Mechanical arm tail end multi-point flexible gripping apparatus and gripping method for heavy workpieces

Abstract

The invention provides a mechanical arm tail end multi-point flexible gripper for heavy workpieces and a gripping method, and belongs to the field of heavy workpiece gripping. The problems that in the process that an existing mechanical arm carries heavy workpieces, a tail end gripper is poor in clamping stability, poor in accuracy and low in bearing capacity are solved. The clamping device comprises a mechanical arm assembly, a truss structure assembly and a flexible moving platform assembly, the position and posture of a tail end gripping apparatus are adjusted through a mechanical arm, connection of the clamping device and a traction bolt on a large-size heavy workpiece assembly is completed through ball movement of a thrust ball bearing under the guidance of the clamping device and chamfers of the traction bolt, and the clamping device and the traction bolt are clamped. And the clamping device and the traction bolt are locked by air pressure. The mechanical arm can carry large-size heavy workpieces, the stability and reliability of the workpieces in the carrying process are guaranteed, the absolute positioning precision of the mechanical arm can be flexibly compensated, the carrying efficiency and safety of the large-size heavy workpieces are improved, and application of unmanned and intelligent factories is further promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy workpiece grasping, and in particular, to a multi-point flexible gripper at the end of a robotic arm for heavy workpieces and a grasping method. Background Art

[0002] With the advancement of China's manufacturing industry towards unmanned and intelligent production, robotic arms have become an important driving force for the transformation and upgrading of modern manufacturing due to their advantages of effectively improving production efficiency, reducing costs, enhancing product quality and safety. In industrial scenarios with high intensity, high stability or large load-bearing capacity, the handling of large-sized heavy workpieces usually relies on truss equipment, which has problems such as large space requirements for truss equipment operation, high consumption of human resources, low work efficiency, high risk factor, and low flexibility. Therefore, using robotic arms to handle large-sized heavy workpieces has become a development trend. However, the commonly used grippers at the end of robotic arms combine mechanical structures and hydraulic systems, which have problems such as complex structures, large space occupation, low grasping accuracy, and high costs. The commonly used pneumatically driven grippers at the end of robotic arms use flexible structures, although they can effectively improve the grasping accuracy, but they are difficult to handle the weight and size of heavy workpieces.

[0003] During the process of using a robotic arm to handle large-sized heavy workpieces, the robotic arm faces problems of stability during handling, clamping accuracy, and high load-bearing capacity:

[0004] First, the working area of the commonly used end effector of a robotic arm is relatively small compared to the clamping surface area of the workpiece. During handling, the anti-interference ability is poor, and it is difficult to achieve stability during handling. It is easy to generate additional overturning moments, causing the robotic arm to fatigue, and even directly causing damage exceeding the load-bearing capacity of the robotic arm, resulting in safety accidents. Therefore, a gripper device at the end of a robotic arm is needed to select multiple clamping points on the clamping surface of the workpiece for grasping to improve the stability of large-sized heavy workpieces during handling;

[0005] Second, due to the absolute positioning accuracy of the commonly used robotic arm during operation, the grasping accuracy is low. When grasping large-sized heavy workpieces, it is necessary to ensure that each clamping point is quickly and accurately connected before carrying out the handling work. To ensure work efficiency and safety, the entire working process of the robotic arm needs to be completed without additional human assistance. Therefore, a flexible gripper device at the end of a robotic arm is needed to compensate for the absolute positioning error of the robotic arm and meet the quick and accurate grasping of each clamping point;

[0006] Thirdly, during the process of handling large-sized heavy workpieces, pneumatic drive is required. The maximum handling weight of the commonly used pneumatic-driven heavy-duty hook claws does not exceed 300 kg, which cannot meet the requirement that the weight of heavy workpieces can reach up to 800 kg. Due to the cumulative effect of errors, the end effector of the robotic arm cannot use too many clamping points. However, fewer clamping points will cause each clamping point to bear a large load, and it is required to be able to lock self-locked for 2 hours after cutting off the air supply to prevent the heavy workpiece being grabbed from falling and causing safety accidents. Therefore, a robotic arm end gripper device with high load-bearing capacity is needed.

