A flexible circuit board assembly special end effector with multi-directional adaptive adjustment function

Abstract

This invention discloses a flexible circuit board assembly end effector with multi-directional adaptive adjustment function and its control method, belonging to the field of electronic manufacturing equipment technology. The end effector includes a lateral motion slide, a flange, a vision recognition system, an encoder, and a controller. The vision recognition system provides the target position setpoint, the encoder provides the actual position feedback value, and a linear extended state observer estimates and compensates for total disturbances such as mechanical friction, flexible support force, and elastic torque in real time. The linear state error feedback control law outputs the displacement increment after disturbance compensation, driving the corresponding motor to complete the sequential adsorption process of adaptive adjustment of the nozzle spacing, vertical adsorption of the first plug, compensation for the position deviation of the unadsorbed plug, and vertical adsorption of the second plug. By combining the end effector structure with a linear active disturbance rejection control algorithm, high-precision sequential adsorption of the two plugs of the flexible circuit board is achieved without repeatedly tuning parameters for flexible circuit boards of different specifications.

Description

Technical Field

[0001] This invention belongs to the field of electronic manufacturing equipment technology, and specifically relates to a special end effector for flexible circuit board assembly with multi-directional adaptive adjustment function. Background Technology

[0002] Flexible printed circuit boards (PCBs) are high-reliability flexible printed circuit boards made with polyimide or polyester film as the substrate. They offer significant advantages such as lightweight design and bendability, and are primarily used to connect various electronic modules such as motherboards, screens, and cameras, enabling stable transmission of electrical energy and various electrical signals. They are widely used in consumer electronics, automotive electronics, aerospace, and other fields. Due to the softness and poor rigidity of the PCB substrate, it is highly susceptible to deformation during external force adsorption, pressing, and alignment. The assembly accuracy of the plug and motherboard socket directly determines the overall electrical performance and mechanical reliability of the device. Misalignment can easily lead to poor contact, short circuits, and other assembly defects. Prolonged use with bending can easily result in wire breakage, signal interruption, and ultimately, device malfunction. Therefore, ensuring precise alignment and locking of the PCB plug and socket is a core prerequisite for improving product yield and service stability, placing extremely high demands on assembly positioning accuracy and operational reliability.

[0003] Currently, the industry commonly uses robots paired with dual-nozzle structures to automate the assembly of flexible circuit boards. Existing equipment uses rigid, fixed-spaced nozzles, which cannot adaptively adjust the spacing. The accompanying control schemes mostly employ traditional cascade PID control. Due to the inherent processing tolerances and accumulated assembly errors of the flexible circuit boards, the spacing between the plugs at both ends varies between different batches and specifications of boards. The rigid, fixed-spaced nozzles cannot adapt to these spacing deviations, leading to a mismatch between the nozzle and plug alignment references. Simultaneously, the suction forces of the two sets of nozzles often differ, resulting in an imbalance of forces on both sides of the board. This can easily cause warping during pickup and misalignment of the plug's suction center point. Subsequent downward insertion further exacerbates the plug misalignment, causing irreversible damage to the flexible circuitry. Furthermore, traditional cascade PID control heavily relies on precise mathematical models and fixed control parameters, neglecting the influence of various unknown disturbances during assembly, such as changes in flexible support force, nozzle contact reaction force, and mechanical friction. It is difficult to quickly compensate for these disturbances, often resulting in positioning overshoot, long stabilization times, or even assembly failure.

[0004] To address the inherent shortcomings of existing rigid, fixed-gap dual-nozzle synchronous adsorption processes and traditional cascade PID control methods, this application proposes a multi-directional adjustable dual-nozzle structure and a sequential adsorption assembly scheme, and constructs an active disturbance rejection control method to replace traditional cascade PID control. This invention, through a dual-nozzle structure with adaptively adjustable spacing and posture, combined with a step-by-step adsorption strategy that first fixes one side of the plug and then compensates for the deviation of the other side's plug, effectively overcomes problems such as poor spacing adaptability of traditional rigid nozzles and uneven force during synchronous adsorption leading to board warping and circuit damage, significantly improving the assembly stability and yield of flexible circuit boards. However, this step-by-step assembly mode introduces new technical challenges: when one side of the plug is adsorbed and pressed down, it exerts pulling and squeezing effects on the flexible board, causing irregular horizontal offset and angular deflection of the unfixed end plug. Since this deformation deviation dynamically changes with the FPC material, thickness, and model specifications, it does not have a fixed variation law and cannot be effectively compensated for through offline calibration. Furthermore, traditional cascade PID control relies on precise models and fixed parameters. Faced with circuit boards of varying flexibility and the dynamic disturbances during assembly, frequent manual parameter tuning is required, resulting in weak anti-disturbance capabilities and poor versatility, making it difficult to meet the demands of flexible, high-precision mass production. Therefore, how to fully combine the structural advantages of multi-directional adjustable dual-nozzle with the dynamic disturbance suppression capabilities of self-disturbance rejection control to effectively compensate for deformation deviations caused by stepwise adsorption, and achieve high-precision, high-reliability, and multi-specification adaptable automated assembly, is a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical problems and provide a flexible circuit board assembly special end effector with multi-directional adaptive adjustment function.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A flexible circuit board assembly special end effector includes: a lateral motion slide, a flange, a vision recognition system, an encoder, and a controller;

[0008] The transverse motion slide is fixed on the flange and is equipped with a slide drive motor. The flange is used to connect the robotic arm.

[0009] The transverse motion slide is equipped with a first suction nozzle module and a second suction nozzle module via a connector. The first suction nozzle module and the second suction nozzle module respectively include a vertical motion control motor and a horizontal rotation control motor. The vertical motion control motor drives the suction nozzle to move up and down, and the horizontal rotation control motor drives the suction nozzle to rotate around a vertical axis. The suction nozzle is used to adsorb the plug of the flexible circuit board.

