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A special magnetic geared tubular linear mo-tor which combines a tubular magnetic gear and a tubular linear motor for direct-drive applications is presented in this paper. The structure and operating principle of the machine are introduced, then magnetic flux distribution of the gear and thrust force generated by winding coils are simulated by using 2-D modeling. Finite-element calculation is used to confirm the accurate of results.

Thrust ripple and density greatly impact the performance of the linear machine and other linear actuators, causing positioning control precision, dynamic performance, and efficiency issues. Generalized pole-pair combinations are difficult to satisfy both the thrust and ripple for double salient reluctance linear machines. In this paper, a DC-Biased vernier reluctance linear machine (DCB-VRLM) is proposed to solve the abovementioned issues. The key to the proposed design is to reduce the ripple and enhance the thrust density with non-uniform teeth by utilizing and optimizing the modulated flux in the air gap. To effectively verify the proposed design, the DCB-VRLMs with different winding pole pairs and secondary poles are compared. The 12-slot/10-pole combination is chosen to adopt a non-uniform air gap structure. Moreover, the energy distribution of AC/DC winding is studied and optimized to further enhance the performance of the proposed DCB-VRLM. The results indicate that the DCB-VRLM with the non-uniform air gap has a lower thrust ripple, better overload capability, and higher thrust density, which confirms its superiority in long-stroke linear rail transit and vertical elevator applications.

This work presents a new wave energy converter power take off (PTO) system that combines two recent developments in drive train technology, the consequent pole linear vernier hybrid permanent magnet machine and the linear magnetic gear. The combined system is fully realised in three-dimensional finite element method and compared to a similar direct drive machine. While the resulting system is lighter, reducing the active material mass by 30%, and more efficient, the system requires larger amounts of high cost permanent magnet material and increased PTO complexity. It is summarised that while such a system could be recommended in certain conditions, it is not viable for general application.

Wave Energy Converters (WECs) generally use a Mechanical Power-Take-Off (MPTO) involving hydraulics or gearing to optimise the extraction of energy from the incoming waves before converting it into electrical energy via a high speed rotating generator. This simplifies the design of the Electrical Power Conversion System (EPCS). Further, it facilitates the use of mechanical energy storage such as hydraulic accumulators to reduce the peaky nature of the power flow and allows the WEC resonant frequency to be tuned for maximum energy capture. This work compares two power electronic converter topologies for an Electrical PTO (EPTO). This EPTO is intended to replace the aforementioned MPTO and generator with a Permanent Magnet Linear Machine (PMLM) directly coupled to the WEC. The compared topologies comprise either a Current Source Converter (CSC) or a Voltage Source Converter (VSC) as the generator interface working in combination with a DC-DC converter and an Energy Storage System (ESS). The principle differences between the two topologies are explored and losses are evaluated in a modular EPCS working with a WEC. Wide-bandgap power electronic switches are assumed for both topologies over a range of switching frequencies. The evaluation concludes that the CSC topology is advantageous at higher switching frequencies.

This article proposes a new topology of double-sided linear Vernier permanent magnet (LVPM) machine with segmented translator structure. A combination of a typical Halbach array consists of two horizontally magnetised permanent magnets (PMs) sandwiched between a salient iron tooth and adjacent vertically magnetised PM pole with the aim of improving its electromagnetic performance. The coreless partitioned translator contributes to a significant reduction in mass and the associated cost. With the aid of finite element analysis (FEA), two LVPM machines with the same PM, and stator volume have been investigated, analysed, and compared. The results imply that the proposed LVPM is capable of producing higher force density, while it exhibits lower cogging force and force ripple compared to its counterpart.

This study addresses double-sided stationary stators in a linear electric generator with similar operation to a linear oscillatory motion electric machine. The plate mover in the linear electric generator's double-sided stationary stators is powered by the acoustic power output of the thermoacoustic engine's acoustic line. The main originality of this structure resides in the linear guidance used for the moving part. The mover is made up of a plate of sandwich magnets between two stators. This plate is in magnetic balance between the two stators through a controlled friction device.

In this study, a linear synchronous machine is compared with a linear transverse flux machine. Both machines have been designed and built with the intention of being used as the power take off in a free piston engine. As both topologies are cylindrical, it is not possible to construct either using just flat laminations and so alternative methods are described and demonstrated. Despite the difference in topology and specification, the machines are compared on a common base in terms of rated force and suitability for use as a generator. Experience gained during the manufacture of two prototypes is described.

