Dexterous hand control system and method

Abstract

The invention discloses a control system and method for a dexterous hand. The system comprises a dexterous hand body, a control module, a power module, a camera, a sensor module and an upper computer. The dexterous hand body comprises a palm base and a plurality of finger units, each finger unit comprises a finger base part, a fingertip module and a plurality of knuckles, the finger base parts are fixedly mounted on the palm base, and each finger unit comprises a plurality of steering engines for controlling the movement of the finger unit; the fingertip module comprises a fingertip, a tendon, a fingertip base and a fingertip fixing frame, the tendon and the fingertip are made of flexible elastic materials, the fingertip is installed on the fingertip fixing frame, and the tendon is used for connecting the fingertip fixing frame and the fingertip base; the power module is used for supplying power to the system; the camera is arranged on the palm base and used for collecting visual image information; the control module is connected with the camera, each sensor in the sensor module and each steering engine through signal lines, and is connected with the upper computer.

Description

Technical Field

[0001] The present invention relates to the technical field of dexterous hands, and in particular to a control system and method for a dexterous hand. Background Art

[0002] As an important end effector of a humanoid robot, compared with a traditional manipulator that can only perform specific tasks, a dexterous hand has the advantages of high flexibility and strong versatility, and can endow the robot with more precise operation ability and stronger environmental adaptability, which is an important way to promote the humanoid robot towards general artificial intelligence.

[0003] At present, the research on dexterous hands mainly focuses on dexterous hands composed of rigid materials and soft dexterous hands composed of artificial muscles. The dexterous hand composed of rigid materials has the advantages of high energy conversion efficiency and good force control effect, but its rigid structure has potential safety hazards in the process of manipulating fragile objects and performing human-machine interaction, and it is difficult to be applied to daily life tasks. The soft dexterous hand composed of artificial muscles has the characteristics of convenient energy storage, good compliance, high safety, etc., but its control dynamic performance is poor.

[0004] Therefore, in order to balance the safety performance and control dynamic performance of the dexterous hand, it is necessary to improve the structure, control system and control algorithm of the dexterous hand. Summary of the Invention

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A control system for a dexterous hand, comprising a dexterous hand body, a control module, a power supply module, a camera, a sensor module and a host computer;

[0007] The dexterous hand body includes a palm base and a plurality of finger units. Each finger unit includes a finger base, a fingertip module and a plurality of phalanges. The finger base is fixedly installed on the palm base, and each finger unit includes a plurality of servos to control its own movement;

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

[0009] The power supply module is used to supply power to the whole system;

[0010] The camera is arranged on the palm base and is used to collect visual image information;

[0011] The control module is respectively connected to the camera, each sensor in the sensor module and each servo through signal lines, and is connected to the host computer;

[0012] The control module is used to receive the information collected by the camera and the sensor module, send the motion state of each current servo to the host computer, and at the same time receive the control instructions sent by the host computer to realize the closed-loop control of the dexterous hand body.

[0013] In some embodiments, for any finger unit, each phalanx includes a phalanx bracket and a phalanx servo fixedly installed on the phalanx bracket, and a finger base servo is also fixedly installed on the finger base;

[0014] In the order from the finger base to the fingertip, the finger base servo is used to control the movement of the first phalanx, the last phalanx servo is used to control the movement of the fingertip base, and other phalanx servos are used to control the movement of the next phalanx.

[0015] In some embodiments, for any finger unit, multiple phalanges include a first phalanx, a second phalanx and a third phalanx. The first phalanx includes a first phalanx servo and a first phalanx bracket, the second phalanx includes a second phalanx servo and a second phalanx bracket, and the third phalanx includes a third phalanx servo and a third phalanx bracket.

[0016] In some embodiments, the number of finger units is five, including one thumb unit and four ordinary finger units with the same structure;

[0017] For the thumb unit, 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 rotation 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;

[0018] For any ordinary finger unit, 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 swing 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.

[0019] In some embodiments, a plurality of palm base servos are further installed on the palm base, and the plurality of palm base servos correspond to the plurality of finger units one by one;

[0020] Each palm base servo is provided with a steel wire, and a wire winding wheel is fixedly installed on the output shaft of the palm base servo;

[0021] One end of the steel wire is wound on the wire winding wheel, and the other end is fixedly connected to the side of the fingertip fixing frame facing the palm base;

[0022] The palm base servo is used to control the bending of the tendon through the steel wire.

