CN120363250A - Underwater flexible mechanical arm with variable rigidity - Google Patents

Abstract

The present invention relates to an underwater variable-rigidity flexible robotic arm, comprising a base, a plurality of linear actuators and a tensioning device at its distal end; a plurality of robotic arm segments, each of which is formed into a columnar shape and has a plurality of segment linear through holes penetrating its own length direction near its circumferential edge, wherein the robotic arm segment closest to the tensioning device is fixed to the tensioning device; a plurality of universal joints, each of which can movably connect any two adjacent robotic arm segments and has a plurality of joint linear through holes penetrating its own axial direction near its circumferential edge; a plurality of line elements, the proximal end of each line element is connected to a corresponding linear actuator, and each line element extends to, passes through the corresponding segment linear through hole of each robotic arm segment and the corresponding joint linear through hole of each universal joint one by one, until its distal end is connected to the robotic arm segment farthest from the tensioning device.

Description

Underwater flexible mechanical arm with variable rigidity

Technical Field

The invention relates to the technical field of robots, in particular to an underwater flexible mechanical arm with variable rigidity.

Background

At present, the traditional flexible underwater mechanical arm mainly comprises three technical schemes, namely (1) a pure flexible mechanical arm without a rigid support, which is based on flexible materials such as silica gel, shape memory alloy and the like, and is bent through pneumatic, hydraulic or rope driving, such as a soft mechanical arm and runner filling design disclosed in Chinese patent application CN117359628A, and is typically applied to a raw soft mechanical arm (such as a bionic octopus tentacle), and (2) a traditional rope-driven flexible mechanical arm with single-mode rigidity, which adopts a wire driving (such as a steel wire rope) to connect joints in series, and provides rigidity through pretightening force, such as Chinese patent application CN113305827A, and (3) an electromagnetic driving flexible mechanical arm, which directly drives the joints through a built-in motor and an electromagnetic valve, and is typically applied to an electric clamping jaw and a rotary joint.

The prior art has the defects that the deep water pressure resistance is insufficient, the joint deformation is easy to occur due to water pressure under the environment of 20m water depth, the movement precision is lost, and the design adopts the combination of static seal and dynamic seal, wherein the dynamic seal can have leakage risk when being used for a long time under the environment of deep water high pressure; the mechanical arm has poor rigidity adjustment capability, the pure flexible mechanical arm cannot resist external load (such as structural collapse when grabbing heavy objects), the mechanical arm is only suitable for low-load scenes (load <0.5 kg), the traditional rope-driven flexible mechanical arm only depends on a passive spring or fixed pretightening force, the rigidity cannot be actively switched according to water flow strength, the mechanical arm can swing under strong water flow, the driving control precision is limited, the pure flexible mechanical arm depends on material deformation feedback, lacks a rigid standard, the omni-directional bending error is greater than 15 degrees, a high-order degree-of-freedom model causes large calculated amount, the real-time control difficulty is high, the traditional rope-driven or connecting rod driving mode lacks a real-time feedback mechanism, the accurate control of omni-directional bending is difficult to realize, the response delay is high (> 500 ms), the tail end positioning error is greater (+ -5 cm) under turbulent flow disturbance, the driving symmetry is insufficient, the traditional four-rope or double-rope driving layout easily causes joint unbalanced load (such as single-side rope slackening during diagonal driving), the motion smoothness is influenced, the sealing and the electromagnetic interference risk is high, the traditional rope-driven driving unit is not separated from a working module, electromagnetic interference exists, electromagnetic elements such as a motor are easy to leak, and the electromagnetic elements are easy to realize waterproof encapsulation, and the dynamic sealing element is easy to be exposed to the environment, and the soft magnetic interference sensing device is required to be coupled with underwater magnetic interference sensing equipment (such as a flexible magnetic coupling device and can be used under the conditions and can be coupled with a flexible magnetic environment and a flexible magnetic sensor and an underwater structure Six-rope symmetrically driven underwater flexible mechanical arm with dual-mode rigidity adjustment.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides an underwater variable-rigidity flexible mechanical arm, which comprises:

a base including a plurality of linear actuators and a tensioning device at a distal end thereof;

A plurality of arm segments, each of which is formed in a column shape, and has a plurality of segment linear through holes penetrating its own length direction near its circumferential periphery, wherein the arm segment closest to the tensioning device is fixed to the tensioning device;

the universal joints are movably connected with any two adjacent mechanical arm sections, and a plurality of joint linear through holes penetrating through the peripheral edge of the universal joints in the axial direction are formed near the peripheral edge of the universal joints;

A plurality of wire elements, each wire element having a proximal end connected to a respective linear actuator and each wire element extending to pass through a corresponding segment linear throughbore of each robotic arm segment and a corresponding joint linear throughbore of each universal joint, one by one, until a distal end thereof is connected to a robotic arm segment furthest from the tensioning device.

