A rigid-flexible coupled dexterous hand finger and control method thereof

Abstract

The application discloses a kind of rigid-flexible coupling dexterous hand fingers, including a finger base, a fingertip module and multiple knuckles;The fingertip module includes fingertip, tendon, fingertip base and fingertip fixing frame, the tendon and fingertip are made of flexible elastic material, the fingertip is installed on the fingertip fixing frame, the tendon is used to connect the fingertip fixing frame and the fingertip base;Each knuckle includes knuckle bracket and a knuckle servo fixedly installed on knuckle bracket, and finger base servo is also fixedly installed on the finger base;In order from the finger base to the fingertip, the finger base servo is used to control the movement of the first knuckle, the last knuckle servo is used to control the movement of the fingertip base, and the other knuckle servo is used to control the movement of the next knuckle.The application also discloses a kind of rigid-flexible coupling dexterous hand finger control method.

Description

Technical Field

[0001] This invention relates to the field of dexterity technology, and in particular to a rigid-flexible coupled dexterity finger and its control method. Background Technology

[0002] As an important end effector for humanoid robots, dexterous hands, compared to traditional robotic hands that can only perform specific tasks, have the advantages of high flexibility and versatility. They can endow robots with more precise manipulation capabilities and stronger environmental adaptability, and are an important way to promote humanoid robots towards general artificial intelligence. At present, research on dexterous hands mainly focuses on dexterous hands made of rigid materials and soft dexterous hands made of artificial muscles.

[0003] Dexterous hands made of rigid materials often employ cable-driven mechanisms. These hands typically use a motor as the drive unit, with gear or pulley transmissions working in conjunction with the motor to drive the cable, thereby controlling the various joints and enabling complex, high-precision motion control. While dexterous hands made of rigid materials offer advantages such as high energy conversion efficiency and good force control, their rigid structure poses safety hazards when manipulating fragile objects and engaging in human-machine interaction, making them unsuitable for everyday tasks.

[0004] Soft dexterous hands composed of artificial muscles are often gas-driven. Gas actuation controls the opening and closing force and speed of the fingers by adjusting air pressure, offering advantages such as fast response speed and simple structure. Although soft dexterous hands composed of artificial muscles have the characteristics of convenient energy storage, good compliance, and high safety, their dynamic control performance is relatively poor.

[0005] The fingers are the foundation of a dexterous hand; therefore, research on the structure and control algorithms of a dexterous hand often begins with the fingers. To balance the safety and dynamic control performance of a dexterous hand, it is necessary to improve the structure and control algorithms of the fingers. Summary of the Invention

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A dexterous hand finger with rigid-flexible coupling, comprising a finger base, a fingertip module, and multiple phalanges;

[0008] The fingertip module includes a fingertip, a tendon, a fingertip base, and a fingertip fixing frame. The tendon and fingertip are made of a soft, elastic material. The fingertip is mounted on the fingertip fixing frame, and the tendon is used to connect the fingertip fixing frame and the fingertip base.

[0009] Each phalanx includes a phalanx support and a phalanx servo fixedly mounted on the phalanx support, and a finger base servo is also fixedly mounted on the base of the finger.

[0010] In sequence from the base of the finger to the fingertip, the base of the finger servo controls the movement of the first phalanx, the last phalanx servo controls the movement of the fingertip base, and the other phalanx servos control the movement of the next phalanx.

[0011] In some embodiments, the plurality of phalanges includes a first phalange, a second phalange, and a third phalange, wherein the first phalange includes a first phalange servo and a first phalange bracket, the second phalange includes a second phalange servo and a second phalange bracket, and the third phalange includes a third phalange servo and a third phalange bracket.

[0012] In some embodiments, the dexterous hand fingers are used to simulate the thumb, the finger base servo is used to control the flexion and extension movement of the first phalanx, the first phalanx servo is used to control the lateral movement of the second phalanx, the second phalanx servo is used to control the flexion and extension movement of the third phalanx, and the third phalanx servo is used to control the flexion and extension movement of the fingertip base.

[0013] In some embodiments, the output shafts of the finger base servo, the second knuckle servo, and the third knuckle servo are all perpendicular to the direction when the fingers of the dexterous hand are extended, and the output shaft of the first knuckle servo is all in the same direction as the fingers of the dexterous hand are extended.

[0014] Furthermore, the output shaft of the finger base servo is fixedly connected to the bottom side of the first phalanx support, the output shaft of the second phalanx servo is fixedly connected to the bottom side of the third phalanx support, and the output shaft of the third phalanx servo is fixedly connected to the bottom side of the fingertip base, thereby realizing the control of flexion and extension movements;

[0015] The output shaft of the first knuckle servo is fixedly connected to the bottom surface of the second knuckle bracket, thereby realizing the control of rotary motion.

[0016] In some embodiments, the dexterous hand fingers are used to simulate any finger other than the thumb, the finger base servo is used to control the flexion and extension movement of the first phalanx, the first phalanx servo is used to control the lateral movement of the second phalanx, the second phalanx servo is used to control the flexion and extension movement of the third phalanx, and the third phalanx servo is used to control the flexion and extension movement of the fingertip base.