[0023] In some embodiments, an I / O module and a remote controller are further included. The I / O module is configured to send the control instructions of the remote controller to the control module to implement the human-computer interaction function of the dexterous hand.

[0024] On the other hand, the present invention provides a control method for a dexterous hand, which adopts the above-mentioned control system of the dexterous hand and includes the following steps:

[0025] S1. Establish a kinematic model of the dexterous hand. When modeling any finger unit, the first knuckle servo, the second knuckle servo, the third knuckle servo, and the finger base servo are jointly used as the four rotational joints of the finger unit;

[0026] S2. For any finger unit, the host computer sends an instruction for the finger unit to the control module to obtain the desired position of the end of the finger unit;

[0027] S3. Based on the kinematic model established in step S1, calculate the spatial vector of the corresponding rotational joint of the finger unit through inverse kinematic mapping;

[0028] S4. Then calculate the servo drive vector corresponding to the spatial vector of the rotational joint through inverse kinematic mapping;

[0029] S5. Control the working state of the corresponding servo according to the calculation result in step S4.

[0030] In some embodiments, in step S1, the steps of establishing the kinematic model of the dexterous hand specifically include:

[0031] Establish coordinate systems for each rotational joint, denoted as O i -X i Y i Z i (i = 1, 2, 3, 4). The origin O in the coordinate system i is located at the geometric center of the servo, the direction of the Z i axis is the direction of the output axis, the direction of the X i axis is the direction in which the finger unit points in the straight state, and finally the orientation of the Y i axis is selected according to the right-hand coordinate system rule;

[0032] Deduce the D-H parameter table of each rotational joint. Based on the chain rule, the formula for deriving the homogeneous transformation matrix of the (i + 1)-th rotational joint relative to the i-th rotational joint is as follows:

[0033]

[0034] In formula (1), R X (α i)Describe that the rotary joint first rotates around the X i axis by an angle α i and then undergoes a translation transformation D X (a i ) such that the joint translates along the X i axis by a distance a i Subsequently, through a rotation transformation R Z (θ i+1 ) it rotates around the Z i+1 axis by an angle θ i+1 Finally, through a translation transformation D Z (d i+1 ) it translates along the Z i+1 axis by a distance d i+1 That is, the rotation transformation from the i-th rotary joint to the (i + 1)-th rotary joint is achieved, and the general expression of is obtained:

[0035]

[0036] To simplify the expression, define Combined with the derived D-H parameter table, the homogeneous transformation matrix of each rotary joint is derived as shown in the following formula:

[0037]

[0038] Among them, the matrices and are defined as shown in the following formulas (4), (5), (6), and (7):

[0039]

[0040] Furthermore, to describe the elements of in formula (3) concisely, define the elements in formula (3) as Formula (3) is rearranged as follows:

[0041]

[0042] The specific mathematical formulas of each element are as follows:

[0043]

[0044] In the above formula, define Thus, the influence of the rotary joint variables on the position and attitude of the finger unit end is described through formulas (8) and (9).

[0045] In some embodiments, in step S3, for any finger unit, referring to formula (8), its end position vector is expressed as The desired position vector is denoted as x * =[p x * p y * p z * T , and the spatial vector of the revolute joint is defined as where θ i (i = 1, 2, 3, 4) represents the rotation angle of the i-th servo. The goal of the inverse kinematics mapping calculation is to solve for the spatial vector q of the revolute joint through the desired position vector x * . The specific derivation process is as follows:

[0046] Multiply a homogeneous transformation matrix on the left side of equation (8) to obtain:

[0047]

[0048] Given that the elements in the first row and fourth column, second row and fourth column, and third row and fourth column of the left and right matrices in equation (10) are equal, we can obtain:

[0049]

[0050] From the second equation in equation (11), we can solve for θ1:

[0051]

[0052] After squaring the first and third equations in equation (11), we can obtain θ3:

[0053]

[0054] where There are two solutions for θ3 in the above equation, and the value is taken as the one closest to the current position;

[0055] Substitute θ1 and θ3 into equation (11) to solve for θ2:

[0056]

[0057] Then multiply equation (8) on the left side by to obtain:

[0058]

[0059] Given that the elements in the first row and first column and second row and second column of the left and right sides of equation (15) are equal, we obtain:

[0060] θ4 = Atan2(s4, c4), (16) ​

[0061] The mathematical descriptions of s4 and c4 are as follows:

[0062]

[0063] where r 11 、r 21 、r 31 as shown in Equation (9);

[0064] Combining Equations (12), (13), (14), and (16), given the desired position vector x * after that, the spatial vector q of the rotary joint can be calculated through the inverse kinematic mapping.

