Industrial robot end error compensation device

Abstract

The application belongs to the technical field of mechanical manufacturing equipment, and particularly relates to an industrial mechanical arm tail end error compensation device, which comprises an upper shell, a lower shell, an adjusting plate, an inner connecting ring, a piston assembly, a spherical body assembly and a guiding and limiting assembly. The upper shell and the lower shell are both hollow structures, the bottom of the upper shell is provided with the inner connecting ring, the top of the lower shell is detachably connected with the upper shell through a snap type structure to form a preset displacement space, the piston assembly is arranged in the upper shell, the displacement adjustment is realized by driving the adjusting plate through the piston and the piston rod, the bottom of the upper shell is provided with a hemispherical groove, and the spherical body assembly arranged in the hemispherical groove forms a spherical surface matching pair to realize multi-degree-of-freedom compensation, and the guiding and limiting assembly limits the movement range of the piston and the lower shell. The application solves the problem of weak bearing capacity and difficulty in standardization caused by the spring compensation scheme in the prior art, can realize six-degree-of-freedom precise compensation without elastic elements, and has the advantages of high bearing capacity, stable structure, high compensation precision and strong adaptability.

Description

Technical Field

[0001] This utility model belongs to the field of mechanical manufacturing equipment technology, and specifically relates to an error compensation device for the end effector of an industrial robotic arm. Background Technology

[0002] With the rapid development of intelligent manufacturing and industrial automation, industrial robotic arms have become key execution units in modern manufacturing systems, widely used in high-precision operations such as assembly, welding, handling, grinding, and painting. The operational quality of a robotic arm largely depends on the positioning accuracy and compliance of its end-effector. However, in actual operation, the end-effector of a robotic arm is often affected by various factors, leading to positional and orientation errors between it and the workpiece.

[0003] The main factors affecting the accuracy of a robotic arm's end effector include: workpiece positioning error, caused by spatial positional errors due to workpiece clamping, reference deviations, etc.; absolute positioning error of the robotic arm, caused by sensor accuracy, joint cumulative error, manufacturing and assembly errors, etc.; and environmental and structural deformation, such as spatial drift caused by thermal expansion and load deformation. To eliminate these errors, a multi-degree-of-freedom error compensation device is typically installed at the end effector to achieve minute adjustments in position and attitude within space. Most existing compensation devices are six-degree-of-freedom compensation structures, capable of simultaneously providing lateral compensation, compression compensation, angular compensation, and torsional compensation to meet complex contact alignment requirements.

[0004] However, traditional six-degree-of-freedom compensation devices generally use spring elements to achieve flexible compensation. These devices have the following shortcomings: 1. Insufficient load-bearing capacity of the spring structure; the spring element is prone to nonlinear deformation under stress, making it difficult to meet stability requirements under high load conditions. 2. Limited specifications and poor adaptability; existing products are mostly designed with fixed stiffness and stroke, unable to flexibly adapt to the needs of different types of robotic arms and complex operating scenarios. 3. Limited compensation accuracy: the fixed stiffness parameters of the spring compensation structure are not adjustable, making fine-tuning of the response impossible, affecting compensation accuracy and stability.

[0005] Therefore, there is an urgent need for a fully mechanical six-degree-of-freedom error compensation device that can achieve multi-degree-of-freedom precision compensation without the need for elastic elements, so as to improve the positioning accuracy and stability reliability of the robotic arm end effector. Utility Model Content

[0006] To address the issues of weak load-bearing capacity and difficulty in standardization caused by the use of spring compensation schemes in traditional six-degree-of-freedom devices in the prior art, this utility model provides an industrial robotic arm end effector error compensation device. This device achieves fully mechanical error compensation with adjustable rigidity and flexibility, sensitive movement, stable coordination, and expandable structure, thereby improving the positioning accuracy and operational reliability of the robotic arm end effector.

[0007] This utility model provides an end-effector error compensation device for an industrial robotic arm, comprising an upper housing, a lower housing, an adjustment plate, an inner connecting ring, a piston assembly, a ball assembly, and a guide and limiting assembly;

[0008] Both the upper and lower shells have hollow cavity structures. An inner connecting ring is fixedly installed at the bottom of the upper shell. The main body of the inner connecting ring is a ring-shaped columnar structure, with one end fixedly connected to the bottom of the upper shell and the other end having a ring-shaped outer edge structure along its outer perimeter. The top of the lower shell has a ring-shaped inner edge that matches the outer edge of the bottom of the upper shell. The inner edge and the outer edge are connected by a snap-fit ​​structure, with the outer edge snapping onto the inside of the inner edge, and a preset displacement space is formed between the outer wall of the inner edge and the upper shell.

[0009] The piston of the piston assembly is installed in the inner cavity of the upper housing, and a sealing structure is provided between its outer wall and the inner cavity wall of the upper housing to form a closed pressure chamber; the piston rod of the piston assembly is coaxially connected to the lower end of the piston, and its bottom is fixedly connected to the adjustment plate.

[0010] The bottom of the upper shell and the lower shell are respectively provided with corresponding hemispherical grooves. The two hemispherical grooves are symmetrically arranged and their arc surfaces face each other to form a spherical mating pair. The spherical assembly is placed in the spherical mating pair, and its spherical surface is in close contact with the arc surfaces of the two hemispherical grooves. The bottom of the arc surface of each hemispherical groove is provided with a coaxial cylindrical hole. The axis of the cylindrical hole is coaxial with the central axis of the piston and piston rod.

[0011] The guide and limiting assembly is disposed between the upper housing and the lower housing to limit the range of motion of the piston and the lower housing.

[0012] In a preferred embodiment, the sphere assembly further includes an upper sphere and a lower sphere, both of which are hemispherical structures and are respectively installed in hemispherical grooves provided in the upper and lower shells. After assembly, the two form a matching spherical substructure through the spherical contact area.

