Magnetic Levitation

For the course ME C134/EECS C128, one of the labs we did was levitating a steel bearing with analog control (i.e. no computers). The goal was to levitate a bearing statically using an op amp, which is by definition, a PID controller. The respective gains can be tuned, which was the essence of the lab.

In this lab, my lab partners, Vineet Nair and Hadi Zhang, aimed to design an analog controller (using MATLAB) for the magnetic levitation system (linearized model) whose parameters we identified, and then implement this physically using circuit elements and hardware. Our design goal was an analog compensator such that the open loop system’s DC gain (the product of compensator gain as well as the plant) was 2 A/m, controller pole/zero ratio was roughly 20 and the phase margin was approximately 60 degrees.

The controller for this lab utilized an op amp for the analog control. In particular the design phase allowed for choosing the location of the poles of the PID controller. The poles initially selected/designed for did not work for the system. Interestingly, I would later learn about H-infinity loopshaping from Andy Packard and understand the lack of robustness in the classical control methods taught in EECS C128.