[0007] Aiming at the problems of poor clamping stability, poor accuracy and low load-bearing capacity of the end gripper during the process of the robotic arm handling heavy workpieces, the present invention designs a multi-point flexible gripper device for the end of the robotic arm of heavy workpieces, which is used to realize the stable, accurate and rapid handling of large-sized heavy workpieces by the robotic arm. Summary of the Invention

[0008] The technical problem to be solved by the present invention is:

[0009] To solve the problems of poor clamping stability, poor accuracy and low load-bearing capacity of the end gripper during the process of the existing robotic arm handling heavy workpieces.

[0010] The technical solution adopted by the present invention to solve the above technical problems:

[0011] The present invention provides a multi-point flexible gripper for the end of the robotic arm of heavy workpieces, which includes a robotic arm assembly, a truss structure assembly and a flexible moving platform assembly.

[0012] The truss structure assembly includes the workpiece end of the quick-change assembly, a truss structure, a pneumatic pressure-holding valve and an air pipe; the robotic arm end of the quick-change assembly is connected to the robotic arm assembly, the workpiece end of the quick-change assembly is arranged at the middle position of the top of the truss structure, and the truss structure is a cuboid structure; the air pipe is fixed to the truss structure; three pairs of evenly distributed connecting seats are symmetrically arranged on both sides of the truss structure along the length direction, and each connecting seat is provided with a pneumatic pressure-holding valve and a flexible moving platform assembly. The air source is first connected to the pneumatic pressure-holding valve and then enters the flexible moving platform assembly to ensure self-locking when the air source is interrupted.

[0013] Each flexible moving platform assembly includes an end cover, a flexible platform support seat, a thrust ball bearing, a flexible platform moving shaft, a clamp fixed end and a clamp.

[0014] The flexible platform support base is a cylindrical structure with an open upper end. The flexible platform support base is arranged on the connecting seat of the truss structure, and the upper end of the flexible platform support base is connected to the end cover through a flange; the flexible platform moving shaft is a cylindrical structure with a limiting frustum on the outside. The flexible platform moving shaft sequentially penetrates through the central positions of the flexible platform support base and the connecting seat and then is connected to the fixed end of the clamp. Thrust ball bearings are arranged on both the upper and lower sides of the limiting frustum of the flexible platform moving shaft, and the thrust ball bearings on both the upper and lower sides can freely move synchronously within the spatial critical range in the radial direction;

[0015] The lower frustum of the fixed end of the clamp is connected to the clamp. The clamp is provided with a chamfer. A cavity is provided at the center of the bottom of the clamp, and the cavity is used to lock the traction bolt on the heavy workpiece assembly by air pressure. The traction bolt is provided with a chamfer; when the robotic arm assembly moves downward, the clamp and the traction bolt, under the guidance of the chamfer, enable the clamp connected to the flexible platform moving shaft to move within the spatial critical range in the radial direction of the central hole at the bottom of the flexible platform support base.

[0016] Further, the robotic arm assembly includes a robotic arm, a six-axis force sensor, and the robotic arm end of the quick-change assembly; the robotic arm is used to realize the displacement and attitude adjustment of the multi-point flexible gripper. The end of the robotic arm is connected to the six-axis force sensor, the six-axis force sensor is connected to the robotic arm end of the quick-change assembly, and the robotic arm end of the quick-change assembly is connected to the workpiece end of the quick-change assembly.

[0017] Further, the air pipe is used to provide a gas source with a pressure not lower than 0.5 MPa for the flexible mobile platform assembly.

[0018] Further, when the gas source is interrupted, the pneumatic pressure-holding valve ensures that the flexible mobile platform assembly is self-locked within 2 h.

