Flexible gun inserting device for automatic charging robot and current feedback control method

Abstract

This invention discloses a flexible charging gun device and a current feedback control method for an automatic charging robot. The flexible charging gun device includes a flexible connection mechanism, a charging gun, and a current feedback control unit. The current feedback control unit is used to collect robot operating status information and control the robot's robotic arm to adjust the insertion posture of the charging gun accordingly. The flexible connection mechanism includes a first and a second mounting plate arranged opposite to each other. The first mounting plate is used to connect to the end of the robotic arm, and the charging gun is fixed on the outer side of the second mounting plate, which has a guide hole with a limiting mating surface. A guide post with a limiting surface is fixed on the side of the first mounting plate facing the second mounting plate, and the free end of the guide post passes through the guide hole, with the limiting surface fitting against the limiting mating surface. A pre-compressed elastic element is connected between the two mounting plates, so that the second mounting plate remains in a fitted state when there is no external force, can adapt to movement under external force, and automatically resets after the external force disappears. This invention can compensate for the positioning and posture deviation of the charging gun and the charging port in multiple directions.

Description

Technical Field

[0001] This invention relates to the field of automatic charging equipment technology for electric vehicles, and in particular to a flexible charging gun device and current feedback control method for an automatic charging robot. Background Technology

[0002] In the scenario of automatic charging of electric vehicles, when the charging gun of the charging robot docks with the charging port of the vehicle, the rigid connection structure is prone to damage to the charging gun or charging port due to factors such as the deviation of the vehicle's parking position, the positioning error of the robotic arm, and the shaking of the vehicle body. Therefore, a flexible connection mechanism is required to compensate for the position and posture deviation.

[0003] Existing flexible connection mechanisms all have structural defects, as detailed below: Purely passive buffer structures, such as those disclosed in patents CN201620430684 and CN201911384469, rely solely on springs and rubber rods as elastic buffer components. They lack fixed positioning references and mechanical hard-limiting structures, and their reset accuracy depends entirely on the deformation capacity of the elastic components. Over time, aging and fatigue deformation of the elastic components can directly lead to a shift in the charging gun's reset position, affecting the accuracy of the charging gun insertion and even causing insertion malfunctions.

[0004] Multi-degree-of-freedom passive compensation structures, such as those disclosed in patents CN202021729727 and CN202121572376, achieve multi-degree-of-freedom floating compensation through components such as guide rails, hinges, and rolling elements. However, they do not have a fixed reference surface, and the reset still relies on the restoring force of elastic components, which can lead to the problem of aging and failure of elastic components. At the same time, this type of structure lacks a mechanical limit and reset structure, which cannot guarantee that the charging gun will accurately return to its initial posture, and the floating posture is uncontrollable.

[0005] Active detection structures, such as those disclosed in patents CN202510755220 and CN202111296345, require additional electrical detection and execution components such as microswitches, pressure sensors, and electromagnets. This results in a complex overall structure, a large number of parts, difficult assembly, and high production costs. Furthermore, the additional components increase the risk of mechanical failure, which is not conducive to large-scale promotion and application.

[0006] In summary, existing flexible connection mechanisms generally suffer from structural defects such as poor reset accuracy, complex structure, high cost, and lack of mechanical hard limit reference, which cannot meet the needs of charging robots for efficient, stable, and low-cost automatic charging. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a flexible plug-in device and current feedback control method for automatic charging robots, which can compensate for the positioning and posture deviation of the charging gun and the charging port in multiple directions, and hard limit ensures the accuracy of the plugging and unplugging position and the consistency of posture. The pure mechanical structure does not require a six-dimensional force sensor, which significantly reduces the manufacturing cost and facilitates large-scale promotion.

[0008] To address the aforementioned technical problems, the first aspect of this invention discloses a flexible charging gun device for an automatic charging robot, comprising: a flexible connection mechanism, a charging gun, and a current feedback control unit. The current feedback control unit is used to collect robot operating status information and control the robot's robotic arm to adjust the insertion posture of the charging gun accordingly. The flexible connection mechanism includes: The first mounting plate is used for fixed connection to the end of the robot's robotic arm; The second mounting plate is disposed opposite to the first mounting plate. The outer side of the second mounting plate has a mounting surface for connecting the charging gun. The second mounting plate has at least one through guide hole, and a limiting mating surface is provided in the guide hole. At least one guide post is fixedly disposed on the side of the first mounting plate facing the second mounting plate, and the free end of the guide post has a limiting surface; the free end of the guide post passes through the guide hole, and the limiting surface and the limiting mating surface are in contact with each other; At least one elastic element is connected between the first mounting plate and the second mounting plate and is in a pre-compressed state so that the second mounting plate keeps the limiting mating surface and the limiting surface in constant contact when there is no external force, and can make adaptive movement relative to the guide post under the action of external force, and automatically reset to the contact state after the external force disappears; The charging gun is fixedly connected to the mounting surface of the second mounting plate.