In one embodiment, each linear actuator comprises a first motor, a coupling, a screw support and a slider, the first motor is rotatably connected to the screw through the coupling, the distal end of the screw is supported by the screw support, and the slider is sleeved on the screw such that the slider is slidable along the screw by means of cooperation with the screw.

In another embodiment, the proximal end of each wire element is fixedly connected to the slider.

In yet another embodiment, each universal joint includes a first joint plate secured to the arm segment at the proximal end, a second joint plate, and a universal joint movably connecting the first joint plate and the second joint plate.

In a further embodiment, each second joint disc is provided with a resilient element on its surface facing away from the first joint disc, the resilient element being connected to the distally located arm segment.

In yet another embodiment, the resilient element is in a compressed state in an initial state of the underwater variable stiffness flexible manipulator, thereby exerting a repulsive force on the second joint disc and the distally located manipulator segment.

In yet another embodiment, the tensioning device includes a plurality of pulley mechanisms in a one-to-one correspondence with a plurality of wire elements, each pulley mechanism including a pair of clamping plates and a pulley block sandwiched between the pair of clamping plates, the corresponding wire element bypassing the pulley block.

In a further embodiment, the distance between the pairs of jaws is adjustable, and the rotational resistance of the pulley block is inversely proportional to the distance between the pairs of jaws.

In yet another embodiment, the base further comprises a second motor, a guide rail, and a moving platform, the second motor being fixed to the guide rail, the moving platform being displaceably connected to the guide rail, the moving platform being displaceable along the guide rail under the drive of the second motor, a number of linear actuators and tensioners being fixed to the moving platform.

In yet another embodiment, the device further comprises a pneumatic jaw, the solenoid valve being arranged at the base, a second wire element, the pneumatic jaw being mounted to the distal-most arm segment, and a solenoid valve, the second wire element connecting the solenoid valve and the pneumatic jaw.

Compared with the prior art, the underwater variable-rigidity flexible mechanical arm has the advantages that by adopting the composite coupling structure of the rigid framework and the flexible shell, a self-high-strength universal joint (allowing double degrees of freedom to rotate by +/-45 degrees) is arranged in each joint unit, the outer part of each joint unit is coated with a high-performance waterproof silica gel molding shell, a spring is embedded in the joint to form an active elastic structure, the structural compressive capacity is improved, the high stability of structural variable less than 2% can be realized in a 20-meter water depth environment, the 90-degree omni-directional bending capacity of a single joint module is realized, the flexibility and the controllability are both considered, the initial dynamic response capacity of a system is effectively improved by the universal joint and the spring structure, and the bending control precision and the system robustness are enhanced. On the other hand, aiming at the actual situation that the underwater disturbance intensity is greatly changed, the application designs the tensioning pulley block and the adjustable clamping plate mechanism, and can automatically switch to a high-rigidity mode according to the external disturbance intensity on the basis of ensuring a conventional operation mode with low rigidity and high flexibility. The continuous adjustment of rope tension from 0-50N range is realized by controlling the distance between the clamping plate and the tensioning front plate, and the closed loop response of stiffness state switching is realized by matching with the spring loading of the universal joint, so that the low pretightening force is kept in a conventional state, the system response is flexible and natural in motion, the system stiffness can be rapidly improved in strong water flow or high load operation, the stable structure and the terminal attitude maintenance are ensured, the switching delay is less than 200ms, the system has good dynamic self-adaptive capacity, and the operation error under strong disturbance is ensured to be less than 5%.

Drawings

Specific embodiments of the invention are described in further detail below with reference to the attached drawing figures, wherein:

FIG. 1 illustrates a perspective view of an underwater variable stiffness flexible mechanical arm in accordance with an embodiment of the present invention.

