Build and control of an inverted pendulum

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

Building and controlling an inverted pendulum was a real mechatronic challenge that required interdisciplinary solutions and as such, provided a decent basis to implement the theoretical knowledge acquired during my university studies into practical realization.

Balancing a pendulum on a cart in its unstable equilibrium point is a popular control theory challenge due to its non-linear mathematical model and highly unstable nature that provides opportunity to observe the performance of a chosen control algorithm. However the most essential part of the project was the controller design, it provided several challenges in other fields as well.

A simple yet functionally satisfactory mechanism was designed and built. Based on it the mathematical model of the system could be derived using the Lagrangian method. An LQR controller suitable for the task was designed. The system was actuated by an H-bridge driven DC motor thus the control signal had to be converted to duty cycle. Adequate measurements of the state variables were carried out. The system was simulated in Simulink and the control algorithm was also generated from a Simulink model to C code and loaded on a microcontroller suitable for the project. The simulated and measured results were compared.

Based on this comparison the project can be considered to be successful as the control algorithm was able to maintain the pendulum in its upper position while regulating the cart to its initial position.


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