Self-locking under-actuated gripper and structural optimization method thereof

Abstract

The application discloses a self-locking under-actuated gripper and a structural optimization method thereof, the self-locking under-actuated gripper comprising a driving mechanism, the upper part of the driving mechanism being provided with left-right symmetrical and same-structure index finger joint assemblies, the upper part of the index finger joint assemblies being provided with middle finger joint assemblies, and the upper part of the middle finger joint assemblies being provided with end finger joint assemblies. The self-locking under-actuated gripper provided by the application can not only realize self-adaptive enveloping grabbing of multi-size disc workpieces, but also realize self-locking in the process of gripping, thereby avoiding the problem that the workpieces are prone to falling off when slightly heavy workpieces are grabbed, and improving the firmness, stability and accuracy of gripping. The structural optimization method of the gripper realizes global optimization of structural parameters, and guarantees force balance of the gripper when workpieces are self-locked and gripped.

Description

Technical Field

[0001] This invention belongs to the field of industrial robot technology, and in particular relates to robot grippers and their structural optimization methods. Background Technology

[0002] With the increasing variety of products on the market, a growing number of diverse, small-batch workpieces are appearing on automated production lines, making industrial robots the main players in these lines. However, to handle workpiece handling during production, robots often need to frequently change fixtures, reducing production line efficiency.

[0003] In recent years, underactuated mechanisms based on the underrank principle have emerged. Due to their adaptive envelope advantage, underactuated mechanisms can meet the "one-to-many" gripping requirements on production lines, attracting attention from scholars both domestically and internationally and becoming a research hotspot. Therefore, designing novel grippers based on the underrank mechanism principle helps solve the gripping needs of robots for workpieces of various shapes and sizes during workpiece handling. However, since underactuated mechanisms often employ multi-joint finger mechanisms, current designs are mostly based on engineering experience. Therefore, during envelope gripping, the mechanism often suffers from reduced stability and accuracy due to the inability of the joints to achieve force balance. Furthermore, most existing underactuated mechanisms lack self-locking functionality, which can lead to detachment and dangerous situations when gripping slightly heavier workpieces.

[0004] The invention patent with application number "202011408245.X" discloses a robot end effector and its structural optimization method. This patent designs a novel end effector with adaptive envelope grasping based on the principle of underrank mechanisms. However, this end effector mainly relies on the tension of the spring itself to grip the workpiece, lacking self-locking capability. It is only suitable for lightweight workpieces; for heavier workpieces, there is a risk of slippage, leading to safety accidents. Furthermore, due to the relatively small clamping force, the workpiece may wobble or vibrate, resulting in poor reliability, stability, and positioning accuracy, and may even affect the normal operation of the equipment.

[0005] Therefore, based on the design of a novel gripper with a self-locking function based on the principle of underrank mechanism, the design of corresponding structural optimization methods can help improve the effectiveness and stability of robot gripping of workpieces. Summary of the Invention

[0006] The purpose of this invention is to address the problems and shortcomings of the existing technology by combining the adaptive envelope grasping technology of underrank mechanism principle to a robot gripper, thereby providing a self-locking underactuated gripper that is secure, stable, accurately positioned, and has self-locking capability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A self-locking underactuated gripper includes a drive mechanism 1. A gripping mechanism is mounted on the upper end face of the drive mechanism 1 and is arranged in a mirror symmetrical manner. The gripping mechanism is composed of a first phalanx assembly 2, a middle phalanx assembly 3 and a last phalanx assembly 4 connected from bottom to top.

[0009] The drive mechanism 1 includes a cylinder body 5. The upper end face of the cylinder body 5 is equipped with mirror-symmetrical pneumatic sliders 6, which are separated from each other on the left and right. A transmission slider 7 is fixedly connected to the pneumatic slider 6 by bolts. The lower end of the drive connecting rod 8 is rotatably connected to the upper end of the drive connecting rod 8, and the lower end of the first finger joint transmission connecting rod 9 is rotatably connected to the upper end of the first finger joint transmission connecting rod 9. A mirror-symmetrical support arm 10 is fixedly provided at the rear end of the cylinder body 5 corresponding to the transmission slider (7). The upper end of the first finger joint transmission connecting rod 9 is rotatably connected to the rotating shaft at the upper end of the support arm 10.

[0010] The first finger joint assembly 2 includes a first finger joint frame 11. The left and right vertical frames of the first finger joint frame 11 each employ two identical, symmetrically arranged rods. The lower frame of the first finger joint frame 11 is rotatably connected to the upper pivot of the support arm 10. The first finger joint frame 11 is bolted from bottom to top to sequentially clamp and fix the lower guide member 12, the upper guide member 13, and the L-shaped rod 14 of the first finger joint. The upper end of the L-shaped rod 14 is rotatably connected to the left end of the arc of the middle finger joint tripod 15. The lower guide member 12 includes a first I-beam 16 and a second I-beam 16 that are parallel to each other. The first I-beam 16 and the second I-beam 17 are respectively fixed between the left and right side frames of the first finger joint frame 11. A first guide tube 18, with its left end closed and its right end open, is clamped and fixed between the first I-beam 16 and the second I-beam 17. A first spring 19 is installed inside the first guide tube 18. The right end of the first spring 19 is supported on the left end of the first finger joint lower compression spring rod 20. A first pin 21, perpendicular to its axis, is also fixed to the left end of the first finger joint lower compression spring rod 20. The first pin 21 can move left and right within the axial groove of the first guide tube 18. The right end of the first phalanx compression spring rod 20 is fixed to the lower left part of the first phalanx clamping block 22. The first phalanx upper guide member 13 includes a third I-beam 23 and a fourth I-beam 24 that are parallel to each other. The third I-beam 23 and the fourth I-beam 24 are also fixed between the left and right side frames of the first phalanx frame 11, respectively. A second guide tube 25 with its left end closed and its right end open is clamped and fixed between the third I-beam 23 and the fourth I-beam 24. A second spring 26 is installed inside the second guide tube 25. The right end of the second spring 26 is supported on the left end of the first phalanx upper compression spring rod 27. The right end of the upper compression spring rod 27 is fixed to the upper left part of the first finger joint clamping block 22. The lower compression spring rod 20 and the upper compression spring rod 27 of the first finger joint jointly support the first finger joint clamping block 22. The middle crossbar of the first finger joint frame 11 is rotatably connected to the turning point of the first finger joint crank rod 28. The first pin 21 is embedded in the groove at the lower end of the first finger joint crank rod 28 and can slide along the groove. The upper end of the first finger joint crank rod 28 is rotatably connected to the lower end of the middle finger joint transmission connecting rod 29, thereby converting the left and right movement of the first finger joint clamping block 22 into the rotation of the first finger joint crank rod 28, providing power for the next stage middle finger joint assembly 3.

[0011] The middle finger joint assembly 3 includes a middle finger joint frame 30. The left and right vertical frames of the middle finger joint frame 30 each employ two identical symmetrical rod structures. The middle finger joint frame 30 is bolted from bottom to top to secure the middle finger joint tripod 15, the lower middle finger joint guide 31, the upper middle finger joint guide 32, and the middle finger joint T-shaped rod 33. The right end of the arc of the middle finger joint tripod 15 is rotatably connected to the upper end of the middle finger joint transmission connecting rod 29. The lower middle finger joint guide 31 has the same structure as the lower first finger joint guide 12, including a fifth I-beam 34, a sixth I-beam 35, a third guide tube 36, a third spring 37, a lower middle finger joint compression spring rod 38, and a second pin 39. The right end of the lower middle finger joint compression spring rod 38 is fixed to the lower left of the middle finger joint clamping block 40. The upper middle finger joint guide... The guide member 32 and the guide member 13 on the first finger joint have the same structure, including the seventh I-beam 41, the eighth I-beam 42, the fourth guide tube 43, the fourth spring 44, and the middle finger joint upper compression spring rod 45. The right end of the middle finger joint upper compression spring rod 45 is fixed to the upper left part of the middle finger joint clamping block 40. The middle finger joint lower compression spring rod 38 and the middle finger joint upper compression spring rod 45 jointly support the middle finger joint clamping block 40. The middle finger joint frame 30 is rotatably connected to the middle finger joint crank rod 46 at the turning point on the middle finger joint frame 30. The lower end of the middle finger joint crank rod 46 has a second pin 39 embedded in the groove and can slide along the groove. The upper end of the middle finger joint crank rod 46 is rotatably connected to the lower end of the end finger joint transmission connecting rod 47, thereby converting the left and right movement of the middle finger joint clamping block 40 into the rotation of the middle finger joint crank rod 46, providing power for the next stage end finger joint assembly 4.