[0009] As an optional implementation, the free end of the guide post is a ball-head structure, and the limiting surface is the outer spherical surface of the ball-head structure; the guide hole is a stepped hole formed by the coaxial connection of a large hole section and a small hole section, the limiting mating surface is an annular concave spherical surface adapted to the outer spherical surface, and the annular concave spherical surface is an arc-shaped transition surface connecting the inner wall surface of the large hole section and the inner wall surface of the small hole section; the second mounting plate can rotate relative to the ball-head structure and can reciprocate along the axial direction of the guide post.

[0010] As another optional implementation, the free end of the guide post is a coaxial column structure, and the limiting surface is the annular end face of the coaxial column structure; the guide hole is a countersunk hole formed by the coaxial connection of a countersunk section and a through hole section, the limiting mating surface is an annular stepped surface adapted to the annular end face, and the annular stepped surface is an annular transition surface perpendicular to the axial direction connecting the inner wall surface of the countersunk section and the inner wall surface of the through hole section; the second mounting plate can rotate around the axis of the guide post, and can also reciprocate along the axial direction of the guide post.

[0011] As another optional implementation, the number of guide posts is one, and the guide post is disposed at the center of the first mounting plate.

[0012] As another optional implementation, the number of guide posts is three, and the three guide posts are evenly distributed in a circular pattern on the first mounting plate; the three guide posts are of equal length.

[0013] As another optional implementation, the ball head structure is a complete sphere or a hemisphere; wherein, the spherical end of the hemisphere is fixedly connected to the rod of the guide post, the planar end of the hemisphere is away from the rod, and the planar end of the hemisphere is provided with a mounting slot.

[0014] As another optional implementation, the current feedback control unit is used to electrically connect with the motors of each joint of the robot, collect the real-time current value of each joint, estimate the external force and torque on the flexible connection mechanism and the charging gun based on the joint dynamics model, and then generate attitude adjustment commands based on the estimated external force and torque to control the robot's robotic arm to adjust the insertion attitude of the charging gun.

[0015] As another optional implementation, the current feedback control unit has a built-in robot joint dynamics model, which is used to calculate the three-axis forces Fx, Fy, Fz and the torques Rx, Ry, Rz around the three axes in the coordinate system of the charging gun end tool based on the real-time current values ​​of each joint; the current feedback control unit has preset safety thresholds for torque in each direction, and when the torque in any direction exceeds the corresponding safety threshold, a pause insertion command is generated and the attitude adjustment process is triggered.

[0016] The second aspect of this invention discloses an adaptive control method for the flexible charging gun posture of an automatic charging robot based on current feedback, applied to the flexible charging gun device for an automatic charging robot described in the first aspect of this invention. The method includes the following steps: S1. Contact detection: The robot's robotic arm moves the flexible plug-in device to the front of the charging port. When the charging gun is detected to be in contact with the charging port, the current feedback acquisition process is initiated. S2. External Force and Torque Estimation: Collect the real-time current values ​​of each joint of the robot, and calculate the three-axis forces Fx, Fy, Fz and the torques Rx, Ry, Rz around the three axes in the tool coordinate system of the charging gun end effector based on the joint dynamics model; S3. Attitude Deviation Judgment: The calculated torque in each direction is compared with the preset attitude deviation threshold. If the absolute value of the torque in any direction is greater than the corresponding attitude deviation threshold, it is determined that there is an attitude deviation in that direction. S4. Closed-loop attitude adjustment: Based on the direction and magnitude of the attitude deviation, control the robot's robotic arm to rotate around the corresponding axis to adjust the attitude of the charging gun, and monitor the torque value in that direction in real time until the absolute value of the torque is less than the attitude deviation threshold. S5. Safe Insertion: After the attitude adjustment is completed, control the charging gun to insert into the charging port in a straight line along the insertion direction. During the insertion process, continuously monitor the torque in each direction. If the torque exceeds the safety threshold, the insertion is paused and the process returns to step S4 for attitude correction. If the insertion conditions are still not met after the number of consecutive corrections reaches the preset maximum number of corrections, the insertion process is terminated and an abnormal alarm signal is issued. S6. Pull-out protection: After charging is completed, first perform attitude zeroing adjustment to make the torque in all directions approach 0, and then control the charging gun to exit the charging port in a straight line along the pull-out direction.

[0017] As an optional implementation, in step S4, the attitude adjustment adopts a proportional control method, where the adjustment angle is proportional to the magnitude of the torque; or adopts a fixed step size adjustment method, rotating by a preset angle step size Δθ each time until the torque converges to within the threshold; and, in step S4, the attitude adjustment adopts a parallel execution method in each direction, or a method that executes sequentially according to the priority of torque magnitude, and prioritizes adjusting the direction with the largest absolute value of torque.

