Quick-change structure and mechanical arm thereof

Abstract

The utility model discloses a quick change structure and mechanical arm belong to mechanical arm technical field, include: first connecting piece is installed on the first object, be provided with at least two limit hole, and first limit wall, and mounting surface on this first connecting piece, and limit hole has mounting hole position and locking hole position, second connecting piece is installed on the second object, be provided with a plurality of limit pieces on this second connecting piece, every limit piece all is provided with second limit wall, movable element moves between first position and second position with respect to this first connecting piece through power drive, when movable element moves from first position to second position, movable element at least partial push a plurality of limit pieces moves from mounting hole position to locking hole position to make second limit wall resist on first limit wall, only need to drive through external power of this application, need not tool to complete the unlocking and the connection between two objects, is applicable to the scene of frequent installation and disassembly.

Description

Technical Field

[0001] This utility model relates to the field of robotic arm technology, and in particular to a quick-change structure and its robotic arm. Background Technology

[0002] In fields such as industrial automation, machining, and logistics handling, the rapid connection and separation of components can effectively improve operational efficiency. For example, as a multi-degree-of-freedom device, a robotic arm often requires the replacement of its end effector (such as grippers, welding guns, and inspection probes) according to different tasks to achieve multi-functional operations such as grasping, welding, and inspection.

[0003] In existing technologies, the connection of objects (such as the end effector of a robotic arm and the actuator) usually uses traditional fasteners such as bolts. The connection and separation process relies on manual operation: bolts need to be tightened or loosened one by one using tools such as wrenches and screwdrivers. The entire installation or disassembly process is time-consuming and cumbersome, especially in scenarios where actuators are frequently replaced, which can lead to excessive downtime for the equipment.

[0004] To address the aforementioned issues, a quick-change structure that requires no tools and can be automatically locked is required. Utility Model Content

[0005] This utility model provides a quick-change structure and its robotic arm to solve the problems in the prior art.

[0006] The present invention adopts the following technical solution: a quick-change structure for connecting a first object and a second object, the quick-change structure comprising: a first connector mounted on the first object, the first connector having at least two limiting holes, a first limiting wall located at the end of the corresponding limiting hole, and a mounting surface opposite to the first limiting wall, each limiting hole having a mounting hole position and a locking hole position; a second connector mounted on the second object, the second connector having limiting members corresponding one-to-one with a plurality of limiting holes, each limiting member having a second limiting wall; and a movable member driven by power to move relative to the first connector at a first position and a second position. The movable member moves between positions; when the movable member is in the first position, several limiting members can pass through the corresponding mounting holes so that the second connecting member abuts against the mounting surface; when the movable member moves from the first position to the second position, the movable member at least partially pushes several limiting members from the mounting holes to the locking holes so that the second limiting wall abuts against the first limiting wall. The locking holes are used to restrict the lateral movement of the limiting members relative to the first connecting member, and the first limiting wall is used to restrict the longitudinal movement of the limiting members relative to the first connecting member; when the movable member moves from the second position to the first position, the movable member at least partially pushes several limiting members from the locking holes to the mounting holes.

[0007] Preferably, the limiting hole is configured as a round hole and a U-shaped groove located on the side of the round hole and communicating with it; the limiting member is configured as a pin and a protrusion located at the end of the pin, the side of the protrusion connected to the pin is the second limiting wall, the diameter of the pin is adapted to the width of the U-shaped groove; the round hole is the mounting hole and the U-shaped groove is the locking hole.

[0008] Preferably, the outer end of the circular hole is chamfered.

[0009] Preferably, the movable component is rotatably mounted on the first connecting member, and the movable component is provided with elongated slots corresponding to a plurality of limiting members; when the second connecting member abuts against the mounting surface, the protrusion is at least partially located in the corresponding elongated slot; when the movable component rotates in the forward direction, the first end of the elongated slot pushes the protrusion, so that the limiting member moves from the mounting hole to the locking hole; when the movable component rotates in the reverse direction, the second end of the elongated slot pushes the protrusion, so that the limiting member moves from the locking hole to the mounting hole.

