Low Speed Range Research Articles

Assessing the speed of individual bacteria dispersing on mycelial networks

Abstract The movement of bacteria on the hyphae of fungi and other mycelial-forming organisms is an important process that determines their ability to actively disperse in water-unsaturated habitats. However, direct observation and characterization of bacterial cell movement on mycelial networks have been difficult to achieve. In this study, we developed a new method that uses high-speed video recording to track the dispersal of individual fluorescently tagged cells of two closely related strains of Pseudomonas putida (UWC1 and KT2440) over the mycelial network of the oomycete Pythium ultimum. We found high intra-population heterogeneity and between-population differences in dispersal speeds for the two bacterial strains. The fitting of the speed distribution functions led to the separation of speeds into two ranges (fast/slow) at an intersection of the fitted curves. In the lower speed range, the UWC1 strain dispersed faster, while the KT2440 strain moved faster in the higher speed range. This finding helps explain conflicting competition outcomes revealed in previous studies and suggests that population mean speed alone does not capture key aspects of bacterial dispersal in mycelial networks. Our new method opens the possibility of studying bacterial dispersal, competition, and other social interactions in spatially heterogeneous environments, such as soils.

An Uncoupled Search Coil for IPMSM Rotor Position Detection in Low-Speed Range

An Uncoupled Search Coil for IPMSM Rotor Position Detection in Low-Speed Range

Study and Simulation of Switched Reluctance Motor Drive Circuit for EV Application

In recent years, an increase in emissions and a decrease in fossil fuels cause environmental pollution and its main air pollution, so we must restore the emissions of vehicles, and this can be achieved with the help of electric propulsion. An electric vehicle is a vehicle powered by an electric motor and powered by a rechargeable battery that can be charged with electricity. It also promotes the use of renewable energy. A rare earth magnet is a primary requirement for most engines. China is the supplier of more than 90% of rare earth magnets in the world and its price is high due to the scarcity of this magnet. So, we need to reduce the use of magnets and this can be achieved by using SRM motors in electric cars due to their reliable structure, high speed, fault tolerance and magnet less design. The main disadvantages of SRM are torque ripple, low power density, low power factor and small extended speed range. To solve this problem, we use an asymmetric bridge converter topology for a 0.5 kW, 2000 rpm, 8/6 SRM drive. Thus, the analysis and problem of Switched Reluctance Motor and the use of power transformers to minimize torque ripple were identified using Ansys Maxwell software (RMxprt tool).

Experimental verification of changes in the control map of a diesel engine operation due to fuel consumption

The paper describes an experiment related to the introduction of changes in the control software of a supercharged diesel engine in order to reduce fuel consumption, as a measure of useful efficiency. The map shaping the torque in the range of low and medium engine speeds was modified. The fuel dose for a specific engine speed at maximum engine load was changed and the boost pressure was increased, without exceeding the permissible values. A vehicle from the age group of 16 years - typical for the automotive market in Poland, was selected for the tests. It meets the EURO 5 standard. The experiment was carried out on a chassis dynamometer and in road traffic conditions. The average fuel consumption was obtained lower by 0.4 dm3 per 100 km than the factory assumed.

Geometrically nonlinear wind-induced vibration piezoelectric energy harvester based on vortex-induced vibration

This paper proposes a geometrically nonlinear wind-induced vibration piezoelectric energy harvester (WIVPEH) with a maximum size of only 80 mm. Introducing nonlinearity solely through geometric structure design reduces the overall stiffness of the system, enabling the device to excite multi-mode coupling and induce internal resonance even under low wind speed conditions, thereby broadening the bandwidth. Wind tunnel experiments demonstrated that the device could vibrate at a wind speed of 1.5 m/s. Under low wind speed, the piezoelectric output is about 4 times greater than that of ordinary devices. Our research indicates that the designed device can maintain efficient wind energy collection within a low wind speed range.