[0065] In some embodiments, in step S4, the servo drive vector is defined where u i (i = 1, 2, 3, 4) represents the drive voltage of the i-th servo. The goal of the inverse kinematic mapping calculation is to solve the corresponding servo drive vector u through the spatial vector q of the rotary joint. The specific derivation process is as follows:

[0066] The forward kinematic mapping from the servo drive vector to the rotary joint spatial vector is a linear mapping, that is:

[0067] q = Au (19)

[0068] where A is a diagonal matrix A = diag[0.24 0.24 0.24] T , then the mathematical description of the corresponding inverse kinematic mapping is as follows:

[0069] u = A -1 q (20).

[0070] Compared with the prior art, the beneficial effects of the control system and method of the dexterous hand provided by the present invention are as follows: The present invention adopts a special control system and method, and combines rigid finger joints and flexible fingertips and tendons, effectively balancing the control dynamic performance and safety performance; thus enabling the dexterous hand to have better compliance and higher safety performance compared with the dexterous hand based on rigid materials, and having higher control accuracy and better dynamic control performance compared with the soft dexterous hand based on artificial muscles. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 is a schematic diagram of the control system of the dexterous hand provided by the present invention;

[0072] Figure 2 is a schematic diagram of the dexterous hand body;

[0073] Figure 3 is a schematic diagram of a common finger unit;

[0074] Figure 4 Schematic diagram of the thumb finger unit;

[0075] Figure 5 Schematic diagram of the palm base servo and related structures;

[0076] Figure 6 Schematic diagram of the connection between two finger joints;

[0077] Figure 7 Schematic diagram of establishing a coordinate system for each rotating joint of the finger unit.

[0078] Explanation of the reference numerals in the drawings:

[0079] 1. First finger joint; 11. First finger joint bracket; 12. First finger joint servo; 13. First bevel gear; 2. Second finger joint; 21. Second finger joint bracket; 22. Second finger joint servo; 23. Output shaft; 24. Hexagon bolt; 3. Third finger joint; 31. Third finger joint bracket; 32. Third finger joint servo; 4. Palm base; 41. Palm base servo; 42. Steel wire; 43. Winding wheel; 5. Finger base servo; 51. Second bevel gear; 6. Finger tip; 7. Tendon; 8. Finger tip base; 9. Finger tip fixing bracket; 10. Ordinary finger unit; 20. Thumb unit; 100. Control module; 200. Power module; 300. Camera; 400. Sensor module; 500. Host computer; 600. I / O module; 700. Remote controller. Specific implementation manners

[0080] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific implementation manners on how it is implemented.

[0081] Refer to Figures 1 - 3As shown, in a specific embodiment, the present invention provides a control system for a dexterous hand, including a dexterous hand body, a control module 100, a power supply module 200, a camera 300, a sensor module 400, and a host computer 500; the dexterous hand body includes a palm base 4 and a plurality of finger units, and each finger unit includes a finger base, a fingertip module, and a plurality of phalanges. The finger base is fixedly installed on the palm base 4, and each finger unit includes a plurality of servos to control its own movement; 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 installed on the fingertip fixing frame 9, and the tendon 7 is used to connect the fingertip fixing frame 9 and the fingertip base 8; the power supply module 200 is used to supply power to the entire system; the camera 300 is arranged on the palm base 4 and is used to collect visual image information; the control module 100 is connected to each sensor in the camera 300 and the sensor module 400 and each servo through signal lines, and is connected to the host computer 500; the control module 100 is used to receive the information collected by the camera 300 and the sensor module 400, send the current movement states of each servo to the host computer 500, and at the same time receive the control instructions sent by the host computer 500 to achieve the closed-loop control of the dexterous hand body.

[0082] Further, the control system for the dexterous hand provided by the present invention further includes an I / O module 600 and a remote controller 700. The I / O module 600 is used to send the control instructions of the remote controller 700 to the control module 100 to achieve the human-computer interaction function of the dexterous hand.

[0083] In this embodiment, the control module 100 can adopt an stm32f103 type microcontroller, and the sensor module can include a plurality of visual and tactile sensors, which are respectively arranged at different positions of the dexterous hand. The control module 100 can be connected to each servo and sensor through serial communication, and is physically connected to the host computer 500 through USB. Using the serial port as the communication method, the current movement states of each servo are sent to the host computer.