This study discusses the topology development of a cylindrical transverse flux linear machine for use with a free piston engine. Despite its three-dimensional flux path, the stator of this topology can be made from regular laminated components and only the translator includes soft magnetic composites. The detailed design development is discussed, including stator tooth combination, alternative winding, and fabrication techniques. Results from both finite element analysis and experimental measurement are compared, which gives a validation of the feasibility of the building process.

Different topologies of Vernier permanent magnet (PM) machines have been proposed for direct drive low-speed applications due to their high thrust and power density. However, this type of machine can suffer from low power factor (PF). In this study, a flux concentrated doubly salient linear permanent magnet machine with V-shape PM arrays is proposed and compared to a consequent pole (CP) type machine. Using the configuration of V-shaped PMs allows the flux to be concentrated in iron spacers located between two pieces of PMs. This feature is shown to result in an improvement of the airgap flux density, which allows a reduction in electrical loading and hence an improvement in power factor. In order to achieve a fair comparison, two doubly salient linear permanent magnet machines with different PMs’ configurations have been analysed and compared using transient FEA. The investigated machines have the same overall machine and, crucially, magnet volume. The results confirm that the proposed V-shape machine is capable of higher thrust force, higher no-load back EMF and can achieve a higher PF of 42% compared to the consequent pole machine, while it consumes the same amount of the PM material.

O motor linear à relutância variável (MLRV) é uma máquina elétrica alimentada em corrente contínua, com fases excitadas numa sequência determinada. Caracterizado por operar numa ampla faixa de variação de velocidade, é utilizado em aplicações lineares que convertem energia elétrica em força e movimento de translação. A necessidade de dispositivos comutadores de corrente e um sistema de controle requer boa estimativa do perfil de indutância do motor. No entanto, uma vez que o maior entreferro dificulta o cálculo analítico, este perfil deve ser obtido através de métodos numéricos. Neste contexto, este trabalho apresenta um motor linear do tipo fluxo longitudinal de 4 fases, destinado a mover um sistema de translação deslizante de abertura e fechamento. A robustez, a simplicidade de construção e a potência reduzida foram decisivos na escolha do tipo de máquina. A análise via elementos finitos (AEF) é aplicada a fim de determinar o desempenho, qualificado pela auto-indutância das bobinas de fase e pela capacidade de produção da força de propulsão. A AEF também é utilizada na avaliação do fator de ondulação da força (force ripple), altamente presente neste tipo de motor, além da produção de vibração e ruído acústico, decorrentes do mesmo. The linear variable reluctance motor (LVRM) is an electric machine fed by direct current with excited phases in a given sequence. Characterized by operating in a wide range of speed variation, it is used in linear applications that converts electric energy into force and translation movement. The need for current switching devices and a control system requires a good estimate of the motor’s inductance profile. However, since the larger air gap makes analytical calculation difficult, this profile must be obtained by numerical methods. In this context, this work presents a linear motor of the 4 phase transverse flow type designed to move a sliding translation system of opening and closing. Robustness, simplicity of construction and reduced power are decisive in the choice of machine type. The finite element analysis (FEA) is applied in order to determine the performance, qualified by the self-inductance of phase coils and the propulsion force production capacity. The FEA is also used in the evaluation of the force ripple factor, highly present in this type of motor, besides the production of vibration and acoustic noise arising from ripple factor. Dissertação (Mestrado)

This document reviews the current state of the art in the linear machine technology. First,the recent advancements in linear induction, switched reluctance and permanent magnet machines arepresented. The ladder slit secondary configuration is identified as an interesting configuration for linearinduction machines. In the case of switched reluctance machines, the mutually-coupled configuration hasbeen found to equate the thrust capability of conventional permanent magnet machines. The capabilities ofthe so called linear primary permanent magnet, viz. switched-flux, flux-reversal, doubly-salient and verniermachines are presented afterwards. A guide of different options to enhance several characteristics of linearmachines is also listed. A qualitative comparison of the capabilities of linear primary permanent magnetmachines is given later, where linear vernier and switched-flux machines are identified as the most interestingconfigurations for long stroke applications. In order to demonstrate the validity of the presented comparison,three machines are selected from the literature, and their capabilities are compared under the same conditionsto a conventional linear permanent magnet machine. It is found that the flux-reversal machines suffer froma very poor power factor, whereas the thrust capability of both vernier and switched-flux machines isconfirmed. However, the overload capability of these machines is found to be substantially lower than theone from the conventional machine. Finally, some different research topics are identified and suggested foreach type of machine.

