Multi-degree-of-freedom underactuated dexterous hand and control method thereof

Abstract

The present application relates to a multi-degree-of-freedom underactuated dexterous hand thumb and a control method thereof, and relates to the field of robot dexterous hands. The technical scheme couples and transmits the active bending movement of the second knuckle to the first knuckle through an underactuated linkage mechanism, realizes the coordinated flexion and extension of the double knuckles by a single electric cylinder, reduces one driving source on the premise of retaining the three-degree-of-freedom movement ability, effectively reduces the mass and rotational inertia of the distal end of the thumb, integrates the side swing electric cylinder to the third knuckle, and transmits force symmetrically through the double-sided turntable connector, thereby eliminating the eccentric load vibration and improving the side swing stability. The rotary dexterous hand electric cylinder is directly driven to the turntable base through a shaft coupling, cooperates with the supporting bearing to constrain the radial runout, makes the whole thumb independently rotate around the axis of the thumb, expands the adjustment dimension of the grasping posture, and is convenient for the multi-fingered palm envelope. The fingertip integrates the tactile sensor to directly obtain the contact force feedback, and supports the closed-loop adjustment of the grasping force.

Description

Technical Field

[0001] This invention relates to the field of robotic dexterous hand technology, and in particular to a multi-degree-of-freedom underactuated dexterous hand thumb and its control method. Background Technology

[0002] As the core end effector for achieving fine manipulation and human-computer interaction, the dexterous hand of a humanoid robot directly determines the overall hand's performance through the flexibility, grasping stability, and structural compactness of its thumb. Currently, thumb structures with combined degrees of freedom in bending and lateral swing have become the mainstream technological approach. These typically employ a scheme where multiple motors independently drive each finger joint to simulate the core movement patterns of the human thumb, such as opposition, flexion, extension, abduction, and adduction. This approach is widely used in service robots, industrial assembly, and rehabilitation assistive devices.

[0003] However, existing fully driven thumb structures generally suffer from the following shortcomings: Firstly, the independent drive source for each phalanx results in a large internal space occupation, high overall mass and rotational inertia, limiting the dynamic response speed and dexterity of end-effector operations. Secondly, the increased number of drive sources complicates control channels and makes wiring difficult, and the coordinated control of multiple electric cylinders requires significant computing resources, increasing system cost and failure rate. Furthermore, existing thumb modules often rely on external adapter mechanisms for rotational freedom, leading to an increased axial dimension at the thumb root and poor integration with the hand body, making it difficult to meet the design requirements of compact, dexterous hands for modularity, lightweight design, and high integration. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-degree-of-freedom underactuated dexterous hand thumb and its control method to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a thumb of a multi-degree-of-freedom underactuated dexterous hand, comprising: The third joint of the thumb integrates the second joint's dexterity cylinder and the third joint's dexterity cylinder. The second joint of the thumb is connected to the third joint of the thumb via the motor shaft A of the second joint dexterous electric cylinder, which drives the second joint of the thumb to rotate around the motor shaft A; The first joint of the thumb is hinged to the second joint of the thumb via a pin, and the first joint of the thumb rotates around the pin; A connecting rod, one end of which is hinged to the first phalanx of the thumb and the other end of which is hinged to the third phalanx of the thumb, is used to drive the first phalanx of the thumb to bend around the pin when the second phalanx of the thumb rotates; A return spring is installed inside the second joint of the thumb. One end of the return spring is connected to the second joint of the thumb, and the other end is connected to the first joint of the thumb. It is used to drive the first joint of the thumb to return to its original position. The third knuckle dexterous electric cylinder has a first turntable connector and a second turntable connector connected to both sides of the motor shaft B. The first turntable connector and the second turntable connector are mounted on the turntable base. The third knuckle dexterous electric cylinder drives the third knuckle of the thumb to swing sideways around the motor shaft B. The turntable base is fixedly connected to a coupling, and the coupling is connected to the motor shaft of the rotary dexterous electric cylinder. The rotary dexterous electric cylinder drives the turntable base to rotate around the motor shaft axis of the rotary dexterous electric cylinder.

[0006] In some embodiments, the thumb of the multi-degree-of-freedom underactuated dexterous hand further includes: The turntable is fixed in a base with an interference fit bearing inside. The turntable base passes through the bearing and is fixed to the coupling by screws. The turntable base rotates relative to the base via the bearing.

