, the middle finger 16, and the thumb 18 are all modular fingers. The modular finger consists of a first curved knuckle 6, a second curved knuckle 7, a third curved knuckle 8, and a fourth swing knuckle 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 knuckles. The index finger and the middle finger strictly conform to the modular finger structure. On the basis of the modular finger, the thumb omits the fourth swing knuckle 9, and modifies the third curved knuckle 8 to use a heterogeneous third curved knuckle 19, and the heterogeneous third curved joint 30 is the corresponding joint of the above knuckle. Each knuckle is connected to the shaft through a micro bearing 29. The micro bearing 29 is fixed on the next knuckle and connected to the current knuckle shaft to achieve fixation. The index finger 17 and the middle finger 16 each have one swinging degree of freedom and three rotational degrees of freedom. The thumb 18 has three rotational degrees of freedom, among which the heterogeneous third curved knuckle 19 imitates the rotation process of the thumb of a human hand. Through modular design, the dexterous hand can conveniently add or subtract the number of fingers according to customization.

[0039] Please refer to Figure 2 In the above mechanical non-coupled fully driven dexterous hand, this example proposes a bidirectional cable connection method, the purpose of which is to connect the controlled joint axis and the drive motor axis. This bidirectional connection method enables a single drive motor to drive a single joint to rotate clockwise and counterclockwise. The connection method is as follows:

[0040] Figure 2 The two rotating shafts in the middle represent the rotating shaft of the controlled joint and the rotating shaft 20 and the rotating shaft 15 of the driving motor respectively. The first wire rope 25 and the second wire rope 26 represent the two wire ropes driving the controlled joint counterclockwise and clockwise respectively. When the rotating shaft 20 of the controlled joint moves counterclockwise, the second wire rope 26 is pulled to move, and the first wire rope 25 follows the movement of the controlled joint. When the controlled joint is driven to move clockwise, the first wire rope 25 is pulled to move, and the second wire rope 26 follows the movement of the controlled joint. The first wire rope 25 and the second wire rope 26 are respectively wound around the rotating shaft 20 of the controlled joint and the rotating shaft 15 for one circle according to the bidirectional connection method, and then fixed to 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 moving distance of the first wire rope 25 and the second wire rope 26 is always the same, and the force size is always the same, thereby ensuring symmetry and realizing the control of a single joint by a single driving motor.

[0041] This connection method ensures that the movement distance and force of the two ropes are always consistent, and there is no step-out problem. It realizes the stable control of a single joint by a single motor.

[0042] Please refer to Figure 3, the rotation relationship corresponding to the above-mentioned two-way rope connection method is a quasi-linear relationship. Theoretically, the rotation relationship corresponding to the above-mentioned two-way rope connection method should be a linear relationship. Due to factors such as friction and changes in the elasticity of the rope length, there are certain errors, but the errors are small. During the rotation of the joint, the relationship between the driving motor 28 and the controlled joint rotation angle basically follows a linear function. The error is relatively large around 0 degrees, about 3 degrees. At other positions, the accuracy is relatively high, with an error of less than 3 degrees. Since the motor 28 of this device is controlled by specifying an absolute position to rotate, there is no cumulative error. Errors below 3 degrees can be almost ignored when the accuracy requirements are not high. The rotation angle formula is as follows:

[0043] θ1=Nθ2

[0044] The above two-way cable connection relationship realizes the control of a single rotating joint by a single drive motor. The single drive motor can drive the rotating joint to move clockwise and counterclockwise in both directions, and the rotation relationship is a quasi-linear relationship, with a maximum fixed error of about 3 degrees.

[0045] Please refer to Figure 4 In the above mechanical non-coupling full-drive dexterous hand, guide rails are designed in each knuckle and palm base, including a main guide rail 31 and a secondary guide rail 32. The wire rope passes through the special guide rail to achieve the non-coupling design between each joint. Taking the first curved knuckle of the index finger as an example, the wire rope arrangement method of the dexterous hand is as follows:

[0046] For the first curved knuckle of the index finger, two lines that control the first curved joint of the index finger pass through the first fixed point 21 and the second fixed point 22 respectively, and are both knotted near the rotating shaft to fix the thread ends. The two lines pass through the secondary guide rail of the second curved knuckle of the index finger, and then merge into the primary guide rail of the second curved knuckle of the index finger. Then they pass through the primary guide rail of the third curved knuckle of the index finger, the primary guide rail of the fourth swinging knuckle of the index finger, and finally pass through the palm guide rail. After the two lines are respectively wrapped around the motor rotating shaft 15, they pass through the holes of the rotating shaft, and the two lines intersect inside the rotating shaft and are knotted and connected. The knotted part of the two lines is connected to the spring 14 of the tensioning mechanism 27, thereby realizing a stable tension design.

[0047] Please refer to Figure 5 The two control joint cables of the above-mentioned dexterous hand pass through the joints as follows: Figure 3 The master-slave dual rail method is used to achieve non-coupling design. In this example, a simplified model is used for the dexterous hand joint: it is assumed that the distances d1 and d2 between the axis centerline and the front and rear knuckles are equal, both recorded as d. The knuckles are simplified to a cuboid with a height of l. And the wires of the two incorrect wiring methods are arcs between the two knuckles. The master-slave rail and the rail line are the wiring methods used by this device, and their lengths at the front and rear joints are d a , D a; The wrong alignment at the top of the two knuckles is the first wrong alignment, and the lengths of the joints before and after the rotation are d b , D b ; The wrong line at the bottom of the two knuckles is the second wrong line, and the lengths of the joints before and after the rotation are d c , D c .

