Bionics-based rigid-flexible coupling under-actuated manipulator

Abstract

The application belongs to the technical field of mechanical hands, and particularly relates to a rigid-flexible coupling under-actuated mechanical hand based on bionics, wherein a palm base is installed on a force sensing module, and a plurality of bionic finger modules are connected to the palm base; a driving unit is installed on an external base body, and comprises a same number of driver groups corresponding to the bionic finger modules; a tendon driving system comprises a same number of tendon groups corresponding to the bionic finger modules; one end of each active tendon and antagonistic tendon in each group is connected to the output end of two rotary drivers in the group, and the other end is connected to the corresponding bionic finger module after passing through the force sensing module and the palm base. The application integrates a rigid-flexible coupling structure and an antagonistic driving principle, and innovatively combines a series crank slider mechanism and an antagonistic tendon system, so that the problems that the existing mechanical hand cannot grasp fragile and large-mass rigid objects and lacks a self-locking mechanism to cause high energy consumption are solved.

Description

Technical Field

[0001] This invention belongs to the field of robotic arm technology, specifically a biomimetic rigid-flexible coupling underactuated robotic arm. Background Technology

[0002] As a key actuator at the end effector of general-purpose robots, robotic arms are widely used in industrial automation, service robots, medical rehabilitation, and rescue detection. The grasping ability and adaptability of a robotic arm directly determine the robot's operational performance. Early robotic arms were mainly simple gripper-type and parallel movement mechanisms, suitable for automated factory production lines, but lacking versatility. To improve the flexibility and adaptability of robotic arms, researchers began exploring human-hand-like design concepts, developing dexterous hands with multiple degrees of freedom and multiple joints. Traditional robotic arms mostly employ a fully actuated approach, with each joint controlled by an independent actuator. While offering high precision, this approach is structurally complex, costly, and uses cumbersome control algorithms, making it difficult to popularize in applications requiring lightweight and low-cost designs. To address these issues, underactuated robotic arms have emerged. These arms control more degrees of freedom with fewer actuators, offering advantages such as simple structure, strong adaptability, and low cost, and have become a current research hotspot.

[0003] However, existing underactuated manipulators still have significant limitations. From a bionic perspective, the human hand's ability to grasp with dexterity and power lies in the musculoskeletal system composed of antagonistic muscle pairs, such as the flexor muscles that control finger flexion and the extensor muscles that control extension. This antagonistic actuation provides a perfect biological blueprint for achieving precise and dynamic adjustment of grasping force. Currently, most underactuated manipulators use motors directly coupled with rigid linkages, making it difficult to simultaneously handle objects with different characteristics through different grasping modes and precise force control. This makes it difficult to balance the flexibility required for grasping fragile items (such as eggs and paper cups) with the high-load grasping capacity required for grasping heavy, rigid items (such as tools and water bottles). Therefore, there is an urgent need for underactuated manipulators capable of grasping objects of different shapes, materials, and weights. Secondly, most underactuated manipulators require continuous power to the motor to maintain the grasping force when grasping heavy objects, which not only leads to low energy efficiency but may also pose reliability risks due to motor overheating. Although some designs incorporate self-locking mechanisms, they are often complex in structure and have poor versatility. Summary of the Invention

[0004] In order to improve the above-mentioned problems of existing underactuated manipulators, the present invention aims to provide a biomimetic rigid-flexible coupling underactuated manipulator.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention includes a hand base, bionic finger modules, a drive unit, a tendon cable transmission system, a force sensing module, and a control system. The hand base is mounted on the force sensing module, and multiple bionic finger modules are connected to the hand base. Each bionic finger module includes a proximal phalanx, a middle phalanx, and a distal phalanx, which form the finger body in the form of two crank-slider mechanisms connected in series. The drive unit is mounted on an external base and includes a set of actuators, one-to-one with the number of bionic finger modules. Each actuator set includes two rotating actuators capable of forward and reverse rotation. The tendon cable transmission system includes tendon cable sets, one-to-one with the number of bionic finger modules. Each tendon cord group includes one active tendon cord and one antagonistic tendon cord. Each active tendon cord and each antagonistic tendon cord is equipped with a spring. One end of each active and antagonistic tendon cord in each group is connected to the output ends of two rotary actuators in the group. The other end of each active and antagonistic tendon cord in each group passes through a force sensing module and a palm base, and is connected to the corresponding bionic finger module. The active tendon cord is driven by the connected rotary actuator to pull the bionic finger module to bend. The antagonistic tendon cord is driven by the connected rotary actuator to pull the bionic finger module to extend and return to its original position or to adjust the stiffness of the bionic finger module. The force sensing module and each rotary actuator are connected to the control system.

[0007] The bionic finger module further includes a knuckle support shaft and a knuckle base. The knuckle base is mounted on a palm base. The knuckle support shaft is slidably connected to the knuckle base. The distal knuckle is slidably connected to the knuckle support shaft. The two ends of the proximal knuckle are respectively hinged to the knuckle base and the knuckle support shaft. The two ends of the middle knuckle are respectively hinged to the knuckle support shaft and the distal knuckle.

[0008] The proximal phalanx, phalanx base, and phalanx support shaft form a crank-slider mechanism. The phalanx base serves as the mounting base for the crank-slider mechanism, the proximal phalanx is the crank of the crank-slider mechanism, and the phalanx support shaft is the slider of the crank-slider mechanism. The middle phalanx, distal phalanx, and phalanx support shaft form another crank-slider mechanism. The phalanx support shaft serves as the mounting base for another crank-slider mechanism, the middle phalanx is the crank of another crank-slider mechanism, and the distal phalanx is the slider of another crank-slider mechanism.

