An adaptive pin interference assembly device and method

Abstract

The present application relates to a kind of self-adapting pin interference assembly device and assembly method, belong to intelligent manufacturing and robot technical field, the present application designs three-jaw centering fixture, wherein carousel and three connecting rods are connected, three connecting rods are synchronous motion around carousel center point respectively, connecting rod is transferred to the rotating action of carousel to slider, and slider is moved towards the direction of the center point of top plate or away from the center point of top plate;The movement of each slider drives the opening and closing of each finger, and the opening and closing of each gripper always keeps the center of top plate aligned with pin, can adjust holding force, and ensure that pin is positioned at the center position, provide high repeat positioning accuracy;The present application installs six-dimensional force sensor at the end of mechanical arm, realizes force tracking to assembly process;Moreover, the present application uses impedance control law in assembly process, realizes pin compliant assembly.

Description

Technical Field

[0001] This invention relates to the fields of intelligent manufacturing and robotics, specifically to an adaptive pin interference fit assembly device and assembly method. Background Technology

[0002] In the fields of mechanical manufacturing and industrial production, pin interference fit is a process that achieves a tight connection through the elastic deformation of materials. It is widely used in automobile, electronics, aerospace and precision machinery manufacturing. Its assembly quality directly affects the product positioning accuracy, load transfer efficiency and service life. However, the pin interference fit technology in the present technology still has the following prominent problems in practical applications: (I) Limitations of manual assembly: (1) Unreliable contact force control. In the present technology, manual assembly relies on the operator to manually knock or press the pin, which cannot accurately control the contact force between the pin and the pin hole during the assembly process. Excessive impact force may cause deformation of the pin or base material, surface damage, or even micro-cracks; insufficient force may not guarantee interference, resulting in loose fit; (2) Insufficient efficiency and consistency. The rhythm of manual assembly depends on the operator's skill level, which is difficult to meet the needs of modern industry for high-speed production; (II) Insufficient flexibility of fixed automated equipment: (1) Lack of adaptive adjustment capability. Existing fixed automated assembly equipment (such as hydraulic presses and pneumatic presses) usually use preset parameters (such as pressure, stroke, and speed) to complete the assembly, 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, making it difficult to quickly switch to adapt to pins of 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 size deviation of the hole or pin exceeds ±0.01mm, the equipment will not be able to complete the assembly or will cause the fit to fail. This forces companies to invest heavily in high-precision machining (such as CNC precision boring), limiting the feasibility of small-batch, low-cost production. (III) Challenges of dynamic working conditions and maintenance: (1) Insufficient long-term reliability: Under long-term vibration, impact, or temperature change, the traditional interference fit pins are prone to loosening due to material creep or fretting wear; (2) Difficult maintenance and replacement: When disassembling interference fit pins, special tools (such as heaters or pullers) are required, which is complicated and easily damages the substrate. The existing pin interference fit method has obvious shortcomings: manual assembly cannot adaptively control the contact force, resulting in low efficiency and poor consistency; while fixed automated equipment has problems such as insufficient flexibility and poor adaptability, which cannot meet the flexible production needs of multiple varieties and small batches. Summary of the Invention

[0003] In view of the above problems, the present invention provides an adaptive pin interference fit assembly device and assembly method. The present invention designs a three-jaw centering fixture, wherein a turntable is connected to three connecting rods. The three connecting rods move synchronously around the center point of the turntable. The connecting rods transmit the rotational motion of the turntable to the sliders, and push the sliders 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 gripper finger. The opening and closing of each gripper finger always keeps the center of the top plate aligned with the pin. The clamping force can be adjusted, and the pin is positioned in the center position, providing high repeatability and positioning accuracy. The present invention installs a six-dimensional force sensor at the end of the robotic arm to achieve force tracking during the assembly process. Moreover, the present invention uses an impedance control law during the assembly process to achieve compliant pin assembly.

