Wide Speed Range Research Articles

Acoustic Noise Mitigation in High Pole Count Switched Reluctance Machines Utilizing Skewing Method on Stator and Rotor Poles

Multiphysics analysis and experimental validation of acoustic noise reduction in a high pole count, high power, switched reluctance machine (SRM), through skewing are explored in detail in this work. An iterative optimization strategy covering electromagnetic, structural, and thermal domains is proposed to investigate the effect of different skewing methods and angles on a 24-stator slot/16-rotor pole (24/16) SRM rated at 100 kW. The contributions of this work are twofold. First, electromagnetic impact, considering average torque, torque ripple, radial and tangential air gap forces, of symmetric and asymmetric skewing on stator and rotor is studied in this work. Second, the impact of skewing methods on acoustic noise and vibration performance is studied and presented in detail. The study reveals that skewing both the stator and rotor by the same amount has superior electromagnetic performance over other types of skewing. Multiphysics simulations conducted, predict a 10.5 dBA reduction in the acoustic noise, compared to a baseline design with no skew, for an optimized rotor-stator skewing angle of 13.75°. Finally, 100 kW prototypes of the baseline and the optimized skewed SRM were constructed and subjected to wide speed range testing. Simulation and test results closely follow each other and validate the effectiveness of the proposed skew design in mitigating acoustic noise and vibration in high pole count SRMs.

A New Analytical MPPT-Based Induction Motor Drive for Solar PV Water Pumping System With Battery Backup

In this article, an analytical method is presented to achieve maximum power point tracking (MPPT) for a solar photovoltaic (PV) array-based water pumping system comprising of an induction motor drive (IMD). The gating signals are generated using the space vector pulsewidth modulation (SVPWM) method for three-phase inverter. This analytical MPPT control (AMPPTC) scheme exhibits fast dynamic performance and minimum overshoot with the IMD-based water pumping system. Additionally, the AMPPTC scheme provides absolute steady-state robustness under variations in solar irradiance/parameters that improves the stability of the system under a wide speed range of IMD and makes the system insensitive toward parameter variations. The dc-link voltage regulation is assured by three-phase inverter, and MPPT regulation is achieved by the boost converter. This two-stage PV system, with MPPT controlled boost converter and SVPWM-based three-phase inverter operating the pump, is modeled and simulated in Simulink environment of MATLAB. The performance and robustness of the AMPPTC-based PV water pumping system are corroborated through the laboratory experimentation.

Stability Analysis and Trajectory Design of a Nonlinear Switching System for Speed Sensorless Induction Motor Drive

For wide-speed range operation of speed sensorless induction motor drives (SSIMD), the stable operation at low synchronous speed range (including zero synchronous speed) is a great challenge. Virtual voltage injection method is found efficient to overcome this challenge. However, the injected virtual voltage into observer results in the estimated speed error, it is reasonable to rely upon this method only when the performance of traditional SSIMD is poor, i.e., at low speed range. At middle and high speed ranges, virtual voltage injection method cannot meet the high-accuracy requirement of speed estimation in industrial application. For wide-speed range operation of SSIMD, a necessary switching system is proposed in this article to meet the stability requirement and accuracy requirement at the same time. The input-state stability theory is adopted to verify the stability of switching method, because the switching system is a nonlinear and strong coupling system. Then the switching trajectory is optimized for smooth and fast switching transition. Finally, the effectiveness and feasibility of the proposed method are verified by experimental results.

The effect of machined valve springs application on dynamic properties of electro-hydraulically driven valve train

Nowadays, the constant striving to reduce the emission and increase the overall efficiency over a wide range of speeds and loads of the internal combustion engine (CE) is observed. The different methods for improving the charge exchange in the engine, particularly ones based on the variable valve timing are sought. This variability can be achieved, among others by using the electrohydraulic valve drive. The goal of the present study is to compare the dynamic parameters of the engine valvetrain utilizing the unilateral electrohydraulic valve drive and various types of valve springs. The model of such a drive being developed by authors and experimentally verified was used for the analysis. Using the Finite Element Method, the models of springs made through the machining from single sleeves were developed. The effect of various geometrical parameters of the modernized springs on their stiffness and on the resulted valvetrain dynamics was examined.

Optoelectronic system for controlling an alternating current motor. Electrical and electronic design

A control system for a three-phase induction motor was designed with the use of optoelectronic components and methods. Motor speed was controlled by changing supply voltage frequency. This solution ensures a wide range of rotational speeds, constant torque and effective start-up of an induction motor. The designed motor is supplied with direct current converted to three-phase alternating current. The adopted solution relies on renewable sources of energy to produce DC power. The designed electric motor is controlled by changing supply voltage frequency. Input voltage with the desired waveform is generated by the motor’s electronic system that relies on two microcontrollers. The presented solution features a user interface.