[0084] Further, for any finger unit, each phalanx includes a phalanx bracket and a phalanx servo fixedly installed on the phalanx bracket, and a finger base servo 5 is also fixedly installed 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 other phalanx servos are used to control the movement of the next phalanx.

[0085] In addition, referring to Figure 3As shown, both ends of the tendon 7 can be connected to the fingertip base 8 and the fingertip fixing frame 9 on the upper and lower sides through straight notches. The fingertip 6 can be attached to the fingertip fixing frame 9 with glue, thus realizing the coupling of the rigid mechanism and the flexible mechanism. The tendon 7 and the fingertip 6 are made of flexible elastic materials, such as being cast with silicone; the rigid mechanisms such as the fingertip base 8 and the phalanx bracket can be obtained by 3D printing technology.

[0086] Preferably, for any finger unit, the multiple phalanges include the first phalanx 1, the second phalanx 2 and the third phalanx 3. The first phalanx 1 includes the first phalanx servo 12 and the first phalanx bracket 11. The second phalanx 2 includes the second phalanx servo 22 and the second phalanx bracket 21. The third phalanx 3 includes the third phalanx servo 32 and the third phalanx bracket 31.

[0087] Preferably, the number of finger units is five, including one thumb unit 20 and four ordinary finger units 10 with the same structure.

[0088] Further referring to Figure 4 As shown, for the thumb unit 20, 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 rotation 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. The third phalanx servo 32 is used to control the flexion and extension movement of the fingertip base 8.

[0089] Specifically, for the thumb unit 20, the directions of the output shafts of the finger base servo 5, the second phalanx servo 22 and the third phalanx servo 32 are all perpendicular to the direction when the thumb unit 20 is straightened. The direction of the output shaft of the first phalanx servo 12 is the same as the direction when the thumb unit 20 is straightened; and, the output shaft of the finger base servo 5 is fixedly connected to the bottom side of the first phalanx bracket 11. The output shaft of the second phalanx servo 22 is fixedly connected to the bottom side of the third phalanx bracket 31. The output shaft of the third phalanx servo 32 is fixedly connected to the bottom side of the fingertip base 8, thus realizing the control of the flexion and extension movement; the output shaft of the first phalanx servo 12 is fixedly connected to the bottom surface of the second phalanx bracket 21, thus realizing the control of the rotation movement.

[0090] Referring to Figure 3 As shown, for any ordinary finger unit 10, 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 side swing 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. The third phalanx servo 32 is used to control the flexion and extension movement of the fingertip base 8.

[0091] Specifically, for any ordinary finger unit 10, the direction of the output shaft of the finger base servo 5 is consistent with the direction when the ordinary finger unit 10 is straightened, and the directions of the output shafts of the first phalanx servo 12, the second phalanx servo 22, and the third phalanx servo 32 are all perpendicular to the direction when the ordinary finger unit 10 is straightened; the output shaft of the finger base servo 5 is fixedly connected with a first bevel gear 51, and the bottom end of the first phalanx bracket 11 is fixedly connected with a second bevel gear 13. The first bevel gear 51 and the second bevel gear 13 are meshed with each other and the included angle between them is 90 degrees, so as to transmit the movement of the servo output shaft to the first phalanx 1 to control the flexion and extension movement of the first phalanx 1; the output shaft of the first phalanx servo 12 is fixedly connected with the middle part of the side surface of the second phalanx bracket 21 to control the lateral swing movement of the second phalanx 2; the output shaft of the second phalanx servo 22 is fixedly connected with the bottom side surface of the third phalanx bracket 31 to control the flexion and extension movement of the third phalanx 3; the output shaft of the third phalanx servo 32 is fixedly connected with the bottom side surface of the fingertip base 8 to control the flexion and extension movement of the fingertip base 8.

[0092] It can be seen that the transmission design of this dexterous hand refers to the structure and function of the human hand, and two different transmission design methods are adopted for the thumb and ordinary fingers. Since the thumb of the human hand is located on the front side of the other four fingers and has the ability of opposition, it can perform opposition movement of approaching each other or opposition movement of moving away from each other with another finger or multiple fingers. Therefore, the thumb occupies an extremely important position among all parts of the human hand.

