Automatic detection system for digital wheel of pipettor

Abstract

The invention discloses an automatic detection system for a digital wheel of a pipettor, belongs to the technical field of production quality detection of the pipettor, and aims to solve the problems of low efficiency, strong subjectivity, single function and difficulty in data tracing caused by dependence on manual work or a simple photoelectric sensor in detection of the digital wheel of the conventional pipettor. The system comprises a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electric control and processing unit and a sorting and removing mechanism. According to the system, full-automatic and high-precision detection of the digital wheel of the pipettor is realized, the detection efficiency and the quality consistency are effectively improved, and meanwhile, the system has a perfect data tracing function and is suitable for an online quality detection link in batch production of the pipettor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipette production quality detection, and discloses a pipette digital wheel automatic detection system. BACKGROUND

[0002] The pipette is a key instrument for accurately measuring and transferring liquid in the laboratory, and its accuracy directly depends on the performance of the digital wheel. The scale clarity, position accuracy and correspondence between the digital and the range of the digital wheel play a decisive role in the final use effect of the pipette.

[0003] In the current pipette production and assembly process, digital wheel detection mainly relies on two existing technologies, and both have significant defects. On the one hand, the detection speed is extremely slow, which is difficult to adapt to the high rhythm production demand of modern production line, becoming the bottleneck link in the production process. On the other hand, the detection standard is greatly influenced by the degree of fatigue, emotional state and operation experience of the workers, and is highly subjective, which is easy to cause missed detection (judging defective products as qualified) and misjudgment (judging qualified products as unqualified), and cannot guarantee the consistency of product quality. In addition, this detection method has no quantitative data record, and when subsequent quality problems occur, it is difficult to trace the root cause and conduct targeted analysis. Simple photoelectric sensor detection can only realize basic function detection, such as judging whether the digital wheel rotates or whether there is a specific mark, and cannot identify complex information such as specific digital content, scale line integrity and character clarity on the digital wheel, and has single function. At the same time, for different models and different scale specifications of pipette digital wheels, the sensor position and parameters need to be adjusted again, which has low flexibility and poor adaptability. Moreover, for complex appearance defects such as character printing blur, broken line, dirt and slight position deviation, this detection method is difficult to cope with.

[0004] In summary, there is a lack of a pipette digital wheel automatic detection scheme in the prior art that can realize fast, accurate and objective detection, and can conduct data tracing. SUMMARY

[0005] The application provides a pipette digital wheel automatic detection system, which aims to solve the problems of low efficiency, strong subjectivity, single function and difficult data tracing caused by the existing pipette digital wheel detection relying on manual or simple photoelectric sensor.

[0006] A pipette digital wheel automatic detection system, comprising a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electric control and processing unit, and a sorting and rejection mechanism. The feeding and positioning mechanism is used to receive the pipette semi-finished product conveyed by the assembly line, and accurately position the pipette, so that the digital wheel is in the preset detection station. The trigger and drive mechanism is used to drive the digital wheel to rotate, so that it displays different range values in turn; the machine vision imaging system is used to capture the image of the digital wheel; the electric control and processing unit is electrically connected with the feeding and positioning mechanism, the trigger and drive mechanism, the machine vision imaging system and the sorting and rejecting mechanism, and is used to control the operation timing of each mechanism, process image data and determine the detection result; The sorting and rejecting mechanism is used to reject unqualified products and convey qualified products to the next station according to the detection result signal sent by the electric control and processing unit. The PLC of the electric control and processing unit and the industrial computer are used to perform real-time data interaction through the EtherNet / IP protocol, and the industrial computer is internally provided with an SD card storage module, which is used to automatically record the unique product serial number of each pipette, the determination result of each detection point and the digital wheel image when the product is unqualified.

[0007] Optionally, the feeding and positioning mechanism comprises a clamp or a V-shaped block, which is used to clamp the pipette to achieve accurate positioning of the pipette. The parallelism error between the positioning reference surface of the clamp or V-shaped block and the axis of the digital wheel is ≤0.02mm, and the clamp is provided with a double-cylinder clamping assembly, the clamping force is adjusted through a pressure regulating valve in the range of 80-150N, and the contact end of the clamping assembly is wrapped with silica gel material.