Numerical Simulation on Lubrication and Experiment Study on Tribology Improvement of Slipper Pair at Low Speeds

A mixed lubrication model for the slipper pair of an electric piston pump is proposed to solve problems such as inadequate lubrication, extreme friction, and wear at near-zero and low speeds. The lubrication characteristics of the slipper pair were numerically calculated and simulated, and the frictional characteristics in the low-speed range were analyzed. A self-lubricating and antiwear slipper pair was developed to mitigate severe friction and wear at near-zero and low speeds. To improve the tribological properties of slippers, various concentrations of molybdenum disulfide (MoS2) powder mixed with epoxy resin (EP) were used as self-lubricating materials. The content of MoS2 ranged from 1 and 20 wt%. The optimal content of MoS2 was obtained by conducting frictional tests on the slipper pair samples as well as material examination and analysis of the slipper sample surfaces before and after the surface characterization tests. The lubrication mechanisms of the self-lubricating and antiwear slippers were determined. The EP/MoS2 composite lubricating materials exhibited excellent self-lubricating and antiwear properties, providing a new direction for the optimized design of slipper pairs and other important friction pairs in piston pumps and promising research prospects.

Experimental and numerical studies on performance investigation of a diesel engine converted to run on LPG

With the growing environmental concerns and depletion of energy resources, considerable efforts are focused on developing ecofriendly and sustainable transportation systems. This includes the conversion of outdated diesel engines into ecofriendly liquefied petroleum gas (LPG) engines. In this study, a Euro-6 diesel engine mounted on a commercial vehicle (mega truck) was converted into a propane LPG engine. The combustion chamber was modified by changing the piston shapes (PSs), compression ratios (CRs), ignition system, throttle body, and injector design to enable operation using propane. The performance of the modified engines with two different PSs, PS1 and PS2, were experimentally investigated. In terms of the power, the engine designed using PS2 demonstrated better performance than PS1 under all operating speeds, except 2600 rpm. Particularly, PS2 outperformed PS1 by more than 10 Nm in the low-speed range of 1000–1600 rpm. Under full load, the PS2-equipped LPG engine achieved the maximum torque and power of 834 Nm at 1600 rpm and 170 kW at 2600 rpm, achieving 106 % and 86 % of the target torque and power, respectively. Additional exhaust gas emission tests were performed using the PS2-equipped LPG engine. The engine performance varied with the application of exhaust-gas recirculation. Moreover, the results of the world-harmonized stationary cycle mode tests confirmed the conformance of the modified LPG engine to all Euro-6 emission standards. Furthermore, simulation-based performance optimization was conducted considering two PSs and four CRs. Based on the simulations, PS1 achieved higher engine performance and lower CO2 and soot emissions, whereas PS2 had lower NO emissions. Additionally, increasing the CR improved the performance and reduced the CO2 and soot emissions for both PSs. These results indicate the possibility of developing LPG engines with performance comparable to diesel engines. In particular, the modified LPG engine proposed in this work may be installed on buses and trucks in the future and is anticipated to replace outdated medium-generator and marine engines.

Sensorless control in full speed domain of interior permanent magnet synchronous motor based on hybrid observer

Aiming at the problem that an Interior Permanent Magnet Synchronous Motor (IPMSM) cannot be smoothly started in zero-low speed range and smoothly transitioned to medium-high speed range by a single observer. This paper proposes a full-speed range control algorithm based on the fusion of pulsating high-frequency injection and back electromotive force (EMF) position error information. In the low-speed range or at start-up, a square-wave high-frequency signal is injected, and the obtained high-frequency current signal is processed to obtain the rotor position error information. The phase shift due to the introduction of a filter is reduced, which improves the control bandwidth and reduces the noise. To ensure smooth switching of the observer, the observer uses a dual second-order generalized integrator module to output the angular frequency in the low-speed range. A higher-order sliding mode observer based on an inverse EMF model obtains rotor position error information at high speeds. During switching, the rotor position information is processed by a fusion strategy, and the obtained hybrid information is fed into the system to improve the stability of the motor operation. A 0.2 kW IPMSM position sensorless vector control system verifies the algorithm’s accuracy.

Reducing Noise and Impact of High-Frequency Torque Ripple Caused by Injection Voltages by Using Self-Regulating Random Model Algorithm for SynRMs Sensorless Speed Control

For the sensorless control in a low-speed range of synchronous reluctance motors (SynRMs), injecting random high-frequency (HF) square-wave-type voltages has become a widely used and technologically mature method. It can solve the noise problem of traditional injection signal methods. However, all injection signal methods will cause problems such as torque ripple, which causes speed fluctuations. This article proposes a self-regulating random model algorithm for the random injection signal method, which includes a quantity adaptive module for adding additional random processes, an evaluation module for evaluating torque deviation degree, and an updated model module that is used to receive signals from the other two modules and complete model changes and output random model elements. The main function of this algorithm is to create a model that updates to suppress the evaluation value deviation based on the evaluation situation and outputs an optimal sequence of random numbers, thereby limiting speed bias always in a small range; this can reduce unnecessary changes in the output value of the speed regulator. The feasibility and effectiveness of the proposed algorithm and control method have been demonstrated in experiments based on a 5-kW synchronous reluctance motor.

