Design of a Radially Segmented Halbach Multipole Magnet

As high pointing accuracy spacecraft are being subjected to more stringent requirements on their micro-vibration environment, the reduction and mitigation of these disturbances has become of great importance. The reaction wheel assembly significantly impacts this environment, and as such improvements in bearing technologies have the greatest...

A Novel Hybrid Analytical Model of Active Magnetic Bearing Considering Rotor Eccentricity and Local Saturation Effect

To facilitate the active magnetic bearing (AMB) design and analysis, an accurate and fast model that considers both rotor eccentricity and the saturation effect is necessary. In this article, a novel hybrid analytical model (HAM) for effective calculation of the magnetic field of the AMB is proposed. Eccentricity and local saturation are...

Driver Circuit Design for a New Eddy Current Sensor in Displacement Measurement of Active Magnetic Bearing Systems

Position sensing is one of the crucial parts of the active magnetic bearing (AMB) system. The printed circuit board (PCB) eddy current position sensor is a new type of position sensor for the AMB system, which makes a compact structure, high sensing quality, and is low cost. In this article, an improved driver circuit is proposed for this new...

Performance comparison of analytical models for rotor eccentricity: A case study of active magnetic bearing

This paper applies two different analytical methods, i.e., the perturbation method and superposition method, to calculate the magnetic flux density distribution and the magnetic force of the active magnetic bearing (AMB) with the rotor eccentricity. These two methods are thoroughly analyzed, compared and validated by the finite element model ...

Sliding mode control with neural network for active magnetic bearing system

A novel controller design procedure is proposed for a 5-degree-of-freedom (DOF) active magnetic bearing (AMB) system, based on sliding mode control (SMC) and neural network (NN). The SMC is used to achieve high robustness and fast response while the NN can compensate unmodeled uncertainty and external disturbance by on-line tuning algorithm. The...

Model-based Process Monitoring and Control of Micro-milling using Active Magnetic Bearings

The process of micro-milling is a promising technology for the fabrication of micro-parts with arbitrary 3D features in a wide range of materials. However, as a result of the reduced dimensions, the susceptibility of the process for machine tool errors and vibrations is higher, having adverse effects on accuracy and surface quality of the...

Design of a Micro Milling Setup with an Active Magnetic Bearing Spindle

This thesis describes the design of a micro milling setup with an active magnetic bearing spindle. Micro milling is the mechanical removal of material with sub millimeter tools. An active magnetic bearing typically consists of a set of magnetic actuators, a control loop and position sensors. Active Magnetic Bearings enable a very high rotational...

Control of magnetic bearings in wind turbines

Direct drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered. In the beginning, the thesis discusses the problems of direct drive...

Investigation on the Possible Use of Magnetic Bearings in Large Direct Drive Wind Turbines

A direct drive generator used in wind turbine has high energy yield compared to other drivetrain topologies and low maintenance is expected as the technology matures. On the other hand direct drive generator weight and size increases rapidly when scaled up to larger units. This paper will investigate the possibility of weight reduction of large...

Designing a position sensor system for Active Magnetic Bearings

In this thesis report, two sensor systems for measuring the position of a levitated spindle are proposed. An off-the-shelf optical sensor is used and the results of the implementation are discussed. Furthermore a capacitive sensor system is designed, consisting of a capacitive ring, sensor plates and signal conditioning. Testing shows both of...

Controller design for a magnetically levtitated spindle system

In this thesis, a complete design strategy is presented for the control of a magnetically levitated spindle. The spindle is levitated by electromagnets located at the spindle ends. Two approaches are used in obtaining a stabilizing control system for this naturally unstable plant. The first approach is to model the spindle as two independently...

Mechatronic design of a magnetically suspended rotating platform

A novel Planar Magnetic Bearing and Motor Configuration applied in a Positioning Stage

This thesis presents the design and implementation of a fully contactless high precision magnetically suspended position stage with large planar stroke. This stage is the first which is suitable for practical application in vacuum. The underlying electromechanical working principles, modelling and analysis, the mechanical and electrical design,...

Combined electromagnetic suspension and propulsion for positioning with sub-micrometer accuracy

Testing and investigations of reaction wheels

The first part of the paper presents the results of measurements on torque and force irregularities of running reaction wheels. Six different, current technology European wheels, both with ball- and magnet bearings, and with d.c. and a.c. drive motors are examined. Time-domain behaviour around zero wheel speed as well as noise at certain...