[0048] The lengths of the three wiring joints before rotation are:

[0049] d a =2

[0050]

[0051] The lengths of the three wiring joints after rotation are:

[0052] D a =2d

[0053]

[0054] The difference before and after rotation is:

[0055] D a -d a =0

[0056]

[0057] It can be seen from this that in the simplified model, the cable arrangement of this device is not coupled, while the cable lengths of the other two cable arrangement methods will change before and after rotation, indicating that the other two cable arrangement methods will be coupled. At the same time, in the cable arrangement method of this device, the two lines of the same joint are parallel in the guide rail, so when the controlled joint rotates, the length changes of the two lines are always equal, which will not cause the problem of loose or over-tightening the lines, that is, there is no symmetry problem. Therefore, the guide rail design of this device can solve both the non-coupling and asymmetry problems at the same time.

[0058] This device also designs a tensioning mechanism based on spring 14, please refer to Figure 1 The lower end of the spring 14 is connected to the two knotted ropes, and the upper end of the spring 14 is connected to the fixed rod 12. A limit rod 13 is placed below the fixed rod 12. The limit rod 13 passes through the limit slot of the limit device 11, thereby fixing the position of the limit 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 limit slot through which the limit rod 13 passes, the length of the spring 14 is adjusted, and the tensioning force is adjusted.

[0059] The tensioning mechanism can adjust the length of the wire rope when the wire rope undergoes elastic deformation within a certain range, so that the wire rope always remains in a tensioned state.

[0060] The above device realizes the design of a mechanical dexterous hand with three fingers and 11 active degrees of freedom through modular finger design, bidirectional cable connection, master-slave dual guide rail line design and tensioning mechanism. Due to the characteristics of the bidirectional cable connection, the dexterous hand can rotate the joints by external force to rotate the drive motor 28 in the power-off state, and this operation can use the motor encoder to record the joint angle.

[0061] The general process of the above-mentioned dexterous hand operation is as follows:

[0062] Step 1: Power off, set the initial position of the motor, and use external force to rotate 11 joints to the target position.

[0063] Step 2: Power on and record the encoder readings of each motor. The readings are the positions to which each joint needs to rotate in order to rotate the dexterous hand to the target position.

[0064] Step 3: Repeat the above steps 1 and 2, set the posture multiple times and record the code disk readings, and set multiple posture states of the dexterous hand during the movement.

[0065] Step 4: Enter the motor control instructions corresponding to the set multiple posture states to complete the operation.

[0066] Please refer to Figure 6 , Figure 6 This is an experiment of grabbing a badminton with a dexterous hand. 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 In Figure 6 (a) Place the dexterous hand at the specified position, set the rotation angle of each joint of the dexterous hand through the above dexterous hand operation process, and turn each motor to make each joint rotate to the specified angle. Please refer to Figure 6 In Figure 6 (b), finally completing the badminton grabbing operation.

[0067] Please refer to Figure 7 , Figure 7 This is a comparison diagram between the actual dexterous hand of the present invention and a human hand. The size of the dexterous hand is close to that of a human hand. The fingers are arranged as the index finger 17, the middle finger 16, and the thumb 18, with a total of 11 degrees of freedom. Among them, the index finger 17 has one swinging degree of freedom and three bending degrees of freedom; the middle finger has one swinging degree of freedom and three bending degrees of freedom; the thumb 18 has three bending degrees of freedom. At the same time, the dexterous hand also includes a set of wire tensioning mechanism 27. The whole hand includes fingers, palm, drive motor and tensioning mechanism, and the volume is close to that of a human hand.

[0068] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

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 bidirectional cords, and the knuckles are divided by a master-slave double guide rail method.

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, lacks the fourth swinging knuckle, and the third curved knuckle of the thumb is replaced by a heterogeneous 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, the middle finger and the 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 bidirectional cord connection comprises: 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, and a wire rope is fixed at each hole, and the two wire ropes are respectively wound in the circular groove in different directions; The wire rope at the active joint is divided into two lines through the master-slave double guide rail mechanism, passes through the guide rails in each knuckle and palm, and reaches 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 at opposite positions in the circular groove, a wire rope is fixed at each hole, and the two wire ropes are respectively wound in the circular groove in different directions, and the wire ropes are connected to the tensioning mechanism.

5. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 4, characterized in that: The master-slave dual guide rail method for realizing line division specifically includes: the finger joint includes a main guide rail and a slave guide rail, the wire rope connected to each finger joint enters the slave guide rail, and merges into the main guide rail when the wire rope enters the next finger joint.

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

7. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 6, characterized in that: The spring-based tensioning mechanism includes: a spring, a fixed rod, a limit rod and a limit device. One end of the spring is connected to the wire rope, and the other end is connected to the fixed rod. The fixed rod is fixed in position by two limit rods. The two limit rods pass through the limit slots of the limit device to adjust the fixed rod and control the elongation of the spring.

8. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 7, characterized in that: The spring is located above the motor and at the center line of the motor.

9. 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.

10. The three-finger dexterous hand driven by a wire-pulling mechanism according to claim 9, 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.

Images