[0013] In a preferred embodiment, the upper sphere and the lower sphere are further provided with connecting rod structures on their arc surfaces, and the bottom of the hemispherical grooves of the upper and lower shells are respectively provided with cylindrical holes, and the two connecting rods pass through the corresponding cylindrical holes and are connected to each other.

[0014] In a preferred implementation, the diameter of the cylindrical hole is further greater than the outer diameter of the connecting rod.

[0015] In a preferred embodiment, the bottom of the adjustment plate is provided with a boss, which is located above the plane of the upper sphere.

[0016] In a preferred implementation, the plurality of guide limiting components are further arranged circumferentially along the outer side of the ball assembly, and each guide limiting component includes a connecting rod, an upper washer, a steel ball, and a lower washer;

[0017] The bottom of the upper housing has multiple through holes evenly distributed around the outer side of its hemispherical groove. Each through hole has an upper gasket mounting seat at its bottom, and a guide cavity coaxial with the through hole is formed in the upper gasket mounting seat. The bottom of the lower housing has a lower gasket mounting seat that is radially corresponding to the upper gasket mounting seat and located directly below it. The upper gasket can slide axially in the upper gasket mounting seat, and the lower gasket is fixedly installed in the lower gasket mounting seat. The opposing surfaces of the upper and lower gaskets are machined together to form a complete spherical groove, and the steel ball is placed in the spherical groove. One end of the connecting rod passes through the through hole at the bottom of the upper housing and is fixedly connected to the adjusting plate, and the other end is fixedly connected to the upper gasket.

[0018] In a preferred implementation, the number of guide limiting components is three, and they are arranged circumferentially at 120° intervals along the outer side of the outer edge of the sphere component.

[0019] In a preferred embodiment, the upper housing further includes a top cover, a guide plate, and an upper frame, which are assembled and connected sequentially along the vertical direction of the device to form an integral structure; the top cover is installed at the uppermost end of the upper housing and has a piston chamber inside; the guide plate is disposed between the bottom of the top cover and the top of the upper frame, and the guide plate has a guide hole in the middle that matches the diameter of the piston rod; the upper frame is located at the lower part of the upper housing, and its bottom has a hemispherical groove of the upper housing; the bottom outer edge of the upper frame is connected to the inner connecting ring.

[0020] In a preferred embodiment, the lower housing further includes a lower frame and an outer connecting ring. The bottom of the lower frame is provided with a hemispherical groove for the lower housing. The top or side of the lower frame is connected to the outer connecting ring along the circumferential direction. The inner side of the top of the outer connecting ring is provided with an inner eave for the lower housing.

[0021] In a preferred embodiment, the top cover of the upper housing is provided with a first air inlet and a second air inlet. Both the first air inlet and the second air inlet are connected to the working chamber of the piston top surface inside the top cover. The two air inlets are used to input gases with different functions to achieve stiffness adjustment and locking reset control of the piston assembly.

[0022] The beneficial effects of this utility model are:

[0023] First, the industrial robotic arm end effector error compensation device of this utility model adopts a fully mechanical structural design. A rigid frame is formed by the upper and lower housings and the inner connecting ring, with a piston assembly and a ball assembly as the core force transmission mechanism. The pneumatically driven piston structure replaces the elastic element, providing higher axial load capacity while ensuring compensation flexibility. This allows the device to maintain structural stability under high loads and complex posture compensation, solving the problem of insufficient load capacity caused by traditional six-degree-of-freedom compensation devices that rely heavily on springs for flexible compensation. Through the cooperation of the piston assembly and the closed pressure chamber inside the upper housing, gas is introduced into the chamber to form an adjustable air pressure, achieving flexible driving and rigid locking of the piston. The air pressure can be adjusted in real time according to different load conditions, thereby dynamically changing the overall stiffness of the system. This provides multi-degree-of-freedom flexible adjustment during the compensation phase and rapid locking during the positioning phase, ensuring the accuracy and repeatability of the compensation action. This overcomes the shortcomings of traditional compensation structures, such as low accuracy and slow response. The invention features hemispherical grooves at the bottom of both the upper and lower housings, where the spherical assembly is placed to form a spherical joint. This "spherical hinge" design enables multi-degree-of-freedom compensated motion in the lateral, axial, angular, and torsional directions. Compared to contact with a plane or conical surface, the spherical joint maintains a stable fit, effectively absorbing deviations caused by positioning errors and thermal deformation, and avoiding jamming caused by changes in the fit clearance. The invention eliminates the limitations of traditional spring parameters, allowing for different compensation amounts and load-bearing levels through interchangeable housing dimensions, spherical diameters, and piston strokes. It exhibits excellent modularity and versatility. Its fully mechanical design not only improves reliability and lifespan but also reduces maintenance costs, meeting the demands of modern manufacturing for high precision, high strength, and multi-condition adaptability.

[0024] Secondly, in the preferred implementation, this utility model adopts an upper and lower split spherical structure in the spherical assembly. That is, the upper sphere and the lower sphere are respectively installed in the hemispherical grooves of the upper shell and the lower shell, and after assembly, they form a matching spherical substructure through spherical contact. Both the upper and lower spheres are provided with connecting rod structures on their arc surfaces, and they are connected to each other by passing through cylindrical holes. This ensures the coaxiality between the spheres. The design of the cylindrical hole diameter being larger than the outer diameter of the connecting rod provides a certain amount of movement clearance for the spherical assembly, allowing it to make slight adaptive adjustments when under force, thereby improving the compensation flexibility and anti-eccentric load capacity, and achieving a balance between structural stability and compensation flexibility.