[0010] The visual recognition system is used to acquire images of the position of the flexible circuit board connector;

[0011] The encoders are respectively installed on the slide drive motor, the vertical motion control motor and the horizontal rotation control motor, and are used to provide real-time feedback of motion information.

[0012] The controller calculates control quantities based on feedback signals from the vision recognition system and the encoder, and drives the slide drive motor, the vertical motion control motor, and the horizontal rotation control motor to operate.

[0013] Furthermore, the two suction nozzle modules have the same structure and are symmetrically arranged on both sides of the transverse motion slide. The transverse motion slide drives the two suction nozzle modules to move relative to each other through a connector, so as to adjust the distance between the two suction nozzles.

[0014] Furthermore, the vertical motion control motor converts the rotational motion into the linear up-and-down motion of the suction nozzle through a cam mechanism.

[0015] Furthermore, the horizontal rotation control motor is a hollow shaft motor, and the suction nozzle is installed through the hollow shaft of the hollow shaft motor.

[0016] The present invention may also include:

[0017] An active disturbance rejection control method for compensating for the sequential adsorption error of dual plugs using a flexible circuit board assembly end effector with multi-directional adaptive adjustment function, comprising the following steps:

[0018] Step 1: Adaptive adjustment of nozzle spacing based on visual feedback: The robotic arm moves the end effector above the flexible circuit board. The visual recognition system collects the spatial position image of the two plugs of the flexible circuit board and calculates the actual distance between the two plugs as the target distance setpoint. The target distance and the actual distance between the two nozzles fed back by the encoder in real time are used as the input of the linear active disturbance rejection controller. The linear active disturbance rejection controller estimates the friction of the slide screw and the load change disturbance in real time through the linear extended state observer. After disturbance compensation by the linear state error feedback control law, it outputs the horizontal displacement increment, which drives the slide drive motor of the transverse motion slide to move, so that the distance between the two nozzles adaptively matches the plug spacing of flexible circuit boards of different specifications.

[0019] Step 2: Vertical compliant adsorption of the first plug considering the flexible contact reaction force: The visual recognition system obtains the vertical distance between the first plug and the corresponding nozzle as the target vertical distance; the target vertical distance and the actual height of the nozzle fed back by the encoder in real time are used as the input of the linear active disturbance rejection controller. The linear expansion state observer estimates the time-varying flexible support force disturbance generated by the transmission friction of the cam mechanism and the contact of the nozzle with the flexible circuit board in real time. After disturbance compensation by the linear state error feedback control law, the vertical displacement increment is output to drive the vertical motion control motor of the corresponding nozzle module to rotate, so that the nozzle moves downward to adsorb the first plug.

[0020] Step 3: Compensation for the angle deviation of the unadsorbed plug based on the linkage torsion of flexible copper wire: After the first plug is adsorbed, the visual recognition system detects the angle deviation of the second unadsorbed plug relative to its original position caused by the deformation of the flexible circuit board. This angle deviation is used as the target angle deviation and is input into the linear active disturbance rejection controller along with the actual rotation angle fed back by the encoder in real time. The linear expansion state observer estimates the elastic torque of the flexible copper wire between the two plugs of the flexible circuit board and the bearing friction disturbance in real time. After disturbance compensation by the linear state error feedback control law, it outputs the angular displacement increment, which drives the horizontal rotation control motor corresponding to the adsorbed first plug to rotate. The torque is transmitted to the second plug through the adsorbed nozzle via the flexible copper wire, so that the second plug returns to its original position without overshoot.

[0021] Step 4: Compensating for Adsorption Pull Disturbance and Vertical Compliant Adsorption of the Second Plug: After the visual recognition system determines that the position of the second plug is without deviation, it obtains the vertical distance between the second plug and the corresponding suction nozzle as the target vertical distance; the target distance and the actual height fed back by the encoder are input into the linear active disturbance rejection controller. The linear expansion state observer estimates in real time the residual elastic pull disturbance after the flexible copper wire is twisted in step 3 and the contact reaction force of the suction nozzle. After disturbance compensation by the linear state error feedback control law, it outputs the vertical displacement increment, drives the corresponding vertical motion control motor to make the suction nozzle move downward to complete the adsorption of the second plug.

[0022] Furthermore, the linear extended state observer in the linear active disturbance rejection controller treats the mechanical friction, changes in flexible support force, and elastic torque of the flexible copper wire generated by the special end effector during the sequential adsorption process as the total system disturbance acting on the corresponding drive motor, performs real-time estimation, and provides dynamic feedforward compensation at the control output.

[0023] Furthermore, in steps 2 and 4, when the nozzle contacts the flexible circuit board plug, the linear expansion state observer detects a sudden change in the flexible support force and automatically reduces the output torque of the vertical motion control motor by the linear state error feedback control law. This, combined with the safety lower limit position protection provided by the encoder feedback, achieves smooth contact between the nozzle and the plug.

[0024] Furthermore, the encoder provides real-time feedback of displacement or angle information of each motor at a frequency of 1 kHz, the visual recognition system acquires plug position images at a frequency of 30 Hz, and the linear expansion state observer performs iterative estimation of the total disturbance at a sampling period of 1 kHz.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention provides a specialized end effector structure designed specifically for the sequential adsorption assembly process of flexible circuit boards. The end effector employs a transverse motion slide table in conjunction with symmetrically arranged dual suction nozzle modules. A slide table drive motor propels the two suction nozzle modules to move relative to each other, enabling active adaptive adjustment of the nozzle spacing. This allows for flexible matching of the actual spacing tolerances between the two connectors of flexible circuit boards of different specifications. Simultaneously, each suction nozzle module independently integrates a vertical motion control motor and a horizontal rotation control motor. The horizontal rotation control motor utilizes a hollow shaft motor structure, with the suction nozzle coaxially passing through its hollow shaft, achieving independent coaxial rotation adjustment after adsorption. This results in a compact structure and decoupled motion. This hardware platform provides a reliable structural foundation for the sequential adsorption process, effectively solving the technical challenge of traditional fixed-spacing or synchronous motion structures failing to compensate for connector position deviations.

