Tubular Permanent Magnet Actuator Research Articles

Investigation of the thermal effect of a tubular permanent magnet actuator with a water cooling channel for active lateral suspension of a high-speed train

Worldwide, high-speed rail is becoming an increasingly popular and efficient means of transport. However, increasing the speed of a train leads to major reductions in stability and ride comfort. Here, we develop a tubular permanent magnet actuator to overcome these problems. To increase actuator thrust, the electromagnetic circuit requires a high current and, thus, becomes hot. We use a water cooling system with 12 straight copper channels to reduce the temperature. We calculate heat transfer coefficients using empirical convection correlations between laminar flow in the channels and experimental results. The predicted, tube surface temperatures correlated well with the experimental data. We evaluated the effects of flow rate and initial water temperature on various design parameters. The cooling system allowed application of a current greater than 100 A, developing a thrust force of over 8000 N. Thus, the system was robust under harsh operating conditions. We measured the thrust and cogging forces and the performance of the water cooling system in terms of the maximum acceptable temperature. The thrust was high and the cogging torque was low, greatly reducing lateral vibration; the temperature remained below the acceptable maximum.

Design of a Tubular Permanent Magnet Actuator for Active Lateral Secondary Suspension of a Railway Vehicle

This paper describes the finite element (FE)-based design of a slotted tubular permanent magnet actuator (TPMA) used in railway vehicle active lateral secondary suspension that improves the actuator’s thrust and lowers its cogging force under thermal and geometric constraints. To consider the electromagnetic and thermal fields and the complex interactions among the design variables, design was carried out in an electromagnet and thermal field environment using accurate and time-effective FE analysis. A six-slot prototype model was fabricated to estimate critical thermal parameters, which are difficult to compute without experiments. Three-dimensional FE analysis using the determined thermal parameters was adopted to calculate the precise thermal distribution of the TPMA and verify the forced air-cooling effect. A prototype TPMA with a quasi-Halbach array of permanent magnets and a moving magnet was manufactured through the FE-based design process; the dynamic, electromagnetic, and thermal characteristics of the prototype TPMA were validated experimentally.

Position Control of a Multi-Motor Drive Based on Series-Connected Five-Phase Tubular PM Actuators

In this paper, an electric drive for positioning systems, consisting of two five-phase tubular permanent-magnet (PM) actuators fed by a single five-phase inverter, is described. The key idea is to combine together the technologies of tubular PM actuators and of multiphase drives. A proximate time-optimal positioning control scheme and a more conventional positioning control scheme based on PI regulators are presented. In both cases, the disturbances introduced by the parasitic coupling between the two actuators due to a realistic non-ideal sinusoidal distribution of the stator windings are considered and compensated. The behavior of the drive is assessed by means of experimental tests.

Efficiency of a Regenerative Direct-Drive Electromagnetic Active Suspension

The efficiency and power consumption of a direct-drive electromagnetic active suspension system for automotive applications are investigated. A McPherson suspension system is considered, where the strut consists of a direct-drive brushless tubular permanent-magnet actuator in parallel with a passive spring and damper. This suspension system can both deliver active forces and regenerate power due to imposed movements. A linear quadratic regulator controller is developed for the improvement of comfort and handling (dynamic tire load). The power consumption is simulated as a function of the passive damping in the active suspension system. Finally, measurements are performed on a quarter-car test setup to validate the analysis and simulations.

Analysis of 3-D Effects in Segmented Cylindrical Quasi-Halbach Magnet Arrays

To improve the performance of permanent magnet (PM) machines, quasi-Halbach PM arrays are used to increase the magnetic loading in these machines. In tubular PM actuators, these arrays are often approximated using segmented magnets resulting in a 3-D magnetic field effect. This paper describes the results of this segmentation obtained from an analytical model. The influence of the number of segments on the magnetic flux density in the air gap is investigated for several actuator dimensions. Furthermore, the effect of this segmentation on the mean value of the radial component of the flux density over the circumference of the cylindrical air gap is analyzed and a 2-D definition of this effect is given. A general rule is presented as a table showing the decrease of the magnetic field as function of the design parameters.

Active Electromagnetic Suspension System for Improved Vehicle Dynamics

This paper offers motivations for an electromagnetic active suspension system that provides both additional stability and maneuverability by performing active roll and pitch control during cornering and braking, as well as eliminating road irregularities, hence increasing both vehicle and passenger safety and drive comfort. Various technologies are compared with the proposed electromagnetic suspension system that uses a tubular permanent-magnet actuator (TPMA) with a passive spring. Based on on-road measurements and results from the literature, several specifications for the design of an electromagnetic suspension system are derived. The measured on-road movement of the passive suspension system is reproduced by electromagnetic actuation on a quarter car setup, proving the dynamic capabilities of an electromagnetic suspension system.