[0012] The distal phalanx assembly 4 includes a distal phalanx clamping block 48. The lower left end of the distal phalanx clamping block 48 is rotatably connected to the upper end of the middle phalanx T-shaped rod 33, and the lower right end of the distal phalanx clamping block 48 is rotatably connected to the upper end of the distal phalanx transmission link 47. The power of the middle phalanx assembly 3 is transmitted to the distal phalanx clamping block 48 through the distal phalanx transmission link 47, so that the distal phalanx clamping block 48 rotates around the upper end of the middle phalanx T-shaped rod 33.

[0013] Furthermore, the first phalanx clamping block 22 is a concave structural component including a mounting surface and a clamping surface, and the inner side of the concave portion is arc-shaped.

[0014] Furthermore, the middle finger joint clamping block 40 is a concave structural component including a mounting surface and a clamping surface, and the inner side of the concave portion is arc-shaped.

[0015] Furthermore, the distal phalanx clamping block 48 is a knife-shaped structural component including an mounting end and a clamping end. The blade handle portion for mounting has two connecting holes, and the blade portion for clamping has a concave structure with an arc-shaped inner side.

[0016] Furthermore, the clamping surfaces of the first phalanx clamping block 22, the middle phalanx clamping block 40, and the last phalanx clamping block 48 are all provided with an impact-resistant and anti-slip layer.

[0017] To achieve the above objectives, another technical solution adopted by the present invention is as follows:

[0018] A structural optimization method for a self-locking underactuated gripper includes establishing a gripper clamping contact force model, a gripper structural parameter optimization method, and a gripper structural parameter optimization process.

[0019] I. Establishment of the clamping contact force model of the gripper, including the following contents and steps:

[0020] (1) Establish the geometric and static models based on the structure of the clamp;

[0021] Given that the self-locking underactuated gripper has a symmetrical structure, the model is established and the structure is optimized by taking the left three-finger joint as an example. The geometric model is established by equating the driving link 8 in the driving mechanism 1 to a rod AB, the first finger joint transmission link 9 to a rod BC2, the first finger joint frame 11 to a quadrilateral C1C3C4E1, the first finger joint curved rod 28 to a folded rod QD2D3, the portion from the left end of the middle crossbar of the first finger joint frame 11 to the turning point of the first finger joint curved rod 28 to a rod D1D2, the middle finger joint transmission link 29 to a rod QP, the middle finger joint frame 30 to a quadrilateral E1E2E5G1, the middle finger joint curved rod 46 to a folded rod RE4E3, the portion from the left end of the middle crossbar of the middle finger joint frame 30 to the turning point of the middle finger joint curved rod 46 to a rod E6E4, the last finger joint transmission link 47 to a rod RU, and the last finger joint... The clamping block 48 is equivalent to quadrilateral G1G2G3G4. Since the first spring 19 and the second spring 26 are stretched and compressed synchronously and have the same deformation, the force on both is equivalent to that on spring D4D3 in the model calculation, and spring D4D3 is represented by s1. Similarly, the force on the third spring 37 and the fourth spring 44 is equivalent to that on spring E7E3, and spring E7E3 is represented by s2. The lengths of rods C1C3, D1D2, E1E2, G1U and E6E4 are defined as a1, a2, a3, a4 and a5, respectively. The lengths of rods E1B, G1E1, G1G4, D1B and E1E6 are defined as d1, d2, d3, d4 and d5, respectively. The lengths of rods D2D3, D2Q, PQ, E3E4, E4R and RU are defined as l1, l2, l3, l4, l5 and l6, respectively.

[0022] The establishment of the static model involves defining the torque of the driving mechanism 1 as T1, and the driving forces of the springs s1 and s2 as T2 and T3, respectively; defining the contact forces of the first phalanx assembly 2, the middle phalanx assembly 3, and the last phalanx assembly 4 that clamp the object as F1, F2, and F3, respectively; defining the distance from point C1 to force F1 as h1, the distance from point E1 to force F2 as h2, and the distance from point G1 to force F3 as h3; and defining the angle between rods E2P and QP, and the angle between rod PQ and D2Q. Angles are defined as follows: the angles between rods G2U and RU, UR and E4R, and C4E1 and C1E1 are α1, α2, α3, α4, and α5, respectively; the angles between rod E1C1 and the horizontal line in the opposite direction are defined as follows: the angle between rod G1E1 and the line extending in the opposite direction of rod C1E1, and G4G1 and the line extending in the opposite direction of rod E1G1 are defined as β1, β2, and β3, respectively; the angles between rod C3C1 and the horizontal line, PE1 and the horizontal line, and UG1 and the horizontal line are defined as follows:

[0023] (2) Establish the virtual work equations for each finger joint of the gripper based on the principle of virtual work:

[0024] In the formula, Let v be the imaginary angular velocity of the torque T1 acting on the first phalanx. s1 v s2 These are the virtual velocities on springs s1 and s2, respectively; v F1 v F2 v F3 These are the virtual velocities of the contact forces F1, F2, and F3 at the point of contact, respectively.

[0025] Let T = [T1 F1 + T2 F2 + T3] T F = [F1 F2 F3] T , V F =[v F1 v F2 v F3 ] T The virtual work equation can be simplified to: F T V F =T T W.

[0026] (3) Establish the virtual velocity V of each finger joint of the gripper based on the rigid body velocity formula. F =[v F1 v F2 v F3 ] T for:

[0027]

[0028] In the formula, δ β1 δ β2 δ β3 These are the angular velocities for rotation angles β1, β2, and β3, respectively.

[0029] virtual velocity V F Written in matrix form: V F =J v [δ β1 δ β2 δ β3 ] T .

[0030] In the formula,

[0031] (4) Since both the middle finger joint transmission link 29 (PQ) and the end finger joint transmission link 47 (UR) exert direct forces on their respective finger joint assemblies, calculate the virtual velocity v of the two links. PQ v UR :

[0032]

[0033] because,

[0034]

[0035]

[0036]

[0037]

[0038] Therefore, the virtual velocity v of the middle finger joint transmission link 29 (PQ) and the end finger joint transmission link 47 (UR) PQ v UR for:

[0039]

[0040] For the five-bar linkage E1PQD2D1, with E1 and D1 as the positive x-axis and the direction pointing towards the disk workpiece as the positive y-axis, its vector closure equation is as follows:

[0041] Decompose it into x and y directions:

[0042] For α6+β2, Differentiate:

[0043]

[0044] Because α6 is a fixed angle, therefore δα6 =0. Based on the angular velocity relationship of the same component, we can obtain: Let m be the term on the right side of the above equation, then the equation can be rearranged to obtain:

[0045] Similarly, for the five-bar linkage G1URE4E6, its vector closure equation is as follows:

[0046] Right now:

[0047] For α7+β3, Differentiating and rearranging, we get:

[0048]

[0049] Since α7 is a fixed angle, then δ α7 =0, based on the angular velocity relationship of the same component, we can obtain: Let n be the term on the right side of the above equation, then it can be rearranged to obtain:

[0050] because Will and Substituting the imaginary velocity v PQ v UR From the middle, and by sorting, we can obtain:

[0051] In the formula,

[0052]

[0053] (5) Calculate the virtual velocities v on springs s1 and s2. s1 v s2 .

[0054] Based on the geometric relationships between structural components in the described geometric and static models of the clamp, it can be concluded that:

[0055]

[0056] Therefore, the virtual velocities on springs s1 and s2 are:

[0057] In the formula,

[0058]

[0059] (6) Calculate the contact force of the clamp F = [F1 F2 F3] T .

[0060] Based on the angular velocity relationship of the same component, we can obtain: Combined with the virtual velocities v on springs s1 and s2 s1 and v s2 The above W can be written in matrix multiplication form: W = J ω [δ β1 δ β2 δ β3 ] T .

[0061] In the formula,

[0062] virtual velocity V F Substituting W into the simplified virtual work equation, we get: F T J v =T T J ω .

[0063] The contact force is then:

[0064] In the formula, and

[0065]

[0066] Since the driving forces T2 and T3 of springs s1 and s2 are much smaller than the clamping force F, they can be ignored, and the clamping force F can be obtained:

[0067]

[0068] Further simplification yields F:

[0069] The above formula gives the contact force F = [F1 F2 F3] T The relationship between F and T1. From the equation, it can be seen that the contact force F is affected by β1~β3, The influence of equal angles and finger mechanism dimensions.

[0070] II. A method for optimizing the structural parameters of the gripper, including an immune optimization algorithm based on population effects. The immune evolutionary algorithm based on population effects is derived from the operators (including the immune selection operator O) of the basic immune optimization algorithm. s Immune crossover operator O c and immune variant operator O m Based on this, a new immune aggregation operator O was designed according to the population effect. g and immune diffusion operator O d Optimize and improve the algorithm.

[0071] Given a population A(k) with n individuals in the kth generation, where A(k) = [a1(k), a2(k), ..., a n(k)], then the immune selection operator O s can be described as:

[0072]

[0073] The immune crossover operator O c can be described as:

[0074] The immune mutation operator O m can be described as:

[0075] The said immune clustering operator O g mainly enables the dominant individuals in the population to form a clustering population to have a calling influence on the inferior individuals with poor fitness, thereby improving the performance of the inferior individuals.