[0009] Both the knuckle support shaft and the knuckle base are U-shaped grooves. One end of the knuckle base is fixed to the palm base, and the other end of the knuckle base is rotatably mounted with a knuckle base bearing. Base grooves are formed along the length of the two side walls of the U-shaped opening near the other end of the knuckle base. One end of the knuckle support shaft is located within the U-shaped opening of the U-shaped knuckle base and is rotatably mounted with a knuckle support shaft near the knuckle pin. The two ends of the knuckle support shaft near the knuckle pin slide within the base grooves on both sides. The other end of the knuckle support shaft is rotatably mounted with a knuckle support shaft far from the knuckle pin. The two side walls of the U-shaped knuckle support shaft near the other end are respectively provided with base grooves along the length of the knuckle base. The distal phalanx is provided with a knuckle support shaft groove. One end of the distal phalanx is located within the U-shaped opening of the U-shaped knuckle support shaft. The distal phalanx is provided with a distal phalanx pin, which slides within the knuckle support shaft grooves on both sides. Both ends of the proximal and middle phalanges are U-shaped. The two side walls of the proximal phalanx end of the U-shape are located outside the knuckle base and are hinged to the knuckle base via the proximal phalanx joint shaft. The two side walls of the other end of the proximal phalanx are located outside the knuckle support shaft and are hinged to the knuckle support shaft via the joint shaft. The two side walls of the middle phalanx end of the U-shape are located outside the knuckle support shaft and are hinged to the knuckle support shaft via the joint shaft. The two side walls of the U-shaped opening at the other end of the middle phalanx are located outside the distal phalanx and are hinged to the distal phalanx via the distal phalanx joint shaft.

[0010] In each group, the other end of the active tendon cord passes through the force sensing module and the palm base, then around the knuckle base bearing and the proximal knuckle guide bearing of the knuckle support shaft, and then around the outside of the knuckle support shaft to the distal knuckle guide bearing of the knuckle support shaft. It then enters the U-shaped opening of the knuckle support shaft and is finally connected to the distal knuckle pin from one side. In each group, the other end of the antagonistic tendon cord passes through the force sensing module and the palm base, then in the opposite direction around the proximal knuckle guide bearing of the knuckle support shaft and enters the U-shaped opening of the knuckle support shaft. Finally, it is connected to the distal knuckle pin from the other side.

[0011] The surfaces of the proximal, middle, and distal phalanges are all fitted with flexible silicone pads to improve gripping contact compliance.

[0012] The hand base includes a base cover, a base bottom, active tendon guide bearings, and antagonistic tendon guide bearings. The base bottom is mounted on the force sensing module, and the base cover is detachably connected to the base bottom. Active tendon guide bearings and antagonistic tendon guide bearings, which are the same number as the active tendons and correspond one-to-one with the antagonistic tendons, are rotatably mounted on the base bottom. In each group, the other end of the active and antagonistic tendons passes through the force sensing module into the hand base, and then enters the bionic finger module through the corresponding active and antagonistic tendon guide bearings.

[0013] The base bottom surface has grooves equal in number to the active tendon guide bearings, and each groove contains a fixed active tendon guide bearing base. The active tendon guide bearings are rotatably mounted on the active tendon guide bearing bases via guide bearing pins. Inside the base bottom, antagonistic tendon guide bearing bases equal in number to the antagonistic tendon guide bearings are installed, and the antagonistic tendon guide bearings are rotatably mounted on the antagonistic tendon guide bearing bases via guide bearing pins. The base bottom also has slotted holes, through which the active tendon guide bearing bases and the antagonistic tendon guide bearing bases are located. The anti-tendon cord guide bearing bases are all inverted U-shapes. The U-shaped openings of each active tendon cord guide bearing base and antagonistic tendon cord guide bearing base are connected to the strip holes, allowing the active and antagonistic tendon cords to pass through. The base cover has notches that correspond one-to-one with the number of bionic finger modules. The bottom of the base has steps corresponding to the positions of each notch. Each bionic finger module is installed in the space formed by the corresponding notch and step. The antagonistic tendon cord guide bearing base is installed on the inner side of the step and is located at the edge of the strip hole.

[0014] Each set of actuators is mounted on a scissor lift platform, through which the pretension of the active and antagonistic tendon cables is adjusted. The base plate of the scissor lift platform is fixed to the external base. Two rotary actuators in each set are fixed to the top of the scissor lift platform via actuator brackets. Each rotary actuator's output end is connected to a single-groove pulley. One end of the active and antagonistic tendon cables in each set is wound around the single-groove pulleys connected to the output ends of the two rotary actuators in the set. One end of the scissor bottom of the scissor lift platform is fixed to the base plate. Symmetrical support plates are provided on the left and right sides of the other end. The support plates on both sides are fixed to the base plate of the lifting platform. Each support plate on both sides has a support plate groove along its length. A movable U-shaped frame is provided between the two support plates. The two sides of the opening of the U-shaped frame are connected to the two support plates by connecting bolts. The connecting bolts are inserted into the support plate grooves on the support plates, pass through the side wall of the opening of the U-shaped frame, and are tightened by connecting nuts. A support is provided on the base plate of the lifting platform. An adjusting bolt is threaded onto the support. The adjusting bolt is fixed to the U-shaped frame. The lifting of the scissor lift platform is achieved by turning the adjusting bolt, thereby adjusting the preload of the active tendon rope and the antagonistic tendon rope.

[0015] The force sensing module includes a sensor base and multiple force detection units installed within the sensor base. The number of force detection units is the same as the total number of active and antagonistic tendons and corresponds one-to-one. Each force detection unit includes a sensor bracket, a sliding bearing, a sliding bearing pin, a slider, a screw, a pressure sensor, a fixed bearing, and a fixed bearing pin. The sensor bracket is fixed inside the sensor base, and the pressure sensor is mounted on the sensor bracket. Two fixed bearings are located on one side of the pressure sensor, and each fixed bearing is fixed to the sensor bracket by its own fixed bearing pin. A detachable slider is located between the two fixed bearings. The slider is U-shaped, with the bottom of the U-shape connected to the pressure sensor by a screw, and a sliding bearing rotatably mounted in the top opening of the U-shape by a sliding bearing pin. The active or antagonistic tendon passes around the lower fixed bearing, then around the other side of the sliding bearing, then exits from the upper fixed bearing, and finally passes through the sensor base.

