Classical and Advanced Controllers for Ideal Halbach Magnetic Lead Screw for Ocean Wave Energy Applications

A magnetic lead screw (MLS) uses the magnetic field of permanent magnets to convert between linear and rotational motions while achieving a gearing action. This mechanism converts low-speed, high-force linear motion to high-speed, low-torque rotational motion. The MLS is ideal for wave energy applications, where the low-speed oscillatory motion of waves can be converted into usable electrical energy. It harnesses the high-force, low-speed linear motion of waves and converts it into rotational motion for generators, all while maintaining contact-free power transfer, reducing maintenance and machine size compared to linear machines. In this study, two controllers are proposed for an ideal Halbach magnetic lead screw: a proportional-resonant (PR) controller and an observer-based state feedback controller (O-SFC). The proportional-integral (PI) controller is also presented as a benchmark. These controllers are developed based on the linearized model of the ideal Halbach MLS and validated through simulation studies of its non-linear model. Results show that both the PR and O-SFC controllers significantly improve system performance compared to the PI controller, with the O-SFC providing superior performance over both the PR and PI controllers.