A robotic tightening system and method of float compensation thereof

Abstract

The application provides a robot tightening system and a floating compensation device and method thereof, wherein the floating compensation device comprises a fixed platform, a floating platform and a centering mechanism; the fixed platform comprises a mounting plate and a double-shaft sliding table air cylinder, and the mounting plate is connected with the tail end of the robot; the floating platform comprises two support frames, two support seats, a cross slider mechanism and a connecting block, the cross slider mechanism comprises a cross slider, first and second mutually perpendicular sliding rails, and the cross slider is slidingly installed at the intersection of the second sliding rail and the first sliding rail; the connecting block is connected with the cross slider; and the centering mechanism comprises four centering units. The thrust force applied by the double-shaft sliding table air cylinder offsets the gravity of the floating platform and the tightening shaft, realizes gravity balance, and can be suitable for multi-attitude tightening under horizontal, vertical and inclined angles; the cross slider is adaptively adjusted in position along the first and second sliding rails, the floating range is wide, the cost is low, the compensation is purely mechanical, the control is simple, and the high-beat production can be adapted.

Description

Technical Field

[0001] This invention relates to the field of robotic automated assembly technology, and in particular to a robotic tightening system and its floating compensation device and method. Background Technology

[0002] With the rapid popularization of new energy vehicles, integrated die casting technology has been widely introduced into the manufacturing of large structural components such as the front engine compartment and rear floor. This technology significantly reduces the number of parts and improves weight reduction by integrating hundreds of stamped sheet metal parts from a traditional body-in-white into a single die casting. However, the large size and complex structure of integrated die castings, along with issues such as mold wear and thermal deformation, lead to a significant increase in deviations in the threaded hole positions on the casting. In the automotive manufacturing field, automated bolt installation using robotic tightening systems is widely used in body assembly. Due to the combined effects of fixture positioning errors, robot accuracy errors, and hole position deviations in integrated die castings, tightening failures or insufficient tightening accuracy often occur because the theoretical tightening position deviates too much from the actual hole position.

[0003] Existing technologies often employ a floating sleeve structure located at the end of the tightening shaft to accommodate hole position deviations. However, its floating range is limited and it is only suitable for specific horizontal or vertical tightening conditions. Under multi-position tightening tasks, its floating compensation range is significantly reduced due to gravity, making it difficult to meet the assembly requirements of complex-shaped workpieces with large deviation ranges, such as the front engine compartment and rear floor of automobiles. Regarding active compensation technology, vision guidance or force feedback control, using devices such as binocular cameras and six-dimensional force sensors, can achieve wide-range, high-precision compensation. However, it suffers from high cost and complex control, making it difficult to adapt to the high-cycle demands of production lines. Summary of the Invention

[0004] In view of this, the present invention proposes a floating compensation device for a robot tightening system to solve the technical problems mentioned in the background art, such as insufficient floating range, poor multi-posture adaptability, high cost and complex control of active compensation technology, which makes it difficult to adapt to the high-cycle demand of production lines.

[0005] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a floating compensation device for a robotic tightening system, comprising a fixed platform, a floating platform, and a centering mechanism, wherein: The fixed platform includes a mounting plate and a dual-axis slide cylinder. The mounting plate is connected to the end effector of the robot. The dual-axis slide cylinder is a double-acting cylinder and there are four sets of it. The four sets of dual-axis slide cylinders are located on the four sides of a rectangle centered on the center of the mounting plate. The floating platform includes two support frames, two support seats, a cross slider mechanism, and a connecting block. The two support frames are respectively mounted on two sets of dual-axis slide cylinders, and the two support seats are respectively mounted on the other two sets of dual-axis slide cylinders. The cross slider mechanism includes a cross slider, a first slide rail, and a second slide rail that are perpendicular to each other. The two ends of the first slide rail are respectively connected to the two support frames, and the two ends of the second slide rail are respectively connected to the two support seats. The cross slider is slidably mounted at the intersection of the second slide rail and the first slide rail. The connecting block is connected to the cross slider and is used to connect a tightening shaft. The centering mechanism includes four centering units, which are arranged in a rectangle with the center of the mounting plate as the center. The centering units are used to limit the movement with the support frame or the support seat to achieve locking and unlocking of the floating platform.

[0006] Based on the above technical solutions, preferably, the dual-axis slide cylinder includes a dual-axis cylinder body, a slide, and two first piston rods. The dual-axis cylinder body is mounted on the mounting plate, and the two first piston rods are mounted in the dual-axis cylinder body and connected to the slide. The slide is slidably mounted on the top surface of the dual-axis cylinder body and connected to the support frame or the support base.

[0007] Based on the above technical solutions, preferably, the centering unit includes a mounting base, two needle cylinders and two positioning blocks. The mounting base is fixed on the mounting plate and located inside the dual-axis slide cylinder. The two needle cylinders are mounted on the mounting base. The output end of each needle cylinder is connected to a positioning block. The positioning block is used to insert into the support frame or the support base.

