Distributed Actuation and Control of Smart Structures

Abstract

The aim of future dynamic machine development is to make them lighter, move faster, use less energy, be more human-friendly, and be more adaptable. A promising solution is distributed actuation integrated with load-bearing structures, which can potentially provide better static and dynamic performance, redundancy and more adaptability than current designs. Such structures can be referred to as smart structures. A morphing aircraft wing is a good example for the application of smart structures, which is deemed to provide better aerodynamic performance and higher wing efficiency than conventional designs. A tensegrity structure is a strong candidate for this integration due to its potentially high stiffness-to-mass ratio and inherent advantage of being a multi-element structure, into which actuators can be embedded.
The research presented in this thesis concerns the study of a smart structure, and its integration with a morphing aircraft wing. A structure design method has been developed for an active tensegrity structure. The high external load level and actuator size constraints are the main challenges at the design stage. A case study design for a smart structure integrated in a morphing wing to be tested in the University of Bath wind tunnel is presented. A forward kinematic calculation method has been developed to transform the actuator axial displacements to structure shape changing degree of freedom (DOF) form. Six actuators and four shape-changing DOF are considered in the analysis, and two internal load paths are also under closed loop control. An antagonistic multi-axial control scheme has been developed for the smart structure, which is capable of motion and internal force control.
An experimental smart structure prototype has been built, along with the morphing wing assembly. Pneumatic cylinders are embedded into the structure; switching valves are selected for the pneumatic control. A simulation model is developed for the prototype, including a dynamic model for the pneumatic system and a multi-body simulation for the structure. The dynamic behaviour of the smart structure has been investigated via a series of simulations and experiments. The wind tunnel test results have demonstrated that the prototype morphing wing is capable of accurate shape- changing control, and offering reasonable aerodynamic performance, while maintaining a desired level of internal load in a stiff structure, with different wind speeds.

Date of Award	2 Oct 2019
Original language	English
Awarding Institution	University of Bath
Supervisor	Andrew Plummer (Supervisor) & David Cleaver (Supervisor)