[0008] Optionally, the trigger and drive mechanism comprises a precision stepping motor or a servo motor, the drive end of the precision stepping motor or servo motor is engaged with the adjustment knob of the pipette, and is used to simulate the action of human hand to accurately rotate the digital wheel. The step angle of the precision stepping motor is 1.8°, the step angle accuracy is ≤±3%, and the drive end is provided with an elastic coupler made of polyurethane, and the radial compensation amount of the coupler is 0.15-0.25mm, which is used to adapt to the coaxiality error of the adjustment knob of different models of pipettes.

[0009] Optionally, the machine vision imaging system comprises a line scan camera, which adopts high-resolution CCD line-by-line scanning, and is fixedly installed in front of the digital wheel, and its field of view supports complete coverage of the entire area of the digital wheel; The CCD pixel resolution of the line scan camera is 2048 pixels, the scanning line rate is ≥6000 lines / s, the distance between the camera lens and the surface of the digital wheel is fixed at 150±5mm, and an aluminum anti-interference shell is installed outside the camera, and a wave-absorbing material is pasted on the inner wall of the shell to shield external electromagnetic interference.

[0010] Optionally, the machine vision imaging system further comprises an industrial lens, which has an adapted focal length and depth of field, and is used to obtain a clear and distortion-free image of the digital wheel. The industrial lens has a focal length of 25mm, a depth of field range of 10-30mm, a distortion rate of ≤0.05%, and an adjustable polarizer installed at the front end of the lens. The polarization angle of the polarizer can be manually adjusted within the range of 0°-90° to filter the reflection of the metal material on the surface of the digital wheel.

[0011] Optionally, the machine vision imaging system further includes a light source system, which is a ring light source, a strip light source, a low-angle dome light, or a coaxial light, used to highlight the characters and scales on the digital wheel and eliminate reflections and shadow interference to form a high-contrast image. The light source system is equipped with a digital light source controller, which receives PWM signals output by the PLC to adjust the brightness of the light source. The brightness adjustment range is 200-800 cd / m², and the angle between the light source and the center of the digital wheel is fixed at 45°. The housing of the light source is made of diffuse reflective material.

[0012] Optionally, the electrical control and processing unit includes a programmable logic controller (PLC). The PLC acts as a lower-level machine, used to control the feeding and positioning, triggering and driving the motor rotation of the mechanism, taking pictures with the camera of the machine vision imaging system, receiving detection results, and controlling the operation of the sorting and rejection mechanism. The PLC uses the Siemens S7-1200 series, and its built-in timing control program is used to control the time interval between the motor rotation positioning signal and the camera photo trigger signal to ≤8ms. The PLC is also equipped with an RS485 communication interface to connect with the production line MES system for real-time uploading of inspection pass rate data.

[0013] Optionally, the industrial computer serves as a host computer, with built-in image processing software for receiving images acquired by the machine vision imaging system and running image processing algorithms.

[0014] Optionally, the sorting and rejection mechanism includes a cylinder, a push rod, or a flipping mechanism, which is used to push unqualified products to the defective product channel and transfer qualified products to the next station. The cylinder of the sorting and rejection mechanism is an SMC mini cylinder with a cylinder action response time of ≤400ms. A diffuse reflection photoelectric sensor is installed at the inlet of the mechanism with a detection distance of 50-100mm to identify whether the pipette has reached the rejection position.

[0015] Optionally, the precision stepper motor or servo motor of the triggering and driving mechanism is electrically connected to the PLC of the electronic control and processing unit. The PLC can send control signals to the precision stepper motor or servo motor to adjust the motor rotation angle so that the digital wheel jumps to the range value to be detected. The PLC sends angle control commands to the motor with a resolution of 0.005°. The motor drive system has a power failure memory function, which is used to automatically restore the last detected range point after a power failure and restart. The motor has a built-in encoder, which is also used to provide real-time feedback of the rotation angle to the PLC, forming a closed-loop control.

