Distributed Actuation and Control for Morphing Structures

  • Guanyu Lai

Student thesis: Doctoral ThesisPhD

Abstract

It is believed that structures and actuation systems should be tightly integrated together in the future to create fast moving, efficient, lightweight dynamic machines. Such actuated structures could be used for morphing aircraft wings, lightweight actuated space structures, or in robotics. This requires actuators to be distributed through the structure. A tensegrity structure is a very promising candidate for this future integration due to its potentially excellent stiffness and strength-to-weight ratio, and the inherent advantage of being a multi-element structure into which actuators can be embedded. Development of these machines will utilise expertise in several fields, involving kinematics, dynamics, actuation and multi-axis motion control.The research presented in this thesis concerns the study of multi-axis actuated tensegrity structures. A form-finding method has been developed to find stable geometries and determine stiffness properties of the type of tensegrity structure proposed. It has been shown that a tensegrity structure, with practical nodes of finite size, can be designed with actuated members to give shape-changing properties while potentially allowing a good stiffness to mass ratio. An antagonistic multi-axis control scheme has been developed for the tensegrity structure. The describing function technique has been used to analyse the dead band controller in the control scheme, giving a stability criterion.An experimental actuated tensegrity system has been designed and built incorporating pneumatic muscles controlled by switching valves. Mathematical models for the experimental actuated tensegrity system have been developed in detail, including the pneumatic actuation system and the structure geometry. The dynamic behaviour of the tensegrity system has been investigated via several simulation studies, using the developed models and the proposed control scheme. Experimental validation has been successfully conducted. The multi-axis control scheme can accurately control the tensegrity structure to achieve shape changes while maintaining a desired level of internal pre-load. The mathematical models can be used as a basis for further development.
Date of Award13 Dec 2017
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorAndrew Plummer (Supervisor) & David Cleaver (Supervisor)

Keywords

  • Tensegrity
  • Distributed actuation
  • Form-finding
  • Multi-axis control
  • Structural dynamics
  • Morphing
  • Variable geometry
  • Modelling
  • Simulation

Cite this

Distributed Actuation and Control for Morphing Structures
Lai, G. (Author). 13 Dec 2017

Student thesis: Doctoral ThesisPhD