[0025] Third, in the preferred implementation, this utility model achieves the automatic posture zeroing function during the locking and resetting process by setting a boss structure at the bottom of the adjustment plate and reserving a preset distance between the bottom surface of the boss and the top of the upper sphere. When the device enters the locking stage, the boss can exert a limiting effect on the upper sphere, so that it can quickly return to the initial posture parallel to the cross-section of the device, thereby ensuring the geometric symmetry and force balance of the spherical pair in the locking state.

[0026] Fourth, in the preferred implementation, this utility model achieves a multi-functional integrated design of low-friction guidance, tilt rotation constraint, and stroke limitation by circumferentially setting multiple guide and limiting components on the outer side of the ball assembly. The guide and limiting components consist of a connecting rod, an upper washer, a steel ball, and a lower washer. The upper and lower washer together form a ball-joint-like structure, in which the steel ball is placed, providing compliant compensation in the torsional, oscillating, and micro-slipping directions. This allows the device to maintain high-precision attitude compensation and stable contact even under complex working conditions such as assembly errors, load disturbances, and thermal drift. The low-friction characteristics of the internal steel ball pair ensure smooth movement and reduce frictional hysteresis and stress concentration during the compensation process. The preferred three-point 120° equidistant circumferential arrangement not only achieves symmetrical support and force balance but also effectively avoids over-constraint problems. Under medium loads and large swing angles, it exhibits advantages such as fast return to center, low resistance, and excellent centering.

[0027] Fifth, in the preferred embodiment, this utility model provides a first air inlet and a second air inlet on the top cover of the upper housing, and installs independent air pipe connectors on each, to achieve input control of different functional gases, enabling the device to have the dual functions of adjustable stiffness and rapid locking and resetting. The first air inlet can introduce working gas to apply adjustable air pressure to the top surface of the piston, thereby changing the force state between the piston assembly and the upper housing, flexibly adjusting the overall stiffness of the system to meet different load and compensation accuracy requirements; the second air inlet is used to introduce locking air pressure after compensation is completed, so that the piston quickly returns to its position and forms a rigid fixation, realizing rapid resetting and locking of the structure. Attached Figure Description

[0028] Figure 1 This is a top view of the robotic arm end effector error compensation device according to an embodiment of the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the cross-sectional structure along line AA;

[0030] Figure 3 for Figure 1 Schematic diagram of the cross-sectional structure along line BB;

[0031] Figure 4 for Figure 3 Schematic diagram of the cross-sectional structure along the CC line;

[0032] Figure 5 for Figure 3 A schematic diagram along direction D.

[0033] Among them, 1-lower frame; 2-outer connecting ring; 3-upper frame; 4-guide plate; 5-top cover; 6-piston ring; 7-piston; 8-piston rod; 9-adjusting plate; 10-upper ball; 11-lower ball; 12-connecting rod; 13-upper gasket; 14-inner connecting ring; 15-steel ball; 16-lower gasket; 17-first air pipe connector; 18-second air pipe connector. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of this application, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] The directional terms such as above, below, left, right, front, and back used in this application are based on the positional relationships shown in the attached drawings. Different attached drawings may result in different positional relationships, therefore they should not be interpreted as limitations on the scope of protection.

[0036] In this application, the terms "installation," "connection," "interlocking," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, or a connection that allows communication between components. They can also refer to a direct connection or an indirect connection through an intermediate medium. They can refer to the internal connection of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0037] This invention discloses an end-effector error compensation device, particularly suitable for automatic compensation and smooth adjustment of position and posture errors between the end effector and the workpiece during high-precision assembly, welding, grinding, painting, and handling operations of industrial robotic arms. This device can achieve micro-compensation and posture correction of the robotic arm end effector in multiple degrees of freedom under complex working conditions, thereby effectively improving operational accuracy and contact stability. Addressing the shortcomings of existing six-degree-of-freedom error compensation devices that rely on spring elements, resulting in weak load-bearing capacity, poor adaptability, and limited compensation accuracy, this invention proposes a fully mechanical six-degree-of-freedom error compensation scheme. This device utilizes the coordinated design of an upper shell, lower shell, inner connecting ring, piston assembly, ball assembly, and guide limiting assembly. It achieves lateral and angular compensation through a spherical sliding fit structure, compression compensation through the axial displacement of the piston assembly, and torsional compensation through the interlocking connection structure between the lower and upper shells. This decomposes complex multidimensional errors into controllable mechanical compensation movements, achieving precise posture correction in multiple degrees of freedom. This error compensation device is installed between the end effector and the end effector of an industrial robotic arm, forming a flexible connection interface. The end effector can be a workpiece clamping mechanism such as a jig, pneumatic gripper, electric gripper, or vacuum suction cup, or a processing mechanism such as a welding torch, grinding head, spray gun, or drilling unit. When the actuator contacts the workpiece, the ball joint, gasket, and pneumatic piston assembly inside the device can perform lateral, axial, angular, and torsional compensation according to the direction of the external force, achieving precise alignment between the workpiece and the actuator. After the compensation action is completed, the device can be quickly restored to a high-rigidity stable state by air pressure locking, ensuring repeatability and mechanical rigidity in subsequent processing or assembly.

[0038] As per the instruction manual Figure 1-5 An error compensation device for the end effector of an industrial robotic arm includes an upper housing, a lower housing, an adjustment plate 9, an inner connecting ring 14, a piston assembly, a ball assembly, and a guide and limiting assembly. Both the upper and lower housings have hollow cavity structures. The inner connecting ring 14 is fixedly installed at the bottom of the upper housing. The main body of the inner connecting ring 14 is a ring-shaped columnar structure, with one end fixedly connected to the bottom of the upper housing and the other end having an annular outer edge structure along its outer circumference. The top of the lower housing has an annular inner edge that matches the outer edge of the bottom of the upper housing. The inner and outer edges are connected by a snap-fit ​​structure. The outer edge snaps onto the inner edge, and a preset displacement space is formed between the outer wall of the inner edge and the upper housing. Through this structural design, when the lower housing is subjected to external force, its bottom can achieve controlled torsion and slight displacement along the direction of the external force under the constraint of the snap-fit ​​between the outer and inner edges, thereby achieving multi-directional attitude compensation.

