Self-adaptive interference pin assembling device and method

Abstract

The invention relates to a self-adaptive interference pin assembling device and method, and belongs to the technical field of intelligent manufacturing and robotics.The self-adaptive interference pin assembling device designs a three-jaw centering clamp, a rotating disc is connected with three connecting rods, the three connecting rods synchronously move around the center point of the rotating disc, and the connecting rods transmit the rotating action of the rotating disc to sliding blocks; the sliding block is pushed to move towards the center point of the top plate or away from the center point of the top plate; the sliding blocks move to drive the clamping fingers to be opened and closed, opening and closing of the clamping fingers always keep the center of the top plate aligned with the pin, the clamping force can be adjusted, it is ensured that the pin is located at the center position, and high repeated positioning precision is provided. The six-dimensional force sensor is installed at the tail end of the mechanical arm, and force tracking in the assembling process is achieved; in addition, an impedance control law is used in the assembling process, and flexible pin assembling is achieved.

Description

Technical Field

[0001] The present invention relates to the technical fields of intelligent manufacturing and robotics, and particularly relates to an adaptive interference pin assembly device and an assembly method. Background Art

[0002] In the fields of mechanical manufacturing and industrial production, interference pin assembly is a process to achieve a tight connection through the elastic deformation of materials, which is widely used in the automotive, electronics, aerospace, and precision machinery manufacturing industries. Its assembly quality directly affects the product positioning accuracy, load transfer efficiency, and service life. However, there are still the following prominent problems in the actual application of the existing interference pin assembly technology: (I) Limitations of manual assembly: (1) Unreliable contact force control. In the existing technology, manual assembly relies on the operator to manually tap or press in the pin, and it is impossible to precisely control the contact force between the pin and the pin hole during the assembly process. Excessive impact force may cause deformation, surface damage, or even microcracks in the pin or the base material; too small a force cannot ensure the interference amount, resulting in loose fit. (2) Insufficient efficiency and consistency. The rhythm of manual assembly depends on the operator's proficiency, making it difficult to meet the requirements of high-tempo production in modern industry. (II) Insufficient flexibility of fixed automation equipment: (1) Lack of adaptive adjustment ability. Existing fixed automation assembly equipment (such as hydraulic presses and pneumatic presses) usually completes the assembly with preset parameters (such as pressure, stroke, speed), and cannot perceive the actual contact state between the pin and the pin hole in real time. (2) Poor adaptability to multiple varieties. The fixtures, molds, and sensors of fixed equipment are mostly specially designed, and it is difficult to quickly switch to adapt to pins with different sizes, shapes, or tolerance requirements. (3) High dependence on precision machining. Traditional equipment requires strict matching of the machining tolerances of the pin and the pin hole (such as H7 / h6 fit). If the dimensional deviation of the hole or the pin exceeds ±0.01 mm, the equipment will not be able to complete the assembly or cause the fit to fail. This forces enterprises to invest a large amount of cost in high-precision machining (such as CNC fine boring of holes), restricting the feasibility of small-batch and low-cost production. (III) Challenges of dynamic working conditions and maintenance: (1) Insufficient long-term reliability. In a long-term vibration, impact, or temperature change environment, the pins assembled by traditional interference assembly are prone to fit loosening due to material creep or fretting wear. (2) Difficult maintenance and replacement. The pins assembled by interference assembly require special tools (such as heaters or pullers) for disassembly, with complex operations and easy damage to the base. There are obvious shortcomings in the existing interference pin assembly methods: manual assembly cannot adaptively control the contact force, with low efficiency and poor consistency; while fixed automation equipment has problems such as insufficient flexibility and poor adaptability, and cannot meet the flexible production requirements of multiple varieties and small batches. Summary of the Invention

[0003] In view of the above problems, the present invention provides an adaptive interference pin assembly device and an assembly method. The present invention designs a three-jaw centering fixture, in which a turntable is connected to three connecting rods, and the three connecting rods move synchronously around the center point of the turntable. The connecting rods transmit the rotational movement of the turntable to the slider and push the slider to move towards or away from the center point of the top plate; the movement of each slider drives the opening and closing of each finger, and the opening and closing of each finger always keep the center of the top plate aligned with the pin, and the clamping force can be adjusted to ensure that the pin is positioned at the center position, providing high repeat positioning accuracy; the present invention installs a six-axis force sensor at the end of the robotic arm to realize force tracking during the assembly process; moreover, the present invention uses an impedance control law during the assembly process to realize compliant assembly of the pin.