[0093] In this embodiment, the realization of the opposition ability of the thumb unit 20 is completed by the collaborative work of the rotational freedom degree of the thumb unit 20 and the remaining flexion and extension freedom degrees. Multiple flexion and extension freedom degrees jointly realize the function of the thumb bending, while the rotational freedom degree realizes the function similar to the palm joint in the human hand by the second phalanx 2 rotating around the output shaft of the first phalanx servo 12, expanding the movement range of the thumb unit 20 and enabling the thumb unit 20 to have the ability to complete opposition movement and anti-opposition movement.

[0094] For the ordinary finger unit 10, in order to improve the structural compactness, the transmission between the finger base servo 5 and the first phalanx bracket 11 is realized through two bevel gears, so as to realize the movement transmission of the flexion and extension freedom degree within a limited space. Multiple flexion and extension freedom degrees jointly realize the function of finger bending; while the lateral swing freedom degree realizes the lateral swing movement of the finger on the horizontal plane by the second phalanx 2 rotating around the output shaft of the first phalanx servo 12, making the movement of the dexterous hand finger more flexible and increasing the redundancy of the dexterous hand freedom degree at the same time.

[0095] Through the analysis of the human hand structure and finger function, this dexterous hand designs two different finger transmission methods, enabling the dexterous hand to have the ability to complete opposition movement and anti-opposition movement.

[0096] Further referring to Figure 5 as shown, preferably, a plurality of palm base servos 41 are further installed on the palm base 4, and the plurality of palm base servos 41 correspond to the plurality of finger units one by one; each palm base servo 41 is configured with a steel wire 42, and a wire 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 around the wire 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] In addition, the steel wire 42 can pass through the preset pores on the fingertip base 8 and then be fixedly connected to the fingertip fixing bracket 9 to limit the movement range of the steel wire 42. By driving the wire winding wheel 43 to rotate forward or backward through the output shaft of the palm base servo 41, the stretching movement of the steel wire 42 can be controlled; when the steel wire 42 pulls the tendon 7, the tendon 7 is stressed and bent; when the pulling force of the steel wire 42 on the tendon 7 decreases, the tendon 7 returns under its own elastic force. In this way, reliable control of the fingertip bending degree of freedom is achieved, meeting the design requirements of the compliance and safety performance of the dexterous hand.

[0098] It can be seen that in this embodiment, for any one finger, five servos are configured: the palm base servo 41, the finger base servo 5, and three phalanx servos. That is, each finger has five degrees of freedom, so that the rigid-flexible coupled dexterous hand exhibits kinematic characteristics and configurations similar to those of the human hand, achieving the purpose of dexterous movement.

[0099] In addition, in combination with the requirements of the dexterous hand for control accuracy and control dynamic performance, the rigid-flexible coupled dexterous hand adopts a drive design with a simple structure and integrated into the dexterous hand. The servo can adopt the HTS-20L type servo. Referring to Figure 6 as shown, when the servo is structurally connected to the driven structure, taking the second phalanx servo 22 of the thumb unit 20 and the third phalanx bracket 31 as an example, a threaded hole is opened at the lower end of the third phalanx bracket 31, and the third phalanx bracket 31 is fixed to the output shaft 23 of the second phalanx servo 22 through a hexagon bolt 24, so as to transmit the rotation of the output shaft 23 to the third phalanx bracket 31. In this way, the offset angle of each phalanx on the rudder surface can be accurately controlled, and the movement transmission between the phalanxes at all levels is simply and efficiently realized to achieve the opposition ability of the dexterous hand. Except for special cases (such as the finger base servo 5 of the ordinary finger unit 10 and the first phalanx bracket 11 are driven by two bevel gears), most of the servos and the structures they drive can achieve movement transmission in a similar way.

[0100] On the other hand, the present invention provides a control method for a dexterous hand, which adopts the aforementioned control system of the dexterous hand and includes the following steps:

[0101] S1. Establish the kinematic model of the dexterous hand. For any finger unit, when modeling, the first knuckle servo 12, the second knuckle servo 22, the third knuckle servo 32 and the finger base servo 5 are jointly regarded as the four rotating joints of the finger unit.

[0102] It can be understood that although each finger unit has five degrees of freedom, in addition to the above four servos as four rotating units, it also includes the finger base servo 5 for controlling the bending of the tendon 7. However, because the work of the finger base servo 5 is relatively independent and the corresponding tendon 7 is controlled one-to-one by the steel wire 42, when the overall position of the finger unit changes due to the work of other servos, the finger base servo 5 only needs to maintain the bending angle of the tendon 7 in the required state. Therefore, only the other four servos need to be regarded as rotating joints and modeled.

