Flexible mechanical arm device with any curvature

Abstract

The invention provides a flexible mechanical arm device with any curvature. The flexible mechanical arm device comprises a rigid mechanical arm and a flexible actuator, the flexible actuator is installed on a first-stage arm of the rigid mechanical arm through a flexible actuator base, and the first-stage arm drives the flexible actuator to rotate by controlling the flexible actuator base; the flexible actuator comprises a silica gel base body, and three sets of SMA wires distributed circumferentially are fixed to the silica gel base body through a set of annular fixing devices. The rigid mechanical arm comprises a base, a third-stage arm is installed on the base, the third-stage arm is driven to rotate horizontally, the third-stage arm drives a second-stage arm to rotate, and the second-stage arm drives a first-stage arm to rotate. The motion precision and safety are improved, the heating temperature of the SMA wire is accurately controlled through the PWM technology, closed-loop control over the flexible actuator is achieved, and the deformation error of the pure flexible mechanical arm is reduced; through combination of the flexible tail end and the rigid body, rigid damage caused when the rigid mechanical arm makes contact with an object is avoided, and the problem that the control precision of a pure flexible structure is insufficient is solved.

Description

Technical Field

[0001] The present invention belongs to the field of machining, and particularly relates to a flexible robotic arm device with arbitrary curvature. Background Art

[0002] Unlike rigid robotic arms, flexible robotic arms generally do not have a dedicated standardized design and evaluation system, and there is even no established part library. However, different from the common flexible robotic arms driven by hydraulics or motors, flexible robotic arms have various driving methods, such as pneumatic drive, shape memory alloy drive, polymer, wire drive, etc. Different power methods correspond to different structures and advantages.

[0003] In 2002, the Stanford Research Institute in the United States developed a cylindrical counter-functional actuator based on electronic EPA using dielectric elastomers. The diameter of this actuator is about 1 cm, the length is 7 cm, and the actuation length is about 5 cm. This actuator uses a non-linear electroactive insulating rubber material as the driving source. The maximum strain of this material can reach 300%, but it requires a strong external electric field of up to 5.5 kV for driving, which has potential high-voltage safety hazards; the driving material (non-linear electroactive insulating rubber) may accelerate aging under extreme electric fields; high strain (300%) may cause material fatigue and irreversible deformation, affecting long-term reliability.

[0004] In 2005, Columbia University in the United States developed a micro catheter surgery robot. The research concept of this robot comes from the movement structure of snakes, and its volume is very small, with a diameter of only 2 mm. This robot has a simple and reliable structure. Three groups of wire ropes are passed through spacers evenly distributed along the axis of the flexible matrix material. Each group of wire ropes is equipped with a wire winding and unwinding motor. The movement control of the robot is achieved through different combinations of the lengths of the wire ropes wound and unwound between the three motors. However, the wire ropes are prone to wear and elastic deformation under long-term tension, resulting in a decrease in control accuracy; the coordinated control of multiple groups of wire ropes is highly complex, relying on the synchronous operation of multiple motors, with high system energy consumption; the eccentric wire rope layout may cause uneven stress distribution inside the silicone matrix, leading to local damage.

[0005] In 2004, Clemson University in the United States developed a flexible robotic arm jointly driven by ropes and air pressure. This robotic arm consists of a central airbag tube and an outer actuation layer wrapped around it. The central airbag tube serves as a skeleton to provide a certain degree of stiffness support for the overall flexible robotic arm, while the outer actuation layer provides driving force for the flexible robotic arm, enabling movements such as bending, grasping, winding, and telescoping, and the maximum telescoping rate can reach 500%. However, the coordinated control of the central airbag tube and the outer actuation layer is difficult, and movement interference is likely to occur; a 500% telescoping rate requires extremely high tear resistance of the rubber material; the pneumatic system needs continuous air supply, and its practicability is limited in an environment without a stable air source.

