A mechanical wrist joint based on flexible tether control

Abstract

The present invention discloses a mechanical wrist joint based on flexible tether control. The wrist joint of the manipulator is connected to a multi-degree-of-freedom piezoelectric ball motor module, which is connected to a ball motor drive module, which is connected to a tether retractable module through a signal conversion module; the joint drive signal of the tether retractable module is sent to the ball motor drive module through the signal conversion module, and the ball motor drive module drives the multi-degree-of-freedom piezoelectric ball motor module according to the received signal, and the multi-degree-of-freedom piezoelectric ball motor module then drives the manipulator, and the ball motor drive module detects the position signal of the multi-degree-of-freedom piezoelectric ball motor module and feeds it back to the signal conversion module, and the signal conversion module adjusts the tether retractable module according to the feedback signal, thereby realizing the control of the mechanical wrist joint. The present invention realizes the precise control of the wrist joint position, speed and acceleration, and has the advantages of compact structure, excellent control performance, and easy engineering implementation.

Description

Technical Field

[0001] The invention relates to a mechanical wrist joint, in particular to a mechanical wrist joint based on flexible tether control. Background Art

[0002] Currently, there are very few cost-effective prostheses available on the market for people with limb disabilities, and most of them are decorative. In addition, most current prostheses use a single-degree-of-freedom motor combined with a mechanical mechanism to achieve multi-degree-of-freedom rotation of the wrist. The large number of mechanical transmission mechanisms makes the overall size of the wrist larger, heavier, and inconvenient to move, which limits the use and promotion of prostheses. Although mechanical wrist-band prosthetic technology has developed in the direction of multi-degree-of-freedom and high-precision since the 1970s, overall, there are currently few mature commercial wrist-band prosthetic hands. From the perspective of design focus, most research and design on prostheses tend to be decorative, with less consideration of functionality. Summary of the invention

[0003] The present invention takes a mechanical wrist joint as the background, and aims to provide a mechanical wrist joint based on flexible tether control in order to solve the shortcomings of traditional mechanical wrist joints, such as large size, heavy weight and inconvenient movement. The mechanical wrist joint uses a piezoelectric ball motor with multiple degrees of freedom. At the same time, multiple flexible tethers are used to simulate human tendons to send motion instructions, collect tether tension signals, and convert them into motor drive signals through a signal converter to achieve precise control of the motor, so that the position, velocity and acceleration of the mechanical wrist joint can be precisely controlled, and finally a good flexible control effect of the mechanical wrist joint is obtained.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] The present invention comprises a manipulator, a tether retracting and releasing module, a signal conversion module, a ball motor driving module and a multi-degree-of-freedom piezoelectric ball motor module;

[0006] The wrist joint of the manipulator is connected to a multi-degree-of-freedom piezoelectric ball motor module, which is connected to a ball motor drive module, which is connected to a tether retraction and extension module via a signal conversion module; the joint driving signal of the tether retraction and extension module is converted by the signal conversion module and then sent to the ball motor drive module, the ball motor drive module drives the multi-degree-of-freedom piezoelectric ball motor module according to the received signal, and the multi-degree-of-freedom piezoelectric ball motor module then drives the wrist joint of the manipulator, the ball motor drive module detects the position signal of the multi-degree-of-freedom piezoelectric ball motor module and feeds it back to the signal conversion module, the signal conversion module adjusts the tether retraction and extension module according to the feedback signal, thereby realizing the control of the wrist joint of the manipulator.

[0007] The multi-degree-of-freedom piezoelectric ball motor module comprises a limiting ring, a stator bracket, a preloaded leaf spring, a traveling wave stator, a ceramic ball, a lower connecting rod and a bent bar;

[0008] The lower end face of the lower connecting rod is fixedly connected to the ball motor driving module, and the upper end face of the lower connecting rod is fixedly installed with a plurality of stator brackets arranged at equal intervals along the circumference, and the side of each stator bracket close to the center of the circle is fixedly connected to the traveling wave stator, and a preloaded leaf spring is also arranged between each stator bracket and the traveling wave stator, and ceramic balls are embedded in the gaps between the plurality of traveling wave stators, and the plurality of traveling wave stators are tangent to the outer circumferential surface of the ceramic balls. A protrusion is arranged on the top of the ceramic balls, and the protrusion serves as the motor output shaft and is coaxially connected to the wrist joint of the manipulator. The upper end face of the lower connecting rod is also fixedly connected to one end of a plurality of bent bars, and each bent bar is arranged between two adjacent stator brackets. The other end of each bent bar is extended upward and fixedly connected to a limiting ring, and the limiting ring is mounted on the top of the ceramic ball to limit the axial movement of the ceramic ball, and the ball motor driving module is electrically connected to the control end of the traveling wave stator.