[0004] The present invention provides an assembly method for an adaptive interference pin assembly device, including:

[0005] Step 1, establish the dynamic equation of the robotic arm;

[0006] Step 2, control each finger 31 to clamp the pin;

[0007] Step 3, move the three-jaw centering fixture 3 after clamping the pin in the current time period to above the position to be assembled;

[0008] Collect the force state and torque state of the pin in the current time period through the six-axis force sensor 2;

[0009] Step 4, control the pin in the current time period to contact the workpiece to be assembled, and detect whether it is in a normal contact state. If not, adjust the impedance control law of the three-jaw centering fixture 3 and enter Step 5; if so, enter Step 5;

[0010] Step 5, judge whether the pin after contact state detection in the current time period is subjected to abnormal force. If so, perform adaptive adjustment of the impedance parameters of the robotic arm in the current time period and enter Step 6; if not, enter Step 6;

[0011] Step 6, insert the pin after abnormal force detection in the current time period into the workpiece to be assembled, and judge whether there is a lateral force. If there is, adjust based on the impedance control law and enter Step 7; if not, enter Step 7;

[0012] Step 7, maintain the force in the insertion direction of the pin in the current time period to ensure that the pin smoothly enters the workpiece to be assembled.

[0013] Optionally, the specific steps of Step 3 include:

[0014] Based on inverse kinematics and the position to be assembled, obtain the expected motion states of the joints of the robotic arm in the current time period; substitute the expected motion states of the joints of the robotic arm in the current time period into the dynamic equation of the robotic arm to obtain the compensation torques of the joints in the current time period;

[0015] Based on the compensation torque of each joint in the current time period, adjust the joint angles of each joint of the robotic arm in the current time period, so that the three-jaw centering fixture 3 after gripping the pin moves above the position to be assembled in the current time period.

[0016] Optionally, the dynamic equation of the robotic arm is expressed as:

[0017]

[0018] where M(.) is the mass matrix, C(.) is the Coriolis force and centrifugal force term, g(.) is the gravity vector, τ is the joint torque, τ ext is the external disturbance joint torque, q is the joint position, is the joint angular acceleration, is the joint angular velocity.

[0019] Optionally, the impedance control law is expressed as:

[0020]

[0021] where F ext is the external force, M d is the desired inertia matrix of the fixture, B d is the desired damping matrix of the fixture, K d is the desired stiffness matrix of the fixture, x is the actual position of the fixture, is the actual velocity of the fixture, is the actual acceleration of the fixture, x d is the desired position of the fixture, is the desired velocity of the fixture, is the desired acceleration of the fixture.

[0022] Optionally, the abnormal force includes jamming and / or uneven assembly force.

[0023] Optionally, the specific steps for judging whether the pin is subjected to abnormal force in the current time period include:

[0024] Judge the force change rate of the pin received by the six-axis force sensor in the current time period and the surface roughness or contact force fluctuation of the workpiece to be assembled in the current time period.

[0025] Another object of the present invention is to provide an adaptive interference pin assembly device, including:

[0026] A robotic arm 1, a six-axis force sensor 2 and a three-jaw centering fixture 3;

[0027] One end of the robotic arm 1 is arranged on the operating table, and the other end can move in a three-dimensional space;

[0028] The other end of the robotic arm 1 is connected to the six - dimensional sensor 2; the six - dimensional sensor 2 is also connected to the three - jaw centering fixture 3.

[0029] Optionally, the three - jaw centering fixture 3 includes a plurality of clamping fingers 31, a plurality of sliders 32, a top plate 33, a plurality of connecting rods 34, and a turntable 35;

[0030] The top plate 33 is respectively connected to the plurality of clamping fingers 31 and the plurality of sliders 32; the plurality of connecting rods are respectively connected to the plurality of sliders and the turntable 35;

[0031] One end of each connecting rod is connected to the turntable, and the other end is connected to each corresponding slider;

[0032] Each slider is also respectively connected to the corresponding clamping finger 31; each slider is also respectively connected to the corresponding clamping finger (31);

[0033] The connecting rod is used to convert the tangential motion of the turntable into the radial motion of the slider;

[0034] One end of each connecting rod is connected to the turntable, and the other end is connected to each corresponding slider.

