A welding device for super-large-diameter precision ring track

Abstract

A kind of welding device for super diameter precision annular track, it is related to welding device field, including welding robot and vibration robot, the bottom of welding robot and vibration robot is provided with base saddle;The base saddle is U-shaped frame, the U-shaped groove opening direction of U-shaped frame is away from the welding robot or vibration robot connected, the opposite sides of base saddle are provided with clamping screw and counterweight;Base saddle includes two clamping plates spaced apart in parallel and fixed plate connected between two clamping plates.The utility model is used to solve the technical problem of high labor intensity of manual welding, and the automatic equipment using magnetic chuck is easy to produce magnetic field influence welding quality.

Description

Technical Field

[0001] This utility model relates to the field of welding equipment, specifically a welding device for ultra-large diameter precision circular tracks. Background Technology

[0002] As a highly customized core engineering component, the ultra-large diameter precision circular track is a key carrier for achieving the synergy between the "rotational degree of freedom" of ultra-large scale systems and industrial-grade precision. It is widely used in automobile manufacturing, aerospace and military industries, scientific research and testing, medical imaging and special structures.

[0003] Given the customized nature and large size of ultra-large diameter precision circular tracks, "segment manufacturing followed by on-site welding" has become the only technical approach that balances cost control, transportation feasibility, and final precision requirements. In the segment manufacturing stage, the segment length must be strictly controlled within the range of 2.5m to 4m. This length limitation stems primarily from the load-bearing capacity of existing transportation equipment and the spatial constraints of the transportation scenario, ensuring that the segmented components can be safely and efficiently transported to the installation site. The beveling design employs a narrow-gap U-shaped bevel with a 1mm to 5mm blunt edge gap. This design helps reduce welding filler and welding stress while ensuring penetration at the bevel root, laying the foundation for subsequent welding quality. Regarding precision control, the flatness of a single segment must be ≤0.01mm / m, and the flatness of the entire ring must be ≤0.05mm. Such stringent precision standards are to meet the high requirements of downstream applications for the stability and positioning accuracy of the circular track.

[0004] Regarding welding process selection, manual arc welding is still widely used in the industry, employing multi-layer, multi-pass welding. Regarding the view in some literature that "manual arc welding has a higher line energy density, leading to greater deformation," an objective analysis is needed: In reality, through precise adjustments of key parameters such as welding current and voltage by professional technicians, manual arc welding can effectively control the line energy density within a reasonable range, thereby achieving effective control of welding quality. In complex special welding scenarios such as ultra-large diameter precision circular tracks, due to the special structure of the components, extremely high precision requirements, and complex and variable on-site welding environment, manual arc welding remains the mainstream welding method in the industry due to its advantages of high operational flexibility and good adaptability to the on-site environment.

[0005] However, existing manual arc welding technology has some problems in practical applications, which restrict the manufacturing efficiency and quality stability of ultra-large diameter precision circular tracks: on the one hand, manual welding is extremely labor-intensive, requiring long periods of focused work, which consumes a lot of physical strength and energy from the operators; on the other hand, welding quality is highly dependent on the operator's experience, skill level and working conditions. Even experienced technicians cannot guarantee that the quality of each weld is completely consistent, making it difficult for key precision indicators such as the flatness of the entire circular track to consistently meet precision requirements. Moreover, manual welding is inefficient and cannot meet the growing market demand. On the other hand, since ultra-large diameter precision circular tracks are all custom-made, the track diameter, structural dimensions, precision requirements, site conditions, and installation locations vary greatly from project to project. When seeking alternative solutions, using batch automated welding equipment not only results in extremely high initial equipment investment costs, but also in complex and time-consuming equipment changeover and adjustment processes, making it difficult to quickly adapt to the personalized needs of different projects. In addition, automated equipment has strict requirements on the spatial layout of the installation site. In some welding processes using robots, magnetic chucks are often used to attach the welding robot to the area to be welded for ease of installation. However, the magnetic field generated by the magnetic chuck can cause magnetic blow of the arc, which in turn affects the welding quality. Utility Model Content

[0006] The present invention aims to provide a welding device for ultra-large diameter precision circular tracks, in order to solve the technical problems of high labor intensity in manual welding and the tendency of automated equipment using magnetic chucks to generate magnetic fields that affect welding quality.