Analysis and structural optimization of tree-type dynamic pressure groove mechanical seal performance

Abstract This study investigates the influence of the order and groove ratio of a tree-shaped groove on the sealing performance of a mechanical seal system using numerical simulations. A three-dimensional geometric model of the tree-shaped groove is established using SOLIDWORKS, and the mesh is divided in ANSYS Meshing before being imported into Fluent software for analysis. The single-factor experimental method is employed to evaluate the impact of different parameters on the opening force and leakage rate by varying one parameter while keeping others constant. The simulation results reveal that in the low-speed range, the tree-shaped groove with a groove ratio of 3:4:5 exhibits a larger opening force. Conversely, in the high-speed range, the three-stage tree-shaped groove with a groove ratio of 1:1:1 demonstrates a lower leakage rate and a larger opening force. The findings highlight the significant impact of the order and groove ratio of the tree-shaped groove on the sealing performance of the non-contact mechanical seal. The three-stage tree-shaped groove outperforms the second and fourth stages in terms of mechanical sealing performance, particularly in regard to the opening force. This study provides valuable insights into optimizing the design of tree-shaped grooves in mechanical seal systems to enhance their overall performance and efficiency.

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.

The Two-Parameter Bifurcation and Evolution of Hunting Motion for a Bogie System

The complex service environment of railway vehicles leads to changes in the wheel–rail adhesion coefficient, and the decrease in critical speed may lead to hunting instability. This paper aims to reveal the diversity of periodic hunting motion patterns and the internal correlation relationship with wheel–rail impact velocities after the hunting instability of a bogie system. A nonlinear, non-smooth lateral dynamic model of a bogie system with 7 degrees of freedom is constructed. The wheel–rail contact relations and the piecewise smooth flange forces are the main nonlinear, non-smooth factors in the system. Based on Poincaré mapping and the two-parameter co-simulation theory, hunting motion modes and existence regions are obtained in the parameter plane consisting of running speed v and the wheel–rail adhesion coefficient μ. Three-dimensional cloud maps of the maximum lateral wheel–rail impact velocity are obtained, and the correlation with the hunting motion pattern is analyzed. The coexistence of periodic hunting motions is further revealed based on combined bifurcation diagrams and multi-initial value phase diagrams. The results show that grazing bifurcation causes the number of wheel–rail impacts to increase at a low-speed range. Periodic hunting motion with period number n = 1 has smaller lateral wheel–rail impact velocities, whereas chaotic motion induces more severe wheel–rail impacts. Subharmonic periodic hunting motion windows within the speed range of chaotic motion, pitchfork bifurcation, and jump bifurcation are the primary forms that induce the coexistence of periodic motion.

Improving Output Power of a Torsional-Flutter Harvester in Stochastic Thunderstorms by Duffing - Van Der Pol Restoring Torque

Abstract Wind energy harvesters are usually designed to operate in the low wind speed range. They rely on smaller swept areas, as a complement to larger horizontal-axis wind turbines. A torsional-flutter-based apparatus is investigated herein to extract wind energy. A nonlinear hybrid restoring toque mechanism, installed at equally spaced supports, is used to produce energy through limit-cycle vibration. Energy conversion and storage from the wind flow are enabled by eddy currents. The apparatus is used during thunderstorm outflows to explore the efficiency in non-ideal wind conditions. The thunderstorm flow model accounts for both non-stationary turbulence and slowly varying mean speed, replicating thunderstorm's intensification and decay stages. This paper evolves from a recent study to examine stochastic stability. More Specifically, the output power is a random process that is derived numerically. Various thunderstorm features and variable apparatus configurations are evaluated. Numerical investigations confirm the detrimental effect of non-ideal, thunderstorms on harvester performance with, on average, an adverse increment of operational speed (about +30\%). Besides nonlinear damping, the benign flutter-prone effect is controlled by the square of the flapping angle. Since flapping amplitudes are moderate at sustained flutter, activation of the apparatus is delayed and exacerbated by the non-stationary outflow and aeroelastic load features. Finally, efficiency is carefully investigated by quantification of output power and “quality factor”.