[0035] Optionally, the extension lines of the symmetry axes of each slider and each clamping finger all pass through the center point of the top plate;

[0036] The extension lines of the symmetry axes of each connecting rod all pass through the center point of the turntable.

[0037] Optionally, the geometric center of the clamping surface of each clamping finger is located on the extension line of the central axis of the three - jaw centering fixture.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] (1) By installing a six - dimensional force sensor at the end of the robotic arm in the present invention, force tracking during the assembly process is realized;

[0040] (2) The three - jaw centering fixture designed in the present invention can adjust the clamping force and ensure that the pin is positioned at the center position, providing high repeat positioning accuracy;

[0041] (3) By using impedance control during the assembly process in the present invention, compliant assembly of the pin is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings are only for the purpose of showing specific embodiments and are not considered as a limitation to the present invention.

[0043] Figure 1 It is a schematic diagram of the flowchart of the adaptive interference pin assembly method according to the embodiment of the present invention;

[0044] Figure 2Schematic diagram of a partial structure of the adaptive interference pin assembly device in the embodiment of the present invention;

[0045] Figure 3 Schematic diagram of an exploded view of the adaptive interference pin assembly device in the embodiment of the present invention;

[0046] Figure 4 Schematic diagram of an isometric view of the turntable three-jaw centering device in the embodiment of the present invention;

[0047] Figure 5 Schematic diagram of an exploded view of the turntable three-jaw centering device in the embodiment of the present invention;

[0048] Figure 6 Schematic diagram of a top view of the three-jaw centering device when the turntable rotates in the embodiment of the present invention;

[0049] Figure 7 Schematic diagram of a top view of the three-jaw centering device when the turntable is stationary in the embodiment of the present invention;

[0050] Figure 8 Schematic diagram of the adaptive interference pin assembly device in the embodiment of the present invention.

[0051] Reference numerals:

[0052] Robotic arm 1, six-axis force sensor 2, three-jaw centering fixture 3, clamping finger 31, slider 32, top plate 33, connecting rod 34, turntable 35, copper column 36, mounting plate 37, motor 38, bracket 39, bottom plate 40, central hole 37-1, groove 33-1, fingertip 31-1, connecting plate 31-2. Detailed implementation manners

[0053] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. In addition, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0054] A specific embodiment of the present invention, as Figure 1-8 , discloses an adaptive interference pin assembly device, including: a robotic arm 1, a six-axis force sensor 2, and a three-jaw centering fixture 3;

[0055] One end of the robotic arm 1 is arranged on the operation table, and the other end can move in a three-dimensional space;

[0056] The other end of the robotic arm 1 is connected to the six-axis sensor 2; the six-axis sensor 2 is also connected to the three-jaw centering fixture 3;

[0057] Optionally, the three-jaw centering fixture 3 includes a plurality of clamping fingers 31, a plurality of sliders 32, a top plate 33, a plurality of connecting rods 34, a turntable 35, and a motor 38;

[0058] The top plate 33 is respectively connected to the plurality of clamping fingers 31 and the plurality of sliders 32; the plurality of connecting rods are respectively connected to the plurality of sliders and the turntable 35; the turntable 35 is further connected to the motor 38;

[0059] The connecting rod is used to convert the tangential movement of the turntable into the radial movement of the slider.

[0060] Further, one end of each connecting rod is connected to the turntable, and the other end is connected to each corresponding slider;

[0061] Each slider is also respectively connected to the corresponding clamping finger 31;

[0062] Optionally, the three-jaw centering fixture 3 further includes a plurality of copper columns 36, a mounting plate 37, a bracket 39, and a bottom plate 40;

[0063] The motor 38 is respectively connected to the bottom plate 40 and the mounting plate 37 through the bracket 39; the motor shaft 38-1 of the motor 38 passes through the central hole 37-1 of the mounting plate 37 and is connected to the turntable 35 for torque transmission; the bottom plate 40 is connected to the six-axis force sensor 2 through a standard flange;

[0064] The mounting plate 37 and the top plate 33 are connected by a plurality of copper columns 36 to ensure that the turntable 35 and the plurality of connecting rods 34 can rotate smoothly in the space between the mounting plate 37 and the top plate 33.