[0018] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: This invention, through the limiting fit between the guide post and the guide hole, and the elastic force of the pre-compressed elastic element, enables the second mounting plate to perform multi-directional adaptive movement under external force, effectively compensating for positioning deviations and attitude errors between the charging gun and the charging port. The pre-compressed elastic element ensures that the limiting fit surface of the second mounting plate remains constantly in contact with the limiting surface when there is no external force, and automatically resets to the initial state after the external force disappears. Combined with the hard limiting effect of the guide post, it ensures the positional accuracy and attitude consistency of the charging gun after each insertion and removal, avoiding attitude drift after long-term use. No additional expensive components such as a six-dimensional force sensor are required. The flexible plug-in / plug-out function can be achieved solely through a mechanical structure, significantly reducing the manufacturing cost of the automatic charging robot and facilitating large-scale application. By opening a wiring through hole in the center of the guide column, the power supply wire of the charging gun passes through the inside of the mechanism, avoiding wear and electromagnetic interference caused by exposed wires. At the same time, the overall structure is more compact and meets the size restrictions of the charging head. Two guide column implementation methods are provided: ball head structure and coaxial column structure, as well as different arrangement schemes with one or three guide columns. These can be flexibly selected according to different degrees of freedom requirements, force requirements, and application scenarios, making it widely applicable.

[0019] This invention further adds a current feedback control unit to the passive flexible structure. By collecting the robot's joint current to estimate the external force and torque at the end effector, it actively controls the robotic arm to adjust the insertion posture of the charging gun. This solves the technical defect of existing passive flexible charging gun devices that can only passively tolerate errors and cannot actively correct posture deviations, significantly improving the success rate of charging gun insertion. By actively adjusting the posture, the charging gun maintains the correct posture throughout the insertion process, eliminating the jamming force between the charging gun and the charging port caused by incorrect posture, effectively reducing the probability of extraction failure, and solving the problem of insertion posture deviation easily causing extraction jamming in the prior art. No additional force sensor is required; the estimation of external force and torque can be achieved using the robot's own joint current collection function, which greatly improves the charging gun performance while maintaining a low manufacturing cost. By preset safety thresholds for torque in each direction, the insertion action can be paused in time and the adjustment process can be triggered when the end effector is abnormally stressed, avoiding excessive force that could damage the charging interface or the vehicle, and ensuring the safety and reliability of the charging gun insertion process.

[0020] This invention employs a complete process of "contact detection - torque estimation - deviation judgment - closed-loop adjustment" to correct the charging gun's posture deviation in real time, ensuring the charging gun is always inserted into the charging port in the correct posture, effectively reducing insertion failures and equipment damage caused by incorrect posture. Multiple protection measures, including torque safety threshold monitoring, joint judgment of insertion depth and axial force, and limit of joint current safety range, comprehensively cover various abnormal conditions during the insertion process, ensuring safety and reliability. Offline calibration establishes the correspondence between the insertion force and the joint current safety range of a single robot, eliminating individual differences between different robots and improving the universality and adaptability of the control method. Before removal, a posture zeroing adjustment is performed to bring the torque in all directions close to zero. Combined with the hard limit reset effect of the flexible connection mechanism, this ensures the charging gun maintains the correct posture during removal, effectively avoiding jamming and improving the success rate of removal. An impedance control model is used to regulate the robot's output force, ensuring the charging gun maintains appropriate contact force during insertion, guaranteeing reliable insertion while avoiding impact damage to the equipment, thus improving the stability of the insertion process. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0022] Figure 1 This is a schematic diagram of the structure of a flexible connection mechanism disclosed in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a first mounting plate disclosed in an embodiment of the present invention; Figure 3 This is a cross-sectional structural diagram of a first mounting plate disclosed in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a second mounting plate disclosed in an embodiment of the present invention; Figure 5 This is a cross-sectional structural diagram of a second mounting plate disclosed in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a guide post disclosed in an embodiment of the present invention; Figure 7 This is a schematic diagram of another guide post structure disclosed in an embodiment of the present invention; Figure 8 This is a method disclosed in the embodiments of the present invention that has Figure 7 A cross-sectional schematic diagram of the flexible connection mechanism of the guide column shown. Figure 9This is a schematic diagram of another guide post structure disclosed in an embodiment of the present invention; Figure 10 This is a method disclosed in the embodiments of the present invention that has Figure 9 A cross-sectional schematic diagram of the flexible connection mechanism of the guide column shown. Figure 11 This is a schematic diagram of the structure of a flexible charging gun device for an automatic charging robot disclosed in an embodiment of the present invention; Figure 12 This is a flowchart illustrating an adaptive control method for the flexible charging gun posture of an automatic charging robot based on current feedback, as disclosed in an embodiment of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 See Figures 1-11 This invention discloses a flexible charging gun device for an automatic charging robot, comprising: a flexible connection mechanism 5, a charging gun 6, and a current feedback control unit (not shown in the accompanying drawings). The current feedback control unit is used to collect robot operating status information and control the robot's robotic arm to adjust the insertion posture of the charging gun accordingly. The flexible connection mechanism 5 includes: The first mounting plate 1 is used to be fixedly connected to the robotic arm end 7 of the robot. The second mounting plate 2 is disposed opposite to the first mounting plate 1. The outer side of the second mounting plate 2 has a mounting surface for connecting the charging gun 6. The second mounting plate 2 has at least one through guide hole 21, and the guide hole 21 has a limiting mating surface 211. At least one guide post 3 is fixedly disposed on the side of the first mounting plate 1 facing the second mounting plate 2, and the free end of the guide post 3 has a limiting surface 31; the free end of the guide post 3 passes through the guide hole 21, and the limiting surface 31 and the limiting mating surface 211 are in contact with each other; At least one elastic element 4 is connected between the first mounting plate 1 and the second mounting plate 2 and is in a pre-compressed state, so that the second mounting plate 2 keeps the limiting mating surface 211 and the limiting surface 31 in constant contact when there is no external force, and can make adaptive movement relative to the guide post 3 under the action of external force, and automatically reset to the contact state after the external force disappears. The charging gun 6 is fixedly connected to the mounting surface of the second mounting plate 2.