[0004] This invention provides an assembly method for an adaptive pin interference fit device, comprising: Step 1: Establish the dynamic equations of the robotic arm; Step 2: Control each gripper finger to pick up the pin; Step 3: Move the three-jaw centering jig that has gripped the pin in the current time period to above the position to be assembled; The force and torque status of the pin are collected during the current time period using a six-dimensional force sensor. Step 4: Control the pin to contact the workpiece to be assembled during the current time period, and check whether it is in a normal contact state. If not, adjust the impedance control law of the three-jaw centering fixture and proceed to step 5; if yes, proceed to step 5. Step 5: Determine whether the pin after the contact status detection in the current time period is subjected to abnormal force. If yes, adjust the impedance parameters of the robot arm in the current time period adaptively and proceed to step 6; otherwise, proceed to step 6. Step 6: Insert the pin detected by the abnormal force in the current time period into the workpiece to be assembled, and determine whether there is a lateral force. If there is, adjust according to the impedance control law and proceed to step 7; if not, proceed to step 7. Step 7: Maintain the force in the current time period of the pin insertion direction to ensure that the pin smoothly enters the workpiece to be assembled.

[0005] Optionally, step 3 includes the following specific steps: Based on inverse kinematics and the position to be assembled, the desired motion state of each joint of the robotic arm in the current time period is obtained; the desired motion state of each joint of the robotic arm in the current time period is substituted 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 angle of each joint of the robotic arm in the current time period, so that the three-jaw centering jig after picking up the pin in the current time period moves to above the position to be assembled.

[0006] Optionally, the dynamic equation of the robotic arm is expressed as:

[0007] in, It is a quality matrix. It refers to the Coriolis force and centrifugal force terms. It is the gravity vector. It is joint torque. It is an external disturbance joint torque. This refers to the joint position. Joint angular acceleration, This represents the joint angular velocity.

[0008] Optionally, the impedance control law is expressed as:

[0009] in, It is an external force. It is the expected inertia matrix of the fixture. It is the expected damping matrix of the clamp. It is the desired stiffness matrix of the fixture. It is the actual position of the fixture. It is the actual speed of the fixture. It is the actual acceleration of the clamp. It is the desired position of the fixture. It is the desired speed of the fixture. It is the desired acceleration of the fixture.

[0010] Optionally, the abnormal force includes jamming and / or uneven assembly forces.

[0011] Optionally, the specific steps for determining whether the pin has been subjected to abnormal force during the current time period include: The force change rate of the pin and the surface roughness or contact force fluctuation of the workpiece to be assembled are judged based on the data received by the six-dimensional force sensor during the current time period.

[0012] Another object of the present invention is to provide an adaptive pin interference fit device, comprising: Robotic arm, six-dimensional force sensor and three-jaw centering fixture; One end of the robotic arm is mounted on the operating table, and the other end can move in three-dimensional space; The other end of the robotic arm is connected to a six-dimensional force sensor; the six-dimensional force sensor is also connected to a three-jaw centering fixture.

[0013] Optionally, the three-jaw centering fixture includes multiple gripping fingers, multiple sliders, a top plate, multiple connecting rods, and a turntable; The top plate is connected to multiple grippers and multiple sliders respectively; the multiple connecting rods are connected to multiple sliders and turntables respectively; One end of each connecting rod is connected to the turntable, and the other end is connected to the corresponding slider. Each slider is also connected to a corresponding gripper finger; each slider is also connected to a corresponding gripper finger. 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 the corresponding slider.

[0014] Optionally, the extension lines of the symmetry axes of each slider and each gripper finger all pass through the center point of the top plate; The extension lines of the axes of symmetry of each link all pass through the center point of the turntable.