[0065] Optionally, the center points of the top plate 33, the turntable 35, and the mounting plate 37 are all set on the central extension line of the three-jaw centering fixture;

[0066] Optionally, the top plate 33 is provided with a plurality of grooves 33-1;

[0067] Each slider 32 is respectively arranged in the corresponding groove 33-1 and is movably connected to the corresponding groove 33-1;

[0068] Each slider 32 respectively controls the corresponding clamping finger 31 to move radially around the center point of the top plate in each groove 33-1 to realize the opening and closing actions of each clamping finger 31;

[0069] Optionally, each clamping finger 31 includes a fingertip 31-1 and a connecting plate 31-2;

[0070] Each connecting plate is respectively connected to the corresponding slider and each fingertip.

[0071] Optionally, the extension lines of the symmetry axes of each slider and each clamping finger all pass through the center point of the top plate;

[0072] The extension lines of the symmetry axes of the respective connecting rods all pass through the center point of the turntable;

[0073] Optionally, the geometric centers of the clamping surfaces of the respective fingers are located on the extension line of the central axis of the three-jaw centering fixture;

[0074] The respective fingers are arranged at equal intervals around the center of the top plate; among them, every two fingers are symmetrically distributed along the center point of the turntable;

[0075] Optionally, the respective connecting rods are arranged at equal intervals around the center of the turntable; among them, the respective connecting rods are evenly distributed along the center point of the turntable;

[0076] The respective grooves and the respective sliders are arranged at equal intervals around the center of the top plate; among them, the respective grooves are evenly distributed along the center point of the top plate, and the respective sliders are evenly distributed along the center point of the top plate;

[0077] Exemplarily, the angle between the connection points of every two connecting rods on the turntable 35 is 120°;

[0078] The angles between every two grooves and every two sliders between the top plates are both 120°;

[0079] The angle between every two fingers on the top plate is 120°;

[0080] When the turntable 35 rotates, one end of each connecting rod simultaneously makes a circular motion around the center point of the turntable; optionally, the sizes and shapes of the respective connecting rods 34 are the same;

[0081] The sizes and shapes of the respective sliders are the same; the sizes and shapes of the respective grooves are the same;

[0082] In an embodiment of the present invention, when the turntable 35 is stationary, the extension lines of the symmetry axes of the respective connecting rods all pass through the center of the turntable, and at this time, the fixture opens and closes to the maximum extent;

[0083] When the turntable rotates, one end of each connecting rod rotates as the turntable rotates, and the extension lines of the symmetry axes of the respective connecting rods do not pass through the center of the turntable;

[0084] The present invention designs the turntable 35 and three connecting rods 34 as a driving mechanism, ensuring that the three sliders 32 move simultaneously, at the same speed, and at equal distances close to or away from the center point of the top plate; at the same time, three grooves are designed to limit that the three sliders can only move strictly along the grooves radially pointing to the center point of the top plate. Further, each finger 31 fixed on the slider moves radially along the three grooves pointing to the center point of the top plate together with the slider, and each finger moves linearly around the center point of the top plate along the extension line of its own symmetry axis, and the moving distances of the three fingers with respect to the center point of the top plate are always equal.

[0085] In one embodiment of the present invention, the rotation of the motor shaft 38-1 of the motor 38 further drives the turntable 35 to rotate clockwise or counterclockwise; one end of each connecting rod moves along with the turntable, so that the extension line of the symmetry axis of each connecting rod 34 is away from the center point of the turntable 35, and the other end of each connecting rod drives each slider 32 to slide away from the center point of the top plate, thereby opening each finger 31; subsequently, the motor shaft 38-1 drives the turntable 35 to rotate in the opposite direction, so that the extension line of the symmetry axis of each connecting rod 34 approaches the center point of the turntable, and the other end of each connecting rod pushes each slider to slide towards the center point of the top plate, closing the fixture and realizing the clamping action.