[0007] To solve the above technical problems, the specific solution adopted by this utility model is as follows: a welding device for ultra-large diameter precision circular track, including a welding robot and a vibration robot, and a base saddle is provided at the bottom of both the welding robot and the vibration robot.

[0008] The base saddle is a U-shaped frame, with the U-shaped groove opening facing away from the welding robot or vibration robot being connected. Clamping screws and counterweights are provided on both opposite sides of the base saddle.

[0009] The base saddle includes two clamping plates arranged in parallel and spaced apart, and a fixing plate connected between the two clamping plates. Both the welding robot and the vibration robot have a mounting base at their bottom. The mounting base has a first positioning hole, and the fixing plate has a second positioning hole corresponding to the first positioning hole. The base fastening screw can pass through the first positioning hole and the second positioning hole to fix the mounting base and the base saddle together. The mounting base has a first positioning pin hole, and the fixing plate has a second positioning pin hole corresponding to the first positioning pin hole. The positioning pin can pass through the first positioning pin hole and the second positioning pin hole to define the relative position of the mounting base and the base saddle.

[0010] As a further optimization of the above technical solution, the bottom and sidewalls of the U-shaped groove of the base saddle are perpendicular to each other.

[0011] As a further optimization of the above technical solution, the base fastening screws and positioning pins are arranged opposite each other.

[0012] As a further optimization of the above technical solution, the clamping plate and the fixing plate are an integral structure, or the clamping plate and the fixing plate are separate structures and are fixedly connected.

[0013] As a further optimization of the above technical solution, the counterweight is fixed on the connecting plate, and the connecting plate is connected to the side of the base saddle.

[0014] As a further optimization of the above technical solution, the base saddle is used to be installed on the rail to be welded, and the clamping plate has clamping holes, so that the clamping screws can pass through the clamping holes and abut against the side wall of the rail.

[0015] As a further optimization of the above technical solution, the first positioning hole is a T-shaped open hole, and the second positioning hole is a cylindrical threaded hole.

[0016] As a further optimization of the above technical solution, the welding robot is equipped with a laser-TIG welding composite welding torch and a laser contour detector.

[0017] As a further optimization of the above technical solution, an electromagnetic vibrator is installed on the vibration robot.

[0018] As a further optimization of the above technical solution, both the welding robot and the vibration robot are four-axis robots.

[0019] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0020] 1. A welding robot and a vibration robot work together. After the welding robot completes the weld, the vibration robot immediately performs online vibration stress relief treatment. Through layer-by-layer vibration treatment, the deformation of a single layer is reduced, and secondary deformation caused by overall tempering after the ring rail welding is avoided, thus completely eliminating residual stress.

[0021] 2. This utility model abandons the magnetic chuck fixing method, which easily leads to arc blow, and adopts a mechanical fixing structure consisting of a mounting base, a base saddle, positioning pins, and fastening screws. The positioning pins ensure precise positioning of the mounting base and the base saddle, the base fastening screws pass through the first and second positioning holes to achieve a firm connection, and the clamping screws abut against the side wall of the track through the clamping holes, ensuring the stability of the robot's relative position to the weld seam during operation and avoiding interference from the magnetic field on the welding quality.

[0022] 3. This utility model adopts a lightweight and modular design. The welding robot and vibration robot are easy to assemble with the base saddle. By selecting different sizes of base saddles and counterweights, it can be adapted to ring tracks of different diameters (within the ultra-large diameter range) and different structures, and can quickly respond to the on-site installation needs of different projects. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0024] Figure 2 This is a side view of the present invention;

[0025] Figure 3 This is a side view schematic diagram of the present invention along the direction of the vibration robot;

[0026] Figure 4 A cross-sectional view showing the connection between the base saddle and the track;

