End effector for gripping pre-assembled bolt assemblies and its control method

Abstract

This invention relates to the technical field of robot end effectors and automated robot assembly, and particularly to an end effector for gripping pre-assembled bolt assemblies and its control method. The end effector includes: a drive motor; a gripper mechanism disposed on the upper part of the end effector for gripping the bolt head; a tray mechanism disposed on the lower part of the end effector for receiving and blocking washers fitted on the bolt; and a transmission mechanism disposed between the drive motor, the gripper mechanism, and the tray mechanism. The drive motor simultaneously drives the gripper mechanism to perform clamping or opening actions and the tray mechanism to perform extending or retracting actions via the transmission mechanism. This invention uses only one drive motor, coupling the opening / closing of the gripper tip and the extension / retraction of the receiving tray through the upper and lower ends of the transmission mechanism. It eliminates the need for independent actuators and additional control programs, providing bottom support for the washers on the pre-assembled bolts, preventing the washers from easily falling off during handling, and reducing cost and control complexity.

Description

Technical Field

[0001] This invention relates to the field of robot end effectors and automated robot assembly technology, and in particular to an end effector for gripping pre-assembled bolt assemblies and its control method. Background Technology

[0002] In automotive manufacturing, construction machinery, rail transit equipment, and intelligent manufacturing production lines, robots are frequently required to grasp pre-assembled bolt assemblies. Common pre-assembled bolt assemblies mainly include bolts, flat washers, and spring washers. Washers are pre-fitted onto the bolt shank, and existing robot grippers typically only hold the bolt head. During handling, when the bolt axis is horizontal or tilted, the washer may slip off along the bolt due to gravity, leading to washer detachment, cycle interruption, component damage, and ultimately assembly failure. Existing solutions usually employ magnetic adsorption or independent lifting mechanisms. These solutions generally suffer from complex structures, high costs, the need for additional drive sources, and complex timing coordination control by the host computer. Therefore, a robot end effector with a simple structure and control logic, a small number of drives, and the ability to effectively prevent washer detachment is needed. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides an end effector for gripping pre-assembled bolt assemblies and a control method thereof.

[0004] On the one hand, the end effector for gripping pre-assembled bolt assemblies provided by the present invention adopts the following technical solution: An end effector for gripping pre-assembled bolt assemblies includes: Drive motor; The gripper mechanism, located on the upper part of the end effector, is used to grip the bolt head; The pallet mechanism, located at the bottom of the end effector, is used to receive and block the washers fitted on the bolts; The transmission mechanism is located between the drive motor and the gripper mechanism and pallet mechanism; The drive motor drives the gripper mechanism to perform clamping or opening actions and the pallet mechanism to perform extending or retracting actions through the transmission mechanism.

[0005] Optionally, the transmission mechanism includes: The first bevel gear is mounted on the output shaft of the drive motor; The second bevel gear meshes perpendicularly with the first bevel gear; The rocker arm is fixedly connected to the shaft of the second bevel gear and swings as the second bevel gear rotates; The upper end of the rocker arm is connected to the gripper mechanism, and the lower end of the rocker arm is connected to the tray mechanism.

[0006] Optionally, the gripper mechanism includes a fingertip, a linkage assembly, and a guide rod. One end of the guide rod is fixed with a second connecting rod. A fourth sliding groove is provided on the rocker arm. The second connecting rod is inserted into the fourth sliding groove and can rotate. The fingertip is connected to the guide rod through the linkage assembly. When the guide rod moves, it drives the fingertip to open or close through the linkage assembly.

[0007] Optionally, each fingertip corresponds to a linkage assembly, which includes: The first connecting rod is rotatably connected at one end to the sliding block on the guide rod; The second link has one end rotatably connected to the other end of the first link, the middle part of the second link is rotatably mounted on a fixed fulcrum, and the other end of the second link is rotatably connected to the fingertip; The third link is rotatably mounted on a fixed fulcrum at one end, and rotatably connected to the fingertip at the other end.

