â liquefied natural gas (lng) is the most economical way of transporting natural gas (ng) over long distances. liquefaction of ng by using vapor compression refrigeration system requires high operating and capital cost. due to lack of systematic design methods for multistage refrigeration cycles, the conventional approaches of determining optimal cycle configuration are mostly based on trial-an...

At present, the cascade PID control is widely used to control the superheating temperature (main steam temperature). As Main Steam Temperature has the characteristics of large inertia, large time-delay and time varying, etc., conventional PID control strategy cannot achieve good control performance. In order to overcome the bad performance and deficiencies of main steam temperature control syst...

During the rough marine environment, heave compensation is used to offset motion of vessel when a crane lifts and lands load. Thus, load are realized decoupled. In previous studies, interference items such as hydraulic cylinder friction, underwater drag force nonlinear friction in active system compensated concentrated be estimated. this paper, we disassembled items; disturbance observer adapti...

during the last years the total cost of lng technology has decreased significantly due to improvements of the liquefaction process. however, many liquefaction plants that are still in operation use a three-cascade refrigeration system. in this paper, an advanced exergetic analysis is applied to better understand the operation of a three-cascade refrigeration system for liquefaction of natural g...

In most modern manufacturing systems, products are often the output of some multistage processes. In these processes, the stages are dependent on each other, where the output quality of each stage depends also on the output quality of the previous stages. This property is called the cascade property. Although there are many studies in multistage process monitoring, there are fewer works on prof...

In this paper, we introduce cascade normal forms for underactuated mechanical systems that are convenient for control design. These normal forms include three classes of cascade systems, namely, nonlinear systems in strict feedback form, feedforward form, and nontriangular quadratic form (to be defined). In each case, the transformation to cascade systems is provided in closed-form. We apply ou...