Low Speed Research Articles

Sensorless control method of induction motors with new feedback gain matrix and speed adaptive law for low speed range

Abstract The conventional adaptive full-order observer-based speed sensorless control method for induction motor is prone to instability at low-speed region as improper feedback gain matrix and imprecise speed adaptive law are often used. To address these problems, a new feedback gain matrix design approach as well as a new speed adaptive law design technique are proposed in this paper. Firstly, considering that the d-axis current estimation error in the traditional feedback gain matrix design method has a great influence on the stability of the speed estimation algorithm, especially at low speeds, a new feedback gain matrix design method is proposed to minimize the d-axis current estimation error. Secondly, a new speed adaptive law design technique is studied based on the conventional method, which only requires the d-axis and q-axis current estimation error with a weight coefficient to be designed, simplifying the conventional speed adaptive law. Thirdly, the transfer function from the speed observation error to the proposed adaptive error is analyzed by Routh stability criterion theory, and the weight coefficient suitable for full range stable operation is determined by MATLAB software. Fourthly, the stability of the proposed method in this paper is analyzed using the poles distribution maps. Finally, the proposed method is experimentally verified based on a 2.2 kW induction motor experimental platform. The experimental results show that the proposed method can make the induction motor operate steadily at low-speed and zero-speed region with rated load. In addition, the proposed method has better anti-disturbance performance than the existing method.

Tumor-Derived Exosomes Promote Tumor Growth Through Modulating Microvascular Hemodynamics in a Human Ovarian Cancer Xenograft Model.

Abnormal tumor vascular network contributes to aberrant blood perfusion and reduced oxygenation in tumors, which lead to poor efficacy of chemotherapy and radiotherapy. We aimed to explore the effects of the tumor-derived exosomes (TDEs) and C188-9 (a small molecule inhibitor of signal transducer and activator of transcription 3, STAT3) on tumor microvascular hemodynamics and determine which blood flow oscillations for various frequency intervals are responsible for these changes. Microvascular hemodynamics parameters were recorded using a PeriFlux 6000 EPOS system in tumor surface in a nude mouse subcutaneous xenograft model. Oscillations of laser Doppler flowmetry (LDF) signal were investigated by wavelet transform analysis. TDEs facilitated tumor growth at least partially was associated with increasing blood flow in smaller vessels with lower speed and decreasing the blood flow at larger vessels with higher speed. Lower oxyhemoglobin saturation (SO2) on tumor surface was aggravated by TDEs, and C188-9 treatment significantly alleviated this decrease. Wavelet transform spectral analysis revealed that TDEs increased the amplitude of oscillations in four frequency intervals related to endothelial (NO-dependent and -independent), myogenic and neurogenic activities, and C188-9 had no effect on this increase. TDEs facilitated tumor growth partially was associated with increasing blood flow in distributing vessels, reducing blood perfusion in larger vessels, and lowering SO2 on tumor surface. Enhanced vascular smooth muscle, endothelial and neurogenic activities occurred in tumor superficial zone.

Optimization of operating parameters of a drum-type feed metering unit developed for a human-powered floating fish feeder

Feed wastage is one of the major concerns in aquaculture practice. A simple and unique floating fish feeder with drum-type metering mechanism was developed, which addresses this concern. A drum-type metering mechanism is an easy, effective, low cost metering method with low energy requirement. Optimizing the feed rate for any metering systems is a necessary pre-requisite to ensure proper feeding. In this study, the operating parameters of the drum-type feed metering unit have been optimized to achieve the desired feed rate. The influence of three independent parameters (number of metering holes, shaft speed and drum fill level) on the dependent parameter (feed rate) was studied and optimized using response surface methodology. A multilevel full factorial design approach has been adopted for the experimental design. The effect of variation in operating parameters was investigated experimentally and a response surface model was developed from experimental data. The fit of the model was expressed by an R2 value of 0.879. The optimal solutions obtained from the model with high desirability values were further used for validation experiments in aquaculture pond and found to be acceptable. It was observed that low shaft speeds and drum fill levels led to better feeding. The best settings recommended for the feeder operation were 24 metering holes, 31 % drum fill level and 30 rpm shaft speed. The feeder was found to improve feed application and reduce feed wastage. This kind of low-cost feeding systems is expected to encourage adoption of mechanized feeding among small and marginal farmers.