[0017] In some embodiments, the direction of the output shaft of the finger base servo is consistent with the direction when the fingers of the dexterous hand are straight, and the directions of the output shafts of the first knuckle servo, the second knuckle servo, and the third knuckle servo are all perpendicular to the direction when the fingers of the dexterous hand are straight.

[0018] The output shaft of the servo motor at the base of the finger is fixedly connected to a first bevel gear, and the bottom end of the first phalanx bracket is fixedly connected to a second bevel gear. The first bevel gear and the second bevel gear mesh with each other and the included angle between them is 90 degrees, thereby transmitting the motion of the servo motor output shaft to the first phalanx to control the flexion and extension motion of the first phalanx.

[0019] The output shaft of the first knuckle servo is fixedly connected to the middle of the side of the second knuckle bracket to control the lateral swing motion of the second knuckle;

[0020] The output shaft of the second phalanx servo is fixedly connected to the bottom side of the third phalanx bracket to control the flexion and extension movement of the third phalanx;

[0021] The output shaft of the third phalanx servo is fixedly connected to the bottom side of the fingertip base to control the flexion and extension movement of the fingertip base.

[0022] In some embodiments, the finger base is fixedly mounted on the palm base, and the palm base is also equipped with a palm base servo motor;

[0023] The hand-based servo motor is equipped with a steel wire, and a winding wheel is fixedly installed on the output shaft of the hand-based servo motor;

[0024] One end of the steel wire is wound around the winding wheel, and the other end is fixedly connected to the side of the fingertip fixing frame facing the palm base;

[0025] The hand-based servo motor is used to control the bending of the tendon via a steel wire.

[0026] A method for controlling the fingers of a rigid-flexible coupled dexterous hand, employing the aforementioned rigid-flexible coupled dexterous hand fingers, includes the following steps:

[0027] S1. Establish a kinematic model of the fingers of a dexterous hand. When modeling, the first phalanx servo, the second phalanx servo, the third phalanx servo, and the finger base servo are collectively regarded as four rotary joints.

[0028] S2, Receive control instructions to obtain the desired position of the fingertips of the dexterous hand;

[0029] S3. Based on the kinematic model established in step S1, calculate the spatial vector of the rotational joint corresponding to the fingers of the dexterous hand through inverse kinematic mapping.

[0030] S4. Then, calculate the servo drive vector corresponding to the spatial vector of the rotary joint through inverse kinematic mapping.

[0031] S5. Control the working state of the corresponding servo motor according to the calculation results in step S4.

[0032] In some embodiments, step S1, the step of establishing the kinematic model of the dexterous hand, specifically includes:

[0033] Establish a coordinate system for each rotary joint, denoted as O. i -X i Y i Z i (i = 1, 2, 3, 4), the origin O in the coordinate system i Located at the geometric center of the servo, Z i The axis orientation is the direction of the output axis, X i The axis direction is the direction in which the fingers of the dexterous hand point when they are fully extended. Finally, the Y-axis is selected according to the right-hand coordinate system rules. i The orientation of the axis;

[0034] The DH parameter table for each revolute joint is derived. Based on the chain rule, the derivation formula for the homogeneous transformation matrix of the (i+1)th revolute joint relative to the ith revolute joint is shown below:

[0035]

[0036] In equation (1), R X (α i Describe the rotational joint first around X i Axis rotation α i Angle, then through translation transformation D X (a i ) so that the joint is along X i Axis translation a i Distance, then transformed by rotation R Z (θ i+1 ) around Z i+1 Axis rotation θ i+1 Angle, finally transformed by translation D Z (d i+1 ) Along Z i+1 Axis translation d i+1 The distance, i.e., realizing the rotational transformation from the i-th rotational joint to the (i+1)-th rotational joint, and obtaining The general expression:

[0037]

[0038] To make the expression concise, define Based on the derived DH parameter table, the homogeneous transformation matrix of each rotational joint is derived. As shown in the following formula:

[0039]

[0040] Among them, matrix and The definitions are shown in equations (4), (5), (6), and (7):

[0041]

[0042]

[0043]

[0044]

[0045] Furthermore, for the sake of concise description (3) The elements of the definition (3) Equation (3) can be rearranged as follows:

[0046]

[0047] The specific mathematical formulas for each element are shown below:

[0048]

[0049] In the above formula, we define Thus, Equations (8) and (9) describe the influence of rotational joint variables on the position and posture of the fingertips of a dexterous hand.