[0076] Let the clustering number be m, the clustering distance be l (l < n), and the number of inferior individuals with poor fitness be n. The process of the immune clustering operator is as follows:

[0077] (1) Select the individual a*(k) with the best fitness from the population A″′(k) after immune mutation;

[0078] (2) Generate m dominant individuals whose clustering distance from a*(k) is less than l, and form a clustering population |a * -g i (k)| ≤ l, |·| represents the Hamming distance;

[0079] (3) Select z individuals with the worst fitness from the population A″′(k), and form an inferior population W(k) = [w1(k), w2(k), …, w z (k)];

[0080] (4) Extract the individual w i (k) (i ∈ [1, z]), perform an exclusive OR operation on it with the individuals in G(k) respectively, and obtain G'(k) = [g'1(k), g'2(k), …, g' m (k)];

[0081] (5) Extract the optimal individual in G'(k) = [g'1(k), g'2(k), …, g' m (k)] and compare it with w i (k). If the former is better than the latter, replace the latter; otherwise, retain the latter;

[0082] (6) Determine whether all individuals in W(k) have completed the exclusive OR operation with the individuals in G(k)? If not, go to step (4); otherwise, exit.

[0083] Immune aggregation operator O g can be described as:

[0084]

[0085] The immune diffusion operator O d mainly allows the individuals with high concentration in the population to diffuse to prevent the individuals from falling into local minima.

[0086] Assume the diffusion distance is r (r < n) and the diffusion number is s. The process of the immune diffusion operator is as follows:

[0087] (1) Select the s antibodies with the highest concentration from the population A IV (k) after immune aggregation and form the diffusion population D(k) = [d1(k), d2(k), …, d s (k)];

[0088] (2) Randomly generate an initial individual a 0 (k), and the number of its elements that are 1 is greater than r and less than or equal to n;

[0089] (3) Take out the individual d i (k) (i ∈ [1, s]) from D(k) and perform the exclusive OR operation with the individual a 0 (k) to obtain a new individual d i '(k);

[0090] (4) Compare the individual d i (k) with d i '(k). If the latter is better than the former, replace the former; otherwise, keep the former;

[0091] (5) Determine whether all antibodies in D(k) have completed the exclusive OR operation with a 0 (k)? If not, go to step (3); otherwise, exit.

[0092] The immune diffusion operator O d can be described as:

[0093]

[0094] III. The optimization process of the gripper structure parameters includes the following contents and steps:

[0095] (1) Based on the clamping force F of the gripper and with the goal of making the contact force as evenly and equal as possible during clamping, establish the objective function for parameter optimization in the stable clamping state of the gripper:

[0096] minf(X)=min((F1-F2) 2 +(F1-F3) 2 +(F2-F3) 2 ).

[0097] In the formula, X is the set of structural parameter variables of the gripper and

[0098] (2) Set the constraint range of the clamp parameter variable set X;

[0099] (3) Initialize the parameters of the immune optimization algorithm based on population effects, and the initial population A(k) = [a1(k), a2(k), ..., a n [(k)], k←0;

[0100] (4) Immune selection: A′(k)←O s (A(k))=[a1′(k),a2′(k),…,a n ′(k)];

[0101] (5) Immune crossover: A″(k)←O c (A′(k))=[a1″(k),a2″(k),…,a n "(k)];

[0102] (6) Immune variation: A″′(k)←O m (A″(k))=[a1″′(k),a2″′(k),…,a n "′(k)];

[0103] (7) Immune accumulation:

[0104] (8) Immune diffusion:

[0105] (9) Termination condition determination. Has the number of generations k reached the maximum? If so, the algorithm terminates and outputs the optimal variable X. * Otherwise, k←k+1, and return to step (4).

[0106] The present invention has the following advantages and beneficial effects:

[0107] 1. Compared with existing single-type robot-specific grippers, the novel gripper designed based on the underrank principle of this invention can achieve adaptive envelope gripping of disc workpieces of different sizes, which greatly improves the problem of high labor intensity and low production efficiency caused by changing special grippers due to changes in workpiece size.

[0108] 2. This clamp can restrict the workpiece's degree of freedom from bottom to top, has a large clamping force, and has a self-locking capability, effectively avoiding the risk of slippage due to the workpiece's own weight, greatly improving the stability, reliability, and positioning accuracy of the clamping, and effectively reducing the occurrence of safety accidents.

[0109] 3. This gripper is designed based on the underactuated principle, with only one power source, which greatly reduces the difficulty of the control task and shortens the entire design cycle of the product.

[0110] 4. A novel immune optimization algorithm based on population effects is proposed. An immune clustering operator is designed based on the clustering behavior in population effects, which improves the algorithm's local search capability by encouraging superior individuals to support inferior individuals. An immune diffusion operator is designed based on the diffusion behavior in population effects, which effectively avoids the algorithm getting trapped in local minima by diffusing high-concentration individuals.

[0111] 5. The workpiece clamping stability of a self-locking underactuated gripper depends on the gripper's structural parameters, but it is a multi-parameter structure with multiple constraints. Trial-and-error design based on manual experience is not only time-consuming and labor-intensive but also fails to yield optimal structural parameters. By establishing a gripper contact force model and utilizing an immune optimization algorithm based on swarm effects, global optimization of gripper parameters can be achieved, improving both optimization efficiency and accuracy. Attached Figure Description

[0112] Figure 1 : Overall structural diagram of the clamp in the embodiment of the present invention;

[0113] Figure 2 : A structural diagram of the drive mechanism of the gripper in an embodiment of the present invention;

[0114] Figure 3 : Overall structural diagram of the first finger joint assembly of the gripper in this embodiment of the invention;

[0115] Figure 4 : A partial structural diagram of the first finger joint assembly of the gripper in an embodiment of the present invention;

[0116] Figure 5 : A structural diagram of the first finger joint guide and clamping block assembly of the clamp in an embodiment of the present invention;

[0117] Figure 6 : The L-shaped rod of the first finger joint of the clamp in the embodiment of the present invention;

[0118] Figure 7 The first finger joint of the clamp in this embodiment of the invention;

[0119] Figure 8 The middle finger joint tripod of the clamp in this embodiment of the invention;

[0120] Figure 9 : Structural diagrams of the middle and distal phalanx assemblies of the gripper in this embodiment of the invention;

[0121] Figure 10 : A structural diagram of the middle finger joint guide and clamping block assembly of the clamp in an embodiment of the present invention;

[0122] Figure 11 : A structural diagram of the distal phalanx clamping block of the clamp in an embodiment of the present invention;

[0123] Figure 12 : A schematic diagram of the gripper before it grasps the disc workpiece in this embodiment of the invention;

[0124] Figure 13 : A schematic diagram of the gripper enveloping and grasping the disc workpiece in an embodiment of the present invention;

[0125] Figure 14 : Geometric model diagram of the self-locking underactuated gripper in an embodiment of the present invention;

[0126] Figure 15 : Static model diagram of the self-locking underactuated gripper in this embodiment of the invention;

[0127] The reference numerals in the figure are as follows: 1. Drive mechanism; 2. First finger joint assembly; 3. Middle finger joint assembly; 4. Last finger joint assembly; 5. Cylinder body; 6. Pneumatic slider; 7. Transmission slider; 8. Drive link; 9. First finger joint transmission link; 10. Support arm; 11. First finger joint frame; 12. Lower guide of the first finger joint; 13. Upper guide of the first finger joint; 14. L-shaped rod of the first finger joint; 15. Triangular frame of the middle finger joint; 16. First I-beam; 17. Second I-beam; 18. First guide tube; 19. First spring; 20. Lower compression spring rod of the first finger joint; 21. First pin; 22. First finger joint clamping block; 23. Third I-beam; 24. Fourth I-beam; 25. Second guide tube; 2 6. Second spring; 27. Upper compression spring rod of the first finger joint; 28. Crank rod of the first finger joint; 29. ​​Transmission connecting rod of the middle finger joint; 30. Middle finger joint frame; 31. Lower guide member of the middle finger joint; 32. Upper guide member of the middle finger joint; 33. T-shaped rod of the middle finger joint; 34. Fifth I-beam; 35. Sixth I-beam; 36. Third guide tube; 37. Third spring; 38. Lower compression spring rod of the middle finger joint; 39. Second pin; 40. Middle finger joint clamping block; 41. Seventh I-beam; 42. Eighth I-beam; 43. Fourth guide tube; 44. Fourth spring; 45. Upper compression spring rod of the middle finger joint; 46. Crank rod of the middle finger joint; 47. Transmission connecting rod of the last finger joint; 48. Clamping block of the last finger joint; 49. Disc workpiece. Detailed Implementation

[0128] To make the objectives and technical solutions of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the described embodiments of this invention without creative effort are within the scope of protection of this invention.