[0019] Further, an anti-wear gasket is also included. An anti-wear gasket is provided between the roller of the upper thrust ball bearing and the end cover, and an anti-wear gasket is provided between the roller of the lower thrust ball bearing and the bottom of the flexible platform support base. The thrust ball bearings on both the upper and lower sides can freely move relative to the anti-wear gasket within the spatial critical range in the radial direction, and the spatial critical value is 2 mm.

[0020] Further, a locknut is also included. The cavity of the flexible platform moving shaft and the connecting column of the fixed end of the clamp are connected by M12 threads. The flexible platform moving shaft and the fixed end of the clamp are connected and fixed from above by the locknut, and the threads of the locknut and the fixed end of the clamp have the same helix direction.

[0021] Further, the clamp is provided with a 2-mm chamfer, and the traction bolt is provided with a 1-mm chamfer, which is used to compensate for the absolute positioning error of the robotic arm of 1.5 mm.

[0022] Further, a clamping plate fixed side is sleeved at the bottom of the connecting seat, and a clamping plate moving side is sleeved on the bottom circular platform of the fixed end of the clamping device. The clamping plate fixed side and the clamping plate moving side are in contact and can slide relative to each other; annular magnets are arranged at the relative positions above the clamping plate fixed side and below the clamping plate moving side to ensure that the flexible platform moving shaft is always located at the center of the displacement area through a pair of annular magnets in the non-working state.

[0023] A grasping method for a multi-point flexible gripper at the end of a robotic arm for heavy workpieces includes the following steps:

[0024] When grasping, the position and posture of the end gripper of the robotic arm are adjusted to make the flexible moving platform components of the six clamping points located above each clamping point, and the flexible moving platform components are driven to move vertically downward. Under the guidance of the 2-mm chamfer of the clamping device and the 1-mm chamfer of the traction bolt, the clamping device is connected to the traction bolt on the large-size heavy workpiece component through the rolling balls of the thrust ball bearing, and the clamping device and the traction bolt are locked by air pressure.

[0025] The end gripper of the robotic arm is displaced upward by a unit distance. If no step torque appears in the six-axis force sensor, it proves that the clamping devices at each clamping point are all locked and connected to the traction bolts, and the grasping process is completed.

[0026] Further, if the air source is interrupted during the working process, the pneumatic pressure maintaining valve is relied on to ensure that the multi-point flexible gripper device is self-locked within 2 hours.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The present invention provides a multi-point flexible gripper device for realizing the stable and rapid handling of large-size heavy workpieces by a robotic arm driven by air pressure and self-locking when the air source is interrupted.

[0029] (2) The present invention adopts a six-point clamping and releasing device on the large-size clamping surface of the heavy workpiece, which can ensure the anti-interference ability of the large-size heavy workpiece during the handling process by the robotic arm and realize the stability during the handling process.

[0030] (3) The present invention adopts a unique flexible moving platform, which can effectively compensate for the absolute positioning error of 1.5 mm of the robotic arm during the downward grasping process, making the grasping process more accurate and efficient, avoiding the cumulative error problem caused by too many clamping points, and the problem of poor stability caused by large load on a single clamping point due to too few clamping points.

[0031] (4) The flexible platform moving shaft of the present invention can achieve flexible connection within a circular area with a radius of 2 mm and has a load-bearing capacity of more than 134 kg.

[0032] (5) The present invention uses anti-loosening bolts, and the thread directions of the anti-loosening bolts and the fixed end of the clamp are the same, effectively ensuring the connection reliability between the flexible platform moving shaft and the fixed end of the clamp, and enhancing the anti-interference ability of the flexible moving platform.

