Bounded Control Essay

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Bounded control literally refers to the control of a system within certain bounded variables. This type of control method seeks to define certain limits that correspond to the physical limit of the variable in question. The variables often considered are that of the amplitude of the actuators. This is to avoid the possibility of an irreversible damage to the actuator. See subsec.~\ref {subsec:Sub-Problem 4}. This concept was used in (\citet*{guerrero2011bounded}) and adequately described in (\citet* {flikop2004bounded}). (\citet*{rifai2011bounded}), proposed a bounded control method based on nested saturations for the rehabilitation of the knee joint. By "nested saturation"; it means that the actuator is subjected to magnitude and rate saturation…show more content…
In order to accomplish this task, two (2) applications were considered. The first application seeks to drive the knee-ankle orthosis to follow a predefined rehabilitation trajectory with and without human contribution. To verify the level of contribution of the human the system may allow, a high gain observer is designed for this purpose. Although high gain observers as been extensively used for the recovery of states such as in (\citet*{wang2003observer}), here, the recovered states were employed to verify the level of human contribution. The stability of the closed-loop system without human contribution is verified using Lyapunov-based analysis. The convergence of the error between the states of the wearer-exoskeleton and that of the high gain observer is also analysed using Lyapunov stability theory. In the second application, the system is used to drive a full-body exoskeleton with four (4) actuated joints in its lower limb (Hips and Knees) to follow a CPG-based human gait. The CPG-based human gait is modified using polynomial functions to allow the selection of initial conditions for the human-exoskeleton. Simulation and the eventual results were obtained via MATLAB/SIMULINK. The performance of the system was discussed
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