Future work

The research has potential applications in many industries and can be developed further into many directions of research. The basic theories for partial pole placement with inaccessible degrees of freedom and block decoupling vibration control in linear time invariant systems, and global robust flutter suppression in under-actuated nonlinear aeroelastic systems are developed and presented in this thesis. Also, semi- analytical and numerical investigation of the effects of softening nonlinearity on aeroelastic systems is presented. Other aspects that can be considered as further work may be summarised here:

1. The method of receptances, originally developed in [8, 9] and further developed in this thesis [128, 129], is based on the assumption of distinct eigenvalues in both open- and closed-loop systems. In practice, systems with closely spaced eigenvalues, which are close to being defective, are common. Developing the method of receptances in defective systems is an interesting line of research.

2. Experiments for block decoupling vibration control in large flexible smart structures with embedded piezo-based actuators and sensors may be carried out.

3. The Boeing Joined-Wing SensorCraft is a concept proposed to serve as a next-generation, high altitude, long endurance reconnaissance unmanned aircraft. Buckling is considered to be a critical constraint for its aeroelastic performance [149]. It is of significant importance to comprehensively

176

investigate the effects of softening nonlinearity experimentally, due to buckling of the aerodynamic responses of joined-wing sensor-crafts.

4. Experiments for robust passivity-based sliding mode control may be carried out on a nonlinear wing section at the University of Liverpool.

177 References

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