[0033] (6) The truss structure of the present invention is welded from Q235 steel plates, with a safety factor of 1.5. During the process of handling large-size heavy workpieces with a mass of 800 kg, the maximum equivalent stress of the truss structure is 58.3 MPa, and the maximum deformation is 339 μm, which is significantly less than the allowable stress of 157 MPa, meeting the strength requirements. Description of the Drawings

[0034] Figure 1 It is a perspective view of a multi-point flexible gripper at the end of the robotic arm and a heavy workpiece assembly in an embodiment of the present invention;

[0035] Figure 2 It is a perspective view of a truss structure assembly and a flexible moving platform assembly in an embodiment of the present invention;

[0036] Figure 3 It is a schematic structural diagram of a flexible moving platform assembly in an embodiment of the present invention;

[0037] Figure 4 It is a bottom view of a truss structure in an embodiment of the present invention;

[0038] Figure 5 It is an equivalent stress nephogram of a truss structure in an embodiment of the present invention;

[0039] Figure 6 It is a total deformation nephogram of a truss structure in an embodiment of the present invention.

[0040] Description of the Reference Numerals:

[0041] 1. Robotic arm assembly; 2. Truss structure assembly; 3. Flexible moving platform assembly; 4. Heavy workpiece assembly; 11. Robotic arm; 12. Six-axis force sensor; 13. Robotic arm end of the quick-change assembly; 21. Workpiece end of the quick-change assembly; 22. Truss structure; 23. Pneumatic pressure maintaining valve; 301. Flexible platform support seat; 302. End cover; 303. Anti-loosening bolt; 304. Flexible platform moving shaft; 305. Anti-wear gasket; 306. Thrust ball bearing; 307. Ring magnet; 308. Fixed side of the splint; 309. Moving side of the splint; 310. Fixed end of the clamp; 311. Clamp; 41. Traction bolt; 42. Heavy workpiece. Detailed Embodiments

[0042] In the description of the present invention, it should be noted that the terminology nouns in the various embodiments, such as "up", "down", "front", "back", "left", "right", etc., which indicate directions, are only for simplifying the description of the positional relationship based on the drawings in the specification, and do not mean that the referred elements and devices must be operated according to the specific directions and defined operations and methods and structures in the specification. Such directional nouns do not constitute a limitation on the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0044] Specific implementation plan 1: Combine Figures 1 to 4 As shown, the present invention provides a multi-point flexible gripper at the end of a mechanical arm for a heavy workpiece, comprising a mechanical arm component 1, a truss structure component 2, a flexible mobile platform component 3 and a heavy workpiece component 4.

[0045] The mechanical arm assembly 1 includes a mechanical arm 11, a six-dimensional force sensor 12 and a mechanical arm end 13 of a quick-change assembly; the mechanical arm 11 is used to achieve 360° displacement of the multi-point flexible gripper, the end of the mechanical arm 11 is connected to the six-dimensional force sensor 12, and the six-dimensional force sensor 12 is connected to the mechanical arm end 13 of the quick-change assembly;

[0046] The truss structure assembly 2 includes a workpiece end 21 of a quick-change assembly, a truss structure 22, a pneumatic pressure-maintaining valve 23 and an air pipe; the mechanical arm end 13 of the quick-change assembly is connected to the workpiece end 21 of the quick-change assembly, and the workpiece end 21 of the quick-change assembly is arranged at the middle position of the top end of the truss structure 22. The truss structure 22 is a rectangular structure, which is an existing truss structure; the air pipe is fixed to the truss structure 22 according to the set air path, and provides an air source of not less than 0.5MPa for the flexible mobile platform assembly 3; the truss structure 22 is symmetrically provided with three pairs of evenly distributed connecting seats on both sides along the length direction, and each connecting seat is provided with a pneumatic pressure-maintaining valve 23 and a flexible mobile platform assembly 3. The air source is first connected to the pneumatic pressure-maintaining valve 23 and then enters the flexible mobile platform assembly 3. When the air source is interrupted, it can ensure that the flexible mobile platform assembly 3 is self-locking within 2 hours to prevent the heavy workpiece being grasped from falling and causing a safety accident;

[0047] Preferably, the quick-change assembly includes a mechanical arm end 13 of the quick-change assembly and a workpiece end 21 of the quick-change assembly, and the selected model is ATI-QC1210; the pneumatic pressure-maintaining valve 23 is selected as Koshimei-BWS-0051;

