An observer design for a poppet type pressure reducing valve

This paper presents an observer design that may be used to improve the response and stability characteristics of a solenoid operated pressure-reducing valve. Most pressure-reducing valves have very little inherent damping, and can potentially exhibit unstable behavior due to fluid velocity effects during the opening of the poppet. One solution is to improve the dynamic characteristics of the valve by using a closed-loop control strategy. Here, the solenoid current, poppet position, the poppet velocity and the control pressure are feedback signals, used to increase the stability margin and the response time. The cost of the sensors and problems associated with taking derivatives make direct measurement infeasible. We propose to obtain estimates of the poppet position and poppet velocity from only measurements of the valve control pressure and the solenoid current. This is done using a state observer that estimates the poppet position and the poppet velocity without calculating derivatives. These estimates may then be used in a feedback controller that is designed to meet the valve transient response specifications.