[0016] This invention discloses an automatic detection system for digital pipette wheels, belonging to the field of pipette production quality inspection technology. It aims to solve the problems of low efficiency, high subjectivity, limited functionality, and difficulty in data traceability caused by existing digital pipette wheel detection methods that rely on manual labor or simple photoelectric sensors. The system includes a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electrical control and processing unit, and a sorting and rejection mechanism. The feeding and positioning mechanism receives semi-finished pipettes from the production line and precisely positions them, placing the digital wheel at a preset detection station. The triggering and driving mechanism drives the digital wheel to rotate, sequentially displaying different volume values. The machine vision imaging system captures clear images of the digital wheel. The electrical control and processing unit is electrically connected to each mechanism, controlling the operation sequence of each mechanism, processing image data, and determining the detection results. Its PLC interacts with an industrial computer in real time via the EtherNet / IP protocol. The industrial computer has a built-in SD card storage module to record the product serial number, detection results, and images of defective pipettes for each unit. The sorting and rejection mechanism automatically sorts qualified and unqualified products based on the detection results. This system enables fully automated, high-precision detection of digital pipette wheels, effectively improving detection efficiency and quality consistency. It also features comprehensive data traceability capabilities, making it suitable for online quality inspection in the mass production of pipettes. Attached Figure Description

[0017] Figure 1 This application provides an illustrative embodiment of an automatic detection system for a digital pipette wheel. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0019] In this article, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0020] Example 1 An automatic detection system for digital pipette wheels includes a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electrical control and processing unit, and a sorting and rejection mechanism.

[0021] The feeding and positioning mechanism receives the semi-finished pipettes conveyed from the production line and precisely positions the pipettes, placing the digital wheel at a preset detection station. The triggering and driving mechanism drives the digital wheel to rotate, sequentially displaying different volume values. The machine vision imaging system captures images of the digital wheel. The electrical control and processing unit is electrically connected to the feeding and positioning mechanism, the triggering and driving mechanism, the machine vision imaging system, and the sorting and rejection mechanism, respectively, and is used to control the operating sequence of each mechanism, process image data, and determine the detection results. The sorting and rejection mechanism, based on the detection result signal issued by the electrical control and processing unit, rejects defective products and conveys qualified products to the next station.

[0022] The PLC of the electrical control and processing unit and the industrial computer use the EtherNet / IP protocol for real-time data interaction. The industrial computer has a built-in SD card storage module to automatically record the unique product serial number of each pipette, the judgment results of each detection point, and the digital wheel image when it fails.

[0023] Furthermore, the electrical control and processing unit of this automatic pipette wheel inspection system utilizes an industrial-grade MicroSD card with a storage capacity of ≥32GB and supports RAID1 mirroring backup, preventing data loss due to a single SD card failure. Simultaneously, the electrical control and processing unit integrates an independent isolated power supply module. This module's input voltage is adapted to the industrial environment's AC220V±10% fluctuation range, while its output voltage is a stable DC24V±0.5V. It also features overvoltage (≥28V), overcurrent (≥5A), and short-circuit protection, enabling rapid power cut-off in case of voltage abnormalities to ensure stable operation of the PLC and industrial computer. Additionally, the EtherNet / IP protocol transmission line between the PLC and industrial computer uses shielded Cat5e network cable, with both ends of the shield grounded via copper lugs, achieving a grounding resistance ≤4Ω. This further reduces the impact of electromagnetic interference on data exchange. Moreover, the inspection data management software within the industrial computer supports multi-dimensional searches by product serial number, inspection date, and defect type, with a search response time ≤1 second, facilitating rapid retrieval of historical inspection data and improving the efficiency of quality problem tracing.

[0024] Example 2 Furthermore, the feeding and positioning mechanism includes clamps or V-blocks, which are used to clamp the pipette to achieve precise positioning of the pipette.

[0025] The parallelism error between the positioning reference surface of the fixture or V-block and the center line of the digital wheel is ≤0.02mm. The fixture is equipped with a double-cylinder clamping assembly. The clamping force is adjusted in the range of 80-150N by a pressure regulating valve. The contact end of the clamping assembly is wrapped with silicone material.