Discussion on the application of sequential turbocharging technology on trawlers

To improve the performance needs of trawlers under the varying load and speed conditions of free-running and trawling operations, this article employs sequential turbocharging technology. By fitting the experimental curves of basic turbocharging and conventional turbocharging (two turbochargers), we obtained the universal characteristic curve of sequential turbocharging. Further, the propeller characteristic curves and load characteristic curves of trawlers under free-running and trawling operations were integrated. The analysis results show that the sequential turbocharging system increases the torque of trawlers by about 20% in the low-speed range; switching to two turbochargers in free-running mode reduces fuel consumption by ∼17.5 g/Wh; switching to basic turbocharging during trawling operations decreases fuel consumption by about 13.9 g/Wh. This study is not only beneficial for the economy of ships but also provides guidance for further improvements in engine mechanics, potentially attracting the interest of readers in the main engine manufacturing field.

MTPA Control of Wound-Rotor Synchronous Start/Generator Drives Based on Virtual Signal Injection Considering Cross-Coupling Effect in Low-Speed Range

MTPA Control of Wound-Rotor Synchronous Start/Generator Drives Based on Virtual Signal Injection Considering Cross-Coupling Effect in Low-Speed Range

Sensorless Control of Surfaced-Mounted Permanent Magnet Synchronous Motor in a Wide-Speed Range

This paper delves into a comprehensive study of a wide-speed-range sensorless control approach for surface-mounted permanent magnet synchronous motors (SPMSMs). In the low-speed range, a novel high-frequency pulse voltage injection (HFPVI) method is introduced for rotor position estimation, which does not depend on motor saliency and is well-suited for SPMSMs. This method incorporates a second-order generalized integrator (SOGI) and a new modulation signal to enhance the accuracy of rotor position estimation. For medium-to-high speeds, an improved super-twisting sliding mode observer (STSMO) utilizing a continuous hyperbolic tangent function is proposed to mitigate chattering. Additionally, a new phase-locked loop (NPLL) is introduced to accurately obtain the rotor position. Furthermore, this paper designs an exponential weighted switching function to facilitate a smooth transition of the motor from the low-speed domain to the medium- and high-speed domains. The effectiveness and superiority of the proposed methods are validated through simulations and experiments conducted on an RTU-BOX platform. The rotor position estimation errors of the proposed new HFPVI method and the improved STSMO method under various operating conditions are both approximately 0.05 rad (2.8 elc·deg), and the SPMSM can switch smoothly from the low-speed range to the medium- and high-speed ranges.

A new emotional intelligent adaptive system for controlling the proposed sensor-less induction motor drive with dual stator winding based on a ten-switch converter in low speed range

A dual stator winding induction motor (DSWIM) has two isolated three-phase windings in its stator, and its rotor is a usual squirrel cage type. In a sensor-less DSWIM drive, the standard and optimal operating mode in all operating speed ranges is the synchronous mode. Until now, researchers use the asynchronous mode to control it in the low speed range that is not the standard mode. But, this paper proposes a new intelligent model reference adaptive system (IMRAS) to control a DSWIM drive without the speed sensor based on a ten-switch converter in the low speed range. In the proposed intelligent sensor-less DSWIM drive, the rotor speed is estimated via an intelligent model as single and bi-objective functions. In the proposed IMRAS, the second objective increases the speed estimation accuracy at very low speeds. In this idea, the rotor speed error is used as data in the rotor speed estimation process. As a result, the convergence between estimated speed and reference speed in the proposed IMRAS is increased at zero and very low speeds. Also, in this paper, the power losses, the capital cost, and the number of switching elements in the converter are reduced via the concept of flux compensation and using a ten-switch converter. The intelligent proposed sensor-less DSWIM drive, unlike conventional methods, works in its standard operating mode (synchronous mode) and has a suitable performance in the low speed range. Hence, the converter power losses are significantly decreased. The suggested techniques are simulated in MATLAB software. The simulation of the proposed DSWIM drive system is performed under different scenarios of operating conditions and the obtained results approve the assumptions.