[0129] The terms "front" and "back" as used in this invention refer to the viewer's orientation relative to the drawing, with the viewpoint pointing towards the viewer being considered "front" and the viewpoint pointing towards the viewer being considered "back," rather than a specific limitation on the gripper device of this invention.

[0130] The "left" and "right" in this invention refer to the left side of the view paper as left and the right side as right when the reader is facing the accompanying drawings, and do not constitute a specific limitation on the gripper device of this invention.

[0131] In this invention, "upper" and "lower" refer to the top edge of the view paper as "up" and the right edge as "right" when the reader is facing the accompanying drawings, and are not a specific limitation on the clamping device of this invention.

[0132] like Figure 1 As shown, a self-locking underactuated gripper of the present invention includes a drive mechanism 1. The upper part of the drive mechanism 1 is connected to a first phalanx assembly 2 that is symmetrical and identical in structure. The upper part of the first phalanx assembly 2 is connected to a middle phalanx assembly 3 that is symmetrical and identical in structure. The upper part of the middle phalanx assembly 3 is connected to a distal phalanx assembly 4 that is symmetrical and identical in structure.

[0133] like Figure 1 and 2 As shown, the drive mechanism 1 of a self-locking underactuated gripper of the present invention includes a cylinder body 5. A pneumatic slider 6, symmetrically arranged and structurally identical, is mounted on the upper end of the cylinder body 5. A transmission slider 7 is bolted to the upper end of the pneumatic slider 6. The lower end of a drive connecting rod 8 is rotatably connected to the transmission slider 7. The upper end of the drive connecting rod 8 is rotatably connected to the lower end of a first finger joint transmission connecting rod 9. A symmetrical support arm 10, with identical structure, is fixedly arranged at the rear end of the cylinder body 5 corresponding to the transmission slider 7. The upper end of the first finger joint transmission connecting rod 9 is rotatably connected to a rotating shaft at the upper end of the support arm 10. By driving the pneumatic slider 6 to move left and right, the first finger joint transmission connecting rod 9 can rotate counterclockwise or clockwise around the rotating shaft at the upper end of the support arm 10, thereby driving the rotation of the first finger joint assembly 2.

[0134] like Figure 1As shown in Figures 3, 4, 5, 6, and 7, a first finger joint assembly 2 of a self-locking underactuated gripper of the present invention includes a first finger joint frame 11. The left and right vertical frames of the first finger joint frame 11 each employ two identical rod structures symmetrically arranged front and back. The lower frame of the first finger joint frame 11 is rotatably connected to the upper shaft of the support arm 10. The first finger joint frame 11 clamps and fixes the lower guide member 12, the upper guide member 13, and the L-shaped rod 14 of the first finger joint sequentially from bottom to top using bolts. The upper end of the L-shaped rod 14 is rotatably connected to the left end of the arc of the middle finger joint tripod 15. The lower guide member 12 includes a first working member that is parallel to each other. The first I-beam 16 and the second I-beam 17 are respectively fixed between the left and right side frames of the first finger joint frame 11. A first guide tube 18, with its left end closed and its right end open, is clamped and fixed between the first I-beam 16 and the second I-beam 17. A first spring 19 is installed inside the first guide tube 18. The right end of the first spring 19 is supported on the left end of the first finger joint lower pressure spring rod 20. A first pin 21, perpendicular to its axis, is also fixed to the left end of the first finger joint lower pressure spring rod 20. The first pin 21 can move left and right within the axial groove of the first guide tube 18. The first finger joint lower pressure spring rod 20... The right end is fixed to the lower left part of the first finger joint clamping block 22. The guide member 13 on the first finger joint includes a third I-beam 23 and a fourth I-beam 24 that are parallel to each other. The third I-beam 23 and the fourth I-beam 24 are also fixed between the left and right frames of the first finger joint frame 11, respectively. A second guide tube 25 with its left end closed and its right end open is clamped and fixed between the third I-beam 23 and the fourth I-beam 24. A second spring 26 is installed inside the second guide tube 25. The right end of the second spring 26 is supported on the left end of the compression spring rod 27 on the first finger joint. The right end of the compression spring rod 27 on the first finger joint is fixed to the upper left part of the first finger joint clamping block 22. The lower compression spring rod 20 and the upper compression spring rod 27 of the first finger joint jointly support the first finger joint clamping block 22. The first finger joint clamping block 22 is a concave structural component including a mounting surface and a clamping surface, and the inner side of the concave part is arc-shaped to better fit the contour of the workpiece. The middle crossbar of the first finger joint frame 11 is rotatably connected to the turning point of the first finger joint crank rod 28. The first pin 21 is embedded in the groove at the lower end of the first finger joint crank rod 28 and can slide along the groove. The upper end of the first finger joint crank rod 28 is rotatably connected to the lower end of the middle finger joint transmission connecting rod 29, thereby converting the left and right movement of the first finger joint clamping block 22 into the rotation of the first finger joint crank rod 28, providing power for the next stage middle finger joint assembly 3.Before clamping the workpiece, under the self-elastic force of the first spring 19 and the second spring 26, the first finger joint clamping block 22 is pushed to the right. Simultaneously, as the lower pressure spring rod 20 of the first finger joint moves to the right, it drives the first pin 21 to move to the right, thereby pushing the first finger joint crank rod 28 to rotate counterclockwise around the central bend. Power is then transmitted to the middle finger joint assembly 3 via the middle finger joint transmission link 29, which is rotatably connected to the upper end of the first finger joint crank rod 28. When clamping the workpiece begins, the first finger joint clamping block 22 is pressed upon contact with the workpiece, thereby pushing the lower pressure spring rod 20 and the upper pressure spring rod 27 of the first finger joint to the left. Simultaneously, the first finger joint crank rod 28, driven by the leftward movement of the first pin 21, rotates clockwise around the bend, and drives the middle finger joint assembly 3 to rotate via the middle finger joint transmission link 29.

[0135] like Figure 1As shown in Figures 5, 8, 9, 10, and 11, a middle finger joint assembly 3 of a self-locking underactuated gripper of the present invention includes a middle finger joint frame 30. The left and right vertical frames of the middle finger joint frame 30 each employ a symmetrical two-bar structure. The middle finger joint frame 30 is bolted from bottom to top to sequentially clamp and fix a middle finger joint triangle 15, a lower middle finger joint guide 31, an upper middle finger joint guide 32, and a middle finger joint T-shaped bar 33. The right end of the arc-shaped part of the frame 15 is rotatably connected to the upper end of the middle finger joint transmission linkage 29. The lower guide member 31 of the middle finger joint and the lower guide member 12 of the first finger joint have the same structure, including the fifth I-beam 34, the sixth I-beam 35, the third guide tube 36, the third spring 37, the lower pressure spring rod 38 of the middle finger joint and the second pin 39. The right end of the lower pressure spring rod 38 of the middle finger joint is fixed to the lower left part of the middle finger joint clamping block 40. The upper guide member 32 of the middle finger joint and the upper guide member 39 of the first finger joint are connected to the upper guide member 39 of the first finger joint. Component 13 has the same structure, including the seventh I-beam 41, the eighth I-beam 42, the fourth guide tube 43, the fourth spring 44, and the middle finger joint upper compression spring rod 45. The right end of the middle finger joint upper compression spring rod 45 is fixed to the upper left part of the middle finger joint clamping block 40. The middle finger joint lower compression spring rod 38 and the middle finger joint upper compression spring rod 45 jointly support the middle finger joint clamping block 40. The middle finger joint clamping block 40 is a concave structural component including a mounting surface and a clamping surface, and the inner side of the concave part is arc-shaped. To better conform to the contour of the workpiece, the middle finger joint frame 30 is rotatably connected to the turning point of the middle finger joint crank 46 on the middle crossbar. The lower end of the middle finger joint crank 46 has a groove in which a second pin 39 is embedded and can slide along the groove. The upper end of the middle finger joint crank 46 is rotatably connected to the lower end of the end finger joint transmission link 47, thereby converting the left and right movement of the middle finger joint clamping block 40 into the rotation of the middle finger joint crank 46, providing power to the next stage end finger joint assembly 4. Similar to the operation of the first finger joint assembly 2, before clamping the workpiece, under the elastic force of the third spring 37 and the fourth spring 44, the middle finger joint clamping block 40 is pushed to the right, and the middle finger joint crank 46 is driven by the second pin 39 on the middle finger joint lower pressure spring rod 38 to rotate counterclockwise around its middle turning point. The power is then transmitted to the end finger joint assembly 4 through the end finger joint transmission link 47, which is rotatably connected to the upper end of the middle finger joint crank 46. When the workpiece is clamped, the middle finger joint clamping block 40 is pressed as it comes into contact with the workpiece, thereby pushing the lower middle finger joint compression spring rod 38 and the upper middle finger joint compression spring rod 45 to the left. At the same time, the middle finger joint crank rod 46 rotates clockwise around the turning point under the leftward movement of the second pin 39, and drives the end finger joint assembly 4 to rotate through the end finger joint transmission link 47.