[0026] Furthermore, the clamps or V-block positioning reference surfaces of the feeding and positioning mechanism are precision ground with a surface roughness Ra≤0.8μm, and the edges of the reference surfaces have a 0.5mm×45° chamfer structure to prevent scratching the pipette's plastic housing during positioning. Each cylinder piston rod of the dual-cylinder clamping assembly is equipped with a laser displacement sensor, with a displacement measurement accuracy ≤0.01mm, which can monitor the stroke position of the clamping assembly in real time. When the stroke deviation exceeds 0.1mm, an alarm signal is automatically sent to the PLC to avoid inaccurate positioning due to cylinder leakage or piston rod jamming. The silicone layer at the contact end of the clamping assembly is made of food-grade silicone with a Shore hardness of 50±5A, integrally molded with the clamping assembly body through a molding process. The silicone layer thickness is uniformly controlled at 1.5-2mm, which not only ensures buffer protection for the pipette during clamping but also prevents the silicone layer from falling off and contaminating the pipette. At the same time, the surface of the silicone layer has 0.1mm deep anti-slip textures to increase the friction with the pipette housing and prevent the pipette from shifting during detection.

[0027] Furthermore, the triggering and driving mechanism includes a precision stepper motor or a servo motor. The drive end of the precision stepper motor or servo motor engages with the adjustment knob of the pipette to simulate the precise rotation of the digital wheel by human hand movements.

[0028] The precision stepper motor has a step angle of 1.8° and a step angle accuracy of ≤±3%. The drive end is equipped with a polyurethane elastic coupling with a radial compensation of 0.15-0.25mm to accommodate the coaxiality error of the adjustment knobs of different pipette models.

[0029] The precision stepper motor stator core of the triggering and driving mechanism is made of 0.35mm thick high-silicon steel sheets, with a stacking coefficient ≥0.95, which effectively reduces iron loss during motor operation and ensures that the temperature rise of the motor during continuous operation (5r / min) is ≤40K (ambient temperature 25℃). The flexible coupling is connected to the motor output shaft and the pipette adjustment knob adapter at both ends via flat keys. The adapter has a replaceable polyurethane inner bushing with an inner diameter that adapts to the outer diameter of different pipette adjustment knobs ranging from 6-12mm. The inner bushing surface has a 0.2mm deep diamond-shaped anti-slip texture to enhance friction with the adjustment knob and prevent slippage during rotation. In addition, a stainless steel axial limiting retaining ring with a thickness of 2mm is provided between the motor output shaft and the adapter. The retaining ring is fixed to the adapter with hexagonal screws to limit the axial displacement of the adapter and ensure that the motor torque is stably transmitted to the adjustment knob. The retaining ring surface is galvanized to prevent rust from affecting assembly accuracy after long-term use.

[0030] Furthermore, the machine vision imaging system includes a line scan camera, which uses a high-resolution CCD for progressive scanning and is fixedly mounted in front of the digital wheel. Its field of view supports complete coverage of the entire area around the digital wheel.

[0031] The line scan camera has a CCD pixel resolution of 2048 pixels, a scanning line rate of ≥6000 lines / second, a fixed distance of 150±5mm between the camera lens and the surface of the digital wheel, and an aluminum anti-interference shell is installed on the outside of the camera. The inner wall of the shell is covered with wave-absorbing material to shield against external electromagnetic interference.

[0032] The line scan camera in the machine vision imaging system uses a global shutter CCD chip, allowing for stepless adjustment of exposure time from 1μs to 100ms. This adapts to the image acquisition needs of digital wheels under varying brightness conditions. The camera is equipped with a precision lens mount secured by an M4 locking nut, with an adjustment accuracy of ≤0.01mm. The lens focal length can be finely adjusted according to the 15-30mm diameter of the digital wheel to ensure consistent sharpness between the image edges and center. A 2mm thick aluminum anti-interference housing contains 10mm-spaced, 5mm-high aluminum heat dissipation fins, aiding in heat dissipation through natural convection and keeping the camera's operating temperature within the 0-50℃ range. A 2mm thick ferrite absorber is attached to the inner wall of the housing, covering ≥90% of the inner wall area. An EMI filter is connected in series at the camera's power interface, with an insertion loss ≥30dB in the 100kHz-1GHz frequency range, effectively suppressing electromagnetic interference on the power line and preventing interference signals from affecting the camera's image acquisition quality.