[0006] Zhejiang University of Technology has developed several gas-driven flexible joints, including torsion joints and bending joints. And a three-fingered gripper has been developed using these flexible joints. This gripper, which uses a gas pump as the power source and is made of rubber to achieve flexibility and has three bending actuators, is mainly composed of the above-mentioned various joints. The torsion degree of freedom for realizing the rotation perpendicular to the gripper axis at the wrist of this robotic gripper is achieved by the torsion joint, while the three pneumatic flexible bending joints are used to realize the grasping action of the robotic gripper. However, the rubber material is prone to creep under repeated air pressure impacts, resulting in a reduction in the joint reset accuracy; the gas pump power source is relatively large in volume and it is difficult to achieve miniaturization and integration; the gas-driven response speed is limited by the pipeline length and the dynamic performance is poor.

[0007] For robotic arms, environmental pollution mainly includes pollution in terms of power sources and noise pollution. In terms of power sources, there are various types of power sources for robotic arms, mainly driven by electricity and fossil fuels. Therefore, at the present stage, it is necessary to increase the research on robotic arms, gradually reduce the dependence on fossil fuels, and gradually transform into clean energy to reduce the burden on the environment. Regarding noise pollution, the noise of robotic arms mainly comes from the vibration noise during the operation of fossil fuel engines. When reducing the dependence on fossil fuels, the noise pollution will also be reduced accordingly. Therefore, increasing the research on robotic arms can also promote the realization of environmentally friendly development. In summary, strengthening the research on robotic arms can achieve the sustainable development of the environment and society. Summary of the Invention

[0008] The purpose of the present invention is to provide a flexible robotic arm device with arbitrary curvature, which can improve the motion accuracy and safety of the flexible robotic arm device. By precisely controlling the heating temperature of the SMA wire through PWM technology, the closed-loop control of the flexible actuator is realized, and the deformation error of the pure flexible robotic arm is reduced.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A flexible robotic arm device with arbitrary curvature, comprising: a rigid robotic arm and a flexible actuator. The flexible actuator is installed on the first-level arm of the rigid robotic arm through a flexible actuator base, and the first-level arm drives the flexible actuator to rotate by controlling the flexible actuator base.

[0011] The flexible actuator includes a silicone matrix, and three groups of circumferentially distributed SMA wires are fixed on the silicone matrix through a set of annular fixators.

[0012] The rigid robotic arm includes a base, on which a third-level arm is installed to drive the horizontal rotational movement of the third-level arm. The third-level arm drives the second-level arm to rotate, and the second-level arm drives the first-level arm to rotate.

[0013] Further, the flexible actuator is connected to the actuator gear through an actuator bearing retaining ring. The actuator gear meshes with an actuator motor gear, and the actuator motor gear is mounted on an actuator motor. The actuator gear and the actuator motor are mounted on the flexible actuator base.

[0014] Further, the flexible actuator base is mounted on a first-stage arm gear. The first-stage arm gear meshes with a first-stage arm motor gear, and the first-stage arm motor gear is mounted on a first-stage arm motor. The first-stage arm motor is mounted on the first-stage arm.

[0015] Further, the flexible actuator base is connected to the housing of the third-stage arm through a flange cover, thereby driving the horizontal rotational movement of the third-stage arm. A support shaft is provided inside the third-stage arm, and the support shaft is driven by a turbine and a worm. The turbine is driven by a base motor.

[0016] Further, bearings are respectively provided between the support shaft and the turbine and the two sides of the box body to ensure smooth rotation.

[0017] Further, the second-stage arm and the first-stage arm are connected to the first-stage arm transmission shaft through a bearing.

[0018] Further, a second-stage arm motor is mounted on the outside of the second-stage arm, and a second-stage expansion reducer is arranged inside the second-stage arm. The second-stage arm motor drives the rotation of the first-stage arm base through the second-stage expansion reducer, thereby driving the rotation of the first-stage arm.

[0019] Further, a third-stage arm transmission shaft and a third-stage arm motor are mounted inside the third-stage arm through bearings.

[0020] Further, the third-stage arm motor drives the rotation of the third-stage arm transmission shaft through meshing transmission of a third-stage arm gear, thereby driving the rotation of the third-stage arm.