[0027] Based on the aforementioned specialized end effector structure, this invention proposes a deeply hardware-coupled active disturbance rejection (ADR) control method to achieve high-precision sequential adsorption of the two plugs on a flexible circuit board. Addressing the inherent challenge in the sequential adsorption process where "adsorbing one plug first causes an uncertain positional shift in the other plug," this method applies a linear ADR control algorithm to four key stages: adaptive adjustment of nozzle spacing, vertical adsorption of the first plug, compensation for the angle deviation of the unadsorbed plug, and vertical adsorption of the second plug. This innovative method integrates the non-contact global positioning of a vision recognition system with the high-frequency local feedback of an encoder. The vision system provides target setpoints (plug spacing, vertical distance, angle deviation), while the encoder provides actual state feedback (actual spacing, height, angle) at a 1kHz frequency. This complementary approach effectively overcomes the shortcomings of high latency in single vision feedback and the inability of a single encoder to perceive absolute position. Furthermore, to address nonlinear disturbances such as flexible circuit board deformation and elastic torque transmission caused by the initial adsorption during sequential adsorption, this method uses an expanded state observer for real-time estimation and dynamic compensation, achieving precise correction of the positional deviation of the unadsorbed plug.

[0028] This invention significantly improves the accuracy and stability of flexible circuit board assembly by deeply coupling the aforementioned special-type end effector structure with a linear active disturbance rejection control algorithm. The extended state observer estimates and dynamically compensates for unknown disturbances such as mechanical friction, flexible support force, and elastic torque in real time, enabling the alignment error to converge to within 0.1 mm with no overshoot and fast response, fully meeting the alignment requirements of high-precision flexible circuit board assembly. Compared to traditional cascade PID control, this invention maintains stable control quality and good assembly consistency even under significant uncertain disturbances.

[0029] This invention has strong process adaptability. The linear active disturbance rejection control algorithm is based on the framework of "total disturbance estimation and compensation". It is not sensitive to the differences in flexibility coefficient, plug spacing and thickness of flexible circuit boards of different specifications. It does not require repeated tuning of control parameters for different product models, which significantly improves the versatility and ease of use of the equipment and is conducive to the needs of rapid changeover of multiple products in flexible production lines.

[0030] This invention features a compliant contact protection function during the adsorption process. The expansion state observer can quickly identify the sudden change in support force at the moment of contact between the nozzle and the flexible circuit board. Based on this, the controller automatically reduces the downward pressure control amount. Combined with the real-time feedback from the encoder and the comparison protection mechanism with the preset safety lower limit (-0.1 mm), this dual protection effectively prevents the plug from deforming and failing due to excessive compression, thus improving the safety of the assembly process and the product yield. Attached Figure Description

[0031] Appendix Figure 1 This is a schematic diagram of the end effector of the present invention;

[0032] Appendix Figure 2 This is a schematic diagram of the installation of the first and second suction nozzle modules of the present invention;

[0033] Appendix Figure 3 It is attached Figure 2 The right view;

[0034] Appendix Figure 4 This is a flowchart of the linear active disturbance rejection control algorithm of the present invention;

[0035] Appendix Figure 5 This is a flowchart illustrating the real-time error adjustment process of the end effector in this invention.

[0036] Appendix Figure 6 This is a simulation curve of the alignment error convergence of the special end effector of this invention;

[0037] Appendix Figure 7 This is a simulation curve of the vertical displacement tracking and disturbance compensation of the suction nozzle of the present invention;

[0038] Appendix Figure 8 This is a simulation curve of the flexible circuit board plug angle calibration of the present invention;

[0039] Appendix Figure 9 This is a simulation curve of the dual-plug highly synergistic adsorption regulation of the present invention.

[0040] In the attached diagram: 1. Vertical motion control motor, 2. Horizontal rotation control motor, 3. Suction nozzle, 4. Lateral motion slide, 5. Flange, 6. Connecting component, 7. Cam mechanism. Detailed Implementation

[0041] The present invention will now be further described with reference to the accompanying drawings.

[0042] This invention provides a flexible circuit board assembly-type end effector, as shown in the attached figure. Figure 1-3 As shown, it includes: a vertical motion control motor 1, a horizontal rotation control motor 2, a suction nozzle 3, a horizontal motion slide 4, a flange 5, and a controller;

[0043] The transverse motion slide 4 is fixed on the flange 5 and is equipped with a slide drive motor. The flange 5 is used to connect the robotic arm.

[0044] The transverse motion slide 4 is equipped with a first suction nozzle module and a second suction nozzle module via a connector 6. The first suction nozzle module and the second suction nozzle module respectively include a vertical motion control motor 1 and a horizontal rotation control motor 2. The vertical motion control motor 1 converts the rotational motion into the linear up-and-down motion of the suction nozzle 3 through a cam mechanism 7. The horizontal rotation control motor 2 drives the suction nozzle 3 to rotate around a vertical axis. The suction nozzle 3 is used to adsorb the plug of the flexible circuit board.

[0045] The visual recognition system is used to acquire images of the position of the flexible circuit board connector;

[0046] The encoders are respectively installed on the slide drive motor, the vertical motion control motor 1 and the horizontal rotation control motor 2, and are used to provide real-time feedback of motion information.