[0009] The ceramic ball is located between the limiting ring and the lower connecting rod and the ceramic ball is provided with a preset moving distance in the axial direction. The maximum diameter of the ceramic ball is greater than the diameter of the limiting ring.

[0010] The ball motor drive module includes a connecting shaft and a motor driver;

[0011] The two ends of the connecting shaft are fixedly connected to the signal conversion module and the ball motor driving module respectively. A motor driver is fixedly installed in the connecting shaft, and the motor driver is electrically connected to the signal conversion module and the ball motor driving module respectively.

[0012] The signal conversion module includes a signal converter, both ends of which are fixedly connected to the tether retraction module and the ball motor drive module respectively, the output end of the signal converter is also electrically connected to the motor drive module, and the input end of the signal converter is also electrically connected to the tether retraction module.

[0013] The tether retracting and releasing module comprises a fixed truss, a tether, a tensioning wheel, a hub motor, a base and a motor bracket;

[0014] The two ends of the fixed truss are fixedly connected to the signal conversion module and the base respectively. A plurality of motor brackets are fixedly installed on the base at intervals, each of which is equipped with a hub motor. A tensioning wheel is also fixedly installed on each motor bracket through a connecting rod. A pressure sensor is provided on the tensioning wheel for measuring the tether pressure. The pressure sensor on the tensioning wheel and the hub motor are electrically connected to the signal conversion module. A plurality of tethers are provided between the signal conversion module and the base. One end of each tether is fixedly installed on the signal conversion module, and the other end of each tether is fixed on the corresponding hub motor after passing around the tensioning wheel. Each tether is wound around the corresponding hub motor, and the rotation of the hub motor realizes the retraction and extension of the tether.

[0015] The beneficial effects of the present invention are:

[0016] 1. Compared with the traditional mechanical wrist joint, the present invention uses a high-reliability multi-degree-of-freedom ball-jointed piezoelectric ball motor, so the mechanical wrist joint is light in weight, small in size and easy to install.

[0017] 2. Compared with the traditional mechanical wrist joint, the rear end of the present invention adopts a tether to simulate the human tendon signal, with a high degree of coupling, which can achieve good flexible control of the mechanical wrist joint.

[0018] 3. Compared with the traditional traveling wave piezoelectric ball motor, the present invention proposes a new structure of a ball-jointed flexible piezoelectric ball motor, which solves the problems of poor compression / tension resistance and difficulty in precise control of the ball rotor in previous motors.

[0019] 4. The present invention has an ingenious structural design, is easy to manufacture, and is easy to implement in engineering.

[0020] 5. The center of mass of the multi-degree-of-freedom piezoelectric ball motor of the present invention is stable, the rotor is evenly stressed, and the drive is relatively easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is one of the three-dimensional diagrams of the mechanical wrist joint of the present invention;

[0022] Figure 2 This is the second three-dimensional diagram of the mechanical wrist joint of the present invention;

[0023] Figure 3 It is a schematic diagram of a multi-degree-of-freedom piezoelectric ball motor module of the present invention;

[0024] Figure 4 is a schematic diagram of a motor drive module of the present invention;

[0025] Figure 5 is a schematic diagram of a tether retracting and releasing module of the present invention;

[0026] In the figure: 1. limiting ring, 2. stator bracket, 3. preloaded leaf spring, 4. traveling wave stator, 5. ceramic ball, 6. motor output shaft, 7. lower connecting rod, 8. bent bar, 9. manipulator, 10. connecting shaft, 11. motor driver, 12. signal converter, 13. fixed truss, 14. tether sleeve, 15. hub motor housing, 16. tether, 17. tensioning wheel, 18. hub motor, 19. base, 20. motor bracket, 21. tether retraction module housing. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific implementations.

[0028] like Figure 1 and Figure 2 As shown, the present invention includes a manipulator 9, a tether retracting and releasing module, a signal conversion module, a ball motor driving module and a multi-degree-of-freedom piezoelectric ball motor module;

[0029] The wrist joint of the manipulator 9 is connected to a multi-degree-of-freedom piezoelectric ball motor module, which is connected to a ball motor drive module, which is connected to a tether retraction and extension module via a signal conversion module; the joint driving signal of the tether retraction and extension module is converted by the signal conversion module and then sent to the ball motor drive module, the ball motor drive module drives the multi-degree-of-freedom piezoelectric ball motor module according to the received signal, and the multi-degree-of-freedom piezoelectric ball motor module then drives the wrist joint of the manipulator 9, the ball motor drive module detects the position signal of the multi-degree-of-freedom piezoelectric ball motor module and feeds it back to the signal conversion module, the signal conversion module adjusts the tether retraction and extension module according to the feedback signal, thereby realizing the control of the wrist joint of the manipulator 9.