[0010] Preferably, the protrusion is configured as a columnar structure, and the first connector is provided with a positioning block corresponding to the limiting hole. The positioning block has an arc-shaped surface that is coaxial with the same diameter as the circular hole; the diameter of the protrusion is adapted to the diameter of the corresponding circular hole.

[0011] Preferably, the movable part is provided with a clearance slot corresponding to a plurality of elongated slots; when the movable part rotates, the positioning block is movably positioned in the corresponding clearance slot.

[0012] Preferably, the first connector has three limiting holes, which are evenly distributed around the pivot of the movable part.

[0013] Preferably, the movable component is provided with a sector-shaped internal gear ring coaxially arranged with its rotating shaft, and the first connecting component is equipped with a rotary drive source. The output shaft of the rotary drive source is coaxially fixedly connected with a gear, which meshes with the internal gear ring.

[0014] Preferably, the first connector has a positioning ring formed on one side of the mounting surface, and the outer peripheral wall of the positioning ring is provided with a tapered surface. The second connector is configured as a ring structure and is sleeved on the positioning ring.

[0015] A robotic arm includes a plurality of articulated arms connected in sequence and a quick-change structure. Each pair of adjacent articulated arms is connected by a slip ring structure. The articulated arm at the end of the robotic arm is the first object, and the actuator connected to the robotic arm is the second object.

[0016] The above-mentioned technical solutions adopted in the embodiments of this utility model can achieve the following beneficial effects: In existing designs, the connection between two objects is typically achieved using fasteners such as bolts, requiring manual operation. This application, however, only requires external power and no tools to unlock and connect the two objects, making it suitable for scenarios involving frequent installation and disassembly. For example, in the field of robotic arms, the first object is the articulated arm at the end of the robotic arm, and the actuators connected to the robotic arm (welding gun, gripper, detection probe, etc.) are the second object. By pre-installing different second connectors on the corresponding actuators, the robotic arm can quickly switch between welding guns, grippers, and detection probes, reducing equipment downtime and improving efficiency. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of this invention, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a three-dimensional structural diagram of the quick-change structure of this utility model; Figure 2 This is a sectional view of the quick-change structure of this utility model; Figure 3 This is a schematic diagram of the internal structure of the quick-change structure of this utility model; Figure 4 This is a schematic diagram showing the connection between the gear and the internal gear ring of this utility model; Figure 5 This is an exploded view of the movable part and the first connecting part of this utility model; Figure 6 Explosion of the first connector, second connector, and movable part of this utility model Figure 1 ; Figure 7 Explosion of the first connector, second connector, and movable part of this utility model Figure 2 ; Figure 8 This is a schematic diagram of the movable part of this utility model in the first position; Figure 9 This is a schematic diagram of the movable part of this utility model in the second position; Figure 10 This is a schematic diagram showing the position of the limiting member when the movable part of this utility model is in the first position; Figure 11 This is a schematic diagram showing the position of the limiting member when the movable part of this utility model is in the second position; Figure 12 This is a three-dimensional structural diagram of the robotic arm and quick-change structure of this utility model; Figure 13 This is a sectional view of the robotic arm and quick-change structure of this utility model.

[0018] Figure Labels 1-First connector; 11-Limiting hole; 111-Mounting hole; 112-Locking hole; 12-First limiting wall; 13-Mounting surface; 14-Positioning block; 141-Arc-shaped surface; 15-Positioning ring; 16-Motor frame; 17-Outer shell; 2-Second connecting member; 21-Limiting member; 211-Pin; 212-Protrusion; 213-Second limiting wall; 3-Moving part; 31-Long slot; 311-First end; 312-Second end; 32-Allowing slot; 33-Internal toothed ring; 4- Rotary drive source; 5- Gear; 6-Articulated arm; 61-Rotation axis; 7-Slip ring structure; 71-Conductive ring; 72-Brush. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by this utility model in order to achieve the intended utility model purpose, the following detailed description of the specific implementation methods, structure, features and effects of this utility model is provided in conjunction with the accompanying drawings and preferred embodiments.

[0020] The technical solutions provided by the various embodiments of this utility model are described in detail below with reference to the accompanying drawings.