[0021] Further, the SMA wire is controlled by Pulse Width Modulation (PWM) technology, and the digital signal analog output of a microprocessor is used to achieve electric heating control.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention has high flexibility and environmental adaptability. By using a flexible actuator driven by Shape Memory Alloy (SMA) and combined with a silicone matrix material, it can achieve multi-directional bending deformation with arbitrary curvature and adapt to complex environments. The wrist design adopts an independent degree of freedom structure, significantly improving the attitude adjustment ability of the end effector and enhancing the obstacle avoidance ability.

[0024] The present invention improves the motion accuracy and safety of the flexible robotic arm device. By precisely controlling the heating temperature of the SMA wire through PWM technology, closed-loop control of the flexible actuator is achieved, reducing the deformation error of the pure flexible robotic arm. The combination of the flexible end and the rigid body not only avoids hard damage when the rigid robotic arm contacts an object but also overcomes the problem of insufficient control accuracy of the pure flexible structure.

[0025] The present invention meets the requirements of large-range operation ability and structural stability. The multi-stage rigid arms (the first-stage arm, the second-stage arm, and the third-stage arm) are designed with structures such as gear transmission and worm and worm gear to support the stable operation of the robotic arm in a large-range space. The base uses thrust ball bearings and worm and worm gear transmission to ensure high load-bearing capacity and smooth operation of the horizontal rotation degree of freedom.

[0026] The present invention is energy-saving, environmentally friendly, and low-noise. It uses electric drive to replace the traditional hydraulic or pneumatic system, reduces dependence on fossil fuels, and reduces noise pollution (such as the low-noise design of planetary reducers and servo motors). At the same time, the lightweight design (such as the hollow arm structure) reduces energy consumption and improves energy utilization efficiency.

[0027] The flexible actuator of the present invention will use shape memory alloy as the actuator. By passing an electric current through the shape memory alloy to heat it up, it will deform. When the magnitude of the electric current flowing into the shape memory alloy is different, the temperature change of the shape memory alloy is also different. The higher the temperature of the shape memory alloy, the faster the heat it dissipates to the outside. When its temperature reaches a certain temperature point, the heat generated by the electric current passing through the shape memory alloy is balanced with the heat radiated by the shape memory alloy to the outside world. At this time, the temperature of the shape memory alloy will become stable, and the corresponding deformation degree of the shape memory alloy at different temperatures is also different. That is to say, the deformation degree of the flexible matrix material driven by the shape memory alloy actuator is different, thus achieving the effect of controlling the motion of the flexible actuator. Therefore, to control the motion of the flexible actuator, it is necessary to use a suitable electric heating technology to heat the shape memory alloy actuator. The present invention uses pulse width modulation technology PWM control, which has good effects and is simple to control. PWM specifically refers to using the digital signal of the microprocessor to replace the analog output to achieve electric heating control. Therefore, the flexible actuator designed in this paper uses PWM technology control.

[0028] The flexible actuator of the present invention uses pulse technology to control the motion of the flexible actuator, which can reduce the volume ratio of the power source, miniaturize the flexible actuator, reduce the burden on the rigid body, and overcome the noise and vibration effects of conventional power sources such as motors and air pumps, with good control effects. Brief Description of the Drawings

[0029] Attached Figure 1 is a schematic structural diagram of the present invention.

[0030] Attached Figure 2 is a schematic diagram of the connection between the flexible actuator and the first-stage arm of the present invention.

[0031] Attached Figure 3 is a schematic structural view of the flexible actuator of the present invention.

[0032] Attached Figure 4 is a schematic internal structure view of the three - stage robotic arm of the present invention.

[0033] Attached Figure 5 is a schematic internal structure view of the base of the present invention.

[0034] Attached Figure 6 is an ideal bending diagram of a silicone cylinder.

[0035] Attached Figure 7 is the schematic illustration of the rectangular coordinate system described in the embodiment of the present invention Figure 1 .

[0036] Attached Figure 8 is the schematic illustration of the rectangular coordinate system described in the embodiment of the present invention Figure 2 .

