Modeling and simulation of high pressure cryogenic process for optimum closed loop control

The Proportional, Integral and Derivative (PID) Controller are widely used for process control. Using PID controller efficiently and the optimum tuning of its parameters is a significant research area. Computational Analysis and Control theory acts as powerful scientific tools for tuning the PID constants. In this paper high pressure cryogenics process is modeled using system identification tool. The process model is developed as second order plus dead time with zero order hold. The PID software is implemented in Programmable Logic Controller (PLC).The high pressure cryogenics systems are used in ground testing of rockets. The process model and controller model are used in SIMULINK to tune PID constants using simulations. Experimental trails are conducted with PID constant derived from simulation. Analytical approach is adopted for further fine tuning and to achieve optimum close loop control. Different ground tests are conducted for testing and qualification of rocket before flight. The SetPoint ( LH2/LOX Runtank Pressures) requirement changes in each test. The PID constants tuned by this methodology gave satisfactory results in closed loop mode and maintained the process variables (LH2/LOX Runtank Pressures) within tolerable band to meet the test objectives.