Energy harvesting vibration absorbers (EHVAs) represent a novel type of vibration absorbers where the dissipated energy is harnessed in the absorber system. Conventional optimization-based methods can be utilized for optimal design of EHVAs, but this usually involves in iterative design procedures, particularly for approaching performance limits. In this note, a visualization technique is proposed. The problem of existence and uniqueness solutions is addressed; the intimate relationship between energy harvesting and vibration suppression performances is disclosed; and the fundamental issue of determining performance limit with this visualized method is solved. These features form solid contributions of the current proposal over those optimization-based design methods. The corresponding design procedures are illustrated and the claims are further validated through real-time simulations to the optimal design of EHVAs.

The inherent nonlinear nature of engine dynamics necessitates advanced design techniques for transient control. Conventional design methodologies are either not ready to apply to large flight envelope control or failing to provide protection over a variety of physical limits. This paper proposes an active set-based method for performance optimization over large envelope while providing limit protection over all sorts of constraints. Detailed design procedures are provided, and extensive numerical investigations are presented with both robustness and implantation issues discussed. Comparisons with both conventional schedule-based control and an advanced nonlinear generalized minimum variance-based (NGMV) control are conducted to illustrate the effectiveness of the proposed method.

Control design for multivariable nonlinear systems has cultivated into a mature research area. A variety of control design methodologies have been well established. In most of the approaches, however, it is implicitly assumed that an analytically mathematical model can be available. This is not always feasible since in many practical control problems, system dynamics may be represented by nonanalytical modules, such as look-up tables, c or Fortran codes, etc. As a consequence, conventional methods can only be performed after analytical models are obtained. In this paper, an approach is proposed where the nonanalytical modules can be handled directly. Important results are obtained on optimal control laws and their implementation; robust control is achieved using a new online tuning method; input saturation and stability issues are also discussed. A numerical study is provided to validate the effectiveness of the proposed method.

Nonlinear control of aircraft engines has attracted much attention in consideration of the inherent nonlinearity of the engine dynamics. Most of the nonlinear design techniques, however, require the information from the rotational speeds of both high-pressure compressor and fan. This is not desirable from engine health management perspective, and this paper proposes a single sensor measurement and single actuator control approach. The proposed method can provide fast regulation of engine speed in a finite-time in comparison with conventional infinite time stability. Important results are obtained on both controller design and disturbance tolerance. Numerical examples are provided for validation of the proposed finite-time controller, demonstrating fast regulation property and remarkable disturbance tolerance capability.

Model-based design has attracted much attention in the field of aircraft engine control in recent years. As an aircraft engine is a complicated thermomechanical system, it can only be represented by a nonlinear process model. This necessitates the study of the nonlinear control techniques. Based on our recent results, this paper proposes a novel design approach based on a generalized Gronwall-Bellman lemma. Important results are obtained on bounding behavior of the nonlinear states of the engine. The proposed method is easy to design and tune with the appealing feature of enlarging the feasible control envelope. Finally, a simulation study is provided to validate the effectiveness of the control design approach.