Light Load Research Articles

Study on energy management strategy of fuel cell patrol vehicle hybrid power system

The slow dynamic response of fuel cells has limited the development of fuel cell vehicles to a certain extent, and reasonable energy management strategies are one of the critical issues that need to be resolved to promote the industrialization of fuel cell vehicle. Based on the complex operating conditions of fuel cell patrol vehicles, this paper establishes a model of the vehicle and the component, exploring the impact of energy management strategies on vehicle performance. The simulation results indicate that Fuzzy logic control (FLC) causes significant fluctuations in fuel cell output power under both light and heavy load conditions. Pontryagin minimum principle (PMP) and Adaptive Pontryagin minimum principle (APMP) maintain a constant lower output power near a fixed value and change slightly according to demand. Comprehensively analyzing the two operating conditions, PMP and APMP can stably maintain State of charge (SOC) around the reference value and converge toward the reference value, and the SOC of the FLC strategy is generally lower than the reference value. Under light and heavy load conditions, the average efficiency of the APMP fuel cell system reaches 50.44% and 49.58%, respectively, which is similar to the PMP strategy and is respectively improved by 0.67% and 0.32% compared to the FLC strategy.

Mechanical characterization of novel Parthenium hysterophorus and Jute reinforced polymer matrix composites for light weight medium load applications and application of MADM-VIKOR approach

This study explores the use of natural fibers in composite materials to enhance mechanical properties and reduce water absorption for lightweight medium load applications. The approach involves hybridizing Parthenium hysterophorus (PH) and Jute with epoxy L-12 matrix in different stacking sequences to create four tri-layer composites. Mechanical tests following ASTM standards revealed that composites with Jute fibers on top and PH fibers in the middle exhibit superior mechanical performance and reduced water absorption, making them suitable for such applications. The tensile strength of composite (CP4) with PH fiber at center and Jute fibers at extreme was found to be 1.7 times higher compared to composite with all three layers of PH fiber (CP1). Similarly, the flexural strength and compressive strength of CP4 is found to be 60% and 80.5% more compared to CP1. Shore D hardness of CP4 is found to be 1.29 times better compared to CP1. Whereas the energy absorption due to impact load of CP1 is better compared to its counter parts wit CP1 exhibiting 71.15 times better compared to CP4. Scanning electron microscope (SEM) analysis of fractured surfaces provides insights into fiber bonding and fracture mechanisms. Overall, this research underscores the potential of natural fiber hybrid composites for improved mechanical characteristics and water resistance in various applications, highlighting specific fiber combinations and stacking sequences.

Topology and Control Optimization of Bidirectional DC/DC Converter for Electric Vehicles

With the rapid development of intelligent electric vehicles, the number of electrical equipment increases, and the interconnection and energy transmission between on-board DC buses has become urgent. This paper proposes a partial isolated bidirectional converter based on dual active bridge converter. By partial switch sharing, the converter has a simplified structure and can supply energy to DC loads of different voltage levels. The system adopts a hybrid control strategy of pulse width modulation and triple phase shift modulation, and introduces a fundamental phase shift to reduce coupling between variables. The operation process is analyzed, and the models of transmitted power, current stress and soft-switching range under two typical operation modes, corresponding to the full load and light load, are established respectively. Under wide gain and different power distribution conditions, the multi-objective optimization is realized. Finally, the correctness of theoretical analysis is verified by experiments.

PMSM Field-Oriented Control with Independent Speed and Flux Controllers for Continuous Operation under Open-Circuit Fault at Light Load Conditions

Presented in this article is a permanent magnet synchronous motor (PMSM) control under open-circuit fault (OCF) operation using field-oriented control (FOC) with independent speed and flux controllers. The independent control allows the motor to operate efficiently under varying conditions. A simplified control approach is employed to control the PMSM under the OCF situation; the actual flux and torque of the PMSM are directly measured by the stator currents, eliminating the need for estimators or phase-locked-loop (PLL) systems. Matlab/Simulink is employed for the simulation, while hardware experiments are conducted using a dSPACE DS1104. The simulation and the hardware results demonstrate the control method’s effectiveness in maintaining continuous motor operation during OCF, its robustness against OCF conditions, and its ability to adapt under varying conditions, including speed, flux, and load torque change.

The highs and lows of lifting loads: SPM analysis of multi-segmental spine angles in healthy adults during manual handling with increased load

Introduction: Manual handling personnel and those performing manual handling tasks in non-traditional manual handling industries continue to suffer debilitating and costly workplace injuries. Smart assistive devices are one solution to reducing musculoskeletal back injuries. Devices that provide targeted assistance need to be able to predict when and where to provide augmentation via predictive algorithms trained on functional datasets. The aim of this study was to describe how an increase in load impacts spine kinematics during a ground-to-platform manual handling task. Methods: Twenty-nine participants performed ground-to-platform lifts for six standardised loading conditions (50%, 60%, 70%, 80%, 90%, and 100% of maximum lift capacity). Six thoracic and lumbar spine segments were measured using inertial measurement units that were processed using an attitude-heading-reference filter and normalised to the duration of the lift. The lift was divided into four phases weight-acceptance, standing, lift-to-height and place-on-platform. Statistical significance of sagittal angles from the six spine segments were identified through statistical parametric mapping one-way analysis of variance with repeated measures and post hoc paired t-tests.Results: Two regions of interest were identified during a period of peak flexion and a period of peak extension. There was a significant increase in spine range of motion and peak extension angle for all spine segments when the load conditions were increased (p < 0.001). There was a decrease in spine angles (more flexion) during the weight acceptance to standing phase at the upper thoracic to upper lumbar spine segments for some condition comparisons. A significant increase in spine angles (more extension) during the place-on-platform phase was seen in all spine segments when comparing heavy loads (>80% maximum lift capacity, inclusive) to light loads (<80% maximum lift capacity) (p < 0.001).Discussion: The 50%–70% maximum lift capacity conditions being significantly different from heavier load conditions is representative that the kinematics of a lift do change consistently when a participant’s load is increased. The understanding of how changes in loading are reflected in spine angles could inform the design of targeted assistance devices that can predict where and when in a task assistance may be needed, possibly reducing instances of back injuries in manual handling personnel.