[0030] like Figure 3 As shown, the multi-degree-of-freedom piezoelectric ball motor module includes a limiting ring 1, a stator bracket 2, a preloaded leaf spring 3, a traveling wave stator 4, a ceramic ball 5, a lower connecting rod 7 and a bent bar 8;

[0031] The lower end surface of the lower connecting rod 7 is fixedly connected to the ball motor drive module, and the upper end surface of the lower connecting rod 7 is fixedly installed with multiple stator brackets 2 arranged at equal intervals along the circumference. In a specific implementation, there are three stator brackets 2, that is, the angle between two adjacent stator brackets 2 is 120°. The side surface of each stator bracket 2 close to the center of the circle is fixedly connected to the traveling wave stator 4, and a pre-tightening leaf spring 3 is also arranged between each stator bracket 2 and the traveling wave stator 4. The pre-tightening leaf spring 3 is used to provide a spring pre-tightening force so that the traveling wave stator is in close contact with the ceramic ball rotor. Ceramic balls 5 are embedded in the gaps between multiple traveling wave stators 4. Multiple traveling wave stators 4 are tangent to the outer circumferential surface of the ceramic balls 5. A protrusion is arranged on the top of the ceramic balls 5. The protrusion serves as a motor output shaft 6 and is coaxially connected to the wrist joint of the manipulator 9. The upper end surface of the lower connecting rod 7 is also fixedly connected to one end of multiple bent bars 8. Each bent bar 8 is arranged between two adjacent stator brackets 2. The other end of each bent bar 8 is extended upward and fixedly connected to the limiting ring 1. The limiting ring 1 is mounted on the top of the ceramic ball 5 to limit the axial movement of the ceramic ball 5. The motor driver 11 of the ball motor driving module is electrically connected to the control end of the traveling wave stator 4. The ball motor driving module drives the ceramic ball 5 through the traveling wave stator 4 to rotate the motor output shaft 6. Specific motor driving principle: when the motor works normally, the traveling wave stator 4 is in full contact with the ceramic ball 5 through the spring preload force provided by the preload leaf spring 3. When the traveling wave stator is energized, it generates high-frequency vibration. The three traveling wave stators cooperate with each other to generate driving torque, and the ceramic ball rotates under the action of the torque.

[0032] The ceramic ball 5 is located between the limiting ring 1 and the lower connecting rod 7 and has a preset moving distance in the axial direction, that is, the ceramic ball 5 can move a certain distance along the direction of the motor output shaft; the maximum diameter of the ceramic ball 5 is greater than the diameter of the limiting ring 1.

[0033] like Figure 4 As shown, the ball motor drive module includes a connecting shaft 10 and a motor driver 11;

[0034] The two ends of the connecting shaft 10 are fixedly connected to the signal conversion module and the ball motor driving module respectively. A motor driver 11 is fixedly installed in the connecting shaft 10. The output end and input end of the motor driver 11 are electrically connected to the traveling wave stator 4 control end of the signal conversion module and the output end of the signal converter 12 of the ball motor driving module respectively.

[0035] The signal conversion module includes a signal converter 12, the two ends of which are fixedly connected to the tether 16, sleeve 14 and connecting shaft 10 of the spherical motor drive module, respectively. The output end of the signal converter 12 is also electrically connected to the input end of the motor driver 11 of the motor drive module, and the input end of the signal converter 12 is also electrically connected to the tether 16, tensioning wheel 17 and hub motor 18 of the tether retractable module. The input end and output end of the signal converter are respectively provided with four input ports and four output ports, which can convert the signals from the four pressure sensors into the electrical signal output of the motor driver in the spherical motor drive module. The motor driver can transmit the output signal of the signal converter to the multi-degree-of-freedom piezoelectric spherical motor after comprehensive processing.