[0136] The present invention discloses a self-locking underactuated gripper, comprising a distal phalanx assembly 4, including a distal phalanx clamping block 48. The lower left end of the distal phalanx clamping block 48 is rotatably connected to the upper end of the middle phalanx T-shaped rod 33, and the lower right end of the distal phalanx clamping block 48 is rotatably connected to the upper end of the distal phalanx transmission link 47. The power of the middle phalanx assembly 3 is transmitted to the distal phalanx clamping block 48 through the distal phalanx transmission link 47, causing the distal phalanx clamping block 48 to rotate around the upper end of the middle phalanx T-shaped rod 33. Before clamping the workpiece, it rotates counterclockwise away from the workpiece; when clamping the workpiece, it rotates clockwise towards the workpiece. The distal phalanx clamping block 48 is a knife-shaped structure including a mounting end and a clamping end. The tool holder portion for mounting has two connecting holes, and the blade portion for clamping has a concave structure with an arc-shaped inner side to better conform to the contour of the workpiece.

[0137] The present invention discloses a self-locking underactuated gripper, comprising a distal phalanx assembly 4, including a distal phalanx clamping block 48. The lower right end of the distal phalanx clamping block 48 is rotatably connected to the upper end of a distal phalanx transmission link 47, and the lower left end of the distal phalanx clamping block 48 is rotatably connected to the upper end of a middle phalanx T-shaped rod 33. The power of the middle phalanx assembly 3 is transmitted to the distal phalanx clamping block 48 through the distal phalanx transmission link 47, causing the distal phalanx clamping block 48 to rotate around the upper end of the middle phalanx T-shaped rod 33. Before clamping a workpiece, the distal phalanx clamping block 48 rotates counterclockwise away from the workpiece. When clamping a workpiece, the distal phalanx clamping block 48 rotates clockwise towards the workpiece. The distal phalanx clamping block 48 is a knife-shaped structure including a mounting end and a clamping end. The mounting part of the knife handle has two connecting holes, and the clamping part of the blade is concave with an arc-shaped inner side to better conform to the contour of the workpiece.

[0138] like Figure 1 , 2As shown in 4, 5, 9, 10, 12, and 13, before clamping the disc workpiece 49, the first spring 19 and the second spring 26 in the first finger joint assembly 2, and the third spring 37 and the fourth spring 44 in the middle finger joint assembly 3, keep the first finger joint assembly 2, the middle finger joint assembly 3, and the distal finger joint assembly 4 in an open state by their own elastic force. When clamping the disc workpiece 49, the pneumatic slider 6 is driven to move the first finger joint assembly 2, the first finger joint clamping block 22 contacts the disc workpiece 49, and the first finger joint lower pressure spring rod 20 moves to the left, driving the first finger joint through the first pin 21. The crank rod 28 rotates clockwise around the bend, driving the middle finger joint assembly 3 to rotate clockwise around the upper end of the first finger joint L-shaped rod 14 via the middle finger joint transmission link 29. This causes the middle finger joint clamping block 40 to contact the disc workpiece 49. The middle finger joint lower compression spring rod 38 moves to the left, driving the middle finger joint crank rod 46 to rotate clockwise around the bend via the second pin 39. This causes the last finger joint assembly 4 to rotate clockwise around the upper end of the middle finger joint T-shaped rod 33 via the last finger joint transmission link 47. This causes the last finger joint clamping block 48 to contact the disc workpiece 49, achieving adaptive envelope gripping of the workpiece by the gripper. At this time, the first finger joint clamping block 22, the middle finger joint clamping block 40, and the last finger joint clamping block 48 are in close contact with the disc workpiece 49, so that the first spring 19, the second spring 26, the third spring 37, and the fourth spring 44 stop compressing due to external force and their extension is hindered by the workpiece, preventing further deformation and achieving self-locking of the gripper. By using a pneumatic slider 6 powered by a power source to drive the linkage of the first phalanx assembly 2, the middle phalanx assembly 3, and the last phalanx assembly 4, under-actuation based on the principle of under-rank mechanism is achieved. Figure 12 The diagram shows the state in which the first phalanx assembly 2, the middle phalanx assembly 3, and the last phalanx assembly 4 are fully open when the pneumatic slider 6 is located outside the cylinder. Figure 13 The state of the first finger joint assembly 2, the middle finger joint assembly 3, and the last finger joint assembly 4 fully adaptively enveloping and grasping the disc workpiece 49 when the pneumatic slider 6 is located inside the cylinder is given.

[0139] like Figure 14 and Figure 15 As shown, this invention provides a structural optimization method for a self-locking underactuated gripper, including establishing a gripper clamping contact force model, a gripper structural parameter optimization method, and a gripper structural parameter optimization process.

[0140] I. Establishment of the clamping contact force model of the gripper, including the following contents and steps:

[0141] (1) Establish the geometric and static models based on the structure of the clamp;

[0142] Given that the self-locking underactuated gripper has a symmetrical structure, the model is established and the structure is optimized by taking the left three-finger joint as an example. The geometric model primarily equates the driving link 8 in the driving mechanism 1 to a link AB, the first finger joint transmission link 9 to a link BC2, the first finger joint frame 11 to a quadrilateral C1C3C4E1, the first finger joint curved rod 28 to a folded rod QD2D3, the portion from the left end of the middle crossbar of the first finger joint frame 11 to the turning point of the first finger joint curved rod 28 to a link D1D2, the middle finger joint transmission link 29 to a link QP, the middle finger joint frame 30 to a quadrilateral E1E2E5G1, the middle finger joint curved rod 46 to a folded rod RE4E3, the portion from the left end of the middle crossbar of the middle finger joint frame 30 to the turning point of the middle finger joint curved rod 46 to a link E6E4, the last finger joint transmission link 47 to a link RU, and the last finger joint... The clamping block 48 is equivalent to quadrilateral G1G2G3G4. Since the first spring 19 and the second spring 26 are stretched and compressed synchronously and have the same deformation, the force on both is equivalent to that on spring D4D3 in the model calculation, and spring D4D3 is represented by s1. Similarly, the force on the third spring 37 and the fourth spring 44 is equivalent to that on spring E7E3, and spring E7E3 is represented by s2. The lengths of rods C1C3, D1D2, E1E2, G1U and E6E4 are defined as a1, a2, a3, a4 and a5, respectively. The lengths of rods E1B, G1E1, G1G4, D1B and E1E6 are defined as d1, d2, d3, d4 and d5, respectively. The lengths of rods D2D3, D2Q, PQ, E3E4, E4R and RU are defined as l1, l2, l3, l4, l5 and l6, respectively.

[0143] The static model mainly defines the torque of the driving mechanism 1 as T1, and the driving forces of the springs s1 and s2 as T2 and T3, respectively; defines the contact forces of the first phalanx assembly 2, the middle phalanx assembly 3, and the last phalanx assembly 4 that hold the object as F1, F2, and F3, respectively; defines the distance from point C1 to force F1 as h1, the distance from point E1 to force F2 as h2, and the distance from point G1 to force F3 as h3; and defines the angle between rods E2P and QP, and the angle between rod PQ and D2Q. Angles are defined as follows: the angles between rods G2U and RU, UR and E4R, and C4E1 and C1E1 are α1, α2, α3, α4, and α5, respectively; the angles between rod E1C1 and the horizontal line in the opposite direction are defined as follows: the angle between rod G1E1 and the line extending in the opposite direction of rod C1E1, and G4G1 and the line extending in the opposite direction of rod E1G1 are defined as β1, β2, and β3, respectively; the angles between rod C3C1 and the horizontal line, PE1 and the horizontal line, and UG1 and the horizontal line are defined as follows:

[0144] (2) Establish the virtual work equations for each finger joint of the gripper based on the principle of virtual work:

[0145] In the formula, Let v be the imaginary angular velocity of the torque T1 acting on the first phalanx. s1 v s2 These are the virtual velocities on springs s1 and s2, respectively; v F1 v F2 v F3 These are the virtual velocities of the contact forces F1, F2, and F3 at the point of contact, respectively.

[0146] Let T = [T1 F1 + T2 F2 + T3] T F = [F1 F2 F3] T , V F =[v F1 v F2 v F3 ] T The virtual work equation can be simplified to: F T V F =T T W.

[0147] (3) Establish the virtual velocity V of each finger joint of the gripper based on the rigid body velocity formula. F =[v F1 v F2 v F3 ] T for:

[0148]

[0149] In the formula, δ β1 δ β2 δ β3 These are the angular velocities for rotation angles β1, β2, and β3, respectively.