[0025] This invention, through the limiting fit between the guide post 3 and the guide hole 21, and the elastic force of the pre-compressed elastic element 4, enables the second mounting plate 2 to perform multi-directional adaptive movement under external force, effectively compensating for the positioning deviation and attitude error between the charging gun 6 and the charging port. The pre-compressed elastic element 4 ensures that the second mounting plate 2 always maintains a constant fit between the limiting fit surface 211 and the limiting surface 31 when there is no external force, and automatically resets to the initial state after the external force disappears. Combined with the hard limiting effect of the guide post 3, it ensures the positional accuracy and attitude consistency of the charging gun 6 after each insertion and removal, avoiding attitude drift after long-term use. It eliminates the need for expensive components such as a six-dimensional force sensor, achieving flexible insertion and removal function through a purely mechanical structure, significantly reducing the manufacturing cost of the automatic charging robot and facilitating large-scale promotion and application.

[0026] See Figures 7-8 In an optional embodiment, the guide post 3 is a ball-head structure guide post 3A, and the limiting surface 31 is the outer spherical surface 31A of the ball-head structure; the guide hole 21 is a first guide hole 21A adapted to the ball-head structure guide post 3A, the first guide hole 21A is a stepped hole formed by coaxially connecting a large hole section 212A and a small hole section 213A, the limiting mating surface 211 is an annular concave spherical surface 211A adapted to the outer spherical surface 31A, the annular concave spherical surface 211A is an arc-shaped transition surface connecting the inner wall surface of the large hole section 212A and the inner wall surface of the small hole section 213A; the second mounting plate 2 can rotate relative to the ball-head structure guide post 3A, and can reciprocate along the axial direction of the guide post 3A.

[0027] Optionally, the radius of curvature of the annular concave spherical surface 211A is equal to the radius of curvature of the outer spherical surface 31A of the ball-head structure guide post 3A, and the center of the annular concave spherical surface 211A is located on the central axis of the ball-head structure guide post 3A, so that the outer spherical surface 31A and the annular concave spherical surface 211A form a spherical mating pair with surface-to-surface contact; the upper edge of the annular concave spherical surface 211A is smoothly and tangentially connected to the inner wall surface of the large hole section 212A, and the lower edge is smoothly and tangentially connected to the inner wall surface of the small hole section 213A, forming a transition structure connecting the large hole section 212A and the small hole section 213A.

[0028] See Figures 9-10In another optional embodiment, the guide post 3 is a coaxial cylindrical structure guide post 3B, and the limiting surface 31 is an annular end face 31B of the coaxial cylindrical structure; the guide hole 21 is a second guide hole 21B adapted to the coaxial cylindrical structure guide post 3B, the second guide hole 21B is a countersunk hole formed by the coaxial connection of the countersunk section 214B and the through hole section 215B, the limiting mating surface 211 is an annular stepped surface 211B adapted to the annular end face 31B, the annular stepped surface 211B is an annular transition surface perpendicular to the axial direction connecting the inner wall surface of the countersunk section 214B and the inner wall surface of the through hole section 215B; the second mounting plate 2 can rotate around the axis of the coaxial cylindrical structure guide post 3B, and can also reciprocate along the axial direction of the guide post 3B.

[0029] In another optional embodiment, the number of guide posts 3 is one, and the guide post 3 is disposed at the center of the first mounting plate 1.