[0050] In some embodiments, in step S3, referring to equation (8), the position vector of the fingertips of the dexterous hand is represented as: The desired position vector is represented as x * =[p x * p y * p z * ] T Define the space vector of the rotational joint as Where θ i (i = 1, 2, 3, 4) represents the rotation angle of the i-th servo motor. The goal of the inverse kinematics mapping calculation is to obtain the desired position vector x. * The spatial vector q of the revolute joint is obtained by solving for the following derivation:

[0051] Multiply the left side of equation (8) by a homogeneous transformation matrix get:

[0052]

[0053] Given that the first row and fourth column, the second row and fourth column, and the third row and fourth column of the left and right matrices in equation (10) are equal, we can obtain:

[0054]

[0055] From the second equation in (11), we can solve for θ1:

[0056]

[0057] Squaring the first and third equations in equation (11) yields θ3:

[0058]

[0059] in, In the above formula, θ3 has two solutions, and the value is taken as the one closest to the current position;

[0060] Substituting θ1 and θ3 into equation (11), we obtain θ2:

[0061]

[0062] Let equation (8) be multiplied on the left at the same time. get:

[0063]

[0064] Given that the first row and first column of the left and right sides of equation (15) are equal to the second row and second column, we get:

[0065] θ4=Atan2(s4,c4), (16)

[0066] The mathematical descriptions of s4 and c4 are as follows:

[0067]

[0068]

[0069] Where r 11 r 21 r 31 As shown in equation (9);

[0070] Combining equations (12), (13), (14), and (16), the desired position vector x is thus given. * Then, the spatial vector q of the rotational joint can be calculated through inverse kinematic mapping;

[0071] In step S4, the servo drive vector is defined. Where u i (i = 1, 2, 3, 4) represents the driving voltage of the i-th servo. The goal of the inverse kinematics mapping calculation is to solve for the corresponding servo driving vector u through the spatial vector q of the rotary joint. The specific derivation process is as follows:

[0072] The positive kinematic mapping from the servo drive vector to the rotary joint space vector is a linear mapping, that is:

[0073] q = Au (19)

[0074] Where A is a diagonal matrix, A = diag[0.24 0.24 0.24] T The mathematical description of the corresponding inverse kinematic mapping is as follows:

[0075] u = A -1 q (20).

[0076] Compared with existing technologies, the beneficial effects of the rigid-flexible coupled dexterous hand fingers and their control method provided by this invention are as follows: Addressing the technical shortcomings of existing dexterous hands in balancing dynamic control performance and safety performance, this invention employs a unique design in its rigid-flexible coupling method, combining rigid knuckles with flexible fingertips and tendons, and utilizing a special control method to effectively balance dynamic control performance and safety performance. This results in a dexterous hand with better compliance and higher safety performance compared to dexterous hands based on rigid materials, and higher control precision and better dynamic control performance compared to soft dexterous hands based on artificial muscles. Attached Figure Description

[0077] Figure 1 This is a schematic diagram of the fingers of a dexterous hand with rigid-flexible coupling in the first embodiment;

[0078] Figure 2 This is a schematic diagram of the fingers of a dexterous hand with rigid-flexible coupling in the second embodiment;

[0079] Figure 3 A schematic diagram of the hand-based servo motor and related structures;

[0080] Figure 4 This is a diagram showing the connection point between two knuckles;

[0081] Figure 5 This is a schematic diagram of establishing a coordinate system for each rotational joint of the fingers of a dexterous hand.

[0082] Explanation of icon numbers:

[0083] 1. First knuckle; 11. First knuckle support; 12. First knuckle servo; 13. Second bevel gear; 2. Second knuckle; 21. Second knuckle support; 22. Second knuckle servo; 23. Output shaft; 24. Hex bolt; 3. Third knuckle; 31. Third knuckle support; 32. Third knuckle servo; 4. Hand base; 41. Hand base servo; 42. Steel wire; 43. Winding reel; 5. Finger base servo; 51. First bevel gear; 6. Fingertip; 7. Tendon; 8. Fingertip base; 9. Fingertip retainer. Detailed Implementation

[0084] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following detailed embodiments further illustrate how this invention is implemented.

[0085] Reference Figure 1 or Figure 2 As shown, the present invention provides a dexterous hand finger with rigid-flexible coupling, including a finger base, a fingertip module, and multiple phalanges; the fingertip module includes a fingertip 6, a tendon 7, a fingertip base 8, and a fingertip fixing frame 9. The tendon 7 and the fingertip 6 are made of a flexible elastic material. The fingertip 6 is mounted on the fingertip fixing frame 9, and the tendon 7 is used to connect the fingertip fixing frame 9 and the fingertip base 8; each phalanx includes a phalanx support and a phalanx servo fixedly mounted on the phalanx support, and a finger base servo 5 is also fixedly mounted on the finger base; in the order from the finger base to the fingertip 6, the finger base servo 5 is used to control the movement of the first phalanx, the last phalanx servo is used to control the movement of the fingertip base 8, and the other phalanx servos are used to control the movement of the next phalanx.

[0086] In addition, the two ends of the tendon 7 can be connected to the fingertip base 8 and fingertip fixation frame 9 on the upper and lower sides through straight grooves. The fingertip 6 can be glued to the fingertip fixation frame 9, thus realizing the coupling of rigid and flexible mechanisms. The tendon 7 and fingertip 6 are made of soft elastic materials, such as silicone casting; the rigid mechanisms such as the fingertip base 8 and knuckle support can be made using 3D printing technology.