Дослідження впливу зовнішніх факторів на експлуатаційні властивості електромобіля

Many factors affect the range of an electric vehicle: speed, driving style and ambient temperature can reduce the range of a full charge. Cold weather poses two main problems for electric vehicles: cold air limits battery performance, and the robo-heater significantly drains the battery. Studies have shown that 21.5 degrees is the optimal temperature for the operation of an electric car battery. Because an average of 21.5 degrees Celsius is the most optimal temperature when it comes to the range of an electric car. This actually prolongs its operation. At 21.5 degrees, the electric car's temperature system does not work, so energy is used for its movement. At -20°C, an electric car loses an average of 50% of its battery charge range. At -10 – 40%, at 0 – 20%. When the temperature is +10o C, the real driving distance of the electric car corresponds to 100% charging of the battery. At +21 o C, the real distance can be increased to 15%. When it is +40oC, the performance of the battery drops significantly to 80%, and the rate of charge rapidly decreases as the temperature increases. The energy consumption of electric vehicles is largely influenced by weather factors. Studies have shown the influence of ambient temperature and wind speed on energy consumption. The results show that at low speeds (30 km/h) the relative influence of ambient temperature is extremely high. The lowest energy consumption is achieved at a temperature of 20° C. At higher speeds (130 km/h), the relative influence of the temperature of the external environment is much lower. It has been proven that 21.5 degrees is the optimal ambient temperature for the operation of an electric car battery during operation, a decrease or increase in temperature leads to a decrease in the efficiency of electric car operation.

Development and validation of the Thai version of MNREAD acuity charts.

To develop and validate MNREAD acuity charts in the Thai language (MNREAD-TH). In total, 180 Thai sentences were generated using words specific to the primary 1-3 students. Each sentence contained 60 characters divided into three lines with even left and right margins and was evaluated by instructors in the education program in Thai. The selected 118 sentences were tested in 20 adults and 20 children by measuring reading time and recording the errors. Sentences with extremely high or low mean reading speeds were excluded. The remaining sentences were selected for contributing to the MNREAD-TH charts. For validation, the charts were tested in another 20 normal-sighted adult groups. In total, 118 sentences were tested on 20 adults (range: 23-58 years) and 20 primary school students (age: 8-9 years). The mean (SD) reading speeds in adult and children's groups were 134.09 (12.45) and 71.33 (10.77) words/min (wpm), respectively. After removing the sentences that deviated by ±1 SD from the mean reading speed, repeatedly had difficulty words, and had low subjective scoring, 60 matched sentences between the groups were selected to develop three versions of the MNREAD-TH chart. The intraclass correlation coefficients between charts were 0.85 for reading acuity, 0.94 for maximum reading speed, and 0.79 for critical print size. The MNREAD-TH charts can be reliably used for evaluating reading performance in Thai people for both children and adults with either normal sight or low vision. These charts are standardized and helpful in clinical trials involving reading.

Age-related and experience-related differences in selected motor cognitive abilities of soccer players

Background: Soccer players constantly experience rapidly changing situations that challenge them to receive and process stimuli, make fast and correct decisions, and perform actions at specific moments. The aim of the present study was to analyze age and experience-related differences in the level of brain speed, disjunctive reaction time, and reaction speed of soccer players. Methods: A total of 111 soccer players (x=12.414; s=1.921) divided by age and level of experience participated in the study. The diagnosis of brain speed and disjunctive reactivity was carried out with the BrainHQ Hawk Eye test and BrainHQ Agility test using the Witty Sem system. Reaction speed was diagnosed with the Fitro Agility Check test using the Fitro Agility system. The Mann-Whitney U test and the Kruskal-Wallis analysis of variance were used to determine the significance of age and experiencerelated differences in the level of brain speed, disjunctive reaction time, and reaction speed of the soccer players. Results and conclusion: Statistically significant differences (p<0.01) in favor of older age categories were observed between disjunctive reaction time and brain speed. Younger soccer players showed significantly lower levels of lower limb reaction speed in both directions of the sagittal plane than older players (p<0.01). Less experienced soccer players demonstrated significantly lower levels of lower limb reaction speed in both directions of the sagittal plane than more experienced counterparts and lower levels of brain speed and disjunctive reaction time (p<0.01).