[0007] In some embodiments, the coupling is fixed to the motor shaft of the rotary dexterous cylinder by a flat-set screw, and the coupling is located below the turntable mounting base.

[0008] In some embodiments, the bottom end of the turntable fixing base is provided with a threaded hole for docking with the dexterous hand body.

[0009] In some embodiments, the fingertip of the first phalanx of the thumb is integrated with a tactile sensor.

[0010] In some embodiments, the connecting rod spans one side of the pin, such that when the second phalanx of the thumb rotates about the motor shaft A, the connecting rod applies a bending moment about the pin to the first phalanx of the thumb.

[0011] Secondly, the present invention provides a control method for the thumb of a multi-degree-of-freedom underactuated dexterous hand, applied to the aforementioned multi-degree-of-freedom underactuated dexterous hand thumb, the method comprising: The second knuckle of the thumb is controlled by a dexterous electric cylinder to drive the second knuckle of the thumb to rotate around the motor shaft A. When the second knuckle of the thumb rotates, it drives the first knuckle of the thumb to bend around the pin shaft through the connecting rod. The second knuckle dexterous electric cylinder is controlled to stop outputting or rotate in the opposite direction, and the reset spring releases elastic potential energy to drive the first knuckle of the thumb to reset around the pin. The third phalanx of the thumb is controlled by a dexterous electric cylinder to drive the third phalanx of the thumb to swing around the motor shaft B. The rotary smart hand cylinder is controlled to drive the turntable base to rotate around the motor shaft axis of the rotary smart hand cylinder through the coupling, so as to drive the thumb to rotate as a whole.

[0012] In some embodiments, the link converts the rotational motion of the second phalanx of the thumb into the flexion motion of the first phalanx of the thumb, and the flexion angle of the first phalanx of the thumb is determined by the rotational angle of the second phalanx of the thumb through the kinematic mapping relationship of the link.

[0013] In some embodiments, the motor shaft B of the third knuckle dexterous electric cylinder drives the third knuckle of the thumb, together with the first and second knuckles of the thumb, to sway sideways as a whole.

[0014] In some embodiments, the rotary dexterous electric cylinder drives the turntable base to rotate via the coupling, and the turntable base rotates relative to the turntable fixed base via a support bearing, thereby causing the thumb as a whole to rotate around the motor shaft axis of the rotary dexterous electric cylinder.

[0015] The beneficial effects of the technical solution provided by this invention include at least the following: This technical solution uses an underactuated linkage mechanism to couple and transmit the active flexion motion of the second phalanx to the first phalanx, achieving coordinated flexion and extension of both phalanges with a single electric cylinder. While retaining three degrees of freedom of motion, it reduces one drive source, effectively lowering the distal mass and rotational inertia of the thumb. The third phalanx integrates a side-swing electric cylinder, which transmits force symmetrically via a double-sided turntable connector, eliminating off-center vibration and improving lateral stability. A rotary dexterous electric cylinder directly drives the turntable base via a coupling, and with the support bearing constraining radial runout, the thumb rotates independently around its own axis, expanding the dimensions of grasping posture adjustment and facilitating multi-finger palmar envelopment. A tactile sensor integrated into the fingertip directly acquires contact force feedback, supporting closed-loop adjustment of the grasping force. All drive sources are concentrated in the proximal phalanges, with only transmission and sensing components remaining at the distal end, significantly reducing the axial and radial dimensions of the thumb, improving integration and adaptability with the hand body, and enhancing end-effector dynamic response performance. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0017] Figure 1 A schematic diagram of the structure of a multi-degree-of-freedom underactuated dexterous hand thumb provided by an exemplary embodiment of the present invention is shown.

[0018] Figure 2 It shows Figure 1 A sectional view along line AA.

[0019] Figure 3 A flowchart is shown of a control method for the thumb of a multi-degree-of-freedom underactuated dexterous hand provided by an exemplary embodiment of the present invention.

[0020] In the diagram: 1. First knuckle of the thumb; 2. Tactile sensor; 3. Second knuckle of the thumb; 4. Return spring; 5. Connecting rod; 6. Second knuckle dexterous cylinder; 61. Motor shaft A; 7. Third knuckle of the thumb; 8. Third knuckle dexterous cylinder; 81. Motor shaft B; 9. First turntable connector; 10. Second turntable connector; 11. Turntable base; 12. Rotating dexterous cylinder; 13. Support bearing; 14. Coupling; 15. Turntable fixing base; 16. Pin. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a multi-degree-of-freedom underactuated dexterous hand thumb, including a first phalanx 1, a second phalanx 3, a third phalanx 7, a second phalanx dexterous cylinder 6, a third phalanx dexterous cylinder 8, a connecting rod 5, and a return spring 4.