[0087] Preferably, the plurality of phalanges includes a first phalange 1, a second phalange 2, and a third phalange 3. The first phalange 1 includes a first phalange servo 12 and a first phalange bracket 11. The second phalange 2 includes a second phalange servo 22 and a second phalange bracket 21. The third phalange 3 includes a third phalange servo 32 and a third phalange bracket 31.

[0088] Reference Figure 1 As shown, in the first embodiment, the dexterous hand fingers are used to simulate any finger other than the thumb. The finger base servo 5 is used to control the flexion and extension movement of the first phalanx 1, the first phalanx servo 12 is used to control the lateral movement of the second phalanx 2, the second phalanx servo 22 is used to control the flexion and extension movement of the third phalanx 3, and the third phalanx servo 32 is used to control the flexion and extension movement of the fingertip base 8.

[0089] Specifically, the output shaft of the finger base servo 5 is oriented in the same direction as the direction of the dexterous hand's fingers when extended. The output shafts of the first knuckle servo 12, the second knuckle servo 22, and the third knuckle servo 32 are all perpendicular to the direction of the dexterous hand's fingers when extended. A first bevel gear 51 is fixedly connected to the output shaft of the finger base servo 5, and a second bevel gear 13 is fixedly connected to the bottom end of the first knuckle support 11. The first bevel gear 51 and the second bevel gear 13 mesh with each other, and the included angle between them is 90 degrees. This transmits the motion of the servo motor output shaft to the first phalanx 1 to control the flexion and extension of the first phalanx 1; the output shaft of the first phalanx servo motor 12 is fixedly connected to the middle side of the second phalanx bracket 21 to control the lateral swing of the second phalanx 2; the output shaft of the second phalanx servo motor 22 is fixedly connected to the bottom side of the third phalanx bracket 31 to control the flexion and extension of the third phalanx 3; the output shaft of the third phalanx servo motor 32 is fixedly connected to the bottom side of the fingertip base 8 to control the flexion and extension of the fingertip base 8.

[0090] Reference Figure 2 As shown, in the second embodiment, the difference from the first embodiment is that the dexterous hand fingers are used to simulate the thumb, the finger base servo 5 is used to control the flexion and extension movement of the first phalanx 1, the first phalanx servo 12 is used to control the lateral movement of the second phalanx 2, the second phalanx servo 22 is used to control the flexion and extension movement of the third phalanx 3, and the third phalanx servo 32 is used to control the flexion and extension movement of the fingertip base 8.

[0091] Specifically, the output shafts of the finger base servo 5, the second knuckle servo 22, and the third knuckle servo 32 are all perpendicular to the direction when the fingers of the dexterous hand are extended, and the output shaft of the first knuckle servo 12 is consistent with the direction when the fingers of the dexterous hand are extended. Furthermore, the output shaft of the finger base servo 5 is fixedly connected to the bottom side of the first knuckle support 11, the output shaft of the second knuckle servo 22 is fixedly connected to the bottom side of the third knuckle support 31, and the output shaft of the third knuckle servo 32 is fixedly connected to the bottom side of the fingertip base 8, thereby realizing the control of flexion and extension movements; the output shaft of the first knuckle servo 12 is fixedly connected to the bottom surface of the second knuckle support 21, thereby realizing the control of rotational movements.

[0092] Because the thumb is located on the front side of the other four fingers (hereinafter referred to as ordinary fingers), it has the ability to oppose itself, enabling it to move closer to or further away from one or more other fingers in an opposing motion. Therefore, the thumb occupies a very important position among all parts of the human hand. The transmission design of this rigid-flexible coupled dexterous hand's fingers references the structure and function of the human hand, employing two different transmission design methods for the thumb and ordinary fingers in two different embodiments.

[0093] In the first embodiment, for the fingers 10 of a typical dexterous hand, to improve structural compactness, the finger base servo 5 and the first phalanx support 11 are connected by two bevel gears, thereby achieving motion transmission of flexion and extension degrees of freedom within a limited space. Multiple flexion and extension degrees of freedom work together to achieve the function of finger bending; while the lateral swing degree of freedom is achieved by the second phalanx 2 rotating around the output shaft of the first phalanx servo 12, realizing the lateral swing motion of the finger on the horizontal plane, thus making the movement of the dexterous hand fingers more flexible, while increasing the redundancy of the dexterous hand's degrees of freedom.

[0094] In the second embodiment, the thumb's ability to oppose the palm is achieved by the coordinated work of the rotational degree of freedom and the remaining flexion and extension degrees of freedom. The multiple flexion and extension degrees of freedom work together to achieve the function of thumb bending, while the rotational degree of freedom is achieved by the second phalanx 2 rotating around the output shaft of the first phalanx servo motor 12, realizing a function similar to the joint of the human hand, expanding the range of motion of the thumb, and enabling the thumb to complete both opposing and counter-opposing movements.