Swiveling Magnetization for Anisotropic Magnets for Variable Flux Spoke-Type Permanent Magnet Motor Applied to Electric Vehicles

This paper investigates the application of anisotropic low-coercive force (LCF) magnets to a novel variable-flux spoke-type permanent magnet synchronous motor (VFS-PMSM) for electrical vehicles with a wide speed range. In the VFS-PMSM, flux is regulated by swiveling the magnetization of the anisotropic LCF magnets instead of directly magnetizing or demagnetizing them. The previously proposed VFS-PMSM uses only isotropic LCF magnets for easily swiveling the magnetic pole direction, resulting in lower torque density. The challenge thus lies in the feasibility to swivel the magnetic pole direction of the anisotropic LCF magnet, and the impact of the different magnetization strengths of the anisotropic magnets on the motor performance. This paper first studies the feasibility to swivel the magnetization direction of anisotropic LCF magnets through experiments. It is confirmed that the magnetization direction can be successfully swiveled by 90 degrees with a reduced external magnetizing field. Then, two VFS-PMSM topologies and various rotor configurations are compared in terms of key performance indices to determine critical sizing factors for performance enhancement. Finite element analysis is used for simulations. In comparison with the VFS-PMSM equipped with isotropic LCF magnets, the maximum torque of the proposed topology can be improved for the same flux adjustment ability. Alternatively, the flux adjustment ability can also be enhanced by 37.43% for the same maximum torque.

Automatic Shift Control of an Electric Motor Direct Drive for an Electric Loader

Traditional loaders with engines present the drawbacks of high energy consumption and poor emissions performance. The usage of an electric motor instead of an engine in an electric loader can effectively improve energy efficiency and emissions. The loader is mainly used in the earthwork construction of unstructured roads. Compared to the automobile, during the working process of the loader, the load fluctuates violently, and the vibration is serious. A large torque range during operation, a wide speed range during transfer, and frequently switching gears to ensure power are required by the loader. Therefore, the automatic shift control strategy for an automobile cannot be well applied to the loader directly. In this paper, a novel distributed electric motor-driven loader in which the walking drive system and the hydraulic system is decoupled is studied. The shift rule of the electric loader is also studied. A comprehensive automatic shift control strategy considering power and economy is proposed. Simulations are carried out to verify the feasibility of the proposed control strategy. The results show that under the “V” cycle operation condition of the loader, the shift rule meets the control requirements and the shift effect is obvious and reasonable. In terms of transfer conditions, the proposed control strategy yields ideal power performance and energy savings.

Optimum Selection of Coated Piston Rings and Thrust Bearings in Mixed Lubrication for Different Lubricants Using Machine Learning

The purpose of this study is to build a parametric algorithm combining analytical results and Machine Learning in order to improve the tribological performance of coated piston rings and thrust bearings in mixed lubrication using different synthetic lubricants. The friction models for piston ring conjunction and pivoted pad thrust bearing consider the basic lubrication theory, the detailed contact geometry and the complete lubricant action for a wide range of speeds. The data produced from the analytical solutions are used as input for the training of regression models. The effect of TiN, TiAlN, CrN and DLC coatings on friction coefficient are investigated through multi-variable quadratic regression and support vector machine models. The optimum selection is considered when the minimum friction coefficient is predicted. Smooth TiN2 and TiAlN coatings seem to affect better the ring friction coefficient than rougher steel, TiN1 and CrN coatings using an uncoated or coated Nickel Nanocomposite (NNC) cylinder. Using an NNC cylinder for better durability, the friction coefficients were found to be higher by 31.3−58.8% for all the studied rings due to the rougher surface morphology. On the other hand, the results indicate that pads coated with DLC show lower friction coefficients compared to the common steel and TiAlN, CrN, and TiN applications. The multi-variable second-order polynomial regression models were demonstrated to be 1−6% more accurate than the quadratic support vector machine models in both tribological contacts.