[0015] Optionally, the geometric center of the gripping surface of each gripper finger is located on the extension line of the central axis of the three-jaw centering fixture.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention installs a six-dimensional force sensor at the end of the robotic arm to realize force tracking during the assembly process; (2) The three-jaw centering fixture designed in this invention can adjust the clamping force and ensure that the pin is positioned in the center position, providing high repeatability positioning accuracy; (3) The present invention uses impedance control during the assembly process to achieve compliant assembly of the pins. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] Figure 1 This is a schematic diagram of the flowchart of the adaptive pin interference fit method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a portion of the structure of the adaptive pin interference fit assembly device in an embodiment of the present invention; Figure 3 This is a schematic exploded view of the adaptive pin interference fit assembly device in an embodiment of the present invention; Figure 4 This is a schematic diagram of the isometric view of the three-jaw centering fixture in an embodiment of the present invention; Figure 5 The explosion of the three-jaw centering clamp in the embodiment of the present invention Figure 1 ; Figure 6 This is a schematic top view of the three-jaw centering fixture when the turntable rotates in an embodiment of the present invention; Figure 7 This is a schematic top view of the three-jaw centering fixture when the turntable is stationary in an embodiment of the present invention; Figure 8The explosion of the three-jaw centering clamp in the embodiment of the present invention Figure 2 .

[0019] Figure label: 1. Robotic arm, 2. Six-dimensional force sensor, 3. Three-jaw centering fixture, 3. Gripping finger, 31. Slider, 32. Top plate, 33. Connecting rod, 34. Turntable, 35. Copper column, 36. Mounting plate, 37. Motor, 38. Bracket, 39. Base plate, 40. Center hole, 37-1. Groove, 33-1. Fingertip, 31-1. Connecting plate, 31-2. Detailed Implementation

[0020] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0021] A specific embodiment of the present invention, such as Figure 1-8 An adaptive pin interference fit assembly device is disclosed, comprising: a robotic arm 1, a six-dimensional force sensor 2, and a three-jaw centering fixture 3; One end of the robotic arm 1 is set on the operating table, and the other end can move in three-dimensional space; The other end of the robotic arm 1 is connected to a six-dimensional force sensor 2; the six-dimensional force sensor 2 is also connected to a three-jaw centering fixture 3; Optionally, the three-jaw centering fixture 3 includes multiple gripping fingers 31, multiple sliders 32, a top plate 33, multiple connecting rods 34, a turntable 35, and a motor 38; The top plate 33 is connected to multiple gripper fingers 31 and multiple sliders 32 respectively; the multiple connecting rods are connected to multiple sliders and turntable 35 respectively; the turntable 35 is also connected to a motor 38; The connecting rod is used to convert the tangential motion of the turntable into the radial motion of the slider.

[0022] Furthermore, one end of each connecting rod is connected to the turntable, and the other end is connected to the corresponding slider. Each slider is also connected to its corresponding gripper finger 31; Optionally, the three-jaw centering fixture 3 also includes multiple copper pillars 36, a mounting plate 37, a bracket 39, and a base plate 40; The motor 38 is connected to the base plate 40 and the mounting plate 37 respectively via the bracket 39; the motor shaft 38-1 of the motor 38 passes through the center hole 37-1 of the mounting plate 37 and is connected to the turntable 35 for torque transmission; the base plate 40 is connected to the six-dimensional force sensor 2 via a standard flange. The mounting plate 37 and the top plate 33 are connected by multiple copper pillars 36 to ensure that the turntable 35 and multiple connecting rods 34 can rotate smoothly in the space between the mounting plate 37 and the top plate 33.

[0023] Optionally, the center points of the top plate 33, the turntable 35 and the mounting plate 37 are all located on the center extension line of the three-jaw centering fixture; Optionally, the top plate 33 is provided with a plurality of grooves 33-1; Each slider 32 is respectively disposed in the corresponding groove 33-1 and is movably connected to the corresponding groove 33-1; Each slider 32 controls the corresponding gripper 31 to move radially around the center point of the top plate in each groove 33-1, thereby realizing the opening and closing action of each gripper 31. Optionally, each of the finger clips 31 includes a fingertip 31-1 and a connecting plate 31-2; Each connecting plate is connected to the corresponding slider and each fingertip.