[0150] virtual velocity V F Written in matrix form: V F =J v [δ β1 δ β2 δ β3 ] T .

[0151] In the formula,

[0152] (4) Since both the middle finger joint transmission link 29 (PQ) and the end finger joint transmission link 47 (UR) exert direct forces on their respective finger joint assemblies, calculate the virtual velocity v of the two links. PQ v UR :

[0153]

[0154] because,

[0155]

[0156]

[0157]

[0158]

[0159] Therefore, the virtual velocity v of the middle finger joint transmission link 29 (PQ) and the end finger joint transmission link 47 (UR) PQ v UR for:

[0160]

[0161] For the five-bar linkage E1PQD2D1, with E1 and D1 as the positive x-axis and the direction pointing towards the disk workpiece as the positive y-axis, its vector closure equation is as follows:

[0162] Decompose it into x and y directions:

[0163] For α6+β2, Differentiate:

[0164]

[0165] Because α6 is a fixed angle, therefore δ α6 =0. Based on the angular velocity relationship of the same component, we can obtain: Let m be the term on the right side of the above equation, then the equation can be rearranged to obtain:

[0166] Similarly, for the five-bar linkage G1URE4E6, its vector closure equation is as follows:

[0167] Right now:

[0168] right Differentiating and rearranging, we get:

[0169]

[0170] Since α7 is a fixed angle, then δ α7 =0, based on the angular velocity relationship of the same component, we can obtain: Let n be the term on the right side of the above equation, then it can be rearranged to obtain:

[0171] because Will and Substituting the imaginary velocity v PQ v UR From the middle, and by sorting, we can obtain:

[0172] In the formula,

[0173]

[0174]

[0175] (5) Calculate the virtual velocities v on springs s1 and s2. s1 v s2 .

[0176] Based on the geometric relationships between structural components in the described geometric and static models of the clamp, it can be concluded that:

[0177]

[0178] Therefore, the virtual velocities on springs s1 and s2 are:

[0179] In the formula,

[0180]

[0181] (6) Calculate the contact force of the clamp F = [F1 F2 F3] T .

[0182] Based on the angular velocity relationship of the same component, we can obtain: Combined with the virtual velocities v on springs s1 and s2 s1 and v s2 The above W can be written in matrix multiplication form: W = J ω [δ β1 δ β2 δ β3 ] T .

[0183] In the formula,

[0184] virtual velocity V F Substituting W into the simplified virtual work equation, we get: F T J v =T T J ω .

[0185] The contact force is then:

[0186] In the formula, and

[0187]

[0188] Since the driving forces T2 and T3 of springs s1 and s2 are much smaller than the clamping force F, they can be ignored, and the clamping force F can be obtained:

[0189]

[0190] Further simplification yields F:

[0191] The above formula gives the contact force F = [F1 F2 F3] T The relationship between F and T1. From the equation, it can be seen that the contact force F is affected by β1~β3, The influence of equal angles and finger mechanism dimensions.

[0192] II. A method for optimizing the structural parameters of the gripper, including an immune optimization algorithm based on population effects. The immune evolutionary algorithm based on population effects is derived from the operators (including the immune selection operator O) of the basic immune optimization algorithm. s Immune crossover operator O c and immune variant operator O m Based on this, a new immune aggregation operator O was designed according to the population effect. g and immune diffusion operator O d Optimize and improve the algorithm.

[0193] While basic immune algorithms possess distributed, global optimization capabilities, they also exhibit limitations when facing multivariate optimization, including effectiveness in local search and a tendency to get trapped in local conditions. As can be seen from the contact force model of the aforementioned gripper, this structure has approximately 10 variables to be optimized, thus placing higher demands on the algorithm's optimization capabilities. To address this, this invention draws upon the group effect in social development, where an individual's behavior changes under the influence of a group, such as clustering behavior based on centripetal force and diffusion behavior based on competition.

[0194] Given a population A(k) with n individuals in the kth generation, where A(k) = [a1(k), a2(k), ..., a n [(k)], then the immune selection operator O s It can be described as:

[0195]

[0196] Immune crossover operator O c It can be described as:

[0197] Immune Mutation Operator O m It can be described as:

[0198] The immune aggregation operator O g mainly enables the dominant individuals in the population to form an aggregation population to have a call and influence on the inferior individuals with poor fitness, thereby improving the performance of the inferior individuals.

[0199] Let the aggregation number be m, the aggregation distance be l (l < n), and the number of inferior individuals with poor fitness be n. The process of the immune aggregation operator is as follows:

[0200] (1) Select the individual a*(k) with the best fitness from the population A″′(k) after immune mutation;

[0201] (2) Generate m dominant individuals whose aggregation distance from a*(k) is less than l, and form an aggregation population |a * -g i (k)| ≤ l, where |·| represents the Hamming distance;

[0202] (3) Select z individuals with the worst fitness from the population A″′(k), and form an inferior population W(k) = [w1(k), w2(k), …, w z (k)];

[0203] (4) Extract the individual w i (k) (i ∈ [1, z]), perform an exclusive OR operation on it with the individuals in G(k) respectively, and obtain G'(k) = [g'1(k), g'2(k), …, g' m (k)];

[0204] (5) Extract the optimal individual in G'(k) = [g'1(k), g'2(k), …, g' m (k)] and compare it with w i (k). If the former is better than the latter, replace the latter, otherwise retain the latter; <​​​​​​​​​​​​​, mainly to let the individuals with high concentration in the population diffuse to prevent individuals from falling into local minima.

[0209] Let the diffusion distance be r (r < n), the diffusion number be s, and the process of the immune diffusion operator is as follows:

[0210] (1) Select the s antibodies with the highest concentration from the population A IV (k) after immune aggregation, and form the diffusion population D(k) = [d1(k), d2(k), …, d s (k)];

[0211] (2) Randomly generate an initial individual a 0 (k), and the number of its elements that are 1 is greater than r and less than or equal to n;

[0212] (3) Take out the individual d i (k) (i ∈ [1, s]) from D(k) and perform an exclusive OR operation with the individual a 0 (k), and obtain a new individual d i '(k);

[0213] (4) Compare the individual d i (k) with d i '(k). If the latter is better than the former, replace the former; otherwise, retain the former;

[0214] (5) Determine whether all antibodies in D(k) have completed the exclusive OR operation with a 0 (k)? If not, go to step (3); otherwise, exit.

[0215] The immune diffusion operator O d can be described as:

[0216]

[0217] III. The optimization process of the gri parameters of the gripper structure parameters includes the following contents and steps:

[0218] (1) Based on the clamping force F of the gripper and with the goal of making the contact force as evenly and equally distributed as possible during clamping, establish the objective function for parameter optimization in the stable clamping state of the gripper:

[0219] minf(X) = min((F1 - F2) 2 +(F1 - F3) 2 +(F2 - F3) 2 )

[0220] In the formula, X is the set of gripper structure parameter variables and

[0221] (2) Set the constraint range of the clamp parameter variable set X;

[0222] (3) Initialize the parameters of the immune optimization algorithm based on population effects, and the initial population A(k) = [a1(k), a2(k), ..., a n [(k)], k←0;

[0223] (4) Immune selection: A′(k)←O s (A(k))=[a1′(k),a2′(k),…,a n ′(k)];

[0224] (5) Immune crossover: A″(k)←O c (A′(k))=[a1″(k),a2″(k),…,a n "(k)];

[0225] (6) Immune variation: A″′(k)←O m (A″(k))=[a1″′(k),a2″′(k),…,a n "′(k)];

[0226] (7) Immune accumulation:

[0227] (8) Immune diffusion:

[0228] (9) Termination condition determination. Has the number of generations k reached the maximum? If so, the algorithm terminates and outputs the optimal variable X. * Otherwise, k←k+1, and return to step (4).

[0229] Taking the gripping of a circular workpiece with a minimum diameter of 70mm as an example, this paper designs a self-locking underactuated gripper structure using the empirical method, Fmincon method, Genetic Algorithm (GA), and the Immune Optimization Algorithm Based on Population Effect (IOABOPE) of this invention. Table 1 presents the design data. As can be seen from the table, compared to the empirical method, the objective function values ​​of the three optimization methods (Fmincon, GA, and IOABOPE) are much smaller, and the differences in the three contact forces of each algorithm are also smaller than those of the empirical method, demonstrating the importance of optimization methods in multivariate structural design. Among the three optimization methods, GA and IOABOPE, which have distributed and global optimization capabilities, outperform Fmincon in both objective function values ​​and the differences in contact forces. This is mainly because Fmincon is a local optimization method and does not have an advantage for multivariate optimization. Compared with GA, IOABOPE of the present invention is undoubtedly the best. Not only is the objective function value the smallest, but the three contact forces are also relatively close. This is mainly due to the immune clustering operator improving the local optimization ability of the algorithm, while the immune diffusion operator avoids the algorithm from getting trapped in local minima too early, which effectively improves the optimization effect of the algorithm. This also verifies the effectiveness and superiority of the optimization method proposed in this invention.