[0008] Optionally, the pallet mechanism includes a receiving pallet, a cantilever, and a slider; The lower end of the rocker arm is connected to the cantilever arm. A first groove is provided on the rocker arm. A first connecting rod is fixed on the side of the cantilever arm near the rocker arm. The first connecting rod is inserted into the first groove and slides along the first groove. The receiving tray is installed at the end of the cantilever, and the upper surface of the receiving tray is matched with the lower surface of the pre-assembled washer. The end effector also includes a housing, and the drive motor is fixed inside the housing; A second groove is provided on the bottom outer side wall of the outer casing, and a third groove is provided on the side wall of the cantilever rod. One end of the slider is inserted into the second groove, and the other end of the slider is inserted into the third groove. The slider slides along the length direction of the second and third grooves.

[0009] Optionally, the rear sidewall and bottom of the housing are provided with vertical strip-shaped clearance windows. When the joystick swings backward to its limit position, the rear edge of the joystick passes through the clearance window and protrudes outside the housing.

[0010] Optionally, it also includes a receiving pallet assembly, which comprises various receiving pallet units with different inner diameters and different U-shaped opening widths, each receiving pallet unit being detachably mounted at the end of the pallet mechanism.

[0011] Optionally, the two fingertips form a V-shaped clamping groove to achieve automatic centering and positioning of the bolt head.

[0012] Optionally, the control unit makes a status judgment based on the motor rotation angle and current change information, and controls the end effector to complete the opening preparation, workpiece approach, clamping and lifting support, transportation and release actions in sequence.

[0013] On the other hand, the present invention also discloses a grasping control method, comprising the following steps: A grasping control method, characterized by comprising the following steps: S1. Task Module Matching: The control system obtains the specification information of the pre-assembled fasteners to be gripped and prompts the operator or the automated quick-change station to assemble a modular receiving tray that matches the specification for the cantilever connector at the bottom of the gripper.

[0014] S2. Initialization phase: The controller drives the single motor to reverse and seek zero until the gripper assembly is at its maximum opening angle and the receiving tray is at its farthest retracted position. The position of the motor encoder at this time is recorded as the zero point.

[0015] S3, Approaching the target stage: The robotic arm drives the gripper mechanism to move to the gripping point directly above the pre-assembled fastener. At this time, the object to be gripped is within the gripping range of the V-shaped fingertips.

[0016] S4. Linked Grabbing and Adaptive Judgment Phase: The controller sends a forward rotation command to the single motor, which drives the rocker arm to swing. During the rocker arm swing, the upper V-shaped fingertips close inward, while the lower receiving tray extends synchronously directly below the bolt. The controller monitors the operating current of the single motor in real time. When the operating current rises sharply and reaches the preset clamping current threshold, it is determined that the V-shaped fingertips have adhered to and clamped the bolt. At this time, the controller stops the motor's forward rotation and maintains the current holding torque. Due to the fixed proportional linkage characteristic of the mechanism, the system assumes that the receiving tray has synchronously reached the anti-drop position, without the need for additional sensors to confirm the tray position.

[0017] S5. Handling and Assembly Release Stage: The robotic arm moves the fastener above the assembly hole and descends. The controller sends a reverse command to the single motor, and the motor returns to the zero position of step S1. During the reverse process, the lower modular receiving tray retracts synchronously with the full opening of the gripper.

[0018] Compared with the prior art, the present invention has the following technical effects: This invention uses only one drive motor, coupling the opening and closing of the fingertips and the extension and retraction of the receiving tray through the upper and lower ends of the transmission mechanism. The rigid constraints of the mechanical structure ensure the synchronicity of the actions, eliminating the need for independent actuators and additional control programs. It provides bottom support for the washers on the pre-assembled bolts, preventing the washers from easily falling off during transportation, thus reducing costs and control complexity. By determining the motor current threshold in the control method, adaptive clamping is achieved. Once clamping is determined, the rigid constraints of the mechanical structure ensure that the tray has reached the designated position, achieving physical-level safety interlocking. The opening design on the rear side of the outer shell allows the rocker arm to extend outward, making the internal structure more compact. The V-shaped fingertip design enables self-centering clamping of cylindrical bolt heads, resulting in more stable clamping. The bottom receiving tray adopts an independent, detachable, modular design, allowing for quick switching when different sizes of washers are available by replacing the tray module, reducing the hardware cost of the equipment and improving the system's versatility. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the clamps being closed and the tray being extended in the present invention; Figure 2 This is a schematic diagram of the gripper opening and the tray retracting state of the present invention; Figure 3 This is the left view of the present invention; Figure 4 This is a top view of the present invention; Figure 5 This is a schematic diagram of the internal structure of the present invention; Figure 6 This is a schematic diagram of the gripper mechanism in this invention; Figure 7 This is a schematic diagram of the third link and the fingertip in this invention; Figure 8 This is a schematic diagram of the pallet mechanism in this invention; Figure 9 This is the control flowchart of the present invention.