[0016] The advantages and positive effects of this invention are as follows:

[0017] This invention integrates a rigid-flexible coupling structure with an antagonistic drive principle. It innovatively overcomes the limitations of existing robotic arms, such as their inability to simultaneously grasp fragile and large, rigid objects, and the high energy consumption due to the lack of a self-locking mechanism, by combining a series crank-slider mechanism with an antagonistic tendon system. Based on the transmission characteristics of the series crank-slider mechanism, the robotic arm exhibits rapid closing in the early closing phase and slow movement during precise grasping, enabling more precise force control. This invention achieves good shape adaptation (plates, toys, irregular steel frames) and precise force control, capable of grasping various fragile (eggshells), easily deformable (tofu, paper rolls, balloons), and large, rigid objects (4kg for a single dumbbell, 7.5kg for three fingers). After stabilizing the grasp, this invention can achieve full mechanical self-locking in specific configurations or low-power self-locking using the system's static friction in general configurations; this significantly reduces the energy required to maintain the grasping state, making it particularly suitable for long-term operation or energy-constrained applications in the field. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of the palm base of the present invention after the base cover and base bottom are separated;

[0020] Figure 3 This is a schematic diagram of the structure of the bionic finger module of the present invention;

[0021] Figure 4 This is a schematic diagram of the structure of the driving unit of the present invention;

[0022] Figure 5 This is a schematic diagram of the structural principle of the finger tendon cord winding circuit of the present invention;

[0023] Figure 6 This is a structural schematic diagram of the bionic finger module of the present invention in a specific configuration state;

[0024] Figure 7 This is one of the structural principle diagrams of the bionic finger module of the present invention in a general configuration state;

[0025] Figure 8 This is the second structural schematic diagram of the bionic finger module of the present invention in its general configuration state;

[0026] Figure 9 This is a schematic diagram of the force sensing module of the present invention;

[0027] Wherein: 1 is the palm base, 101 is the base cover, 102 is the base bottom, 103 is the active tendon chord guide bearing, 104 is the active tendon chord guide bearing base, 105 is the guide bearing pin, 106 is the antagonistic tendon chord guide bearing, 107 is the antagonistic tendon chord guide bearing base, 108 is the notch, 109 is the step, and 110 is the strip hole;

[0028] 2 is the bionic finger module; 201 is the proximal phalanx; 202 is the middle phalanx; 203 is the distal phalanx; 204 is the phalanx support shaft; 205 is the phalanx base; 206 is the phalanx support joint shaft; 207 is the proximal phalanx joint shaft; 208 is the distal phalanx joint shaft; 209 is the distal phalanx pin; 210 is the distal phalanx pin of the phalanx support shaft; 211 is the distal phalanx guide bearing of the phalanx support shaft; 212 is the proximal phalanx pin of the phalanx support shaft; 213 is the proximal phalanx guide bearing of the phalanx support shaft; 214 is a flexible silicone pad; 215 is the phalanx support shaft groove; and 216 is the base groove.

[0029] 3 is the drive unit, 301 is the rotary drive, 302 is the single-groove pulley, 303 is the drive bracket, 304 is the scissor lift platform, 305 is the lift platform base plate, 306 is the lift platform plate, 307 is the support, 308 is the adjusting bolt, 309 is the U-shaped frame, 310 is the connecting bolt, 311 is the connecting nut, 312 is the support plate, and 313 is the support plate groove.

[0030] 4 is the tendon cable transmission system, 401 is the active tendon cable, 402 is the antagonistic tendon cable, 403 is the spring, and 404 is the knuckle base bearing;

[0031] 5 is the force sensing module, 501 is the force detection unit, 502 is the sensor base, 503 is the sensor bracket, 504 is the sliding bearing, 505 is the sliding bearing pin, 506 is the slider, 507 is the screw, 508 is the pressure sensor, 509 is the fixed bearing, and 510 is the fixed bearing pin.

[0032] 6 is the control system, 7 is the microcomputer, 8 is the driver controller, and 9 is the data acquisition card. Detailed Implementation

[0033] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] like Figure 1 , Figures 3-5As shown, the present invention includes a hand base 1, a bionic finger module 2, a drive unit 3, a tendon cable transmission system 4, a force sensing module 5, and a control system 6. The hand base 1 is mounted on the force sensing module 5, and multiple bionic finger modules 2 are connected to the hand base 1. Each bionic finger module 2 includes a proximal phalanx 201, a middle phalanx 202, and a distal phalanx 203. The proximal phalanx 201, middle phalanx 202, and distal phalanx 203 form the body of the finger in the form of two crank-slider mechanisms connected in series. The structure of the bionic finger module 2 is designed to mimic the multi-segment bending motion of a mantis's forelimb. The drive unit 3 is mounted on an external base and includes a driver group that corresponds one-to-one with the number of bionic finger modules 2. Each driver group includes two rotating drivers 301 capable of forward and reverse rotation, forming an antagonistic drive mode similar to the skeletal muscles of a human hand. The tendon cable transmission system 4 includes components connected to the bionic finger module 5. The two groups of tendon cords are identical in number and correspond one-to-one. Each group of tendon cords includes one active tendon cord 401 and one antagonistic tendon cord 402. Each active tendon cord 401 and each antagonistic tendon cord 402 is equipped with a spring 403. One end of each active tendon cord 401 and antagonistic tendon cord 402 in each group is connected to the output end of two rotary actuators 301 in the group. The other end of each active tendon cord 401 and antagonistic tendon cord 402 in each group passes through the force sensing module 5 and the palm base 1 and is connected to the corresponding bionic finger module 2. The active tendon cord 401 is driven by the connected rotary actuator 301 to pull the bionic finger module 2 to bend. The antagonistic tendon cord 402 is driven by the connected rotary actuator 301 to pull the bionic finger module 2 to extend and reset or to adjust the stiffness of the bionic finger module 2. The force sensing module 5 and each rotary actuator 301 are connected to the control system 6.

[0035] This embodiment has three bionic finger modules 2. One bionic finger module 2 is located on one side of the palm base 1, and the other two bionic finger modules 2 are located on the opposite side of the palm base 1. These two bionic finger modules 2 can be arranged in parallel or at an angle to each other (i.e., the two bionic finger modules 2 are arranged at a set angle). In this embodiment, the two bionic finger modules 2 located on the opposite side of the palm base 1 are arranged in parallel.