[0025] The third joint 7 of the thumb is the base joint of the thumb, and it integrates the second joint dexterity cylinder 6 and the third joint dexterity cylinder 8. By integrating the two cylinders inside the third joint 7, the drive source is concentrated at the proximal end, and the distal joint does not need to accommodate the motor. This reduces the size and mass of the distal joint, lowers the moment of inertia, and improves the flexibility and response speed of dexterity hand end-effector operations.

[0026] The second phalanx 3 and the third phalanx 7 of the thumb are connected by the motor shaft A61 of the second phalanx dexterous cylinder 6. Specifically, the motor shaft A61 serves as the rotation axis of the second phalanx 3 relative to the third phalanx 7. The second phalanx dexterous cylinder 6 drives the second phalanx 3 to rotate around the motor shaft A61, achieving active bending of the second phalanx. Since the motor shaft A61 simultaneously performs the dual functions of driving and hinge, it eliminates the need for a separate hinge shaft and coupling, reduces the number of parts, simplifies the assembly process, shortens the transmission chain, and reduces the impact of transmission backlash on positioning accuracy.

[0027] The first phalanx 1 and the second phalanx 3 of the thumb are hinged together by a pin 16. The first phalanx 1 rotates around the pin 16, which provides the center of rotation for the passive bending of the first phalanx. In this embodiment, the first phalanx 1 of the thumb does not have an independent drive cylinder, but is passively driven to bend through the connecting rod 5. This is the main feature of the underactuated design. The underactuated design allows the bending action of the three phalanxes to be completed with only two cylinders. While reducing one cylinder, it retains the equivalent bending degree of freedom as the fully driven scheme, effectively reducing the overall mass, volume and control complexity of the thumb.

[0028] One end of the connecting rod 5 is hinged to the first phalanx 1 of the thumb, and the other end is hinged to the third phalanx 7 of the thumb. When the second phalanx dexterous electric cylinder 6 drives the second phalanx 3 of the thumb to rotate around the motor shaft A61, the rotational motion of the second phalanx 3 is transmitted to the first phalanx 1 of the thumb through the connecting rod 5, causing the first phalanx 1 of the thumb to bend around the pin 16. The connecting rod 5 converts the rotational motion of the second phalanx into the bending motion of the first phalanx, realizing the underactuated transmission effect of simultaneously driving the bending of two phalanxes with a single electric cylinder. The connecting rod transmission structure is simple, has high transmission efficiency, and no elastic slippage, which can ensure a definite kinematic correspondence between the bending angle of the first phalanx and the rotation angle of the second phalanx, which is beneficial for open-loop or semi-closed-loop control.

[0029] A return spring 4 is installed inside the second knuckle 3 of the thumb. One end of the return spring 4 is connected to the second knuckle 3 of the thumb, and the other end is connected to the first knuckle 1 of the thumb. When the second knuckle's dexterous electric cylinder 6 stops outputting or rotates in the reverse direction, the return spring 4 releases its stored elastic potential energy, driving the first knuckle 1 of the thumb to rotate in the reverse direction around the pin 16, returning to its initial extended position. The design of the return spring 4 eliminates the need for an additional electric cylinder to drive the return of the first knuckle, further reducing the number of drive sources. At the same time, the elastic return process is smooth and gentle, avoiding impact damage to the surface of the grasped object caused by rigid return.

[0030] The motor shaft B81 of the third-joint dexterous electric cylinder 8 is connected to a first turntable connector 9 and a second turntable connector 10 on both sides, respectively. The first turntable connector 9 and the second turntable connector 10 are mounted on the turntable base 11. The third-joint dexterous electric cylinder 8 drives the third joint 7 of the thumb to swing sideways around the motor shaft B81. The first turntable connector 9 and the second turntable connector 10 are located on both sides of the motor shaft B81, so that the lateral swing torque is symmetrically transmitted to the turntable base 11 through both sides, avoiding the off-center load and torsional vibration caused by unilateral force transmission, and improving the stability of the lateral swing motion and the symmetry of the structural load-bearing capacity.