[0020] Explanation of reference numerals in the attached drawings: 1. Drive motor; 2. Transmission mechanism; 21. First bevel gear; 22. Second bevel gear; 23. Rocker arm; 231. First slide groove; 232. Fourth slide groove; 3. Gripper mechanism; 31. Fingertip; 32. Linkage assembly; 321. First link; 3211. First rotating shaft; 322. Second link; 3221. Second rotating shaft; 3222. Third rotating shaft; 3223. Fourth rotating shaft; 323. Third link; 3 231. Fifth pivot; 3232. Sixth pivot; 33. Guide rod; 331. Sliding block; 332. T-shaped slider; 333. Second connecting rod; 4. Pallet mechanism; 41. Receiving pallet; 42. Cantilever rod; 421. First connecting rod; 422. Third slide groove; 43. Slider; 5. Housing; 51. Flange interface; 52. Clearance window; 53. Front housing; 531. Upper housing; 532. Lower housing; 54. Second slide groove. Detailed Implementation

[0021] The following is in conjunction with the appendix Figure 1 - Appendix Figure 9 The present invention will be described in further detail below.

[0022] Reference Figures 1-9 This invention discloses an end effector for gripping pre-assembled bolt assemblies, comprising a drive motor 1, a gripper mechanism 3 located at the upper part, a transmission mechanism 2 located in the middle, a tray mechanism 4 located at the lower part, and a housing 5. The drive motor 1 is fixed inside the housing 5. A front housing 53 is provided on one side of the housing 5, and the front housing 53 is fixed to the housing 5 by bolts. The front housing 53 includes an upper housing 531 and a lower housing 532, which are fixed by bolts. A flange interface 51 is provided on the housing 5, which is used to establish a rigid connection with the end flange of an industrial robotic arm.

[0023] Reference Figure 5 The transmission mechanism 2 includes a first bevel gear 21, a second bevel gear 22, and a rocker arm 23. The output shaft of the drive motor 1 is vertically upward. The first bevel gear 21 is mounted on the output shaft of the drive motor 1, and the second bevel gear 22 meshes perpendicularly with the first bevel gear 21 at a 90-degree angle. The rocker arm 23 is fixedly connected to the rotating shaft of the second bevel gear 22. When the second bevel gear 22 rotates, it drives the rocker arm 23 to rotate. The drive motor 1 performs forward and reverse rotation, and the rocker arm 23 swings back and forth around the axis of the second bevel gear 22.

[0024] Reference Figure 2 , Figure 3 , Figure 5 and Figure 8The lower pallet mechanism 4 includes a receiving pallet 41, a cantilever 42, and a slider 43. The top of the rocker arm 23 is located inside the housing 5, and the bottom of the rocker arm 23 extends to the bottom of the housing 5. The bottom of the rocker arm 23 is connected to the cantilever 42. A first groove 231 is provided on the rocker arm 23. A first connecting rod 421 is fixed on the side of the cantilever 42 near the rocker arm 23. The first connecting rod 421 is inserted into the first groove 231 and can slide along the first groove 231.

[0025] The bottom of the outer casing 5 has two opposite outer sidewalls with second grooves 54, and the cantilever rod 42 has two opposite sidewalls with third grooves 422. A slider 43 is provided between the outer casing 5 and the cantilever rod 42. One end of the slider 43 is inserted into the second groove 54, and the other end of the slider 43 is inserted into the third groove 422. The slider 43 can slide along the length of the second groove 54 and the third groove 422.

[0026] The receiving tray 41 is bolted to the end of the cantilever 42. The receiving tray 41 is U-shaped, with its opening facing forward, and its upper surface matches the lower surface of the pre-assembled washer. This system is equipped with a set of receiving trays, containing individual trays with various inner diameters and U-shaped opening widths. In practical applications, if the outer diameter of the bolt washers in the current batch is too small, only the current receiving tray 41 needs to be replaced.

