Research Of Closed-Loop Control Of Micro Water And Medicine Supplying System Based On Stepper Motor

Microfluidic technology which can integrate a series of traditional chemistry and biology experimental procedures,such as the injection,reaction,separation and detection of samples,has found an increasingly wide utilization in biomedical detection and chemical analysis.Most conditions engaging microfluidic technology require micro-flow,while the injection pump and peristaltic pump which are widely used to provide micro-flow have drawbacks of long settling time,excessive flow pulsation,incapability of closed-loop control and wireless transmission.The closed-loop controlling method of micro water and medicine supplying system based on stepper motor proposed in this paper achieves the stabilized output of microflow,with the integration of microfluidic equipment enhanced and settling time shortened,which can be used in drug delivery of clinical medicine,precision irrigation and biological and chemical analysis.A circuit equivalent method is advanced in this paper in order to analysis the operational principle of the medicine supplying system conveniently;the mathematical model of the system is established.The computational formula of the deformation of micro channel is constructed based on energy method and virtual work principle,and Matlab/Simulink is utilized to analysis the open-loop characteristic of the system.The response characteristic of stepper motor is obtained;the difference of volume flow in micro valve under different air pressure is analyzed,and the relation between flow rate of micro valve and pressure of air source and opening of the valve is analyzed.Meanwhile,the effect of gas pressure changing on the flow of microfluidic chip and the relationship between volume flow rate and gas pressure are analyzed,and the effect of the gas pressure,the size of the micro channel,the volume of the air chamber in the airtight vessel and the flow path of the microfluidic chip on the flow characteristics of the microfluidic chip and the liquid filling length are investigated.This paper presents a comparison of the effect of intelligent PID,PWM controller and Bang-Bang controller of the aforementioned system;the influence of air pressure and external disturbance on system settling time,overshoot and control accuracy is analyzed;based on the comparison,single-valve Bang-Bang controller is finally chosen to control the flow rate of microfluidic chips,then the effect on the control precision of the opening of vent micro valve,different flow settings and gas pressure,and interference of different types of air sources are investigated.The pouring and encapsulation of microfluidic chip are accomplished in this paper,and the micro valve module with control module is designed.An experimental platform is built,which can realize the producing of two channels of micro flow;the operating characteristics and maximum operating frequency of stepper motor are tested;meanwhile,the relation between the pressure in the airtight container and the opening of the valve was tested;the open-loop characteristics of the micro valve and microfluidic chip are tested,and the difference between the experimental results and the simulation results is analyzed;closed loop control experiment is carried out to compare the advantages and disadvantages of the three control methods;the control effect of Bang-Bang controller under the condition of changing pressure of air source is studied,and wireless data transmission is also designed.