Space vectors and pseudo inverse matrix methods for the radial force control in bearingless multi-sector permanent magnet machines

Two different approaches to characterize the torque and radial force production in a Bearingless Multi-Sector Permanent Magnet (BMSPM) machine are presented in this work. The first method consists of modelling the motor in terms of torque and force production as a function of the stationary reference frame α-β currents. The current control reference signals are then evaluated adopting the Joule losses minimization as constrain by means of the pseudo inverse matrix. The second method is based on the control of the magnetic field harmonics in the airgap through the current Space Vector (SV) technique. Once the magnetic field harmonics involved in the torque and force production are determined, the SV transformation can be defined to obtain the reference current space vectors. The methods are validated by numerical simulations, Finite Element Analysis (FEA) and experimental tests. The differences in terms of two Degrees of Freedom (DOF) levitation performance and efficiency are highlighted in order to give the reader an in-depth comparison of the two methods

Power-Sharing Control in Bearingless Multi-Sector and Multi-Three-Phase Permanent Magnet Machines

This paper deals with the power-sharing control of bearingless multi-sector and multi-three-phase permanent magnet machines. The proposed control strategy allows to distribute the power flows among the three-phase inverters supplying the machine during bearingless operation of the drive. The control technique is based on the extension of the vector space decomposition modeling approach. The components producing the electromagnetic torque, i.e. the q-axis currents, are controlled independently from the d-axis ones, also with the aim of managing the power flows among the three-phase systems. Conversely, the d-axis currents are exploited for the generation of the radial forces needed to levitate the rotor, while considering the compensation of the forces caused by the q-axis currents in case of unbalanced power sharing strategy. The validity of the proposed method is confirmed by simulations and experimental tests on a prototyped bearingless multi-sector permanent magnet synchronous machine. The proposed approach is a contribution to the development of advanced control systems employing multiphase drives in the field of bearingless and multiport applications

Radial force control of multi-sector permanent magnet machines for vibration suppression

Radial force control in electrical machines has been widely investigated for a variety of bearingless machines, as well as for the conventional structures featuring mechanical bearings. This paper takes advantage of the spatial distribution of the winding sets within the stator structure in a multisector permanent-magnet (MSPM) machine toward achieving a controllable radial force. An alternative force control technique for MSPM machines is presented. The mathematical model of the machine and the theoretical investigation of the force production principle are provided. A novel force control methodology based on the minimization of the copper losses is described and adopted to calculate the d–q axis current references. The predicted performances of the considered machine are benchmarked against finite-element analysis. The experimental validation of the proposed control strategy is presented, focusing on the suppression of selected vibration frequencies for different rotational speeds

Modular Power Sharing Control for Bearingless Multi-Three Phase Permanent Magnet Synchronous Machine

This paper proposes a modular approach to the power sharing control of permanent magnet synchronous bearingless machine. The selected machine topology features a winding layout with phases distributed into non-overlapping three phase groups, a solution whose twofold aim is to increase the fault tolerance and to allow for the radial force generation. The three phase sub-windings are supplied by standard three-phase inverter, leading to a modular system architecture. A throughout explanation of the methodology used to develop the control algorithm is presented considering the torque and force control in combination with the power sharing management of the machine. Special emphasis is also placed on validating the modelling hypotheses based on a finite element characterisation of the machine electro-mechanical behaviour. The proposed control strategy is also extended to cater the possibility of one or more inverters failure, thus validating the intrinsic advantage of the redundancy obtained by the modularity of the system. An extensive experimental test campaign is finally carried out on a prototyped multi-three phase permanent magnet synchronous drive. The obtained results validate the bearingless power sharing operation in healthy and faulty scenarios, both at steady state and under extreme transient condition