[0048] Each flexible mobile platform component 3 includes an end cap 302, a flexible platform support base 301, an anti-wear gasket 305, a thrust ball bearing 306, a locknut bolt 303, a flexible platform moving shaft 304, a clamp fixed end 310, and a clamp 311;

[0049] The flexible platform support base 301 is a cylindrical structure with an open upper end. The flexible platform support base 301 is fixed to the connecting seat of the truss structure 22 by bolts. The upper end of the flexible platform support base 301 is connected to the end cap 302 by a flange. The flexible platform moving shaft 304 is a cylindrical structure with a limiting frustum on the outside. The flexible platform moving shaft 304 sequentially passes through the central positions of the flexible platform support base 301 and the connecting seat and is threadedly connected to the clamp fixed end 310 by M12. Thrust ball bearings 306 are provided on both the upper and lower sides of the limiting frustum of the flexible platform moving shaft 304. An anti-wear gasket 305 is provided between the roller of the upper thrust ball bearing 306 and the end cap 302, and an anti-wear gasket 305 is provided between the roller of the lower thrust ball bearing and the bottom of the flexible platform support base 301. The thrust ball bearings 306 on both the upper and lower sides can freely move within 2 mm in the radial direction relative to the anti-wear gasket 305;

[0050] A cavity is provided at the center of the flexible platform moving shaft 304. The clamp fixed end 310 includes a bottom frustum and a cylindrical connecting column at the upper center. The cavity of the flexible platform moving shaft 304 is threadedly connected to the connecting column of the clamp fixed end 310 by M12, and the flexible platform moving shaft 304 and the clamp fixed end 310 are connected and fixed from above by a locknut bolt 303 to prevent the threaded connection between the flexible platform moving shaft 304 and the clamp fixed end 310 from loosening and ensure the connection strength between the two;

[0051] The lower frustum of the clamp fixed end 310 is bolted to the clamp 311. The clamp 311 has a 2-mm chamfer ( Figure 3 C2 in it), and a cavity is provided at the center of the bottom of the clamp 311. The cavity is used to lock with the traction bolt 41 on the heavy workpiece component 4 by air pressure. The traction bolt 41 has a 1-mm chamfer ( Figure 3 C1 in it); during the downward movement of the robotic arm 11, under the guidance of the chamfer, the clamp 311 and the traction bolt 41 enable the clamp 311 connected to the flexible platform moving shaft 304 to move within 2 mm in the radial direction of the central hole at the bottom of the flexible platform support base 301, that is, within a circular ring with a ring distance of 2 mm outside the flexible platform moving shaft 304 in the initial state, compensating for the 1.5-mm absolute positioning error of the robotic arm (recorded in the instruction manual of the KUKA robotic arm model) and ensuring the quick and accurate grasping of each clamping point.

[0052] Preferably, the robotic arm 11 is of the model KUKA KR 1000 TITIAN.

[0053] Preferably, a clamping plate fixed side 308 is sleeved at the bottom of the connecting seat, and a clamping plate moving side 309 is sleeved on the bottom circular platform of the fixed end 310 of the clamp. The clamping plate fixed side 308 and the clamping plate moving side 309 are in contact and can slide relative to each other; annular magnets 307 are provided at the relative positions above the clamping plate fixed side 308 and below the clamping plate moving side 309. To ensure that in the non-working state, through the magnetic force of a pair of annular magnets and the flexible platform moving shaft 304, the central axis of the flexible platform moving shaft 304 coincides with the symmetry axis of the flexible platform support seat 301.

[0054] Preferably, the materials of the clamping plate fixed side 308 and the clamping plate moving side 309 are both polytetrafluoroethylene, with a friction coefficient of 0.02, having excellent self-lubricating performance, which can effectively reduce the friction between the two.

[0055] Preferably, the heavy workpiece assembly includes a large-size heavy workpiece 42 and a traction bolt 41; the traction bolt 41 is arranged at the clamping point positions on the heavy workpiece 42 corresponding to the six flexible moving platform assemblies 3.

