Two-finger force-controlled underactuated manipulator based on differential connecting rod sliding

Abstract

The application discloses a two-finger force control underactuated manipulator based on differential connecting rod sliding, and relates to the technical field of manipulators.The two-finger force control underactuated manipulator comprises a supporting frame, a telescopic mechanism installed at one end of the supporting frame, and two clamping mechanisms which are slidably connected to the other end of the supporting frame.The clamping mechanism comprises a translation connecting rod and a clamping arm;the clamping arm is integrated with a force measuring unit;the underactuated grabbing mechanism comprises a crossbeam and two slider connecting rod assemblies which are slidably connected to the crossbeam;the crossbeam is rotatably connected to a telescopic rod of the telescopic mechanism;torsional springs are installed between the telescopic rod and the crossbeam;one end of the slider connecting rod assembly is slidably connected to the crossbeam, and the other end of the slider connecting rod assembly is hingedly connected to the translation connecting rod and the inner side wall of the supporting frame;the crossbeam, the slider connecting rod assembly and the translation connecting rod are matched with each other in a skillful manner, so that the vertical movement of the telescopic mechanism is converted into horizontal grabbing movement of the clamping arm;under the driving of a single telescopic mechanism, the shape and size of a part to be grabbed can be automatically adapted; and the force measuring unit is used to realize accurate force control of the manipulator under different grabbing force ranges.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical hands, and more particularly to a two-finger force control underactuated mechanical hand based on differential connecting rod sliding. BACKGROUND

[0002] An underactuated mechanical hand refers to a special mechanical hand in which the number of required driving motors is less than the number of degrees of freedom of the grasping mechanism. Compared with a traditional fully actuated mechanical hand (in which the number of motors is equal to the number of degrees of freedom of the grasping mechanism), an underactuated mechanical hand has a simple structure, and the number of driving components is greatly reduced because the number of required motors is less than that of a fully actuated mechanical hand. Therefore, the underactuated mechanical hand has a smaller volume and a smaller weight, and consumes less energy. The underactuated mechanical hand has a very wide range of applications and can be used in industrial automation, space exploration, medical surgery, agricultural picking, and other fields. For example, the underactuated mechanical hand can be equipped with various tools and sensors to complete operations in dangerous environments. In addition, the underactuated mechanical hand can adapt to different shapes, materials, and position deviations of parts, thereby reducing the grasping difficulty of the mechanical hand and improving the operability of the mechanical hand. At present, the underactuated mechanical hand is developing towards intelligence, miniaturization, high flexibility, and precision, and is one of the important development directions in the field of future intelligent robots.

[0003] Although the number of motors of the underactuated mechanical hand is greatly reduced compared with the fully actuated mechanical hand, most underactuated mechanical hands still use two to five motors, so the cost of the mechanical hand is still high. Using a single motor to drive can greatly reduce the cost and control complexity of the mechanical hand, but the mechanical structure of the existing single-drive underactuated mechanical hand is too complex, and a heavy transmission mechanism such as a gear and a rack is usually used as a differential mechanism, thereby causing the mechanical hand to be large and heavy, and making its maintenance very difficult. In addition, although the use of a differential mechanism based on a rope and a pulley can reduce the volume and weight of the underactuated mechanical hand, the grasping force of this driving method is usually small, so it cannot carry heavy or large objects, which limits its wide application in industrial production. The underactuated mechanical hand based on the connecting rod differential mechanism has the advantages of compactness, lightness, and large grasping force. However, the existing connecting rod differential mechanism has a small movement range, which easily leads to a limited grasping range of the mechanical hand.

[0004] In addition, because the underactuated mechanical hand has multiple passive degrees of freedom (i.e., the movement of the grasping mechanism of the mechanical hand is not controlled), the position control of the mechanical hand cannot be performed, and the mechanical hand can only passively adapt to the shape or position of the object, so it can only be force-controlled, i.e., the grasping force after the final stable grasping is controlled to avoid the grasping force being too large or too small. However, the existing force sensor cannot accurately measure a small grasping force and a large grasping force at the same time, mainly because the range and the accuracy of the force sensor are contradictory, i.e., the larger / smaller the range, the lower / higher the accuracy.

[0005] Therefore, how to provide a simple structure, which can realize automatic adaptation to the shape and size of the grabbed parts under the driving of a single motor, and can be used for measuring different range of gripping force by an under-actuated manipulator is an urgent problem for those skilled in the art. SUMMARY

[0006] Therefore, the application provides a two-finger force-controlled under-actuated manipulator based on differential link sliding, aiming to solve the above technical problems.