[0024] Optionally, the extension lines of the symmetry axes of each slider and each gripper finger all pass through the center point of the top plate; The extension lines of the axes of symmetry of each link all pass through the center point of the turntable; Optionally, the geometric center of the gripping surface of each gripper finger is located on the extension line of the central axis of the three-jaw centering fixture; Each of the gripping fingers is arranged at equal intervals around the center of the top plate; wherein, each pair of gripping fingers is symmetrically distributed along the center point of the turntable; Optionally, the connecting rods are arranged at equal intervals around the center of the turntable; wherein, the connecting rods are evenly distributed along the center point of the turntable; The grooves and sliders are evenly spaced around the center of the top plate; wherein the grooves and sliders are evenly distributed along the center point of the top plate. For example, the included angle between the connection points of the two connecting rods at turntable 35 is 120°; The included angle between each pair of grooves and each pair of sliders on the top plate is 120°. The angle between the two fingers on the top plate is 120°; When the turntable 35 rotates, one end of each link simultaneously makes a circular motion around the center point of the turntable; optionally, the size and shape of each link 34 are the same. The dimensions and shapes of each slider are consistent; the dimensions and shapes of each groove are consistent. In one embodiment of the present invention, when the turntable 35 is stationary, the extension lines of the symmetry axes of each link all pass through the center of the turntable, at which time the clamp opens and closes to its maximum. When the turntable rotates, one end of each link rotates along with the turntable, and the extension of the axis of symmetry of each link does not pass through the center of the turntable; This invention designs a 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 the same distance toward or away from the center point of the top plate. At the same time, three grooves are designed to limit the three sliders to move radially along the three grooves pointing to the center point of the top plate. Furthermore, each gripper 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. Each gripper finger moves linearly around the center point of the top plate along the extension line of its respective axis of symmetry, and the movement distance of the three grippers is always equal relative to the center point of the top plate.

[0025] 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 with the turntable, causing the extension line of the axis of symmetry of each connecting rod 34 to move 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 causing each gripper finger 31 to open; subsequently, the motor shaft 38-1 drives the turntable 35 to rotate in the opposite direction, causing the extension line of the axis of symmetry of each connecting rod 34 to move closer to the center point of the turntable, and the other end of each connecting rod pushes each slider to slide closer to the center point of the top plate, causing the clamp to close and realizing the clamping action.

[0026] In this 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 the corresponding sliders 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 gripping process.

[0027] In this invention, the turntable 35 is connected to three connecting rods 34. The three connecting rods move synchronously around the center point of the turntable. The connecting rods 34 transmit the rotation of the turntable to the slider 32 and push the slider to move toward or away from the center point of the top plate. The movement of each slider drives the opening and closing of each gripper finger 31. The opening and closing of each gripper finger always keeps the center of the top plate aligned with the pin, that is, always keeps the pin on the extended line of the central axis of the three-jaw centering fixture.

[0028] In this invention, the movement of the three sliders all originates from the rotation of the turntable 35. The initial driving action received by each slider is completely synchronized. The turntable, as the only power input point, ensures the simultaneity of the movement.

[0029] In this invention, the sliders driven by each link are constrained in symmetrically distributed radial grooves; When the turntable rotates at a certain angle, the magnitude and direction of the radial tension generated by each link on its connected slider are exactly the same. The slider is constrained to move within the corresponding groove to prevent deviation.

[0030] Another object of the present invention is to provide a method of using an adaptive pin interference fit device, comprising: Step 1: Establish the dynamic equations of the robotic arm; Step 2: Robotic arm 1 acquires the angles of each joint of the robotic arm in the current time period; Adjust the angles of each joint of the robotic arm 1 during the current time period, move the three-jaw centering fixture 3 above the pin tray, and control the fixture 3 to pick up the pin based on the control torque of the robotic arm 1, while keeping the pin position at the center point of the top plate. Understandably, the pin is always kept at the center of the top plate during the gripping process; each gripping finger opens or closes during the gripping process to achieve self-centering of the pin's position.

[0031] Optionally, the clamping force is adjusted by the clamping force estimated by the motor current feedback to keep the clamping force within a suitable range and avoid the clamping force being too large or too small. For example, the motor current feedback provides information about the motor load. The motor current is directly related to the torque. The larger the current value, the larger the torque and the stronger the clamping force. The clamping force can be controlled by adjusting the motor current. The motor adjusts the clamping force of the fingers by controlling the torque of the turntable 35.