[0056] Specific implementation method two: As shown in Figures 1 to 4 The present invention provides a grasping method for a multi-point flexible gripper at the end of a robotic arm for a heavy workpiece, including the following steps:

[0057] When grasping, the position and posture of the end gripper are adjusted by the robotic arm 11 so that the six flexible moving platform assemblies 3 of the clamping points are located above each clamping point, and the flexible moving platform assembly 3 is driven to move vertically downward. Under the guidance of the 2-mm chamfer of the clamp 311 and the 1-mm chamfer of the traction bolt 41, the ball of the thrust ball bearing 306 moves to complete the connection between the clamp 311 and the traction bolt 41 on the large-size heavy workpiece assembly 4, and the locking of the clamp 311 and the traction bolt 41 is completed by air pressure.

[0058] When the end gripper of the robotic arm 11 moves upward by a unit distance, if no step torque appears in the six-axis force sensor 12, it proves that the clamps 311 at each clamping point are all locked and connected to the traction bolts 41, and the grasping process is completed.

[0059] After the robotic arm 11 transports the large-size heavy workpiece assembly 4 to the designated position, the traction bolts 41 at each clamping point are released to complete the entire transportation process.

[0060] If the air source is interrupted during the working process, the pneumatic pressure-holding valve 23 can be relied on to ensure that the multi-point flexible gripper device is self-locked within 2 hours, so as to prevent the heavy workpiece assembly 4 being grabbed from falling and causing safety accidents.

[0061] Other combinations and connection relationships of this implementation scheme are the same as those of the specific implementation scheme one.

[0062] Simulation experiment

[0063] The present invention includes two key components, namely the flexible mobile platform assembly 3 and the truss structure 22, both of which need to be checked.

[0064] (1) Check of the load-bearing capacity of the flexible mobile platform assembly 3

[0065] Since the maximum weight of the heavy workpiece assembly 4 can reach 800 kg, the maximum weight is selected for checking, and the safety factor is required to be 1.5 or more; the flexible mobile platform assembly 3 includes two key load-bearing components, namely the thrust ball bearing 306 and the flexible platform moving shaft 304, both of which need to be checked.

[0066] The selected model of the thrust ball bearing 306 is BCL51105, its inner diameter is 25 mm, outer diameter is 42 mm, the material is GCr15, the rated static load Co is 15.4 kN, the rated dynamic load Cr is 23.9 kN, and the contact area is 0.0365 mm 2 , in the present invention, it is required to bear an axial force of 1.34 kN in the static state. It can be calculated that the static load safety factor S is 11.49, which is greater than 1.5 and meets the requirements; the contact stress in the static state is calculated to be 3671 MPa, which is less than the allowable value of 4000 MPa of the GCr15 material and meets the requirements. The M12 thread connection is selected between the flexible platform moving shaft 304 and the fixed end 310 of the clamp, the material is Gr15, the thread length is 35 mm, and it is required to bear an axial force of 1.34 kN in the present invention. The cross-sectional area of the minor diameter of the thread can be calculated as follows:

[0067]

[0068] In the formula, d represents the minor diameter of the M12 thread;

[0069] The tensile stress it bears is:

[0070]

[0071] In the formula, W represents the axial force required to be borne by the fixed end 310 of the clamp;

[0072] The yield strength of the material Gr15 is σ y = 1500 MPa. Considering the safety factor of 1.5, the allowable stress is:

[0073]

[0074] The allowable stress of 1000 MPa is significantly greater than 16.74 MPa, meeting the tensile strength requirement.

[0075] Its threaded shear area is calculated as:

[0076] A 剪 = π·d 中径 ·L = π×10.863×35 = 1195.98 mm 2

[0077] In the formula, d 中径 represents the pitch diameter of the M12 thread;

[0078] The shear stress it bears is:

[0079]

[0080] The shear strength of the material can be approximated as 60% of the tensile strength. Considering a safety factor of 1.5, its allowable shear stress is:

[0081]

[0082] The allowable shear stress of 600 MPa is significantly greater than 1.1 MPa, meeting the shear strength requirement.