[0008] Based on the above technical solutions, preferably, the support frame is provided with a first positioning hole, the support base is provided with a second positioning hole, and the end of the positioning block is provided with a conical insertion part, which is inserted into the first positioning hole or the second positioning hole.

[0009] Based on the above technical solutions, preferably, the needle cylinder includes a needle cylinder body and a second piston rod, the needle cylinder body is mounted on the mounting base, and the second piston rod is mounted in the needle cylinder body and connected to the positioning block.

[0010] Based on the above technical solutions, preferably, a pneumatic control component is also included. The pneumatic control component includes a main air passage, and two first branch air passages and one second branch air passage respectively connected to the main air passage. One end of the main air passage is connected to an air source, and the other end is connected to an overflow valve. Four sets of dual-axis slide cylinders are provided, two of which are connected to one of the first branch air passages, and the other two are connected to the other first branch air passage, so as to achieve the gravity balance of the floating platform. The second branch air passage is used to control the extension and retraction of the needle cylinder, so as to achieve the locking and unlocking of the floating platform.

[0011] Based on the above technical solutions, preferably, the first branch air circuit includes an electro-proportional valve, a three-position five-way directional valve, two one-way throttle valves, and a differential pressure gauge; the inlet of the electro-proportional valve is connected to the main air circuit, and the outlet is connected to the P port of the three-position five-way directional valve; the three-position five-way directional valve adopts a center-leaking type; the inlets of the two one-way throttle valves are respectively connected to the A and B ports of the three-position five-way directional valve, and the outlets of the two one-way throttle valves are respectively connected to the inlet and outlet of the dual-axis slide cylinder; the differential pressure gauge is connected in parallel between the inlet and outlet of the dual-axis slide cylinder.

[0012] Based on the above technical solutions, preferably, the second branch air circuit includes a pressure reducing valve, a two-position three-way directional valve, and a pressure gauge; the inlet of the pressure reducing valve is connected to the main air circuit, and the outlet is connected to the P port of the two-position three-way directional valve; the A port of the two-position three-way directional valve is connected to the inlet of the needle cylinder; and the pressure gauge is connected to the air inlet of the needle cylinder.

[0013] In a second aspect, the present invention provides a floating compensation method for a robot tightening system, using the floating compensation device for a robot tightening system as described in the first aspect, comprising: The floating platform is locked by limiting the support frame or support base through the centering mechanism; The floating compensation device was moved by the robot to above the theoretical tightening position; By adjusting the intake pressure of the dual-axis slide cylinder, the thrust applied by the dual-axis slide cylinder counteracts the gravity of the floating platform and the tightening shaft. The floating platform is released from its lock by disengaging from the support frame or support base through the centering mechanism. The floating compensation device and the tightening shaft are moved by the robot to the theoretical tightening position, and the tightening shaft is driven to tighten the bolt. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider adaptively adjusts its position along the first and second slide rails under the action of pneumatic compliance.

[0014] Thirdly, the present invention provides a robot tightening system, including a robot and a tightening shaft, and a floating compensation device for the robot tightening system as described in the first aspect, wherein the end of the robot is connected to the mounting plate and the tightening shaft is connected to the connecting block.