[0036] like Figure 5 As shown, the tether retracting and releasing module includes a fixed truss 13, a tether 16, a sleeve 14, a tensioning wheel 17, a hub motor 18, a hub motor housing 15, a tether retracting and releasing module housing 21, a base 19 and a motor bracket 20;

[0037] The fixed truss 13, the tether 16, the sleeve 14, the tensioning wheel 17, the hub motor 18, the hub motor housing 15, the tether retracting module housing 21, the base 19 and the motor bracket 20 are all arranged in the tether retracting module housing 21; the two ends of the fixed truss 13 are fixedly connected to the input end of the signal conversion module and the base 19 respectively, the base is divided into two semicircles, which are connected by pins, and each semicircle is fixedly connected to at least one fixed truss 13, and a plurality of motor brackets 20 are fixedly installed on the base 19 at intervals, and each motor bracket 20 has a plurality of motor brackets 20. A hub motor 18 is installed, and a hub motor housing 15 is installed outside each hub motor 18. A tensioning wheel 17 is fixedly installed on each motor bracket 20 through a connecting rod. A pressure sensor is provided on the tensioning wheel 17 for measuring the pressure of the tether 16. The pressure sensor on the tensioning wheel 17 and the hub motor 18 are electrically connected to the signal conversion module. A plurality of tethers 16 are provided between the signal conversion module and the base 19. The number of tethers 16 and hub motors 18 is the same. In a specific implementation, there are 4 tethers 16 and 4 hub motors 18. One end of each tether 16 is fixedly installed on the input end of the signal conversion module, and a sleeve 14 is arranged outside one end of each tether 16. One end of the sleeve 14 is fixedly installed on the input end of the signal conversion module, and a gap is arranged between the sleeve 14 and the tether 16; the other end of each tether 16 is fixed on the corresponding hub motor 18 after passing through the tensioning wheel 17, and each tether 16 is wound on the corresponding hub motor 18. The rotation of the hub motor 18 realizes the retraction and extension of the tether 16. The retraction and extension process of the tether 16 is similar to the contraction and relaxation process of the tendon of the human body. The pressure sensor installed on the tensioning wheel 17 has a signal output, and the signal converter 12 receives and converts the collected pressure signal into an input electrical signal output of the motor driver 11. The motor driver 11 processes the electrical signal received from the signal converter 12, controls the rotation of the multi-degree-of-freedom piezoelectric ball motor, and realizes the multi-posture of the motor output shaft 6 of the ball-hinged piezoelectric ball motor.

[0038] In a specific implementation, the tension of each tether 16 is used as a joint driving signal of the tether retraction and extension module. The tension of each tether 16 is obtained by calculating the measured pressure applied by the tether 16 on the corresponding pressure sensor and the angle between the tensioning wheel 17 and the motor bracket 20, wherein the angle between the tensioning wheel 17 and the motor bracket 20 is specifically the angle between the connecting rod of the motor bracket 20 and the central axis of the motor bracket 20.

[0039] The working process of the present invention is as follows:

[0040] First, the tether in the tether module is wound around the hub motor in the tether retraction and release module through the tensioning wheel in the tensioning measurement module. The tether is always kept in a tensioned state. The pressure sensor on the tensioning wheel measures the pressure and outputs a signal. The four hub motors can rotate independently and are not affected. The contraction and relaxation of the tether are achieved through the rotation of the hub motor, simulating the contraction and relaxation process of human tendons. At the same time, the four hub motors move independently of each other and are not affected. The pressure sensor installed on the tensioning wheel measures different pressure values ​​from the tether, and the obtained pressure signal is input into the signal converter. The pressure sensor and the hub motor form a closed-loop control. The value of the pressure sensor can be fed back to the hub motor, and the tension of the tether is changed by the rotation of the hub motor.

[0041] Then, the signal converter receives the signals from the four pressure sensors, and processes and converts the signals of the pressure sensors into electrical signals of the motor driver and outputs them to the motor driver. After receiving the electrical signals from the signal converter, the motor driver drives the multi-degree-of-freedom piezoelectric ball motor to rotate. The motor output shaft of the multi-degree-of-freedom spherical-jointed piezoelectric ball motor can output multiple different postures. The posture specifically refers to the circumferential rotation and axial displacement of the multi-degree-of-freedom spherical-jointed piezoelectric ball motor, thereby achieving the purpose of flexibly driving the mechanical wrist joint. At the same time, the electrical signal of the multi-degree-of-freedom piezoelectric ball motor can be fed back to the motor driver through a closed-loop circuit. The motor driver can transmit the signal back to the signal converter. The signal converter can convert the signal fed back by the motor driver into the signal output of the pressure sensor, and the contraction and relaxation of the tether can be achieved through the closed-loop control of the pressure sensor and the hub motor.

[0042] Finally, by repeating the above steps, the flexible control of the mechanical wrist joint can be realized, achieving the requirements of high-precision posture control, reliable performance, dexterity, and lightweight.