Linear hybrid excited flux switching machines (LHEFSM) combine the features of permanent magnet flux switching machines (PMFSM) and field excited flux switching machines (FEFSM). Because of the widespread usage of rare-earth PM materials, their costs are steadily rising. This study proposes an LHEFSM, a dual stator LHEFSM (DSLHEFSM), and a dual mover LHEFSM (DMLHEFSM) to solve this issue. The employment of ferrite magnets rather than rare-earth PM in these suggested designs is significant. Compared to traditional designs, the proposed designs feature greater thrust force, power density, reduced normal force, and a 25% decrease in PM volume. A yokeless primary structure was used in a DSLHEFSM to minimize the volume of the mover, increasing the thrust force density. In DMLHELFSM, on the other hand, a yokeless secondary structure was used to lower the secondary volume and the machine’s total cost. Single variable optimization was used to optimize all of the proposed designs. By completing a 3D study, the electromagnetic performances acquired from the 2D analysis were confirmed. Compared to conventional designs, the average thrust force in LHEFSM, DSLHEFSM, and DMLHEFSM was enhanced by 15%, 16.8%, and 15.6%, respectively. Overall, the presented machines had a high thrust force density, a high-power density, a high no-load electromotive force, and a low normal force, allowing them to be used in long-stroke applications.

More and more gas reciprocating generator units are integrated into offshore platforms, due to their compact structure and high efficiency. This paper concentrates on the transient stability analysis of one special type of AC microgrids containing a gas reciprocating generator unit. Firstly, the operation principle for the gas reciprocating generator unit is presented, which mainly consists of a reciprocating internal combustion engine and a linear synchronous alternator (LSA). Afterwards, the mathematical model for the core part of the gas reciprocating generator unit LSA is proposed, based on the principle of armature reaction in traditional synchronous and asynchronous machines. Finally, the simplified model of the independent offshore power system with a gas reciprocating generator unit is derived, and numerical simulations on the transient stability of this typical AC microgrid are performed, from which the effectiveness and correctness of the LSA model are validated. The transient stability analysis method of the independent offshore power system and the mathematical model of LSA can provide beneficial guidance for the stable operation of other types of stand-alone AC microgrids.

The thermal design is one of the most important stages in the design process of electrical machines. Thanks to software packages, like Motor-CAD, rotating machine designers can predict the thermal operation of the machines with high precision. However, a Motor-CAD equivalent for linear machines does not exist. Thus, linear machine designers must develop specific thermal analysis tools when designing the machines. In this article, a generic thermal analysis tool for different kinds of linear machines is presented. The model has been designed in MATLAB Simulink. Hence, it should be easy to implement for most engineers. The article describes the configuration of the different elements of the tool. The calibration parameters and procedure, and typical values of the calibration variables, are also given in the document. Finally, in order to demonstrate the generic nature of the tool, the model is experimentally validated via DC thermal tests to a linear induction machine and a linear switched-flux permanent magnet machine. The results show that, despite being simple and easy to implement, the model can predict the thermal operation of different machines with high precision.

In this study, analysis of core-loss occurring in the magnetic flux modulation core of a linear magnetic gear and the core of each mover is presented, using an analytical method. Losses in electric machines were generally calculated and analyzed using the finite element method (FEM). However, in the case of core-loss, the exact loss value could not be calculated using FEM data. Therefore, we considered the harmonic component of the air-gap magnetic flux density waveform with the modified Steinmetz equation, and performed a more accurate core-loss analysis with magnetic behavior analysis. Thus, we performed a calculated core-loss characteristic comparison with the FEM and the modified Steinmetz equation.

The paper presents an automatic parameter identification procedure for linear permanent magnet synchronous motors. The electrical parameters of a test machine are estimated by identification tests performed through the inverter. The method employs the available feedback signals that are needed by the control. The stator resistance and machine inductances are estimated through signal injection at standstill. The permanent magnets' flux-linkage identification instead requires carriage movement. Subsequently, the inverter nonlinearity characteristics are identified, again at standstill, through a flux-observer. The proposed self-commissioning process requires only the nameplate data of the machine and no datasheet information of the power electronic devices is needed. The developed techniques can be used both with and without a position sensor. The complete process is automatic and safe to run on its own and requires least intervention from the operator.