[0032] Step 3: Based on inverse kinematics and the position to be assembled, obtain the desired motion state of each joint of the robot arm in the current time period; substitute the desired motion state of each joint of the robot arm in the current time period into the dynamic equation of the robot arm to obtain the compensation torque of each joint in the current time period. By using the compensation torque of each joint in the current time period for feedforward control, the joints of the robotic arm are driven to move the three-jaw centering fixture 3, which has gripped the pin in the current time period, quickly to the position above the assembly position. The force and torque states of the pin during the current time period are collected by the six-dimensional force sensor 2. Optionally, the dynamic equation of the robotic arm is expressed as:

[0033] in, It is the mass matrix of the joint. It refers to the Coriolis force and centrifugal force of the joint. It is the gravity vector of the joint. It is joint torque. It is an external disturbance joint torque. Joint angular acceleration, The joint angular velocity, This refers to the joint angle.

[0034] Optionally, the desired motion state includes a desired angle. Expected speed and expected acceleration ; Optionally, the compensating torque of each joint The expression is:

[0035] in, To compensate for the torque, From the perspective of expectation, The desired speed.

[0036] Optionally, the state of the force and torque includes the location, magnitude, and direction of the force; and the location, magnitude, and direction of the torque. Optionally, the data collected by the six-dimensional force sensor is transmitted to the control cabinet in real time via the Modbus 485 protocol and saved to the database; When the robotic arm uses a gripper to pick up the pin, a six-dimensional force sensor measures the contact force and torque between the pin and the gripper. When the gripper of the robotic arm approaches the workpiece to be assembled, the six-dimensional force sensor measures the reaction force and torque of the workpiece on the robotic arm.

[0037] Furthermore, the data collected by the six-dimensional force sensor includes: Force along the X-axis, force along the Y-axis, force along the Z-axis, torque about the X-axis, torque about the Y-axis, and torque about the Z-axis; Step 4: Control the pin to contact the workpiece to be assembled during the current time period, detect the contact status between the pin and the workpiece to be assembled during the current time period, and determine whether it is a normal contact status. If not, proceed to step 5. If so, proceed to step 6; Step 5: Adjust the impedance control law of the three-jaw centering fixture according to the force and torque state of the pin in the current time period to obtain the updated force and torque state of the pin in the current time period, which will be used as the force and torque state of the pin in the next time period. Proceed to Step 6. Optionally, step 4, determining whether a contact is in a normal state, includes the following steps: The force and torque status information of the pin in the current time period is obtained by a six-dimensional force sensor and compared with the normal contact status information stored in the database. If the force of the pin in the current time period exceeds the normal contact status threshold, the pin in the current time period is in an abnormal contact state, indicating that the pin is in contact with the hole wall or other problems have occurred. If the force of the pin in the current time period does not exceed the normal contact status threshold, the current time period is in a normal contact state. Optionally, when the pin is not in contact with the workpiece to be assembled, the stiffness of the three-jaw centering fixture 3 is increased to ensure alignment with the desired position. Movement, maintaining accurate trajectory tracking; Optionally, the specific steps for adjusting the impedance control law of the three-jaw centering fixture based on the force and torque state of the pin during the current time period include: When the pin comes into contact with the workpiece to be assembled, and the pin is subjected to radial force and / or frictional force; Reduce the radial stiffness of the robotic arm in the current time period and make slight adjustments to the left and right sides of the robotic arm so that the pin is aligned with the hole; the radial stiffness includes the stiffness in the left and right directions and the front and back directions. Increase the damping of the robotic arm during the current time period; Maintain the current high axial stiffness of the robotic arm to ensure continued force to advance the pin; the axial stiffness includes stiffness in the vertical direction; Optionally, step 4 also includes establishing an impedance control law, the specific steps of which include: The relationship between the motion of the three-jaw centering clamp and the external force is modeled as a spring-damped-mass system. Based on this system, the impedance relationship between the motion of the clamping fingers and the external force is established, yielding the impedance control law, expressed as:

[0038] in, It is an external force, the reaction force of the environment on the three-jaw centering clamp, including contact force and friction force, which is measured by a six-dimensional force sensor. It is the expected inertia matrix of the fixture. It is the expected damping matrix of the clamp. It is the desired stiffness matrix of the fixture. It is the actual position of the fixture. It is the actual speed of the fixture. It is the actual acceleration of the clamp. It is the desired position of the fixture. It is the desired speed of the fixture. It is the desired acceleration of the fixture.

