Design and implementation of a control system for a powered reciprocating gait orthosis

Zaidan, AAR

Abstract

The University of Salford has developed a program in order to improve the control of
lower limb orthotics thus improving the ability of paraplegics to walk. Although the
system is greatly needed for rehabilitation it is hoped that the final system would enable
paraplegics to walk in the community. The present project, which is based on previous
designs such as the R. G. O (Reciprocating Gait Orthbsis), strives to add external power at
the hips of the R. G. O. The constructed prototype is made of a mechanical skeleton with
each leg driven by a brushless motor and a lead screw.
The main purpose of this project is to design a control system to control the motion of the
legs. The first step in achieving this task was to model the various components of the
system separately and then derive a model using system identification that will describe
the behaviour of the whole system.
The starting point was a mechanical device with two motors mounted one at either hip. A
full mathematical analysis of the system is carried out. Once a mathematical model is
derived for the RG. O with the two motors it can be used to carry out real time
simulations using MATLAB.
Once the model is derived it must be validated to make sure it is actually a mathematical
representation of the system. The identified model is usually very accurate as it is based
on the actual system performance. Then real time simulations of the theoretical and the identified model are compared. If the theoretical model behaves in the same way as the
identified model then it is validated and may be used for further work.
The models derived using system identification were validated and gave a good
comparison when compared to real data. A pole placement controller was designed and
tested based on these models. The controller performance was tested with the orthosis
unloaded, loaded with artificial loads (a plaster leg weighing 10 Kg). The controller
managed to follow the pre-set trajectory reasonably well. The orthosis was then tested
with a volunteer in it. Again the performance was very encouraging.
The fmal Project will be P. C driven System with the possibility of using NiCAD
Batteries as the power source. The main tools, which will be used in order to carry out
simulations and comparisons of theoretical and practical results, are MATLAB. The
software used was C.

Citation

Zaidan, A. Design and implementation of a control system for a powered reciprocating gait orthosis. (Thesis). University of Salford, UK

• Thesis Type: Thesis
• Deposit Date: Jul 7, 2009
• Publicly Available Date: Jul 7, 2009
• Additional Information: Additional Information : PhD supervisor: Professor John Grey
• Award Date: Nov 1, 2000