[0039] The piston assembly includes a piston 7 and a piston rod 8. The piston 7 is installed in the inner cavity of the upper housing, and a sealing structure is provided between its outer wall and the inner wall of the upper housing to form a closed pressure chamber and ensure the smoothness of the compensation action. The piston rod 8 is coaxially connected to the lower end of the piston 7, and its bottom is fixedly connected to the adjusting plate 9. It is used to transmit piston displacement to the lower housing structure or to transmit external forces on the lower housing to the piston, realizing axial (Z-axis) compensation and minute attitude adjustment. This piston assembly can generate displacement when subjected to external torque or axial impact, thereby dynamically compensating for the contact force of the end effector.

[0040] The bottoms of the upper and lower shells are provided with corresponding hemispherical grooves, arranged symmetrically, and the arc surfaces of the two hemispherical grooves form a pair of spherical mating pairs. A spherical assembly is placed within the spherical mating pair, with its spherical surface fitting snugly against the arc surfaces of the two hemispherical grooves. Each hemispherical groove has a coaxial cylindrical hole at its bottom arc surface, the axis of which is coaxial with the central axis of the piston 7 and piston rod 8. This spherical mating structure allows the lower shell to adaptively fine-tune around the center of the sphere when subjected to lateral forces, torsional loads, or angular disturbances, thereby achieving lateral compensation, angular compensation, and torsional compensation.

[0041] A guide and limiting assembly is arranged between the upper and lower housings to limit the range of motion of piston 7 and the lower housing, preventing excessive structural deformation or movement exceeding limits. This assembly includes a limiting pin, a sliding guide post, or a spherical constraint ring element to ensure the motion stability and repeatability of the entire compensation device during multi-degree-of-freedom linkage.

[0042] When positional or angular errors occur during contact between the robotic arm's end effector and the workpiece, the external force first acts on the lower housing. The lower housing achieves micro-torsional compensation along the direction of the external force through the interlocking structure between its inner edge and the outer edge of the inner connecting ring 14; simultaneously, the piston assembly generates a small axial displacement to achieve compression compensation; and the ball assembly, through the sliding fit of the spherical pair, further achieves adaptive adjustment in the lateral and angular directions. These compensation actions coordinate with each other, thereby achieving comprehensive error compensation in six degrees of freedom, effectively improving the assembly and operational accuracy of the robotic arm's end effector.

[0043] In a preferred embodiment of this application, the spherical assembly includes an upper sphere 10 and a lower sphere 11, which together constitute the core compliant unit of the compensation device, used to achieve multi-directional angle and displacement compensation of the robotic arm end effector. The upper sphere 10 and lower sphere 11 are primarily hemispherical structures, located in hemispherical grooves in the upper and lower housings respectively. After assembly, they form a pair of matching spherical substructures through a spherical contact area. The upper sphere 10 is installed in the hemispherical groove at the bottom of the upper housing, and its spherical shape matches the spherical curvature of the upper housing groove cavity to ensure it can perform minute rotations within a limited range. The lower sphere 11 is installed in the hemispherical groove at the top of the lower housing, and its spherical shape matches the curvature of the lower housing groove cavity, similarly enabling limited-angle rotation and micro-movement within the spherical contact area. The centers of the two hemispheres are located on a common axis, which coincides with the central axis of the piston assembly in the locked state of the compensation device, thus ensuring symmetrical posture and balanced force in the locked state.

[0044] Both the upper sphere 10 and the lower sphere 11 have an integrally formed connecting rod structure on one side. The two connecting rods are arranged in the same direction along the arc surface of the spheres and are fixedly connected by means of threaded connection, pin connection, or interference fit, forming a rigid force transmission chain. This connecting rod not only serves to position and transmit force between the two spheres, but also acts as a central guide shaft for the compensation device when needed, restricting the degree of freedom of relative sliding between the spheres. The presence of the connecting rod allows the upper and lower spheres to rotate as a whole within the hemispherical grooves of the upper and lower shells, thereby achieving spherical degree of freedom compensation while maintaining the overall mechanical stability and attitude coordination of the device.

[0045] When an external force is applied to the lower housing, the force is transmitted through the lower sphere 11 to the connecting rod, and then through the connecting rod to the upper sphere 10. Because the contact between the sphere and the hemispherical groove is a smooth spherical surface with a low coefficient of friction, the sphere assembly can perform micro-angle rotation and micro-radial displacement in three-dimensional space, achieving angle compensation and lateral compensation (X and Y directions). Simultaneously, the rigid connection of the connecting rod ensures coordinated response of the upper and lower spheres under force, effectively preventing local offset or attitude imbalance, thereby enhancing the overall stability and repeatability of the compensation device.

[0046] Preferably, the radii of the upper sphere 10 and the lower sphere 11 can be equal or have slight differences to adjust the compensation sensitivity. The connecting rod can be made of high-strength alloy steel or titanium alloy, and its end can be provided with a threaded section, a locating pin hole, or a locking groove to achieve assembly accuracy control. A wear-resistant self-lubricating coating (such as a PTFE film) can be applied between the sphere and the groove cavity to reduce wear and extend service life.