[0037] In the figure: 1. Flexible actuator; 101. Silicone matrix; 102. SMA wire; 103. Ring fixator; 2. Actuator bearing retainer; 3. Actuator gear; 4. Actuator motor gear; 5. Actuator motor; 6. Actuator base; 7. First - stage arm gear; 8. First - stage arm motor; 9. First - stage arm shaft; 10. First - stage arm base; 11. Second - stage expansion reducer; 12. Second - stage arm motor; 13. Second - stage arm; 14. Third - stage arm; 15. Third - stage arm motor; 16. Base; 17. Base motor; 18. Third - stage arm gear; 19. Support shaft; 20. Turbine; 21. Bearing 1; 22. Worm; 23. Bearing 2; 24. Flange cover. Detailed implementation manners

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] The present invention provides a flexible robotic arm device with arbitrary curvature. As shown in the attached Figure 1 figure, it includes: a rigid robotic arm, a flexible actuator 1. The flexible actuator 1 is installed on the first - stage arm 9 of the rigid robotic arm through a flexible actuator base 6, and the first - stage arm drives the flexible actuator 1 to rotate by controlling the flexible actuator base 6;

[0040] The flexible actuator 1 includes a silicone matrix 101, and three groups of circumferentially distributed SMA wires 102 are fixed on the silicone matrix 101 through a group of ring fixators 103;

[0041] The rigid robotic arm includes a base 16, on which a three-stage arm 14 is installed to drive the horizontal rotational movement of the three-stage arm 14. The three-stage arm 14 drives the secondary arm 13 to rotate, and the secondary arm 13 drives the primary arm 9 to rotate.

[0042] In this embodiment, the secondary arm 13 and the primary arm 9 are connected to the primary arm transmission shaft through bearings.

[0043] In this embodiment, a secondary arm motor 12 is installed outside the secondary arm 13, and a secondary expansion reducer 11 is arranged inside the secondary arm 13. The secondary arm motor 12 drives the rotation of the primary arm base 10 through the secondary expansion reducer 11, thereby driving the rotation of the primary arm 9.

[0044] Inside the three-stage arm 14, a three-stage arm transmission shaft and a three-stage arm motor 15 are installed through bearings.

[0045] As shown in the appendix Figure 2 As shown, the flexible actuator 1 is connected to the actuator gear 3 through an actuator bearing retainer 2. The actuator gear 3 meshes with the actuator motor gear 4. The actuator motor gear 4 is installed on the actuator motor 5. The actuator gear 3 and the actuator motor 5 are installed on the flexible actuator base 6.

[0046] The flexible actuator base 6 is installed on the primary arm gear 7. The primary arm gear 7 meshes with the primary arm motor gear. The primary arm motor gear is installed on the primary arm motor 8. The primary arm motor 8 is installed on the primary arm 9.

[0047] As shown in the appendix Figure 3 As shown, the SAM wire and the axis of the silica gel cylinder are embedded therein. There are three groups of SMA wires placed in the silica gel matrix material. The included angle between the SMA wires is set to 120°. The SAM wire and the silica gel body are connected through an annular fixator.

[0048] As shown in the appendix Figure 5 As shown, the flexible actuator base 6 is connected to the housing of the three-stage arm 14 through a flange cover 24, thereby driving the horizontal rotational movement of the three-stage arm 14. Inside the three-stage arm 14, there is a support shaft 19. The support shaft 19 is driven by a turbine 20 and a worm 22. The turbine 20 is driven by a base motor 17.

[0049] Bearings are respectively provided between the support shaft 19 and the turbine 20 and both sides of the box body to ensure smooth rotation.

[0050] As shown in the appendix Figure 4 As shown, the three-stage arm motor drives the rotation of the three-stage arm transmission shaft through meshing transmission of the three-stage arm gear 18, thereby driving the rotation of the three-stage arm 14.

