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

High Speed flywheel and test rig design for rural energy storage

There is considerable growth in the renewable energy sector to contribute to sustainable development, environmental conservation and most importantly to provide affordable energy to isolated rural communities of sub-Saharan Africa. Renewable energy sources such as solar and wind require energy storage since the source of energy is intermittent. Electrochemical batteries especially from lead acid are commonly used to store energy in Solar Home Systems (SHS) for rural electrification in sub-Saharan Africa. Disadvantages such as low efficiencies, low life cycle costs, high maintenance, comparatively short life and serious environmental and human toxicity effects exist. Since recycling is not widespread, replacement costs are high, as are the resultant environmental damage and health hazards from lead and sulphuric acid. In this thesis, an electromechanical flywheel energy storage device is proposed as an alternative to a lead acid battery in order to increase efficiency, life expectancy, increased high depth of discharge, low life cycle cost and elimination of adverse environmental effects. Due to income and service skill constraints in rural areas, the proposed, high speed flywheel systems (for long time energy storage) will require the use of low cost configurations and topologies, special considerations on the flywheel rotor profile design, robust electrical machines, simple power electronics and a low cost bearing set. Low loss magnetic bearings are also possible but were limited by time while also making their maintenance complex especially in rural areas. Conventional high strength composite materials used in flywheel rotor manufacture for high speed operation are expensive. Therefore there is a need to develop techniques to profile the rotor shape so as to improve on material usage and exhibit lower mechanical stresses. A robust electrical machine topology for high speed operation and a simple drive system are investigated to ensure simple assembly, low cost and low maintenance. vii The various flywheel components were designed using analytical and numerical methods. Two techniques were used to develop two optimal profiles for the flywheel rotor structure. Partial differential equations and analytical solutions were employed to develop the profiles. Analytical equations were used to design the electrical machine, drive, bearing system and other accessories. The final electromechanical battery prototype consisted of a composite flywheel rotor made from E-glass fibre materials, double rotor Axial Flux Permanent Magnet (AFPM) machine and a drive system using Brushless DC (BLDC) mode of operation. The system was designed for 300Wh of energy storage for the delivery of 100W and 500W of power and an operating speed range of 8,000 rpm-25,000 rpm. The design and development of the flywheel energy storage system and test rig using locally available materials was investigated. Experiments were conducted for speeds up to 6,000 rpm. The electromechanical battery was able to store a maximum of 77Wh of energy. The shortfall of the system to meet its design specifications was investigated and found to have been caused by vibrations resulting from prototyping issues. A thermal model was developed to predict the temperature rise in the system which showed a good correlation with the experimental results

ANALYZING THE POTENTIAL TO COMBINE ENERGY GENERATING TECHNOLOGIES WITH STRENGTH TRAINING EXERCISE MACHINES

Our energy intensive lifestyle is damaging to ourselves and the environment. The developed world has established an intricate energy sector that is dependent on fossil fuels which relentlessly releases greenhouse gases into the atmosphere leading to climate altering impacts and environmental degradation. Americans, in particular, have used this development to become more sedentary and ultimately unhealthier. This research project is aimed at realizing the potential to electrify the fitness industry by examining the potential to make strength training exercise machines a distributed energy source. In this project, three designs were analyzed to understand their unique drivetrain components and how they operate. These designs include the SportsArt ECO-POWR G575R Recumbent Cycle, the NordicTrack Fusion CST, and Tonal. The research uncovered that there is a shift away from traditional, real weights to the use of magnetic resistance to provide the resistive force for cardio and strength training exercise machines. Interestingly, the magnetic resistance component allows for the designs to harness some of the mechanical energy from the user’s workout and convert it to usable electricity; however, the electricity produced from this process was usually wasted as heat which raises the prospect of improving the design to capture that electricity. This research project found there was an adequate amount of potential to alter the designs of strength training machines to be net suppliers of electricity which could result in not only contributing to a healthier population, but this could also promote a more sustainable lifestyle

Magnetically levitated hysteresis motor driven linear stage for in-vacuum transportation tasks