[0031] The turntable base 11 is fixedly connected to the coupling 14, which is connected to the motor shaft of the rotary dexterous hand cylinder 12. The rotary dexterous hand cylinder 12 drives the turntable base 11 to rotate around the motor shaft axis of the rotary dexterous hand cylinder 12, thereby causing the thumb mounted on the turntable base 11 to rotate as a whole. The setting of rotational degrees of freedom allows the thumb to adjust its orientation around its own axis, and work with the other fingers to achieve the enveloping grasp of objects of different shapes and postures, significantly expanding the grasping adaptability range of the dexterous hand.

[0032] In this embodiment, the thumb has three independent degrees of freedom: bending degree of freedom (driven by the second joint dexterous electric cylinder 6, transmitted to the first joint via the connecting rod 5), lateral swing degree of freedom (driven by the third joint dexterous electric cylinder 8), and rotational degree of freedom (driven by the rotational dexterous electric cylinder 12). The three degrees of freedom are independent of each other and can move individually or in combination, giving the thumb spatial movement capabilities close to those of a human thumb.

[0033] Example 2 like Figure 1 and Figure 2 As shown, based on Embodiment 1, this embodiment further defines the relevant structures for rotational degrees of freedom and the specific structure of the fixed base: The thumb of the multi-degree-of-freedom underactuated dexterous hand in this embodiment also includes a turntable fixing base 15. A support bearing 13 is press-fitted into the turntable fixing base 15. The press-fitting connection method makes the support bearing 13 and the turntable fixing base 15 form a tight fit without gap, eliminating the rotational wobbling caused by the fit gap, and ensuring the coaxiality and positioning accuracy of the thumb during the rotation process.

[0034] The turntable base 11 passes through the support bearing 13 and is fixed to the coupling 14 by screws. The support bearing 13 provides radial and axial support for the rotation of the turntable base 11, enabling the turntable base 11 to rotate with low friction relative to the turntable fixed base 15. The bearing support method transforms the rotational friction from sliding friction to rolling friction, significantly reducing the rotational drive torque requirement. This allows for the use of a smaller power model for the rotary hand cylinder 12, further reducing the overall weight and size of the thumb. At the same time, the bearing support ensures minimal radial runout of the turntable base 11 during rotation, ensuring that the thumb tip does not shift during rotation and improving the repeatability of gripping and positioning.

[0035] The coupling 14 is fixed to the motor shaft of the rotary maneuvering electric cylinder 12 by a flat-face screw. The flat surface of the screw mates with the flat surface of the motor shaft, achieving circumferential positioning between the coupling 14 and the motor shaft, preventing relative rotation of the coupling 14 on the motor shaft, and ensuring reliable transmission of rotational torque. At the same time, the flat-face screw connection method facilitates easy disassembly and assembly, making later maintenance and cylinder replacement convenient.

[0036] The coupling 14 is located below the turntable base 15, so that the installation position of the rotary electric cylinder 12 is lower than the rotation plane of the turntable base 11, making full use of the space below the base of the thumb, avoiding radial spatial interference between the electric cylinder and the turntable base 11, and making the overall structure more compact.

[0037] The turntable base 11 and the coupling 14 are fixed with screws. When it is necessary to adjust the initial rotation phase angle of the thumb, simply loosen the screws, rotate the turntable base 11 to the target angle, and then tighten it again to complete the phase calibration. No other parts need to be disassembled.

[0038] The bottom end of the turntable fixing base 15 is provided with a threaded hole, which is used to dock with the dexterous hand body. The threaded hole connection method has the advantages of high positioning accuracy, reliable connection and convenient assembly and disassembly, which enables the thumb module to be quickly docked and separated from the dexterous hand body as an independent functional unit, facilitating modular assembly, independent debugging and fault replacement.

[0039] Example 3 like Figure 1 and Figure 2 As shown, based on Embodiment 1, this embodiment further defines the specific structure of the tactile sensing and linkage transmission: A tactile sensor 2 is integrated into the tip of the first joint 1 of the thumb. This sensor detects the magnitude and distribution of contact force in real time when the thumb comes into contact with the object being grasped. Integrating the sensor 2 at the fingertip, placing it at the forefront of the grasping contact, allows for immediate acquisition of contact information, directly sensing the grasping state without the need for force transmission through the middle joints. The feedback signal from the sensor 2 can be used for closed-loop control of the grasping force, preventing damage to the object's surface due to excessive force or slippage due to insufficient force, significantly improving the smoothness and safety of dexterous hand grasping operations.