[0051] In this embodiment, the base 16 is used to support the weight of the entire rigid arm and provide a horizontal rotational degree of freedom for the rigid manipulator by connecting with the third-level arm 14. The main shaft is driven by a turbine 20 and a worm 22. The motor drives the turbine and worm to rotate, thereby controlling the rotation of the support shaft 19. The support shaft 19 is connected to the third-level arm housing through a flange cover, thereby driving the horizontal rotational movement of the third-level arm.

[0052] In this embodiment, the third-level arm 14 plays two main roles: one is to support parts such as the second-level arm 13, and the other is to endow the manipulator with a horizontal rotational movement. The third-level arm 14 is connected to the second-level arm 13 through a cantilever shaft, and the motor drives the third-level arm 14 to rotate through gear meshing.

[0053] The second-level arm 13 is connected to the first-level arm 9 through a shaft. The second-level arm motor 12 is placed outside the second-level arm 13. A second-level expansion reducer 11 is arranged inside the second-level arm 13. The second-level arm motor 12 drives the first-level arm 9 to rotate through the second-level expansion reducer 11. By driving and adjusting through the third-level arm 14 and the second-level arm motor 12, the positions of the flexible actuator 1 on the horizontal axis and the vertical axis on the horizontal plane can be controlled.

[0054] The first-level arm 9 drives the gear to rotate through the drive motor, which can control the rotation of the flexible actuator base, thereby controlling the rotation of the pitch angle of the flexible actuator.

[0055] The flexible actuator base 6 can control the rotation of the flexible brake itself by driving the actuator motor 5 to drive the actuator gear 3 to rotate.

[0056] The linkage movement of the third-level arm 14 and the flexible actuator 1 enables the brake of the flexible actuator to work at any position and any angle.

[0057] In this embodiment, the flexible actuator 1 is controlled by shape memory alloy SMA wires. Since there is a linear relationship between the stress generated by the shape memory alloy SMA wires and their strain, when the silicone matrix bends, the bending angle is related not only to the density parameters, softness, etc. of the silicone matrix itself, but also to the stress of the SMA wires.

[0058] As shown in the appendix Figure 6 shows an ideal bending diagram of a silicone cylinder. For any bent silicone, the following geometric relationship exists between the eccentricity of its SMA wire and the wire attachment point:

[0059]

[0060] e0 is the projection distance of the SMA wire distance eccentricity in the y direction, d is the distance from the wire attachment point of the SMA wire on the cross-section where the Y axis is located to the center of the circle after the silicone matrix bends, l is the length of the SMA wire, and θ is the bending angle of the silicone matrix. l o$l_0$ is the original length of the SMA wire, $\Delta l$ is the contraction amount of the SMA wire, and $\varepsilon$ is the strain of the SMA wire.

[0061] The distance d from the centromere to the bending center of the silicone matrix can be expressed as:

[0062]

[0063] Substituting the above formula into (1), the strain of the SMA wire is

[0064]

[0065] When a single group of SMA wires is driven, the neutral plane of the bent silicone matrix will shift at this time, towards the opposite side of the driving SMA wire. Because for any cross-section taken, the strain of the two groups of SMA wires that are passively stretched is less than that of the SMA wire on the driving side. Assuming that the neutral plane is still at the axis, the moment generated by the SMA wire on the tensile side is less than the moment generated by the SMA wire on the driving side, that is, the moment on the tensile side of the silicone matrix is greater than the moment on the contraction side. Because when the neutral plane is at the axis, the strains on both sides of the axis of the silicone matrix are the same and the generated moments are the same, which is contrary to the above inference. Therefore, the neutral plane can only conform to the above inference when it is on the tensile side. Here, assume that the position offset of the neutral plane is e 中 , assuming that the pure bending curvature of the neutral plane is k, then it can be deduced that the radius of curvature of the neutral plane is:

[0066]

[0067] Let the driving-end SMA wire be SMA1, and the counterclockwise SMA wires be SMA2 and SMA3 respectively, and establish a rectangular coordinate system, as shown in the appendix Figure 7 as shown.

[0068] Let the abscissa of any surface parallel to the neutral plane be x0, then its curvature can be expressed as:

[0069]

[0070] where k1 is the curvature of this surface and R1 is the radius of curvature of this surface.

