Low Speed Operation Research Articles

Analysis of the Coupling Mechanism of Liquid Cylinder Vibration Based on the Low-Speed Operating Conditions of Neural Network Model

The connection between the friction negative and related damping is on the low-speed hydraulic cylinder, which will generate the vibration and influence of the hydraulic cylinder, which inhibits the accuracy of the hydraulic equipment. In order to effectively solve this problem, this paper creates a neural network model, considering the negative damping and related damping effects under low-speed conditions, and intended the coupling mechanism of negative damping and related damping. Based on the converter of the hydraulic cylinder, the nonlinear stiffness characteristics of the sensor hydraulic cylinder were analyzed, and the requirements of the hydraulic cylinder collection were obtained according to the requirements of the energy star collection of the liquid voltage star, and the equivalent of the sensor liquid pressure cylinder was obtained. At the same time, the sensor system implements feedback control on vibration velocity and displacement based on changes in piston position, in order to analyze the coupling mechanism of hydraulic cylinder vibration under low-speed operating conditions. The results of the study show that the function of the feedback controller is systematic, and the antipity control contains the possibility of minimizing serious damage and can effectively improve the efficiency and stability of the system. In the actual manufacturing process, we studied the vibration coupling effect of the liquid cylinder under low-speed conditions, proved the change characteristics of the vibration amplitude and frequency of the hydraulic cylinder, and revealed the related damping in the vibration.

Optimization of energy acquisition system in smart grid based on artificial intelligence and digital twin technology

In response to the low operating speed and poor stability of energy harvesting systems in smart grids, an energy harvesting optimization method based on improved convolutional neural networks and digital twin technology is proposed in the experiment. Firstly, a smart grid data transmission framework integrating digital twin technology is proposed. A digital twin mapping method based on time, data, and topology structure is used to realize the digital twin mapping at the device level of power grid. Through data synchronization and interaction between the physical power grid and the digital twin model, the operational efficiency and reliability of the power grid are improved. Then, the classical convolutional neural network and attention mechanism are used to comprehensively analyze the physical topology data in the smart grid energy acquisition system. The improved lightweight target detection model is combined to monitor the equipment status of the smart grid and extract key features. Simultaneously utilizing convolutional attention mechanism to dynamically adjust the feature weights of channels or spaces, completing the preprocessing of energy harvesting data. Finally, combined with energy harvesting and power grid switching system, the process of energy harvesting and power grid operation are optimized together. On the training and validation sets, when the channels exceeded 60, the proposed method achieved a system energy efficiency of 55% during operation. The system energy efficiency of the other three comparative algorithms was all less than 40%. In practical applications, as the energy transfer loss increased to 1.0, the system throughput increased to 50 bits. The electricity needs of different users were met, and the difference between power allocation and optimal power allocation was small, which was very reasonable. This proves that the research has effectively optimized the energy harvesting system in the smart grid, improving the efficiency and reliability of the system in practical applications of the smart grid. At the same time, in the increasingly severe energy problem, this system can further provide technical references for the utilization of renewable energy and help achieve the goal of sustainable energy.

Analysis of single vehicle noise emissions in the frequency domain for two different motorizations

Environmental noise, primarily attributed to the road transportation system, poses a significant challenge in Europe, impacting the quality of life for millions. Therefore, a thorough characterization of noise emissions from road transportation sources is needed to stem this problem. This investigation aims to fill a gap in the literature regarding single-vehicle noise emissions in the frequency domain. The emphasis is on motorization (i.e., fuel type), with particular attention to Low-Frequency components, due to their potential impact on human health and ecosystems. Two probe vehicles, a diesel and a Liquefied Petroleum Gas-powered, were employed to collect data for noise emission curves in the frequency domain (from 63 to 8000 Hz) and compare them with those furnished in the CNOSSOS-EU, Harmonoise, and REMEL models. Moreover, data in terms of exhaust noise emissions (at the tailpipe) were also gathered and analyzed in the frequency domain.The analysis highlighted motorization's influence on noise emissions, revealing differences in frequency component contributions to the overall sound power level at different speeds. Low-frequency components were found to be predominant for both vehicles, especially at lower speeds, where the engine noise contribution dominates. This finds its endorsement in the frequency analysis on the noise emission curves provided in the examined models. The evaluation of the exhaust noise emissions revealed resonance phenomena at 63 Hz and showcased the dominance of low-frequency components in the exhaust spectrum (despite the penalization introduced by the A-weighting procedure), opening avenues for understanding and lowering noise emissions during vehicle idling and low-speed operations.