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 241-246).This thesis presents a new in-vacuum reticle transportation mechanism for extreme ultraviolet (EUV) photolithography machines. In the photolithography process, the reticle is a quartz plate that contains a pattern of the integrated circuit, which needs to be transported between a storage position and the exposure stage. In next-generation EUV lithography machines, the reticle handling system must satisfy the following requirements: (1) transport the reticle through a distance of 2 meters, (2) the height of the mechanism needs to be within 100 mm, (3) operate in vacuum, and (4) satisfy ultra-tight contamination requirements. To fulfill these requirements, a conventional robotic reticle handler is inadequate. In this work, we designed, built, and tested a magnetically-levitated linear stage prototype, targeting at the reticle transportation application. Compared with robot manipulators, linear stages typically require less volume for long-distance transportation tasks.Magnetic suspension is used to eliminate mechanical contact and thereby avoid particle generation that can contaminate the reticle. The stage's linear motion is driven by linear hysteresis motors, which allows using solid-steel motor secondaries on the moving stage. This is desirable for in-vacuum operation, since permanent magnets can out-gas in high vacuum when not encapsulated. The magnetic suspension of the stage is achieved using a novel linear bearingless slice motor design, where the stage's magnetic suspension in three degrees of freedom, including vertical, pitch, and roll, are achieved passively. This compact design effectively reduces the number of sensors and actuators being used. The prototype system has successfully levitated the moving stage. The resonance frequency of the passively levitated degrees of freedom is approximately 10 Hz, and the suspension bandwidth of the actively-controlled degrees of freedom is about 60 Hz.The stage's maximum thrust force is 5.8 N under a 2.5 A current amplitude, which corresponds to a stage acceleration of 1200 M/s². This is able to satisfy the acceleration requirement for reticle transportation task. The stage was tested to track a reticle handling reference trajectory, where the maximum position tracking error of our linear stage is 50 [mu]m. The stage's lateral displacements during motion is below 50 [mu]m, which is well below making mechanical contact to the side walls. To our knowledge, this work represents the first study of linear hysteresis motors, and the first linear bearingless slice motor design. Hysteresis motors are a type of electric machine that operates using the magnetic hysteresis effect of the secondary material. Since the magnetization in the rotor lags behind the external field, a thrust force/torque can be generated.In prior usage, hysteresis motors have been operated in open-loop, which makes them unsuitable for applications where dynamic performance is critical. As a part of this thesis work, we also studied the modeling and closed-loop torque and position control for hysteresis motors. The proposed control method was tested with three rotary hysteresis motors, including two custom-made motors of different rotor materials and one off-the-shelf hysteresis motor. Experimental results show that position control for all three motors can reach a bandwidth of 130 Hz. To our best knowledge, this is the first work that enabled high-bandwidth torque and position control for hysteresis motors, which allows this motor to be used for servo applications.Sponsored by ASMLby Lei Zhou.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineerin

Control of a brushless permanent magnet machine using an integrated torque sensor in place of a rotor position sensor

The work presented in this thesis proposes the use of measured torque feedback from an integrated, low cost surface acoustic wave (SAW) torque transducer in place of a position sensor to control brushless permanent magnet (BLPM) machines. The BLPM machine closed loop control requires knowledge of the rotor position to control stator current and maximum torque per ampere. The electrical position feedback to control the phase current requires a position sensor or position sensorless technique. Position sensors such as absolute encoder or resolver are needed for position information, in the absolute encoder, an accurately patterned disk rotates between a light source and a detector giving a unique digital output signal for every shaft position. However, each bit in the digital world represents an independent track on the encoder disk, resulting in a complex and costly sensors. Brushless resolvers operation is based on inductive coupling between stator and rotor winding. The resolver with its resolver to digital converter also gives precise absolute position information, but again the cost is often prohibitive. So the disadvantages of the position sensors are the added cost and size to the machine. The position sensorless techniques for the BLPM machine are based on obtaining position from the terminal voltages and currents based on estimating the back electro-magnetic force (EMF), flux-linkage or inductance which from position can be estimated. The disadvantages of the back-EMF and flux-linkage techniques are (1) that they behave poorly at zero and low speed (2) behave poorly for load disturbances since load torque is estimated from machine parameters which can change. The inductance techniques work at zero and low speed, however the disadvantages are (1) in a surface mounted machine there is no saliency so any variation of winding inductances with rotor position arises from magnetic saturation; (2) the back-EMF dominates the rate-of-change in the current; (3) the variation of incremental inductances with rotor position undergoes two cycles per single electrical cycle of the brushless pm machine causing an ambiguity in sensed position; (4) the distortion due to the nonlinearities in the inverter; (5) the load offsets and the noise caused by signal injection. This thesis develops a start-up routine and operation algorithms that enhance the performance of position sensorless control of brushless permanent magnet machines at all speeds, including zero speed, and loads by using a machine integrated, low-cost, SAW torque transducer in place of the rotor position sensor.EThOS - Electronic Theses Online ServicePublic Authority of Applied Education in KuwaitGBUnited Kingdo