[0086] In the present invention, the rotation of the turntable 35 drives one end of each connecting rod to move along the center point of the turntable. When the turntable rotates, the rotation of one end of each connecting rod further drives each corresponding slider 32 to move radially around the center point of the turntable in each groove, ensuring that the pin is located at the center point of the top plate 33 during the grasping process.

[0087] In the present invention, the turntable 35 is connected to three connecting rods 34, and the three connecting rods move synchronously around the center point of the turntable. The connecting rod 34 transmits the rotation action of the turntable to the slider 32 and pushes the slider to move towards or away from the center point of the top plate; the movement of each slider drives the opening and closing of each finger 31, and the opening and closing of each finger always keep the center of the top plate aligned with the pin, that is, always keep the pin on the extension line of the central axis of the three-jaw centering fixture.

[0088] In the present invention, the movements of the three sliders all originate from the rotation of the turntable 35, and the initial driving actions received by each slider are completely synchronous. The turntable, as the only power input point, ensures the simultaneity of the movement.

[0089] In the present invention, the sliders driven by each connecting rod are constrained in symmetrically distributed radial grooves;

[0090] When the turntable rotates a certain angle, the magnitude and direction of the radial pulling force generated by each connecting rod on the slider it connects are exactly the same, and the slider is constrained to move in the corresponding groove to prevent deviation.

[0091] Another object of the present invention is to provide a method for using an adaptive interference pin assembly device, including:

[0092] Step 1, establish the dynamic equation of the robotic arm;

[0093] Step 2, the robotic arm 1 obtains the joint angles of the robotic arm in the current time period;

[0094] Adjust the joint angles of the robotic arm 1 in the current time period, move the three-jaw centering fixture 3 above the pin stock tray, control the fixture 3 to pick up the pin based on the control moment of the robotic arm 1, and at the same time keep the position of the pin at the center point of the top plate;

[0095] It can be understood that during the grasping process of the pin, it is always ensured that each finger 31 is located at the center point of the top plate; each finger opens or closes during the clamping process to achieve self-centering of the pin position.

[0096] Optionally, the fixture force is adjusted by the clamping force estimated by the motor current feedback to keep the clamping force within an appropriate range and avoid excessive or insufficient clamping force;

[0097] Exemplarily, the current feedback of the motor provides information about the motor load. The current of the motor is directly related to the torque. The larger the current value, the larger the torque and the stronger the clamping force. By adjusting the motor current, the clamping force can be controlled;

[0098] The motor adjusts the clamping force of the fingers by controlling the torque of the turntable 35.

[0099] Step 3: Based on the inverse kinematics and the position to be assembled, obtain the desired motion states of the joints of the robotic arm in the current time period; substitute the desired motion states of the joints of the robotic arm in the current time period into the dynamic equation of the robotic arm to obtain the compensation torque of each joint in the current time period;

[0100] Use the compensation torque of each joint in the current time period for feedforward control to drive the joints of the robotic arm and make the three-jaw centering fixture 3 quickly move above the position to be assembled after picking up the pin in the current time period;

[0101] Collect the force state and torque state of the pin in the current time period through the six-axis force sensor 2;

[0102] Optionally, the dynamic equation of the robotic arm is expressed as:

[0103]

[0104] where M(.) is the mass matrix of the joints, C(.) is the Coriolis force and centrifugal force terms of the joints, g(.) is the gravity vector of the joints, τ is the joint torque, τ ext is the external disturbance joint torque, is the joint angular acceleration vector, is the joint angular velocity, and q is the joint angle.

[0105] Optionally, the desired motion state includes the desired angle q d 、desired velocity and desired acceleration

[0106] Optionally, the compensation torque τ of each joint c , and the expression is:

[0107]

[0108] where τ c is the compensation torque, q d is the desired angle, is the desired speed.

[0109] Optionally, the states of the force and torque include the position, magnitude, and direction of the force; the position, magnitude, and direction of the torque;

[0110] Optionally, the data collected by the six-axis force sensor is transmitted to the control cabinet in real time through the Modbus485 protocol and saved to the database;

[0111] When the robotic arm grabs the pin with the fixture, the six-axis force sensor measures the contact force and torque between the pin and the fixture;

[0112] When the fixture of the robotic arm approaches the workpiece to be assembled, the six-axis force sensor measures the reaction force and torque of the workpiece on the robotic arm.