[0230] Table 1:

[0231]

[0232] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A self-locking under-actuated gripper comprising a drive mechanism (1), characterized in that, The upper end surface of the driving mechanism (1) is provided with mirror-symmetrical clamping mechanisms, which are connected from bottom to top by the first knuckle assembly (2), the middle knuckle assembly (3) and the last knuckle assembly (4). The driving mechanism (1) comprises a cylinder body (5), the upper end surface of the cylinder body (5) is provided with mirror-symmetrical pneumatic sliders (6) which are isolated left and right, the pneumatic sliders (6) are fixedly connected with transmission sliders (7) through bolts, the lower end of a driving link (8) is rotatably connected to the upper side of the transmission slider (7), the lower end of a first knuckle transmission link (9) is rotatably connected to the upper end of the driving link (8), the rear end of the cylinder body (5) is fixedly provided with mirror-symmetrical support arms (10) corresponding to the transmission slider (7), and the upper end of the first knuckle transmission link (9) is rotatably connected with the rotation shaft of the upper end of the support arm (10). The first phalanx assembly (2) comprises a first phalanx frame (11), the middle of the lower edge of the first phalanx frame (11) is rotationally connected with the rotation shaft of the upper end of the support arm (10), the first phalanx frame (11) is sequentially clamped and fixed with the first phalanx lower guide (12), the first phalanx upper guide (13) and the first phalanx L-shaped rod (14) from bottom to top by bolts, the upper end of the first phalanx L-shaped rod (14) is rotationally connected with the left end of the arc-shaped part of the middle phalanx tripod (15), the first phalanx lower guide (12) comprises the first I-shaped piece (16) and the second I-shaped piece (17) which are parallel to each other, the first I-shaped piece (16) and the second I-shaped piece (17) are respectively fixed between the left side frame and the right side frame of the first phalanx frame (11), the first I-shaped piece (16) and the second I-shaped piece (17) are clamped and fixed with the first guide pipe (18) which is closed at the left end and open at the right end, the first guide pipe (18) is provided with the first spring (19) therein, the right end of the first spring (19) is supported on the left end part of the first phalanx lower compression spring rod (20), the left end of the first phalanx lower compression spring rod (20) is further provided with the first pin shaft (21) which is perpendicular to the axis of the first phalanx lower compression spring rod (20), the first pin shaft (21) moves leftward and rightward in the groove of the first guide pipe (18) along the axial direction, the right end of the first phalanx lower compression spring rod (20) is fixed on the left lower part of the first phalanx clamping block (22), the first phalanx upper guide (13) comprises the third I-shaped piece (23) and the fourth I-shaped piece (24) which are parallel to each other, the third I-shaped piece (23) and the fourth I-shaped piece (24) are also respectively fixed between the left side frame and the right side frame of the first phalanx frame (11), the third I-shaped piece (23) and the fourth I-shaped piece (24) are clamped and fixed with the second guide pipe (25) which is closed at the left end and open at the right end, the second guide pipe (25) is provided with the second spring (26) therein, the right end of the second spring (26) is supported on the left end part of the first phalanx upper compression spring rod (27), the right end of the first phalanx upper compression spring rod (27) is fixed on the left upper part of the first phalanx clamping block (22), the first phalanx lower compression spring rod (20) and the first phalanx upper compression spring rod (27) jointly support the first phalanx clamping block (22), the middle horizontal rod of the first phalanx frame (11) is rotationally connected with the turning part of the first phalanx curved rod (28), the first pin shaft (21) is embedded in the lower end slot of the first phalanx curved rod (28) and can slide along the slot, the upper end of the first phalanx curved rod (28) is rotationally connected with the lower end of the middle phalanx transmission connecting rod (29). The middle finger joint assembly (3) comprises a middle finger joint frame (30) which is fixed by bolts from bottom to top in sequence with a middle finger joint tripod (15), a middle finger joint lower guide (31), a middle finger joint upper guide (32) and a middle finger joint T-shaped rod (33), the right end of the arc-shaped part of the middle finger joint tripod (15) is rotatably connected with the upper end of a middle finger joint transmission connecting rod (29), the middle finger joint lower guide (31) and the first finger joint lower guide (12) are the same in structure and comprise a fifth I-shaped piece (34), a sixth I-shaped piece (35), a third guide pipe (36), a third spring (37), a middle finger joint lower pressing spring rod (38) and a second pin shaft (39), the right end of the middle finger joint lower pressing spring rod (38) is fixed to the lower left part of a middle finger joint clamping block (40), the middle finger joint upper guide (32) and the first finger joint upper guide (13) are the same in structure and comprise a seventh I-shaped piece (41), an eighth I-shaped piece (42), a fourth guide pipe (43), a fourth spring (44) and a middle finger joint upper pressing spring rod (45), the right end of the middle finger joint upper pressing spring rod (45) is fixed to the upper left part of the middle finger joint clamping block (40), the middle finger joint lower pressing spring rod (38) and the middle finger joint upper pressing spring rod (45) jointly support the middle finger joint clamping block (40), the middle of the middle finger joint frame (30) is rotatably connected with the turning part of a middle finger joint curved rod (46), the lower end slot of the middle finger joint curved rod (46) is embedded with the second pin shaft (39) which can slide along the slot, the upper end of the middle finger joint curved rod (46) is rotatably connected with the lower end of a last finger joint transmission connecting rod (47); The last finger joint assembly (4) comprises a last finger joint clamping block (48), the lower right end of the last finger joint clamping block (48) is rotatably connected with the upper end of the last finger joint transmission connecting rod (47), the lower left end of the last finger joint clamping block (48) is rotatably connected with the upper end of the middle finger joint T-shaped rod (33); The last finger joint assembly (4) comprises a last finger joint clamping block (48), the lower left end of the last finger joint clamping block (48) is rotatably connected with the upper end of the middle finger joint T-shaped rod (33), the lower right end of the last finger joint clamping block (48) is rotatably connected with the upper end of the last finger joint transmission connecting rod (47).

2. A self-locking under-actuated gripper according to claim 1, wherein: The first finger joint clamping block (22) is a concave structural member comprising a mounting surface and a clamping surface, and the inner side of the concave part is arc-shaped.

3. The self-locking underactuated gripper of claim 1, wherein: The middle finger joint clamping block (40) is a concave structural member comprising a mounting surface and a clamping surface, and the inner side of the concave part is arc-shaped.

4. The self-locking underactuated gripper of claim 1, wherein: The last finger joint clamping block (48) is a knife-shaped structural member comprising a mounting end and a clamping end, the knife handle part for mounting is provided with two connecting holes, and the blade part for clamping is a concave structure, and the inner side of the concave part is arc-shaped.

5. The self-locking underactuated gripper of claim 1, wherein: The clamping surfaces of the first finger joint clamping block (22), the middle finger joint clamping block (40) and the last finger joint clamping block (48) are all provided with an anti-impact and anti-slip layer.

