Design and optimisation of a reconfigurable exoskeleton for ankle rehabilitation

The EPSRC (Engineering and Physical Sciences Research Council) decided to fund a project which aims to deliver innovative rehabilitation through an exoskeleton which is modular and reconfigurable, to meet individual needs and have the required intelligence to monitor recovery, personalise treatments and deliver effective rehabilitation in stroke patients' own homes. The work of thesis has been carried out at King’s College in London, where a team worked on the different parts which make up the exoskeleton, namely hip, knee and ankle. The device that models the human ankle is the topic of this thesis, the content of which can be summarized as follows. After an introduction, in Chapter 2 a novel 2-UPS-UPRU/S mechanism (where P, R, U, S stand for prismatic, revolute, universal and spherical joint, respectively) which models the human ankle as a spherical joint, is introduced. This device is proposed to cover those rehabilitation tasks which see the patient as sitting or lying down. The direct and inverse kinematic problems are solved, and the singularity analysis is carried out. Furthermore, the calculation of the mechanism stiffness matrix via screw theory is presented. In Chapter 3, the requirements for walking are highlighted. This lays the groundwork to introduce the reconfiguration process described later in this chapter, which enable the transformation of the 2-UPS-UPRU/S into the UPS-UPU/S mechanism. This latter is intended for weight bearing tasks, including walking. Then, the CAD model of both devices which consider problems such as interference between elements and joint angle limitations is presented. The mobility analysis of the UPS-UPU/S device will be addressed by means of screw theory in Chapter 4. This part also, deals with the kinematic, singularity and stiffness analyses of the mechanism. In each chapter, calculations have been carried out using MATLAB software. Conclusions and future developments are covered in Chapter 5.