[0015] The floating compensation device for the robot tightening system of the present invention has the following advantages over the prior art: (1) The floating platform is locked by limiting the support frame or support seat through the centering mechanism. By adjusting the air intake pressure of the dual-axis slide cylinder, the thrust applied by the dual-axis slide cylinder counteracts the gravity of the floating platform and the tightening shaft. The floating platform is released from the limit of the support frame or support seat by the centering mechanism. The floating compensation device and the tightening shaft are moved to the theoretical tightening position by the robot, and the tightening shaft is driven to tighten the bolt. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider is adaptively adjusted along the first slide rail and the second slide rail under the pneumatic compliance action. The floating range of this device is wide, and it can achieve gravity balance. It can be used for multi-posture tightening in horizontal, vertical and inclined angles. It has low cost, is purely mechanical floating compensation, is simple to control, and can adapt to the high cycle time of the production line. (2) The dual-axis cylinder is mounted on the mounting plate, the slide is slidably mounted on the top surface of the dual-axis cylinder and connected to the support frame or the support seat, the two first piston rods are mounted in the dual-axis cylinder and connected to the slide, the air intake pressure of the dual-axis slide cylinder makes the thrust of the piston rods able to balance the weight of the floating platform and the tightening shaft, so that the slides at both ends of the first slide rail and the slides at both ends of the second slide rail can slide easily. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the position can be adjusted adaptively with high adjustment accuracy. (3) Two needle cylinders are installed on the mounting base. The output end of each needle cylinder is connected to a positioning block. The needle cylinder extends so that the positioning block can be inserted into the support frame or the support base to lock the floating platform. When unlocking is required, the needle cylinder drives the positioning block to retract. (4) Four sets of dual-axis slide cylinders are used, two of which are connected to one of the first branch air circuits and the other two are connected to another of the first branch air circuits to achieve gravity balance of the floating platform; the second branch air circuit is used to control the extension and retraction of the needle cylinder to achieve locking and unlocking of the floating platform. The action of the dual-axis slide cylinder and the needle cylinder is realized by pneumatic control, thereby realizing the overall control of the device. The response is fast, which can improve the tightening efficiency of the robot tightening bolts. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the floating compensation device for the robot tightening system in an embodiment of the present invention; Figure 2 This is an exploded view of the floating compensation device for the robot tightening system in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the fixed platform in an embodiment of the present invention; Figure 4 This is a schematic diagram of the mounting plate in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the floating platform in an embodiment of the present invention; Figure 6 This is a schematic diagram of the cross slider mechanism in an embodiment of the present invention; Figure 7 This is a schematic diagram of the support frame in an embodiment of the present invention; Figure 8 This is a schematic diagram of the centering mechanism in an embodiment of the present invention; Figure 9 This is a schematic diagram of the centering unit in an embodiment of the present invention; Figure 10 This is a schematic diagram of the floating compensation device (with a housing) used in the robot tightening system according to an embodiment of the present invention; Figure 11 This is a schematic diagram of the installation of the floating compensation device and the tightening shaft in the robot tightening system according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the pneumatic control principle of the pneumatic control component in an embodiment of the present invention; Figure 13 This is a schematic diagram of the robot tightening system in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached drawings: 1-Fixed platform, 2-Floating platform, 3-Return mechanism, 4-Pneumatic control components, 5-Outer shell; 100 - Robot, 200 - Tightening shaft, 300 - Connecting flange, 400 - Connecting plate; 11-Mounting plate, 111-Mounting groove, 12-Dual-axis slide cylinder, 121-Dual-axis cylinder body, 122-Slide, 123-First piston rod; 21-Support frame, 211-Base plate, 2111-First positioning hole, 212-Top plate, 2121-First slotted hole, 213-Side plate, 2131-Third slotted hole, 22-Support base, 221-Second slotted hole, 222-Second positioning hole, 23-Cross slider mechanism, 231-Cross slider, 232-First slide rail, 233-Second slide rail, 24-Connecting block; 31-Centering unit, 311-Mounting base, 312-Needle cylinder, 3121-Needle cylinder body, 3122-Second piston rod, 313-Positioning block, 3131-Plug-in part; 41-Main air circuit, 411-Air source, 412-Relief valve, 413-Triple unit; 42-First branch air circuit, 421-Electro-proportional valve, 422-Three-position five-way directional valve, 423-One-way throttle valve, 424-Differential pressure gauge, 425-Silencer; 43-Second branch air circuit, 431-Pressure reducing valve, 432-Two-position three-way directional valve, 433-Pressure gauge, 434-Diverter; 51- Reserved opening for air pipe. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Reference Figures 1-12 As shown, a first aspect of the present invention provides a floating compensation device for a robot tightening system, comprising a fixed platform 1, a floating platform 2, and a centering mechanism 3, wherein: The fixed platform 1 includes a mounting plate 11 and dual-axis slide cylinders 12. The mounting plate 11 is connected to the end of the robot 100. The dual-axis slide cylinders 12 are double-acting cylinders and there are four sets. The four sets of dual-axis slide cylinders 12 are located on the four sides of a rectangle centered on the center of the mounting plate 11. Two sets of dual-axis slide cylinders 12 are arranged along the X-axis and are symmetrical about the center of the mounting plate 11. The other two sets of dual-axis slide cylinders 12 are arranged along the Y-axis and are symmetrical about the center of the mounting plate 11. The cylinder diameter of the dual-axis slide cylinder 12 is 16mm and the stroke is 10mm. After installation, the parallelism of the axes of the two symmetrical dual-axis slide cylinders 12 must be ensured to avoid cylinder jamming during operation. The floating platform 2 includes two support frames 21, two support seats 22, a cross slider mechanism 23, and a connecting block 24. The two support frames 21 are respectively mounted on two sets of dual-axis slide cylinders 12, and the two support seats 22 are respectively mounted on the other two sets of dual-axis slide cylinders 12. The cross slider mechanism 23 includes a cross slider 231, a first slide rail 232 and a second slide rail 233 that are perpendicular to each other. The two ends of the first slide rail 232 are respectively connected to the two support frames 21, and the two ends of the second slide rail 233 are respectively connected to the two support seats 22. The cross slider 231 is slidably mounted at the intersection of the second slide rail 233 and the first slide rail 232. The connecting block 24 is connected to the cross slider 231 and is used to connect a tightening shaft 200. The tightening shaft 200 is equipped with a tightening motor, which drives the tightening shaft 200 to rotate, thus tightening the bolts. The connecting block 24 is mounted on the side of the cross slider 231. The movement of the tightening shaft 200 in the plane can be achieved through the cross slider mechanism. 23 is decomposed into two sets of dual-axis slide cylinders 12 linear motion in the X-axis direction and two sets of dual-axis slide cylinders 12 linear motion in the Y-axis direction. The component of the gravity on the mounting plate 11 plane of the tightening shaft 200 can be transmitted to the two sets of dual-axis slide cylinders 12 in the X-axis direction and the two sets of dual-axis slide cylinders 12 in the Y-axis direction through the cross slider mechanism 23. The installation must ensure the parallelism of the first slide rail 232 and the second slide rail 233 with respect to the side of the mounting plate 11, and the parallelism of the second slide rail 233 with respect to the mounting plate 11. The parallelism of the upper surface of plate 11 is checked. After installation, the movement of the cross slider 231 and the dual-axis slide cylinder 12 is tested for any jamming. If jamming occurs, the installation accuracy of the first slide rail 232 and the second slide rail 233 needs to be adjusted. The allowable static torque of the cross slider 231 is ≥80.5 N·m. The width of the first slide rail 232 and the second slide rail 233 is 15 mm. The first slide rail 232 and the second slide rail 233 are based on the side of the mounting plate 1. After installation, the parallelism error between the first slide rail 232 and the side of the mounting plate 1 is ≤0.1 mm. Specifically, the support frame 21 includes a base plate 211, a top plate 212, and two side plates 213. The base plate 211 is mounted on the dual-axis slide cylinder 12. The top plate 212 and the base plate 211 are arranged in parallel. The side plates 213 are connected to the base plate 211 and the top plate 212 respectively, forming a hollow rectangular frame structure. The two ends of the first slide rail 232 are connected to the top plates 212 of the two support frames 21 respectively, thereby raising the first slide rail 232 so that the first slide rail 232 and the second slide rail 233 are staggered in the height direction. The top plate 212 has a first groove hole 2121 with the length direction parallel to the first slide rail 232. After the bolt passes through the first groove hole 2121 and the first slide rail 232, it is connected to the nut. The locking mechanism is designed to prevent over-positioning of the mechanism from causing excessive radial force on the dual-axis slide cylinder 12 and resulting in cylinder jamming. The support base 22 has a second slot 221 with its length direction parallel to the second slide rail 233. Bolts pass through the second slot 221 and the second slide rail 233 and are locked with nuts. The second slot 221 is designed to prevent over-positioning of the mechanism from causing excessive radial force on the dual-axis slide cylinder 12 and resulting in cylinder jamming. The side plate 213 has a third slot 2131 with its length direction along the height direction of the side plate. Bolts pass through the third slot 2131 and connect to the top plate 212. The third slot 2131 is used for fine adjustment of the parallelism of the first slide rail 232 relative to the second slide rail 233. The centering mechanism 3 includes four centering units 31, which are arranged in a rectangle around the center of the mounting plate 11. The centering units 31 are used to limit the movement of the support frame 21 or the support base 22, thereby locking and unlocking the floating platform 2. Two centering units 31 are used to limit the movement of the two support frames 21 respectively, and the other two centering units 31 are used to limit the movement of the two support bases 22 respectively.