[0039] It is understood that the workpiece to be assembled is the assembly hole or surface of a pin; Optionally, the initial axial stiffness and initial radial stiffness of the robotic arm are set according to the pin interference range; The axial stiffness is greater than the radial stiffness; Axial stiffness is used to ensure stable advancement of the robotic arm during assembly; Radial stiffness allows the robotic arm to adjust its position when encountering assembly deviations, preventing jamming.

[0040] The abnormal forces include jamming and / or uneven assembly forces; Step 6: Determine whether the pin has been subjected to abnormal force after the contact status detection was completed in the current time period. If yes, proceed to step 7; otherwise, proceed to step 8. Step 7: Adaptively adjust the impedance parameters of the robotic arm for the current time period to obtain the adjusted robotic arm for the current time period, and proceed to Step 8; Optionally, the specific steps for determining whether the pin has been subjected to abnormal force during the current time period include: Determine whether the rate of change of force on the pin received by the six-dimensional force sensor in the current time period exceeds the rate of change threshold. If so, it is an abnormal force, and the damping of the robot arm in the current time period is increased to obtain the adjusted damping; if not, it is not subjected to an abnormal force. At the same time, if it is determined that the surface roughness of the workpiece to be assembled is high or the contact force fluctuates greatly during the current time period, the stiffness of the robotic arm during the current time period will be reduced to enhance the adaptability of the robotic arm to complex environments. This will ensure that the robotic arm can still maintain a stable and smooth assembly process and obtain the adjusted stiffness when the workpiece position is deviated or the force changes are caused by external interference. If not, it means that there is no abnormal force. Furthermore, the adjusted damping and adjusted stiffness The expressions are as follows:

[0041]

[0042] in, It is the reference damping. It is the reference stiffness. It is about setting a threshold. The online adjustment coefficient is one. The online adjustment coefficient is two, which dynamically adjusts the damping and stiffness based on the rate of change of external force and the actual stress conditions.

[0043] Optionally, the workpiece surface characteristics include: Surface roughness: In the initial stage of contact, monitor the fluctuation of normal force and contact force. If the force signal has high-frequency vibration, it may indicate surface roughness. Friction characteristics: Analysis of the rate of change of tangential force.

[0044] Step 8: Insert the pin that detected abnormal force in the current time period into the workpiece to be assembled, and determine whether there is a lateral force. If there is, reduce the stiffness parameter based on the impedance control law, adjust the horizontal position of the pin in the current time period, and proceed to step 9; if there is no force, proceed to step 9. Step 9: Maintain the force in the current time period of the pin insertion direction to ensure that the pin enters the workpiece to be assembled smoothly, and proceed to step 10; Step 10: Maintain the force in the direction of pin insertion during the current time period, and continuously monitor the force and displacement until a signal indicating that assembly is complete is detected.

[0045] The dynamics equation of the robotic arm of this invention introduces a dynamic compensation mechanism to counteract the inherent interferences such as the robotic arm's own inertial force, gravity, and joint friction, thereby improving the control accuracy of the robotic arm.

[0046] Compensating torque in this invention This system is used to counteract interference caused by gravity, inertia, and friction, and is superimposed as a feedforward signal into the feedback control. The corresponding desired joint angle, desired velocity, and desired acceleration are calculated using an inverse kinematics algorithm. These calculated angles, velocities, and accelerations are then substituted into the robotic arm's dynamic equations to calculate a compensation torque. This torque precisely counteracts the inherent interference from the robotic arm's own inertial forces, gravity, and joint friction. This compensation torque is used as a feedforward control signal, and control parameters are dynamically adjusted based on force feedback information to more accurately track the desired trajectory. In complex dynamic environments, the system can achieve high-precision end-effector motion control, improving the stability and adaptability of the assembly process.