[0036] like Figure 1 , Figure 2As shown, the hand base 1 in this embodiment includes a base cover 101, a base bottom 102, active tendon ligament guide bearings 103 and antagonistic tendon ligament guide bearings 106. Both the base cover 101 and the base bottom 102 are square. The base cover 101 simulates a human hand and provides a supporting plane. The base bottom 102 is used to fix the bionic finger module 2 and is mounted on the force sensing module 5. The base cover 101 is detachably connected to the base bottom 102. Active tendon ligament guide bearings 103 and antagonistic tendon ligament guide bearings 106 are rotatably mounted on the base bottom 102, corresponding to the number of active tendon ligaments 401. The active tendon ligament guide bearings 103 and antagonistic tendon ligament guide bearings 106 are corresponding to the number of antagonistic tendon ligaments 402, respectively, for guiding the active tendon ligaments 401 and antagonistic tendon ligaments 402. The base bottom 102 has grooves on its bottom surface, the same number as the number of active tendon guide bearings 103. Each groove is fixedly fitted with an active tendon guide bearing base 104, and the active tendon guide bearings 103 are rotatably mounted on the active tendon guide bearing base 104 via guide bearing pins 105. Inside the base bottom 102, there are antagonistic tendon guide bearing bases 107, the same number as the antagonistic tendon guide bearings 106. The antagonistic tendon guide bearings 106 are rotatably mounted on the antagonistic tendon guide bearing bases 107 via guide bearing pins 105. The base bottom 102 also has a strip-shaped hole 110. Both the active tendon guide bearing base 104 and the antagonistic tendon guide bearing base 107 are inverted U-shapes. The U-shaped openings of each active tendon guide bearing base 104 and antagonistic tendon guide bearing base 107 are connected to the strip-shaped hole 110, allowing the active tendon 401 and the antagonistic tendon 402 to pass through. The base cover 101 has openings 108, one for each bionic finger module 2, and the same number of openings 108 are provided on each opening 108 on the base bottom 102. Each bionic finger module 2 is installed in the space formed by the corresponding opening 108 and the step 109. The platform of the step 109 has a shaft hole for fixing the bionic finger module 2. The antagonistic tendon guide bearing base 107 is installed on the inner side of the step 109 and is located at the edge of the strip hole 110. The other end of the active tendon 401 and the antagonistic tendon 402 in each group passes through the force sensing module 5 and enters the palm base 1, and then enters the bionic finger module 2 through the corresponding active tendon guide bearing 103 and antagonistic tendon guide bearing 106, respectively.

[0037] In this embodiment, both the base cover 101 and the base bottom 102 are made of epoxy resin material through 3D printing. The antagonistic tendon guide bearing base 107 is made of PLA (polylactic acid) material through 3D printing, and the active tendon guide bearing base 104 is made of aluminum alloy material with higher strength than PLA.

[0038] The bionic finger module 2 in this embodiment also includes a knuckle support shaft 204 and a knuckle base 205. Both the knuckle support shaft 204 and the knuckle base 205 are U-shaped grooves. One end of the knuckle base 205 is fixed in the space formed by the notch 108 and the step 109 on the palm base 1. The other end of the knuckle base 205 is rotatably mounted with a knuckle base bearing 404. Base grooves 216 are respectively opened along the length direction on the two side walls of the U-shaped opening near the other end of the knuckle base 205. One end of the knuckle support shaft 204 is located in the U-shaped opening of the U-shaped knuckle base 205 and is rotatably mounted with a knuckle support shaft near knuckle pin 212. The two ends of the knuckle support shaft near knuckle pin 212 slide in the base grooves 216 on both sides respectively. The other end of the knuckle support shaft 204 is rotatably mounted with a knuckle support shaft far knuckle pin 210. Knuckle support shaft grooves 215 are respectively opened along the length direction on the two side walls of the U-shaped knuckle support shaft 204 near the other end. One end of the distal knuckle 203 is located in the U-shaped opening of the U-shaped knuckle support shaft 204 and is provided with a distal knuckle pin 209, which slides in the knuckle support shaft grooves 215 on both sides. Both ends of the proximal phalanx 201 and the middle phalanx 202 are U-shaped. The two side walls of one end of the U-shaped proximal phalanx 201 are located outside the phalanx base 205 and are hinged to the phalanx base 205 via the proximal phalanx joint axis 207. The two side walls of the other end of the U-shaped proximal phalanx 201 are located outside the phalanx support axis 204 and are hinged to the phalanx support axis 204 via the joint axis 206. The two side walls of one end of the U-shaped middle phalanx 202 are located outside the phalanx support axis 204 and are hinged to the phalanx support axis 204 via the joint axis 206. The two side walls of the other end of the U-shaped middle phalanx 202 are located outside the distal phalanx 203 and are hinged to the distal phalanx 203 via the distal phalanx joint axis 208. In this embodiment, the length of the phalanx support axis groove 215 can be 42 mm, and the length of the base groove 216 can be 36 mm.

[0039] In this embodiment, the proximal phalanx 201, phalanx base 205, and phalanx support shaft 204 form a crank-slider mechanism. The phalanx base 205 serves as the mounting base for one crank-slider mechanism, the proximal phalanx 201 is the crank of one crank-slider mechanism, and the phalanx support shaft 204 is the slider of one crank-slider mechanism. The middle phalanx 202, distal phalanx 203, and phalanx support shaft 204 form another crank-slider mechanism. The phalanx support shaft 204 serves as the mounting base for another crank-slider mechanism, the middle phalanx 202 is the crank of another crank-slider mechanism, and the distal phalanx 203 is the slider of another crank-slider mechanism. The phalanx support shaft 204 serves as both the slider of the first crank-slider mechanism and the mounting base of the second crank-slider mechanism, thus forming two tandem crank-slider mechanisms. The tandem crank-slider mechanisms constitute the body of the bionic finger module 2, converting the linear tension of the tendons into the sliding tension of the pins, and further into the joint torque of the phalanges. This tandem crank-slider mechanism can adaptively adjust the bending angle and output force of each joint according to the shape and stiffness of the object during the gripping process.