[0021] The floating compensation device for the robot tightening system proposed in this embodiment uses a centering mechanism 3 to limit the support frame 21 or support base 22, locking the floating platform 2. By adjusting the air intake pressure of the dual-axis slide cylinder 12, the thrust applied by the dual-axis slide cylinder 12 counteracts the gravity of the floating platform 2 and the tightening shaft 200. The centering mechanism 3 releases the limit on the support frame 21 or support base 22, releasing the lock on the floating platform 2. The floating compensation device and the tightening shaft 200 are moved by the robot 100 to the theoretical tightening position, driving the tightening shaft 200 to tighten the bolts. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider 231 adaptively adjusts its position along the first slide rail 232 and the second slide rail 233 under pneumatic compliance. This device has a wide floating range, can achieve gravity balance, and can be used for multi-posture tightening in horizontal, vertical, and tilt angles. It is low-cost, purely mechanical floating compensation, simple to control, and can adapt to the high cycle time of the production line.

[0022] In some embodiments, the dual-axis slide cylinder 12 includes a dual-axis cylinder body 121, a slide 122, and two first piston rods 123. The dual-axis cylinder body 121 is installed in the mounting groove 111 of the mounting plate 11. The mounting groove 111 is rectangular. The two first piston rods 123 are installed in the dual-axis cylinder body 121 and connected to the slide 122. The slide 122 is slidably installed on the top surface of the dual-axis cylinder body 121 and connected to the support frame 21 or the support base 22. The slide 122 is L-shaped. The vertical side of the slide 122 is connected to the first piston rods 123. The horizontal side of the slide 122 is slidably installed on the top surface of the dual-axis cylinder body 121. The bottom end of the vertical side of the slide 122 extends into the mounting groove 111, which can limit the maximum displacement of the slide 122. Two support frames 21 are respectively fixedly installed on the slides 122 of the two sets of dual-axis slide cylinders 12 arranged along the X-axis direction, and two support seats 22 are respectively fixedly installed on the slides 122 of the two sets of dual-axis slide cylinders 12 arranged along the Y-axis direction. The air intake pressure of the dual-axis slide cylinders 12 enables the thrust of the piston rod to balance the weight of the floating platform 2 and the tightening shaft 200, allowing the slides 122 at both ends of the first slide rail 232 and the slides 122 at both ends of the second slide rail 233 to slide easily. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the position can be adaptively adjusted with high adjustment accuracy.