[0027] Reference Figures 5-7 The gripper mechanism 3 includes a fingertip 31, a connecting rod assembly 32, and a guide rod 33. A sliding block 331 is fixed to one end of the guide rod 33, and a second connecting rod 333 is fixed to the other end. A fourth sliding groove 232 is provided on the rocker arm 23, and the second connecting rod 333 is inserted into the fourth sliding groove 232 and can rotate. The fingertip 31 and the guide rod 33 are connected through the connecting rod assembly 32. When the guide rod 33 moves, the connecting rod assembly 32 causes the two parts to clamp or loosen.

[0028] A sliding block 331 is fixed to one end of the guide rod 33, and T-shaped sliders 332 are fixed to both the upper and lower ends of the sliding block 331. The two T-shaped sliders 332 are symmetrically arranged about the sliding block 331. T-shaped grooves for sliding of the T-shaped sliders 332 are fixed on both the upper housing 531 and the lower housing 532.

[0029] There are two fingertips 31, and the ends of the two fingertips 31 are machined into V-shaped grooves. When the rocker arm 23 is rotated, the guide rod 33 moves forward or backward in a straight line, driving the linkage assembly 32 to make the V-shaped fingertips 31 on both sides open or close in parallel.

[0030] Each fingertip 31 corresponds to a link assembly 32. The link assembly 32 includes a first link 321, a second link 322, and a third link 323. There are two first links 321, one of which is located above the sliding block 331 and the other is located below the sliding block 331. A first rotating shaft 3211 is fixed on the sliding block 331, and one end of the first link 321 is rotatably connected to the first rotating shaft 3211.

[0031] One end of the second link 322 is located between the upper and lower first links 321. A second rotating shaft 3221 is fixed to the end of the second link 322 closer to the first link 321, and the first link 321 is rotatably connected to the second rotating shaft 3221. A third rotating shaft 3222 is fixed on the lower housing 532, and the second link 322 is rotatably connected to the third rotating shaft 3222. A fourth rotating shaft 3223 is fixed to the end of the second link 322 away from the first link 321, and one end of the fingertip 31 is rotatably connected to the fourth rotating shaft 3223.

[0032] A fifth rotating shaft 3231 is rotatably mounted on the lower housing 532. One end of the third connecting rod 323 is rotatably connected to the fifth rotating shaft 3231, and the other end of the third connecting rod 323 is mounted with a sixth rotating shaft 3232, which is rotatably connected to the fingertip 31.

[0033] Since the rocker arm 23 has a certain swing amplitude during operation, in order to minimize the overall size of the end effector, vertical strip-shaped clearance windows 52 are provided on the rear side wall and bottom of the housing 5. When the gripper fingertips 31 are in the fully open state, that is, when the rocker arm 23 swings backward to its limit position, the rear edge of the rocker arm 23 can pass through the opening structure and protrude outside the housing 5, avoiding interference with the housing 5.

[0034] Clamping process: The drive motor 1 drives the first bevel gear 21 to rotate, which in turn drives the second bevel gear 22 to rotate, thereby causing the rocker arm 23 to deflect. The upper end of the rocker arm 23 pushes the second connecting rod 333 to move backward, thereby pushing the guide rod 33 to move backward in a straight line. Through the connecting rod assembly 32, the two V-shaped fingertips 31 close inward to clamp the bolt. At the same time, the lower end of the rocker arm 23 pushes the cantilever rod 42 to move forward, causing the receiving tray 41 to move forward synchronously to directly below the fingertips 31, receiving and preventing the washer on the bolt from falling off.

[0035] Opening process: Drive motor 1 reverses, rocker arm 23 swings in the opposite direction, the upper end of rocker arm 23 pulls guide rod 33 forward, and fingertips 31 open. At the same time, the lower end of rocker arm 23 pulls cantilever rod 42 backward, and receiving tray 41 retracts synchronously, so that bolt assembly is released smoothly.

[0036] This invention also discloses an end effector grasping control method, comprising the following steps: S1, Task Module Matching: The control system obtains the specification information of the pre-assembled fastener to be picked up, including the head diameter, smooth rod diameter, and length, by reading the QR code on the receiving tray 41 or receiving instructions from the upper system. Based on this specification information, the controller displays the model of the required receiving tray 41 on the operation interface, prompting the operator to manually replace it or for the automated quick-change station to pick up a receiving tray 41 matching the specification from the receiving tray 41 library and lock it onto the cantilever rod 42 at the bottom of the end effector through the quick-change interface.