[0083] (2) Check of the truss structure 22

[0084] The truss structure 22 is the load-bearing core of the entire flexible gripper device and needs to be ensured to be light enough in weight. To ensure that it can stably and safely carry out the handling work of heavy workpieces with a mass of 800 kg, six clamping points are selected for grasping, and each clamping point needs to bear a weight of more than 134 kg. It is very necessary to check it.

[0085] Through preliminary estimation, the stiffness of the fixed area of the flexible moving platform assembly 3 is relatively large, while the load-bearing beam bears large loads over a long distance, and the deformation mainly occurs in the load-bearing beam. Therefore, the truss structure 22 will be analyzed below. The two side load-bearing beams are made of Q235 steel plates with a thickness of 8 mm, and the middle load-bearing beam is made of Q235 steel plates with a thickness of 10 mm. The finite element analysis software ANSYS Workbench is used to analyze its deformation. Displacement constraints are applied to the contact surface of the quick-change assembly, gravity conditions are applied to the whole truss structure 22, with a safety factor of 1.5, and external forces of 2000 N vertically downward are applied to 6 working positions respectively. The simulation results of the finite element analysis software are as Figure 5 and Figure 6As shown, the maximum equivalent stress of the truss structure 22 is 58.3 MPa, and the maximum deformation is 339 μm, which is significantly less than the allowable stress of Q235 steel, 157 MPa, meeting the strength requirements.

[0086] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art of the present invention can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A multi-point flexible gripper at the end of a mechanical arm for heavy workpieces, characterized in that: It comprises a mechanical arm assembly (1), a truss structure assembly (2) and a flexible mobile platform assembly (3), The truss structure assembly (2) comprises a workpiece end (21) of a quick-change assembly, a truss structure (22), a pneumatic pressure-maintaining valve (23) and an air pipe; the mechanical arm end (13) of the quick-change assembly is connected to the mechanical arm assembly (1), the workpiece end (21) of the quick-change assembly is arranged at the middle position of the top end of the truss structure (22), and the truss structure (22) is a rectangular parallelepiped structure; the air pipe is fixed to the truss structure (22); the truss structure (22) is symmetrically provided with three pairs of evenly distributed connecting seats on both sides along the length direction, each connecting seat is provided with a pneumatic pressure-maintaining valve (23) and a flexible mobile platform assembly (3), and the air source is first connected to the pneumatic pressure-maintaining valve (23) and then enters the flexible mobile platform assembly (3), so as to ensure self-locking when the air source is interrupted; Each flexible mobile platform assembly (3) comprises an end cover (302), a flexible platform support seat (301), a thrust ball bearing (306), a flexible platform moving shaft (304), a clamp fixing end (310) and a clamp (311); The flexible platform support seat (301) is a cylindrical structure with an open upper end. The flexible platform support seat (301) is arranged on a connecting seat of a truss structure (22). The upper end of the flexible platform support seat (301) is connected to the end cover (302) via a flange. The flexible platform moving shaft (304) is a cylindrical structure and is provided with a limiting truncated cone on the outside. The flexible platform moving shaft (304) passes through the center position of the flexible platform support seat (301) and the connecting seat in sequence and is connected to the clamp fixed end (310). Thrust ball bearings (306) are provided on both the upper and lower sides of the limiting truncated cone of the flexible platform moving shaft (304). The thrust ball bearings (306) on the upper and lower sides can move freely and synchronously within the critical range of the space in the radial direction. The lower cone of the fixed end (310) of the clamp is connected to the clamp (311), and the clamp (311) is provided with a chamfer. A cavity is provided at the bottom center of the clamp (311), and the cavity is used for pneumatic locking with the traction bolt (41) on the heavy workpiece assembly (4), and the traction bolt (41) is provided with a chamfer; when the robot arm assembly (1) moves downward, the clamp (311) and the traction bolt (41) are guided by the chamfer to move the clamp (311) connected to the flexible platform moving shaft (304) within the critical range of the space in the radial direction of the bottom center hole of the flexible platform support seat.

2. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 1, characterized in that: The mechanical arm assembly (1) comprises a mechanical arm (11), a six-dimensional force sensor (12) and a mechanical arm end (13) of a quick-change assembly; the mechanical arm (11) is used to achieve displacement and posture adjustment of a multi-point flexible gripper, the end of the mechanical arm (11) is connected to the six-dimensional force sensor (12), the six-dimensional force sensor (12) is connected to the mechanical arm end (13) of the quick-change assembly, and the mechanical arm end (13) of the quick-change assembly is connected to a workpiece end (21) of the quick-change assembly.

3. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 2, characterized in that: The air pipe is used to provide an air source of no less than 0.5 MPa to the flexible mobile platform component (3).

4. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 3, characterized in that: When the gas source is interrupted, the pneumatic pressure-maintaining valve (23) ensures that the flexible mobile platform assembly (3) is self-locked within 2 hours.

5. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 4, characterized in that: It also includes an anti-wear gasket (305), wherein an anti-wear gasket (305) is provided between the roller of the upper thrust ball bearing (306) and the end cover (302), and an anti-wear gasket (305) is provided between the roller of the lower thrust ball bearing (306) and the bottom of the flexible platform support seat (301), and the thrust ball bearings (306) on both sides are free to move within a critical space range in the radial direction relative to the anti-wear gasket (305), and the critical space is 2 mm.

6. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 5, characterized in that: It also includes an anti-loosening bolt (303), and the cavity of the flexible platform moving shaft (304) and the connecting column of the clamp fixed end (310) are connected via an M12 thread, and the flexible platform moving shaft (304) and the clamp fixed end (310) are connected and fixed from above via the anti-loosening bolt (303).

7. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 6, characterized in that: The clamp (311) is provided with a chamfer of 2 mm, and the traction bolt (41) is provided with a chamfer of 1 mm, so as to compensate for the absolute positioning error of the robot arm (11) of 1.5 mm.

8. The multi-point flexible gripper at the end of a mechanical arm for heavy workpieces according to claim 7, characterized in that: The bottom of the connecting seat is sleeved with a splint fixed side (308), and the bottom circular platform of the clamp fixed end (310) is sleeved with a splint movable side (309), and the splint fixed side (308) and the splint movable side (309) are in contact and can slide relative to each other; annular magnets (307) are provided at relative positions above the splint fixed side (308) and below the splint movable side (309), which are used to ensure that in a non-working state, the flexible platform movable axis (304) is always located at the center of the displacement area through a pair of annular magnets (307).

9. A method for grasping a heavy workpiece by a multi-point flexible gripper at the end of a robot arm as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: When grasping, the position and posture of the end gripper are adjusted by the mechanical arm (11) so that the flexible mobile platform assembly (3) of the six clamping points is located above each clamping point, and the flexible mobile platform assembly (3) is driven to move vertically downward. Under the guidance of the 2mm chamfer of the clamp (311) and the 1mm chamfer of the traction bolt (41), the connection between the clamp and the traction bolt (41) on the large-sized heavy workpiece assembly (4) is completed through the movement of the ball of the thrust ball bearing (306), and the clamp (311) and the traction bolt (41) are locked by air pressure; When the gripper at the end of the mechanical arm (11) moves upward by a unit distance and no step torque is detected in the six-dimensional force sensor (12), it is proved that the clamps (311) at each clamping point are locked and connected with the traction bolts (41), and the grasping process is completed.

10. The method for grabbing a heavy workpiece by a multi-point flexible gripper at the end of a mechanical arm according to claim 9, characterized in that: If the air source is interrupted during the working process, the pneumatic pressure-maintaining valve (23) is used to ensure that the multi-point flexible gripper device is self-locked within 2 hours.

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