The finite reluctance approach is very well suited for fast modeling and dynamic simulation of permanent magnet synchronous machines with inverter feeding. This paper shows validating simulations, in both steady-state and transient conditions, carried out for a permanent magnet linear motor designed for on board ship load actuation. The basics of the method are resumed. The simulations obtained by using the finite reluctance approach are compared with FEM simulations, showing good agreement. Keywords—Dynamic model, dynamic simulation, linear machine, magnetic network, reluctance.

Marine energy represents a very promising source of energy available worldwide. Although this energy is available in several forms, wave energy is the more widespread source characterized by high power density. In order to exploit energy from waves, numerous systems have been designed and commercialized. The Inertial Sea Wave Energy Converter is a device based on a floating body slack-moored to the seabed, using a gyroscope as a reference frame to produce electric power. This paper describes the design of the proposed converter equipped with two linear tubular permanent-magnet generators, exploiting the reciprocating motion between the gyroscopic system and the hull to generate power. The design of a two-phase linear tubular generator is analyzed. Experimental tests on a scale prototype have been performed.

This paper presents the design of an arc linear motor for a new type of robot, named Galileo Sphere, based on direct drive technology for pick and place operations. Pick and place robots require high dynamics and position accuracy and repeatability. A classical implementation is based on rotating electric machines with reduction gearboxes and kinematic mechanisms that convert the rotating motion to linear where necessary. The direct drive technology reduce mechanical losses, backlash, MTBF and a number of components. This technology also achieves higher dynamic and accuracy. The robot has a polar-like configuration with 5 degree of freedom. A dynamical simulator was used to assess motors, that satisfies a typical pick and place trajectory with the different payload. The proposed solution resulted feasible, even at high working frequencies and with payloads up to 4 kg. The precision and repeatability remained high, within 100 mum. The working is a spherical sector with 1870 mm maximum diameter, and 450 mm vertical reach.

On établit analytiquement la distribution des courants induits au sein d'une bande conductrice mince, en mouvement de translation uniforme dans un champ magnétique extérieur d'extension finie purement glissant. On montre que les grandeurs électromagnétiques ne s'expriment pas par des séries, mais par des combinaisons polynomiales exponentielles, à cause des dimensions finies du système. On indique la forme du champ magnétique extérieur permettant d'obtenir un champ d'induction résultant purement glissant à l'intérieur de la bande. Bien qu'à l'origine de la recherche se trouve l'étude des machines linéaires, le problème est traité d'une façon générale et les résultats obtenus peuvent s'appliquer au calcul de divers dispositifs, comme machines en arc, écrans magnétiques, relais de translation, etc...

A theory is developed following work by Williams (1952) and Kiefer (1960) for exact treatment designs in one dimension in which the errors are a stationary process. It is shown that the designs which achieve the minimax value of any of a wide class of functionals on the information matrix for estimation of treatment differences have a special property. If the process is autoregressive of order $p$ then a random piece of the design of length $p + 1$ exhibits uncorrelated treatment values. Such designs can be formed using full length cyclic error-correcting codes of a suitable order. A new technique is developed for classifying the ergodic combinatorial structure of exact designs of arbitrary or infinite length. It is shown that all designs are, to $p$th order, generated by a finite number of sequences with finite length. The classification is given explicitly up to order 3. The method is used to find asymptotically optimum designs for different processes. It is also shown that the designs can be achieved to within an arbitrarily good approximation as the realization of an ergodic Markov chain of sufficiently high order.

This paper presents a method to detect the position of a linear actuator without any position sensor. The actuator winding has a resonance frequency that is very related to the position of the linear actuator moving part. A sinusoidal scan voltage is superposed to the main voltage. Its frequency is close to the resonance frequency and therefore it is possible to measure the resulting scan current amplitude that allows position detection.

In this paper a mathematical model of tubular linear induction machines (TLIM) with hollowed induced part is recalled. Moreover the design criteria of a TLIM with hollowed iron induced part are presented as well as the technological processes to be adopted and the choice of materials to construct the various parts. The methodologies for mechanical assembling and electric wiring are considered too. A prototype with bimetallic induced part has been designed and built. Finally some experimental results on electrical and mechanical variables, when the machines are used as motors, are shown.