[0095] Based on the analysis of human hand structure and finger function, two different finger transmission methods were designed. When this invention is applied to the overall dexterous hand structure, the dexterous hand fingers in the above two embodiments can be combined, for example, using one thumb and four ordinary fingers, enabling the dexterous hand to perform both palm-opposing and palm-fighting movements.

[0096] Further reference Figure 3 As shown, preferably, the base of the finger is fixedly mounted on the palm base 4, and a palm base servo 41 is also mounted on the palm base 4; the palm base servo 41 is equipped with a steel wire 42, and a winding wheel 43 is fixedly mounted on the output shaft of the palm base servo 41; one end of the steel wire 42 is wound on the winding wheel 43, and the other end is fixedly connected to the side of the fingertip fixing bracket 9 facing the palm base 4; the palm base servo 41 is used to control the bending of the tendon 7 through the steel wire 42.

[0097] Understandable, Figure 3 The illustration shows the situation corresponding to the first embodiment, where the dexterous hand fingers are used to simulate ordinary fingers; for the second embodiment, when the dexterous hand fingers are used to simulate anything other than the thumb, the palm base servo motor 41, steel wire 42, winding wheel 43 and other structures can also be used to achieve control over the bending of the tendon 7.

[0098] Furthermore, the steel wire 42 can pass through a pre-set hole on the fingertip base 8 and then be fixedly connected to the fingertip fixing frame 9 to limit the range of motion of the steel wire 42. The output shaft of the hand base servo motor 41 drives the winding wheel 43 to rotate forward or backward, controlling the stretching motion of the steel wire 42. When the steel wire 42 pulls the tendon 7, it causes the tendon 7 to bend under force; when the tension of the steel wire 42 on the tendon 7 decreases, the tendon 7 returns to its original position under its own elastic force. In this way, reliable control of the fingertip bending freedom is achieved, meeting the design requirements for compliance and safety performance of the dexterous hand's fingers.

[0099] As can be seen, in both embodiments, the dexterous hand fingers are equipped with five servo motors: a palm base servo motor 41, a finger base servo motor 5, and three knuckle servo motors. That is, each finger has five degrees of freedom, so that the rigid-flexible coupled dexterous hand fingers exhibit kinematic characteristics and configurations similar to human fingers, achieving the purpose of dexterous movement.

[0100] Furthermore, considering the control precision and dynamic performance requirements of the dexterous hand's fingers, this rigid-flexible coupled dexterous hand finger employs a simple, integrated drive design within the dexterous hand itself. The servo motor can be an HTS-20L type. (Refer to...) Figure 4 As shown, when the servo motor is connected to its driving structure, taking the second knuckle servo motor 22 and the third knuckle support 31 in the second embodiment as an example, the lower end of the third knuckle support 31 has a threaded hole. The third knuckle support 31 is fixed to the output shaft 23 of the second knuckle servo motor 22 by hexagonal bolts 24, thereby transmitting the rotation of the output shaft 23 to the third knuckle support 31. In this way, the offset angle of each knuckle on the control surface can be precisely controlled, achieving simple and efficient motion transmission between different knuckle levels, thus realizing the dexterity of the hand. Except for special cases (such as the finger base servo motor 5 and the first knuckle support 11 being driven by two bevel gears in the first embodiment), most servos and their driving structures can achieve motion transmission in a similar manner.

[0101] The hardware control system of this rigid-flexible coupled dexterous hand finger can consist of a control module, a communication module, an I / O module, a power supply module, a sensor module, and a host computer. The control module can use an STM32F103 microcontroller; the sensor module can include multiple visual and tactile sensors, each positioned at a different location on the dexterous hand finger. The control module connects to each servo and sensor via serial communication and physically connects to the host computer via USB, using serial communication to send the current motion status of each servo to the host computer and receive control commands from the host computer, thus achieving closed-loop control of the dexterous hand finger. The I / O module can send control commands from the remote control to the control module, enabling human-computer interaction functionality for the dexterous hand finger.

[0102] Another aspect of the present invention provides a method for controlling the fingers of a rigid-flexible coupled dexterous hand, employing the aforementioned rigid-flexible coupled dexterous hand fingers, and comprising the following steps:

[0103] S1. Establish a kinematic model of the fingers of a dexterous hand. When modeling, the first phalanx servo 12, the second phalanx servo 22, the third phalanx servo 32 and the finger base servo 5 are used together as the four rotational joints of the fingers of a dexterous hand.

[0104] Understandably, although each finger of a dexterous hand has five degrees of freedom, including the four servos mentioned above as four rotational units and the finger base servo 5 for controlling the bending of the tendons 7, the finger base servo 5 operates relatively independently. It controls the corresponding tendon 7 one-to-one via the wire 42. When the operation of other servos causes a change in the overall position of the dexterous hand's fingers, the finger base servo 5 only needs to maintain the bending angle of the tendon 7 in the required state. Therefore, it is only necessary to treat the other four servos as rotational joints and model them accordingly.