[0047] The controller calculates the control quantity based on the feedback signals from the vision recognition system and the encoder, and drives the slide drive motor, the vertical motion control motor 1, and the horizontal rotation control motor 2 to operate.

[0048] Furthermore, the two suction nozzle modules have the same structure and are symmetrically arranged on both sides of the transverse motion slide 4. The transverse motion slide 4 drives the two suction nozzle modules to move relative to each other through the connector 6, so as to adjust the distance between the two suction nozzles 3.

[0049] The horizontal rotation control motor 2 is a hollow shaft motor, and the suction nozzle 3 is installed through the hollow shaft of the hollow shaft motor.

[0050] Furthermore, the controller incorporates a linear active disturbance rejection control algorithm, which consists of two parts: a linear extended state observer and a linear state error feedback control law. The linear extended state observer takes the actual feedback quantity y and the control quantity u of the system as inputs, and estimates the system state (position, velocity) and total disturbances (including lead screw friction, cam drive friction, flexible circuit board support force, elastic torque, load changes, etc.) in real time. It then compensates the controlled object into a standard integrator-type series form through a disturbance compensation stage. The linear state error feedback control law takes the target setpoint r and the state quantities (position z1, velocity z2) estimated by the linear extended state observer as inputs, calculates the basic control quantity, and outputs the final control quantity, i.e., the displacement increment, after disturbance compensation.

[0051] Furthermore, the tracking differentiator is calculated using the following discrete formula:

[0052]

[0053] In the formula, k is the current sampling time, k+1 is the next sampling time; v1(k) is the transition signal output by the tracking differentiator at time k, and v2(k) is the differentiated signal of the transition signal at time k; f st (·) represents the fastest control synthesis function; r0 is the fast factor; h0 is the filter factor; h is the sampling period; and r(k) is the target position signal input to the visual recognition system.

[0054] Furthermore, the extended state observer is calculated using the following discrete formula:

[0055]

[0056] In the formula, z1(k) is the estimated value of the actual position of the flexible circuit board plug, which is the system output quantity; z2(k) is the estimated value of the derivative of the system output quantity, which is the estimated value of the plug position change rate; z3(k) is the estimated value of the total system disturbance, which includes friction, assembly error and visual recognition delay; y(k) is the position signal fed back by the visual recognition system; u(k) is the control voltage signal output by the controller to the motor; b is the gain coefficient of the controlled object; β1, β2, and β3 are the gain parameters of the extended state observer; and h is the sampling period.

[0057] Furthermore, the linear state error feedback control law is calculated using the following discrete formula:

[0058]

[0059] In the formula, k is the current sampling time; v1(k) and v2(k) are the target position transition signal and its differential signal output by the tracking differentiator, respectively; z1(k) and z2(k) are the actual position and actual velocity of the slide estimated by the extended state observer, respectively; k p k d Here, is the tunable position feedback gain and velocity feedback gain; u0(k) is the base control quantity without disturbance compensation; z3(k) is the total system disturbance estimated by the extended state observer; b is the estimated value of the control channel gain; and u(k) is the control quantity finally output to the motor driver.

[0060] Example 1:

[0061] A method for active disturbance rejection control based on a special end effector assembled on a flexible circuit board, comprising the following steps:

[0062] Step 1: Adaptive Adjustment of Nozzle Spacing: The robotic arm moves the end effector to a preset position above the flexible circuit board. A depth camera mounted on the end effector captures real-time images of the spatial positions of the two connectors on the flexible circuit board. The actual spacing between the two connectors is calculated using a visual recognition algorithm and used as the target spacing setpoint r. Simultaneously, an encoder mounted on the end of the lead screw of the slide module provides real-time feedback of the actual spacing y between the two nozzles at a frequency of 1 kHz. The target spacing r and the actual spacing y are used as input values ​​for the linear active disturbance rejection controller (ADC). The ADC consists of a linear extended state observer and a linear state error feedback control law. The linear extended state observer takes the actual spacing y and the control quantity u as inputs, estimates the system state and total disturbance in real time, and compensates the controlled object into a standard integrator-type cascade form through disturbance compensation. The linear state error feedback control law takes the target spacing r and the state quantity estimated by the linear extended state observer as inputs, and calculates the output quantity after disturbance compensation. The output of the linear active disturbance rejection controller is the horizontal displacement increment Δx. This horizontal displacement increment Δx is converted into the number of pulses of the stepper motor driver through pulse equivalent, which drives the closed-loop stepper motor to rotate the lead screw, so that the distance between the two nozzles converges quickly and smoothly to the target distance, realizing adaptive adjustment of the distance.

[0063] Step 2: Vertical Adsorption of the First Plug: After adjusting the nozzle spacing, the vision recognition system acquires the vertical distance between the first flexible circuit board plug and the corresponding nozzle, which is taken as the target vertical distance r. Simultaneously, the encoder installed on the motor shaft provides real-time feedback on the actual height y of the nozzle at a frequency of 1 kHz. Using the target vertical distance r and the actual height y as inputs to the linear active disturbance rejection controller (ADC), the linear extended state observer uses the actual height y and the control quantity u as inputs to estimate the nozzle's current position, descent speed, and total disturbance (including cam drive friction, flexible circuit board contact reaction force, etc.). The linear state error feedback control law uses the target vertical distance r and the state quantity estimated by the linear extended state observer as inputs, and calculates the output after disturbance compensation. The output of the linear ADC is the vertical displacement increment Δz. This vertical displacement increment Δz is converted into the number of pulses for the stepper motor driver through pulse equivalent, driving the stepper motor connected to the eccentric cam drive mechanism to rotate, causing the nozzle to move downwards to adsorb the first plug. During this process, the encoder provides real-time feedback on the movement distance and compares it with the preset safety lower limit (-0.1mm). When the nozzle movement exceeds the safety lower limit, the control system immediately stops the motor to prevent the nozzle from being pressed down too much, which could cause the flexible circuit board plug to deform and fail due to compression.