[0071] The bending angle of the silicone matrix is:

[0072] α = kl0 (6)

[0073] l0 is the length of the silicone matrix, which is equivalent to the arc length of the curvature circle of the neutral plane.

[0074] The tensile force generated in SMA1 is:

[0075]

[0076] r0 is the radius of the SMA wire

[0077] The tensile forces in SMA2 and SMA3 can be expressed as

[0078]

[0079] By combining (3) and (5), we can obtain

[0080]

[0081] In this way, the relationship between strain and centrifugal distance is obtained, so that the displacement of the brake can be controlled by controlling the strain of the SMA wire.

[0082] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flexible mechanical arm device with arbitrary curvature, characterized in that: include: A rigid mechanical arm and a flexible actuator (1), wherein the flexible actuator (1) is mounted on a primary arm (9) of the rigid mechanical arm via a flexible actuator base (6), and the primary arm drives the flexible actuator (1) to rotate by controlling the flexible actuator base (6); The flexible actuator (1) comprises a silicone base (101), on which three groups of circumferentially distributed SMA wires (102) are fixed via a group of annular fixers (103); The rigid mechanical arm comprises a base (16), on which a tertiary arm (14) is mounted, driving the horizontal rotational movement of the tertiary arm (14), the tertiary arm (14) driving the secondary arm (13) to rotate, and the secondary arm (13) driving the primary arm (9) to rotate.

2. The flexible mechanical arm device with arbitrary curvature according to claim 1, characterized in that: The flexible actuator (1) is connected to the actuator gear (3) via the actuator bearing retaining ring (2); the actuator gear (3) is meshed with the actuator motor gear (4); the actuator motor gear (4) is mounted on the actuator motor (5); and the actuator gear (3) and the actuator motor (5) are mounted on the flexible actuator base (6).

3. The flexible mechanical arm device with arbitrary curvature according to claim 1, characterized in that: The flexible actuator base (6) is mounted on a primary arm gear (7), the primary arm gear (7) is meshed with a primary arm motor gear, the primary arm motor gear is mounted on a primary arm motor (8), and the primary arm motor (8) is mounted on the primary arm (9).

4. The flexible mechanical arm device with arbitrary curvature according to claim 2 or 3, characterized in that: The flexible actuator base (6) is connected to the shell of the three-stage arm (14) through a flange cover (24), thereby driving the horizontal rotation movement of the three-stage arm (14). The three-stage arm (14) has a support shaft (19) inside, and the support shaft (19) is driven by a turbine (20) and a worm (22), and the turbine (20) is driven by a base motor (17).

5. The flexible mechanical arm device with arbitrary curvature according to claim 4, characterized in that: The support shaft (19) and the turbine (20) are provided with bearings on both sides of the casing to ensure smooth rotation.

6. The flexible mechanical arm device with arbitrary curvature according to claim 5, characterized in that: The secondary arm (13) and the primary arm (9) are connected to the primary arm transmission shaft via a bearing.

7. The flexible mechanical arm device with arbitrary curvature according to claim 6, characterized in that: A secondary arm motor (12) is installed on the outside of the secondary arm (13), and a secondary deployable reducer (11) is arranged inside the secondary arm (13). The secondary arm motor (12) drives the primary arm base (10) to rotate through the secondary deployable reducer (11), thereby driving the primary arm (9) to rotate.

8. The flexible mechanical arm device with arbitrary curvature according to claim 7, characterized in that: A three-stage arm transmission shaft and a three-stage arm motor (15) are installed inside the three-stage arm (14) via bearings.

9. The flexible mechanical arm device with arbitrary curvature according to claim 8, characterized in that: The three-stage arm motor drives the three-stage arm transmission shaft to rotate through the meshing transmission of the three-stage arm gear (18), thereby driving the three-stage arm (14) to rotate.

10. The flexible mechanical arm device with arbitrary curvature according to claim 9, characterized in that: The SMA wire (102) is controlled by pulse width modulation technology (PWM), and uses digital signal analog output of a microprocessor to achieve electric heating control.

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