Multiphase electric drives for "More Electric Aircraft" applications

Advances in power electronic and machine control techniques are making the inverter-fed drives an always more attractive solution. Because of the number of inverter legs is arbitrary, also the number of phases results as a further degree of freedom for the machine design. Therefore, the multiphase winding is often a possible solution. Due to the increasing demand for high performance and high power variable speed drives, the research on multiphase machines has experienced a significant growth in the last two decades. Indeed, one of the main advantages of the multiphase technology is the possibility of splitting the power of the system across a higher number of power electronic devices with a reduced rating. A similar result can be obtained by using multi-level converters. However, the redundancy of the phases leads to an increased reliability of the machine and to the introduction of additional degrees of freedom in the current control and the machine design. This work aims to study and analyze the highly reliable and fault tolerant machines. It proposes innovative solutions for multiphase machine design and control to meet the safety-critical requirements in “More-Electric Aircraft” (MEA) and “More Electric Engine” (MEE) in which thermal, pneumatic or hydraulic drives in aerospace applications are replaced with electric ones. Open phase, high resistance and short circuit faults are investigated. Fault tolerant controls and fault detection algorithms are presented. Radial force control techniques and bearingless operation are verified and improved for various working scenarios. Fault tolerant designs of multiphase machines are also proposed

Control System Commissioning of Fully Levitated Bearingless Machine

The bearingless permanent magnet synchronous motor (BPMSM) is a compact motor structure that combines the motoring and bearing functions based on well-designed integrated windings for generating both torque and magnetic suspension force. In order to achieve a successful high-performance control design for the BPMSM, an adequate model of the rotor dynamics is essential. This paper proposes simplified multiple-input and multiple-output (MIMO) control approaches, namely the pole placement and the linear-quadratic regulator (LQR), that allow to carry out identification experiments in full levitation. Additionally, the stability of the MIMO levitation controller is verified with the rotation tests. Compared with other recently published works, the novelty of this paper is to experimentally demonstrate that a stable fully levitated five-degrees-of-freedom (5-DOF) operation of a bearingless machine can be achieved by the proposed approach, and thereby, options for commissioning of such a system are obtained

Enhanced Availability of Drivetrain Through Novel Multiphase Permanent-Magnet Machine Drive

This paper deals with a novel multiphase permanent-magnet (PM) machine drive to enhance drivetrain availability in electric traction applications. It describes the development of new winding configurations for six-phase PM brushless machines with 18 slots and eight poles, which eliminate and/or reduce undesirable space harmonics in the stator magnetomotive force. In addition to improved power/torque density and efficiency with a reduction in eddy current loss in rotor PMs and copper loss in end-windings, the developed winding configuration also enhances availability of drivetrain, in a variety of applications requiring a degree of fault tolerance, by employing it as two independent three-phase windings in a six-phase interior-PM machine, which is designed and optimized for a given set of specifications for an electric vehicle, under thermal, electrical, and volumetric constraints. This paper also describes the design and development of a six-phase inverter with independent control for both sets of three-phase windings. The designs of the motor and the inverter are validated by a series of preliminary tests on the prototype machine drive

A Review of Modeling and Diagnostic Techniques for Eccentricity Fault in Electric Machines

Research on the modeling and fault diagnosis of rotor eccentricities has been conducted during the past two decades. A variety of diagnostic theories and methods have been proposed based on different mechanisms, and there are reviews following either one type of electric machines or one type of eccentricity. Nonetheless, the research routes of modeling and diagnosis are common, regardless of machine or eccentricity types. This article tends to review all the possible modeling and diagnostic approaches for all common types of electric machines with eccentricities and provide suggestions on future research roadmap. The paper indicates that a reliable low-cost non-intrusive real-time online visualized diagnostic method is the trend. Observer-based diagnostic strategies are thought promising for the continued research

44th Aerospace Mechanisms Symposium

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms

Energy. A continuing bibliography with indexes, issue 18

This issue of Energy lists 1038 reports, journal articles, and other documents announced between April 1, 1978 and June 30, 1978 in Scientific and Technical Aerospace Reports (STAR) or in International Aerospace Abstracts (IAA). The coverage includes regional, national and international energy systems; research and development on fuels and other sources of energy; energy conversion, transport, transmission, distribution and storage, with special emphasis on use of hydrogen and of solar energy. Also included are methods of locating or using new energy resources. Of special interest is energy for heating, lighting, for powering aircraft, surface vehicles, or other machinery