[0047] To prevent excessive displacement of the spherical assembly and avoid disengagement of the spherical pair, cylindrical holes are respectively provided at the bottom of the hemispherical groove arc surfaces of the upper and lower shells. These cylindrical holes are coaxial with the center lines of the two hemispherical grooves. These cylindrical holes are used to geometrically limit the stroke and swing angle of the connecting rods of the upper sphere 10 and lower sphere 11. The diameter D of the cylindrical hole is designed to be larger than the outer diameter d of the corresponding connecting rod, forming a clearance fit (D > d). This ensures free swing and slight radial displacement of the connecting rod while limiting the maximum displacement and maximum swing angle. Preferably, the radial clearance Δr of Dd is 0.10mm-0.80mm, more preferably 0.20mm-0.50mm. The clearance size can be determined empirically or through structural simulation based on the target compensation angle θ_max and the extension length L of the connecting rod. The cylindrical holes are preferably straight cylindrical holes with their axes coaxial with the central axis of the piston assembly to maintain the symmetry of the device. To reduce edge interference, the orifice is fitted with an inlet chamfer or fillet, such as R0.5-R1.

[0048] When the compensation device is working, the connecting rod swings at a small angle and undergoes radial displacement along with the upper ball 10 and the lower ball 11. When the displacement approaches the upper limit, the outer circle of the connecting rod makes geometric contact with the cylindrical hole wall, forming a rigid limit to prevent the spherical pair from separating or exceeding the posture limit. To suppress the impact of the limit position collision, an elastic buffer ring, such as a thin fluororubber / polyurethane retaining ring, can be set on the hole wall or the shoulder of the connecting rod to absorb the end energy and reduce noise.

[0049] In a preferred embodiment of this application, the bottom of the adjustment plate 9 is provided with a boss, which is located above the upper ball 10. The boss is used to quickly zero the attitude of the upper ball during the locking and resetting process, so that the upper surface of the upper ball is restored to a state parallel to the cross-section of the device, thereby ensuring the symmetry and repeatability of the spherical pair in the locking state.

[0050] The boss is a short cylindrical or ring-shaped structure, connected to the adjusting plate 9 by screws, interference fits, or integral machining. The boss axis is coaxial with the central axis of the piston assembly. The top of the upper ball 10 has a flat surface formed by spherical cutting, which is arranged opposite to the bottom surface of the boss, forming a free travel gap between them to accommodate the small-angle swing and micro-displacement of the ball under compensation conditions. Through the design of the boss, the preset spacing, and the flat surface of the upper ball 10, fast, controllable, and low-impact locking and resetting are achieved without affecting the compensation sensitivity. After resetting, it is ensured that the common axis coincides with the piston central axis in the locked state, improving repeatability and force uniformity.

[0051] In a preferred embodiment of this application, multiple guide and limiting components are circumferentially distributed along the outer side of the ball assembly to provide low-friction guidance, tilt rotation constraint, and stroke limitation during the unlocking compensation and locking reset processes of the device. Each guide and limiting component includes a connecting rod 12, an upper washer 13, a steel ball 15, and a lower washer 16.

[0052] Multiple through holes are evenly distributed around the outer side of the hemispherical groove at the bottom of the upper housing. Each through hole has an upper gasket mounting seat at its bottom, and a guide cavity coaxial with the through hole is formed within the upper gasket mounting seat. A lower gasket mounting seat is located radially opposite to and directly below the upper gasket mounting seat on the inner side of the bottom of the lower housing. The upper gasket 13 can slide axially within the upper gasket mounting seat, and the lower gasket 16 is fixedly mounted within the lower gasket mounting seat. The opposing surfaces of the upper gasket 13 and lower gasket 16 are machined together to form a complete spherical groove. A steel ball 15 is placed within the spherical groove, and together with the upper gasket 13 and lower gasket 16, they constitute a ball-joint-like structure with multi-degree-of-freedom micro-displacement capabilities. These three components together provide compliant compensation capabilities for torsion, oscillation, and micro-slippage, thereby achieving error compensation for the device under assembly deviation, load disturbance, and thermal drift conditions. One end of each connecting rod 12 passes through the bottom through hole of the upper housing and is fixedly connected to the adjusting plate 9, such as by thread or pin positioning connection. The other end of the connecting rod 12 is fixedly connected to the upper gasket 13, such as by threaded end connection or shoulder interference, forming a rigid force transmission chain.

[0053] Preferably, three guide and limiting components are arranged circumferentially at 120° intervals along the outer edge of the spherical component, forming an equilateral three-point support to ensure symmetry and force balance under both unlocking and locking conditions. In scenarios with moderate loads and large swing angles, three guide and limiting components are less likely to cause over-constraint, resulting in fast centering and low resistance. Alternatively, four (90° division) or six (60° division) components can be used depending on load and space requirements to improve guide stiffness or reduce single-point contact stress.

[0054] In a preferred embodiment of this application, the upper housing includes a top cover 5, a guide plate 4, and an upper frame 3. These components are sequentially assembled along the vertical direction of the device and connected by bolts to form a whole. This assembly supports the piston assembly, guides the movement of the piston rod, and forms a force-closed system with the lower housing and inner connecting ring. The top cover 5 is installed at the uppermost end of the upper housing and has a piston chamber machined inside. This piston chamber is cylindrical or stepped cylindrical in shape and is used to accommodate the piston 7 in the piston assembly, forming a working chamber. The guide plate 4 is located between the bottom of the top cover 5 and the top of the upper frame 3, and has a flat plate structure, serving as a guide and positioning element. The upper frame 3 is a hollow annular structure located at the lower part of the entire upper housing. Its bottom outer edge is machined with a hemispherical groove for mating with a spherical assembly.