[0103] The steps for establishing the kinematic model of the dexterous hand specifically include:

[0104] Refer to Figure 7 As shown, the figure corresponds to Figure 3 the ordinary finger unit 10 in i -X i Y i Z i (i = 1, 2, 3, 4). The origin O i in the coordinate system is located at the geometric center of the servo. The direction of the Z i axis is the direction of the output axis, the direction of the X i axis is the direction pointed by the finger unit in the straight state. Finally, the orientation of the Y i axis is selected according to the right-hand coordinate system rule;

[0105] Derive the D-H parameter table of each rotating joint as shown in Table 1:

[0106] Table 1 D-H parameter table of rotating joints

[0107]

[0108] Based on the chain rule, the derivation formula of the homogeneous transformation matrix of the (i + 1)-th rotating joint relative to the i-th rotating joint is as follows:

[0109]

[0110] In Equation (1), R X (α i ) describes that the rotating joint first rotates by an angle α i around the X i axis, and then through the translation transformation D X (ai ) causes the joint to translate along the X i axis by a i distance, and then through a rotation transformation R Z (θ i+1 ) rotate around the Z i+1 axis by θ i+1 angle, and finally through a translation transformation D Z (d i+1 ) translate along the Z i+1 axis by d i+1 distance, that is, the rotation transformation from the i-th rotary joint to the i + 1-th rotary joint is realized, and the general expression is obtained:

[0111]

[0112] To simplify the expression, define Combined with the derived D-H parameter table, the homogeneous transformation matrix of each rotary joint is derived as shown in the following formula:

[0113]

[0114] Among them, the matrices and are defined as shown in the following formulas (4), (5), (6), (7):

[0115]

[0116] Furthermore, in order to describe the elements in in formula (3) concisely, define the elements in formula (3) Formula (3) is rearranged as follows:

[0117]

[0118] The specific mathematical formulas of each element are as follows:

[0119]

[0120] In the above formula, define Thus, the influence of the rotary joint variables on the position and attitude of the finger unit end is described by formulas (8) and (9).

[0121] S2. For any finger unit, the host computer 500 sends an instruction for this finger unit to the control module 100 to obtain the expected position of the end of this finger unit.

[0122] S3. Based on the kinematic model established in step S1, calculate the spatial vector of the rotation joint corresponding to the finger unit through inverse kinematic mapping.

[0123] For any finger unit, referring to Equation (8), its end position vector is expressed as The desired position vector is expressed as x * =[p x * p y * p z * T , and define the spatial vector of the rotation joint as where θ i (i = 1, 2, 3, 4) represents the rotation angle of the i-th servo. The goal of inverse kinematic mapping calculation is to solve the spatial vector q of the rotation joint through the desired position vector x * . The specific derivation process is as follows:

[0124] Multiply a homogeneous transformation matrix on the left side of Equation (8) to get:

[0125]

[0126] Since the elements in the fourth column of the first row, the fourth column of the second row, and the fourth column of the third row in the left and right matrices of Equation (10) are equal, we can obtain:

[0127]

[0128] From the second equation in Equation (11), we can solve for θ1:

[0129]

[0130] After squaring the first and third equations in Equation (11), we can obtain θ3:

[0131]

[0132] where, There are two solutions for θ3 in the above equation, and the value is taken as the one closest to the current position;

[0133] Substitute θ1 and θ3 into Equation (11) to solve for θ2:

[0134]

[0135] Then multiply Equation (8) on the left side by to get:

[0136] ​

[0137] Since the elements in the first row and first column and the second row and second column of the left and right sides of Equation (15) are equal, we obtain:

[0138] θ4 = Atan2(s4, c4), (16)

[0139] where the mathematical descriptions of s4 and c4 are as follows:

[0140]

[0141] where r 11 、r 21 、r 31 are as shown in Equation (9);

[0142] Combining Equations (12), (13), (14), and (16), given the desired position vector x * of the finger tip, the spatial vector q of the rotary joint can be calculated through the inverse kinematic mapping.

[0143] S4. Then, calculate the servo drive vector corresponding to the spatial vector of the rotary joint through the inverse kinematic mapping.