[0113] Furthermore, the data collected by the six-axis sensor includes:

[0114] The force in the X-axis direction, the force in the Y-axis direction, the force in the Z-axis direction, the torque rotating around the X-axis, the torque rotating around the Y-axis, and the torque rotating around the Z-axis;

[0115] Step 4: Control the pin to contact the workpiece to be assembled in the current time period, detect the contact state between the pin and the workpiece to be assembled in the current time period, and determine whether it belongs to the normal contact state. If not, go to Step 5;

[0116] If so, go to Step 6;

[0117] Step 5: Adjust the impedance control law of the three-jaw centering fixture according to the force and torque states of the pin in the current time period, obtain the updated force state and updated torque state of the pin in the current time period, and use them as the force state and torque state of the pin in the next time period, then go to Step 6;

[0118] Optionally, the specific steps for Step 4 to determine whether it belongs to the normal contact state include:

[0119] Obtain the force and moment state information of the pin during the current time period based on the six-axis force sensor, and compare it with the pre-stored normal contact state information in the database. If the force on the pin during the current time period exceeds the normal contact state threshold, the pin during the current time period belongs to an abnormal contact state, indicating that the pin during the current time period touches the hole wall or other problems occur; if the force on the pin during the current time period does not exceed the normal contact state threshold, the current time period belongs to the normal contact state;

[0120] Optionally, when the pin is not in contact with the workpiece to be assembled, increase the stiffness of the three-jaw centering fixture 3 to ensure movement along the desired position x d and maintain precise trajectory tracking;

[0121] Optionally, the specific steps for adjusting the impedance control law of the three-jaw centering fixture according to the force and moment state of the pin during the current time period include:

[0122] When the pin is in contact with the workpiece to be assembled and the pin is subjected to radial force and / or frictional interference;

[0123] Reduce the radial stiffness of the robotic arm during the current time period, and make fine adjustments to the robotic arm left and right to align the pin with the hole; the radial stiffness includes the stiffness in the left-right direction and the front-back direction;

[0124] Increase the damping of the robotic arm during the current time period;

[0125] Maintain the high axial stiffness of the current robotic arm to ensure continuous pushing of the pin with force; the axial stiffness includes the stiffness in the up-down direction;

[0126] Optionally, step 4 further includes establishing an impedance control law, and the specific steps include:

[0127] Model the relationship between the movement of the three-jaw centering fixture and the external force as a spring-damper-mass system, establish the impedance relationship between the movement of the finger and the external force based on the spring-damper-mass system, and obtain the impedance control law. The expression is:

[0128]

[0129] where F ext is the external force, the reaction force of the environment on the three-jaw centering fixture, including the contact force and frictional force, measured by the six-axis force sensor, M d is the desired inertia matrix of the fixture, B d is the desired damping matrix of the fixture, K d is the desired stiffness matrix of the fixture, x is the actual position of the fixture, is the actual velocity of the fixture, is the actual acceleration of the fixture, x d is the desired position of the fixture, is the expected speed of the fixture, is the expected acceleration of the fixture.

[0130] It can be understood that the workpiece to be assembled is the hole or surface to be assembled of the pin;

[0131] Optionally, set the initial axial stiffness and initial radial stiffness of the robotic arm according to the interference range of the pin;

[0132] The axial stiffness is greater than the radial stiffness;

[0133] The axial stiffness is used to ensure the stable advancement of the robotic arm during the assembly process;

[0134] The radial stiffness allows the robotic arm to adjust its position when encountering assembly deviations to avoid jamming.

