This study brings forward backstepping control based on nonlinear control strategy as a possible way to implement close-loop speed-control based on the characteristic of fans load.

This paper presents a new concept of asymmetrical valve controlled asymmetrical cylinder,makes new definition of load flow and load pressure,thus illustrated static and dynamic properties of asymmetrical cylinders,derives its transfer function and block diagram,which can be universally applied to all kinds valve controlled cylinder and may be a meaningful guide to the design of such servo systems.

According to the working characteristics of the pump and valve combined EHA (Electrical Hydraulic Actuator), the method to improve the system efficiency by increasing the design value of load pressure was proposed.

To test the output volgage and load voltage using the sensor in DC/DC converter, this paper presents a novel method of using state observer to estimate the output voltage and output load voltage of DC/DC converter.