PCR Instrument Temperature Control System

The polymerase chain reaction(PCR)instrument is a medical device which can simulate the environment of DNA replication in the human body,a hardware platfom is used to realize vitro DNA replication using the-proper control algorithms.It is great significance for fast disease diagnosis to study how to increase the PCR efficiency.This article analyzes the performance of existing domestic and foreign PCR instruments.In view of the conflict of the temperature response speed and the temperature accuracy,we design the hardware circuits and improve the temperature control algorithm.The temperature increasing and decreasing rate is reduced,the overshoot is reduced at the same time,and the control accuracy is enhanced.The main contents of the article includes the following several aspects:(1)The hardware circuit design and software programming of PCR instrument based on STM32F103ZET6 microcontroller are completed.The improved temperature detection module can achieve the temperature resolution equal to 0.1?.For the temperature control system,the semiconductor refrigeration chip is selected for heating or cooling source.(2)A host computer program based on Microsoft Visual Basic is completed which is used to send instructions to the PCR instrument,and to display the working status of the PCR instrument in real time.This upper computer can save the collected temperature data for plotting variably curve.(3)Based on the working principle of the semiconductor refrigeration chip,the mathematical model of the heating system was established,and its parameters are identified.The experimental curve is compared with the identification curve,which proves the correctness of the identified mathematical model.(4)It is found that the traditional control algorithms including PID(Proportional Integral Derivative),fuzzy adaptive PID and time-optimal PID are not ideal for the temperature control of the PCR instrument through simulation and experimental analysis.Therefore,a robust PID is proposed,which is optimized using multi-objective particle swarm optimization.Simulations and experiments show that the overshoot of the robust PID is smaller with respect to the above three methods.The temperature rising rate 4.5?/s,the cooling rate 4.3?/s,the overshoot 0.58%,and the temperature accuracy±0.2? are achieved by the proposed method and the designed hardware.