[0007] In order to achieve the above purpose, the application adopts the following technical solutions:

[0008] A two-finger force-controlled under-actuated manipulator based on differential link sliding comprises:

[0009] A support frame is provided with a telescopic mechanism; two clamping mechanisms are slidably connected to the end of the support frame away from the telescopic mechanism; the clamping mechanism comprises a translational link slidably connected to the support frame and a clamping arm fixedly connected to one end of the translational link;

[0010] An under-actuated gripping mechanism comprises a crossbeam and two slider link assemblies slidably connected to the crossbeam; the crossbeam is located on the inner side of the support frame and is rotatably connected to the telescopic rod of the telescopic mechanism; a torsional spring is installed between the telescopic rod and the crossbeam; one end of the slider link assembly is slidably connected to the crossbeam, and the other end is hingedly connected to the translational link and the inner side wall of the support frame;

[0011] A force measuring unit is integrated on the inner side of the clamping arm.

[0012] Through the above technical solutions, the two-finger force-controlled under-actuated manipulator based on differential link sliding provided by the application outputs displacement through the telescopic mechanism, the crossbeam synchronously drives the slider link mechanism on both sides to move, and then drives the two translational links to synchronously move, thereby realizing the clamping and gripping action; meanwhile, a torsional spring is installed between the crossbeam and the telescopic rod, the setting of the torsional spring can constrain the rotation between the crossbeam and the telescopic rod, when the displacements on both sides of the crossbeam are the same, the crossbeam does not rotate, when the displacements on both sides of the crossbeam are different, the crossbeam rotates, so as to adapt to the difference between the displacements on both sides; the stable operation of the overall structure is ensured; the application has a simple structure and can realize the clamping of parts with different sizes and shapes; meanwhile, force measuring units are integrated on the inner sides of the two clamping arms, thereby realizing the measurement of the gripping force of the clamping arms.

[0013] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, an opening is formed at the end of the support frame away from the telescopic mechanism, and a fixed slider is fixed at both ends of the opening, and the translational link is slidably connected to the inner side of the fixed slider. A moving pair is formed between the translational link and the fixed slider.

[0014] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, the slider link assembly comprises a movable slider, a first link and a second link; the movable slider is slidably connected to the cross beam, one end of the first link is hingedly connected to the top surface of the movable slider, and the other end is hingedly connected to the translational link; one end of the second link is hingedly connected to the bottom surface of the movable slider, and the other end is hingedly connected to the support frame. A rocker slider mechanism is formed between the first link, the second link, the translational link and the fixed slider, and the clever cooperation of the cross beam and the rocker slider mechanism converts the vertical movement of the telescopic mechanism into the horizontal grabbing movement of the clamping arm; The technical problems of the prior art, such as complex structure, large size and complicated operation process, are solved.

[0015] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, the clamping arm comprises a first flexible beam and a second flexible beam, and the end of the first flexible beam is fixed with a clamping finger; one end of the second flexible beam is fixedly connected with the end of the first flexible beam away from the clamping finger, and the other end is fixedly connected with the translational link.

[0016] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, the thickness of the first flexible beam is smaller than the thickness of the second flexible beam.

[0017] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, a first support is fixed to the outer side of the first flexible beam, a first gap is formed between one end of the first support and the first flexible beam, and the other end is fixedly connected with the first flexible beam; a second support is fixed to the outer side of the second flexible beam, a second gap is formed between one end of the second support and the second flexible beam, and the other end is fixedly connected with the translational link.

[0018] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, the force measuring unit comprises a first strain gauge and a second strain gauge; the first strain gauge is installed on the inner side of the first flexible beam; and the second strain gauge is installed on the inner side of the second flexible beam.

[0019] Preferably, in the two-finger force-controlled underactuated manipulator based on differential link sliding, the clamping end surface of the clamping finger is V-shaped. The V-shaped arrangement can ensure stable grabbing of the object and prevent the object from slipping off the finger during grabbing.

[0020] Preferably, in the two-finger force-controlled underactuated manipulator based on differential connecting rod sliding, a displacement sensor is further included; the displacement sensor comprises a sensor shell and a sensor core; the sensor shell is fixed on the support frame, one end of the sensor core is in sliding connection with the sensor shell, and the other end extends to the outside of the sensor shell and is fixedly connected with the second support frame. The displacement sensor is a linear displacement sensor for detecting the displacement of the gripping fingers.