[0064] Step 3: Compensation for Position Deviation of Unattached Plugs: After the first plug is attached, the visual recognition system again acquires spatial position images of the two plugs on the flexible circuit board. It determines whether the position of the second unattached plug has changed due to the attachment process of the first plug. If a position change is determined, the visual recognition algorithm detects the angular deviation of the unattached plug relative to its original position, which is taken as the target angular deviation θ1. Simultaneously, the encoder installed on the shaft end of the hollow motor provides real-time feedback of the current actual rotation angle θ2. The target angular deviation θ1 and the actual rotation angle θ2 are used as input values ​​for the linear active disturbance rejection controller. The linear extended state observer takes the actual angle θ2 and the control quantity u as inputs to estimate the current angle, angular velocity, and total disturbance (including the elastic torque of the flexible copper wire, bearing friction, etc.) in real time. The linear state error feedback control law takes the target angular deviation θ2 and the state quantity estimated by the linear extended state observer as inputs, and calculates the output quantity after disturbance compensation. The output of the linear active disturbance rejection controller is the angular displacement increment Δθ. This angular displacement increment Δθ is converted into the number of pulses for the motor driver through pulse equivalent. This drives the 20 hollow motor mounted above the suction nozzle that has already attracted the first plug to directly rotate the nozzle horizontally. The torque is transmitted through the flexible copper wire between the two plugs of the flexible circuit board, causing the second plug to return to its original position. During this process, the encoder provides real-time feedback of the rotation angle information and compares it with the preset safe upper limit of the angle (±5°) to prevent damage to the flexible copper wire of the flexible circuit board due to excessive rotation angle.

[0065] Step 4: Vertical Adsorption of the Second Plug: After the visual recognition system determines that the second plug has no positional change or that positional deviation compensation has been completed, the vertical distance between the second unadsorbed plug and the corresponding nozzle is obtained again through the visual recognition system and taken as the target vertical distance r. Simultaneously, the encoder installed on the motor shaft provides real-time feedback on the actual height y of the nozzle at a frequency of 1kHz. Using the target vertical distance r and the actual height y as input values ​​for the linear active disturbance rejection controller, the linear extended state observer uses the actual height y and the control quantity u as input to estimate the current position, descent speed, and total disturbance (including cam drive friction, flexible circuit board contact reaction force, etc.) of the nozzle in real time. The linear state error feedback control law uses the target vertical distance r and the state quantity estimated by the linear extended state observer as input, and calculates the output quantity after disturbance compensation. The output quantity of the linear active disturbance rejection controller is the vertical displacement increment Δz. This vertical displacement increment Δz is converted into the number of pulses for the stepper motor driver through pulse equivalent, driving the stepper motor connected to the eccentric cam drive mechanism of the corresponding nozzle module to rotate, causing the nozzle to move downwards to adsorb the second plug. During this process, the encoder provides real-time feedback on the movement distance and compares it with the safety lower limit (-0.1mm) to prevent the suction nozzle from deforming and failing due to excessive pressure on the flexible circuit board connector. This completes the sequential adsorption process of the two connectors on the flexible circuit board.

[0066] This embodiment takes an assembly scenario where the distance between the two plugs of a flexible circuit board is 101mm and the initial nozzle distance is 108.88mm as an example to illustrate the specific implementation process of the control method of the present invention.

[0067] (a) Adaptive adjustment of nozzle spacing

[0068] The robotic arm moves the end effector to a preset position above the flexible circuit board. The D435i depth camera mounted on the end effector captures the spatial position images of the two plugs on the flexible circuit board in real time at a frequency of 30Hz. The actual distance between the two plugs is calculated by a visual recognition algorithm and used as the target distance setpoint r=101.0mm. At the same time, the encoder mounted on the end of the lead screw of the slide module provides real-time feedback on the actual distance y between the two suction nozzles at a frequency of 1 kHz, with an initial value of 108.88mm.

[0069] The target spacing *r* and the actual spacing *y* are used as the input values ​​for the linear active disturbance rejection control (ADC) algorithm. In this step, the parameters of the ADC algorithm are set as follows: sampling period *h* = 0.001 seconds, control gain estimate *b0* = 1, controller bandwidth *ωc* = 20 rad / s, and observer bandwidth *ω* = 0.001 rad / s. o =80 rad / s. Therefore, calculate the gain parameters: position feedback gain k. p =ω c ²=400, speed feedback gain k d =2×ω c=40, observer gain β1=3×ω o =240, β2=3×ω o ²=19200, β3=ω o ³=512000.

[0070] Substituting the above parameters into formulas (3) to (5), we obtain the calculation formula for the linear expansion state observer in this step:

[0071]

[0072] The linear expansion state observer iterates in real time using the above formula and outputs three state estimates: z1 is the estimate of the current nozzle spacing, z2 is the estimate of the spacing change rate, and z3 is the real-time estimate of the total disturbance (including lead screw friction, load changes, etc.).

[0073] Substituting the above parameters into formulas (6) and (7), the formula for calculating the linear state error feedback control law in this step is obtained as follows:

[0074]

[0075] The linear state error feedback control law, using the above formula, takes the target distance r(k) and the state estimates z1(k), z2(k), and z3(k) output by the linear extended state observer as inputs to calculate the final control quantity after disturbance compensation, namely the horizontal displacement increment Δx. This horizontal displacement increment Δx is converted into the number of pulses of the stepper motor driver using a pulse equivalent of 0.000313 mm per pulse. This drives the closed-loop stepper motor to rotate the lead screw, causing the distance between the two suction nozzles to gradually converge from the initial value of 108.88 mm to the target value of 101.0 mm, thus achieving adaptive adjustment of the distance.