[0021] Reference Figures 1 to 13 As shown, this utility model embodiment provides a quick-connect structure for connecting a first object and a second object, thereby achieving a quick connection between the first object and the second object. The quick-connect structure mainly includes a first connector 1, a second connector 2, and a movable component 3.

[0022] The first connector 1 is mounted on the first object. The first connector 1 is provided with at least two limiting holes 11, a first limiting wall 12 located at the end of the corresponding limiting hole 11, and a mounting surface 13 disposed opposite to the first limiting wall 12 (generally, the first connector 1 has three limiting holes 11, which are evenly distributed around the axis of rotation of the movable member 3). Each limiting hole 11 has a mounting hole position 111 and a locking hole position 112. The second connector 2 is mounted on the second object. The second connector 2 is provided with limiting members 21 corresponding one-to-one with a plurality of limiting holes 11. Each limiting member 21 is provided with a second limiting wall 213. The movable member 3 is driven by power to move relative to the first connector 1 between a first position and a second position. When the movable component 3 is in the first position, several limiting components 21 can be inserted into the corresponding mounting holes 111 (e.g., Figure 8 and Figure 10), so that the second connector 2 abuts against the mounting surface 13; when the movable member 3 moves from the first position to the second position, the movable member 3 at least partially pushes a plurality of limiting members 21 from the mounting hole 111 to the locking hole 112 (e.g. Figure 9 and Figure 11 The second limiting wall 213 abuts against the first limiting wall 12. The locking hole 112 is used to restrict the lateral movement of the limiting member 21 relative to the first connecting member 1, and the first limiting wall 12 is used to restrict the longitudinal movement of the limiting member 21 relative to the first connecting member 1. When the movable member 3 moves from the second position to the first position, the movable member 3 can at least partially push several limiting members 21 from the locking hole 112 to the mounting hole 111.

[0023] This quick-change structure achieves rapid docking and separation of the first connector 1 and the second connector 2 through the driving of the movable part 3: the first connector 1 is pre-assembled on the first object, and the second connector 2 is pre-assembled on the second object; when the movable part 3 is in its initial state (the movable part 3 is in the first position), the mounting hole 111 of the first connector 1 allows the limiting member 21 of the second connector 2 to be inserted. The second connector 2 approaches the first connector 1, and its limiting member 21 aligns with the limiting hole 11 of the first connector 1, and is inserted longitudinally until it fits against the mounting surface 13 (i.e., the second connector 2 abuts against the mounting surface 13 of the first connector 1), completing the initial positioning of the second connector 2 relative to the first connector 1.

[0024] An external power drive moves the movable part 3 relative to the first connecting part 1, pushing the limiting part 21 from the mounting hole 111 to the locking hole 112. The size of the locking hole 112 matches that of the limiting part 21, restricting the lateral movement of the limiting part 21. The second limiting wall 213 on the limiting part 21 abuts against the first limiting wall 12 of the first connecting part 1, restricting the longitudinal movement of the limiting part 21. This, combined with the second connecting part 2 abutting against the mounting surface 13 (preventing axial separation), achieves a stable connection between the second connecting part 2 and the first connecting part 1. Conversely, the power device drives the movable part 3 in the opposite direction, moving it from the second position (locked position) back to the first position (initial position), pushing the limiting part 21 laterally from the locking hole 112 back to the mounting hole 111, releasing the dual lateral and longitudinal limiting.

[0025] In summary, existing designs typically connect two objects using fasteners such as bolts, requiring manual operation. This application, however, only requires external power and no tools to unlock and connect the two objects, making it suitable for scenarios involving frequent installation and disassembly. For example, in the field of robotic arms, the first object is the articulated arm 6 at the end of the robotic arm, and the actuators connected to this robotic arm (welding gun, gripper, detection probe, etc.) are the second objects. Different second connectors 2 are pre-installed on the corresponding actuators, allowing the robotic arm to quickly switch between the welding gun, gripper, and detection probe, reducing equipment downtime and improving efficiency.