[0040] Series crank-slider mechanisms in specific configurations (such as...) Figure 6 As shown, complete self-locking can be achieved under certain conditions, and low-power self-locking can be achieved under general configuration. For the specific configuration of complete self-locking, complete self-locking is achieved when the force is applied vertically downwards to the distal phalanx 203, and the line of action of the force passes perpendicularly through the distal phalanx joint axis 208 while being tangent to the inner end of the phalanx support axis near the phalanx guide bearing 213. At this time, the angle between the phalanx support axis 204 and the sliding symmetry center of the phalanx base 205 is θ0. In practical applications, due to structural limitations, the line of action of the external force cannot pass through the distal phalanx joint axis 208. Assuming the angle between the line of action of the external force and the axis of the distal phalanx 203 is θ... F When the distance between the line of action of the external force and the axis 208 of the distal phalanx joint is within L0, the external force F can be borne by static friction f through the lever principle. Specifically, the maximum self-locking force F that can be borne is... max-lock With θ F L0 and f are related. In a fully self-locking configuration, the bionic finger module 2 can withstand a maximum force of nearly 40N by relying on the static friction of the structure itself. For a general configuration, the distance between the line of action of the external force and the axis of the distal phalanx joint 208 is within L0. When the distance L between the line of action of the external force and the axis of the phalanx support shaft near the phalanx guide bearing 213 is greater than its radius, the angle θ between the phalanx support shaft 204 and the center of symmetry of the U-shaped groove of the phalanx base 205 is less than θ0, which can achieve low-power self-locking. The bionic finger module 2 can withstand a force of nearly 40N with a force of 2-8N, such as Figure 7 As shown. An angle θ greater than θ0 can also achieve low-power self-locking, but the energy consumption is greater than in the case where the angle θ is less than θ0, but still less than the applied force, as... Figure 8 As shown.

[0041] In this embodiment, the proximal phalanx 201, middle phalanx 202, and distal phalanx 203 are all made of epoxy resin material through 3D printing. The phalanx support shaft 204 is cut from a U-shaped groove made of high-strength, easy-to-process, and lightweight aluminum alloy material. Flexible silicone pads 214 are installed on the surfaces of the proximal phalanx 201, middle phalanx 202, and distal phalanx 203 to improve the flexibility of gripping contact.

[0042] In this embodiment, the distal phalanx 203 is designed with a spherical arc surface that mimics the human hand to increase the contact surface, and multiple hollow parts 217 are provided on the back to reduce material consumption and the weight of the phalanx.

[0043] The bionic finger module 2 in this embodiment has a range of motion that encompasses the functional range of motion of a human hand. Furthermore, due to the characteristics of the crank-slider mechanism, the bionic finger module 2 moves relatively quickly in the early stages of closure, which matches the closing motion characteristics of a human hand. During precise grasping, the knuckle movements are slower than the early closing movements, which helps in the precise control of the grasping force.

[0044] like Figure 1 , Figure 4As shown, in this embodiment, each set of actuators is installed on a scissor lift platform 304. The preload of the active tendon rope 401 and the antagonistic tendon rope 402 is adjusted through the scissor lift platform 304. The lifting platform base plate 305 at the bottom of the scissor lift platform 304 is fixed to the external base. The two rotary actuators 301 of each set of actuators are fixed to the lifting platform plate 306 at the top of the scissor lift platform 304 through the actuator bracket 303. The output end of each rotary actuator 301 is connected to a single groove pulley 302. One end of the active tendon rope 401 and the antagonistic tendon rope 402 in each set of tendon ropes is wound around the single groove pulley 302 connected to the output ends of the two rotary actuators 301 in the set. One end of the scissor lift platform 304 is fixed to the lifting platform base plate 305. The other end of the scissor lift platform 304 has symmetrical support plates 312 on the left and right sides. The two support plates 312 are fixed to the lifting platform base plate 305 respectively. Each support plate 312 has a support plate groove 313 along the length direction. A movable U-shaped frame 309 is provided between the two support plates 312. The two sides of the opening of the U-shaped frame 309 are connected to the two support plates 312 by connecting bolts 310. The connecting bolts 310 are inserted into the support plate groove 313 on the support plate 312, pass through the side wall of the opening of the U-shaped frame 309, and are tightened by connecting nuts 311. A support 307 is provided on the base plate 305 of the lifting platform. An adjusting bolt 308 is threaded onto the support 307. The adjusting bolt 308 is fixedly connected to the U-shaped frame 309. The lifting and lowering of the scissor lift platform 304 is achieved by turning the adjusting bolt 308, thereby adjusting the preload of the active tendon cable 401 and the antagonistic tendon cable 402. The rotary actuator 301 can be a servo motor or a servo motor. It drives the series crank-slider mechanism to move by coordinating the release and retraction of the active tendon cable 401 and the antagonistic tendon cable 402, thereby causing the finger joints to produce coupled bending or extension movements. In this embodiment, the rotary actuator 301 is a servo motor with a maximum load torque of not less than 20 kg·cm. Specifically, the rotary actuator 301 can be a servo motor from Shenzhen Huaner Technology Co., Ltd., model LX 224HV.

[0045] The tendon cable transmission system 4 of this embodiment includes three sets of tendon cables, namely three active tendon cables 401 and three antagonistic tendon cables 402. In each set, one end of the active tendon cable 401 and the antagonistic tendon cable 402 are respectively connected to one end of two springs 403. The other ends of the two springs 403 are then wound around the single-groove pulleys 302 connected to the output ends of the two rotary actuators 301 in each set via tendon cables. The springs 403 are used to improve the compliance with the object during gripping. The active tendon cables 401 and the antagonistic tendon cables 402 can use springs 403 with different stiffnesses. In each group, the other end of the active tendon cord 401 passes through the force sensing module 5 and the corresponding active tendon cord guide bearing 103 on the palm base 1, and then enters the bionic finger module 2. It bypasses the knuckle base bearing 404 and the proximal knuckle guide bearing 213 of the knuckle support shaft, and then goes around the outside of the knuckle support shaft 204 to the distal knuckle guide bearing 211 of the knuckle support shaft. It then enters the U-shaped opening of the knuckle support shaft 204 and is finally connected to the distal knuckle pin 209 from one side. In each group, the other end of the antagonistic tendon cord 402 passes through the force sensing module 5 and the corresponding antagonistic tendon cord guide bearing 106 on the palm base 1, and then enters the bionic finger module 2. It then goes around the proximal knuckle guide bearing 213 of the knuckle support shaft in the opposite direction and enters the U-shaped opening of the knuckle support shaft 204. Finally, it is connected to the distal knuckle pin 209 from the other side. Therefore, the end of the antagonistic tendon cord 402 can directly antagonize and regulate the force exerted on the fingertip of the distal knuckle 203.