[0023] In some embodiments, the centering unit 31 includes a mounting base 311, two needle cylinders 312, and two positioning blocks 313. The mounting base 311 is fixed to the mounting plate 11 and located inside the dual-axis slide cylinder 12. The two needle cylinders 312 are mounted on the mounting base 311, and the output end of each needle cylinder 312 is connected to a positioning block 313. The positioning block 313 is used to insert into the support frame 21 or the support seat 22. The two positioning blocks 313 of each centering unit 31 are inserted into one support frame 21 or one support seat 22, thereby improving the stability of centering. The mounting base 311 is located inside the dual-axis slide cylinder 12, which makes the structure more compact and the floating compensation device more miniaturized. The needle cylinder 312 extends, allowing the positioning block 313 to engage with the support frame 21 or the support base 22, thus locking the floating platform 2. To unlock, the needle cylinder 312 retracts the positioning block 313. The needle cylinder 312 is a retractable type with a diameter of 10mm and a stroke of 10mm.

[0024] In some embodiments, the support frame 21 is provided with a first positioning hole 2111, and the side of the base plate 211 is provided with two first positioning holes 2111. The first positioning holes 2111 are conical holes and are arranged facing inward. The support base 22 is provided with two second positioning holes 222. The second positioning block 313 is a conical hole and is arranged facing inward. The end of the positioning block 313 is provided with a conical insertion part 3131, and the insertion part 3131 is inserted into the first positioning hole 2111 or the second positioning hole 222. The positioning blocks 313 of two centering units 31 are respectively used to insert into the first positioning holes 2111 of the two support frames 21, and the positioning blocks 313 of the other two centering units 31 are respectively used to insert into the second positioning holes 222 of the two support seats 22. By inserting the insertion part 3131 into the first positioning hole 2111, the two support frames 21 are limited. By inserting the insertion part 3131 into the second positioning hole 222, the two support seats 22 are limited, and the floating platform 2 is locked.

[0025] In some embodiments, the needle cylinder 312 includes a needle cylinder body 3121 and a second piston rod 3122. The needle cylinder body 3121 is mounted on the mounting base 311, and the second piston rod 3122 is mounted in the needle cylinder body 3121 and connected to the positioning block 313. The second piston rod 3122 slides within the needle cylinder body 3121 under pneumatic control, thereby extending and retracting the second piston rod 3122 and moving the positioning block 313. The needle cylinder 312 is a single-acting retractable type; when no high-pressure gas is introduced, the second piston rod 3122 remains retracted; when high-pressure gas is introduced, the second piston rod 3122 extends.

[0026] In some embodiments, the floating compensation device for the robot tightening system further includes a pneumatic control component 4, which includes a main air passage 41, and two first branch air passages 42 and a second branch air passage 43 respectively connected to the main air passage 41; one end of the main air passage 41 is connected to an air source 411, and the other end is connected to an overflow valve 412; four sets of dual-axis slide cylinders 12, two of which are connected to one of the first branch air passages 42, and the other two are connected to another first branch air passage 42, so as to achieve gravity balance of the floating platform 2; the second branch air passage 43 is used to control the extension and retraction of the needle cylinder 312 to achieve locking and unlocking of the floating platform 2. The air source 411 is connected to the triplet 413 before entering the main air circuit 41. The triplet 413 consists of three main components: an air pressure reducing valve, a filter, and an oil mist lubricator. The air pressure reducing valve stabilizes the air source 411, keeping it at a constant pressure and reducing damage to valves or actuators caused by sudden changes in air pressure. The filter cleans the air source 411, filtering out moisture from the compressed air to prevent it from entering the device. The oil mist lubricates the moving parts of the machine, providing lubrication for components where lubrication is inconvenient, significantly extending the machine's service life. The pressure in the main air circuit 41 is set to the maximum system operating pressure by the air pressure reducing valve in the triplet 413, while the overflow valve 412 is set to a safe pressure higher than the system operating pressure. Pneumatic control enables the movement of the dual-axis slide cylinder 12 and the needle cylinder 312, achieving overall control of the device with a fast response, thus improving the tightening efficiency of the robot 100 bolt tightening.

[0027] In some further embodiments, the first branch air passage 42 includes an electro-proportional valve 421, a three-position five-way directional valve 422, two one-way throttle valves 423, and a differential pressure gauge 424; the inlet of the electro-proportional valve 421 is connected to the main air passage 41, and the outlet is connected to the P port of the three-position five-way directional valve 422; the three-position five-way directional valve 422 is a center-venting type; the inlets of the two one-way throttle valves 423 are respectively connected to the A and B ports of the three-position five-way directional valve 422, and the outlets of the two one-way throttle valves 423 are respectively connected to the dual-axis slide cylinder 12. The air inlet and outlet are connected, with one one-way throttle valve 423 outlet connected to the air inlet of each of the two dual-axis slide cylinders 12, and another one-way throttle valve 423 outlet connected to the air outlet of each of the two dual-axis slide cylinders 12. A differential pressure gauge 424 is connected in parallel between the air inlet and outlet of each dual-axis slide cylinder 12, that is, in parallel between the main air supply pipe and the main air return pipe of each of the two sets of dual-axis slide cylinders 12, used to monitor the pressure difference between the air inlet and outlet of the two sets of dual-axis slide cylinders 12 arranged in the X-axis or Y-axis direction. The electro-proportional valve 421 is model ITV1030, with a set pressure range of 0.005-0.5MPa.