Research on Low Speed Operation of PMSM Based on Improved Non-Singular Fast Terminal SMC

Research on Low Speed Operation of PMSM Based on Improved Non-Singular Fast Terminal SMC

Using numerical simulation methods to analyze the aerodynamic performance of racing tail fins under multiple factor conditions

Abstract. In high-speed ground racing cars, the aerodynamics of the tail wing are crucial as they directly affect the overall performance and results of the car. In the aerodynamic performance of the tail wing, down force and drag are the two most important parameters. In order to study the specific effects of factors such as racing speed, tail wing profile, and tail angle of attack on the aerodynamic performance of the tail wing, fluid dynamics numerical simulation methods were used for research.The research results indicate that within the parameter range of 160km/h to 240 km/h, both resistance and down force continuously increase with the increase of speed, and show a typical linear variation pattern. Within the range of 0 to 35 angle of attack, both drag and down force increase, but within 20 , the increase in down force is faster, and once it exceeds 20 , the increase in drag becomes more pronounced.At the same time, four different airfoil structures were compared and analyzed, and it was concluded that the NACA airfoil is more suitable for low-speed operating conditions, as it can generate higher down force at lower speeds. The research results of this article provide certain reference value for the design and finalization of racing tail fins.

A Study on Ways to Expand the Speed Operation Range of Dental Laboratory Handpiece Motors Using Low-Cost Hall Sensors

In the dental prosthetics field, BLDC micro-motors are primarily used for implant procedures. As dental materials become increasingly harder, there is a growing demand for higher performance motors to precisely process these materials. However, difficulties in motor development arise due to price competitiveness. Dental motors require capabilities such as low-speed, high-torque for drilling operations and high-speed rotation for precise machining of high-strength dental materials. Additionally, there is a requirement to address thermal issues to prevent user burns due to motor-generated heat. Typically, motors requiring precision control utilize high-resolution position sensors like encoders or resolvers to acquire and control the rotor’s position. However, the high cost of these sensors and constraints such as increased device size pose challenges in maintaining price competitiveness. In this paper, we propose a control algorithm that satisfies the requirements for low-speed, high-torque and high-speed operation requirements for precision machining without hardware modifications using a BLDC micro-motor equipped with an inexpensive Hall sensor commonly used in the dental field. Furthermore, the algorithm is designed to ensure stable operation even in the event of Hall sensor failure or malfunction, and its effectiveness is validated through experiments.

Research on Sub-Module Fluctuating Power Decoupling Strategy for Modular Multilevel Converter-Based Medium-Voltage Motor Drive System with Wide Speed Range

There is a problem of excessively large sub-module capacitance in modular multilevel converter (MMC) applications for medium-voltage motor drive systems, which is particularly noticeable during the low-speed operation of the motor. This paper proposes a low-capacitance MMC (LC-MMC) motor drive system based on lateral sub-module interconnection, achieving capacitance lightweighting across the wide speed range of the motor. The LC-MMC is based on the three-phase symmetrical fluctuating current input of the sub-modules in the interconnection channel, achieving their mutual cancellation, thus significantly reducing the sub-module capacitance size. This paper starts from the traditional MMC motor drive system and analyzes its specific requirements for sub-module capacitance. Then, it provides a detailed description of the LC-MMC scheme for achieving capacitance lightweighting across the wide speed range of the motor, and the two MMC motor drive systems are compared and evaluated. The evaluation results show that the volume of the LC-MMC is reduced by nearly 70% compared to a traditional MMC. Finally, the LC-MMC scheme is simulated and experimentally verified.

Pressure Drop in a Metal Foam Centrifugal Breather: A Simulation Approach

One of the main issues faced in the operation of a metal foam centrifugal breather is the high pressure drop. This study investigates the pressure drop of a metal foam centrifugal breather. The numerical simulation research method is adopted. The DPM model is used to calculate the two-phase flow field of the metal foam breather, and the porous medium model is used to replace the metal foam at the breather. The resistance caused by the metal foam is replaced by a distributed resistance added to the fluid. The effects of flow rate, rotational speed, porosity, PPI (pores per inch), and temperature on the pressure drop of the breather are analyzed. The results indicate that rotational speed, flow rate, porosity, and PPI significantly influence the resistance of the metal foam centrifugal breather. The resistance of the breather is directly proportional to the rotational speed, flow rate, temperature, and metal foam pore density, and inversely proportional to the porosity. Temperature has a minor impact on the resistance of the metal foam centrifugal breather. Therefore, the metal foam centrifugal breather is more suitable for low-speed operating conditions.