Theoretical and experimental study of a bi-stable piezoelectric energy harvester under hybrid galloping and band-limited random excitations

In the practical environment, it is very common for the simultaneous occurrence of base excitation and crosswind. Scavenging the combined energy of vibration and wind with a single energy harvesting structure is fascinating. For this purpose, the effects of the wind speed and random excitation level are investigated with the stochastic averaging method (SAM) based on the energy envelope. The results of the analytical prediction are verified with the Monte-Carlo method (MCM). The numerical simulation shows that the introduction of wind can reduce the critical excitation level for triggering an inter-well jump and make a bi-stable energy harvester (BEH) realize the performance enhancement for a weak base excitation. However, as the strength of the wind increases to a particular level, the influence of the random base excitation on the dynamic responses is weakened, and the system exhibits a periodic galloping response. A comparison between a BEH and a linear energy harvester (LEH) indicates that the BEH demonstrates inferior performance for high-speed wind. Relevant experiments are conducted to investigate the validity of the theoretical prediction and numerical simulation. The experimental findings also show that strong random excitation is favorable for the BEH in the range of low wind speeds. However, as the speed of the incoming wind is up to a particular level, the disadvantage of the BEH becomes clear and evident.

Speed Estimation of Induction Motor at Low and Zero Speed using High Frequency Signal Injection for Rotor Slot Harmonics Detection

Rotor position estimation based on high frequency signal injection method represents the interesting way to provide the high performances of the AC drives sensorless controlled at low or near zero speed range. So, this method requires the existence of saliencies inside the IM particularly the presence of the slots where their design constitutes the main advantageous to exploit its effect for rotor speed monitoring. First, the present paper exposes a model of the induction machine including slotting effects which it can be exploited in order to extract the harmonic saliency created by rotor slotting. Second, the high frequency signal injection method is used in order to allow tracking the characteristic harmonic saliency due to rotor slotting from which the rotor position and speed may be estimated. A High frequency voltage signal injection creates a high frequency current modulated by the saliencies presented inside the machine. To extract information about rotor position, the resulting stator current treads to heterodyning process to eliminate the disturbance components and subsequently the rotor position may be extracted by a closed-loop observer. Simulation results are shown in order to verify the validity of the proposal and to confirm the effectiveness of estimation method at zero frequency.

УПРОЩЕННАЯ КОМПЬЮТЕРНАЯ МОДЕЛЬ ВЕТРОЭНЕРГЕТИЧЕСКОЙ СИСТЕМЫ НА ОСНОВЕ ДВУХ МАГНИТОЭЛЕКТРИЧЕСКИХ ГЕНЕРАТОРОВ С РЕКОНФИГУРИРУЕМЫМИ ОБМОТКАМИ

Relevance Due to the growing demand for electricity and the reduction in reserves of traditional energy sources, energy conservation and the use of alternative sources are becoming increasingly important. Wind energy is an important growth industry in the production of electricity from renewable wind energy, playing an important role in diversifying energy sources and reducing dependence on the unstable political and economic factors associated with the extraction and transportation of fossil fuels. Wind energy, from a scientific point of view, is a field of science and technology that develops the theoretical foundations, methods and means of using wind energy. To convert the kinetic energy of the wind flow into mechanical energy of rotation of the generator rotor with its subsequent conversion into electrical energy, wind power plants of various configurations are used, installed in open areas where the wind has a suitable speed for generating electricity. Of particular interest to researchers, engineers and the public around the world is the issue of developing new wind power plants and improving existing ones. Thus, wind energy has great interest in the modern world, representing an important and promising option for diversifying the energy system, reducing environmental pollution and providing a sustainable and economically attractive source of energy for future generations. Aim of research To study the operating modes at low and normal wind speeds of a wind power system model based on two magnetoelectric generators with reconfigurable windings in the Matlab application package (Simscape). Research methods Simulation of operating modes at low and normal wind speeds of a wind energy system based on two magnetoelectric generators with reconfigurable windings in the Matlab application package (Simscape). Results A study was carried out of the operating modes at low and normal wind speeds of a wind energy system based on two magnetoelectric generators with reconfigurable windings in the Matlab application package (Simscape). This voltage regulation method can provide the ability to stabilize voltage and maintain high efficiency at an acceptable level over a wider range of low and normal wind speeds.