[0046] In this embodiment, the active tendon cord 401 is responsible for pulling the bionic finger module 2 to bend, while the antagonistic tendon cord 402 is responsible for pulling the bionic finger module 2 to extend and return to its original position or for adjusting the stiffness of the bionic finger module 2. This constitutes an antagonistic drive mode of the human hand's skeletal muscles, facilitating the adjustment of fingertip force to adapt to the grasping of objects with different characteristics. The movement of the flexible tendon cord, through the aforementioned transmission circuit, drives the crank-slider mechanism, further driving the rotational movement of the rigid knuckles for precise or enveloping grasping of objects. In this rigid-flexible coupling structure formed by the tendon cord and the rigid knuckles, the flexible transmission provides the robotic hand with better compliance, while the structure formed by the rigid knuckles enhances the stiffness of the bionic finger module 2, helping to increase the load capacity of the robotic hand. The rigid knuckles driven by the crank-slider mechanism are similar to a reinforced skeleton, relying on the structural stability brought by static friction to provide the bionic finger module 2 with self-locking capability and reduce motor power consumption. In this embodiment, both the active tendon cord 401 and the antagonistic tendon cord 402 are made of braided polyethylene thread with a breaking strength of 735 N, which can maintain sufficient flexibility while ensuring strength. The active tendon 401, antagonistic tendon 402, and spring 403 increase the flexibility of the robotic hand, making it more adaptable to grasping fragile and deformable objects.

[0047] like Figure 1 , Figure 9As shown, the force sensing module 5 in this embodiment includes a sensor base 502 and multiple force detection units 501 installed within the sensor base 502. The base bottom 102 in the palm base 1 is mounted on the sensor base 502. The number of force detection units 501 is the same as the total number of active tendon tractors 401 and antagonistic tendon tractors 402, and they correspond one-to-one. The force detection unit 501 includes a sensor bracket 503, a sliding bearing 504, a sliding bearing pin 505, a slider 506, a screw 507, a pressure sensor 508, a fixed bearing 509, and a fixed bearing pin 510. The sensor bracket 503 is fixed within the sensor base 502, and the pressure sensor 508... The pressure sensor 508 is mounted on a sensor bracket 503. Two fixed bearings 509 are located on one side of the pressure sensor 508, one above the other. Each fixed bearing 509 is fixed to the sensor bracket 503 via its respective fixed bearing pin 510. A detachable slider 506 is located between the two fixed bearings 509. The slider 506 is U-shaped, and a sliding bearing 504 is rotatably mounted inside the opening at the top of the U-shape via a sliding bearing pin 505. When installing the sliding bearing 504, the slider 506 is slid into a groove on the sensor bracket 503 and positioned between the two fixed bearings 509. Then, the bottom of the U-shape is connected to the pressure sensor 508 via screws 507. The active tendon 401 or antagonistic tendon 402 passes around one side of the lower fixed bearing 509, then around the other side of the sliding bearing 504, then exits from one side of the upper fixed bearing 509, and finally passes through the sensor base 502. The pressure sensor 508 can detect the tension of the active tendon 401 and antagonistic tendon 402 in real time.

[0048] The control system 6 in this embodiment is existing technology, including a microcomputer 7, a driver controller 8, and a data acquisition card 9. The control system 6 estimates the fingertip and joint torque of the bionic finger module 2 based on the data of the active tendon 401 and the antagonistic tendon 402 fed back by the pressure sensor 508, and further coordinates the control of the rotary driver 301 according to the characteristics of different objects to control the movement of the robotic hand and realize force feedback control.

[0049] The tendon-wire transmission in this embodiment offers flexibility by separating the drive unit 3 from the manipulator body module. The manipulator body module integrates the force sensing module 5, the hand base 1, and the bionic finger module 2, and can be integrated into the end effector of a general-purpose robotic arm via a flange. The entire manipulator adopts a modular design, facilitating functional expansion or component replacement according to different application scenarios.

[0050] The working principle of this invention is as follows:

[0051] The robotic hand of this invention can be used as a general-purpose robot end effector. It employs a hybrid rigid-flexible bionic robotic hand design in conjunction with an antagonistic drive system. The rotary actuator 301, through the coordinated retraction and extension of the active tendon cable 401 and the antagonistic tendon cable 402, drives the tandem crank-slider mechanism, thereby causing coupled bending or extension movements in each finger joint to achieve envelope grasping or pinching of the target object. Specifically:

[0052] When it is necessary to grasp an object, the control system 6 sends a control command to the rotary actuator 301, which drives the single-groove pulley 302 to retract the active tendon rope 401 and release the antagonistic tendon rope 402. The tension of the active tendon cord 401 is transmitted through the spring 403 and the force detection unit 501 to the crank-slider mechanism formed by the knuckle base 205, proximal knuckle 201, and knuckle support shaft 204. This drives the proximal knuckle pin 212 of the knuckle support shaft to slide, further causing the knuckle support shaft 204 to begin bending. The torque is transmitted sequentially, causing the proximal knuckle 201 and middle knuckle 202 to bend successively. This movement phase enables motion closure and precise grasping configuration. When there is no object contact, after the crank-slider mechanism formed by the knuckle base 205, proximal knuckle 201, and knuckle support shaft 204 moves to the limit, the active tendon cord 401 continues to act on the crank-slider mechanism formed by the knuckle support shaft 204, middle knuckle 202, and distal knuckle 203, driving the distal knuckle pin 209 to slide and causing the distal knuckle 203 to bend, thus achieving adaptive envelope grasping of the object.