Performance Evaluation of Hybrid Propulsion System on Fast Patrol Boat

This paper presents a performance evaluation of a hybrid propulsion system applied to a fast patrol boat. The study aims to analyze the efficiency, fuel consumption, and overall operational effectiveness of the hybrid system compared to conventional propulsion methods. A combination of electric motors and diesel engines is utilized in the hybrid setup, allowing for optimized energy use in varying operational conditions. The performance of the system was evaluated through simulation and sea trials, focusing on key metrics such as speed, endurance, maneuverability, and emission reduction. Results indicate that the hybrid system offers significant advantages in terms of fuel savings and reduced environmental impact, particularly during low-speed or patrol operations. This research provides valuable insights into the practical benefits and challenges of implementing hybrid propulsion systems in maritime security operations.

An Analysis of Air Conditioning System Operation Patterns on Droplet Particle Distribution in a Classroom-A CFD Approach

In the classroom context, the transmission of pathogens among students is a significant concern. Therefore, it is important to determine appropriate airflow patterns, the placement of supply and exhaust ventilation, and the optimization of classroom design to reduce the risk of pathogen transmission. This research aims to determine the performance of two air conditioning (AC) operating patterns—low speed and high speed—in six scenarios involving window and door configurations and identify the most effective strategies for minimizing virus exposure to occupants in classrooms. The method used in this research is numerical simulation with the 3D unsteady k-ε RNG model to simulate air flow and the Eulerian-Lagrange approach to capture the movement of SARS-CoV-2 aerosol droplets. The results of this research show that of the six scenarios determined by the researchers, the low-speed AC operating pattern with an incoming air speed of 3.5 m/s occurs in scenario 5, that is, all windows open and doors closed. This is based on the lowest number of students exposed to the virus, which is 22.22%. Meanwhile, the high-speed AC operating pattern with an incoming air speed of 6 m/s occurs in scenario 2, that is, all windows closed and doors open. This is based on the lowest number of students exposed to the virus, which is 22.22%, so it can be concluded that increasing the air flow speed originating from the AC will speed up the droplets to leave the room through the outlet. Meanwhile, increasing the outlet capacity will shorten the particle path, thereby shortening the time when the droplets are in the classroom.

Active flux based adaptive and non-adaptive observer for sensorless interior permanent magnet synchronous machine drive

The use of the interior permanent magnet synchronous machine (IPMSM) drive has profoundly increased in a large number of applications due to numerous advantages. Owing to the disadvantages of mechanical sensors, sensorless control techniques are employed to enhance the performance of the IPMSM drive by removing the effect of noise and gain drift due to the sensor, increasing reliability, cost saving, and reducing overall size. This article presents the comparative analysis between the adaptive observer and non-adaptive extended electromotive force (EEMF) observer based on the active flux concept in a stationary reference frame (α–β). Moreover, the effect of slot harmonics and non-sinusoidal distribution of rotor flux is present in the three-phase IPMSM, this problem is considered as the control system disturbances in this article. Due to the non-sinusoidal distribution of flux and slot harmonics, the observer structure in the rotating reference frame (d–q) fails to estimate at the low-speed operation range. Comparative analysis between adaptive and non-adaptive observer structures is provided for a wide speed range. The effectiveness of the observer structures is examined using the classical field-oriented control scheme. In the end, simulation and experimental results are demonstrated to validate the performance of the sensorless control scheme using the adaptive and non-adaptive observer structures for the three-phase IPMSM drive setup.

Experimental study on the matching relationship of gas wave oscillation tube under liquid-carrying condition

The gas wave oscillation tube (GWOT) transfers energy directly between gases of varying pressures using non-constant motion waves, and its low rotational speed operation offers a broader application potential in two-phase refrigeration compared to turbomachinery. The GWOTs achieve a high performance by optimizing the relationship between tube length, deflection displacement, rotational speed, and incident excitation wave (S1) velocity. However, under the liquid-carrying conditions, the optimizing matching relationship of the GWOTs deviates, leading to a decline in performance, so it is necessary to explore the matching relationship of the high performance of the GWOTs under the liquid-carrying conditions. This study focuses on "spoon" GWOTs, analyzing the impact of rotational speed, liquid-carrying capacity, and deflection displacement on their refrigeration performance under a fixed tube length through experimental analysis. It is found that the refrigeration efficiency at the design parameters of the GWOTs decreases by a maximum of about 25 % with the increase in the amount of liquid-carrying capacity within the study area of this paper, while the refrigeration efficiency can be improved by a maximum of about 8 % by varying the rotational speed. The findings provide valuable insights for enhancing the liquid-carrying performance of the GWOTs and promoting the application expansion of GWOTs in the field of gas-liquid two-phase.