[0105] The specific steps involved in establishing a kinematic model of the fingers of a dexterous hand include:

[0106] Reference Figure 5 As shown, this figure corresponds to Figure 1 In the first embodiment, dexterous hand fingers are used to simulate ordinary fingers; it is understood that in the second embodiment, the modeling of dexterous hand fingers is based on the same principle.

[0107] Establish a coordinate system for each rotary joint, denoted as O. i -X i Y i Z i (i = 1, 2, 3, 4), the origin O in the coordinate system i Located at the geometric center of the servo, Z i The axis orientation is the direction of the output axis, X i The axis direction is the direction in which the fingers of the dexterous hand point when they are fully extended. Finally, the Y-axis is selected according to the right-hand coordinate system rules. i The orientation of the axis;

[0108] The DH parameter table for each rotary joint is derived, as shown in Table 1:

[0109] Table 1. DH Parameters of Rotational Joints

[0110]

[0111] Based on the chain rule, the derivation formula for the homogeneous transformation matrix of the (i+1)th rotation joint relative to the ith rotation joint is as follows:

[0112]

[0113] In equation (1), R X (α i Describe the rotational joint first around X i Axis rotation α i Angle, then through translation transformation D X (a i ) so that the joint is along X i Axis translation a i Distance, then transformed by rotation R Z (θ i+1 ) around Z i+1 Axis rotation θ i+1 Angle, finally transformed by translation D Z (d i+1 ) Along Z i+1 Axis translation d i+1 The distance, i.e., realizing the rotational transformation from the i-th rotational joint to the (i+1)-th rotational joint, and obtaining The general expression:

[0114]

[0115] To make the expression concise, define Based on the derived DH parameter table, the homogeneous transformation matrix of each rotational joint is derived. As shown in the following formula:

[0116]

[0117] Among them, matrix and The definitions are shown in equations (4), (5), (6), and (7):

[0118]

[0119]

[0120]

[0121]

[0122] Furthermore, for the sake of concise description (3) The elements of the definition (3) Equation (3) can be rearranged as follows:

[0123]

[0124] The specific mathematical formulas for each element are shown below:

[0125]

[0126] In the above formula, we define Thus, Equations (8) and (9) describe the influence of rotational joint variables on the position and posture of the fingertips of a dexterous hand.

[0127] S2. Accept control commands to obtain the desired position of the fingertips of the dexterous hand, such as accepting commands sent from the host computer to the control module for the dexterous hand fingers.

[0128] S3. Based on the kinematic model established in step S1, calculate the spatial vector of the rotational joint corresponding to the fingers of the dexterous hand through inverse kinematic mapping.

[0129] Referring to equation (8), the position vector of the fingertips of a dexterous hand is represented as follows: The desired position vector is represented as x * =[p x * p y * p z * ] T Define the space vector of the rotational joint as Where θ i (i = 1, 2, 3, 4) represents the rotation angle of the i-th servo motor. The goal of the inverse kinematics mapping calculation is to obtain the desired position vector x. * The spatial vector q of the revolute joint is obtained by solving for the following derivation:

[0130] Multiply the left side of equation (8) by a homogeneous transformation matrix get:

[0131]

[0132] Given that the first row and fourth column, the second row and fourth column, and the third row and fourth column of the left and right matrices in equation (10) are equal, we can obtain:

[0133]

[0134] From the second equation in (11), we can solve for θ1:

[0135]

[0136] Squaring the first and third equations in equation (11) yields θ3:

[0137]

[0138] in, In the above formula, θ3 has two solutions, and the value is taken as the one closest to the current position;

[0139] Substituting θ1 and θ3 into equation (11), we obtain θ2:

[0140]

[0141] Let equation (8) be multiplied on the left at the same time. get:

[0142]

[0143] Given that the first row and first column of the left and right sides of equation (15) are equal to the second row and second column, we get:

[0144] θ4=Atan2(s4,c4), (16)

[0145] The mathematical descriptions of s4 and c4 are as follows:

[0146]

[0147]

[0148] Where r 11 r 21 r 31 As shown in equation (9);

[0149] Combining equations (12), (13), (14), and (16), the desired position vector x is thus given. * Then, the spatial vector q of the rotational joint can be calculated through inverse kinematic mapping.

[0150] S4. Then, calculate the servo drive vector corresponding to the spatial vector of the rotary joint through inverse kinematic mapping.

[0151] Define servo drive vector Where u i (i = 1, 2, 3, 4) represents the driving voltage of the i-th servo. The goal of the inverse kinematics mapping calculation is to solve for the corresponding servo driving vector u through the spatial vector q of the rotary joint. The specific derivation process is as follows:

[0152] The positive kinematic mapping from the servo drive vector to the rotary joint space vector is a linear mapping, that is:

[0153] q = Au (19)

[0154] Where A is a diagonal matrix, A = diag[0.24 0.24 0.24] T The mathematical description of the corresponding inverse kinematic mapping is as follows:

[0155] u = A -1 q (20).

[0156] S5. Control the working state of the corresponding servo motor according to the calculation results in step S4.

