This article reviews permanent magnet electrodynamic suspensions (PM-EDSs) used in ground transportation systems, such as Magnetic Levitation (MAGLEV) trains. The different suspension topologies are first presented, considering separately their two main components, namely the track and the magnetic field source. Beyond that, a phenomenological explanation of the evolution with the speed of the drag and levitation forces is provided, depending on the track topology. The models aimed at predicting the behavior and performance of the suspension are then detailed, classifying them according to whether they are global or local. Finally, the main experimental setups developed to validate PM-EDSs are described.

This paper presents a robot aimed to assist the shoulder movements of stroke patients during their rehabilitation process. This robot has the general form of an exoskeleton, but is characterized by an action principle on the patient no longer requiring a tedious and accurate alignment of the robot and patient's joints. It is constituted of a poly-articulated structure whose actuation is deported and transmission is ensured by Bowden cables. It manages two of the three rotational degrees of freedom (DOFs) of the shoulder. Quite light and compact, its proximal end can be rigidly fixed to the patient's back on a rucksack structure. As for its distal end, it is connected to the arm through passive joints and a splint guaranteeing the robot action principle, i.e. exert a force perpendicular to the patient's arm, whatever its configuration. This paper also presents a first prototype of this robot and some experimental results such as the arm angular excursions reached with the robot in the three joint planes.

Topologies of electrodynamic thrust bearings (EDTB) and axial flux permanent magnet (AFPM) machines exhibit a significant number of similarities. Starting from this observation, the present paper introduces a new self-bearing motor combining, within a single armature winding and through the same permanent magnets, both the passive electrodynamic axial levitation and motor functions. The rotor axial stabilisation being achieved through passively induced currents, no sensor, controller and power electronics related to the bearing function are required. In addition, an electromechanical model describing both the axial and spin dynamics of such a motor is presented. This set of six equations depends on twelve parameters whose determination can be performed through static finite element simulations or quasi-static experimental measurements. The model is linearised allowing us to study the local stability of this passive self-bearing motor around an operation point characterised by the rotor spin speed as well as the external force and torque. The dynamic and quasi-static behaviours as well as the stable spin speed ranges are analysed through a case study. Finally, a first experimental investigation dedicated to the validation of the operation principle as well as the dynamical model is performed.

Applied to the production of windings, the printed circuit board (PCB) technology is promising for developing high performance slotless permanent magnet machines, since it allows for winding shapes and topologies that are difficult to obtain with the classical wire technology. However, compared with wire windings, PCB windings are more prone to eddy current losses because of the high width-to-thickness ratio of the conductor cross-section. To counteract these eddy currents, the conventional solution consists of reducing the width of the conductive tracks constituting the winding in conjunction with an increased number of turns. To keep the supply voltage within limits compatible with the power supply, parallel connections of the tracks at the winding terminals are required. This article tackles the eddy current problem differently by adding some slits distributed along the conductive tracks. This amounts to carry out local parallelizations without impacting the motor supply voltage. By means of parametric analyses carried out on different slit configurations and considering their impact on both the supply and eddy current losses, this study shows that a parallel reconnection of successive tracks two by two gives almost the same results as a classical parallel connection of all the tracks, independently of the winding shape. Furthermore, this article concludes that the optimal number of parallel slits is fixed and valid for a large range of nominal speed-torque ratios. However, it is necessary to increase the width of the slits when this ratio becomes very high and it is technically no longer possible to increase the number of slits.

Passively levitated thrust self-bearing machines with combined armature windings have recently been introduced. These machines reach higher reliability and compactness while being lower cost than their actively suspended counterparts. However, they result in small axial restoring force and stiffness at low speeds since the axial guidance relies on passive phenomena arising from induced currents. The axial destabilizing stiffness produced by the permanent magnet centering bearings as well as the axial load, therefore, prevent the rotor from levitating below a threshold speed. This article introduces and develops a solution to this problem based on a hybrid active–passive actuation approach of these thrust self-bearing machines. The approach consists of regulating the rotor axial position through the direct-axis component of the currents flowing in half of the combined winding until reaching the threshold speed beyond which passive axial suspension can be achieved. Since the active operation solely requires the addition of an axial position sensor, the benefits related to passive levitation are only slightly affected. Extensive experimental investigations corroborate the force and torque model derived for the active operation and highlight that the transitions between suspension modes have a limited impact on the rotor axial position and spin speed, validating the proposed hybrid active–passive actuation approach.

Self-bearing machines offer a highly integrated solution to achieve the rotor drive and magnetic levitation within a single structure. Although the trend is toward a diminution in the number of actively stabilized degrees of freedom to reduce the requirement for sensors, power electronics, and controllers, no self-bearing machine relying solely on passive phenomena has been successfully tested so far due to the restrictions highlighted by Earnshaw's theorem. Recent researches have demonstrated, through electromechanical models and in-depth experimental investigations, that electrodynamic thrust self-bearing machines (EDTSBMs) can gather, within a combined winding, both the rotor axial passive suspension and motor functions. Nonetheless, the test rigs implementing them still comprised external means to ensure the rotor radial and tilt support. In this context, this article takes the study of EDTSBMs to the final step by combining them with two permanent magnet centering bearings, yielding the first fully passively levitated self-bearing machines. A reaction wheel demonstrator based on the latter is designed and sized according to an optimal approach. Thorough experimental analyses dealing with the axial forces that support the rotor and its resulting axial position as well as the drive torque are carried out, notably proving that stable fully passive levitation can be achieved. Finally, the motor and suspension currents as well as the corresponding losses are investigated.