Contribution to Conditional Maintenance by Vibration Analysis of Rotating Machine Mechanical Failures and Proposed Solutions

Objective: The aim of this study is to analyze the Cement Separator machine and identify potential condition indicators through vibration measurements and analysis. The goal is to diagnose and repair the machine before any material damage occurs. Background: Maintenance Technology: Modern maintenance technologies are crucial for monitoring equipment performance and planning timely maintenance interventions. Vibration Monitoring: As a key component in maintenance programs, especially for mechanical systems, vibration monitoring provides early warnings of faults based on the actual state of the machine. Cement Separator Machine: Issue: The cement separator exhibits significant vibrations despite its low operating speed. Data Sources: The construction and operational details of the machine are available from its operating manual and vibration measurements. Methodology: Practical Vibration Measurements: Extensive measurements are performed in a research laboratory and on-site to monitor the machine's condition. Vibration measuring devices are used to monitor rotating machines at specified intervals according to their condition and international standards. Condition Indicators: Various condition indicators are monitored to detect possible deterioration and the onset of mechanical or electrical failures during the machine's operation. Experimental Studies: Practical experiments validate the theoretical and numerical findings and refine the vibration analysis approach. Strategy: Adequate scheduling of interventions and repairs based on the machine's condition. Continuous monitoring through vibration analysis devices. Expected Outcomes: Early detection of potential mechanical or electrical failures. Sustainable solutions to reduce vibrations and enhance the machine's performance. Improved maintenance scheduling to prevent material damage and extend the machine's lifespan. By integrating vibration monitoring and analysis with practical studies, this research aims to provide a comprehensive diagnosis and repair strategy for the cement separator machine.

Practical method for evaluating wind influence on autonomous ship operations (2nd report)

Recently, a considerable number of research and development projects have focused on automatic vessels. A highly realistic simulator is needed to validate control algorithms for autonomous vessels. For instance, when considering the automatic berthing/unberthing of a vessel, the effect of wind in such low-speed operations cannot be ignored because of the low rudder performance during slow harbor maneuvers. Therefore, a simulator used to validate an automatic berthing/unberthing control algorithm should be able to reproduce the time histories of wind speed and wind direction realistically. Therefore, in our first report on this topic, to obtain the wind speed distribution, we proposed a simple algorithm to generate the time series and distribution of wind speed only from the mean wind speed. However, for wind direction, the spectral distribution could not be determined based on our literature surveys, and hence, a simple method for estimating the coefficients of the stochastic differential equation (SDE) could not be proposed. In this study, we propose a new methodology for generating the time history of wind direction based on the results of Kuwajima et al.’s work. They proposed a regression equation of the standard deviation of wind direction variation for the mean wind speed. In this study, we assumed that the wind direction distribution can be represented by a linear filter as in our previous paper, and its coefficients are derived from Kuwajima’s proposed equation. Then, as in the previous report, the time series of wind speed and wind direction can be calculated easily by analytically solving the one-dimensional SDE. The joint probability density functions of wind speed and wind direction obtained by computing them independently agree well with the measurement results.

Experimental analysis of enhanced finite set model predictive control and direct torque control in SRM drives for torque ripple reduction

The magnet-less switched reluctance motor (SRM) speed-torque characteristics are ideally suited for traction motor drive characteristics and its advantage to minimize the overall cost of on-road EVs. The main drawbacks are torque and flux ripple, which have produced high in low-speed operation. However, the emerging direct torque control (DTC) operated magnitude flux and torque estimation with voltage vectors (VVs) gives high torque ripples due to the selection of effective switching states and sector partition accuracy. On the other hand, the existing model predictive control (MPC) with multiple objective and optimization weighting factors produces high torque ripples due to the system dynamics and constraints. Therefore, existing DTC and MPC can result in high torque ripples. This paper proposed a finite set (FS)-MPC with a single cost function objective without weighting factor: the predicted torque considered to evaluate VVs to minimize the ripples further. The selected optimal VV minimizes the SRM drive torque and flux ripples in steady and dynamic state behaviour. The classical DTC and proposed model were developed, and simulation results were verified using MATLAB/Simulink. The proposed model operated in SRM drives experimental results to prove the effective minimization of torque and flux ripples compared to the existing DTC.