[0144] Define the servo drive vector where u i (i = 1, 2, 3, 4) represents the drive voltage of the i-th servo. The goal of the inverse kinematic mapping calculation is to solve the corresponding servo drive vector u through the spatial vector q of the rotary joint. The specific derivation process is as follows:

[0145] The forward kinematic mapping from the servo drive vector to the spatial vector of the rotary joint is a linear mapping, that is:

[0146] q = Au (19)

[0147] where A is a diagonal matrix A = diag[0.24 0.24 0.24] T , then the mathematical description of the corresponding inverse kinematic mapping is as follows:

[0148] u = A -1 q (20).

[0149] S5. Control the working state of the corresponding servo according to the calculation result in step S4.

[0150] It can be seen that according to the control method of the dexterous hand provided by the present invention, given the desired position of the finger tip, the spatial vector of the rotary joint is calculated through the inverse kinematic mapping, and further the servo drive vector is calculated through the inverse kinematic mapping, so as to achieve precise control of the finger tip position.

[0151] In summary, the present invention adopts a special control system and method, and combines rigid finger joints with flexible fingertips and tendons, effectively weighing the control dynamic performance and safety performance; thereby enabling the dexterous hand to have better compliance and higher safety performance compared to dexterous hands based on rigid materials, and having higher control precision and better dynamic control performance compared to soft dexterous hands based on artificial muscles.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A control system for a dexterous hand, characterized in that, It includes a dexterous hand body, a control module (100), a power module (200), a camera (300), a sensor module (400) and a host computer (500); The dexterous hand body includes a palm base (4) and multiple finger units. Each finger unit includes a finger base, a fingertip module and multiple phalanges. The finger base is fixedly installed on the palm base (4). Moreover, each finger unit includes multiple servos to control its own movement; The fingertip module includes a fingertip (6), a tendon (7), a fingertip base (8) and a fingertip fixing bracket (9). The tendon (7) and the fingertip (6) are made of a flexible elastic material. The fingertip (6) is installed on the fingertip fixing bracket (9). The tendon (7) is used to connect the fingertip fixing bracket (9) and the fingertip base (8); The power module (200) is used to supply power to the whole system; The camera (300) is arranged on the palm base (4) and is used to collect visual image information; The control module (100) is connected to each sensor in the camera (300) and the sensor module (400) and each servo through signal lines respectively, and is connected to the host computer (500); The control module (100) is used to receive the information collected by the camera (300) and the sensor module (400), send the current movement states of each servo to the host computer (500), and at the same time receive the control instructions sent by the host computer (500) to realize the closed-loop control of the dexterous hand body.

2. The control system of the dexterous hand according to claim 1, characterized in that, For any finger unit, each of its phalanges includes a phalanx bracket and a phalanx servo fixedly installed on the phalanx bracket. Moreover, a finger base servo (5) is also fixedly installed 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 other phalanx servos are used to control the movement of the next phalanx.

3. The control system of the dexterous hand according to claim 2, characterized in that, For any finger unit, the multiple phalanges include a first phalanx (1), a second phalanx (2) and a third phalanx (3). The first phalanx (1) includes a first phalanx servo (12) and a first phalanx bracket (11). The second phalanx (2) includes a second phalanx servo (22) and a second phalanx bracket (21). The third phalanx (3) includes a third phalanx servo (32) and a third phalanx bracket (31).

4. The control system of the dexterous hand according to claim 3, characterized in that, The number of the finger units is five, including one thumb unit (20) and four ordinary finger units (10) with the same structure; For the thumb unit (20), 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 rotation 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); For any ordinary finger unit (10), 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 swing 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).

5. The control system of the dexterous hand according to claim 1, characterized in that A plurality of palm base servos (41) are further installed on the palm base (4), and the plurality of palm base servos (41) correspond to the plurality of finger units one by one; Each palm base servo (41) is provided with a steel wire (42), and a wire 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 around the wire winding wheel (43), and the other end is fixedly connected to the side of the fingertip fixing frame (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).

6. The control system of the dexterous hand according to claim 1, characterized in that, It further includes an I / O module (600) and a remote controller (700), and the I / O module (600) is used to send the control instructions of the remote controller (700) to the control module (100) to realize the human-computer interaction function of the dexterous hand.