Effects of axial electric and transverse magnetic fields on a rotating electro-osmotic flow in micro-parallel plates

This paper explores the combined influence of an axial electric field and a perpendicular magnetic field imposed on rotating micro-parallel plates immersed in an electrolyte solution. A specialized computer program was developed to solve the velocity as well as the EDL potential fields using the finite difference method, employing the Debye-Hückel (DH) approximation to linearization the EDL potential. The study examines the influence of various non-dimensional parameters, including rotational speed (ω), Hartmann number (Ha), Debye-Hückel parameter (κ), and the non-dimensional parameter ‘S’, on axial, and transverse velocities, wall shear stress, and net flow rate. Results demonstrate that, both velocity components decrease with increased rotational speed and Hartmann number, while the net flow rate increases with the Debye-Hückel parameter for both rotating and non-rotating systems. The impact of these parameters on shear stress was also analyzed. Analysis of Ekmann spirals in the velocity plane revealed closed spirals at a higher rotational speed and open spirals at lower speeds, with spiral size reducing as rotational speed increases.

Friction and Wear Performance of a Hydraulic Motor Roller/Piston Pair Contact lined with the Self-Lubricating Bearing Bush Modified by PEEK

Poly Ether Ether Ketone (PEEK) is a kind of special engineering plastic with excellent properties such as high-temperature resistance, self-lubrication, wear resistance, and high mechanical strength. However, its blending or composite modification applications still face numerous challenges. The primary objective of this research was to evaluate the friction and wear performance of a three-layer self-lubricating bearing bush, which was made from a modified material containing short carbon fiber and Poly Ether Ether Ketone (SCF/PEEK). The bearing bush is used as a surface contact layer on the pistons of a hydraulic motor in the interface with the cam roller. The bearing bush was processed using a 15% SCF-modified PEEK material, and the friction and wear test was conducted using a self-built friction test machine. This study aimed to assess the frictional and wear characteristics of the SCF/PEEK-modified material in the bearing bush. The results show that as the experimental pressure rises from 15 MPa to 25 MPa, the friction coefficient of the SCF-modified bearing bush experiences a significant decrease from 0.420 to 0.296. Furthermore, the stability of the frictional morphology of carbon fibers indicates its effective adaptability to low speed and high load conditions.

Thermodynamic Study on the Vortex Teeth of Electric Scroll Compressors Based on Gradient Tooth Height

Through the analysis of the adhesion between the tooth head and axial clearance leakage attributed to vortex tooth shape deformation, an innovative tooth shape design concept has been introduced entitled “progressive change tooth high vortex tooth”. This unique design includes a gradual change in tooth height and an elevated vortex tooth profile, using temperature-sensitive materials to enhance the resolution of temperature loading on the vortex disc. By refining the process of resolving the temperature loading on the vortex disc, the mean temperature function of the fluid domain along the wall of the vortex tooth is calculated, and a steady-state temperature distribution model for the solid domain of the vortex tooth is formulated. Subsequently, a finite element model for the high eddy current disc is constructed using Abaqus 2021 finite element software, which facilitates the calculation of stress–strain distribution within the high eddy current disc under both gas pressure and temperature field loads. The results show that, especially under conditions of low speed and low exhaust pressure, the temperature load mainly influences the maximum deformation and stress distribution of the vortex tooth. Specifically, under the influence of heat-solid coupling, the maximum deformation of the progressive change tooth high vortex tooth occurs in close proximity to the central compression cavity, reaching up to 13 microns. These results provide a crucial theoretical basis for the structural design and performance optimization of the compressor.