[0037] S2. Initial Zeroing: The controller sends a reverse command to drive motor 1. Drive motor 1 reverses, causing the fingertip 31 to gradually open and the lower receiving tray 41 to retract synchronously via the transmission component. The controller monitors the motor's operating current in real time. When it detects that the mechanism has reached the mechanical hard limit, causing the motor to stall and the operating current to rise sharply and exceed the preset stall judgment threshold, it determines that the gripper fingertip 31 is at its maximum opening angle and the receiving tray 41 has reached its final retraction position. At this time, the controller records the current position of the motor encoder as the zero point, completing the initial calibration. This zeroing action ensures that the starting state of each operation is completely consistent, eliminating accumulated errors.

[0038] S3, Approaching the Target: Based on the coordinates provided by the vision positioning system, the controller controls the robotic arm to move the end effector to the gripping point directly above the fastener to be gripped. At this time, the axis of the fastener falls within the gripping range of the two V-shaped fingertips 31, and the gripper fingertips 31 remain in their maximum open state, so as to approach quickly with a large tolerance.

[0039] S4. Linked Grabbing and Adaptive Judgment: The controller sends a forward rotation command to the drive motor 1. The drive motor 1 rotates forward, causing the rocker arm 23 to swing, and the V-shaped fingertip 31 to close inward. Simultaneously, the lower receiving tray 41 extends. During forward rotation, the controller collects the motor's operating current signal in real time at a predetermined sampling frequency and performs sliding window averaging filtering to filter out instantaneous interference. When the inclined surface of the V-shaped fingertip 31 contacts the fastener and begins to apply radial clamping force, the load on the drive motor 1 increases rapidly, and the operating current rises sharply from the no-load base value. The controller compares the filtered current value with a pre-stored clamping current threshold, which is determined through calibration experiments and corresponds to the clamping force that can reliably clamp without damaging the workpiece. Once the filtered current value reaches or exceeds the clamping current threshold, the controller immediately determines that the V-shaped fingertip 31 has adhered to and clamped the fastener, then stops the motor's forward rotation and switches to torque holding mode, so that the motor continuously outputs holding torque corresponding to the current current. Based on the fixed-proportional linkage characteristic of the mechanism, at the same moment the clamping determination takes effect, the receiving tray 41 has already moved synchronously to the anti-drop position. Therefore, this method does not require a separate receiving tray 41 position sensor for secondary confirmation, and relies entirely on mechanical linkage to ensure that the anti-drop position is correctly reached.

[0040] S5. Handling and Assembly Release: The robotic arm moves the end effector holding the fastener to the designated position. The controller then sends a reverse command to the motor, causing it to reverse and move towards the zero point recorded in step S2. During the reverse process, the upper V-shaped fingertip 31 gradually opens, releasing the fastener; simultaneously, the lower receiving tray 41 retracts backward. When the motor returns to the zero point, the fastener falls into the assembly hole under gravity or with the assistance of the robotic arm, completing the release, and the gripper fingertip 31 returns to its maximum open state. The robotic arm then returns to the picking position, and the system enters the next work cycle, repeating steps S1 to S5.

[0041] This control method utilizes a single motor to achieve a purely mechanical linkage between the opening and closing of the gripper fingertip 31 and the extension and retraction of the receiving tray 41. It achieves sensorless clamping confirmation through current detection and ensures that the receiving tray 41 reaches the anti-drop station through a mechanical linkage ratio. This significantly reduces the number of sensors and control complexity while improving the reliability of the gripping and handling process.

[0042] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An end effector for gripping pre-assembled bolt assemblies, characterized in that, include: Drive motor (1); The gripper mechanism (3) is located on the upper part of the end effector and is used to grip the bolt head; The pallet mechanism (4) is located at the bottom of the end effector and is used to receive and block the washer fitted on the bolt. The transmission mechanism (2) is located between the drive motor (1) and the gripper mechanism (3) and the pallet mechanism (4); The drive motor (1) drives the gripper mechanism (3) to perform clamping or opening actions and the pallet mechanism (4) to perform extending or retracting actions through the transmission mechanism (2).