[0033] Furthermore, machine vision imaging systems also include industrial lenses with appropriate focal lengths and depths of field, used to acquire clear, distortion-free images of digital wheels.

[0034] The industrial lens has a focal length of 25mm, a depth of field range of 10-30mm, and a distortion rate of ≤0.05%. An adjustable polarizer is installed at the front of the lens, and the polarization angle of the polarizer can be manually adjusted within the range of 0°-90° to filter the reflection of metal material on the surface of the digital wheel.

[0035] The industrial lens of the machine vision imaging system uses a combination of 8 optical lenses in 6 groups. The lenses are made of low-dispersion K9 optical glass and have a multi-layer anti-reflection coating. The transmittance in the 450-650nm visible light band is ≥98%, which reduces light reflection loss and improves image brightness uniformity. The adjustable polarizer at the front of the lens is connected to the lens via an M12 thread. The polarizer adjustment knob has a scale marking from 0 to 90°, with each mark corresponding to an adjustment amount of 2°, allowing operators to accurately adjust the polarization angle based on the reflection of the digital wheel surface. In addition, the lens housing is equipped with an M3 focal length locking screw. After the lens focal length is adjusted to the correct position, tightening the locking screw can prevent focal length shift caused by workshop vibration. The locking screw is made of stainless steel with a blackened surface treatment, which is both rust-proof and easy to operate with an Allen wrench. At the same time, the lens housing is anodized, with a surface hardness of HV≥200, which can improve the lens's wear resistance and scratch resistance.

[0036] Furthermore, the machine vision imaging system also includes a light source system, which can be a ring light source, a bar light source, a low-angle dome light, or a coaxial light source, used to highlight the characters and scales on the digital wheel and eliminate reflections and shadows to form a high-contrast image.

[0037] The light source system is equipped with a digital light source controller, which receives PWM signals output by the PLC to adjust the brightness of the light source. The brightness adjustment range is 200-800 cd / m², and the angle between the light source and the center of the digital wheel is fixed at 45°. The housing of the light source is made of diffuse reflective material.

[0038] In the light source system of the machine vision imaging system, the digital light source controller has a built-in 8-bit microprocessor and supports communication with an industrial computer via an RS232 interface. It can remotely set and monitor the brightness of the light source in real time, and the controller has a brightness memory function. After a power failure and restart, it can automatically restore the previously set brightness parameters (200-800 cd / m²). The 45° angle between the light source and the center of the digital wheel is fixed by an adjustable aluminum alloy bracket. The bracket has an angle scale dial of 0-90° with a scale accuracy of 1°. The bottom of the bracket is connected to the detection platform through a waist-shaped hole (20mm long and 8mm wide), which can finely adjust the horizontal position of the light source to ensure that the light source illumination area accurately covers the digital wheel. The light source shell is made of ABS engineering plastic injection molding. The inner wall has a honeycomb texture with a depth of 0.3mm and a side length of 5mm, which can enhance the diffuse reflection effect of light and make the illumination uniformity of the digital wheel surface ≥90%, avoiding image detection errors caused by local over-brightness or under-brightness. At the same time, the shell surface is matte to prevent the reflection of the light source shell into the camera lens and form stray light.

[0039] Furthermore, the electrical control and processing unit includes a programmable logic controller (PLC). The PLC acts as a lower-level machine, used to control the feeding and positioning, triggering and driving the motor rotation of the mechanism, taking pictures with the camera of the machine vision imaging system, receiving detection results, and controlling the operation of the sorting and rejection mechanism.

[0040] In addition, the industrial computer acts as the host computer, with built-in image processing software, used to receive images acquired by the machine vision imaging system and run image processing algorithms.

[0041] The industrial computer uses an embedded motherboard, integrating an Intel Core i5-1035G1 processor (≥2.5GHz), 8GB DDR4 laptop memory, and a 128GB industrial-grade SSD, ensuring smooth operation of the image processing software. The processing time for a single digital wheel image (2048×1080 pixels resolution) is ≤200ms. The image processing software has a built-in image calibration module, supporting the import of standard checkerboard calibration board (10mm×10mm checkerboard size) images for pixel size calibration, with a calibration accuracy ≤0.001mm / pixel. However, the software has some defects. The intelligent annotation function can automatically select defective areas (such as missing characters or broken scale lines) on unqualified images with a red rectangle and annotate the defect type. The annotation information is stored in association with the inspection data. The software also supports the inspection data export function, which can export data to Excel or CSV format. During the export process, an MD5 data check code is automatically generated to prevent data tampering. At the same time, the software has a three-level user permission management system (administrator, operator, and viewer). Different users with different permissions can operate different functional modules, which can effectively prevent unauthorized personnel from modifying inspection parameters (such as character recognition threshold and scale integrity judgment standard).