[0055] The top cover 5, guide plate 4, and upper frame 3 have internally threaded holes running through their side walls in the axial direction, forming long bolt channels. Long bolts can be inserted and tightened to achieve a unified fixed connection between the three components. The piston cavity axis formed inside the top cover 5 is coaxial with the central axis of the device, used to accommodate the piston 7 and limit its vertical movement stroke. Piston rings 6 are installed on the outer periphery of the piston 7 to achieve a sealing and leak-proof function within the piston cavity. The outer periphery of the top cover 5 can be machined with a positioning flange or threaded interface for connection with the robotic arm connector. The guide plate 4 has a guide hole in the middle that matches the diameter of the piston rod 8. The axis of the guide hole is coaxial with the central axis of the piston cavity, used to provide precise linear guidance for the piston rod. The wall of the guide hole can be fitted with a wear-resistant bushing or a self-lubricating bushing, such as PTFE, to reduce friction and improve service life. The upper frame 3 is the main load-bearing body. Its upper end face contacts the bottom surface of the guide plate, and its lower end face is machined into a hemispherical groove to accommodate the upper sphere 10. Multiple through holes and upper gasket mounting seats connected to the through holes are evenly distributed around the outer periphery of the hemispherical groove at the bottom of the upper frame for mounting the upper gasket 13 of the guide and limit assembly. The inner connecting ring 14 is fixed to the outer edge of the bottom of the upper frame by bolts. The inner connecting ring serves as the interface element between the upper and lower shells and undertakes the function of transmitting torsional and compressive forces.

[0056] In the preferred embodiment of this application, the lower housing includes a lower frame 1 and an outer connecting ring 2, which are bolted together to form an integral whole. The lower frame 1 is used to support the upper spherical assembly and to form a snap-fit ​​with the inner connecting ring 14 of the upper housing. The lower frame 2 plays a major supporting, guiding and limiting role during the stress and compensation movement of the device.

[0057] The lower frame 1 has a disc-shaped structure. A hemispherical groove is machined along the central axis at the bottom of the lower frame 1. This hemispherical groove corresponds to and is symmetrically arranged with the hemispherical groove at the bottom of the upper frame 3 of the upper shell. The two hemispherical grooves together form the mating space for the spherical assembly. Multiple bolt holes are arranged around the top or side of the lower frame 1 for connection and fixation with the outer connecting ring 2. The inner edge of the lower shell is located on the inner side of the top of the outer connecting ring 2.

[0058] In a preferred embodiment of this application, the top cover 5 of the upper housing is provided with a first air inlet and a second air inlet. A gas pipe connector 17 is installed at the first air inlet, and a gas pipe connector 18 is installed at the second air inlet. Both are used for the input of different functional gases to achieve stiffness adjustment and locking / resetting control of the piston assembly. Both air inlets are connected to the piston top working chamber inside the top cover 5. The introduced gas ultimately acts on the top of the piston 7 and the inner cavity area of ​​the upper housing, thereby generating gas pressure and controlling the axial displacement of the piston assembly.

[0059] The first and second air inlets are respectively arranged on the top surface of the top cover 5, preferably radially spaced to avoid mutual interference. The axes of the two air inlets are perpendicular to the central axis of the piston chamber. The first air inlet is mainly used to introduce gas, such as compressed air or nitrogen, to maintain the overall rigidity of the device. The gas pressure can be adjusted by an external proportional pressure regulating valve or a precision pressure reducing valve to flexibly adjust the system rigidity according to the load mass and working force at the end of the robotic arm. When an appropriate gas pressure is introduced, the top of the piston 7 is subjected to downward force, causing the piston assembly to form a stable pre-tightened state, thereby improving the overall deformation resistance and stability of the device. This gas path is usually maintained at atmospheric pressure to ensure that the compensation device has a certain gas spring stiffness during normal operation. The second air inlet is used to introduce high-pressure locking gas into the piston chamber when the operation is completed or the posture needs to be reset. When the second air inlet is opened, the gas enters the upper region of the piston chamber and is rapidly pressurized, pushing the piston 7 to move downward along the axis, driving the piston rod 8 and the adjusting plate 9 to achieve the locking and reset action.

[0060] Preferably, the first air inlet has a pressure range of 0.1-0.6 MPa for stiffness adjustment, and the second air inlet has a pressure range of 0.4-0.8 MPa for locking and resetting.

[0061] The working principle of the industrial robotic arm end-effector error compensation device of this invention is as follows:

[0062] This utility model discloses an industrial robotic arm end-effector error compensation device that is pneumatically driven. Its core lies in the synergistic action of the piston assembly, ball assembly, and guide / limiting assembly to achieve compliant error compensation and high-precision locking and resetting of the robotic arm end-effector in six degrees of freedom. The device internally consists of an upper housing, a lower housing, a piston assembly, an adjusting plate 9, a ball assembly, a guide / limiting assembly, an inner connecting ring 14, and a pneumatic system. Under controlled pneumatic pressure, these components form a force transmission and compensation link, ensuring precise and stable contact between the robotic arm end-effector and the workpiece.

[0063] In the overall structure, a piston chamber is provided inside the upper housing, and piston 7 can move axially up and down within the chamber. Its lower end is fixedly connected to adjusting plate 9 via piston rod 8. A boss structure is provided below adjusting plate 9 for centering the upper ball 10 during the locking and reset phase. The bottoms of the upper and lower housings respectively form symmetrical hemispherical grooves, and the ball assembly is located between the two grooves, forming a spherical pair with multi-degree-of-freedom rotation and micro-displacement capabilities. The ball assembly consists of upper ball 10 and lower ball 11, which are fixedly connected as a whole by connecting rods. Their centers are collinear and coincide with the central axis of the piston assembly in the locked state, thus ensuring symmetrical force and stable posture. Upper ball 10 and lower ball 11 respectively mate with the groove walls of the upper and lower housings, enabling fine-tuning of the angle around the center of the ball, radial displacement, and torsional compensation, forming the core compliant unit of the entire compensation system.