Respective effect of waterjet suction and jet action on hull resistance

Waterjet suction and jet action have their own effect on hull resistance. It is generally hard to quantify their respective roles on changing hull resistance through the model tests and conventional numerical simulations. Apart from the bare hull and self-propelled hull, this paper introduces another three intermediate self-propelled hulls with overall waterjet action, single suction and single jet action respectively through numerical simulations. Combined with model test, this paper conducts numerical investigations on the respective effect of waterjet suction and jet action on resistance in a wide speed range of 0.68 <Fr▽ < 6.16. At low speed, it is the jet action of waterjet that plays the dominant role on influencing the earlier critical Froude number of transom clearance of self-propelled hull, while the waterjet suction has little effect on it. At semi-planing and planing states, the variation of pressure and shear stress acted on aft-hull is majorly influenced by waterjet suction, which dominants the local effect (flow field change) and global effect (hull attitude variation) on resistance at the same time. This work is helpful to explore further understand on hull-waterjet interaction and provide more detailed instruction on design of waterjet-propelled planing crafts.

Multi-Objective Optimization Design and Analysis of V-Shape Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors (PMSMs) are the main source of power in modern machine tools and are required to generate a high torque over a wide speed range in order to improve manufacturing efficiency. This study sets out to optimize the rotor design of a PMSM with a rated power, rated speed, rated torque and maximum speed of 34 kW, 2250 rpm, 144.3 N·m and 11,250 rpm, respectively. A multi-objective optimization algorithm is employed to determine the rotor design parameters which maximize the output torque of the PMSM over three different load conditions (no load, rated load and maximum speed load). ANSYS multi-physics simulations are conducted to examine the electromagnetic, the structural field, temperature/flow field, demagnetization parament analysis and map analysis of global characteristics of the optimized PMSM. In general, the results show that the optimized PMSM provides a high torque and high-speed expansion performance, and thus facilitates a wide range of applications from low-speed heavy cutting to high-speed cutting without the need to replace the motor or machine tool.

Comparison of Interior Permanent Magnet and Synchronous Homopolar Motors for a Mining Dump Truck Traction Drive Operated in Wide Constant Power Speed Range

Synchronous homopolar motors (SHMs) with an excitation winding located at the stator and a toothed salient pole rotor are a good alternative to motors traditionally used in traction applications such as induction motors or interior permanent magnet synchronous motors (IPMSM). This study presents the results of a theoretical comparison between an IPMSM and an SHM in a traction application with a constant power speed range of 1:10, which is specific to the mining truck drives, and with a rated power of 370 kW. The considered IPMSM and SHM have the same number of phases, poles and stator slots, and the same outer diameter of the stator lamination. The IPMSM design is optimized using the Nelder–Mead method. The main objectives of optimization are to minimize the average losses in the operating cycle and to limit the required power of the semiconductor inverter. The performance of the optimized IPMSM is compared with the previously obtained performance of the SHM optimized by the same method. Although the average losses in the operating cycle in the compared motors are approximately equal, the losses at high speed for the IPMSM are about two times greater than at low speed with maximum torque, which means that there is a need to intensify the IPMSM cooling system and there is deterioration of reliability. The advantage of the IPMSM is the reduction in the length of the active part by 30%. The advantage of the SHM is that there is 4.6 times lower cost of active materials. In addition, the SHM is more reliable than the IPMSM, as there is no risk of overheating, demagnetization or degradation of permanent magnets over time.

Steady State Modeling and Performance Analysis of a Wind Turbine-Based Doubly Fed Induction Generator System with Rotor Control

The utilization of renewable energy sources aids in the economic development of a country. Among the various renewable energy sources, wind energy is more effective for electricity production. The doubly fed induction generator is an extensively known wind turbine generator for its partially rated power converters and dynamic performance. The doubly fed induction generator assists the wind turbine to function with a wide speed range. Hence, the steady-state performance analysis of a doubly fed induction generator helps enable it to operate efficiently at a specific wind turbine speed. In this paper, a 2 MW variable speed pitch regulated doubly fed induction generator with a speed range of 900—2000 rpm was opted for steady-state analysis. This was followed by the design and modelling of a doubly fed induction generator in Matlab/Simulink environment, and the analyses were performed using mathematical equations computed via Matlab coding. The steady-state magnitudes were calculated with rotor magnetization idr = 0. The closed-loop stator flux-oriented vector control is applied to the rotor side converter for controlling the designed doubly fed induction generator model. The simulation results were compared with computational values to establish a workable model with less than 10% error. The simulation model can be used for predicting the performance of the machine, fault analysis, and validation of existing DFIG at a steady state.