[0021] Preferably, in the two-finger force-controlled underactuated manipulator based on differential connecting rod sliding, the telescopic mechanism is a linear motor. The telescopic mechanism can also adopt other structures to realize the telescopic movement of the telescopic rod to drive the displacement of the moving block on the cross beam.

[0022] According to the technical scheme, compared with the prior art, the two-finger force-controlled underactuated manipulator based on differential connecting rod sliding has the following beneficial effects:

[0023] 1. The first connecting rod, the second connecting rod, the translating connecting rod and the fixed block form a rocker block mechanism, the rocker block mechanism and the cross beam are matched with each other, the vertical movement of the linear motor is converted into horizontal grabbing movement for driving the gripping fingers, a single linear motor is used to drive the manipulator, the shape and size of the grabbed part are automatically adapted, the structure is simple, and the operation is convenient.

[0024] 2. The telescopic rod and the cross beam are connected in a rotary joint mode, and a torsional spring is arranged between the telescopic rod and the cross beam, the connecting mode forms a two-degree-of-freedom connecting rod differential mode, the vertical movement is the active degree of freedom and is directly driven by the linear motor, and the rotation is the passive degree of freedom; the torsional spring restricts the rotation between the cross beam and the telescopic rod, when the displacements on both sides of the cross beam are the same, the cross beam does not rotate, and when the displacements on both sides are different, the cross beam rotates to adapt to the difference between the displacements on both sides.

[0025] 3. The two-stage force measuring unit can realize accurate force control of the manipulator in different grabbing force ranges. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only embodiments of the present application, and other accompanying drawings can be obtained by those skilled in the art without creative labor on the basis of the provided accompanying drawings.

[0027] Figure 1 The accompanying drawings are structural schematic diagrams of the two-finger force-controlled underactuated manipulator based on differential connecting rod sliding provided by the present application;

[0028] Figure 2 The drawing is a schematic diagram of a two-finger force-controlled underactuated manipulator based on differential link sliding provided by the present application.

[0029] Figure 3 The drawing is a schematic diagram of a two-finger force-controlled underactuated manipulator based on differential link sliding provided by the present application.

[0030] Figure 4 The drawing is another schematic diagram of a two-finger force-controlled underactuated manipulator based on differential link sliding provided by the present application.

[0031] Figure 5 The drawing is a schematic diagram of the working principle of a two-degree-of-freedom differential link provided by the present application.

[0032] Figure 6 The drawing is a schematic diagram of the structure of a clamping arm provided by the present application.

[0033] Figure 7 The drawing is a schematic diagram of the structure of a force deformation provided by the present application.

[0034] Wherein:

[0035] 1 - underactuated gripping mechanism; 101 - cross beam; 102 - moving block; 103 - first link; 104 - second link; 105 - translating link; 106 - fixed block; 107 - sensor housing; 108 - sensor core; 109 - torsional spring; 2 - force measuring unit; 201 - first flexible beam; 202 - first bracket; 203 - first strain gauge; 204 - second flexible beam; 205 - second bracket; 206 - second strain gauge; 3 - telescopic mechanism; 301 - telescopic rod; 4 - support frame; 5 - clamping finger; 6 - part. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] Referring to the drawings, Figure 1 to the drawings, Figure 7 the embodiments of the present application disclose a two-finger force-controlled underactuated manipulator based on differential link sliding, comprising:

[0038] Support frame 4; the telescopic mechanism 3 is installed on the support frame 4; two clamping mechanisms are slidably connected to the end of the support frame 4 away from the telescopic mechanism 3, and the clamping mechanism comprises a sliding connection with the support frame 4 The translational link 105 and the clamping arm fixedly connected to one end of the translational link 105;

[0039] Under-actuated gripping mechanism 1; the under-actuated gripping mechanism 1 comprises a crossbeam 101 and two slider link assemblies slidably connected to the crossbeam 101; the crossbeam 101 is located inside the support frame 4 and is rotatably connected to the telescopic rod 31 of the telescopic mechanism 3, and a torsional spring 109 is installed between the end of the telescopic rod 31 away from the telescopic mechanism 3 and the crossbeam 101; one end of the slider link assembly is slidably connected to the crossbeam 101, and the other end is hingedly connected to the translational link 105 and the inner wall of the support frame 4;

[0040] Force measuring unit 2; the force measuring unit 2 is integrated inside the clamping arm.