[0157] As can be seen, according to the control method of the dexterous hand with rigid-flexible coupling provided by the present invention, given the desired position of the fingertip, the spatial vector of the rotary joint is calculated by inverse kinematic mapping, and the servo drive vector is further calculated by inverse kinematic mapping, so that the precise control of the position of the fingertip of the dexterous hand can be achieved.

[0158] In summary, the rigid-flexible coupled dexterous hand fingers and their control method provided by this invention address the technical shortcomings of existing dexterous hands that struggle to balance dynamic control performance and safety performance. It employs a unique design in its rigid-flexible coupling method, combining rigid knuckles with flexible fingertips and tendons, and utilizes a special control method to effectively balance dynamic control performance and safety performance. As a result, this dexterous hand exhibits better compliance and higher safety performance compared to dexterous hands based on rigid materials, and higher control precision and better dynamic control performance compared to soft dexterous hands based on artificial muscles.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dexterous hand finger with rigid-flexible coupling, characterized in that, It includes a finger base, a fingertip module, and multiple phalanges; The fingertip module includes a fingertip (6), a tendon (7), a fingertip base (8), and a fingertip fixing frame (9). The tendon (7) and the fingertip (6) are made of a soft elastic material. The fingertip (6) is mounted on the fingertip fixing frame (9). The tendon (7) is used to connect the fingertip fixing frame (9) and the fingertip base (8). Each phalanx includes a phalanx support and a phalanx servo fixedly mounted on the phalanx support, and a finger base servo is also fixedly mounted on the base of the finger (5). In the order from the base of the finger to the fingertip (6), the base of the finger servo (5) is used to control the movement of the first phalanx, the last phalanx servo is used to control the movement of the fingertip base (8), and the other phalanx servos are used to control the movement of the next phalanx. Multiple phalanges include a first phalange (1), a second phalange (2) and a third phalange (3). The first phalange (1) includes a first phalange servo (12) and a first phalange bracket (11). The second phalange (2) includes a second phalange servo (22) and a second phalange bracket (21). The third phalange (3) includes a third phalange servo (32) and a third phalange bracket (31). The output shaft of the finger base servo (5) is fixedly connected to a first bevel gear (51), and the bottom end of the first phalanx bracket (11) is fixedly connected to a second bevel gear (13). The first bevel gear (51) and the second bevel gear (13) mesh with each other and the included angle between them is 90 degrees, thereby transmitting the motion of the servo output shaft to the first phalanx (1) to control the flexion and extension motion of the first phalanx (1). The base of the finger is fixedly installed on the palm base (4), and a palm base servo (41) is also installed on the palm base (4). The palm base servo (41) is equipped with a steel wire (42), and a winding wheel (43) is fixedly installed on the output shaft of the palm base servo (41). One end of the steel wire (42) is wound on the winding wheel (43), and the other end is fixedly connected to the side of the fingertip fixing bracket (9) facing the palm base (4); The hand base servo (41) is used to control the bending of the tendon (7) via a steel wire (42).

2. The dexterous hand finger with rigid-flexible coupling according to claim 1, characterized in that, The dexterous hand fingers are used to simulate the thumb. The finger base servo (5) is used to control the flexion and extension movement of the first phalanx (1), the first phalanx servo (12) is used to control the lateral movement of the second phalanx (2), the second phalanx servo (22) is used to control the flexion and extension movement of the third phalanx (3), and the third phalanx servo (32) is used to control the flexion and extension movement of the fingertip base (8).

3. The dexterous hand finger with rigid-flexible coupling according to claim 2, characterized in that, The output shafts of the finger base servo (5), the second knuckle servo (22) and the third knuckle servo (32) are all perpendicular to the direction when the fingers of the dexterous hand are straight, and the output shaft of the first knuckle servo (12) is consistent with the direction when the fingers of the dexterous hand are straight. Furthermore, the output shaft of the finger base servo (5) is fixedly connected to the bottom side of the first knuckle support (11), the output shaft of the second knuckle servo (22) is fixedly connected to the bottom side of the third knuckle support (31), and the output shaft of the third knuckle servo (32) is fixedly connected to the bottom side of the fingertip base (8), thereby realizing the control of flexion and extension movements; The output shaft of the first knuckle servo motor (12) is fixedly connected to the bottom surface of the second knuckle bracket (21), thereby realizing the control of rotary motion.

4. The dexterous hand finger with rigid-flexible coupling according to claim 1, characterized in that, The dexterous hand is used to simulate any finger except the thumb. The finger base servo (5) is used to control the flexion and extension of the first phalanx (1), the first phalanx servo (12) is used to control the lateral movement of the second phalanx (2), the second phalanx servo (22) is used to control the flexion and extension of the third phalanx (3), and the third phalanx servo (32) is used to control the flexion and extension of the fingertip base (8).