[0053] When grasping fragile items, the control system 6, through coordinated control of the rotary actuator 301, the active tendon cord 401, and the antagonistic tendon cord 402 acting directly on the distal phalanx pin 209, can control the fingertip to apply a small force through antagonistic action, achieving a gentle and precise grasp. When grasping heavy, rigid items, based on the stability characteristics of the crank-slider mechanism and the amplification effect of the lever mechanism, it can bear an item weighing 7.5 kg. In a specific configuration (the line of force acts vertically downward through the distal phalanx pin 209 and the proximal phalanx pin 212 of the phalanx support shaft), the mechanism achieves complete self-locking, and even if the power of the rotary actuator 301 is removed, the finger configuration can still withstand a force of nearly 40 N. In a general configuration (the line of force acts vertically downward through the distal phalanx pin 209 and to the right of the proximal phalanx pin 212 of the phalanx support shaft), the system relies on the static friction between the tendon cord and the U-groove, as well as the internal friction of the mechanism, to achieve low-power self-locking. In this case, only a very small driving force is required to maintain the grasp, significantly reducing energy consumption.

[0054] When the object needs to be released, the rotary actuator 301 rotates in the opposite direction, retracting the antagonistic tendon 402 and releasing the active tendon 401, and the phalanges of the bionic finger module 2 extend in sequence, returning to the open state.

[0055] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A biomimetic rigid-flexible coupling underactuated manipulator, characterized in that: The system includes a hand base (1), a bionic finger module (2), a drive unit (3), a tendon cable transmission system (4), a force sensing module (5), and a control system (6). The hand base (1) is mounted on the force sensing module (5), and multiple bionic finger modules (2) are connected to the hand base (1). Each bionic finger module (2) includes a proximal phalanx (201), a middle phalanx (202), and a distal phalanx (203). The proximal phalanx (201), middle phalanx (202), and distal phalanx (203) form the body of the finger in the form of two crank-slider mechanisms connected in series. The drive unit (3) is mounted on an external base and includes a set of actuators that are the same number as the number of bionic finger modules (2) and correspond one-to-one. Each set of actuators includes two rotary actuators (301) that can rotate in both directions. The tendon cable transmission system (4) includes a set of tendon cables that are the same number as the number of bionic finger modules (2) and correspond one-to-one. Each set of tendon cables includes one tendon cable. An active tendon cord (401) and an antagonistic tendon cord (402) are provided, each of which is equipped with a spring (403). One end of each active tendon cord (401) and antagonistic tendon cord (402) in each group is connected to the output ends of two rotary actuators (301) in the group. The other end of each active tendon cord (401) and antagonistic tendon cord (402) in each group passes through a force sensing module (5) and a palm base (5), respectively. 1) It is then connected to the corresponding bionic finger module (2). The active tendon (401) is driven by the connected rotary driver (301) to pull the bionic finger module (2) to bend. The antagonistic tendon (402) is driven by the connected rotary driver (301) to pull the bionic finger module (2) to extend and reset or to adjust the stiffness of the bionic finger module (2). The force sensing module (5) and each rotary driver (301) are respectively connected to the control system (6). The bionic finger module (2) further includes a knuckle support shaft (204) and a knuckle base (205). Both the knuckle support shaft (204) and the knuckle base (205) are U-shaped grooves. One end of the knuckle base (205) is fixed to the palm base (1), and the other end of the knuckle base (205) is rotatably mounted with a knuckle base bearing (404). The two side walls of the U-shaped opening near the other end of the knuckle base (205) are respectively provided with base grooves (216) along the length direction. One end of the knuckle support shaft (204) is located in the U-shape. A finger support shaft near-finger guide bearing (213) is rotatably mounted in the U-shaped opening of the groove-shaped finger base (205) and via the finger support shaft near-finger pin (212). The two ends of the finger support shaft near-finger pin (212) slide in the base grooves (216) on both sides respectively. The other end of the finger support shaft (204) is rotatably mounted with a finger support shaft far-finger guide bearing (211) via the finger support shaft far-finger pin (210). Along the length direction, the two side walls of the U-shaped groove-shaped finger support shaft (204) near the other end are... Each finger joint support shaft has a sliding groove (215). One end of the distal phalanx (203) is located in the U-shaped opening of the U-shaped groove finger joint support shaft (204). One end of the distal phalanx (203) is provided with a distal phalanx pin (209), which slides in the finger joint support shaft sliding grooves (215) on both sides. Both ends of the proximal phalanx (201) and the middle phalanx (202) are U-shaped. The two side walls of the proximal phalanx (201) end are located outside the phalanx base (205) and are connected to the phalanx through the proximal phalanx joint shaft (207). The base (205) is hinged, and the two side walls of the other end of the proximal phalanx (201) of the U-shape are located outside the phalanx support shaft (204) and are hinged to the phalanx support shaft (204) through the joint shaft (206); the two side walls of one end of the middle phalanx (202) of the U-shape are located outside the phalanx support shaft (204) and are hinged to the phalanx support shaft (204) through the joint shaft (206); the two side walls of the other end of the middle phalanx (202) of the U-shape are located outside the distal phalanx (203) and are hinged to the distal phalanx (203) through the distal phalanx joint shaft (208); The other end of the active tendon cord (401) in each group passes through the force sensing module (5) and the palm base (1), then goes around the knuckle base bearing (404) and the knuckle support shaft proximal knuckle guide bearing (213), and goes around the outside of the knuckle support shaft (204) to the knuckle support shaft distal knuckle guide bearing (211), and then enters the U-shaped opening of the knuckle support shaft (204), and is finally connected to the distal knuckle pin (209) from one side; the other end of the antagonistic tendon cord (402) in each group passes through the force sensing module (5) and the palm base (1), then goes around the knuckle support shaft proximal knuckle guide bearing (213) in the opposite direction and enters the U-shaped opening of the knuckle support shaft (204), and is finally connected to the distal knuckle pin (209) from the other side.

2. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 1, characterized in that: The knuckle base (205) is mounted on the palm base (1). The knuckle support shaft (204) is slidably connected to the knuckle base (205). The distal knuckle (203) is slidably connected to the knuckle support shaft (204). The two ends of the proximal knuckle (201) are respectively hinged to the knuckle base (205) and the knuckle support shaft (204). The two ends of the middle knuckle (202) are respectively hinged to the knuckle support shaft (204) and the distal knuckle (203).

3. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 2, characterized in that: The proximal knuckle (201), knuckle base (205), and knuckle support shaft (204) form a crank-slider mechanism. The knuckle base (205) is the mounting base for the crank-slider mechanism. The proximal knuckle (201) is the crank of the crank-slider mechanism. The knuckle support shaft (204) is the slider of the crank-slider mechanism. The middle knuckle (202), distal knuckle (203), and knuckle support shaft (204) form another crank-slider mechanism. The knuckle support shaft (204) is the mounting base for another crank-slider mechanism. The middle knuckle (202) is the crank of another crank-slider mechanism. The distal knuckle (203) is the slider of another crank-slider mechanism.

4. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 1, characterized in that: The surfaces of the proximal phalanx (201), middle phalanx (202), and distal phalanx (203) are all fitted with flexible silicone pads (214) to improve gripping contact compliance.

5. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 1, characterized in that: The hand base (1) includes a base cover (101), a base bottom (102), an active tendon guide bearing (103), and an antagonistic tendon guide bearing (106). The base bottom (102) is mounted on the force sensing module (5). The base cover (101) is detachably connected to the base bottom (102). The base bottom (102) is rotatably mounted with active tendon guide bearings (103) that are the same number as the active tendon (401) and antagonistic tendon guide bearings (106) that are the same number as the antagonistic tendon (402). In each group, the other end of the active tendon (401) and antagonistic tendon (402) passes through the force sensing module (5) and enters the hand base (1), and then enters the bionic finger module (2) through the corresponding active tendon guide bearing (103) and antagonistic tendon guide bearing (106).

6. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 5, characterized in that: The bottom surface of the base (102) has grooves of the same number as the active tendon guide bearings (103), and each groove is fixedly connected to an active tendon guide bearing base (104). The active tendon guide bearings (103) are rotatably mounted on the active tendon guide bearing bases (104) via guide bearing pins (105). The bottom of the base (102) has antagonistic tendon guide bearing bases (107) of the same number as the antagonistic tendon guide bearings (106), and the antagonistic tendon guide bearings (106) are rotatably mounted on the antagonistic tendon guide bearing bases (107) via guide bearing pins (105). The bottom of the base (102) also has a strip hole (110), and the active tendon guide bearing bases (104) and the antagonistic tendon guide shafts are connected to each other. The base (107) is inverted U-shape. The U-shaped openings of each active tendon guide bearing base (104) and antagonistic tendon guide bearing base (107) are connected to the strip hole (110) for the active tendon (401) and antagonistic tendon (402) to pass through. The base cover (101) is provided with notches (108) that are the same number as the number of bionic finger modules (2) and correspond one-to-one. The base bottom (102) is provided with steps (109) corresponding to the positions of each notch (108). Each bionic finger module (2) is installed in the space formed by the corresponding notch (108) and step (109). The antagonistic tendon guide bearing base (107) is installed on the inner side of the step (109) and is located at the edge of the strip hole (110).

7. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 1, characterized in that: Each set of the drive units is mounted on a scissor lift platform (304), through which the preload of the active tendon cable (401) and the antagonistic tendon cable (402) is adjusted; the lifting platform base plate (305) at the bottom of the scissor lift platform (304) is fixed to the external base, and the two rotary drives (301) of each set of the drive units are respectively fixed to the lifting platform plate (306) at the top of the scissor lift platform (304) through drive brackets (303). The output ends of the rotary actuators (301) are respectively connected to single-groove pulleys (302). In each group of tendon cords, one end of the active tendon cord (401) and the antagonistic tendon cord (402) are respectively wound around the single-groove pulleys (302) connected to the output ends of the two rotary actuators (301) in the group; one end of the bottom of the scissor lift platform (304) is fixed to the lift platform base plate (305), and the other end of the bottom of the scissor lift platform (304) is symmetrically provided with support plates on the left and right sides. 312), the two side support plates (312) are respectively fixed on the lifting platform base plate (305), and each side support plate (312) is provided with a support plate groove (313) along the length direction. A movable U-shaped frame (309) is provided between the two side support plates (312). The two sides of the opening of the U-shaped frame (309) are respectively connected to the two side support plates (312) by connecting bolts (310). The connecting bolts (310) are connected by the support plate grooves (313) on the support plates (312). After being inserted through the side wall of the opening of the U-shaped frame (309), it is tightened by the connecting nut (311); the base plate (305) of the lifting platform is provided with a support (307), and the support (307) is threaded with an adjusting bolt (308). The adjusting bolt (308) is fixedly connected to the U-shaped frame (309). The lifting of the scissor lift platform (304) is realized by turning the adjusting bolt (308), thereby adjusting the preload of the active tendon rope (401) and the antagonistic tendon rope (402).

8. The biomimetic rigid-flexible coupling underactuated manipulator according to claim 1, characterized in that: The force sensing module (5) includes a sensor base (502) and multiple force detection units (501) installed in the sensor base (502). The number of force detection units (501) is the same as the total number of active tendon cords (401) and antagonistic tendon cords (402), and they correspond one-to-one. Each force detection unit (501) includes a sensor bracket (503), a sliding bearing (504), a sliding bearing pin (505), a slider (506), a screw (507), a pressure sensor (508), a fixed bearing (509), and a fixed bearing pin (510). The sensor bracket (503) is fixed in the sensor base (502), and the pressure sensor (508) is installed on the sensor bracket (503). The pressure sensor (508) has a top and bottom edge on one side. Two fixed bearings (509) are fixed to the sensor bracket (503) by their respective fixed bearing pins (510). A detachable slider (506) is provided between the two fixed bearings (509). The slider (506) is U-shaped. The bottom of the U-shape is connected to the pressure sensor (508) by screws (507). A sliding bearing (504) is rotatably installed in the top opening of the U-shape by a sliding bearing pin (505). The active tendon (401) or antagonistic tendon (402) passes around one side of the lower fixed bearing (509), then around the other side of the sliding bearing (504), then out through one side of the upper fixed bearing (509), and finally out through the sensor base (502).

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