[0030] In another optional embodiment, the number of guide posts 3 is three, and the three guide posts 3 are evenly distributed in a circular pattern on the first mounting plate 1; the three guide posts 3 are of equal length.

[0031] In another optional embodiment, the ball head structure is a complete sphere or a hemisphere; wherein, the spherical end of the hemisphere is fixedly connected to the rod 33 of the guide post 3, the planar end of the hemisphere is away from the rod 33, and the planar end of the hemisphere is provided with a mounting slot 34.

[0032] Optionally, the maximum lateral shear force that a single hemispherical guide post 3A can withstand should not be less than the ratio of the maximum insertion / extraction force of the robotic arm end 7 to the number of guide posts 3. This ratio is determined based on the design principle of load sharing to prevent the guide posts 3 from being sheared during insertion / extraction and to ensure the long-term reliability of the mechanism. For example, assuming the maximum axial insertion / extraction force of the robotic arm end 7 is 1815N, and the load is shared equally by three guide posts 3, then the maximum lateral shear force of a single hemispherical guide post 3A should not be less than 605N.

[0033] Optionally, the diameter of the cylindrical rod 33 of the hemispherical guide post 3A is determined based on the maximum transverse shear force and the shear strength of the selected material, ensuring that the shear resistance of the rod 33 is not less than the maximum transverse shear force it can withstand, and meeting the structural strength requirements with the lowest processing cost. For example, assuming the guide post 3 is made of 45 steel, the minimum rod 33 diameter corresponding to a maximum transverse shear force of 605N is 3mm, then the diameter of the cylindrical rod 33 is not less than 3mm.

[0034] Optionally, the theoretical design range of the spherical portion of the hemispherical guide post 3A can be 0-11mm. The upper limit of 11mm simultaneously meets the national standard's maximum outer diameter limit for charging heads and the space requirements for the charging cable routing. The lower limit of 0mm is the theoretical design extreme value. In actual engineering, it is limited by the aforementioned maximum lateral shear force requirement. For example, in the aforementioned example, the spherical radius of 45 steel is not less than 3mm, so the actual range is 3-11mm. Based on this, considering ease of installation, processing difficulty, and strength margin, assuming the guide post 3 is made of 45 steel, and using three hemispherical guide posts 3A, a hemispherical guide post 3A with a radius of 6mm is optimal.

[0035] See Figures 7-8 In another optional embodiment, the center of the guide post 3 is provided with an axially penetrating wiring through hole 32; the first mounting plate 1 is provided with a first through hole 16 communicating with the wiring through hole 32, and the guide hole 21 corresponding to the guide post 3 constitutes a second through hole communicating with the wiring through hole 32.

[0036] In another alternative embodiment, the number of elastic elements 4 is at least two, and all elastic elements 4 are evenly distributed on the first mounting plate 1 and are arranged alternately with the guide posts 3.

[0037] In another optional embodiment, the elastic element 4 is a compression spring; the first mounting plate 1 has a spring receiving groove 12 corresponding to the compression spring on the side facing the second mounting plate 2, and a limiting rod 13 is fixedly provided at the bottom center of the spring receiving groove 12; the compression spring is sleeved on the outside of the limiting rod 13, and one end of the compression spring abuts against the bottom of the spring receiving groove 12. The second mounting plate 2 has through-type spring mounting stepped holes 22 corresponding to the compression springs. The spring mounting stepped holes 22 are formed by coaxially connecting a large through hole section 221 close to the first mounting plate 1 and a small through hole section 222 away from the first mounting plate 1. A spring abutting step surface 223 is formed between the large through hole section 221 and the small through hole section 222. The other end of the compression spring abuts against the spring abutting step surface 223. The diameter of the small through hole section 222 is larger than the diameter of the limiting rod 13.

[0038] Optionally, the number and arrangement of compression springs are determined based on the magnitude of the preload, the uniformity of force distribution, and structural interference requirements.

[0039] Optionally, the spring force range of a single compression spring is determined based on the total safe insertion / removal range, the number of springs, and the initial preload requirement. The total insertion / removal force is distributed using a load-sharing design principle, simultaneously meeting the dual requirements of initial posture stability and safety during insertion / removal. For example, assuming the safe insertion / removal range is 85N-180N, and the total insertion / removal force is evenly distributed among four compression springs, the theoretical spring force range of a single compression spring is 21.25N-45N, with the maximum spring force not exceeding 45N. The initial preload of the spring needs to be greater than 24N to overcome the weight of the charging head and ensure its fixed position. Therefore, the actual effective preload range of a single compression spring is 24N-45N, which simultaneously meets the initial posture stability requirement and the total safe insertion / removal range limitation.