[0027] Reference numerals: 1. Welding robot; 101. Laser profile detector; 102. Laser-TIG welding composite torch; 2. Vibration robot; 201. Electromagnetic vibrator; 3. Track; 301. First segment; 302. Second segment; 303. U-shaped bevel; 4. Base saddle; 401. Fixing plate; 402. Clamping plate; 5. Counterweight; 6. Concrete base; 7. Mounting base; 8. Counterweight fastening screw; 9. Clamping screw; 10. Positioning pin; 11. Base fastening screw; 12. Connecting plate. Detailed Implementation

[0028] The technical solution of this utility model will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of this utility model should be understood as prior art known or should be known by those skilled in the art, such as the specific structure of welding robots, vibration robots and electromagnetic vibrators connected thereto, laser-TIG welding composite welding guns, laser contour detectors, etc.

[0029] like Figure 1 , 2 As shown, this utility model discloses a welding device for ultra-large diameter precision circular tracks. The circular track 3 is composed of multiple segmented track 3 spliced ​​together. For ease of description, it will be referred to as... Figure 1 The two adjacent track segments 3 are defined as the first segment 301 and the second segment 302. The first segment 301 and the second segment 302 are both fixed on the concrete base 6. The joint of the first segment 301 and the second segment 302 has an upward-opening U-shaped bevel 303. In order to facilitate welding, the joints of the segments of the ultra-large diameter precision ring track form a straight track. The curved parts of the track are integrally formed. This is the prior art.

[0030] The welding apparatus includes a welding robot 1 and a vibration robot 2, both of which are lightweight four-axis robots. Welding robot 1 is equipped with a laser-TIG welding composite torch and a laser profile detector 101, and also integrates a high-precision vision sensor. Vibration robot 2 is connected to a high-frequency electromagnetic vibrator 201. This vibrator weighs only 1.5-2 kg, is compact, and can output an adjustable frequency of 25-60 Hz with an amplitude range of 0.08-0.3 mm. Vibration parameters can be flexibly adjusted according to the actual weld conditions. It should be noted that the structures of welding robot 1 and vibration robot 2 are existing technologies, and the integration of the laser-TIG welding composite torch, laser profile detector 101, high-precision vision sensor, and high-frequency electromagnetic vibrator 201 onto the respective robots also adopts existing installation methods, which will not be elaborated further here.

[0031] Both welding robot 1 and vibration robot 2 are equipped with a base saddle 4 at their bottom. The base saddle 4 is a U-shaped frame, with the opening of the U-shaped groove facing away from the connected welding robot 1 or vibration robot 2, and the bottom and sidewalls of the U-shaped groove are perpendicular to each other. Clamping screws 9 and counterweights 5 are provided on opposite sides of the base saddle 4.

[0032] Specifically, such as Figure 3 , 4 As shown, the base saddle 4 includes two parallel and spaced clamping plates 402 and a fixing plate 401 connected between the two clamping plates 402. Both the fixing plate 401 and the clamping plates 402 are rectangular plates. The clamping plates 402 and the fixing plate 401 are either an integral structure or separate structures that are fixedly connected. When the clamping plates 402 and the fixing plate 401 are an integral structure, the base saddle 4 is manufactured by casting. When the clamping plates 402 and the fixing plate 401 are separate structures that are fixedly connected, they are fixedly connected by welding.

[0033] Both the welding robot 1 and the vibration robot 2 have mounting bases 7 at their bottoms. The mounting bases 7 have a first positioning hole, and the fixing plate 401 has a second positioning hole corresponding to the first positioning hole. The base fastening screws 11 can pass through the first and second positioning holes to securely connect the mounting base 7 and the base saddle 4. The first positioning hole is a T-shaped open hole, and the second positioning hole is a threaded hole. The base fastening screws 11 can pass through the first positioning hole and be threaded into the second positioning hole.

[0034] The mounting base 7 has a first positioning pin hole, and the fixing plate 401 has a second positioning pin hole corresponding to the first positioning pin hole. The positioning pin 10 can pass through the first positioning pin hole and the second positioning pin hole to limit the relative position of the mounting base 7 and the base saddle 4.