[0028] In some embodiments, the second branch air passage 43 includes a pressure reducing valve 431, a two-position three-way reversing valve 432, and a pressure gauge 433; the inlet of the pressure reducing valve 431 is connected to the main air passage 41, and the outlet is connected to the P port of the two-position three-way reversing valve 432; the A port of the two-position three-way reversing valve 432 is connected to the inlet of the needle cylinder 312; and the pressure gauge 433 is connected to the air inlet of the needle cylinder 312. The two-position three-way directional valve 432 is normally closed, meaning that port P is closed when not energized, and port A is open to exhaust through port T. Its working port A is connected to the inlet of eight needle cylinders 312 simultaneously via a distributor 434. The needle cylinders 312 are single-acting spring-return cylinders. The pressure-reducing valve 431 is set to a pressure sufficient to meet the thrust required by the needle cylinders 312. A pressure gauge 433 is connected to the air line after the distributor 434 to monitor the air supply pressure of the needle cylinders 312. A silencer 425 is installed at the exhaust port T of the two-position three-way directional valve 432. The Cv value (flow coefficient of the valve, used to indicate the valve's flow capacity under specific operating conditions) of the two-position three-way directional valve 432 is 1.68.

[0029] All pneumatic components of the above pneumatic control system are integrated and installed in an external pneumatic control cabinet.

[0030] In some embodiments, the floating compensation device further includes a housing 5, which is connected to the mounting plate 11. The housing 5 covers the other parts of the floating compensation device, forming a protective layer. Air pipes are introduced into the device through pre-drilled air pipe openings 51 on the housing 5, and connected to the interfaces of two sets of dual-axis slide cylinders 12 arranged in the X-axis direction, two sets of dual-axis slide cylinders 12 arranged in the Y-axis direction, and eight needle cylinders 312, respectively. The gauges of the differential pressure gauge 424 and pressure gauge 433 can be mounted on the pneumatic control cabinet panel. The control signal lines of the electro-proportional valve 421, the three-position five-way directional valve 422, and the two-position three-way directional valve 432 are connected to the PLC control system inside the pneumatic control cabinet.

[0031] The operation of the floating compensation device is controlled by the Robot 100 control system or a dedicated PLC, and the specific steps are as follows: Step S1, centering and initial positioning: The controller sends an energizing signal to the two-position three-way directional valve 432, which opens the valve port. Compressed air enters the eight needle cylinders 312 through the pressure reducing valve 431, the two-position three-way directional valve 432, and the distributor 434. The second piston rod 3122 is pushed out, which drives the positioning block 313 at its end to insert into the first positioning hole 2111 or the second positioning hole 222, locking the floating platform 2 in the center position of the device.

[0032] The robot 100 drives the entire floating compensation device and the tightening shaft 200 mounted on it to a safe height above the theoretical tightening position via the connecting flange 300.

[0033] Step S2, Gravity balance: The controller obtains the component of the gravity of the floating platform 2 on the plane of the mounting plate 11 based on the target's tightening bolt posture. This component can be decomposed into an X-axis component Fx and a Y-axis component Fy, which can be determined in advance.

[0034] Based on the direction and magnitude of Fx and Fy, set: For one of the three-position five-way directional valves 422, if the thrust of the dual-axis slide cylinder 12 needs to be balanced in the Fx direction, the valve position is set to supply air in the corresponding direction. For example, if Fx is to the left, the valve position is set so that the high pressure output from port A drives the dual-axis slide cylinder 12 to generate a force to the right. If Fx is 0, such as pure vertical tightening, the valve position is set to the neutral position to release pressure. Similarly, the other three-position five-way directional valve 422 sets its valve position according to the Fy direction.

[0035] The controller sends a set pressure command to the two electro-proportional valves 421. The set pressure value is calculated based on the magnitudes of Fx and Fy and the effective area of ​​the cylinder. The electro-proportional valves 421 continuously adjust the output air pressure according to the electrical signal. The differential pressure gauge 424 is used to assist in monitoring and calibrating whether the actual pressure difference has reached the target value.

[0036] Step S3, unlock the float: After confirming that the pressure of the dual-axis slide cylinder 12 has been established and reached a balanced state, the controller sends a power-off signal to the two-position three-way reversing valve 432, the valve port closes, the air intake of the needle cylinder 312 is exhausted, the second piston rod 3122 retracts under the action of the internal spring, the positioning block 313 disengages from the first positioning hole 2111 or the second positioning hole 222, and the floating platform 2 is released from locking. At this time, the floating platform 2 is in a suspended state, and its gravity has been balanced by the air pressure of the dual-axis slide cylinder 12.

