Control of a Conical Bearingless Permanent Magnet Synchronous Motor
Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
Final Report Abstract
In this project, the control of a conical bearingless permanent magnet synchronous motor is addressed. The investigations are validated experimentally on a test-bench. Its construction is part of the project. The bearingless prototype was already designed and built at the beginning of the project. The first part deals with the construction of the test-bench, necessary to evaluate the different control schemes investigated. A real-time PC connected to a FPGA card is used to perform the control as well as the signal processing. The computationally intensive mechanical control is done in the real-time PC, while the four field oriented controls, necessary for proper levitation and drive of the rotor, are implemented in the FPGA. Sensor cards are designed to generate suitable excitation signals for the eddy-current sensors as well as to extract the position information from the modulated signals. Several excitation shapes and signal processing are tested. Then a theoretical part follows with the derivation of the electromagnetic model of the motor. The electromagnetic forces and torque are derived from the analytical calculation of the air-gap magnetic fields and evaluated for the built prototype. The disturbances, that are inherent to this particular motor topology, are then developed analytically. Different control schemes are implemented and tested on the test-bench. Due to the simplicity of the voltage-current models, it is found that simple PI controllers and field oriented control schemes are sufficient for the current control. The mechanical model displays interactions of mechanical origin (gyroscopic effect) and magnetic origin (field superposition and field modulation due to rotor eccentricity). The mechanical control is first derived with PID controllers, and the limitations of this approach are shown. Then the prototype is treated as a multi-input multi-output system and is decoupled with full-state feedback control in order to obtain good performances. Finally the magnetic disturbances are validated experimentally. It is shown that a proper control setting is able to operate in the presence of disturbances. This project demonstrates that a doubly conical bearingless motor can be easily treated as a permanent magnet synchronous motor from the electrical point of view and as a drive with magnetic bearings from the mechanical point of view.
Publications
- “Observer-based pole placement control for a double conical high-speed bearingless permanent magnet synchronous motor”, Proceedings of the 19 th European Conference on Power Electronics and Applications EPE’16, pp.1-10, September 6-8, 2016, Karlsruhe, Germany
G. Messager, A. Binder
(See online at https://doi.org/10.1109/EPE.2016.7695264) - Bearingless permanent magnet synchronous motor configurations and controls for high-speed drive applications, Dissertation, TU Darmstadt, 2017
G. Messager
- “Derivation of forces and force interferences in a double conical high-speed bearingless permanent magnet synchronous motor”, IEEE International Electric Machines and Drives Conference (IEMDC), 2017, May 21-24, 2017, Miami, Florida, U.S.A.
G. Messager, A. Binder
(See online at https://doi.org/10.1109/IEMDC.2017.8002213)
