Positioning and Smoothing Movement Approaches of a Linear Actuator Dedicated to A Biomedical Application

The movement of linear stepper motors is characterized by a highly oscillatory translation, which is troublesome for the positional accuracy and the speed constant (often required by many industrial applications such as the syringe pump). These oscillations can lead to loss of synchronism and stall risk. Thus, in order to attenuate the amplitudes of these oscillations and to guarantee the positioning of the actuator without errors, solutions exploiting open-loop and closed-loop control techniques are proposed in this paper for the purpose of improve the performance of the actuato

Performance Characteristics of Switched Reluctance Motor Drive

In this report, methods and computational techniques for predicting the static and steady state characteristics of a switched reluctance motor drive are developed and the predicted characteristics are compared with experimental results. Because of high local saturation and narrow airgap in the SR motor, accurate calculation of the static characteristics of the torque, flux linkage, inductances, and speed emf from its FE field solution is not straightforward. For the purpose of this study, a two-dimensional finite element model is developed to handle the nonlinear magnetic field inside the machine. Based on a thorough study of the potential sources of errors in the field solution and in the computational methods used in postprocessing, new guidelines are developed regarding the shape and uniformity of the mesh in the airgap and the preservation of these qualities of the mesh as the rotor is rotated. When the proposed guidelines on the mesh configuration and its rotation were used, significant improvement in the accuracy of the field distribution and in the accuracy of the predicted torque/angle characteristics as compared to the experimentally measured torque was observed. Furthermore, all three methods of torque calculation, namely global virtual work, local virtual work, and Maxwell-stress tensor methods are converging to the same results and the torque/angle characteristics are smooth. Improvement in the prediction of such static characteristics is also essential to a realistic prediction of the steady state behavior. In the study of steady state performance of the SRM drive, the converter is approximated by a controlled, square wave pulse generator. In the integration process, the coefficients of the governing differential equation, being dependent on the phase current and rotor angle, are updated using surface interpolation method on the static characteristics. The predicted steady state characteristics compare favorably with the experimental results over a wide range of torque/speed variation

In-wheel motor vibration control for distributed-driven electric vehicles:A review

Efficient, safe, and comfortable electric vehicles (EVs) are essential for the creation of a sustainable transport system. Distributed-driven EVs, which often use in-wheel motors (IWMs), have many benefits with respect to size (compactness), controllability, and efficiency. However, the vibration of IWMs is a particularly important factor for both passengers and drivers, and it is therefore crucial for a successful commercialization of distributed-driven EVs. This paper provides a comprehensive literature review and state-of-the-art vibration-source-analysis and -mitigation methods in IWMs. First, selection criteria are given for IWMs, and a multidimensional comparison for several motor types is provided. The IWM vibration sources are then divided into internally-, and externally-induced vibration sources and discussed in detail. Next, vibration reduction methods, which include motor-structure optimization, motor controller, and additional control-components, are reviewed. Emerging research trends and an outlook for future improvement aims are summarized at the end of the paper. This paper can provide useful information for researchers, who are interested in the application and vibration mitigation of IWMs or similar topics

Aspects of magnetisation and iron loss characteristics in switched-reluctance and permanent-magnet machines

In the first section, the magnetisation characteristics of the switched-reluctance motor are examined. Measurements have been carried out using both static and dynamic test methods. The test data has been compared with simulation results from analytical design programs and finite element models. The effects of mutual coupling on the magnetisation characteristics are investigated through measurement and simulation. Results show that the degree of mutual coupling is strongly dependent on the winding arrangement of the machine. In the next section, the difficulties in measuring the properties of permanent-magnet machines are discussed in detail, and solutions to common problems proposed. The measurement and analysis methods used for the switched-reluctance motor are further developed for analysis of permanent magnet machines. Techniques for determining the variation in synchronous reactances and permanent magnet flux are presented. Finite element simulations are used to show the variation of magnet flux under loading, a condition ignored in classical analysis methods. The final section discusses the analysis of magnetisation characteristics of electrical sheet steels. Comparison is made between measurements carried out on single sheet tester and Epstein square test rigs. The iron losses of a typical non-grain-orientated steel are measured under both sinusoidal and nonsinusoidal flux density conditions. The iron losses are shown to increase significantly when higher harmonic components are introduced to the flux density waveform. The difficulties in modelling the nonlinear iron loss characteristics of electrical steels are considered

The design of hybrid stepping motors aided by three dimensional finite element analysis

Though the hybrid stepping motor has a long and proven history, in terms of toughness, accuracy of position and the ability to operate in open loop, motor performance improvements can still be made in terms of the physical structure of the motor's components. It is impossible to build a complete solution of the hybrid stepping motor using simple analytical functions or equivalent circuit representations. This is due to the difficulties introduced by the motor's highly non-linear three dimensional magnetic structure, of which the doubly salient tooth structure, axial magnet, and back iron all complicate the situation. However, with the recent advances in three dimensional finite element software a comprehensive study of the motor has been achieved in this thesis. This has allowed improvements to simpler two dimensional based mathematical models, which allow faster computation of the motor's electromagnetic performance. To aid modelling, novel equations which accurately model today's high permeability steels have been developed. These are shown to be more accurate than the established Jiles-Atherton method. Inductance calculations of the steel's flux paths have been comprehensively improved by the use of elliptical functions. The thesis concludes with the design of two quite individual new machines. The first dramatically improves a motor's power output, smoothness, noise levels, and resonance by modifying the tooth structure. The second uses soft magnetic composite materials to provide an isotropic path for cross lamination flux which flows in a stator's back iron. Both new designs are shown to offer a significant improvements to the high speed torque capability of the hybrid stepping motor

Modelling and Control of Switched Reluctance Machines

Today, switched reluctance machines (SRMs) play an increasingly important role in various sectors due to advantages such as robustness, simplicity of construction, low cost, insensitivity to high temperatures, and high fault tolerance. They are frequently used in fields such as aeronautics, electric and hybrid vehicles, and wind power generation. This book is a comprehensive resource on the design, modeling, and control of SRMs with methods that demonstrate their good performance as motors and generators