[0040] Link 5 spans one side of pin 16, so that when the second phalanx 3 of the thumb rotates around motor shaft A61, link 5 applies a bending moment around pin 16 to the first phalanx 1 of the thumb. Specifically, the hinge points of link 5 and the first phalanx 1 of the thumb, and the hinge points of link 5 and the third phalanx 7 of the thumb, are both located on the same side of the axis of pin 16, and the rod body of link 5 spans the plane of pin 16. When the second phalanx 3 of the thumb rotates around motor shaft A61, link 5 is subjected to a pushing and pulling force. The line of action of this pushing and pulling force does not pass through the axis of pin 16, thus generating a bending moment around pin 16 on the first phalanx 1 of the thumb, forcing the first phalanx 1 of the thumb to bend around pin 16. The magnitude of this bending moment is proportional to the pushing and pulling force and lever arm of link 5. By reasonably designing the length of link 5 and the position of the hinge point, the magnitude of the bending moment of the first phalanx and the transmission ratio between the bending speed and the rotation angle of the second phalanx can be adjusted, thereby optimizing the mechanical characteristics of the underactuated transmission.

[0041] The arrangement of connecting rod 5 straddling one side of pin 16 ensures that connecting rod 5 always applies a unidirectional bending moment to the first finger joint during transmission, avoiding the dead point problem that may occur when the connecting rod crosses the pin axis, and ensuring the continuity and monotonicity of the transmission process. That is, the rotation angle of the second finger joint and the bending angle of the first finger joint always maintain a one-to-one correspondence, which is conducive to ensuring control accuracy.

[0042] The return spring 4 is installed inside the second phalanx 3 of the thumb. One end of the return spring 4 is connected to the inner wall of the second phalanx 3, and the other end is connected to the base of the first phalanx 1 of the thumb. Concealing the return spring 4 inside the second phalanx 3 avoids the risk of snagging and unsightly appearance caused by an exposed spring. Simultaneously, the compression stroke of the spring is constrained by the internal space of the second phalanx 3, preventing excessive compression or stretching and potential failure. In its natural state, the return spring 4 keeps the first phalanx 1 of the thumb in a straight position, providing a definite initial positional reference for the transmission of the linkage 5.

[0043] Example 4 like Figure 1 and Figure 3As shown, this embodiment provides a control method for the thumb of a multi-degree-of-freedom underactuated dexterous hand, applied to the thumb of a multi-degree-of-freedom underactuated dexterous hand as described in any one of embodiments one to three. The method includes the following steps: Step 301, Bending control: Control the second knuckle dexterous electric cylinder 6 to drive the second knuckle 3 of the thumb to rotate around the motor shaft A61.

[0044] Specifically, when the second phalanx 3 of the thumb rotates, the connecting rod 5 is displaced by the second phalanx 3 of the thumb. The connecting rod 5 transmits the displacement to the first phalanx 1 of the thumb, causing the first phalanx 1 of the thumb to bend around the pin 16. In this step, only one electric cylinder, the dexterous electric cylinder 6 of the second phalanx, is needed to simultaneously achieve the bending action of the second and first phalanxes. This demonstrates the core advantage of underactuated control, namely, reducing the number of control channels, simplifying the complexity of the control algorithm, and reducing the demand for computing power resources of the control unit.

[0045] Step 302, Reset Control: Control the second knuckle dexterous hand cylinder 6 to stop output or rotate in the reverse direction.

[0046] Specifically, when the second-joint dexterous cylinder 6 stops outputting, the connecting rod 5 no longer applies a bending moment in the bending direction to the first joint 1 of the thumb. The return spring 4 releases the elastic potential energy stored during the bending process, driving the first joint 1 of the thumb to rotate in the opposite direction around the pin 16 to return to its initial straight position. When the second-joint dexterous cylinder 6 rotates in the opposite direction, the second joint 3 of the thumb moves in the opposite direction, and the connecting rod 5 applies a reverse thrust to the first joint 1 of the thumb. This thrust, combined with the elastic force of the return spring 4, accelerates the reset process of the first joint. In this step, the reset process is mainly completed by the release of elastic potential energy, requiring no additional driving energy consumption, making it energy-efficient and effective. At the same time, the elastic reset process is smooth and gentle, avoiding damage to the grasped object and the finger structure itself caused by rigid impact.