[0042] Furthermore, the PLC adopts the Siemens S7-1200 series, and its built-in timing control program is used to control the time interval between the motor rotation positioning signal and the camera photo trigger signal to ≤8ms. The PLC is also equipped with an RS485 communication interface to connect with the production line MES system for real-time uploading of inspection pass rate data.

[0043] The Siemens S7-1200 series PLC in the electrical control and processing unit is expanded with 4 analog input modules. These modules support 4-20mA current signal input and can be connected to the light source brightness detection sensor in the machine vision imaging system, as well as the motor temperature sensor signal in the trigger and drive mechanism. This allows for real-time acquisition and monitoring of key parameters such as light source brightness (200-800 cd / m²) and motor temperature (≤60℃). When these parameters exceed preset thresholds, the PLC automatically triggers a shutdown protection program and sends an alarm signal to the industrial computer. The PLC's built-in timing control program uses ladder logic programming and incorporates dual redundancy. The timer has a time error of ≤0.1ms, ensuring that the time interval between the motor rotation positioning signal and the camera photo trigger signal is stable at ≤8ms. The PLC's RS485 communication interface adopts an opto-isolation design with an isolation voltage of ≥2500Vrms. The communication rate can be set within the range of 9600bps-115200bps. A TVS transient voltage suppressor diode (model SMBJ6.5CA) is connected in parallel at the interface to prevent external surge voltage from damaging the communication port, ensuring stable communication with the production line MES system and enabling real-time uploading of inspection pass rate data (upload frequency 1 time / minute).

[0044] Furthermore, the sorting and rejection mechanism includes cylinders, push rods, or flipping mechanisms, which are used to push defective products to the defective product channel and transfer qualified products to the next station.

[0045] The cylinders of the sorting and rejection mechanism are SMC mini cylinders with a cylinder action response time of ≤400ms. A diffuse reflection photoelectric sensor is installed at the inlet of the mechanism with a detection distance of 50-100mm to identify whether the pipette has reached the rejection position.

[0046] The SMC mini cylinder for the sorting and rejection mechanism is model CDJ2B16-20-B, with a cylinder diameter of 16mm and a stroke of 20mm. The cylinder barrel undergoes hard anodizing treatment, with a surface hardness of HV≥300, improving the cylinder's wear resistance and corrosion resistance. The cylinder seal is made of fluororubber, suitable for a working temperature range of -20℃ to 80℃, ensuring reliable sealing and no leakage under different workshop temperature environments. The diffuse reflection photoelectric sensor is model E3Z-D61, with an adjustable detection distance of 50-100mm, a detection accuracy of ≤0.5mm, and an output signal of NPN type normally open switch, with a response time of... With a sensitivity adjustment knob of ≤1ms, the sensor can be adjusted according to the color of the pipette housing (transparent, white, black, etc.) to avoid false detections due to color differences. In addition, a polyurethane buffer block is installed at the end of the push rod of the sorting and rejection mechanism. The buffer block is 5mm thick and has a Shore hardness of 30±5A. It can buffer when pushing non-conforming products to prevent the push rod from hitting the pipette and causing damage to the housing. A 1mm thick wear-resistant nylon liner is pasted on the inner wall of the defective product channel. The liner surface is smooth (friction coefficient ≤0.15) to ensure that non-conforming products slide smoothly and avoid product jamming caused by the rough inner wall of the channel.

[0047] Furthermore, the precision stepper motor or servo motor that triggers and drives the mechanism is electrically connected to the PLC of the electronic control and processing unit. The PLC can send control signals to the precision stepper motor or servo motor to adjust the motor rotation angle, so that the digital wheel jumps to the range value to be detected.