6. A method for optimizing the structure of a self-locking underactuated gripper as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: I. The establishment of the clamping contact force model comprises the following contents and steps: (1) Establishing geometric model and static model according to the structure of the gripper; In view of the left-right symmetrical structure of the self-locking under-actuated gripper, the model is established and the structure is optimized by taking the three fingers of the left side as an example; the geometric model is established by equivalent the driving link (8) in the driving mechanism (1) to AB rod, the first finger joint transmission link (9) to BC2 rod, the first finger joint frame (11) to C1C3C4E1 quadrilateral, the first finger joint crank (28) to QD2D3 crank, the part from the left end of the middle horizontal rod in the first finger joint frame (11) to the turning part of the first finger joint crank (28) to D1D2 rod, the middle finger joint transmission link (29) to QP rod, the middle finger joint frame (30) to E1E2E5G1 quadrilateral, the middle finger joint crank (46) to RE4E3 crank, the part from the left end of the middle horizontal rod in the middle finger joint frame (30) to the turning part of the middle finger joint crank (46) to E6E4 rod, the last finger joint transmission link (47) to RU, and the last finger joint clamping block (48) to G1G2G3G4 quadrilateral; since the first spring (19) and the second spring (26) are synchronously stretched and compressed, and the deformation amount is the same, the forces of the two are equivalent to the spring D4D3 in the model calculation, and s1 represents the spring D4D3; similarly, the forces of the third spring (37) and the fourth spring (44) are equivalent to the spring E7E3, and s2 represents the spring E7E3; the lengths of the rods C1C3, D1D2, E1E2, G1U and E6E4 are defined as a1, a2, a3, a4 and a5 respectively; the lengths of the rods E1B, G1E1, G1G4, D1B and E1E6 are defined as d1, d2, d3, d4 and d5 respectively; the lengths of the rods D2D3, D2Q, PQ, E3E4, E4R and RU are defined as l1, l2, l3, l4, l5 and l6 respectively; the static model is established by defining the torque of the driving mechanism (1) as T1, the driving forces of the springs s1 and s2 as T2 and T3 respectively, the contact forces of the first finger joint assembly (2), the middle finger joint assembly (3) and the last finger joint assembly (4) for clamping objects as F1, F2 and F3 respectively, the distance of the point C1 from the force F1 as h1, the distance of the point E1 from the force F2 as h2, and the distance of the point G1 from the force F3 as h3; the angles between the rod E2P and the rod QP, the rod PQ and the rod D2Q, the rod G2U and the rod RU, the rod UR and the rod E4R, and the rod C4E1 and the rod C1E1 are defined as α1, α2, α3, α4, α5 respectively; the angles between the rod E1C1 and the horizontal reverse line, the rod G1E1 and the reverse extension line of the rod C1E1, and the rod G4G1 and the reverse extension line of the rod E1G1 are defined as β1, β2, β3 respectively; the angles between the rod C3C1 and the horizontal line, the rod PE1 and the horizontal line, and the rod UG1 and the horizontal line are defined as φ1, φ2, φ3 respectively; (2) The virtual work equations of each finger segment of the gripper are established based on the virtual work principle: ; in the formula, ω φ1 is the virtual angular velocity of the moment T1 acting on the first finger segment, v s1 , v s2 are the virtual velocities of springs s1 and s2 respectively; v F1 , v F2 , v F3 are the virtual velocities of contact forces F1, F2 and F3 at the contact points respectively; Let T = [T1 F1 + T2 F2 + T3] T F = [F1 F2 F3] T W = [ω φ1 v s1 v s2 ] T V F =[v F1 v F2 v F3 ] T The equation for virtual work can be simplified to: ; (3) The virtual velocity V of each finger segment of the gripper is established based on the rigid body velocity formula F = v F1 v F2 v F3 ] T is: ； wherein , δ β1 , δ β2 , δ β3 are angular velocities of the angles β1, β2and β3, respectively; The virtual velocity V F in matrix form: ; In the formulae, ; (4) Since the middle finger joint transmission link (29) and the last finger joint transmission link (47) have direct force on the finger joint assembly, the virtual velocities v PQ 、 v UR of the two links are calculated ； because, ， ， ， ， Therefore, the virtual velocity v of the middle finger joint transmission connecting rod (29) and the virtual velocity v of the last finger joint transmission connecting rod (47) are: PQ , UR , ; For five-bar mechanism E1PQD2D1, E1D1 is the positive direction of x-axis, and the direction of disc workpiece is the positive direction of y-axis. The vector closed equation is listed as follows: ; Decompose it into x, y direction: ; The derivation of α6+β2, α2-α1+φ2-φ1 is: ； Because α6 is a fixed angle, δ α6 = 0, according to the same component angular velocity relationship, we can get: δ φ2 = -δ β2 = -δ β1 ; let the right side of the above equation be m, then the above equation can be arranged as: ; Again for the five-bar linkage G1URE4E6, its vector closure equation is listed: ; That is, ; The derivation of α7+β3, α6-α4+α3+φ2-φ3 is, and the arrangement can be obtained: ； Since α7 is a fixed angle, then δ α7 = 0, according to the same component angular velocity relationship, we have δ φ3 = - δ β3 = - δ β2 = - δ β1 ; let the right side of the equal sign of the above equation be n, then it can be arranged as: ; Since δ φ2 = -δ β2 = -δ β1 = -δ φ3 = -δ β3 = -δ β2 = -δ β1 , δ α2-α1+φ2 and δ α4-α3+φ3 are substituted into the virtual velocities v PQ , v UR , and the equation is arranged, we have: ; In the formulae, , ， ， ； (5) Calculate the virtual velocity v on springs s1 and s2 s1 , v s2 ; According to the geometric model and the static model of the structure, the geometric relationship between the structure members can be obtained: , ; So the virtual velocities on springs s1 and s2 are: ; In the formulae, , , ， ； (6) Calculate gripper contact forces F = [F1 F2 F3] T ; From the same component angular velocity relationship, we can get: again combined with the virtual velocity v s1 and v s2 , we can write the above W as a matrix multiplication form: ; In the formulae, , Substitute the virtual velocity V F into the simplified virtual work equation, we get: , The contact force is then: wherein , and , , , ， ， ； Since the driving forces T2 and T3 of the springs s1 and s2 are much smaller than the clamping force F, they are ignored and the clamping force F is obtained: ​ Further simplification gives F: ; The above equation gives the contact force F = [F1 F2 F3] T The relationship between T1 and F can be seen from the equation, the contact force F is affected by angles β1~β3, φ1~φ3, and the size of the finger mechanism. II. The method for optimizing the structure parameters of the gripper, comprising an immune optimization algorithm based on group effect, wherein the immune evolution algorithm based on group effect is designed with a new immune aggregation operator O g and an immune diffusion operator O d to perform algorithm optimization and promotion; A(k) = [a1(k), a2(k), ∙∙∙, an(k)], where a1(k), a2(k), ∙∙∙, an(k) are the individuals of the population A(k) of the k-th generation. n (k)], then the immune selection operator O s can be described as: , i e [1, n], , Immune crossover operator O c Can be described as: , i∈[1, n], , Immune variation operator O m Can be described as: , i∈[1, n], ; The immune clustering operator O g is to let the dominant individuals in the population form a clustering population to have a call impact on the inferior individuals with poor fitness, and then improve the performance of the inferior individuals. Let the number of clusters be m, the cluster distance be l (l<n), the number of inferior individuals of fitness difference be n, and the flow of the immune clustering operator be: (1) Selecting the best individual a*(k) from the immune varied population of fitness. (2) Generate m dominant individuals with their clustering distance less than l from a*(k) and form the clustering population G(k) = [g1(k), g2(k), …, g m (k)], |·| denotes Hamming distance; (3) Select z worst individuals from the population W(k) = [w1(k), w2(k),…, w z (k)] from the population P(k) = [p1(k), p2(k),…, p n(k)] (4) Extract individual w from W(k) i (k)(i [1, z], XOR with individual in G(k) respectively, and get G'(k) = [g'1(k), g'2(k), …, g' m (k)]; (5) Extract G'(k) = [g'1(k), g'2(k), …, g'N(k)] from G(k) = [g1(k), g2(k), …, gN(k)] where g'n(k) is the best individual in G'(k) and w is a weight factor. m (k) is replaced by g'n(k) if g'n(k) is better than g'n(k), otherwise g'n(k) is kept. i (k) is replaced by g'n(k) if g'n(k) is better than g'n(k), otherwise g'n(k) is kept. (6) Determine whether all individuals in W(k) complete the XOR operation with individuals in G(k), if not, go to step (4), otherwise, exit; Immunoaggregation operator O g Can be described as: , i e [1, n], ; The immunodiffusion operator O d is to let the high concentration individuals in the population diffuse to prevent individuals from falling into local minima; Let the diffusion distance be r (r<n), the diffusion number be s, and the flow of the immune diffusion operator be: (1) From the immune-aggregated population A IV (k) the s antibodies with the highest concentrations are selected and form the diffusion population D(k) = [d1(k), d2(k), …, d s (k)]. (2) randomly generate 1 initial individual a 0 (k) and the number of elements of 1 is greater than r and less than or equal to n; (3) Take individual d from D(k) i (k) (i [1, s] and individual a 0 (k) and get new individual d i '(k); (4) Compare individual d i (k) with d i '(k) and replace d if d '(k) is better than d, otherwise keep d. (5) Determine whether all antibodies in D(k) are associated with a 0 (k) Complete the XOR operation, if not, go to step (3), otherwise exit. Immune diffusion operator O d Can be described as: , i e [1, n], ; Three, the structure parameter optimization process of the gripper, including the following contents and steps: (1) Based on the clamping force F of the gripper, and taking the target of making the contact force as evenly distributed and equal as possible during clamping, the objective function of parameter optimization in the stable clamping state of the gripper is established: ； where X is the set of gripper structure parameter variables and X = [x1x2x3x4x5x6x7x8x9x 10 x 11 x 12 x 13 x 14 x 15 ]=[a2 a5 h1 h2 h3 l2 l3 l5 l6 β1 β2 β3 φ1 φ2 φ3] (2) Set the constraint range of the parameter variable set X of the gripper; (3) initialize the parameters of the immune optimization algorithm based on group effect, and the initial population A(k) = [a1(k), a2(k), ∙∙∙, a n (k)], k <- 0; (4) immune selection: ; (5) Immune cross: ; (6) Immune variation: ; (7) immunocytokines: ; (8) Immunodiffusion: ; (9) Termination condition judgment, whether the evolution generation k reaches the maximum generation, if yes, the algorithm terminates, and the optimal variable X* is output; otherwise, k←k+1, and return to step (4).

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