[0064] The device is powered by a gas-driven system. The top cover 5 has a first air inlet and a second air inlet, with air pipe connectors 17 and 18 installed respectively. The two air paths operate independently, each responsible for pre-tightening adjustment and locking / resetting functions. In operation, a certain air pressure is first introduced through air pipe connector 17, creating a constant downward gas pressure at the top of piston 7. This air pressure can be flexibly adjusted via a proportional pressure regulating valve, thereby achieving adjustable control of axial stiffness. When the air pressure is at its working state, piston 7, piston rod 8, and adjusting plate 9 maintain a stable pre-tightened state under the force of the gas spring, and the piston assembly is in a compliant but not locked state. At this time, the entire compensation device can respond freely under external forces, achieving multi-directional micro-displacement and attitude compensation.

[0065] When the end effector of the robotic arm contacts the workpiece, if there is a positional deviation or angular error, the external force first acts on the lower housing. The lower housing generates a small relative torsion and displacement through the interlocking structure between the inner edge of its top and the outer edge of the inner connecting ring 14 at the bottom of the upper housing, thereby achieving torsional compensation around the vertical axis (Z-axis). At the same time, the external force is transmitted through the lower housing to the lower sphere 11, and then through the connecting rod to the upper sphere 10. Since the contact between the sphere assembly and the upper and lower housings is a smooth spherical pair, the friction is minimal. After being subjected to force, the sphere assembly can generate a small-angle rotation and radial displacement in three-dimensional space, achieving adaptive compensation in the lateral (X, Y directions) and angular (Pitch, Yaw directions). During this process, the piston 7 in the piston assembly will move slightly under the action of pneumatic elasticity, achieving axial compression compensation (Z-axis compensation), thereby absorbing the deformation and impact caused by the external load and keeping the contact force between the actuator and the workpiece constant and stable.

[0066] During the compensation motion, the guide and limiting components serve as guides and stroke constraints. Multiple guide and limiting components, preferably three, are evenly distributed circumferentially around the outer side of the spherical assembly, arranged at 120° intervals along the circumference to form an equilateral three-point support, ensuring the symmetry and force balance of the device under unlocking and locking conditions. Each guide and limiting component consists of a connecting rod 12, an upper washer 13, a steel ball 15, and a lower washer 16. The connecting rod 12 rigidly connects the adjusting plate 9 and the upper washer 13. The steel ball 15 is placed in the spherical groove formed by the upper and lower washers, forming a ball-joint-like structure with multi-degree-of-freedom micro-displacement capabilities. When the compensation action occurs, the connecting rod 12 moves upward along with the adjusting plate 9 and the piston rod 8, lifting the upper washer 13. The steel ball 15 performs a combined rolling and sliding motion within the spherical groove, providing low-friction guidance and limiting for the tilting, lateral movement, and torsion of the lower housing. This structure ensures coordinated linkage between the degrees of freedom during the compensation process, making the compensation motion smooth and controllable.

[0067] Through the synergistic effect of air pressure and structure, the device achieves comprehensive compensation in six degrees of freedom: 1. A piston assembly controlled by air pressure provides adjustable flexibility, stiffness, and impact resistance, achieving axial (Z-axis) compression compensation. 2. Low-damping displacement is provided by spherical and rolling pairs, correcting planar position errors and achieving lateral (X / Y-axis) displacement compensation. 3. The lower shell tilts relative to the upper shell in a plane. The micro-rotation of the spherical assembly within the hemispherical groove eliminates assembly angle deviations. The rotation of the spherical assembly around the X-axis compensates for the forward and backward tilt of the lower shell, and the rotation around the Y-axis compensates for the left and right tilt of the lower shell, ultimately achieving tilt angle compensation (Pitch / Yaw direction). 4. The inner and outer eaves latching structure of the lower shell is controlled torsion within a preset displacement space, achieving torsional compliance and torsional compensation (around the Z-axis). 5. The gas spring effect and low spherical rolling friction allow for automatic centering after compensation, absorbing vibration and impact energy. 6. The rolling ball pair of the guide and limiting assembly provides directional constraints and motion limits for the entire system, preventing structural overtravel.

[0068] When the compensation action is completed or when locking and resetting are required, high-pressure locking gas is introduced through the air pipe connector 18. The gas pressure quickly enters the upper region of the piston chamber and pushes the piston 7 to move axially downward. At this time, the piston rod 8, adjusting plate 9, and connecting rod 12 move downward as a whole, pressing the steel ball 15 between the upper shim 13 and the lower shim 16. The relative movement between the spherical pair and the rolling pair is suppressed, and the device changes from a compliant state to a high-rigidity locking state. At the same time, the boss at the bottom of the adjusting plate 9 flattens the top plane of the upper ball 10, applying a return force, so that the upper ball quickly returns to a posture parallel to the cross-section of the device, achieving zero posture. At this time, the collinear axis of the upper and lower balls is completely coincident with the central axis of the piston assembly, ensuring the symmetry and repeatability of the device in the locking state. As the locking action is completed, the gas pressure can be kept constant to maintain the high-rigidity state, or released to atmospheric pressure according to the operation requirements, and enter the next operation cycle.

[0069] In summary, this invention achieves linear displacement compensation in the X, Y, and Z directions and angular compensation in the Pitch, Yaw, and Roll directions (i.e., rotation around the X, Y, and Z axes) of the robotic arm end effector through a multi-dimensional collaborative design involving pneumatic drive, spherical compliance, rolling guidance, latch torsion, and mechanical limiting, thus forming a complete six-degree-of-freedom error compensation system. In operation, it offers advantages such as adjustable stiffness, low friction, rapid response, and precise reset, improving the posture consistency and operational accuracy of the robotic arm end effector when in contact with the workpiece. It has broad application prospects in high-precision assembly, welding, grinding, and precision handling scenarios.