[0035] The base fastening screws 11 and the positioning pins 10 are arranged opposite to each other and are connected and fixed by the base fastening screws 11 and the positioning pins 10 to ensure that the two are accurately positioned and firmly connected. Moreover, compared with all the base fastening screws 11, the arrangement of the base fastening screws 11 and the positioning pins 10 is easier to disassemble and install.

[0036] Each clamping plate 402 has multiple clamping holes, and the clamping screws 9 can pass through the clamping holes and abut against the side wall of the track 3. The clamping screws 9 are spigot screws.

[0037] The counterweight 5 is fixed to the connecting plate 12, which is connected to the side of the base saddle 4. The connecting plate 12 is connected to the clamping plate 402 at a lower position and located on the outside of the clamping plate 402. The connecting plate 12 and the clamping plate 402 are detachably fixed together by counterweight fastening screws 8. Both the connecting plate 12 and the clamping plate 402 have mounting holes for the counterweight screws to pass through. The mounting holes on the clamping plate 402 are through holes, while the mounting holes on the connecting plate 12 can be either blind holes or through holes. It is necessary to ensure that the mounting holes on the connecting plate 12 are threaded holes. In this utility model, the mounting holes on the clamping plate 402 are blind holes, and the counterweight fastening screws 8 pass through the connecting plate 12 and are threaded onto the clamping plate 402 to balance the center of gravity of the robot during operation and improve the safety of equipment operation.

[0038] In other embodiments of this utility model, the mounting hole on the connecting plate 12 is a through hole. The counterweight fastening screw 8 passes through the connecting plate 12 and is threaded onto the clamping plate 402. After passing through the clamping plate 402, it abuts against the side wall of the track 3. The counterweight fastening screw 8 fixes the configuration block on the clamping plate 402 on one hand, and further fixes the base saddle 4 on the track 3 by abutting against the side wall of the track 3 on the other hand, thereby enhancing the stability of the device.

[0039] For ease of understanding, the welding process of this utility model is briefly described as follows:

[0040] I. Operation process of welding robot 1

[0041] The end effector of welding robot 1 integrates a laser-TIG welding hybrid torch and is equipped with a high-precision vision sensor and a laser contour detector 101. Before formal welding, it performs a three-dimensional contour scan of the weld seam using a pre-calibrated positioning reference. The system compares the scanned data with the preset weld seam digital model in real time, automatically calculates the positional deviation, and drives the end effector to perform six-degree-of-freedom fine adjustments to ensure that the laser focus and the arc center are precisely aligned with the weld seam bevel, and that the distance between the laser focus and the bottom of the bevel meets the process requirements (error controlled within ±0.1mm), thus completing the weld seam alignment.

[0042] The welding wire used in welding must be selected based on the material and performance requirements of the base metal to ensure compatibility between the welding wire and the base metal, thereby ensuring that the strength, toughness, and other mechanical properties of the welded joint meet the design standards. For example, if the base metal is low-alloy high-strength steel, a welding wire of the corresponding strength grade can be selected.

[0043] After alignment, welding robot 1 begins operation according to a pre-programmed multi-layer, multi-pass welding procedure. The program includes trajectory planning for each weld pass, including parameters such as the oscillation amplitude and dwell time of the crescent-shaped wire feeding method, and the timing of the coordinated actions of the laser and arc. During welding, the laser preheats the base material to form a molten pool, while the TIG arc fills the welding wire using a crescent-shaped feeding method. The welding wire moves evenly along an arc-shaped trajectory within the weld bevel, ensuring sufficient filling of the molten pool and effectively avoiding defects such as undercut and lack of fusion. The coordinated energy of the laser and arc achieves efficient and high-quality welding. After each weld pass is completed, a visual inspection is performed to check for defects such as undercut, lack of fusion, porosity, and cracks on the weld surface. For critical welds, subsequent non-destructive testing, such as radiographic testing and ultrasonic testing, is also required to ensure the internal quality of the weld is up to standard.

