Team Mechatronics project: Simulation of a Humanoid Leg
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The project undertaken consisted of the analytical and simulation of an under-actuated, humanoid, robotic leg. The leg was modelled using physical and mathematical laws which incorporated an electrical circuit, a DC motor and equations of motions for the behaviour of the leg. The model was then converted into a block diagram using Simulink in Matlab. An open loop model was generated initially, and the responses to a variety of inputs were produced and analysed. The linear model was also developed using the linearization tool on Matlab. Analysis on both of these sets of models was undertaken, and the conclusion that the system produced a divergent model was made.
From these results, a decision that control needed to be added to the system, in order to achieve the performance specification that were required from the modelled system. A full stability analysis was then undertaken on the linear and non-linear models of the open loop system. It was discovered that the open loop system had a neutral stability due to the zero poles in the characteristic equation. The responses for three different controllers: a proportional-integral-derivative controller, a pseudo-derivative-feedback controller and a controller based on the root locus technique were established using Simulink, based on the original open loop model.
The results of the simulation were produced using Simulink. These results sets were recorded and compared by the rise time, settling time, overshoot percentage, and the gain- and phase margins, in order to select the most suitable controller for the model based on set points and preferred parameters. The PID controller was selected to be the most suitable controller, as it would be the most robust controller, the overshoot values of the controller were the smallest and the gain- and phase margin of the controller were the most favourable overall.