[0026] In some practical applications, based on the above implementation method: refer to Figures 2 to 6 As shown, the limiting hole 11 is configured as a round hole and a U-shaped groove located on the side of the round hole and communicating with it (the outer end of the round hole can be chamfered to facilitate the insertion of the limiting member 21); the limiting member 21 is configured as a pin 211 and a protrusion 212 located at the end of the pin 211 (or a pin with a threaded end can be used, which is fixedly installed on the second connector 2 by the thread), the side of the protrusion 212 connected to the pin 211 is the second limiting wall 213, and the diameter of the pin 211 is adapted to the width of the U-shaped groove; the round hole is the mounting hole 111, and the U-shaped groove is the locking hole 112.

[0027] In this embodiment, the movable part 3 is in its initial position (undriven state). The second connecting part 2 (connected to the second object) drives the limiting part 21 to move towards the first connecting part 1. The pin 211 is inserted into the round hole (mounting hole 111) until the end face of the second connecting part 2 abuts against the mounting surface 13 of the first connecting part 1, completing the longitudinal positioning. At this time, the protrusion 212 is located above the round hole and has not entered the U-shaped groove. Then, the power device (such as a motor or cylinder) drives the movable part 3 to move relative to the first connecting part 1. The movable part 3 contacts the limiting part 21, pushing the pin 211 to slide from the round hole into the U-shaped groove (locking hole 112). At this time, the second limiting wall 213 of the protrusion 212 fits tightly against the first limiting wall 12 of the first connecting part 1 (i.e., the inner wall of the U-shaped groove), preventing the second connecting part 2 from separating longitudinally, thus completing the locking of the first connecting part 1 and the second connecting part 2.

[0028] Specifically, refer to Figures 3 to 5As shown, the movable member 3 is rotatably mounted on the first connecting member 1. The movable member 3 is provided with elongated slots 31 (i.e., waist-shaped holes, with the length direction along the rotation trajectory of the movable member 3) corresponding one-to-one with a plurality of limiting members 21. When the second connecting member 2 abuts against the mounting surface 13, the protrusion 212 is at least partially located in the corresponding elongated slot 31. When the movable member 3 rotates in the forward direction, the first end 311 of the elongated slot 31 pushes the protrusion 212, so that the limiting member 21 moves from the mounting hole 111 to the locking hole 112. When the movable member 3 rotates in the reverse direction, the second end 312 of the elongated slot 31 pushes the protrusion 212, so that the limiting member 21 moves from the locking hole 112 to the mounting hole 111.

[0029] In some practical applications, based on the above implementation, the protrusion 212 is configured as a columnar structure (e.g. Figure 6 The first connecting member 1 is provided with a positioning block 14 corresponding to the limiting hole 11. The positioning block 14 has an arc-shaped surface 141 that is coaxial with the circular hole and has the same diameter (e.g., Figure 6 The diameter of the protrusion 212 is adapted to the diameter of the corresponding circular hole. Therefore, the multiple circular holes can achieve initial lateral positioning after the insertion of the limiting member 21. After the multiple protrusions 212 are inserted into the corresponding arc-shaped surface 141, the multiple arc-shaped surfaces 141 can limit the lateral displacement of the entire second connecting member 2.

[0030] Furthermore, the movable component 3 is provided with clearance slots 32 corresponding one-to-one with a plurality of elongated slots 31 (e.g., Figure 7 When the movable part 3 rotates, the positioning block 14 is movably positioned within the corresponding clearance slot 32. Since the positioning block 14 on the first connecting part 1 needs to be arranged close to the limiting hole 11, and the movable part 3 is prone to interference with the positioning block 14 when it rotates, the clearance slot 32 (arc-shaped or waist-shaped) can reserve rotation space for the positioning block 14 without increasing the axial or longitudinal dimensions of the movable part 3, making the overall structure more compact and suitable for installation in confined spaces.

[0031] In this embodiment, the movable member 3 rotates forward around the pivot, and the elongated slot 31 rotates synchronously with the movable member 3. At this time, the inner wall of the first end 311 of the elongated slot 31 contacts the side of the protrusion 212, so that the limiting member 21 slides into the U-shaped groove (locking hole 112). When the movable member 3 rotates, the positioning block 14 slides in the clearance groove 32 of the movable member 3 to avoid interference between the positioning block 14 and the movable member 3, ensuring that the rotation angle of the movable member 3 is not hindered. When the movable member 3 rotates in the opposite direction, the inner wall of the second end 312 of the elongated slot 31 contacts the other side of the protrusion 212, and the limiting member 21 slides back into the round hole (installation hole 111). Therefore, the second connecting member 2 can be pulled out longitudinally, completing the separation of the first connecting member 1 and the second connecting member 2.