[0044] After inspection, the robotic arm of welding robot 1 will automatically raise to avoid obstacles in the work area and enter standby mode, while simultaneously sending a signal to vibration robot 2. If robot malfunctions or welding defects occur during welding, work should be stopped immediately. For robot malfunctions, professional personnel must be dispatched for repair; work can only continue after the malfunction has been resolved. For welding defects, appropriate repair measures should be taken according to the type and severity of the defect, such as weld repair or grinding. Subsequent operations can only proceed after the defect has passed inspection.

[0045] After the vibration robot 2 completes the vibration treatment of the current weld (eliminating residual stress through vibration at a specific frequency and amplitude) and sends back a completion signal, the robotic arm of the welding robot 1 descends back to the welding start position, confirms the weld position again through the vision system (to compensate for the slight displacement that may be caused by vibration), and then performs the welding operation of the next weld. This cycle continues until all preset welds are completed.

[0046] II. Working Process of Vibration Robot 2

[0047] The end effector of the vibration robot 2 is connected to the high-frequency electromagnetic vibrator 201. This vibrator weighs only 1.5-2kg, is compact, and can output an adjustable frequency of 25-60Hz with an amplitude range of 0.08-0.3mm. Vibration parameters can be flexibly adjusted according to the actual weld conditions. Upon receiving the work signal from the welding robot 1, the vibration robot 2 immediately starts its work program. Its onboard vision positioning system first scans and confirms the current weld position, ensuring that the deviation between the vibrator's point of action and the weld center does not exceed ±0.5mm.

[0048] Subsequently, the robotic arm of vibration robot 2 drives the vibrator to slowly descend, ensuring that the contact end of the vibrator (made of a wear-resistant polymer material to avoid damaging the weld surface) is in close contact with the weld area, maintaining a contact pressure within the range of 30-60N. After confirming a stable fit, the vibrator begins operation according to preset parameters, applying high-frequency vibration to the weld area for a duration of 8-25 seconds (dynamically adjusted according to the weld thickness). During vibration, the posture sensor of vibration robot 2 monitors the stability of the robotic arm in real time, ensuring that the vibration energy is concentrated on the weld and heat-affected zone, maximizing the release of residual stress.

[0049] After vibration treatment is completed, the vibrator automatically stops working, and the robotic arm of vibration robot 2 lifts the vibrator and removes it from the work area, simultaneously sending a completion signal to welding robot 1. Afterward, vibration robot 2 remains in a standby state, waiting for welding robot 1 to complete the next weld and send a new work signal, then repeating the above process to achieve efficient collaborative work with welding robot 1. If equipment malfunctions or other problems occur during vibration, work must be stopped immediately, and professional personnel must be dispatched to inspect and troubleshoot before resuming work.

[0050] III. Post-weld treatment:

[0051] (a) Post-weld heat treatment of welds

[0052] After the entire weld is completed, it needs to undergo localized heat treatment to remove hydrogen. Specifically, heating tape and heat lamps are used as the main heating equipment. The heating tape is tightly wrapped around the weld and heat-affected zone, utilizing its ability to evenly heat the weld to provide basic heat. Simultaneously, heat lamps are placed around the weld to irradiate the area from multiple angles, further enhancing the heating effect. Through this combination, the temperature of the weld and heat-affected zone is stably raised to a range of 250-350℃ and maintained at this temperature for 2-4 hours. During the heating process, a dedicated person must use a temperature monitoring instrument to monitor the weld temperature in real time, ensuring that the temperature does not fluctuate within the specified range and preventing excessively high or low temperatures from affecting the treatment effect. This process effectively promotes the diffusion and escape of hydrogen from the weld, preventing hydrogen-induced cracking, and further removes residual internal stress from the welding process, improving the mechanical properties and stability of the weld and ensuring that the weld quality meets long-term service requirements.

[0053] (ii) Machining of welds

[0054] After the local heat treatment to remove hydrogen and the weld to cool to room temperature, the weld is milled using a portable milling machine (a Normaco PML3 portable milling machine from Finland). During operation, the milling parameters of the milling machine are adjusted according to the actual size of the weld and the surface flatness requirements, so that the milling cutter moves smoothly along the length of the weld to remove protrusions, excess material, and oxide scale from the weld surface, ensuring that the surface flatness of the weld meets the preset standard. After milling, an angle grinder with grinding wheels of different grits is used to polish the weld. First, coarse grinding removes the milling marks, and then fine grinding improves the surface finish of the weld, ultimately achieving the surface roughness required by the design.