[0135] The abnormal force includes jamming and / or uneven assembly force;

[0136] Step 6: Determine whether the pin is subjected to an abnormal force after detecting the contact state in the current time period. If so, go to Step 7; if not, go to Step 8;

[0137] Step 7: Perform adaptive adjustment of the impedance parameters of the robotic arm in the current time period to obtain the adjusted robotic arm in the current time period, and go to Step 8;

[0138] Optionally, the specific steps for determining whether the pin is subjected to an abnormal force in the current time period include:

[0139] Determine whether the change rate of the force received by the six-axis force sensor of the pin in the current time period exceeds the change rate threshold. If so, it is an abnormal force, and increase the damping of the robotic arm in the current time period to obtain the adjusted damping; if not, it is not subjected to an abnormal force;

[0140] At the same time, when it is determined that the surface roughness of the workpiece to be assembled in the current time period is high or the contact force fluctuates greatly, if so, reduce the stiffness of the robotic arm in the current time period to enhance the adaptability of the robotic arm to the complex environment, and ensure that the robotic arm can still maintain a stable and compliant assembly process when the force changes caused by the workpiece position deviation or external interference, and obtain the adjusted stiffness; if not, it means that it is not subjected to an abnormal force;

[0141] Furthermore, the adjusted damping B d and the adjusted stiffness K d , the expressions are respectively:

[0142]

[0143] K d = K0 - β||F ext - F th ||

[0144] Among them, B0 is the reference damping, K0 is the reference stiffness, F th is the set threshold, α is the online adjustment coefficient one, β is the online adjustment coefficient two, and the damping and stiffness are dynamically adjusted according to the external force change rate and the actual force condition.

[0145] Optionally, the workpiece surface characteristics include:

[0146] Surface roughness: At the initial stage of contact, monitor the fluctuations of the normal force and the contact force. If there are high-frequency vibrations in the force signal, it may indicate surface roughness;

[0147] Friction characteristics: Analyze the change rate of the tangential force.

[0148] Step 8: Insert the pin that detects abnormal force in the current time period into the workpiece to be assembled, and determine whether there is a lateral force. If there is, based on the impedance control law, reduce the stiffness parameter, adjust the horizontal position of the pin in the current time period, and enter Step 9; if not, enter Step 9;

[0149] Step 9: Maintain the force in the insertion direction of the pin in the current time period to ensure that the pin smoothly enters the workpiece to be assembled, and enter Step 10;

[0150] Step 10: Maintain the force in the insertion direction of the pin in the current time period, and continuously monitor the force and displacement until a signal indicating the completion of assembly is detected.

[0151] In the dynamic equation of the robotic arm of the present invention, a dynamic compensation mechanism is introduced to offset the internal interferences such as the inertial force, gravity, and joint friction of the robotic arm itself, improving the control accuracy of the robotic arm.

[0152] The compensation torque τ in the present invention c is used to offset the interferences caused by gravity, inertia, and friction, and is superimposed on the feedback control as a feedforward signal. The corresponding joint desired angles, desired velocities, and desired accelerations are calculated through the inverse kinematics algorithm. The calculated desired angles, velocities, and accelerations are substituted into the dynamic equation of the robotic arm to calculate the compensation torque. This torque precisely offsets the internal interferences such as the inertial force, gravity, and joint friction of the robotic arm itself. The compensation torque is used as a feedforward control signal, and the control parameters are dynamically adjusted according to the force feedback information to more accurately track the desired trajectory. In a complex dynamic environment, the system can achieve high-precision end motion control, improving the stability and adaptability of the assembly process.

[0153] In response to the uncertainties in a dynamic environment, the robotic arm can quickly adapt to small changes in the position or posture of the workpiece through real-time force feedback and position adjustment. When the position of the workpiece shifts, the robotic arm can dynamically adjust its motion trajectory and combine force control strategies to achieve adaptive assembly, ensuring the stability and reliability of the assembly process. By introducing an adaptive control algorithm, the robotic arm can dynamically adjust impedance parameters based on real-time force feedback to cope with differences in the materials, shapes, and assembly conditions of different workpieces, further improving the consistency and efficiency of assembly.