Performance improvement of induction motor drives in low-speed operation using gray wolf optimizer based on IFOC

Performance improvement of induction motor drives in low-speed operation using gray wolf optimizer based on IFOC

Experimental and numerical investigation on rotating stall flow pattern in a counter-rotating axial compressor

Rotational stall is a common flow instability phenomenon in axial and centrifugal compressors. The experimental and numerical results of the three-dimensional flow field in a low-speed counter-rotating axial compressor operating in deep rotating stall are presented in this paper. The obtained results provide a detailed description of the flow inside and outside the stall cell. The circumferential flow of the reversed flow upstream and downstream is dominated, respectively, by the counter-rotating front and rear row rotors. The reverse flow downstream reenters the rear row rotor and the front rotor at higher blade heights, undergoing repeated work by the rotors. This leads to the formation of a high-pressure region at the leading edge of stall cell, which is essential for maintaining stall conditions upstream of rotors. Stalls primarily occur in the middle and tip regions with elevated pressure, while the downstream stall cell exhibits significant spreading from hub to tip with some circumferential bias.

Investigation of Hybrid Laminar Flow Control Capabilities from the Flight Envelope Perspective

The present work conducts a multifidelity aerodynamic design of a medium-range commercial aircraft wing featuring hybrid laminar flow control (HLFC) technology. The design was performed to investigate the capabilities of the HLFC, considering the entire design flight envelope, low-speed performance requirements, and various potential mission scenarios. A combination of medium-fidelity aerodynamic design tools for laminar flow control using MSES-COCO-LILO, CFD RANS for high-lift cases, the quasi-three-dimensional for database generations, and SUAVE for mission analysis were used to design and assess aircraft’s performance with the HLFC wing. Studies of the design objective demonstrated a conflict between friction and compressibility drag that strongly affects the design objective function and the wing performance at various off-design conditions. A strong dependence of HLFC on flight conditions was observed to indicate technology performance limitations and a tradeoff between airplane emissions, range, and costs. Finally, a comparison of medium- and low-fidelity performance results showed deviations in the design fuel burn of 4%, a minimum possible harmonic range difference of 3%, and direct operating costs of 2%. The outcome suggests the need for better compressibility and parasite drag models for early design stages to accurately model the HLFC technology without introducing complicated methods at the first sizing steps.

The Design and the Control Principle of a Direct Low-Speed PMSM Servo-Drive Operating under a Sign-Changing Load on the Shaft

The paper relates to the development of an algorithm applicable for maintaining the rotational speed of low-speed drives using PMSM motors and operating under a sign-changing load. The moment of inertia of rotating parts does not play the role of a mechanical stabilizer for the speeds discussed in the article. Simulation studies are presented with the aim of developing a rotational speed control algorithm that utilizes only positional feedback and the previously assumed sign-changing load on the shaft. For the purposes of this research, a mathematical model was developed to calculate transient processes in a PMSM machine operating in the conditions of a sign-changing load on the shaft. This model assumes a deterministic control principle adapted to the known nature of the load change. In this model, the mutual influence occurring between the phase fluxes, the electromagnetic torque, the electric currents and the rotor position angle are established on the basis of FEM analysis of a two-dimensional magnetic field using a quasi-stationary approximation. Principles applicable for controlling a direct low-speed servo drive based on a PMSM machine operating with a known variable shaft load using only positional feedback and a predetermined shaft load change law are defined. The proposed regulation method is verified in an experimental manner. For this purpose, an experimental setup was built, which includes a PMSM with a load imitator on a variable sign shaft, an inverter providing sine-shaped power supply to the machine and a digital dual-processor control system. The discussed rotational speed stabilization algorithm was implemented in the form of a program for a microcontroller, which forms a part of the control system. The results of experimental tests confirm the adequacy of mathematical modeling and the effectiveness of the proposed rotational speed stabilization algorithm.

Experimental and Numerical Investigation of Bogie Hunting Instability for Railway Vehicles Based on Multiple Sensors.

Bogie hunting instability is one of the common faults in railway vehicles. It not only affects ride comfort but also threatens operational safety. Due to the lower operating speed of metro vehicles, their bogie hunting stability is often overlooked. However, as wheel tread wear increases, metro vehicles with high conicity wheel-rail contact can also experience bogie hunting instability. In order to enhance the operational safety of metro vehicles, this paper conducts field tests and simulation calculations to study the bogie hunting instability behavior of metro vehicles and proposes corresponding solutions from the perspective of wheel-rail contact relationships. Acceleration and displacement sensors are installed on metro vehicles to collect data, which are processed in real time in 2 s intervals. The lateral acceleration of the frame is analyzed to determine if bogie hunting instability has occurred. Based on calculated safety indicators, it is determined whether deceleration is necessary to ensure the safety of vehicle operation. For metro vehicles in the later stages of wheel wear (after 300,000 km), the stability of their bogies should be monitored in real time. To improve the stability of metro vehicle bogies while ensuring the longevity of wheelsets, metro vehicle wheel treads should be reprofiled regularly, with a recommended reprofiling interval of 350,000 km.