[0070] The above description is merely an embodiment of this utility model, and common knowledge regarding specific structures and characteristics is not described in detail here. It will be apparent to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this utility model is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An end-effector error compensation device for an industrial robotic arm, characterized in that, Includes an upper housing, a lower housing, an adjusting plate (9), an inner connecting ring (14), a piston assembly, a ball assembly, and a guide and limiting assembly; The upper and lower shells are both hollow cavity structures. An inner connecting ring (14) is fixedly installed at the bottom of the upper shell. The main body of the inner connecting ring (14) is a ring-shaped column structure. One end of the inner connecting ring (14) is fixedly connected to the bottom of the upper shell, and the other end is provided with a ring-shaped outer eave structure along the outer periphery. The top of the lower shell is provided with a ring-shaped inner eave that matches the outer eave of the bottom of the upper shell. The inner eave and the outer eave adopt a snap-fit ​​structure. The outer eave snaps onto the inner side of the inner eave, and a preset displacement space is formed between the outer wall of the inner eave and the upper shell. The piston (7) of the piston assembly is installed in the inner cavity of the upper housing, and a sealing structure is provided between its outer wall and the inner cavity wall of the upper housing to form a closed pressure chamber; the piston rod (8) of the piston assembly is coaxially connected to the lower end of the piston (7), and its bottom is fixedly connected to the adjustment plate (9); The bottom of the upper shell and the lower shell are respectively provided with corresponding hemispherical grooves. The two hemispherical grooves are symmetrically arranged and their arc surfaces face each other to form a spherical mating pair. The spherical assembly is placed in the spherical mating pair, and its spherical surface is in close contact with the arc surfaces of the two hemispherical grooves. The bottom of the arc surface of each hemispherical groove is provided with a coaxial cylindrical hole. The axis of the cylindrical hole is coaxial with the central axis of the piston (7) and the piston rod (8). The guide and limiting assembly is located between the upper housing and the lower housing to limit the range of motion of the piston (7) and the lower housing.

2. The industrial robotic arm end-effector error compensation device according to claim 1, characterized in that, The spherical assembly includes an upper sphere (10) and a lower sphere (11). The main bodies of the upper sphere (10) and the lower sphere (11) are both hemispherical structures, and are respectively installed in hemispherical grooves provided in the upper and lower shells. After assembly, the two form a matching spherical sub-structure through the spherical contact area.

3. The industrial robotic arm end-effector error compensation device according to claim 2, characterized in that, Both the upper sphere (10) and the lower sphere (11) are provided with connecting rod structures on their arc surfaces. The bottom of the hemispherical grooves of the upper and lower shells are respectively provided with cylindrical holes. The two connecting rods pass through the corresponding cylindrical holes and are connected to each other.

4. The industrial robotic arm end-effector error compensation device according to claim 3, characterized in that, The diameter of the cylindrical hole is larger than the outer diameter of the connecting rod.

5. The industrial robotic arm end-effector error compensation device according to claim 2, characterized in that, The bottom of the adjustment plate (9) is provided with a boss, which is located above the plane of the upper sphere (10).

6. The industrial robotic arm end-effector error compensation device according to claim 1, characterized in that, The plurality of guide limiting components are arranged circumferentially along the outer side of the ball assembly. Each guide limiting component includes a connecting rod (12), an upper washer (13), a steel ball (15), and a lower washer (16). The bottom of the upper housing has multiple through holes evenly distributed around the outer side of its hemispherical groove. Each through hole has an upper gasket mounting seat at its bottom, and a guide cavity coaxial with the through hole is formed in the upper gasket mounting seat. The bottom of the lower housing has a lower gasket mounting seat that is radially corresponding to the upper gasket mounting seat and located directly below it. The upper gasket (13) can slide axially in the upper gasket mounting seat. The lower gasket (16) is fixedly installed in the lower gasket mounting seat. The upper gasket (13) and the lower gasket (16) are machined together to form a complete spherical groove. The steel ball (15) is placed in the spherical groove. One end of the connecting rod (12) passes through the through hole at the bottom of the upper housing and is fixedly connected to the adjusting plate (9). The other end is fixedly connected to the upper gasket (13).

7. The industrial robotic arm end-effector error compensation device according to claim 6, characterized in that, The number of guide and limiting components is three, and they are arranged circumferentially at 120° intervals along the outer side of the outer edge of the sphere component.

8. The industrial robotic arm end-effector error compensation device according to claim 1, characterized in that, The upper housing includes a top cover (5), a guide plate (4), and an upper frame (3), which are assembled and connected in sequence along the vertical direction of the device to form an integral structure. The top cover (5) is installed at the uppermost end of the upper housing and has a piston chamber inside. The guide plate (4) is located between the bottom of the top cover (5) and the top of the upper frame (3). The guide plate (4) has a guide hole in the middle that matches the diameter of the piston rod (8). The upper frame (3) is located at the lower part of the upper housing and has a hemispherical groove at its bottom. The bottom outer edge of the upper frame (3) is connected to the inner connecting ring (14).

9. The industrial robotic arm end-effector error compensation device according to claim 1, characterized in that, The lower housing includes a lower frame (1) and an outer connecting ring (2). The bottom of the lower frame (1) is provided with a hemispherical groove for the lower housing. The top or side of the lower frame (1) is connected to the outer connecting ring (2) along the circumferential direction. The inner side of the top of the outer connecting ring (2) is provided with the inner edge of the lower housing.

10. The industrial robotic arm end-effector error compensation device according to claim 1, characterized in that, The top cover (5) of the upper housing is provided with a first air inlet and a second air inlet. Both the first air inlet and the second air inlet are connected to the working chamber of the piston top surface inside the top cover (5). The two air inlets are used to input gases with different functions to realize the stiffness adjustment and locking reset control of the piston assembly.

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