[0032] In some practical applications, based on any of the above embodiments, the movable element 3 can be powered by the following structure: (Refer to...) Figures 2 to 4 As shown, the movable part 3 is provided with a sector-shaped internal gear ring 33 coaxially arranged with its rotating shaft, and a rotary drive source 4 is installed on the first connecting part 1. The output shaft of the rotary drive source 4 is coaxially fixedly connected to a gear 5, which meshes with the internal gear ring 33. The rotary drive source 4 is generally a servo motor (or idler motor). When it is running, the precise angular rotation of the movable part 3 can be achieved through the transmission between the gear 5 and the internal gear ring 33. At the same time, the servo motor can withstand strong torque to ensure the connection stability between the first connecting part 1 and the second connecting part 2.

[0033] In some practical applications, the first connector 1 also includes a motor frame 16 and a housing 17 (e.g., Figure 1 and Figure 2 The motor frame 16 is bolted to the main body of the first connecting piece 1, forming a gap for the rotation of the movable part 3, which facilitates the installation and disassembly of the movable part 3; the outer shell 17 encloses the rotary drive source 4, gear 5, internal gear ring 33 and other structures, which not only serve as protection, but also as a base for connecting with the first object.

[0034] In some practical applications, the first connector 1 has a positioning ring 15 formed on one side of the mounting surface 13 (e.g., Figure 2 The outer peripheral wall of the positioning ring 15 is provided with a tapered surface. The second connector 2 is configured as a ring structure. The second connector 2 is sleeved on the positioning ring 15. The positioning ring 15 is provided to guide the second connector 2 close to the mounting surface 13 to ensure the coaxiality between the two when the second connector 2 abuts against the first connector 1.

[0035] Reference Figures 12 to 13 As shown, a robotic arm includes multiple articulated arms 6 connected in sequence and a quick-change structure as described above. Each pair of adjacent articulated arms 6 is connected by a slip ring structure 7. The articulated arm 6 at the end of the robotic arm is the first object, and the actuator connected to the robotic arm is the second object. A pneumatically driven rotating shaft 61 is provided inside the end of the next-level robotic arm. The slip ring structure 7 includes a conductive ring 71 and a brush 72. The first object is mounted on the articulated arm 6 at the end of the robotic arm, with the mounting surface 13 facing outwards.

[0036] Adjacent joint arms 6 are connected by a slip ring structure 7 and a rotating shaft 61; the rotating shaft 61 of the next-level joint arm 6 is connected to the previous-level joint arm 6, driving it to rotate, and the quick-change structure moves synchronously with the end joint arm 6.

[0037] The slip ring structure 7, as an existing technology, is used for electrical connection between two articulated arms 6. Specifically, a conductive ring 71 is annularly fitted around the outside of the rotating shaft 61 and fixed to the next-level articulated arm 6 (not rotating with the rotating shaft 61). The outer ring of the conductive ring 71 is connected to the input power supply, control signals, etc. A brush 72 is fixed to the end of the rotating shaft 61 (rotating synchronously with the rotating shaft 61). Its bristles (such as precious metal alloy wire) make frictional contact with the inner ring of the conductive ring 71, transmitting the electrical signals of the conductive ring 71 to the next-level articulated arm 6. This slip ring structure 7 allows for simultaneous rotational movement of the two articulated arms while allowing multiple articulated arms of the robotic arm to rotate at any angle, avoiding the wiring entanglement problem caused by excessive rotation between the two articulated arms 6 in traditional methods.