Investigation on Multi-Physics Modelling of Fault Tolerant Stator Mounted Permanent Magnet Machines

This thesis investigates the stator mounted permanent magnet machines from the point of view of fault tolerant capability. The topologies studied are switched flux (and its derivatives C-Core, E-Core and modular), doubly salient and flux reversal permanent magnet machines. The study focuses on fault mode operation of these machines looking at severe conditions like short-circuit and irreversible demagnetization. The temperature dependence of the permanent magnet properties is taken into account. A complex multi-physics model is developed in order to assess the thermal state evolution of the switched flux machine during both healthy and faulty operation modes. This model couples the electro-mechanical domain with the thermal one, thus being able to consider a large range of operating conditions. It also solves issues such as large computational time and resources while still maintaining the accuracy. Experimental results are also provided for each chapter. A hierarchy in terms of fault tolerant capability is established. A good compromise can be reached between performance and fault tolerant capability. The mechanism of the magnet irreversible demagnetization process is explained based on magnetic circuit configuration. It is also found that the studied topology are extremely resilient against the demagnetizing influence of the short-circuit current and the magnet demagnetization is almost only affected by temperature

Synchronous reluctance motors with fractional slot-concentrated windings

PhD ThesisToday, high efficiency and high torque density electrical machines are a growing research interest and machines that contain no permanent magnet material are increasingly sought. Despite the lack of interest over the last twenty years, the permanent magnet-free synchronous reluctance machine is undergoing a revival and has become a research focus due to its magnet-free construction, high efficiency and robustness. They are now considered a potential future technology for future industrial variable speed drive applications and even electric vehicles. This thesis presents for the first time a synchronous reluctance motor with fractional slot-concentrated windings, utilizing non-overlapping single tooth wound coils, for high efficiency and high torque density permanent magnet-free electric drives. It presents all stages of the design and validation process from the initial concept stage through the design of such a machine, to the test and validation of a constructed prototype motor. The prototype machine utilizes a segmented stator core back iron arrangement for ease of winding and facilitating high slot fill factors. The conventional synchronous reluctance motor topology utilizes distributed winding systems with a large number of stator slots, presenting some limitations and challenges when considering high efficiency, high torque density electrical machines with low cost. This thesis aims to present an advancement in synchronous reluctance technology by identifying limitations and improving the design of synchronous reluctance motors through development of a novel machine topology. With the presented novel fractional slot concentrated winding machine design, additional challenges such as high torque ripple and low power factor arise, they are explored and analysed - the design modified to minimise any unwanted parasitic effects. The electrical and electromagnetic characteristics of the developed machine are also explored and compared with that of a conventional machine. A novel FEA post-processing technique is developed to analyse individual air-gap field harmonic torque contributions and the machines dq theory also modified in order to account for additional effects. The developed machine is found to be lower cost, lower mass and higher efficiency than an equivalent induction or conventional synchronous reluctance motor, but does suffer higher torque ripples and lower power factor. The prototype is validated using static and dynamic testing with the results showing a good match with finite element predictions. The work contained within this thesis can be considered as a first step to developing commercial technology based on the concept for variable speed drive applications.Financial assistance was provided by was provided by the UK Engineering and Physical Sciences Research Council (EPSRC) in the form of a Doctoral Training Award and additional financial assistance was kindly provided by Cummins Generator Technologies, Stamford, UK, through industrial sponsorship of this wor