[0037] Step S4, Floating compensation and bolt tightening: The robot 100 drives the floating compensation device and the tightening shaft 200 to move to the theoretical tightening position at a low and constant speed along a direction perpendicular to the axis of the target threaded hole. Floating compensation process: If there is a deviation between the actual position and the theoretical position of the threaded hole, the bolt will be subjected to a lateral force when it contacts the hole opening. This force is transmitted to the cross slider 231 through the tightening shaft 200, the tightening shaft 200 mounting plate 11, and the support block. Under pneumatic compliance: The cross slider 231 drives the floating platform 2 to produce a small sliding displacement along slide rail I and / or slide rail II; The piston rod of the corresponding dual-axis slide cylinder 12 extends and retracts along with the movement of the cross slide block 231 under the flexible support of the pneumatic chamber, thereby passively absorbing positional deviations. This ensures that the bolt axis can adaptively align with the threaded hole axis. The tightening shaft 200 uses a torque / angle sensor to determine whether the bolt has been inserted into the hole, and completes the bolt tightening operation according to a preset tightening strategy, such as torque control, angle control, or yield point control.

[0038] Step S5, Reset: After the bolts are tightened, the control robot 100 removes the sleeve from the bolt head, the controller sends an energizing signal to the two-position three-way reversing valve 432, the needle cylinder 312 pushes the positioning block 313 to re-insert into the conical hole, and locks the floating platform 2 back to the center position. The controller sends a signal to the two three-position five-way directional valves 422 to switch them to the middle position depressurization state. The gas inside the dual-axis slide cylinder 12 is discharged through the three-position five-way directional valve 422 and the silencer 425, and the cylinder is reset. Robot 100 will raise the floating compensation device to a safe height or move it to the next theoretical tightening position.

[0039] Repeat steps S2 to S5 to tighten the bolts.

[0040] Based on the same concept, a second aspect of the present invention provides a floating compensation method for a robot tightening system, using the floating compensation device for a robot tightening system as described in the first aspect embodiment, including: The floating platform 2 is locked by limiting the support frame 21 or support base 22 through the centering mechanism 3; The floating compensation device is moved by robot 100 to above the theoretical tightening position; By adjusting the intake pressure of the dual-axis slide cylinder 12, the thrust applied by the dual-axis slide cylinder 12 counteracts the gravity of the floating platform 2 and the tightening shaft 200. The floating platform 2 is released from its lock by disengaging from the centering mechanism 3, which releases the limit on the support frame 21 or support base 22. The floating compensation device and the tightening shaft 200 are moved to the theoretical tightening position by the robot 100, and the tightening shaft 200 is driven to tighten the bolt. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider 231 adaptively adjusts its position along the first slide rail 232 and the second slide rail 233 under the action of pneumatic compliance.

[0041] The robot tightening system proposed in this embodiment uses a floating compensation method. By adjusting the air intake pressure of the dual-axis slide cylinder 12, the thrust applied by the dual-axis slide cylinder 12 counteracts the gravity of the floating platform 2 and the tightening shaft 200, achieving gravity balance. It can be used for multi-posture tightening in horizontal, vertical, and tilt angles. By releasing the limit on the support frame 21 or support seat 22 through the centering mechanism 3, the floating platform 2 is unlocked. The floating compensation device and the tightening shaft 200 are moved to the theoretical tightening position by the robot 100, driving the tightening shaft 200 to tighten the bolt. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider 231 adaptively adjusts its position along the first slide rail 232 and the second slide rail 233 under the action of pneumatic compliance. This device has a wide floating range, low cost, and is a purely mechanical floating compensation. It is simple to control and can adapt to the high cycle time of the production line.

[0042] Based on the same concept, a third aspect of the present invention is described, with reference to... Figure 13 As shown, a robotic tightening system is provided, including a robot 100 and a tightening shaft 200, as well as a floating compensation device for the robotic tightening system as described in the first aspect embodiment. The end of the robot 100 is connected to the mounting plate 11, and the tightening shaft 200 is connected to the connecting block 24. The end of the robot 100 is connected to the mounting plate 11 via a connecting flange 300, and the tightening shaft 200 is connected to the connecting block 24 via a connecting plate 400.