7. A control method for a dexterous hand, characterized in that Adopt the control system of the dexterous hand described in any one of claims 3-6, and include the following steps: S1. Establish a kinematic model of the dexterous hand. When modeling any finger unit, the first phalanx servo (12), the second phalanx servo (22), the third phalanx servo (32) and the finger base servo (5) are jointly used as the four rotating joints of the finger unit; S2. For any finger unit, the host computer (500) sends an instruction for the finger unit to the control module (100) to obtain the desired position of the end of the finger unit; S3. Based on the kinematic model established in step S1, calculate the spatial vector of the corresponding rotating joint of the finger unit through inverse kinematic mapping; S4. Then calculate the servo drive vector corresponding to the spatial vector of the rotating joint through inverse kinematic mapping; S5. Control the working state of the corresponding servo according to the calculation result in step S4.

8. The control method of the dexterous hand according to claim 7, wherein In step S1, the steps of establishing the kinematic model of the dexterous hand specifically include: Establish coordinate systems for each rotating joint respectively, denoted as O i -X i Y i Z i (i = 1, 2, 3, 4), the origin O in the coordinate system i is located at the geometric center of the servo, and the Z i axis is oriented in the direction of the output axis, and the X i axis is oriented in the direction pointed to when the finger unit is in the straight state. Finally, the orientation of the Y i axis is selected according to the right-hand coordinate system rule; Derive the D-H parameter table of each rotating joint. Based on the chain rule, the formula for deriving the homogeneous transformation matrix of the (i + 1)-th rotating joint relative to the i-th rotating joint is as follows: In formula (1), R X (α i ) describes the revolute joint first around X i Axis rotation α i Angle, then transform D by translation X (a i ) so that the joint is along the X i Axis translation a i distance, and then transformed by rotation R Z (θ i+1 ) around Z i+1 Axis rotation θ i+1 Angle, and finally transform D by translation Z (d i+1 ) Along Z i+1 Axis translation d i+1 Distance, that is, to achieve the rotation transformation from the i-th rotation joint to the i+1-th rotation joint, and get The general expression of is: To simplify the expressions, define Combined with the derived D-H parameter table, the homogeneous transformation matrices of each rotating joint are derived As shown in the following formula: Among them, the matrix and are defined as shown in the following formulas (4), (5), (6), and (7): Further, for the sake of a concise description of the elements in Equation (3), define the elements in Equation (3) as follows: Rearrange Equation (3) as follows: The specific mathematical formulas of each element are as follows: In the above formula, it is defined that Thus, the influence of the rotational joint variables on the position and attitude of the end of the finger unit is described by equations (8) and (9).

9. The control method of the dexterous hand according to claim 8, characterized in that, In step S3, for any finger unit, referring to Equation (8), its end position vector is expressed as The desired position vector is expressed as x * =[p x * p y * p z * T , and the spatial vector of the rotary joint is defined as where θ i (i = 1, 2, 3, 4) represents the rotation angle of the i-th servo. The goal of the inverse kinematics mapping calculation is to solve the spatial vector q of the rotary joint through the desired position vector x * . The specific derivation process is as follows:​ Multiply a homogeneous transformation matrix on the left side of Equation (8). We get: It is known that the first row and fourth column, the second row and fourth column, and the third row and fourth column in the left and right matrices of formula (10) are equal, and it can be obtained that: From the second equation in formula (11), θ1 can be solved: After squaring the first and third equations in formula (11), θ3 can be obtained: Among them, In the above formula, θ3 has two solutions, and the value is taken as the standard of the value closest to the current position; Substitute θ1 and θ3 into formula (11) to solve for θ2: Multiply equation (8) on the left by to obtain: It is known that the first row and first column and the second row and second column in the left and right sides of formula (15) are equal, and it is obtained that: θ4 = Atan2(s4, c4), (16) The mathematical descriptions of s4 and c4 are as follows: where r 11 、r 21 、r 31 as shown in Equation (9); Combining equations (12), (13), (14), and (16), given the desired position vector x * the spatial vector q of the revolute joints can be calculated by the inverse kinematic mapping.

10. The control method of the dexterous hand according to claim 9, characterized in that In step S4, a servo drive vector is defined where u i (i = 1, 2, 3, 4) represents the drive voltage of the i-th servo. The goal of the inverse kinematics mapping calculation is to solve the corresponding servo drive vector u through the spatial vector q of the rotating joint. The specific derivation process is as follows: The forward kinematic mapping from the servo drive vector to the rotational joint space vector is a linear mapping, i.e.: q = Au (19) Among them, the diagonal matrix A = diag[0.24 0.24 0.24] T , then the mathematical description of the corresponding inverse kinematic mapping is as follows: u = A -1 q(20).

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