[0041] As shown in Figure 2 , the end of the support frame 4 away from the telescopic mechanism 3 has an opening, and the two ends of the opening are fixed with fixed blocks 106, and the translational link 105 is slidably connected inside the fixed blocks 106; the slider link assembly comprises a movable block 102, a first link 103 and a second link 104;

[0042] The telescopic rod 301 is connected to the crossbeam 101 in a rotary joint manner, and a torsional spring 109 is installed between the two; two movable blocks 102 are installed on both sides of the crossbeam 101 and can slide along the crossbeam; the first link 103 and the second link 104 are rotatably connected to the movable block 102, and the other end of the second link 104 is rotatably connected to the translational link 105; the translational link 105 and the fixed block 106 form a moving pair, and the first link 103, the second link 104, the translational link 105 and the fixed block 106 form a rocker slider mechanism; in the initial position of the gripping mechanism (the initial distance between the two fingers is 2s0), β / 2>γ should be satisfied to ensure that a larger gripping motion can be obtained under a smaller telescopic mechanism output motion, that is, to achieve the purpose of motion amplification.

[0043] As shown in Figure 3 , when the manipulator grips the part 6 and the center line of the part 6 coincides with the center line of the manipulator, the linear motor 3 outputs displacement d1, the crossbeam 101 synchronously drives the movable blocks 102 on both sides, and the two movable blocks 102 respectively drive the rocker slider mechanisms A1B1C1 and A2B2C2 to move, at this time the two fingers 5 move synchronously and have the same displacement, and the distance from the center line is s0; when the clamping fingers 5 move synchronously, the rocker slider mechanisms on both sides move in the same state, and the crossbeam 101 always maintains a horizontal state; it can be seen that the clever cooperation of the crossbeam 101 and the rocker slider mechanism can convert the vertical motion of the linear motor 3 into horizontal gripping motion of the clamping fingers 5.

[0044] As Figure 4 shown, when the part 6 deviates from the center line of the manipulator by Δ, during the grabbing process, the right clamping finger 5 is closer to the part, and first contacts the part 6. Thereafter, the grabbing mechanism continues to move, the crossbeam 101 rotates clockwise, the torsion spring 109 is deformed, the left rocker slider mechanism A1B1C1 continues to move, until the left clamping finger 5 contacts the part 6, at this time, the clamping angles of the two sides satisfy β1>β2, the two movable sliders 102 slide on the crossbeam 101 with different displacements, the left side is larger than the right side; the displacement sensor cannot be used for position control, but can estimate the size of the grabbed part 6 according to the movement range; after the grabbing mechanism is retracted, the whole grabbing mechanism returns to the initial position under the action of the torsion spring 109. Figure 2

[0045] As Figure 5 shown, the grabbing mechanism of the present application adopts a differential mode based on two degrees of freedom linkage (movement and rotation of the center point), wherein the vertical movement is the active degree of freedom, directly driven by the linear motor 3, and the rotation is the passive degree of freedom; the torsion spring 109 restricts the rotation between the crossbeam 101 and the telescopic rod 301, when the displacements of the two sides of the crossbeam 101 are the same, the crossbeam 101 does not rotate; when the displacements of the two sides are different, the crossbeam 101 rotates to adapt to the difference between the displacements of the two sides.

[0046] As Figures 6-7 shown, the clamping arm includes a first flexible beam 201 and a second flexible beam 204, the end of the first flexible beam 201 is fixed with the clamping finger 5; one end of the second flexible beam 204 is fixedly connected with the end of the first flexible beam 201 away from the clamping finger 5, and the other end is fixedly connected with the translational linkage 105; the outer side of the first flexible beam 201 is fixed with the first support 202, a first gap is formed between one end of the first support 202 and the first flexible beam 201, and the other end is fixedly connected with the first flexible beam 201; the outer side of the second flexible beam 204 is fixed with the second support 205, a second gap is formed between one end of the second support 205 and the second flexible beam 204, and the other end is fixedly connected with the translational linkage 105.

[0047] The force measuring unit 2 is divided into two stages of force measuring units, including a first strain gauge 203 and a second strain gauge 206, the first strain gauge 203 is installed on the inner side of the first flexible beam 201; the second strain gauge 206 is installed on the inner side of the second flexible beam 204; the first strain gauge 203 and the second strain gauge 206 are respectively used to detect the elastic deformation of the first flexible beam 201 and the second flexible beam 204; the thickness of the first flexible beam is h1, and the thickness of the second flexible beam is h2, wherein h1 is less than h2, and the smaller the thickness, the smaller the stiffness (stiffness K=F / l).