Thermodynamic Study on the Vortex Teeth of Electric Scroll Compressors Based on Gradient Tooth Height

Through the analysis of the adhesion between the tooth head and axial clearance leakage attributed to vortex tooth shape deformation, an innovative tooth shape design concept has been introduced entitled “progressive change tooth high vortex tooth”. This unique design includes a gradual change in tooth height and an elevated vortex tooth profile, using temperature-sensitive materials to enhance the resolution of temperature loading on the vortex disc. By refining the process of resolving the temperature loading on the vortex disc, the mean temperature function of the fluid domain along the wall of the vortex tooth is calculated, and a steady-state temperature distribution model for the solid domain of the vortex tooth is formulated. Subsequently, a finite element model for the high eddy current disc is constructed using Abaqus 2021 finite element software, which facilitates the calculation of stress–strain distribution within the high eddy current disc under both gas pressure and temperature field loads. The results show that, especially under conditions of low speed and low exhaust pressure, the temperature load mainly influences the maximum deformation and stress distribution of the vortex tooth. Specifically, under the influence of heat-solid coupling, the maximum deformation of the progressive change tooth high vortex tooth occurs in close proximity to the central compression cavity, reaching up to 13 microns. These results provide a crucial theoretical basis for the structural design and performance optimization of the compressor.

Charge generation by passive plant leaf motion at low wind speeds: design and collective behavior of plant-hybrid energy harvesters

Energy harvesting techniques can exploit even subtle passive motion like that of plant leaves in wind as a consequence of contact electrification of the leaf surface. The effect is strongly enhanced by artificial materials installed as ‘artificial leaves’ on the natural leaves creating a recurring mechanical contact and separation. However, this requires a controlled mechanical interaction between the biological and the artificial component during the complex wind motion. Here, we build and test four artificial leaf designs with varying flexibility and degrees of freedom across the blade operating on Nerium oleander plants. We evaluate the apparent contact area (up to 10 cm2 per leaf), the leaves’ motion, together with the generated voltage, current and charge in low wind speeds of up to 3.3 m s−1 and less. Single artificial leaves produced over 75 V and 1 µA current peaks. Softer artificial leaves increase the contact area accessible for energy conversion, but a balance between softer and stiffer elements in the artificial blade is optimal to increase the frequency of contact-separation motion (here up to 10 Hz) for energy conversion also below 3.3 m s−1. Moreover, we tested how multiple leaves operating collectively during continuous wind energy harvesting over several days achieve a root mean square power of ∼6 µW and are capable to transfer ∼80 µC every 30–40 min to power a wireless temperature and humidity sensor autonomously and recurrently. The results experimentally reveal design strategies for energy harvesters providing autonomous micro power sources in plant ecosystems for example for sensing in precision agriculture and remote environmental monitoring.

The Motion Estimation of Unmanned Aerial Vehicle Axial Velocity Using Blurred Images

This study proposes a novel method for estimating the axial velocity of unmanned aerial vehicles (UAVs) using motion blur images captured in environments where GPS signals are unavailable and lighting conditions are poor, such as underground tunnels and corridors. By correlating the length of motion blur observed in images with the UAV’s axial speed, the method addresses the limitations of traditional techniques in these challenging scenarios. We enhanced the accuracy by synthesizing motion blur images from neighboring frames, which is particularly effective at low speeds where single-frame blur is minimal. Six flight experiments conducted in the corridor of a hydropower station demonstrated the effectiveness of our approach, achieving a mean velocity error of 0.065 m/s compared to ultra-wideband (UWB) measurements and a root-mean-squared error within 0.3 m/s. The results highlight the stability and precision of the proposed velocity estimation algorithm in confined and low-light environments.

The Motion Estimation of Unmanned Aerial Vehicle Axial Velocity Using Blurred Images

This study proposes a novel method for estimating the axial velocity of unmanned aerial vehicles (UAVs) using motion blur images captured in environments where GPS signals are unavailable and lighting conditions are poor, such as underground tunnels and corridors. By correlating the length of motion blur observed in images with the UAV’s axial speed, the method addresses the limitations of traditional techniques in these challenging scenarios. We enhanced the accuracy by synthesizing motion blur images from neighboring frames, which is particularly effective at low speeds where single-frame blur is minimal. Six flight experiments conducted in the corridor of a hydropower station demonstrated the effectiveness of our approach, achieving a mean velocity error of 0.065 m/s compared to ultra-wideband (UWB) measurements and a root-mean-squared error within 0.3 m/s. The results highlight the stability and precision of the proposed velocity estimation algorithm in confined and low-light environments.