[0047] To address uncertainties in dynamic environments, robotic arms can quickly adapt to minute changes in workpiece position or orientation through real-time force feedback and position adjustment. When the workpiece position shifts, the robotic arm can dynamically adjust its trajectory, combining force control strategies to achieve adaptive assembly, ensuring the stability and reliability of the assembly process. By introducing adaptive control algorithms, the robotic arm can dynamically adjust impedance parameters based on real-time force feedback to cope with differences in workpiece materials, shapes, and assembly conditions, further improving assembly consistency and efficiency.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection 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 scope of the technology disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. An assembly method for an adaptive pin interference fit device, the adaptive pin interference fit device comprising: A robotic arm (1), a six-dimensional force sensor (2), and a three-jaw centering fixture (3); one end of the robotic arm (1) is set on the operating table, and the other end can move in three-dimensional space; the other end of the robotic arm (1) is connected to the six-dimensional force sensor (2); the six-dimensional force sensor (2) is also connected to the three-jaw centering fixture (3); the three-jaw centering fixture (3) includes multiple gripping fingers (31), characterized in that the assembly method includes: Step 1: Establish the dynamic equations of the robotic arm; Step 2: Control each gripper finger (31) to grip the pin; Step 3: Move the three-jaw centering fixture (3) that has gripped the pin in the current time period to above the position to be assembled; The force and torque states of the pin during the current time period are collected by a six-dimensional force sensor (2); Step 4: Control the pin to contact the workpiece to be assembled during the current time period and check whether it is in a normal contact state. If not, adjust the impedance control law of the three-jaw centering fixture (3) and proceed to step 5; if yes, proceed to step 5. Step 5: Determine whether the pin after the contact status detection in the current time period is subjected to abnormal force. If yes, adjust the impedance parameters of the robot arm in the current time period adaptively and proceed to step 6; otherwise, proceed to step 6. Step 6: Insert the pin detected by the abnormal force in the current time period into the workpiece to be assembled, and determine whether there is a lateral force. If there is, adjust according to the impedance control law and proceed to step 7; if not, proceed to step 7. Step 7: Maintain the force in the current time period of the pin insertion direction to ensure that the pin smoothly enters the workpiece to be assembled; Step 3 includes the following specific steps: Based on inverse kinematics and the position to be assembled, the desired motion state of each joint of the robotic arm in the current time period is obtained; the desired motion state of each joint of the robotic arm in the current time period is substituted into the dynamic equation of the robotic arm to obtain the compensation torque of each joint in the current time period. By using the compensation torque of each joint in the current time period for feedforward control, the robotic arm joints are driven to move the three-jaw centering jig after the pin is picked up in the current time period to the position to be assembled. The dynamic equation of the robotic arm is expressed as follows: in, It is a quality matrix. It refers to the Coriolis force and centrifugal force terms. It is the gravity vector. It is joint torque. It is an external disturbance joint torque. For joint angle, Joint angular acceleration, Joint angular velocity; The impedance control law is expressed as follows: in, It is an external force. It is the expected inertia matrix of the fixture. It is the expected damping matrix of the clamp. It is the desired stiffness matrix of the fixture. It is the actual position of the fixture. It is the actual speed of the fixture. It is the actual acceleration of the clamp. It is the desired position of the fixture. It is the desired speed of the fixture. It is the desired acceleration of the fixture.

2. The assembly method of the adaptive pin interference fit assembly device according to claim 1, characterized in that, The abnormal forces include jamming and / or uneven assembly forces.

3. The assembly method of the adaptive pin interference fit assembly device according to claim 2, characterized in that, The specific steps to determine whether the pin has been subjected to abnormal force in the current time period include: The force change rate of the pin and the surface roughness or contact force fluctuation of the workpiece to be assembled are judged based on the data received by the six-dimensional force sensor during the current time period.

Images