[0047] Step 303, Side Sway Control: Control the third joint of the thumb's third joint 7 to sway sideways around the motor shaft B81 using the dexterous electric cylinder 8.

[0048] Specifically, when the motor shaft B81 of the third-joint dexterous electric cylinder 8 rotates, the lateral swing torque is transmitted to the turntable base 11 through the first turntable connector 9 and the second turntable connector 10, causing the third joint 7 of the thumb, along with the first joint 1 and the second joint 3 of the thumb, to swing laterally as a whole. This lateral swing changes the orientation angle of the thumb in the plane perpendicular to the bending motion, allowing the thumb to approach the object to be grasped from different directions, thus achieving stable grasping of asymmetrical objects in conjunction with the bending motion.

[0049] Step 304, Rotation control: Control the rotary smart electric cylinder 12 to drive the turntable base 11 to rotate around the motor shaft axis of the rotary smart electric cylinder 12 through the coupling 14.

[0050] Specifically, the rotation of the turntable base 11 causes the lateral swing-degree-of-freedom components mounted on it, the third phalanx 7 of the thumb, the second phalanx 3 of the thumb, and the first phalanx 1 of the thumb to rotate as a whole, that is, the thumb rotates around the motor axis of the rotating dexterous hand cylinder 12. The rotational motion changes the orientation of the thumb in the horizontal plane, allowing the fingertip of the thumb to point in different directions, forming various grasping configurations in conjunction with the other fingers of the dexterous hand.

[0051] Steps 301 to 304 can be executed independently, in any order, or simultaneously. When executed independently, each step activates only the corresponding single electric cylinder, achieving a single degree of freedom of movement. When executed in combination, multiple electric cylinders move simultaneously or sequentially, achieving complex motion trajectories such as bending, lateral swaying, and rotation. This combined control method allows the thumb to flexibly adjust its posture in three-dimensional space according to the needs of the grasping task, meeting the grasping requirements of objects with various shapes and postures.

[0052] Example 5 like Figure 1 and Figure 3 As shown, based on Embodiment 4, this embodiment further defines the refined control logic for each transmission link in the control method: In the bending control of step 301, link 5 converts the rotational motion of the second phalanx 3 of the thumb into the bending motion of the first phalanx 1 of the thumb. The bending angle of the first phalanx 1 of the thumb is determined by the rotational angle of the second phalanx 3 of the thumb through the transmission relationship of link 5.

[0053] Specifically, when the second knuckle dexterous cylinder 6 drives the second knuckle 3 of the thumb to rotate by an angle θ around the motor shaft A61, the hinge point between the connecting rod 5 and the third knuckle 7 of the thumb moves accordingly. The length of the connecting rod 5 remains unchanged, and this movement is transmitted through the connecting rod 5 to the hinge point with the first knuckle 1 of the thumb, forcing the first knuckle 1 of the thumb to bend by an angle φ around the pin 16. The angle φ and angle θ are determined by the length of the connecting rod 5, the position of the hinge point, and the position of the pin 16, forming a defined kinematic mapping relationship. This defined mapping relationship means that the control unit only needs to control the rotation angle of the second knuckle dexterous cylinder 6 to accurately predict and control the bending angle of the first knuckle, without needing to set up a separate position sensor or drive cylinder for the first knuckle, thus simplifying the sensing configuration and control loop.

[0054] In the lateral swing control of step 303, the motor shaft B81 of the third joint dexterous electric cylinder 8 drives the third joint 7 of the thumb to deflect, causing the second joint 3 of the thumb, which is hinged to it, and the first joint 1 of the thumb, which is hinged to it via pin 16, to swing as a whole. The characteristic of the overall lateral swing is that the relative angles between the three joints remain unchanged during the lateral swing, and the lateral swing motion is equivalent to the rotation of the thumb as a whole around the motor shaft B81. This overall lateral swing method ensures that the bending posture is not disturbed during the lateral swing, that is, the bending angle and the lateral swing angle are decoupled. The control unit can independently adjust the two degrees of freedom of bending and lateral swing without mutual compensation, reducing the algorithm complexity of multi-degree-of-freedom coordinated control.