[0076] Depend on Figure 6 As shown in the simulation curve of the alignment error convergence of the special end effector, the control method in this article can be seen to quickly converge the alignment error to within 0.1mm under the disturbances of lead screw friction and load change, with no overshoot and fast response speed, which verifies the feasibility and effectiveness of the linear active disturbance rejection control algorithm in the high-precision alignment scenario of flexible circuit board assembly.

[0077] (ii) Vertical adsorption of the first plug

[0078] After the nozzle spacing adjustment is completed, the vision recognition system obtains the vertical distance between the first flexible circuit board plug and the corresponding nozzle, which is taken as the target vertical distance r=8.0mm; at the same time, the encoder installed on the shaft end of the vertical motion control motor provides real-time feedback on the actual height y of the nozzle at a frequency of 1kHz, with an initial value of 8.0mm (the nozzle is located 8mm above the plug).

[0079] The target vertical distance *r* and the actual height *y* are used as input values ​​for the linear active disturbance rejection control (ADC) algorithm. In this step, the parameters of the ADC algorithm are set as follows: sampling period *h* = 0.001 s, control gain estimate *b0* = 0.8, and controller bandwidth *ω*. c =8 rad / s, observer bandwidth ω o =32 rad / s. Therefore, calculate the gain parameters: k p =ω c ²=64, k d =2×ω c =16, β1=3×ω o =96, β2=3×ω o ²=3072, β3=ω o ³=32768.

[0080] Substituting the above parameters into formulas (3) to (5), we obtain the calculation formula for the linear expansion state observer in this step:

[0081]

[0082] The linear expansion state observer iterates in real time using the above formula and outputs three state estimates: z1 is the estimate of the current height of the nozzle, z2 is the estimate of the descent speed of the nozzle, and z3 is the real-time estimate of the total disturbance (including cam drive friction, contact reaction force of flexible circuit board, etc.).

[0083] Substituting the above parameters into formulas (6) and (7), the formula for calculating the linear state error feedback control law in this step is obtained as follows:

[0084]

[0085] The linear state error feedback control law, using the above formula, takes the target vertical distance r(k) and the state estimates z1(k), z2(k), and z3(k) output by the linear extended state observer as inputs to calculate the final control quantity after disturbance compensation, namely the vertical displacement increment Δz. This vertical displacement increment Δz is converted into the number of pulses of the stepper motor driver using a pulse equivalent of 0.0225 mm per pulse. This pulse drives the stepper motor connected to the eccentric cam transmission mechanism to rotate, causing the suction nozzle to smoothly descend from a height of 8.0 mm to 0 mm, completing the adsorption of the first plug.

[0086] During this process, the encoder provides real-time feedback on the movement distance and compares it with the preset safety lower limit of -0.1mm. When the nozzle movement exceeds the safety lower limit, the control system immediately stops the motor to prevent the nozzle from pressing down too much and causing the flexible circuit board plug to deform and fail due to compression.

[0087] Depend on Figure 7As shown in the simulation curves of nozzle vertical displacement tracking and disturbance compensation, this control method enables the nozzle's actual vertical displacement to smoothly track the visually given target distance without significant impact or overshoot. When the nozzle contacts the flexible circuit board, the linear expansion state observer quickly identifies and estimates external disturbances such as the flexible support force and motor static friction. The controller synchronously and automatically adjusts the motor output control quantity to reduce the downward driving force, achieving compliant contact. This simulation verifies that this method can effectively prevent damage to the flexible circuit board caused by excessive pressure at the moment of contact.

[0088] (iii) Compensation for positional deviation of the non-adhesive plug

[0089] After successfully attaching the first plug, the visual recognition system again captures images of the spatial positions of the two plugs on the flexible circuit board to determine whether the second, unattached plug has changed position due to the attachment process of the first plug. The detection shows that the second plug has shifted by 0.5 units relative to its original position. 。 The angular deviation is taken as the target angular deviation r=0.5 。 Meanwhile, the encoder installed on the shaft end of the 20 hollow motor provides real-time feedback of the current actual rotation angle y, with an initial value of 0. 。 .

[0090] The target angle deviation *r* and the actual rotation angle *y* are used as the input values ​​for the linear active disturbance rejection control (ADC) algorithm. In this step, the parameters of the ADC algorithm are set as follows: sampling period *h* = 0.001 s, control gain estimate *b0* = 0.8, and controller bandwidth *ω*. c =12 rad / s, observer bandwidth ω o =48 rad / s. Therefore, calculate the gain parameters: k p =ω c ²=144, k d =2×ω c =24, β1=3×ω o =144, β2=3×ω o ²=6912, β3=ω o ³=110592.

[0091] Substituting the above parameters into formulas (3) to (5), we obtain the calculation formula for the linear expansion state observer in this step:

[0092]

[0093] The linear extended state observer calculates in real time using the above formula and outputs three state estimates: z1 is the estimate of the current rotation angle, z2 is the estimate of the rotation angular velocity, and z3 is the real-time estimate of the total disturbance (including the elastic torque of the flexible copper wire, bearing friction, etc.).

[0094] Substituting the above parameters into formulas (6) and (7), the formula for calculating the linear state error feedback control law in this step is obtained as follows:

[0095]

[0096] The linear state error feedback control law, using the above formula, takes the target angular deviation r(k) and the state estimates z1(k), z2(k), and z3(k) output by the linear extended state observer as inputs to calculate the final control quantity after disturbance compensation, namely the angular displacement increment Δθ. This angular displacement increment Δθ is converted into the number of pulses per pulse for the motor driver using a pulse equivalent of 0.1125 degrees per pulse. This drives a 20mm hollow motor to directly rotate the suction nozzle with the first plug already attached horizontally. Torque is transmitted through the flexible copper wire between the two plugs on the flexible circuit board, causing the second plug to rotate 0.5 mm. 。 Return to the original position.

