Design And Research Of Pipetting Control System Of Fully Automatic Pipetting Workstation

With the outbreak of severe acute respiratory syndrome(SARS)in 2003 and diseases such as the new coronavirus pneumonia(COVID-19)in 2019,a large number of suspected infections need to be diagnosed in the shortest possible time,in order to the epidemic situation should be controlled accurately so that effective prevention and control measures can be taken.The most effective method is to use more rapid,more accurate and highly automated high-throughput nucleic acid detection technology to complete the rapid diagnosis by detecting the nucleic acid sequence of the pathogen in the patient sample to achieve a shorter detection window.Due to the traditional method of manual processing,high time and labor cost,and in the process of reagent sample processing,manual operation is easy to induce sample pollution,resulting in unreliable data.Therefore,it has become the trend of high-throughput sample processing in the field of biology and medicine that the automatic operation of liquid processing replaces the tedious manual labor.In the paper,based on the research of domestic and foreign micropipetting technology and the current demand for pipetting in related fields,a set of automatic pipetting workstation pipetting control system is designed.The control system adopts the modular function design concept,uses the air displacement liquid transfer technology and the air pressure liquid level detection technology to achieve the high precision,high efficiency and high reliability processing requirements for biological reagent samples.Firstly,this paper designs the overall scheme of the liquid transfer control system.STM32 single-chip microcomputer is used as the hardware controller of the lower computer to complete the control of each motor,sensor and micro liquid transfer pump,RS485 communication is established through MODBUS protocol to complete the communication with the PC end of the upper computer.The servo motor is used as the X-axis driving element,the Y-axis / Z-axis / liquid transfer pump driving shaft is used as the stepping motor,and the(SUENW)NPN-U photoelectric sensor is used to realize the mechanical shaft in the liquid transfer process.In order to improve the precision of the full-automatic liquid transfer workstation,a data acquisition system of the pneumatic liquid level detection is designed with the pressure sensor of Honeywell 40PC100G2 A.The experimental results show that the system can not only detect the liquid level,but also monitor the air pressure in the process of liquid transfer in real time,and detect the bubbles and suction heads in the process of liquid transfer in time Blockage and other abnormal conditions,greatly improving the efficiency of liquid transfer.At the same time,the software and hardware of the control system are designed.The hardware part mainly completes the circuit diagram design of each functional module in the liquid transfer control system and the drawing of PCB circuit board.The software part completes the flow chart construction of PC upper computer control system and the personalized design of user operation interface,and the program diagram design of air pressure data acquisition system based on Lab VIEW development environment A semi closed loop multi axis motion control algorithm based on time sequence coupling is proposed.The quality method is used to verify the accuracy of the control system.The allowable error and repeatability deviation of the data capacity of the system are in line with the requirements of GGJ646-2006.