[0055] In the rotation control of step 304, the rotary dexterous hand cylinder 12 drives the turntable base 11 to rotate via the coupling 14. The turntable base 11 rotates relative to the turntable fixed base 15 via the support bearing 13. The support bearing 13 provides radial and axial constraints to the turntable base 11, ensuring that the rotational movement of the turntable base 11 occurs only around the motor shaft of the rotary dexterous hand cylinder 12, without radial offset or axial movement. The rotation of the turntable base 11 drives the entire structure mounted on it to rotate as a whole, realizing the rotational movement of the thumb as a whole. The rotational movement causes the bending plane and lateral swing plane of the thumb to rotate around the rotation axis in space, providing an additional dimension for adjusting the grasping posture of the dexterous hand.

[0056] In the cooperative control mode, at least two steps from 301 to 304 are executed synchronously. For example, bending control is executed simultaneously with rotation control, so that the thumb adjusts its rotational orientation synchronously during the bending gripping process to achieve a spiral approach gripping of the target object; or bending control is executed simultaneously with lateral swing control, so that the thumb completes bending closure while adjusting its orientation during lateral swing, shortening the total time of the gripping action. During cooperative control, the control unit calculates the target angle and angular velocity of each electric cylinder according to the target gripping posture and synchronously issues control commands to ensure that the motion of the three degrees of freedom is coordinated and consistent on the time axis, forming a smooth composite motion trajectory.

[0057] Example 6 As a supplementary explanation, this embodiment provides a dexterous hand, including a dexterous hand body and a thumb mounted on the dexterous hand body, wherein the thumb is the multi-degree-of-freedom underactuated dexterous hand thumb of any one of embodiments one to three.

[0058] Specifically, the threaded hole at the bottom of the turntable fixing base 15 engages with the corresponding mounting thread on the dexterous hand body, fixing the thumb module to the thumb mounting position on the dexterous hand body. The threaded connection provides reliable positioning and fastening, preventing the thumb from loosening or shifting when subjected to grasping reaction force.

[0059] The dexterous hand body contains a control unit, which is electrically connected to the second knuckle dexterous hand cylinder 6, the third knuckle dexterous hand cylinder 8, and the rotary dexterous hand cylinder 12, respectively, to execute the control methods described in Embodiments 4 and 5. The control unit receives grasping instructions from the host computer or the operator, parses the grasping instructions into target motion parameters for each cylinder, and sends drive signals to the second knuckle dexterous hand cylinder 6, the third knuckle dexterous hand cylinder 8, and the rotary dexterous hand cylinder 12, respectively, to achieve coordinated control of thumb bending, lateral swinging, and rotation.

[0060] The tactile sensor 2 integrated into the fingertip of the first joint of the thumb 1 is connected to the control unit. During the grasping process, the tactile sensor 2 transmits the contact force signal to the control unit in real time. Based on the comparison between the contact force signal and the preset grasping force threshold, the control unit dynamically adjusts the output torque of the second joint dexterous cylinder 6 to achieve closed-loop control of the grasping force. When the detected contact force reaches the target grasping force, the control unit maintains the current output state of the second joint dexterous cylinder 6 to maintain a stable grasping force. When the detected contact force exceeds the safety threshold, the control unit immediately controls the second joint dexterous cylinder 6 to rotate in the opposite direction, releasing the grasped object and preventing overload damage.

[0061] The dexterous hand also has fingers other than the thumb. These fingers work in conjunction with the thumb to perform various grasping modes, such as pinching, enveloping, and lateral grasping. The thumb's three degrees of freedom of motion allows it to adapt to the different requirements of thumb orientation and bending posture in different grasping modes, thus improving the overall grasping success rate and operational flexibility of the dexterous hand.

