Construction of Devices in Bioartificial Liver Support System

An automatic control device in bioartificial liver support system is designed and implemented. Details of the hardware structure, design of the control system and the applied software in the device are described. Main controller uses the WS-843AW industrial control computer; precision electromagnetic valves are selected as implements to control the flux of three-gases (oxygen, carbon dioxide and nitrogen). The interconnected rule of controlled parameters in the system is analysed, and then matched by the mass balance equation. By a series of logic judgements of signals from sensors and direct digital calculations (DDC), a simple proportional plus integral (PI) controller can firstly manipulate the operations of electromagnetic valves, and then the on-line and off-line predictive control algorithm is used in accordance with practical experience to meet the requirements of the parameters in the culture and metabolism of hepatocytes. Software based on Visual C++ is implemented. All these serve to ensure high operational reliability, expansibility and better maneuverability of the whole system. Experiments show that this method can achieve sound performances in practice although there exist very strong coupling, dead-delay and lots of non-linear factors in the bioreactor. The controlling range is: dissolved oxygen 0-200plusmn5%; pH 6-8plusmn0.05pH; temperature 20-45plusmn0.1degC. The device can work in a steady state, and the control precision is high. It can meet the needs in the bioartificial liver support system, and hopefully improve clinical therapeutic effect