[0055] (III) Stress relief of welds and heat-affected zones

[0056] After the grinding and polishing process is completed, vibration robot 2 is activated to repeatedly vibrate the weld and its surrounding area. The high-frequency electromagnetic vibrator 201 of vibration robot 2 maintains the same parameter settings as before (frequency 25-60Hz, amplitude 0.08-0.3mm), and its end effector is precisely aligned with the center of the weld and the heat-affected zone via a vision positioning system, with contact pressure controlled at 30-60N. During vibration, the robotic arm moves back and forth along the entire length of the weld according to a preset trajectory, ensuring that the vibration energy is evenly applied to the entire weld area. Each vibration lasts 15-30 seconds, with a total of 3-5 vibrations. After processing, the residual stress in the weld area is detected using a stress detector until the stress value is less than the design specification value, ensuring the structural safety and stability of the weld during long-term use.

[0057] This implementation plan effectively solves key problems such as deformation control and stress relief during the welding process by utilizing the collaborative operation of dual four-axis robots, combined with unique methods such as laser-TIG hybrid welding and mechanical fixation, as well as comprehensive work processes and quality control measures. Furthermore, meticulous consideration of the working environment, material selection, and emergency handling further ensures the stability and reliability of the welding operation. Following this plan, it is expected that welding tasks for components such as ring tracks can be completed efficiently while ensuring that welding quality meets standards, providing solid technical support for the stable operation of related equipment.

[0058] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A welding device for ultra-large diameter precision circular tracks, characterized in that, It includes a welding robot (1) and a vibration robot (2), and both the welding robot (1) and the vibration robot (2) are equipped with a base saddle (4) at the bottom; The base saddle (4) is a U-shaped frame. The opening direction of the U-shaped groove of the U-shaped frame is opposite to the welding robot (1) or vibration robot (2) connected to it. Clamping screws (9) and counterweights (5) are provided on both sides of the base saddle (4). The base saddle (4) includes two clamping plates (402) arranged in parallel and spaced apart, and a fixing plate (401) connected between the two clamping plates (402); the bottom of both the welding robot (1) and the vibration robot (2) is provided with a mounting base (7), the mounting base (7) is provided with a first positioning hole, and the fixing plate (401) is provided with a second positioning hole corresponding to the first positioning hole. The base fastening screw (11) can pass through the first positioning hole and the second positioning hole to fix the mounting base (7) and the base saddle (4); the mounting base (7) is provided with a first positioning pin hole, and the fixing plate (401) is provided with a second positioning pin hole corresponding to the first positioning pin hole. The positioning pin (10) can pass through the first positioning pin (10) hole and the second positioning pin (10) hole to limit the relative position of the mounting base (7) and the base saddle (4).

2. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The bottom and sidewall of the U-shaped groove of the base saddle (4) are perpendicular to each other.

3. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The base fastening screws (11) and the positioning pins (10) are arranged opposite to each other.

4. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The clamping plate (402) and the fixing plate (401) are an integral structure, or the clamping plate (402) and the fixing plate (401) are separate structures and are fixedly connected.

5. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The counterweight (5) is fixed on the connecting plate (12), and the connecting plate (12) is connected to the side of the base saddle (4).

6. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The base saddle (4) is used to be installed on the rail (3) to be welded. The clamping plate (402) has clamping holes, and the clamping screw (9) can pass through the clamping holes and abut against the side wall of the rail (3).

7. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The first positioning hole is a T-shaped open hole, and the second positioning hole is a cylindrical threaded hole.

8. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, The welding robot (1) is equipped with a laser-TIG welding composite welding gun (102) and a laser profile detector (101).

9. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, An electromagnetic vibrator (201) is installed on the vibration robot (2).

10. The welding device for ultra-large diameter precision circular tracks according to claim 1, characterized in that, Both the welding robot (1) and the vibration robot (2) are four-axis robots.

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