Control Strategy Of Thermoelectric Refrigeration And Its PLC Realization

Semiconductor lasers have been widely used since they were invented,but its performance and life are greatly subjected to the influence of operation temperature,hence the temperature of semiconductor laser must be accurately stabilized.Traditional cooling methods can no longer meet the heat dissipation of semiconductor laser,however,as an active cooling method,thermoelectric refrigeration can achieve efficient thermal management of semiconductor laser if a appropriate control strategy is used.In this thesis,the thermoelectric refrigeration temperature control simulation model is established to study the influence of different control strategies on the accuracy of temperature control at different ambient temperature and set temperature,including PID control,fuzzy control,fuzzy PID compound control and fuzzy adaptive PID control.The simulation results show that the fuzzy PID compound control has high temperature control precision,but it need 25 minutes to achieve this temperature control accuracy,the response time is relatively long,so it is not suitable for the practical application.The temperature control precision of other algorithms can meet the requirements of the semiconductor laser,which is ±2℃,and they only takes a few seconds to reach the target temperature,the response speed is relatively fast.According to the simulation results,control strategies presented above are realized by means of SIEMENS series PLC,the temperature control system of semiconductor laser based on thermoelectric refrigeration is also established,and the actual temperature control effect at different ambient temperature and set temperature of PID control and fuzzy control is studied.The experimental results show that the PID control and the fuzzy control both can meet the precision requirement of the semiconductor laser,which is ±2℃.However,with the increase of heat load of semiconductor laser,the response time of PID control increased from 80 s to 100 s,the accuracy of temperature increased from 0.9 to 2.15 ℃,while the response time of fuzzy control is still 60 s,the temperature control accuracy increased from 1.62 to 2.16℃.So the appropriate temperature control strategy should be chosen according to the thermal load of the semiconductor laser,when the heat load is small,the temperature control effect of PID control is better;when the heat load is moderate,the temperature control effect of PID control and fuzzy control is nearly same;when the heat load is large,the temperature control effect of fuzzy control is better.