[0040] Optionally, the selection of compression springs is based on Hooke's Law formula F=Kx, where F is the spring force, K is the spring stiffness coefficient, and x is the spring compression. The spring with the corresponding stiffness coefficient is selected according to the required preload range and the allowable compression stroke to achieve precise control of the spring force and ensure the adaptive performance of the flexible connection mechanism 5.

[0041] Optionally, the maximum outer contour dimension of the flexible connection mechanism 5 shall not exceed the outer contour dimension of the charging gun.

[0042] In another optional embodiment, the current feedback control unit is used to electrically connect with the motors of each joint of the robot, collect the real-time current value of each joint, estimate the external force and torque on the flexible connection mechanism and the charging gun based on the joint dynamics model, and then generate attitude adjustment commands based on the estimated external force and torque to control the robot's robotic arm to adjust the insertion attitude of the charging gun.

[0043] In another optional embodiment, the current feedback control unit has a built-in robot joint dynamics model, which is used to calculate the three-axis forces Fx, Fy, Fz and the torques Rx, Ry, Rz around the three axes in the coordinate system of the charging gun end tool based on the real-time current values ​​of each joint; the current feedback control unit has preset safety thresholds for torque in each direction, and when the torque in any direction exceeds the corresponding safety threshold, a pause insertion command is generated and the attitude adjustment process is triggered.

[0044] Example 2 See Figure 12 This invention discloses an adaptive control method for the flexible charging gun posture of an automatic charging robot based on current feedback, applied to the flexible charging gun device for the automatic charging robot described in Embodiment 1. The method includes the following steps: S1. Contact Detection: The robot's robotic arm moves the flexible charging gun device to the front of the charging port. When the charging gun is detected to be in contact with the charging port, the current feedback acquisition process is initiated.

[0045] S2. External Force and Torque Estimation: Collect the real-time current values ​​of each joint of the robot, and calculate the three-axis forces Fx, Fy, Fz and the torques Rx, Ry, Rz around the three axes in the tool coordinate system of the charging gun end based on the joint dynamics model.

[0046] S3. Attitude Deviation Judgment: The calculated torque in each direction is compared with the preset attitude deviation threshold. If the absolute value of the torque in any direction is greater than the corresponding attitude deviation threshold, it is determined that there is an attitude deviation in that direction.

[0047] S4. Closed-loop attitude adjustment: Based on the direction and magnitude of the attitude deviation, control the robot's robotic arm to rotate around the corresponding axis to adjust the attitude of the charging gun, and monitor the torque value in that direction in real time until the absolute value of the torque is less than the attitude deviation threshold.

[0048] S5. Safe Insertion: After the attitude adjustment is completed, control the charging gun to insert into the charging port in a straight line along the insertion direction. During the insertion process, continuously monitor the torque in each direction. If the torque exceeds the safety threshold, the insertion is paused and the process returns to step S4 for attitude correction. If the insertion conditions are still not met after the number of consecutive corrections reaches the preset maximum number of corrections, the insertion process is terminated and an abnormal alarm signal is issued.

[0049] S6. Pull-out protection: After charging is completed, first perform attitude zeroing adjustment to make the torque in all directions approach 0, and then control the charging gun to exit the charging port in a straight line along the pull-out direction.

[0050] In an optional embodiment, in step S4, the attitude adjustment adopts a proportional control method, where the adjustment angle is proportional to the magnitude of the torque; or a fixed step size adjustment method, where the rotation is a preset angle step size Δθ each time until the torque converges to within the threshold.

[0051] In another optional embodiment, in step S4, the attitude adjustment is performed in parallel in each direction or in order of priority according to the magnitude of torque, and the direction with the largest absolute value of torque is adjusted first.

[0052] In yet another optional embodiment, force control safety limiting steps for each axis of the robot are also included, specifically: S0. Offline calibration: For a single robot, perform insertion tests under preset normal insertion conditions, collect the maximum working current of each joint during the normal insertion process, determine the safe current range of each joint under different working conditions, and establish the correspondence between insertion force and the safe current range of each joint. S51. During the safe insertion process in step S5, the working current of each joint of the robot is collected in real time, and the current feedback control unit limits the working current of each joint to the safe current range corresponding to the current insertion force. S52. If the operating current of any joint exceeds the corresponding safe current range, the end force is determined to be abnormal, the insertion pause action is executed, the attitude adjustment process is triggered or the insertion process is exited and an alarm signal is issued.