Fig. 2 shows a combined perspective view of the manipulator segment and universal joint of fig. 1.

Fig. 3 shows an exploded view of the base shown in fig. 1.

Fig. 4 shows an exploded view of the universal joint shown in fig. 2.

Fig. 5 shows a perspective view of a linear actuator according to another embodiment of the present invention.

Fig. 6 shows an exploded view of a tensioning device according to a further embodiment of the invention.

Detailed Description

The invention will be described in detail below with reference to the drawings and to specific embodiments. The exemplary embodiments and descriptions of the present invention are intended to explain the present invention and are not intended to be limiting.

As shown in fig. 1, the underwater variable stiffness flexible robot arm of the present invention includes a base, a plurality of robot arm segments 2, a plurality of universal joints 1, and a plurality of wire members (not shown). The base comprises several linear actuators 6 and tensioning means 5 at its distal end.

As shown in fig. 2, and in combination with fig. 1, each of the arm segments 2 is formed in a columnar shape. Each arm segment 2 is provided with a plurality of segment linear through holes 4 penetrating the length direction of the arm segment near the circumferential periphery. The arm segment 2 closest to the tensioning device 5 is fixed to the tensioning device 5, and then the subsequent arm segments 2 are connected in series in sequence, thereby forming a flexible arm segment extending distally. Each universal joint 1 movably connects any two adjacent robot arm segments 2. Each universal joint 1 is provided with a plurality of joint linear through holes penetrating through the axial direction of the universal joint near the circumferential periphery. In the axial direction (from the proximal end to the distal end) of the flexible mechanical arm segment, the plurality of segment linear through holes 4 and the plurality of joint linear through holes are in one-to-one correspondence. The proximal end of each wire element is connected to a respective linear actuator 6 and extends to pass through the corresponding segment linear through hole 4 of each manipulator segment 2 and the corresponding joint linear through hole of each gimbal 1 one by one until its distal end is connected to the manipulator segment 2 furthest from the tensioner 5.

As shown in fig. 5, each linear actuator 6 includes a first motor g, a coupling h, a screw i, a screw support j, and a slider, the first motor g being rotatably connected to the screw i through the coupling h, whereby the first motor g drives the screw i to rotate. The distal end of the screw rod i is supported by a screw rod support seat j, in particular, a deep groove ball bearing is built in the screw rod support seat j, so that the screw rod i is allowed to rotate at a high speed. The sliding block is sleeved on the screw rod i, so that the sliding block can slide along the screw rod i by means of matching with the screw rod i. As described above, the proximal end of each wire element is connected to the respective linear actuator 6, in particular, the proximal end of each wire element is fixed (e.g. bound) to the slider of the corresponding linear actuator 6.

As shown in fig. 4, each universal joint 1 includes a first joint plate f, a second joint plate b, and a universal joint member a. The first joint disc f is fixed to a single arm segment 2 located at the proximal end. The universal joint a connects the first joint disc f and the second joint disc b movably. In particular, the universal joint a is provided with several flange bearings d, so that the universal joint a is capable of relative oscillation of the first and second joint discs f, b in two dimensions, in particular with an oscillation amplitude of up to ±45° in both dimensions. Preferably, in order to be able to pass through the corresponding joint linear through-holes without any obstruction, in particular, to avoid the wire elements being scratched by the joint linear through-holes when moving relative to the joint linear through-holes, each joint linear through-hole is provided with a self-lubricating bushing e, so that the wire elements pass therethrough and are not easily scratched to break when relative movement occurs.

Further, the second articulation disc b is provided with a resilient element 3 (e.g. an embedded spring) on its surface facing away from the first articulation disc f, the resilient element 3 being connected to a single mechanical arm segment 2 at the distal end. In the initial state of the underwater variable stiffness flexible manipulator, the elastic element 3 is in a compressed state, whereby a repulsive force is applied to the second joint disc b and the single manipulator segment 2 located distally. In other words, between every two adjacent arm segments 2, the elastic elements 3 in between exert a repulsive force on them, whereby, at the scale of the whole flexible arm segment, several wire elements are tensioned by a plurality of elastic elements 3 in the above-described manner.