[0097] During this process, the encoder provides real-time feedback of the rotation angle information and compares it with the preset safe upper limit of ±5 degrees to prevent excessive rotation angle from damaging the flexible copper wires of the flexible circuit board.

[0098] Depend on Figure 8 As shown in the simulation curve of the flexible circuit board plug angle calibration, this control method enables the actual rotation angle to smoothly track the visually given target angle without significant overshoot. During the rotation, the linear expansion state observer identifies the elastic torque disturbance generated by the flexible copper wire in real time. The controller dynamically compensates for the disturbance and outputs a smooth motor control quantity to achieve slow rotation linkage, effectively suppressing angle overshoot and verifying the feasibility and stability of this flexible linkage angle calibration method.

[0099] (iv) Vertical adsorption of the second plug

[0100] Once the visual recognition system determines that the second plug has completed position deviation compensation, it again obtains the vertical distance between the second unattached plug and the corresponding suction nozzle through the visual recognition system, which is taken as the target vertical distance r=8.0 mm; at the same time, the encoder installed on the shaft end of the vertical motion control motor provides real-time feedback on the current actual height y of the suction nozzle at a frequency of 1 kHz, with an initial value of 8.0 mm.

[0101] The target vertical distance *r* and the actual height *y* are used as input values ​​for the linear active disturbance rejection control (ADC) algorithm. The parameters of the ADC algorithm in this step are the same as in step (II): sampling period *h* = 0.001 s, control gain estimate *b0* = 0.8, and controller bandwidth *ω*. c =8 rad / s, observer bandwidth ω o =32rad / s, position feedback gain k p =64, speed feedback gain k d=16, observer gain β1=96, β2=3072, β3=32768.

[0102] Substituting the above parameters into formulas (3) to (5), we obtain the calculation formula for the linear expansion state observer in this step:

[0103]

[0104] Substituting the above parameters into formulas (6) and (7), the formula for calculating the linear state error feedback control law in this step is obtained as follows:

[0105]

[0106] The linear state error feedback control law calculates the vertical displacement increment Δz using the above formula. This vertical displacement increment Δz is converted into the number of pulses of the stepper motor driver using the pulse equivalent of 0.0225 mm per pulse. This drives the stepper motor connected to the eccentric cam transmission mechanism of the corresponding nozzle module to rotate, causing the nozzle to drop from a height of 8.0 mm to 0 mm, thus completing the adsorption of the second plug.

[0107] During this process, the encoder provides real-time feedback on the movement distance and compares it with the safety lower limit of -0.1mm to prevent the suction nozzle from deforming and failing due to excessive pressure on the flexible circuit board connector. This completes the sequential adsorption process on the two connectors of the flexible circuit board.

[0108] Depend on Figure 9 As shown in the simulation curve of the vertical adsorption of the second plug, this control method can achieve stable and precise adjustment of the nozzle height based on the visual height deviation. The linear expansion state observer effectively estimates the pulling disturbance generated by the flexible copper wire and compensates for it in real time, so that the second plug can reach the target height smoothly without impact or overshoot, which verifies the feasibility of this dual-plug height coordinated compliant adsorption method.

[0109] This invention uses a linear active disturbance rejection control algorithm to perform closed-loop control on each motor of the end effector. The visual recognition system provides the target position setpoint, the encoder provides the actual position feedback value, and the linear extended state observer estimates and compensates for unknown disturbances such as mechanical friction, flexible support force, and elastic torque in real time. The linear state error feedback control law outputs the displacement increment after disturbance compensation, which ultimately realizes the real-time and precise adjustment of the flexible circuit board plug position, achieving the effect of precise adsorption and precise installation, effectively reducing the assembly defect rate and saving production costs.

[0110] This invention employs a special end effector structure with a transverse slide and a dual-nozzle module. The slide can flexibly adjust the nozzle spacing to accommodate flexible circuit board plugs of different specifications. A 20-core hollow motor directly drives the nozzles to rotate coaxially. The structure is compact, highly reliable, and adaptable to the rapid switching and assembly of multiple models of flexible circuit boards.

[0111] This invention features high-precision anti-disturbance performance. The linear extended state observer estimates the total system disturbance in real time at a frequency of 1 kHz. It treats mechanical friction, changes in flexible support force, and elastic torque as disturbances and compensates them uniformly. Compared with traditional cascade PID control, the alignment error can be converged to within 0.1 mm, with no overshoot and fast response speed, meeting the high-precision assembly alignment requirements of flexible circuit boards.

[0112] This invention has strong adaptability. The linear active disturbance rejection control algorithm includes the differences in flexibility coefficients of flexible circuit boards of different specifications and load changes during assembly into the total disturbance, which is uniformly estimated and compensated by the linear extended state observer. There is no need to repeatedly tune the controller parameters for different models, which significantly improves the versatility and ease of use of the equipment.

[0113] This invention features compliant contact protection. During the adsorption process, the linear expansion state observer can quickly identify the sudden change in support force at the moment of contact between the nozzle and the flexible circuit board. The controller automatically reduces the downward pressure control amount, and with the encoder's safety lower limit protection, the plug is doubly protected from deformation and failure due to excessive squeezing.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible circuit board assembly end effector with multi-directional adaptive adjustment function, characterized in that, include: Lateral motion slide (4), flange (5), vision recognition system, encoder, controller; The transverse motion slide (4) is fixed on the flange (5) and is equipped with a slide drive motor. The flange (5) is used to connect the robotic arm. The transverse motion slide (4) is equipped with a first suction nozzle module and a second suction nozzle module via a connector (6). The first suction nozzle module and the second suction nozzle module respectively include a vertical motion control motor (1) and a horizontal rotation control motor (2). The vertical motion control motor (1) drives the suction nozzle (3) to move up and down, and the horizontal rotation control motor (2) drives the suction nozzle (3) to rotate around the vertical axis. The suction nozzle (3) is used to adsorb the plug of the flexible circuit board. The visual recognition system is used to acquire images of the position of the flexible circuit board connector; The encoders are respectively installed on the slide drive motor, the vertical motion control motor (1) and the horizontal rotation control motor (2) for real-time feedback of motion information; The controller calculates the control quantity based on the feedback signals from the vision recognition system and the encoder, and drives the slide drive motor, the vertical motion control motor (1), and the horizontal rotation control motor (2) to operate.