[0043] The robot tightening system proposed in this embodiment can be used for tightening in multiple postures, including horizontal, vertical and inclined angles. It has a wide floating range, low cost, pure mechanical floating compensation, simple control, and can adapt to the high cycle time of the production line.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A floating compensation device for a robot tightening system, characterized in that, It includes a fixed platform, a floating platform, and a centering mechanism, among which: The fixed platform includes a mounting plate and a dual-axis slide cylinder. The mounting plate is connected to the end effector of the robot. The dual-axis slide cylinder is a double-acting cylinder and there are four sets of it. The four sets of dual-axis slide cylinders are located on the four sides of a rectangle centered on the center of the mounting plate. The floating platform includes two support frames, two support seats, a cross slider mechanism, and a connecting block. The two support frames are respectively mounted on two sets of dual-axis slide cylinders, and the two support seats are respectively mounted on the other two sets of dual-axis slide cylinders. The cross slider mechanism includes a cross slider, a first slide rail, and a second slide rail that are perpendicular to each other. The two ends of the first slide rail are respectively connected to the two support frames, and the two ends of the second slide rail are respectively connected to the two support seats. The cross slider is slidably mounted at the intersection of the second slide rail and the first slide rail. The connecting block is connected to the cross slider and is used to connect a tightening shaft. The centering mechanism includes four centering units, which are arranged in a rectangle with the center of the mounting plate as the center. The centering units are used to limit the movement with the support frame or the support seat to achieve locking and unlocking of the floating platform.

2. The floating compensation device for the robot tightening system as described in claim 1, characterized in that, The dual-axis slide cylinder includes a dual-axis cylinder body, a slide, and two first piston rods. The dual-axis cylinder body is mounted on the mounting plate, and the two first piston rods are mounted in the dual-axis cylinder body and connected to the slide. The slide is slidably mounted on the top surface of the dual-axis cylinder body and connected to the support frame or the support base.

3. The floating compensation device for the robot tightening system as described in claim 1, characterized in that, The centering unit includes a mounting base, two needle cylinders, and two positioning blocks. The mounting base is fixed to the mounting plate and located inside the dual-axis slide cylinder. The two needle cylinders are mounted on the mounting base. The output end of each needle cylinder is connected to a positioning block. The positioning block is used to insert into the support frame or the support base.

4. The floating compensation device for the robot tightening system as described in claim 3, characterized in that, The support frame is provided with a first positioning hole, the support base is provided with a second positioning hole, and the end of the positioning block is provided with a conical insertion part, which is inserted into the first positioning hole or the second positioning hole.

5. The floating compensation device for the robot tightening system as described in claim 4, characterized in that, The needle cylinder includes a needle cylinder body and a second piston rod. The needle cylinder body is mounted on the mounting base, and the second piston rod is mounted in the needle cylinder body and connected to the positioning block.

6. The floating compensation device for the robot tightening system as described in claim 5, characterized in that, It also includes a pneumatic control assembly, which includes a main air path, and two first branch air paths and one second branch air path respectively connected to the main air path; one end of the main air path is connected to an air source, and the other end is connected to an overflow valve; four sets of dual-axis slide cylinders, two of which are connected to one of the first branch air paths, and the other two are connected to another first branch air path, so as to achieve the gravity balance of the floating platform; the second branch air path is used to control the extension and retraction of the needle cylinder, so as to achieve the locking and unlocking of the floating platform.

7. The floating compensation device for the robot tightening system as described in claim 6, characterized in that, The first branch air circuit includes an electro-proportional valve, a three-position five-way directional valve, two one-way throttle valves, and a differential pressure gauge; the inlet of the electro-proportional valve is connected to the main air circuit, and the outlet is connected to the P port of the three-position five-way directional valve; the three-position five-way directional valve is a center-leaking type; the inlets of the two one-way throttle valves are respectively connected to the A and B ports of the three-position five-way directional valve, and the outlets of the two one-way throttle valves are respectively connected to the inlet and outlet of the dual-axis slide cylinder; the differential pressure gauge is connected in parallel between the inlet and outlet of the dual-axis slide cylinder.

8. The floating compensation device for the robot tightening system as described in claim 6, characterized in that, The second branch air circuit includes a pressure reducing valve, a two-position three-way directional valve, and a pressure gauge; the inlet of the pressure reducing valve is connected to the main air circuit, and the outlet is connected to the P port of the two-position three-way directional valve; the A port of the two-position three-way directional valve is connected to the inlet of the needle cylinder; and the pressure gauge is connected to the air inlet of the needle cylinder.

9. A floating compensation method for a robot tightening system, using the floating compensation device for a robot tightening system as described in any one of claims 1-8, characterized in that, include: The floating platform is locked by limiting the support frame or support base through the centering mechanism; The floating compensation device is moved by the robot to above the theoretical tightening position; By adjusting the intake pressure of the dual-axis slide cylinder, the thrust applied by the dual-axis slide cylinder counteracts the gravity of the floating platform and the tightening shaft. The floating platform is released from its lock by disengaging from the support frame or support base through the centering mechanism. The floating compensation device and the tightening shaft are moved by the robot to the theoretical tightening position, and the tightening shaft is driven to tighten the bolt. When there is a deviation between the actual position of the threaded hole and the theoretical tightening position, the cross slider adaptively adjusts its position along the first and second slide rails under the action of pneumatic compliance.

10. A robotic tightening system, characterized in that, It includes a robot and a tightening shaft, and a floating compensation device for a robot tightening system as described in any one of claims 1-8, wherein the end of the robot is connected to the mounting plate and the tightening shaft is connected to the connecting block.

Images