General Formulation of the Electromagnetic Field Distribution in Machines and Devices Using Fourier Analysis

We present a general mesh-free description of the magnetic field distribution in various electromagnetic machines, actuators, and devices. Our method is based on transfer relations and Fourier theory, which gives the magnetic field solution for a wide class of two-dimensional (2-D) boundary value problems. This technique can be applied to rotary, linear, and tubular permanent-magnet actuators, either with a slotless or slotted armature. In addition to permanent-magnet machines, this technique can be applied to any 2-D geometry with the restriction that the geometry should consist of rectangular regions. The method obtains the electromagnetic field distribution by solving the Laplace and Poisson equations for every region, together with a set of boundary conditions. Here, we compare the method with finite-element analyses for various examples and show its applicability to a wide class of geometries.

Analysis and design of a slotless tubular permanent magnet actuator for high acceleration applications

This paper presents the design of a linear actuator for high acceleration applications. In the analysis, a slotless tubular permanent magnet actuator is modeled by means of semianalytical field solutions. Several slotless topologies are modeled and compared to achieve the highest acceleration. A design has been proposed and built, and measurements are conducted to verify the models.

Design Aspects of an Active Electromagnetic Suspension System for Automotive Applications

This paper is concerned with the design aspects of an active electromagnet suspension system for automotive applications which combines a brushless tubular permanent-magnet actuator with a passive spring. This system provides for additional stability and safety by performing active roll and pitch control during cornering and braking. Furthermore, elimination of the road irregularities is possible, hence, passenger drive comfort is increased. Based upon measurements, static and dynamic specifications of the actuator are derived. The electromagnetic suspension is installed on a quarter-car test setup, and the improved performance using roll control is measured and compared with a commercial passive system. An alternative design using a slotless external-magnet tubular actuator is proposed which fulfills the thermal and volume specifications.

Semi-Analytical Calculation of the Armature Reaction in Slotted Tubular Permanent Magnet Actuators

This paper considers the semi-analytical field calculation of the armature reaction in brushless tubular permanent magnet actuators with rectangular slots. The tubular actuator is considered to have an infinite length and Fourier analysis is used to describe the current density distribution. The field solution is obtained by solving the Maxwell equations in the constant boundary value problem consisting of the airgap and the slot. The results are verified with finite element software, and analysis limitations and inaccuracies are addressed.

Analytical and Numerical Techniques for Solving Laplace and Poisson Equations in a Tubular Permanent Magnet Actuator: Part II. Schwarz–Christoffel Mapping

In Part I of the paper, we derive a semianalytical framework for the magnetic field calculation in the air gap of a tubular permanent-magnet (PM) actuator. We also make an extension for skewed topologies. However, the slotting effect and its related cogging force cannot be determined in a straightforward way. Therefore, in Part II, we apply the Schwarz-Christoffel (SC) conformal mapping method to one pole-pair of the tubular PM actuator. This mapping allows for field calculation in a domain where standard field solutions can be used. In this way, slotting effects can be taken into account; however, skewing cannot be implemented directly. The SC-conformal mapping method is valid only for two-dimensional Cartesian domains. We therefore apply a special transformation from the cylindrical to the Cartesian coordinate system to describe the tubular actuator as a linear actuator.

Analytical and Numerical Techniques for Solving Laplace and Poisson Equations in a Tubular Permanent-Magnet Actuator: Part I. Semi-Analytical Framework

We present analytical and numerical methods for determining the magnetic field distribution in a tubular permanent-magnet actuator (TPMA). In Part I, we present the semianalytical method. This method has the advantage of a relatively short computation time and it gives physical insight. We make an extension for skewed topologies, which offer the benefit of reducing the large force ripples of the TPMA. However, a lot of assumptions and simplifications with respect to the slotted structure have to be made in order to come to a relatively simple semianalytical description. To model the slotting effect and the related cogging force, we apply a Schwarz-Christoffel (SC) mapping for magnetic field and force calculations in Part II of the paper. Validation of the models is done with finite-element analysis.

Aggressive Output Space-Mapping Optimization for Electromagnetic Actuators

Automated electromagnetic actuator design can be achieved by means of several approaches. For example, one might consider fast, however, accuracy deficient coarse models or, in contrast, the design could be achieved exclusively by employing accurate, time expensive, fine models. The space-mapping optimization technique, with its input or output mapping based implementations, merges the advantages of the two extremes. A new algorithm variant that presents a simple structure, namely the aggressive output space-mapping, is proposed in this paper. The design problem of a tubular permanent magnet actuator is considered in order to compare the proposed algorithm with two existing techniques.

Electromagnetic and Thermal Design of a Linear Actuator Using Output Polynomial Space Mapping

This paper describes the optimization methodology used in the design of a slotted tubular permanent-magnet actuator for industrial applications. A time-effective optimization procedure is obtained by considering simple analytical design equations in coherence with 2-D finite-element analysis as means to establish the various design variables. The optimization is performed in a multiphysics environment because both electromagnetic and thermal models are created and used in the optimization routine. The original optimization problem is replaced by a surrogate, which is updated or improved iteratively by means of a space-mapping-based technique. Its application for solving coupled magnetic-thermal design problems for electric machines is a rather unexplored topic.