Magnetic Levitation Control System
Multidisciplinary Mechatronics Project
I tailored my master's degree in mechanical engineering to learn how to build sufficiently stable and robust mechatronic systems. In this project, I worked on a multidisciplinary team to design a system capable of levitating small metal objects.
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Operating Principle: Light (shown as the orange beam to the right) is emitted from a photodiode and received by a phototransistor. The computer is programmed to detect changes in the amount of light that passes by the levitating ball. When the phototransistor receives more light (ball is falling and lets more light pass), a command is sent to the actuator driver to increase the strength of the magnet to pull the ball back up into an equilibrium state. When the phototransistor receives less light (ball is rising and covers the beam), a command is sent to the actuator driver to decrease the strength of the magnet to let it fall down to an equilibrium state. The control system is designed to optimize the system's robustness to disturbances (vibrations) and performance to minimize oscillations.
Photo Diode
Photo Transistor
Electromagnet
Light Beam Detecting Change in Position
Levitating Ball
Block Diagram: All the components in the closed-loop feedback system are modeled in the block diagram by transfer functions, transfer of information, and transfer of power. Feedforward control was used to set the ball at its desired equilibrium position. A Lead controller was used as the feedback controller to keep the system stable. Controllers were designed using root locus methods with SISOTool from the Control Systems Toolbox in MATLAB.
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Simulink Model: To make sure the system dynamics were correct before testing the physical system, a model in MATLAB/Simulink was created to model the levitating system.
What I Learned
I learned how to design a controller to make an inherently unstable system stable. This requires comprehensive knowledge of the system parameters and tuning of the feedback controller to meet all the performance criteria.