Study on cold start of fuel cell stack combined with liquid heating and fuel cell self-starting

Fuel cell vehicles have been paid more and more attention, while the low temperature cold start capability has become the main reason that hinders their large-scale commercialization, especially for the fuel cell bus. Generally, liquid heating (positive temperature coefficient thermistor (PTC) as the heat source) and fuel cell self-starting heating are the common cold start methods. However, these methods can bring about low start speed and high energy consumption. Therefore, a new cold start method combined with liquid heating and fuel cell self-starting is proposed to solve the problems. Besides, phase change material (PCM) is introduced to reduce energy consumption further. The PCM can absorb the waste heat of the fuel cell stack. Then the heat can be used for stack cold start by circulating liquid. In this study, a fuel cell bus cold start system simulating model is built. Based on this model, the fuel cell temperature and energy consumption during the cold start are analyzed. The results show that the method combined with liquid heating and fuel cell self-starting is superior to the liquid heating method. The cold start time and PTC consumption of the PTC-PCM-self-starting heating mode are 19.0 % and 19.2 % less than that of PTC-PCM heating mode. As for the combined heating method, dropping the self-starting temperature can not only increase the cold start speed but also reduce the proportion of electric heating. For every 1 °C decrease, the start-up time is shortened by 1 % on average, and the waste heat utilization rate is increased by 0.5 %. Although increasing the self-starting current can increase energy consumption, it will save more cold start time and reduce the proportion of electric heating. For every 1 A increase, the start-up time is shortened by 0.3 % on average, and the waste heat utilization rate is increased by 0.1 %. The PTC-PCM-self-starting heating method provides a way for fuel cell stack to start quickly and energy-efficiently in low temperature environment.

Large-eddy simulations of turbulent wake flows behind helical- and straight-bladed vertical axis wind turbines rotating at low tip speed ratios

Large-eddy simulations of turbulent wake flows behind helical- and straight-bladed vertical axis wind turbines rotating at low tip speed ratios

Exploring the effects of traffic light countdown displays on the driving behaviours of drivers with different personality dispositions: A VR-simulated study

The dilemma zone, where drivers must decide whether to stop or proceed through an intersection as a traffic signal turns yellow, poses a substantial risk for traffic accidents. One factor affecting the dilemma zone is the inconsistency of green light countdown displays across intersections. This VR simulation study aims to investigate how different countdown display settings impact driver behaviour in the dilemma zone. Using a simulated traffic intersection developed using Unity3D, 31 participants completed driving tasks under 5 different green light countdown displays. Vehicle speeds were collected objectively in the experiments. Questionnaires were employed to assess drivers' hesitation levels and personality dispositions. The results from the statistical analysis reveal that drivers with diverse personality dispositions exhibited consistent hesitation levels across countdown displays. While longer countdown displays tended to reduce drivers' hesitation, the countdowns set between 5-10 seconds resulted in lower vehicle speeds through the intersection compared to other shorter or longer settings. This indicates that the optimal green light countdown display for mitigating the dilemma zone is 5-10 seconds. Findings of the study provide useful insights into the relevant research field. Transportation departments may apply these findings to improve driver safety, refine policies, and standardise countdown timers across intersections.

Adaptive Speed Control Scheme Based on Congestion Level and Inter-Vehicle Distance

Cellular vehicle-to-everything (C-V2X) enables short-distance communication between vehicles and other users to improve road safety through data sharing. Conventional research on C-V2X typically assumes that vehicles travel at the same speed with a fixed inter-vehicle distance (Disinter). However, this assumption does not reflect the real driving environment or promote road traffic efficiency. Conversely, assigning different speeds to vehicles without a structured approach inevitably increases the collision risk. Therefore, determining appropriate speeds for each vehicle in the C-V2X framework is crucial. To this end, considering the road environment and mobility, this study introduces an adaptive speed mechanism based on the congestion level of a zone and Disinter. First, the given scenario is divided into several zones. Subsequently, based on the congestion level of a zone and the Disinter level, an adaptive speed is defined for each vehicle. This approach ensured that vehicles adopt lower speeds in congested situations to reduce the collision probability and higher speeds in sparse traffic cases to improve traffic efficiency. The performance of the proposed adaptive speed scheme is compared with that of conventional fixed-speed settings. The results show that the adaptive speed control scheme outperforms conventional fixed-speed schemes in terms of the packet reception ratio (PRR) and collision ratio (CR). Specifically, the proposed mechanism can reduce the CR to 0 and ensure that the PRR is higher than 0.98 in low-density scenarios.