Claims

1. A mechanical wrist joint based on flexible tether control, characterized in that: It includes a manipulator (9), a tether retracting and releasing module, a signal conversion module, a ball motor driving module and a multi-degree-of-freedom piezoelectric ball motor module; The wrist joint of the manipulator (9) is connected to a multi-degree-of-freedom piezoelectric ball motor module, which is connected to a ball motor drive module, which is connected to a tether retraction and extension module via a signal conversion module; the joint drive signal of the tether retraction and extension module is converted by the signal conversion module and then sent to the ball motor drive module, the ball motor drive module drives the multi-degree-of-freedom piezoelectric ball motor module according to the received signal, and the multi-degree-of-freedom piezoelectric ball motor module then drives the wrist joint of the manipulator (9), the ball motor drive module detects the position signal of the multi-degree-of-freedom piezoelectric ball motor module and feeds it back to the signal conversion module, the signal conversion module adjusts the tether retraction and extension module according to the feedback signal, thereby realizing the control of the wrist joint; The ball motor drive module comprises a connecting shaft (10) and a motor driver (11); The two ends of the connecting shaft (10) are respectively fixedly connected to the signal conversion module and the ball motor driving module, and a motor driver (11) is fixedly installed in the connecting shaft (10), and the motor driver (11) is respectively electrically connected to the signal conversion module and the ball motor driving module; The signal conversion module comprises a signal converter (12), the two ends of the signal converter (12) are respectively fixedly connected to the tether retracting and releasing module and the ball motor driving module, the output end of the signal converter (12) is also electrically connected to the motor driving module, and the input end of the signal converter (12) is also electrically connected to the tether retracting and releasing module; The tether retracting and releasing module comprises a fixed truss (13), a tether (16), a tensioning wheel (17), a hub motor (18), a base (19) and a motor bracket (20); The two ends of the fixed truss (13) are respectively fixedly connected to the signal conversion module and the base (19); a plurality of motor brackets (20) are fixedly installed on the base (19) at intervals; a wheel hub motor (18) is installed on each motor bracket (20); a tensioning wheel (17) is also fixedly installed on each motor bracket (20) via a connecting rod; a pressure sensor is arranged on the tensioning wheel (17) for measuring the pressure of the tether (16); the pressure sensor on the tensioning wheel (17) and the wheel hub motor (18) are both electrically connected to the signal conversion module; a plurality of tethers (16) are arranged between the signal conversion module and the base (19); one end of each tether (16) is fixedly installed on the signal conversion module; the other end of each tether (16) is fixed on the corresponding wheel hub motor (18) after passing through the tensioning wheel (17); each tether (16) is wound on the corresponding wheel hub motor (18); the rotation of the wheel hub motor (18) realizes the retraction and extension of the tether (16).

2. A mechanical wrist joint based on flexible tether control according to claim 1, characterized in that: The multi-degree-of-freedom piezoelectric ball motor module comprises a limiting ring (1), a stator bracket (2), a preloaded leaf spring (3), a traveling wave stator (4), a ceramic ball (5), a lower connecting rod (7) and a bent bar (8); The lower end surface of the lower connecting rod (7) is fixedly connected to the ball motor drive module, and the upper end surface of the lower connecting rod (7) is fixedly mounted with a plurality of stator brackets (2) arranged at equal intervals along the circumference, and the side surface of each stator bracket (2) close to the center of the circle is fixedly connected to the traveling wave stator (4), and a preloaded leaf spring (3) is further arranged between each stator bracket (2) and the traveling wave stator (4). Ceramic balls (5) are embedded in the gaps between the plurality of traveling wave stators (4), and the plurality of traveling wave stators (4) are tangent to the outer circumferential surface of the ceramic balls (5). The top of the ceramic balls (5) A protrusion is provided at the top, the protrusion serves as a motor output shaft (6) and is coaxially connected to the wrist joint of the manipulator (9). The upper end surface of the lower connecting rod (7) is also fixedly connected to one end of a plurality of bent bars (8), each bent bar (8) is arranged between two adjacent stator brackets (2), and the other end of each bent bar (8) is extended upward and fixedly connected to a limiting ring (1). The limiting ring (1) is sleeved on the top of the ceramic ball (5) and is used to limit the axial movement of the ceramic ball (5). The ball motor drive module is electrically connected to the control end of the traveling wave stator (4).

3. A mechanical wrist joint based on flexible tether control according to claim 2, characterized in that: The ceramic ball (5) is located between the limiting ring (1) and the lower connecting rod (7), and the ceramic ball (5) is provided with a preset moving distance in the axial direction, and the maximum diameter of the ceramic ball (5) is greater than the diameter of the limiting ring (1).

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