As shown in fig. 6, the tensioning device 5 includes a plurality of pulley mechanisms, which are also in one-to-one correspondence with the plurality of wire elements. Each pulley mechanism comprises a clamping plate pair l and a pulley block m clamped between the clamping plate pair l, and corresponding wire elements bypass the pulley block m. The clamping plate pair l is fixed (e.g. by means of bolts) to the end plate k of the tensioning device 5. Moreover, the distance between the pairs of clamping plates l is adjustable (e.g. by means of a threaded connection), which in turn adjusts the clamping degree of the pairs of clamping plates l to the pulley block m, thereby adjusting the rotational resistance of the pulley block m, i.e. the rotational resistance of the pulley block m is inversely proportional to the distance between the pairs of clamping plates l from each other. Thus, adjusting the distance can change the wheelbase of the pulley block m, thereby adjusting the initial pre-tightening force of the line element.

As shown in fig. 3, the base further comprises a second motor, a guide rail 7 and a moving platform. The second motor is fixed to the guide rail 7, and the moving platform is displaceably connected to the guide rail 7, and is displaced along the guide rail 7 by the drive of the second motor. A number of linear actuators 6 and tensioners 5 are fixed to the moving platform. Thus, the several linear actuators 6 and the tensioning device 5 move together with the moving platform, enabling the movement of the underwater variable stiffness flexible mechanical arm in the dimension of the guide rail 7. Even further, the base is a housing (not shown), employing a totally static seal structure and employing a seal made of nitrile rubber, the second motor, solenoid valve and associated electronic control elements being integrated inside the base. The configuration has the advantages that the working space does not contain an electromagnetic radiation source, the configuration is suitable for high-sensitivity operation scenes such as submarine acoustic equipment and magnetic detection instruments, the power transmission path adopts full flexible transmission, a complex electric and pneumatic sealing structure is not needed, the failure rate is obviously reduced, the whole protection level of the whole system is improved by the design of electric separation, and the deepwater operation life is prolonged.

Further, the underwater variable stiffness flexible mechanical arm of the present application further comprises a pneumatic clamping jaw, a second wire element and a solenoid valve. The solenoid valve is arranged at the base and the pneumatic clamping jaw is mounted to the distal most arm segment 2, and the second wire element connects the solenoid valve and the pneumatic clamping jaw. The pneumatic clamping jaw controls the air pressure of the pneumatic clamping jaw through an electromagnetic valve in the base, so that the clamping jaw is opened and closed. The transmission system between the electromagnetic valve and the pneumatic clamping jaw is a second wire element, so that the electromagnetic exposure problem of the traditional electric clamping jaw is avoided, and meanwhile, the stability of long-distance transmission is ensured.

In the present embodiment, both the wire element and the second wire element can be usedA traction rope. Segment linear through-hole 4 and self-lubricating bush e of joint linear through-hole, their inner diameter ratioThe hauling rope diameter is 0.5mm larger, allowing the rope to slide freely while avoiding wear by hole edge rounding (R0.2mm).

During operation of the underwater variable stiffness flexible mechanical arm of the present application, several linear actuators 6 operate independently of each other. Taking any linear actuator 6 as an example, the screw rod i is driven by the first motor g to rotate, so as to drive the sliding block to linearly move, and the wire element fixed to the sliding block pulls the mechanical arm segment 2 positioned at the farthest section under the tensioning action of the elastic element(s) 3 and the driving of the sliding block. In the present embodiment, the underwater variable stiffness flexible robot arm includes six linear actuators 6 and corresponding wire elements which are equally spaced along the circumference of the robot arm segment 2. Thereby, the different actions of the respective linear actuators 6 bring the corresponding wire elements to different extended states, thereby realizing the bending direction and the bending degree of the underwater variable stiffness flexible mechanical arm. The six linear actuators 6 and the corresponding wire elements realize fine sectional driving control, support high-precision posture adjustment (control error <3 degrees) of any direction of a single joint, improve the smoothness and driving force balance of joint movement, effectively avoid the problem of unbalanced load and swing of a traditional rope driving structure, ensure that the whole system has good redundancy and robustness, and can maintain the stability of the whole movement track even if partial rope tension is slightly deviated. Of course, in other embodiments, other numbers of linear actuators 6 and corresponding wire elements are also possible.