[0053] In this embodiment, the aforementioned preset normal insertion conditions cover all typical conditions that enable stable insertion, such as: different insertion forces: 90N, 100N, 150N, 180N; different insertion points: near point, far point; different insertion directions: forward direction, left offset direction, right offset direction; different force control speeds: 10mm / s, 20mm / s, 30mm / s. All insertion tests in step S0 are performed under the premise that the charging gun can be normally inserted into the charging port. The maximum operating current of each joint during normal insertion is recorded, serving as the benchmark value for the current safety range. When abnormal conditions such as jamming, jamming, or misalignment occur, the joint current will significantly exceed this benchmark range, thereby triggering the safety protection mechanism. For each insertion force, the maximum current value of each joint corresponding to all insertion points, all insertion directions, and all force control speeds under that force is taken as the upper limit of the current safety range for that corresponding joint; combined with the lower limit of the rated operating current of the robot joint motor, this constitutes the current safety range under that condition. For example, based on the measured data of a six-axis robotic arm, the global maximum current values ​​of each joint (six axes) under all normal insertable working conditions are: J1: 4.17A, J2: 11.7A, J3: 6.79A, J4: 0.84A, J5: 1.38A, J6: 1.82A. This value is the global upper limit of the safe current range under all working conditions.

[0054] This embodiment establishes the safe current range for each joint based on the measured current under verified normal gun insertion conditions. The current feedback control unit actively limits the operating current of each joint within the safe range, ensuring the smooth progress of the normal gun insertion process and preventing the joint motors from being damaged due to overload under abnormal conditions, thus extending the service life of the robot.

[0055] In another optional embodiment, in step S3, the attitude deviation thresholds include a roll direction threshold Rx_th, a pitch direction threshold Ry_th, and a yaw direction threshold Rz_th; If |Rx|>Rx_th, it is determined that there is an attitude deviation in the roll direction; If |Ry|>Ry_th, it is determined that there is an attitude deviation in the pitch direction; If |Rz|>Rz_th, it is determined that there is an attitude deviation in the yaw direction.

[0056] In another optional embodiment, in step S5, when the charging gun insertion depth reaches a preset insertion depth, the magnitude of the axial force Fz is detected: If Fz is less than the preset minimum insertion force threshold, it is determined that the insertion is not complete, and the charging gun is controlled to exit and steps S1-S5 are re-executed; If Fz is greater than the preset maximum safety force threshold, an insertion abnormality is determined, the charging gun is immediately withdrawn and an alarm signal is issued.

[0057] In this embodiment, the preset insertion depth is the standard depth at which the charging gun and the charging port are fully inserted to ensure that the charging gun is inserted in place and forms a stable and reliable electrical connection. This depth can be determined according to the general technical requirements of electric vehicle conductive charging interfaces.

[0058] In yet another optional embodiment, in step S2, the joint dynamics model is based on the formula τ=J T F is established, where τ is the torque vector of each joint of the robot, J is the Jacobian matrix of the robot in its current pose, and F is the external force vector at the end of the charging gun. Real-time current values ​​of each joint of the robot are collected, and a joint dynamics model is established based on this current. The estimated external force at the end of the charging gun is obtained from the joint dynamics model. Establishing the joint dynamics model and estimating the external force on the robot based on the current are existing technologies, which can be implemented by those skilled in the art using conventional techniques.

[0059] In another optional embodiment, in step S5, the output force of the robot is controlled using an impedance control model during the insertion process. The impedance control model is: M +B =F d -F estimate Where M is the inertia coefficient, B is the damping coefficient, and x is the pose in the Cartesian direction. The speed of the robot's end effector. F is the acceleration of the robot's end effector. d For the desired insertion force, F estimate The actual external force is estimated based on the current.

[0060] The content disclosed in the embodiments of this invention is only a preferred embodiment of the invention and is used only to illustrate the technical solutions of the invention, not to limit it. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this invention.

Claims

1. A flexible charging gun device for an automatic charging robot, characterized in that, include: Flexible connection mechanism, charging gun, and current feedback control unit; The current feedback control unit is used to collect robot operating status information and control the robot's robotic arm to adjust the insertion posture of the charging gun accordingly. The flexible connection mechanism includes: The first mounting plate is used for fixed connection to the end of the robot's robotic arm; The second mounting plate is disposed opposite to the first mounting plate. The outer side of the second mounting plate has a mounting surface for connecting the charging gun. The second mounting plate has at least one through guide hole, and a limiting mating surface is provided in the guide hole. At least one guide post is fixedly disposed on the side of the first mounting plate facing the second mounting plate, and the free end of the guide post has a limiting surface; the free end of the guide post passes through the guide hole, and the limiting surface and the limiting mating surface are in contact with each other; At least one elastic element is connected between the first mounting plate and the second mounting plate and is in a pre-compressed state so that the second mounting plate keeps the limiting mating surface and the limiting surface in constant contact when there is no external force, and can make adaptive movement relative to the guide post under the action of external force, and automatically reset to the contact state after the external force disappears; The charging gun is fixedly connected to the mounting surface of the second mounting plate.

