Freeze Dryer Temperature Control System Of The Algorithm

The Freeze-drying method is the most advanced drying technologies. Mate-rials is placed in the frozen and dried vacuum condition that can avoid products oxidation of degeneration, deformation or loss of vitality and can maintain the original color and flavor raw materials,nutrient less losses after re-watering. As the freeze-dryer requires large investment and process cycle becomes long, some disadvantages such as energy consumption, limiting the use of freeze-drieding technology. However, with the freeze-dried products becomes light, long-term storage, transportation cost reduction. At present, the drugs, biological products, precious, and some high-tech products of food production and processing, the freeze-drying technology plays an irreplaceable role in the use of freeze-dryer. Freeze-dryer is a cooling system that is composed of several parts,such as thermal compensation system, temperature control system, drive control system etc., each part must to be meet the demand and coordination. The shelf tempera-ture control is the key to the whole control system using circulating heat medium method to achieve the heat exchange which produces a obvious lag property.Freeze-dryer temperature control system as a one-order large time delay control system, the process of running has more complex interference factors, freeze-dring product quality demand to more process. The traditional PID control method for large delay system control,due to delay timeτis much greater than 1, the result of Pade approximating is not satisfactory, in the late stage will have great oscillation and shelf temperature fluctuations, excessive fluctuations will destroy the composition of freeze-dried products,freeze-dried products can not be meet the high demand for quality. In this paper, freeze dryer temperature control systems have been studied, a series of Laguerre progression that improve algo-rithm by using the bilinear transform is proposed, Laguerre algorithm can be used in the limited band, it may be good approximation within the e-τs, it achieves the large time delay control system of freeze-dryer temperature.Control system hardware adopts to DSP320F2812 system, it is the center of control system, this text designs constant-current source platinum resistance tem-perature sensor, DSP is used in integrated internal ADC over-sampling of tem-perature data, After smooth work is treated as an algorithm input, Laguerre algo-rithm run on DSP by means of Programming. Through the drive circuit completes a lot of control, such as the chillers, circulating pumps and various valves, it will control the pre-freeze, vacuum, defrost, signal acquisition and control algo-rithms by programming to improve the degree of automation about freeze dryer control system.