[0048] ​From the connection mode, the first flexible beam 201 and the second flexible beam 204 adopt series connection; therefore, under the action of external force, the first flexible beam 201 deforms greatly, and the measurement accuracy of the first strain gauge 203 is higher than that of the second strain gauge 206, the first strain gauge 203 can be used for high-precision measurement of small grasping force, and the second strain gauge 206 is used for measuring large grasping force with small measurement accuracy.

[0049] Therefore, based on the two-stage force measuring unit, accurate force control of the manipulator in different grasping force ranges can be realized, the first support 202 and the second support 205 are mainly used to limit the maximum deformation of the first flexible beam 201 and the second flexible beam 204, so as to prevent yield deformation of the first flexible beam 201 and the second flexible beam 204 under the action of large grasping force.

[0050] The clamping end face of the clamping finger 5 is V-shaped, mainly used to ensure stable grasping of the part 6 and prevent the part 6 from slipping off the clamping finger 5 during grasping.

[0051] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0052] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A two-finger force-controlled underactuated manipulator based on differential link sliding, characterized in that, The utility model relates to a kind of underactuated gripper, including: Support frame (4);The telescopic mechanism (3) is installed on the support frame (4);Two clamping mechanisms are slidably connected to the end of the support frame (4) away from the telescopic mechanism (3), and the clamping mechanism includes sliding connection with the support frame (4) translational link (105) and with one end of the translational link (105) fixedly connected clamping arm; Underactuated gripper (1);The underactuated gripper (1) includes beam (101) and two slider link assemblies slidably connected on the beam (101);The beam (101) is located inside the support frame (4), and is rotatably connected with the telescopic rod (31) of the telescopic mechanism (3), and torsion spring (109) is installed between the telescopic rod (31) and the beam (101);One end of the slider link assembly is slidably connected on the beam (101), and the other end is hinged with the translational link (105) and the inner wall of the support frame (4);The slider link assembly includes dynamic slider (102), first link (103) and second link (104);The dynamic slider (102) is slidably connected on the beam (101), and one end of the first link (103) is hinged with the top surface of the dynamic slider (102), and the other end is hinged with the translational link (105);One end of the second link (104) is hinged with the bottom surface of the dynamic slider (102), and the other end is hinged with the inner wall of the support frame (4); Force measuring unit (2);The force measuring unit (2) is integrated inside the clamping arm; The clamping arm includes first flexible beam (201) and second flexible beam (204), and the end of the first flexible beam (201) is fixed with clamping finger (5);One end of the second flexible beam (204) is fixedly connected with the end of the first flexible beam (201) away from the clamping finger (5), and the other end is fixedly connected with the translational link (105);The thickness of the first flexible beam (201) is less than the thickness of the second flexible beam (204); The force measuring unit (2) includes first strain gauge (203) and second strain gauge (206);The first strain gauge (203) is installed inside the first flexible beam (201);The second strain gauge (206) is installed inside the second flexible beam (204).

2. The two-finger force-controlled underactuated manipulator based on differential link sliding according to claim 1, wherein, The end of the support frame (4) away from the telescopic mechanism (3) has opening, and both ends of the opening are fixed with fixed block (106), and the translational link (105) is slidably connected inside the fixed block (106).

3. The two-finger force-controlled underactuated manipulator based on differential link sliding according to claim 1, characterized in that, An outer side of the first flexible beam (201) is fixed with a first support (202), one end of the first support (202) and the first flexible beam (201) form a first gap, the other end is fixedly connected with the first flexible beam (201); an outer side of the second flexible beam (204) is fixed with a second support (205), one end of the second support (205) and the second flexible beam (204) form a second gap, the other end is fixedly connected with the translational linkage (105).

4. The two-finger force-controlled underactuated manipulator based on differential link sliding according to claim 1, characterized in that, The clamping end face of the clamping finger (5) is V-shaped.

5. The two-finger force-controlled underactuated manipulator based on differential link sliding according to claim 3, characterized in that, Further comprising a displacement sensor; the displacement sensor comprises a sensor shell (107) and a sensor core (108); the sensor shell (107) is fixed on the support frame (4), one end of the sensor core (108) is slidably connected with the sensor shell (107), the other end extends to the outside of the sensor shell (107) and is fixedly connected with the second support (205).

6. The two-finger force-controlled underactuated manipulator based on differential link sliding according to claim 1, wherein, The telescopic mechanism (3) is a linear motor.

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