Intelligent ship anti-rolling control system based on a deep deterministic policy gradient algorithm and the Magnus effect

Anti-rolling devices are widely used in modern shipboard components. In particular, ship anti-rolling control systems are developed to achieve a wide range of ship speeds and efficient anti-rolling capabilities. However, factors that are challenging to solve accurately, such as strong nonlinearities, a complex working environment, and hydrodynamic system parameters, limit the investigation of the rolling motion of ships at sea. Moreover, current anti-rolling control systems still face several challenges, such as poor nonlinear adaptability and manual parameter adjustment. In this regard, this study developed a dynamic model for a ship anti-rolling system. In addition, based on deep reinforcement learning (DRL), an efficient anti-rolling controller was developed using a deep deterministic policy gradient (DDPG) algorithm. Finally, the developed system was applied to a ship anti-rolling device based on the Magnus effect. The advantages of reinforcement learning adaptive control enable controlling an anti-rolling system under various wave angles, ship speeds, and wavelengths. The results revealed that the anti-rolling efficiency of the intelligent ship anti-rolling control method using the DDPG algorithm surpassed 95% and had fast convergence. This study lays the foundation for developing a DRL anti-rolling controller for full-scale ships.

Sensorless vector control scheme for an induction motor fed by MMC

ABSTRACT Due to its notable advantages, Modular Multilevel Converter (MMC) is considered to be employed for medium-voltage motor drives. In this paper, a high-performance sensorless vector control scheme inspired from the Model Reference Adaptive System (MRAS) approach is developed for an MMC-fed induction motor. Besides the well-known vector control scheme advantage, i.e. independent control of motor flux and torque, eliminating the speed sensor will notably improve the reliability of the proposed method. The motor flux components in the αβ frame are determined and used for estimating the speed value. As the errors of flux components calculated by the motor voltage and current models are continuously compensated by a MRAS-based loop, the estimation would be accurate for a wide range of speeds. Moreover, several modifications are considered to add the capability of voltage balancing for submodule capacitors, and also circulating current control to the proposed scheme. The two aforementioned features are necessary for efficient operation of MMC. Moreover, the circulating current control capability is mandatory for injection of different circulating current profiles, which is required for reducing the flying capacitors’ voltage ripples at low speeds. Finally, different performance aspects of the proposed method are experimentally assessed and validated.

Friction Stir Spot Welding of Different Thickness Sheets of Aluminum Alloy AA6082-T6.

Friction stir spot welding (FSSW) is one of the important variants of the friction stir welding (FSW) process. FSSW has been developed mainly for automotive applications where the different thickness sheets spot welding is essential. In the present work, different thin thickness sheets (1 mm and 2 mm) of AA6082-T6 were welded using FSSW at a constant dwell time of 3 s and different rotation speeds of 400, 600, 800, and 1000 rpm. The FSSW heat input was calculated, and the temperature cycle experience during the FSSW process was recorded. Both starting materials and produced FSSW joints were investigated by macro- and microstructural investigation, a hardness test, and a tensile shear test, and the fractured surfaces were examined using a scanning electron microscope (SEM). The macro examination showed that defect-free spot joints were produced at a wide range of rotation speeds (400–1000 rpm). The microstructural results in terms of grain refining of the stir zone (SZ) of the joints show good support for the mechanical properties of FSSW joints. It was found that the best welding condition was 600 rpm for achieving different thin sheet thicknesses spot joints with the SZ hardness of 95 ± 2 HV0.5 and a tensile shear load of 4300 ± 30 N.

Numerical simulation and prototype experiment of integrated electrohydraulic pump

Integrated electrohydraulic pump (IEHP) is conceived as an innovative design concept to achieve the higher power density, lower noise level, and leakage-free with respect to the traditional hydraulic power units. Nevertheless, the complex cooling circuit may increase the flow resistance, reducing the effective delivery flow rate of IEHP, which will be more serious at high rotational speed. In this context, a novel centrifugal charging pump (CCP) integrated on the hollow drive shaft is arranged on the suction path of positive-displacement vane pump (main pump) to boost its inlet pressure, thus efficiently improving the suction capability of IEHP. The contribution of this study is to develop a full flow field CFD model of IEHP, in which the fluid domain of main pump and CCP are connected in series. Based on the CFD model validated subsequently by prototype experiment in terms of volumetric efficiency, the charging effect of CCP modeled with different geometric parameters, at 1,500 r/min, has been investigated. Finally, combined with experiment and simulation, the delivery flow rate of IEHP, in the speed range 600–6,000 r/min, are also analyzed by means of comparing with a standard vane pump. The results show that the CCP makes an outstanding contribution to the filling of main pump, especially when the rotational speed exceeds 3,000 r/min; Since then, the flow rate saturation of standard vane pump tends to occur due to serious incomplete filling, while the IEHP still maintains valid output. It can be concluded that, with the help of charging effect of CCP, the IEHP can keep the same volume efficiency as the vane pump under rated speed, and there is a certain potential for the application of IEHP in a wide speed range.