[0062] In the embodiments disclosed in this invention, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this invention according to the specific circumstances.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A thumb of a multi-degree-of-freedom underactuated dexterous hand, characterized in that, include: The third joint of the thumb (7) integrates the second joint dexterity cylinder (6) and the third joint dexterity cylinder (8). The second joint (3) of the thumb is connected to the third joint (7) of the thumb via the motor shaft A (61) of the second joint dexterous electric cylinder (6), which drives the second joint (3) of the thumb to rotate around the motor shaft A (61); The first phalanx (1) of the thumb is hinged to the second phalanx (3) of the thumb by a pin (16), and the first phalanx (1) of the thumb rotates around the pin (16); The connecting rod (5) has one end hinged to the first phalanx (1) of the thumb and the other end hinged to the third phalanx (7) of the thumb, and is used to drive the first phalanx (1) of the thumb to bend around the pin (16) when the second phalanx (3) of the thumb rotates; A reset spring (4) is installed inside the second joint (3) of the thumb. One end of the reset spring (4) is connected to the second joint (3) of the thumb, and the other end is connected to the first joint (1) of the thumb. It is used to drive the first joint (1) of the thumb to reset. The motor shaft B (81) of the third knuckle dexterous electric cylinder (8) is connected to a first turntable connector (9) and a second turntable connector (10) on both sides. The first turntable connector (9) and the second turntable connector (10) are mounted on the turntable base (11). The third knuckle dexterous electric cylinder (8) drives the third knuckle (7) of the thumb to swing sideways around the motor shaft B (81). The turntable base (11) is fixedly connected to the coupling (14). The coupling (14) is connected to the motor shaft of the rotating dexterous electric cylinder (12). The rotating dexterous electric cylinder (12) drives the turntable base (11) to rotate around the motor shaft axis of the rotating dexterous electric cylinder (12).

2. The thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 1, characterized in that, The thumb of the multi-degree-of-freedom underactuated dexterous hand also includes: The turntable fixing base (15) has an interference fit support bearing (13) inside. The turntable base (11) passes through the support bearing (13) and is fixed to the coupling (14) by screws. The turntable base (11) rotates relative to the turntable fixing base (15) through the support bearing (13).

3. The thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 2, characterized in that, The coupling (14) is fixed to the motor shaft of the rotary dexterous electric cylinder (12) by a flat screw, and the coupling (14) is located below the turntable fixing base (15).

4. The thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 2, characterized in that, The bottom end of the turntable fixing base (15) is provided with a threaded hole, which is used to connect with the dexterous hand body.

5. The thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 1, characterized in that, The fingertip of the first phalanx (1) of the thumb is integrated with a tactile sensor (2).

6. The thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 1, characterized in that, The connecting rod (5) is positioned across one side of the pin (16), such that when the second phalanx (3) of the thumb rotates around the motor shaft A (61), the connecting rod (5) applies a bending moment around the pin (16) to the first phalanx (1) of the thumb.

7. A method for controlling the thumb of a multi-degree-of-freedom underactuated dexterous hand, characterized in that, Applied to the thumb of a multi-degree-of-freedom underactuated dexterous hand as described in any one of claims 1 to 6, the method comprises: The second finger joint dexterous electric cylinder (6) controls the second finger joint (3) of the thumb to rotate around the motor shaft A (61). When the second finger joint (3) of the thumb rotates, it drives the first finger joint (1) of the thumb to bend around the pin (16) through the connecting rod (5). Controlling the second knuckle dexterous hand cylinder (6) to stop output or rotate in the opposite direction, the reset spring (4) releases elastic potential energy to drive the first knuckle (1) of the thumb to reset around the pin (16); The third phalanx of the thumb is controlled by a dexterous electric cylinder (8) to drive the third phalanx of the thumb (7) to swing sideways around the motor shaft B (81); The rotating dexterous electric cylinder (12) is controlled to drive the turntable base (11) to rotate around the motor shaft axis of the rotating dexterous electric cylinder (12) through the coupling (14), so as to drive the thumb to rotate as a whole.

8. The method for controlling the thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 7, characterized in that, The link (5) converts the rotational motion of the second phalanx (3) of the thumb into the bending motion of the first phalanx (1) of the thumb. The bending angle of the first phalanx (1) of the thumb is determined by the rotational angle of the second phalanx (3) of the thumb through the kinematic mapping relationship of the link (5).

9. The method for controlling the thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 7, characterized in that, The motor shaft B (81) of the third joint dexterous electric cylinder (8) drives the third joint (7) of the thumb, together with the first joint (1) and the second joint (3) of the thumb, to sway to the side as a whole.

10. The method for controlling the thumb of a multi-degree-of-freedom underactuated dexterous hand according to claim 7, characterized in that, The rotary smart electric cylinder (12) drives the turntable base (11) to rotate via the coupling (14). The turntable base (11) rotates relative to the turntable fixed base (15) via the support bearing (13) to drive the thumb to rotate around the motor shaft axis of the rotary smart electric cylinder (12).

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