A new control strategy for hydraulic valve applications in oil field

For simplicity and economic reasons, many operational equipment in oil field are equipped with tri-state hydraulic valves as the prime control device instead of using some more sophisticated and precise hydraulic servo system. There are only three operating states for a tri-state valve, i.e., close, open and motionless. Quite often, these kinds of simple hydraulic valves are adopted to achieve high precision controls, such as flow rate control, cement density control, etc. It has been a great challenge for our control engineers. In this paper, a new control strategy is presented in the field of hydraulic valve control. It combines the classical fuzzy control theory and tri-state valve technology to form a discontinuous controller. This results a much more simplified and effective control algorithm, which has been used in many oil field applications. Also, a parameter optimization procedure based on nonlinear simplex method is presented to optimize the control parameters. Both simulation and field test results show the proposed control strategy is practical and effective