Insight into macroscale superlubricity of polyol aqueous solution induced by protic ionic liquid

Currently, macroscale liquid superlubricity remains limited to low applied loads and typical ceramic friction pairs. In this study, a robust macroscale superlubricity with a coefficient of friction (COF) of approximately 0.006 is realized at the bearing steel interface induced by protic ionic liquids (ILs) in propylene glycol aqueous solution, and the lubrication system exhibits excellent anti-corrosion properties. Results show that superlubricity can be achieved by employing ILs with longer alkyl chains over a wide load (< 350 N) and speed (> 700 r/min) range. By systematically investigating factors affecting superlubricity, including the IL structure, ionization degree, test conditions, polyol, water-to-alcohol ratio, and lubrication state, the superlubricity mechanism is discussed. Notably, a thicker and denser stern layer can be formed using ILs with longer alkyl chains, which participates in the tribochemical reaction with the metal substrate to form a tribofilm during rubbing. The hydrogen bond network layer formed by the hydrogen ion and polycol aqueous solution can withstand high applied loads. Water can be used to reduce the shear stress of polyols, and enable superlubricity to be achieved under high-speed rotations. Moreover, an inevitable running-in period serves as a dispersing contact stress and dynamically forms a lubricating film, where the lubrication state locates mixed lubrication and then transforms into boundary lubrication as the roughness of the contact surface increases. This study is expected to significantly promote the development and application of superlubricity in the engineering field.

Investigation of the influence of hydraulic oil temperature on the variable-speed pump performance

This paper describes investigation on the influence of hydraulic oil temperature on the performance of a hydraulic pump. The aim of the research is to determine changes in volumetric efficiency of the pump in the form of maps of operation at different temperatures of the hydraulic oil, in conditions of variable speed and pressure. The described tests were carried out on an experimental stand with a hydraulic fixed-displacement gear pump controlled by a servo motor. Based on the signals from the sensors processed with the LabVIEW program, maps of the hydraulic pump operation were drown in a wide range of speeds and temperatures. The paper presents the results of the research and based on this the conclusions regarding the main aim of the research and others that were observed during the measurements were presented. The most important conclusion from the study shows that the temperature-dependent characteristics provide users with a significant amount of information such as operating conditions that will ensure a high level of efficiency.

A self-powered absolute shaft encoder based on triboelectric nanogenerator

A rotary encoder is an important element for measuring the rotational motion in various mechanical systems. This paper proposes a self-powered absolute shaft encoder (SPASE) based on a triboelectric nanogenerator that enables absolute angle measurement and stable signal detection without additional circuits for signal processing by utilizing a voltage pumping method. SPASE was designed by separating the measurement function and the triboelectric power generation function and modularizing the parts that perform each function. A SPASE prototype with a size of ϕ42 mm × 50 mm was manufactured. It was experimentally confirmed that, in this prototype, a voltage of 182.7 V can be generated in the pumping module and that stable angle measurement with a resolution of 12° can be successfully conducted over a wide speed range from 40 to 2000 rpm in the sensing module. Furthermore, SPASE exhibits great applicability and flexibility as a self-powered absolute angle sensor because the pumping and sensing modules are separated and each module can be independently operated as needed. SPASE is expected to be used in various fields that require rotation monitoring without any external power sources.

Rotor Flux Estimator Design With Offset Extractor for Sensorless-Driven Induction Motors

In sensorless drive of induction motors (IMs), the design of a voltage model (VM) for flux estimation is challenging because of its inherent problems with dc saturation and drift. In the implementation of VM, various strategies have been studied in the flux estimator design. The closed-loop (CL) style flux estimator is a popular scheme owing to its good performance in a wide speed range. However, the CL style suffers from dc drift problems because of an offset at the back electromotive force. Based on the fact that dc drift always persists in the CL style flux estimator, this article proposes an offset extractor (OE) using a parallel structure of two CL style flux estimators. Moreover, a crossover strategy is applied to the comparative flux used in the CL scheme. This strategy guarantees low-speed operation including zero speed. When offset compensation using the proposed OE is applied to the flux estimator in a feedforward manner, the proposed flux estimator exhibits good performance in a wide speed range with robustness to the offset. Compared with the conventional methods, the proposed OE and flux estimator are verified in various situations by simulation and experiment in a sensorless-driven IM.