5. The dexterous hand finger with rigid-flexible coupling according to claim 4, characterized in that, The direction of the output shaft of the finger base servo (5) is consistent with the direction when the fingers of the dexterous hand are straightened, and the directions of the output shafts of the first knuckle servo (12), the second knuckle servo (22) and the third knuckle servo (32) are all perpendicular to the direction when the fingers of the dexterous hand are straightened; The output shaft of the first knuckle servo (12) is fixedly connected to the middle of the side of the second knuckle bracket (21) to control the lateral swing motion of the second knuckle (2); The output shaft of the second phalanx servo (22) is fixedly connected to the bottom side of the third phalanx bracket (31) to control the flexion and extension movement of the third phalanx (3); The output shaft of the third knuckle servo motor (32) is fixedly connected to the bottom side of the fingertip base (8) to control the flexion and extension movement of the fingertip base (8).

6. A method for controlling the fingers of a rigid-flexible coupled dexterous hand, characterized in that, The dexterous hand fingers with rigid-flexible coupling as described in any one of claims 1-5 are used, and the process includes the following steps: S1. Establish a kinematic model of the fingers of a dexterous hand. When modeling, the first phalanx servo (12), the second phalanx servo (22), the third phalanx servo (32), and the finger base servo (5) are used together as four rotational joints. S2, Receive control instructions to obtain the desired position of the fingertips of the dexterous hand; S3. Based on the kinematic model established in step S1, calculate the spatial vector of the rotational joint corresponding to the fingers of the dexterous hand through inverse kinematic mapping. S4. Then, calculate the servo drive vector corresponding to the spatial vector of the rotary joint through inverse kinematic mapping. S5. Control the working state of the corresponding servo motor according to the calculation results in step S4.

7. The method for controlling the fingers of a rigid-flexible coupled dexterous hand according to claim 6, characterized in that, In step S1, the steps for establishing the kinematic model of the dexterous hand specifically include: Establish a coordinate system for each rotary joint, denoted as follows: ( i =1,2,3,4), the origin of the coordinate system Located at the geometric center of the servo motor, The shaft orientation is the direction of the output shaft. The axis direction is the direction in which the fingers of the dexterous hand point when they are fully extended, and is finally selected using the rules of the right-hand coordinate system. The orientation of the axis; The DH parameter table for each revolute joint is derived. Based on the chain rule, the derivation formula for the homogeneous transformation matrix of the (i+1)th revolute joint relative to the ith revolute joint is shown below: (1) In equation (1), Describe the rotational joint first around Axis rotation Angle, then through translation transformation Make the joint along Axis translation Distance, then transformed by rotation Around Axis rotation Angle, finally transformed by translation. Along Axis translation Distance, i.e., achieving distance from the first i The first rotational joint to the... i +1 rotational transformation of the joints, and obtain The general expression: (2) To make the formula concise, define , Based on the derived DH parameter table, the homogeneous transformation matrix of each rotational joint is derived. As shown in the following formula: (3) Among them, matrix , , and The definitions are shown in equations (4), (5), (6), and (7): (4) (5) (6) (7) Furthermore, for the sake of concise description (3) The elements of , in definition (3), , Equation (3) can be rearranged as follows: (8) The specific mathematical formulas for each element are shown below: (9) In the above formula, we define , , , Thus, equations (8) and (9) describe the influence of rotational joint variables on the position and posture of the fingertips of a dexterous hand.

8. The method for controlling the fingers of a rigid-flexible coupled dexterous hand according to claim 7, characterized in that, In step S3, referring to equation (8), the position vector of the fingertips of the dexterous hand is expressed as: The desired position vector is represented as Define the space vector of the rotational joint as ,in ( i =1,2,3,4) represents the first... i The rotation angle of each servo motor, the goal of inverse kinematics mapping calculation is to obtain the desired position vector. Solve for the spatial vector of the revolute joint. The specific derivation process is as follows: Multiply the left side of equation (8) by a homogeneous transformation matrix ,get: (10) Given that the first row and fourth column, the second row and fourth column, and the third row and fourth column of the left and right matrices in equation (10) are equal, we can obtain: (11) From the second equation in equation (11), we can obtain : (12) Squaring the first and third equations in equation (11) yields : (13) in, In the above formula There are two solutions; the value chosen is the one closest to the current position. Will , Substituting into equation (11), we get : (14) Let equation (8) be multiplied on the left at the same time. ,get: (15) Given that the first row and first column of the left and right sides of equation (15) are equal to the second row and second column, we get: (16) in and The mathematical description is as follows: ， (17) ， (18) in , , As shown in equation (9); Combining equations (12), (13), (14), and (16), the desired position vector is thus given. Then, the spatial vector of the rotational joint can be calculated through inverse kinematic mapping. ; In step S4, the servo drive vector is defined. ,in ( i =1,2,3,4) represents the first... i The driving voltage of each servo motor, the goal of the inverse kinematics mapping calculation is to obtain the spatial vector of the rotational joint. Solve for the corresponding servo drive vector The specific derivation process is as follows: The positive kinematic mapping from the servo drive vector to the rotary joint space vector is a linear mapping, that is: (19) Among them is diagonal matrix The mathematical description of the corresponding inverse kinematic mapping is as follows: (20)。

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