Furthermore, during operation of the underwater variable stiffness flexible mechanical arm of the present application, each corresponding pulley mechanism may be operated in different modes, including a normal mode and a strong disturbance mode. Wherein, the pulley block m keeps lower pretightening force and depends on the conventional mode under low-custom water flow environmentThe real-time pulling force of the traction rope controls the bending of each universal joint 1 to realize high flexibility, a strong disturbance mode is suitable for the high-speed water flow environment, the clamping plate clamps the pulley block m, the pretightening force is increased, the compression amount of the elastic element 3 is locked, and the overall rigidity is improved to resist water flow impact.

While the foregoing has been provided by embodiments of the present invention with particularity, the principles and modes of carrying out the embodiments of the present invention have been described in detail by way of example only, and are not intended to limit the invention to the particular embodiments and modes of carrying out the invention, as will be apparent to those skilled in the art from consideration of this disclosure.

Claims (10)

1. An underwater variable stiffness flexible mechanical arm, comprising:

a base including a plurality of linear actuators and a tensioning device at a distal end thereof;

A plurality of arm segments, each of which is formed in a column shape, and has a plurality of segment linear through holes penetrating a length direction thereof, near a circumferential periphery thereof, wherein the arm segment closest to the tensioning device is fixed to the tensioning device;

The universal joints are movably connected with any two adjacent mechanical arm sections, and a plurality of joint linear through holes penetrating through the mechanical arm sections in the axial direction are formed near the circumferential periphery of the mechanical arm sections;

a plurality of wire elements, each of the wire elements having a proximal end connected to a respective one of the linear actuators and each of the wire elements extending to, one by one, pass through a corresponding one of the segment linear throughholes of each of the robotic arm segments and a corresponding one of the joint linear throughholes of each of the universal joints until a distal end thereof is connected to the robotic arm segment furthest from the tensioning device.

2. The underwater variable stiffness flexible mechanical arm of claim 1, wherein each of the linear actuators comprises a first motor, a coupling, a screw support, and a slider, the first motor being rotatably connected to the screw through the coupling, a distal end of the screw being supported by the screw support, the slider being sleeved on the screw such that the slider is slidable along the screw by means of engagement with the screw.

3. The underwater variable stiffness flexible mechanical arm of claim 2 wherein the proximal end of each wire element is fixedly connected to the slider.

4. The underwater variable stiffness flexible robotic arm of claim 1, wherein each of the universal joints comprises a first joint plate secured to the arm segment at a proximal end, a second joint plate, and a universal connection movably connecting the first joint plate and the second joint plate.

5. The underwater variable stiffness flexible robotic arm of claim 4, wherein each of the second articulation discs is provided with a resilient element on a surface thereof facing away from the first articulation disc, the resilient element being connected to the distal arm segment.

6. The underwater variable stiffness flexible robotic arm of claim 5, wherein in an initial state of the underwater variable stiffness flexible robotic arm, the resilient element is in a compressed state, thereby exerting a repulsive force on the second articular disc and the distally located robotic arm segment.

7. The underwater variable stiffness flexible mechanical arm of claim 1, wherein the tensioning device comprises a plurality of pulley mechanisms in one-to-one correspondence with a plurality of the wire elements, each pulley mechanism comprising a pair of clamping plates and a pulley block sandwiched between the pair of clamping plates, the corresponding wire element bypassing the pulley block.

8. The underwater variable stiffness flexible mechanical arm of claim 7 wherein the distance between the pair of cleats is adjustable and the rotational resistance of the pulley block is inversely proportional to the distance between the pair of cleats.

9. The underwater variable stiffness flexible mechanical arm of claim 1, wherein the base further comprises a second motor, a rail, and a moving platform, the second motor being fixed to the rail, the moving platform being displaceably connected to the rail, the moving platform being displaced along the rail under the drive of the second motor, a number of the linear actuators and the tensioning device being fixed to the moving platform.

10. The underwater variable stiffness flexible mechanical arm of claim 1 further comprising a pneumatic clamping jaw, a second wire element and a solenoid valve, the solenoid valve being disposed at the base, the pneumatic clamping jaw being mounted to the distal-most arm segment, the second wire element connecting the solenoid valve and the pneumatic clamping jaw.