[0048] The PLC sends angle control commands to the motor with a resolution of 0.005°. The motor drive system has a power failure memory function, which is used to automatically restore the last detected range point after power failure and restart. The motor has a built-in encoder, which is also used to provide real-time feedback of the rotation angle to the PLC, forming a closed-loop control.

[0049] In the triggering and driving mechanism, the angle control commands sent by the PLC to the precision stepper motor or servo motor are transmitted via pulse signals. The pulse frequency can be adjusted within the range of 1kHz-100kHz, corresponding to a motor rotation speed of 0.5-50r / min, which can meet the detection requirements of different models of digital pipette wheels (speed requirement 1-10r / min). The power-off memory function of the motor drive system is achieved through a 1F supercapacitor. The supercapacitor can maintain the memory data for ≥30 minutes after a power failure. Furthermore, the drive system has a built-in voltage detection circuit. When the supply voltage is detected to be lower than DC20V, the data saving program is automatically triggered, and the current measurement range is updated. The position data is written to non-volatile memory; the incremental encoder built into the motor has a resolution of 1000 lines / revolution and outputs two-phase quadrature signals A and B. The PLC calculates the actual rotation angle of the motor by decoding the quadrature signals at four times the frequency, with a decoding accuracy of up to 0.36° (360° / 1000 / 4). A differential transmission module is connected in series on the encoder signal line, with a differential transmission distance of ≤10m, which can reduce the attenuation and interference during signal transmission, ensure the accuracy of closed-loop control, and stabilize the motor rotation angle control error within ≤±0.01°, thereby ensuring that the digital wheel can accurately jump to the detection range value (such as 10μL, 20μL, 50μL, 100μL).

[0050] In summary, the system provided in this application includes a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electrical control and processing unit, and a sorting and rejection mechanism. The feeding and positioning mechanism receives and precisely positions the semi-finished pipettes conveyed from the production line, placing the digital wheel at a preset detection station. The triggering and driving mechanism drives the digital wheel to rotate, sequentially displaying different volume values. The machine vision imaging system captures clear images of the digital wheel. The electrical control and processing unit is electrically connected to each mechanism, controlling the operational sequence of each mechanism, processing image data, and determining the detection results. Its PLC interacts with an industrial computer in real time via the EtherNet / IP protocol. The industrial computer has a built-in SD card storage module to record the product serial number, detection results, and images of defective pipettes for each unit. The sorting and rejection mechanism automatically sorts qualified and unqualified products based on the detection results. This system achieves fully automated, high-precision detection of the digital wheel of the pipette, effectively improving detection efficiency and quality consistency. It also possesses comprehensive data traceability capabilities and is suitable for online quality inspection in the mass production of pipettes.

[0051] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An automatic detection system for digital pipette wheels, characterized in that, It includes a feeding and positioning mechanism, a triggering and driving mechanism, a machine vision imaging system, an electronic control and processing unit, and a sorting and rejection mechanism; The feeding and positioning mechanism is used to receive the semi-finished pipettes conveyed by the production line and to accurately position the pipettes so that the digital wheel is in the preset detection position. The triggering and driving mechanism is used to drive the digital wheel to rotate, so that it displays different range values ​​in sequence; the machine vision imaging system is used to capture the image of the digital wheel; the electrical control and processing unit is electrically connected to the feeding and positioning mechanism, the triggering and driving mechanism, the machine vision imaging system and the sorting and rejection mechanism respectively, and is used to control the running sequence of each mechanism, process image data and determine the detection results. The sorting and rejection mechanism is used to reject defective products and transfer qualified products to the next workstation based on the detection result signal issued by the electronic control and processing unit. The PLC of the electrical control and processing unit and the industrial computer use the EtherNet / IP protocol for real-time data interaction. The industrial computer has a built-in SD card storage module for automatically recording the unique product serial number of each pipette, the judgment results of each detection point, and the digital wheel image when it fails to meet the requirements.

2. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The feeding and positioning mechanism includes a clamp or a V-block, which is used to clamp the pipette to achieve precise positioning of the pipette; The parallelism error between the positioning reference surface of the fixture or V-block and the center line of the digital wheel is ≤0.02mm. The fixture is equipped with a double-cylinder clamping assembly, and the clamping force is adjusted in the range of 80-150N by a pressure regulating valve. The contact end of the clamping assembly is wrapped with silicone material.

3. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The triggering and driving mechanism includes a precision stepper motor or a servo motor. The driving end of the precision stepper motor or servo motor engages with the adjustment knob of the pipette to simulate the precise rotation of the digital wheel by human hand movements. The precision stepper motor has a step angle of 1.8° and a step angle accuracy of ≤±3%. The drive end is equipped with a polyurethane elastic coupling with a radial compensation of 0.15-0.25mm to accommodate the coaxiality error of the adjustment knobs of different pipette models.

4. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The machine vision imaging system includes a line scan camera, which uses a high-resolution CCD for progressive scanning and is fixedly installed in front of the digital wheel. Its field of view supports complete coverage of the entire area around the digital wheel. The line scan camera has a CCD pixel resolution of 2048 pixels, a scanning line rate of ≥6000 lines / second, a fixed distance of 150±5mm between the camera lens and the surface of the digital wheel, and is equipped with an aluminum anti-interference shell with wave-absorbing material pasted on the inner wall of the shell to shield against external electromagnetic interference.

5. The automatic detection system for digital pipette wheels according to claim 4, characterized in that, The machine vision imaging system also includes an industrial lens with a suitable focal length and depth of field for acquiring clear, distortion-free images of the digital wheel. The industrial lens has a focal length of 25mm, a depth of field range of 10-30mm, a distortion rate of ≤0.05%, and an adjustable polarizer installed at the front end of the lens. The polarization angle of the polarizer can be manually adjusted within the range of 0°-90° to filter the reflection of the metal material on the surface of the digital wheel.

6. The automatic detection system for digital pipette wheels according to claim 4, characterized in that, The machine vision imaging system also includes a light source system, which is a ring light source, a strip light source, a low-angle dome light, or a coaxial light, used to highlight the characters and scales on the digital wheel and eliminate reflections and shadow interference to form a high-contrast image. The light source system is equipped with a digital light source controller, which receives PWM signals output by the PLC to adjust the brightness of the light source. The brightness adjustment range is 200-800 cd / m², and the angle between the light source and the center of the digital wheel is fixed at 45°. The housing of the light source is made of diffuse reflective material.

7. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The electrical control and processing unit includes a programmable logic controller (PLC). The PLC acts as a lower-level machine, used to control the feeding and positioning, the motor rotation of the triggering and driving mechanism, the camera of the machine vision imaging system to take pictures, receive detection results, and control the operation of the sorting and rejection mechanism. The PLC uses the Siemens S7-1200 series, and its built-in timing control program is used to control the time interval between the motor rotation positioning signal and the camera photo trigger signal to ≤8ms. The PLC is also equipped with an RS485 communication interface to connect with the production line MES system for real-time uploading of inspection pass rate data.

8. The automatic detection system for digital pipette wheels according to claim 7, characterized in that, The industrial computer serves as the host computer, with built-in image processing software used to receive images acquired by the machine vision imaging system and run image processing algorithms.

9. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The sorting and rejection mechanism includes a cylinder, a push rod, or a flipping mechanism. The cylinder, push rod, or flipping mechanism is used to push unqualified products to the defective product channel and transfer qualified products to the next station. The cylinder of the sorting and rejection mechanism is an SMC mini cylinder with a cylinder action response time of ≤400ms. A diffuse reflection photoelectric sensor is installed at the inlet of the mechanism with a detection distance of 50-100mm to identify whether the pipette has reached the rejection position.

10. The automatic detection system for digital pipette wheels according to claim 1, characterized in that, The precision stepper motor or servo motor of the triggering and driving mechanism is electrically connected to the PLC of the electronic control and processing unit. The PLC can send control signals to the precision stepper motor or servo motor to adjust the motor rotation angle so that the digital wheel jumps to the range value to be detected. The PLC sends angle control commands to the motor with a resolution of 0.005°. The motor drive system has a power failure memory function, which is used to automatically restore the last detected range point after a power failure and restart. The motor has a built-in encoder, which is also used to provide real-time feedback of the rotation angle to the PLC, forming a closed-loop control.

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