In this paper, we propose a retrofit control method for stable network systems. The proposed approach is a decentralized control method that, rather than an entire system model, requires a model of the subsystem of interest for controller design. To design the retrofit controller, we use a novel approach based on hierarchical state-space expansion that generates a higherdimensional cascade real...

In this note, 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 our...

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...

This paper focuses on simultaneous relay auto tuning of open loop unstable parallel cascade systems. For stable parallel cascade systems,Vivek and Chidambaram[1] had discussed effect of higher order harmonics of symmetrical relay output, which accounts for error in ultimate controller gain estimation. In the present work, this method is extended to parallel cascade controllers for open loop uns...