[0154] As described above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. An assembling method of an adaptive interference pin assembling device, characterized in that Including: Step 1: Establish the dynamic equation of the robotic arm; Step 2: Control each finger (31) to pick up the pin; Step 3: In the current time period, move the three-jaw centering fixture (3) after picking up the pin above the position to be assembled; Collect the force state and torque state of the pin in the current time period through the six-axis force sensor (2); Step 4: Control the pin in the current time period to contact the workpiece to be assembled, and detect whether it is in a normal contact state. If not, adjust the impedance control law of the three-jaw centering fixture (3) and enter Step 5; if so, enter Step 5; Step 5: Judge whether the pin after the contact state detection in the current time period is subjected to abnormal force. If so, perform adaptive adjustment of the impedance parameters of the robotic arm in the current time period and enter Step 6; if not, enter Step 6; Step 6: Insert the pin after the abnormal force detection in the current time period into the workpiece to be assembled, and judge whether there is a lateral force. If there is, adjust based on the impedance control law and enter Step 7; if not, enter Step 7; Step 7: Maintain the force in the insertion direction of the pin in the current time period to ensure that the pin smoothly enters the workpiece to be assembled.

2. The assembling method of the self-adaptive interference pin assembling device according to claim 1, characterized in that The specific steps of Step 3 include: Based on inverse kinematics and the position to be assembled, obtain the desired motion states of the joints of the robotic arm in the current time period; substitute the desired motion states of the joints of the robotic arm in the current time period into the dynamic equation of the robotic arm to obtain the compensation torque of each joint in the current time period; Based on the compensation torque of each joint in the current time period, adjust the joint angles of each joint of the robotic arm in the current time period to move the three-jaw centering fixture after picking up the pin above the position to be assembled.

3. The assembly method of the adaptive interference pin assembly device according to claim 1, characterized in that The dynamic equation of the robotic arm has the expression: where M(.) is the mass matrix, C(.) is the Coriolis and centrifugal force terms, g(.) is the gravity vector, τ is the joint torque, τ ext is the external disturbance joint torque, q is the joint angle, is the joint angular acceleration, is the joint angular velocity.

4. The assembly method of the adaptive interference pin assembly device according to claim 1, characterized in that, The impedance control law has the expression: where, F ext is the external force, M d is the desired inertia matrix of the fixture, B d is the desired damping matrix of the fixture, K d is the desired stiffness matrix of the fixture, x is the actual position of the fixture, is the actual velocity of the fixture, is the actual acceleration of the fixture, x d is the desired position of the fixture, is the desired velocity of the fixture, is the desired acceleration of the fixture.

5. The assembling method of the self-adaptive interference pin assembling device according to claim 1, characterized in that, The abnormal force includes jamming and / or uneven assembly force.

6. The assembling method of the self-adaptive interference pin assembling device according to claim 5, characterized in that The specific steps of judging whether the pin is subjected to abnormal force in the current time period include: Judge the force change rate of the pin received by the six-axis force sensor in the current time period and the surface roughness or contact force fluctuation of the workpiece to be assembled in the current time period.

7. An adaptive interference pin assembly device, characterized in that, Including: A robotic arm (1), a six-axis force sensor (2) and a three-jaw centering fixture (3); One end of the robotic arm (1) is set on the operation table, and the other end can move in three-dimensional space; The other end of the robotic arm (1) is connected to the six-axis sensor (2); the six-axis sensor (2) is also connected to the three-jaw centering fixture (3).

8. The self-adaptive interference pin assembly device according to claim 7, characterized in that, The three-jaw centering fixture (3) includes a plurality of fingers (31), a plurality of sliders (32), a top plate (33), a plurality of connecting rods (34) and a turntable (35); The top plate (33) is respectively connected to a plurality of fingers (31) and a plurality of sliders (32); the plurality of connecting rods are respectively connected to the plurality of sliders and the turntable (35); One end of each connecting rod is connected to the turntable, and the other end is connected to each corresponding slider; Each slider is also respectively connected to the corresponding finger (31); each slider is also respectively connected to the corresponding finger (31); The connecting rod is used to convert the tangential motion of the turntable into the radial motion of the slider; One end of each connecting rod is connected to the turntable, and the other end is connected to each corresponding slider.

9. The self-adaptive interference pin assembly device according to claim 8, characterized in that The extension lines of the symmetry axes of each slider and each finger pass through the center point of the top plate; The extension lines of the symmetry axes of each connecting rod pass through the center point of the turntable.

10. The adaptive interference pin assembly device according to claim 8, characterized in that, The geometric center of the clamping surface of each finger is located on the extension line of the central axis of the three-jaw centering fixture.

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