Effects of Wind Speed and Heat Flux on De-Icing Characteristics of Wind Turbine Blade Airfoil Surface

The icing on wind turbines reduces their aerodynamic performance and can cause other safety issues. Accordingly, in this paper, the de-icing characteristics of a wind turbine blade airfoil under different conditions are investigated using numerical simulation. The findings indicate that when the de-icing time is 10 s, the peak ice thickness on the leading edge of the airfoil surface decreases from 0.28 mm to 0.068 mm and from 0.77 mm to 0.45 mm at low (5 m/s) and high (15 m/s) wind speeds, respectively. This is due to the fact that the ice melting rate is much greater than the icing rate at low wind speeds, while the icing rate increases at high wind speeds. When the de-icing time is 20 s, ice accretion on the leading edge of the airfoil is completely melted. At a low heat flux (8000 W/m2) and high heat flux (12,000 W/m2), the peak ice thickness decreases by 31.2% and 64.9%, respectively. With an increase in de-icing time and heat flux, the peak thickness of runback ice increases. This is due to an increase in runback ice as a result of more ice melting on the leading edge of the airfoil. The surface temperature in the ice-free area is significantly higher than that in the ice-melting area, due to high thermal resistance in the ice-free area. This study will provide guidance for the thermal distribution and coating layout of a wind turbine blade airfoil to make the anti-/de-icing technology more efficient and energy-saving.

Effects of Wind Speed and Heat Flux on De-Icing Characteristics of Wind Turbine Blade Airfoil Surface

The icing on wind turbines reduces their aerodynamic performance and can cause other safety issues. Accordingly, in this paper, the de-icing characteristics of a wind turbine blade airfoil under different conditions are investigated using numerical simulation. The findings indicate that when the de-icing time is 10 s, the peak ice thickness on the leading edge of the airfoil surface decreases from 0.28 mm to 0.068 mm and from 0.77 mm to 0.45 mm at low (5 m/s) and high (15 m/s) wind speeds, respectively. This is due to the fact that the ice melting rate is much greater than the icing rate at low wind speeds, while the icing rate increases at high wind speeds. When the de-icing time is 20 s, ice accretion on the leading edge of the airfoil is completely melted. At a low heat flux (8000 W/m2) and high heat flux (12,000 W/m2), the peak ice thickness decreases by 31.2% and 64.9%, respectively. With an increase in de-icing time and heat flux, the peak thickness of runback ice increases. This is due to an increase in runback ice as a result of more ice melting on the leading edge of the airfoil. The surface temperature in the ice-free area is significantly higher than that in the ice-melting area, due to high thermal resistance in the ice-free area. This study will provide guidance for the thermal distribution and coating layout of a wind turbine blade airfoil to make the anti-/de-icing technology more efficient and energy-saving.

Exploring dispersion modelling for resuspended pollen particles in a heterogeneous urban environment

ABSTRACT Urban air quality assessment in regard to biogenic emissions such as airborne pollen grains (PGs) is indispensable in the urban environment which significantly affects human health, climates, ecosystems, and energy production. Dispersion and deposition of PGs because of resuspension events (ReSE) are investigated using computational fluid dynamics (CFD). The mechanisms in PGs movement are achieved through the Lagrangian formulation-based discrete-phase model (DPM). The observed pollen grains distribution pattern is highly spatially dependent on heterogeneous urban obstacles as it induces modified characteristics of the wind flow field. Wind-urban structure interplays in PGs concentration variation. The simulated results identify the pollen hot-spot zones, where vortical flow features and low wind speed dominate. This approach offers a detailed understanding of the dispersion patterns of airborne PGs in urban environments because of ReSE with high resolution.