2. The flexible insertion gun device according to claim 1, characterized in that, The free end of the guide post is a ball-shaped structure, and the limiting surface is the outer spherical surface of the ball-shaped structure; the guide hole is a stepped hole formed by the coaxial connection of a large hole section and a small hole section, and the limiting mating surface is an annular concave spherical surface adapted to the outer spherical surface, and the annular concave spherical surface is an arc-shaped transition surface connecting the inner wall surface of the large hole section and the inner wall surface of the small hole section; the second mounting plate can rotate relative to the ball-shaped structure and can reciprocate along the axial direction of the guide post.

3. The flexible insertion gun device according to claim 1, characterized in that, The free end of the guide post is a coaxial column structure, and the limiting surface is the annular end face of the coaxial column structure; the guide hole is a countersunk hole formed by the coaxial connection of a countersunk section and a through hole section, and the limiting mating surface is an annular stepped surface adapted to the annular end face. The annular stepped surface is an annular transition surface perpendicular to the axial direction connecting the inner wall surface of the countersunk section and the inner wall surface of the through hole section; the second mounting plate can rotate around the axis of the guide post and can reciprocate along the axial direction of the guide post.

4. The flexible insertion gun device according to any one of claims 1-3, characterized in that, The number of guide posts is one, and the guide post is located at the center of the first mounting plate.

5. The flexible insertion gun device according to any one of claims 1-3, characterized in that, The number of guide posts is three, and the three guide posts are evenly distributed in a circle on the first mounting plate; the three guide posts are of equal length.

6. The flexible insertion gun device according to claim 2, characterized in that, The ball head structure is a complete sphere or a hemisphere; wherein, the spherical end of the hemisphere is fixedly connected to the rod of the guide post, the planar end of the hemisphere is away from the rod, and the planar end of the hemisphere is provided with a mounting slot.

7. The flexible insertion gun device according to any one of claims 1 to 6, characterized in that, The current feedback control unit is used to electrically connect with the motors of each joint of the robot, collect the real-time current value of each joint, estimate the external force and torque on the flexible connection mechanism and the charging gun based on the joint dynamics model, and then generate attitude adjustment commands based on the estimated external force and torque to control the robot's robotic arm to adjust the insertion attitude of the charging gun.

8. The flexible insertion gun device according to claim 7, characterized in that, The current feedback control unit has a built-in robot joint dynamics model, which is used to calculate the three-axis forces Fx, Fy, and Fz and the torques Rx, Ry, and Rz around the three axes in the coordinate system of the charging gun end tool based on the real-time current values ​​of each joint. The current feedback control unit has preset safety thresholds for torque in each direction. When the torque in any direction exceeds the corresponding safety threshold, a pause insertion command is generated and the attitude adjustment process is triggered.

9. A flexible charging gun attitude adaptive control method for an automatic charging robot based on current feedback, characterized in that, Applied to the flexible insert gun device of claim 7 or 8, the method includes the following steps: S1. Contact detection: The robot's robotic arm moves the flexible plug-in device to the front of the charging port. When the charging gun is detected to be in contact with the charging port, the current feedback acquisition process is initiated. S2. External Force and Torque Estimation: Collect the real-time current values ​​of each joint of the robot, and calculate the three-axis forces Fx, Fy, Fz and the torques Rx, Ry, Rz around the three axes in the tool coordinate system of the charging gun end effector based on the joint dynamics model; S3. Attitude Deviation Judgment: The calculated torque in each direction is compared with the preset attitude deviation threshold. If the absolute value of the torque in any direction is greater than the corresponding attitude deviation threshold, it is determined that there is an attitude deviation in that direction. S4. Closed-loop attitude adjustment: Based on the direction and magnitude of the attitude deviation, control the robot's robotic arm to rotate around the corresponding axis to adjust the attitude of the charging gun, and monitor the torque value in that direction in real time until the absolute value of the torque is less than the attitude deviation threshold. S5. Safe Insertion: After the attitude adjustment is completed, control the charging gun to insert into the charging port in a straight line along the insertion direction. During the insertion process, continuously monitor the torque in each direction. If the torque exceeds the safety threshold, the insertion is paused and the process returns to step S4 for attitude correction. If the insertion conditions are still not met after the number of consecutive corrections reaches the preset maximum number of corrections, the insertion process is terminated and an abnormal alarm signal is issued. S6. Pull-out protection: After charging is completed, first perform attitude zeroing adjustment to make the torque in all directions approach 0, and then control the charging gun to exit the charging port in a straight line along the pull-out direction.

10. The control method according to claim 9, characterized in that, In step S4, the attitude adjustment adopts a proportional control method, where the adjustment angle is proportional to the magnitude of the torque; or a fixed step adjustment method, where the rotation is done by a preset angle step Δθ each time, until the torque converges to within the threshold. Furthermore, in step S4, the attitude adjustment is performed in parallel in each direction or in order of priority based on the magnitude of torque, with priority given to adjusting the direction with the largest absolute value of torque.

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