2. The flexible circuit board assembly end effector with multi-directional adaptive adjustment function according to claim 1, characterized in that, The two suction nozzle modules have the same structure and are symmetrically arranged on both sides of the transverse motion slide (4). The transverse motion slide (4) drives the two suction nozzle modules to move relative to each other through the connector (6) to adjust the distance between the two suction nozzles (3).

3. The flexible circuit board assembly end effector with multi-directional adaptive adjustment function according to claim 1, characterized in that, The vertical motion control motor (1) converts the rotational motion into the linear up-and-down motion of the suction nozzle (3) through the cam mechanism (7).

4. The flexible circuit board assembly end effector with multi-directional adaptive adjustment function according to claim 1, characterized in that, The horizontal rotation control motor (2) is a hollow shaft motor, and the suction nozzle (3) is installed through the hollow shaft of the hollow shaft motor.

5. A self-disturbance rejection control method for compensating for the sequential adsorption error of dual plugs using a flexible circuit board assembly end effector with multi-directional adaptive adjustment function as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Adaptive adjustment of nozzle spacing based on visual feedback: The robotic arm drives the end effector to move above the flexible circuit board. The visual recognition system collects the spatial position image of the two plugs on the flexible circuit board and calculates the actual distance between the two plugs as the target distance setpoint. The target spacing and the actual spacing between the two nozzles fed back by the encoder in real time are used as the input of the linear active disturbance rejection controller. The linear active disturbance rejection controller estimates the friction of the slide screw and the load change disturbance in real time through the linear extended state observer, and outputs the horizontal displacement increment after the disturbance compensation by the linear state error feedback control law, which drives the slide drive motor of the transverse motion slide (4) to move, so that the spacing between the two nozzles adaptively matches the plug spacing of flexible circuit boards of different specifications. Step 2: Considering the flexible contact reaction force, the first plug is vertically and compliantly adsorbed: The visual recognition system obtains the vertical distance between the first plug and the corresponding nozzle as the target vertical distance; the target vertical distance and the actual height of the nozzle fed back by the encoder in real time are used as the input of the linear active disturbance rejection controller. The linear expansion state observer estimates the time-varying flexible support force disturbance generated by the transmission friction of the cam mechanism (7) and the contact of the nozzle with the flexible circuit board in real time. After the disturbance is compensated by the linear state error feedback control law, the vertical displacement increment is output to drive the vertical motion control motor (1) of the corresponding nozzle module to rotate, so that the nozzle (3) moves downward to adsorb the first plug; Step 3: Compensation for angle deviation of unadsorbed plug based on flexible copper wire linkage torsion: After the first plug is adsorbed, the visual recognition system detects the angle deviation of the second unadsorbed plug relative to its original position caused by the deformation of the flexible circuit board. This angle deviation is used as the target angle deviation and is input into the linear active disturbance rejection controller along with the actual rotation angle fed back by the encoder in real time. The linear expansion state observer estimates the elastic torque of the flexible copper wire between the two plugs of the flexible circuit board and the bearing friction disturbance in real time. After the disturbance is compensated by the linear state error feedback control law, the angular displacement increment is output to drive the horizontal rotation control motor (2) corresponding to the adsorbed first plug to rotate. The torque is transmitted to the second plug through the adsorbed nozzle via the flexible copper wire, so that the second plug returns to its original position without overshoot. Step 4: Compensating for the vertical compliant adsorption of the second plug due to the adsorption pull disturbance: After the visual recognition system determines that the position of the second plug is without deviation, it obtains the vertical distance between the second plug and the corresponding nozzle as the target vertical distance; the target distance and the actual height fed back by the encoder are input into the linear active disturbance rejection controller. The linear expansion state observer estimates in real time the residual elastic pull disturbance and nozzle contact reaction force after the flexible copper wire is twisted in step 3. After the disturbance is compensated by the linear state error feedback control law, the vertical displacement increment is output, which drives the corresponding vertical motion control motor (1) to make the nozzle move downward to complete the adsorption of the second plug.

6. The method according to claim 5, characterized in that, The linear extended state observer in the linear active disturbance rejection controller treats the mechanical friction, changes in flexible support force, and elastic torque of the flexible copper wire generated by the special end effector during the sequential adsorption process as the total system disturbance acting on the corresponding drive motor, performs real-time estimation, and provides dynamic feedforward compensation at the control output.

7. The method according to claim 5, characterized in that, In steps 2 and 4, when the nozzle contacts the flexible circuit board plug, the linear expansion state observer detects the sudden change in the flexible support force and automatically reduces the output torque of the vertical motion control motor (1) by the linear state error feedback control law. With the help of the encoder feedback safety lower limit position protection, the nozzle and the plug make smooth contact.

8. The method according to claim 5, characterized in that, The encoder provides real-time feedback of displacement or angle information of each motor at a frequency of 1 kHz, the visual recognition system acquires plug position images at a frequency of 30 Hz, and the linear expansion state observer performs iterative estimation of the total disturbance at a sampling period of 1 kHz.

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