2. The end effector for gripping pre-assembled bolt assemblies according to claim 1, characterized in that: The transmission mechanism (2) includes: The first bevel gear (21) is mounted on the output shaft of the drive motor (1); The second bevel gear (22) meshes perpendicularly with the first bevel gear (21); The rocker arm (23) is fixedly connected to the shaft of the second bevel gear (22) and swings as the second bevel gear (22) rotates; The upper end of the rocker arm (23) is connected to the gripper mechanism (3) for transmission, and the lower end of the rocker arm (23) is connected to the tray mechanism (4) for transmission.

3. The end effector for gripping pre-assembled bolt assemblies according to claim 2, characterized in that: The gripper mechanism (3) includes a fingertip (31), a linkage assembly (32) and a guide rod (33). One end of the guide rod (33) is fixed with a second connecting rod (333). A fourth sliding groove (232) is provided on the rocker arm (23). The second connecting rod (333) is inserted into the fourth sliding groove (232) and can rotate. The fingertip (31) is connected to the guide rod (33) through the linkage assembly (32). When the guide rod (33) moves, it drives the fingertip (31) to open or close through the linkage assembly (32).

4. The end effector for gripping pre-assembled bolt assemblies according to claim 3, characterized in that: Each fingertip (31) corresponds to a link assembly (32), and the link assembly (32) includes: The first link (321) is rotatably connected at one end to the sliding block (331) on the guide rod (33); The second link (322) is rotatably connected at one end to the other end of the first link (321), the middle part of the second link (322) is rotatably mounted on a fixed fulcrum, and the other end of the second link (322) is rotatably connected to the fingertip (31); The third link (323) is rotatably mounted on a fixed fulcrum at one end and rotatably connected to the fingertip (31) at the other end.

5. The end effector for gripping pre-assembled bolt assemblies according to claim 2, characterized in that: The pallet mechanism (4) includes a receiving pallet (41), a cantilever (42), and a slider (43). The lower end of the rocker arm (23) is connected to the cantilever arm (42). A first groove (231) is provided on the rocker arm (23). A first connecting rod (421) is fixed on the side of the cantilever arm (42) near the rocker arm (23). The first connecting rod (421) is inserted into the first groove (231) and slides along the first groove (231). The receiving tray (41) is installed at the end of the cantilever (42), and the upper surface of the receiving tray (41) is matched with the lower surface of the pre-assembled washer. The end effector also includes a housing (5), and a drive motor (1) is fixed inside the housing (5); A second groove (54) is provided on the bottom outer side wall of the outer casing (5), and a third groove (422) is provided on the side wall of the cantilever rod (42). One end of the slider (43) is inserted into the second groove (54), and the other end of the slider (43) is inserted into the third groove (422). The slider (43) slides along the length direction of the second groove (54) and the third groove (422).

6. The end effector for gripping pre-assembled bolt assemblies according to claim 1, characterized in that: The rear sidewall and bottom of the outer casing (5) are provided with vertical strip-shaped clearance windows (52). When the rocker arm (23) swings backward to the limit position, the rear edge of the rocker arm (23) passes through the clearance window (52) and is exposed outside the outer casing (5).

7. The end effector for gripping pre-assembled bolt assemblies according to claim 1, characterized in that: It also includes a receiving pallet assembly, which contains a variety of receiving pallet (41) units with different inner diameters and different U-shaped opening widths, and each receiving pallet (41) unit is detachably installed at the end of the pallet mechanism (4).

8. The end effector for gripping pre-assembled bolt assemblies according to claim 4, characterized in that: Two fingertips (31) form a V-shaped clamping groove to achieve automatic centering and positioning of the bolt head.

9. The end effector for gripping pre-assembled bolt assemblies according to claim 1, characterized in that: The control unit makes status judgments based on the motor rotation angle and current change information, and controls the end effector to complete the opening preparation, workpiece approach, clamping and lifting support, transportation and release actions in sequence.

10. A method for gripping a pre-assembled bolt assembly of an end effector as described in any one of claims 1 to 9, characterized in that... This includes the following steps: S1: Select a suitable receiving tray (41); S2: Record the zero position of the drive motor (1); S3: The robot drives the end effector to approach the pre-assembled bolt assembly; S4: The drive motor (1) rotates to close the fingertip (31) to hold the bolt head, and the receiving tray (41) moves forward synchronously to the bottom of the washer to form support; S5: The robot moves the bolt assembly to the designated position, controls the fingertip (31) to open, and the receiving tray (41) retracts synchronously to complete the release.

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