[0038] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to a preferred embodiment, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A quick-change structure for connecting a first object and a second object, characterized in that, The quick-change structure includes: The first connector (1) is installed on the first object. The first connector (1) is provided with at least two limiting holes (11), a first limiting wall (12) located at the end of the corresponding limiting hole (11), and a mounting surface (13) disposed opposite to the first limiting wall (12). Each limiting hole (11) has a mounting hole (111) and a locking hole (112). The second connector (2) is installed on the second object. The second connector (2) is provided with a limiting member (21) corresponding to a plurality of limiting holes (11). Each limiting member (21) is provided with a second limiting wall (213). The movable part (3) is driven by power to move between a first position and a second position relative to the first connecting part (1); When the movable member (3) is in the first position, a plurality of limiting members (21) can pass through the corresponding mounting holes (111) so that the second connecting member (2) abuts against the mounting surface (13); when the movable member (3) moves from the first position to the second position, the movable member (3) at least partially pushes a plurality of limiting members (21) from the mounting holes (111) to the locking holes (112) so that the second limiting wall (213) abuts against the first limiting wall (12), the locking hole (112) is used to restrict the lateral movement of the limiting member (21) relative to the first connecting member (1), and the first limiting wall (12) is used to restrict the longitudinal movement of the limiting member (21) relative to the first connecting member (1); when the movable member (3) moves from the second position to the first position, the movable member (3) at least partially pushes a plurality of limiting members (21) from the locking holes (112) to the mounting holes (111).

2. The quick-change structure according to claim 1, characterized in that, The limiting hole (11) is configured as a round hole and a U-shaped groove located on the side of the round hole and communicating with it; the limiting member (21) is configured as a pin (211) and a protrusion (212) located at the end of the pin (211), the side of the protrusion (212) connected to the pin (211) is the second limiting wall (213), the diameter of the pin (211) is adapted to the width of the U-shaped groove; the round hole is the mounting hole (111), and the U-shaped groove is the locking hole (112).

3. The quick-change structure according to claim 2, characterized in that, The outer end of the circular hole is chamfered.

4. The quick-change structure according to claim 2, characterized in that, The movable part (3) is rotatably mounted on the first connecting part (1). The movable part (3) is provided with elongated slots (31) corresponding to a plurality of limiting parts (21). When the second connecting part (2) abuts against the mounting surface (13), the protrusion (212) is at least partially located in the corresponding elongated slot (31). When the movable part (3) rotates in the forward direction, the first end (311) of the elongated slot (31) pushes the protrusion (212) so that the limiting part (21) moves from the mounting hole (111) to the locking hole (112). When the movable part (3) rotates in the reverse direction, the second end (312) of the elongated slot (31) pushes the protrusion (212) so that the limiting part (21) moves from the locking hole (112) to the mounting hole (111).

5. A quick-change structure according to claim 4, characterized in that, The protrusion (212) is configured as a columnar structure. The first connector (1) is provided with a positioning block (14) corresponding to the limiting hole (11). The positioning block (14) has an arc surface (141) that is coaxial with the same diameter as the circular hole. The diameter of the protrusion (212) is adapted to the diameter of the corresponding circular hole.

6. A quick-change structure according to claim 5, characterized in that, The movable part (3) is provided with a clearance slot (32) corresponding to a number of long slots (31); when the movable part (3) rotates, the positioning block (14) is movably set in the corresponding clearance slot (32).

7. A quick-change structure according to claim 4, characterized in that, The first connector (1) has three limiting holes (11) which are evenly distributed around the pivot of the movable part (3).

8. A quick-change structure according to claim 4, characterized in that, The movable part (3) is provided with a fan-shaped internal gear ring (33) coaxially arranged with its rotating shaft. The first connecting part (1) is equipped with a rotary drive source (4). The output shaft of the rotary drive source (4) is coaxially fixedly connected with a gear (5). The gear (5) meshes with the internal gear ring (33).

9. A quick-change structure according to claim 1, characterized in that, The first connector (1) has a positioning ring (15) formed on one side of the mounting surface (13). The outer peripheral wall of the positioning ring (15) is provided with a tapered surface. The second connector (2) is configured as a ring structure and is sleeved on the positioning ring (15).

10. A robotic arm, characterized in that, It includes a plurality of articulated arms (6) connected in sequence, and a quick-change structure as described in any one of claims 1-9. Each pair of adjacent articulated arms (6) are connected by a slip ring structure (7). The articulated arm (6) at the end of the robotic arm is the first object, and the actuator connected to the robotic arm is the second object.

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