Design and Development of a Screw Jack: An Input Repair Tool for Light Vehicles

This study introduces an innovative investigation into the development and utilization of a specially designed jack screw tailored for lifting lightweight objects. While screw jacks are well-established for their efficacy in mechanical lifting applications, this research aims to broaden their adaptability by specifically addressing the unique demands of lifting lighter loads. The exploration encompasses a thorough examination of the design principles, materials, and operational facets associated with the proposed screw jack innovation. The primary impetus behind this research is to fill an existing void in lifting solutions that are customized to the requirements of tasks involving light objects. By delving into the intricacies of screw jack design, the study seeks to improve the efficiency and safety of lifting operations in diverse contexts, such as small-scale workshops, where precision and controlled lifting of lighter loads are crucial. Anticipated outcomes of this study include the development of a specialized screw jack prototype that provides a dependable, cost-effective, and ergonomic solution for lifting light objects. The research findings aim to contribute valuable insights to the fields of mechanical engineering and lifting technology, laying the groundwork for further advancements in the design and application of lifting devices tailored to specific load requirements. Based on the study's findings, the following conclusions were drawn: the device effectively raises objects with a 2-ton capacity, its safety has been successfully verified, and the materials used are locally available. However, it is essential to note that this design is limited to light loads. Therefore, in applications requiring a screw-type mechanical jack for heavy loads, a different design is necessary. Recommendations include adherence to the device's capacity, implementation of safety measures to prevent accidents during operation, and potential modifications for further enhancement in future research endeavors.

A Deep Learning-Based Microgrid Energy Management Method Under the Internet of Things Architecture

Given that the current microgrid incorporates highly connected distributed energy sources, the conventional model control methods do not suffice to support complex and ever-changing operating scenarios. This paper proposes a deep learning-based energy optimization method for microgrid energy management in the new power system scenarios. This article constructs a microgrid cloud edge collaboration architecture, which collects interactive network status data through terminal devices and network edge sides. A microgrid energy management model is constructed based on Bi-LSTM attention in the network cloud. And the model is sunk to provide real-time and efficient comprehensive load and power generation prediction output optimal scheduling decisions at the edge of the network, achieving collaborative control of microgrid light load storage. The simulation based on the actual available microgrid data shows that the proposed Bi-LSTM attention energy management model can achieve rapid analysis and optimize decision-making within 7.3 seconds for complex microgrid operation scenarios.

A novel robustness matching method based on amplitude-frequency characteristic for high power ultrasonic system under variable load

In order to solve the insufficiency of the driving capacity when the load of the ultrasonic driver changes, a high robustness LC matching design method is proposed based on the equivalent circuit modeling and the amplitude-frequency characteristic analysis of circuit transfer function. The transfer function of the input current including the matching capacitance and inductance is established by using the amplitude-frequency characteristics of the circuit transfer function. In order to simplify the transfer function, two new parameters as: impedance coefficient kz and frequency coefficient kf is introduced and a robust matching method based on uncertainty solving is proposed. The superiority of the proposed method compared with the existing matching method is proved by simulation and experiment. The experimental results show that the current fluctuation is less than 10% from light load to full load, which proves the reliability and robustness of our proposed method is higher than the existing matching method. It can ensure the amplitude stability of the ultrasonic transducer, and its performance is optimal than the existing general matching method.

Fuzzy adaptive control of coal gangue sorting parallel robot with variable load

ABSTRACT Delta parallel robot is widely used in the high-speed sorting industry with a light load and constant load. Its motion control is based on kinematic planning, without considering the influence of load and disturbance. The gangue sorting robot has the characteristics of a large load and random mass change, so traditional kinematics planning can not meet the control requirements. A fuzzy adaptive robust control algorithm is proposed to solve the problems of unstable motion and jitter in the coal gangue sorting robot. By establishing the mathematical model of the fuzzy system, the uncertain terms of the dynamic parameters caused by the random changes in the load are approximated. At the same time, to reduce the number of fuzzy rules and the amount of fuzzy calculation, the uncertain terms are decomposed into velocity terms and acceleration terms and then approximated, respectively. The Lyapunov analysis of the system is carried out, and the convergence of the system is proved. The simulation results show that the fuzzy adaptive robust control algorithm has a smaller error and faster convergence compared with the computational torque control algorithm when the system is sorting gangue within 8 kg, which improves the stability of gangue grasping.

Kinematic calibration and feedforward control of a heavy-load manipulator using parameters optimization by an ant colony algorithm

AbstractMost of the currently available three-degree-of-freedom manipulators are light load and cannot achieve full continuous rotation; given this, we designed a heavy-load manipulator that achieves unrestricted and continuous rotation. Due to manufacturing and assembly errors, parameter deviations between the real manipulator and its underlying theoretical model were unavoidable. Because of the lack of high-precision, high-frequency, and real-time closed-loop detection methods, we proposed a type of kinematics calibration of parameterized ant colony optimization and feedforward control methods. This was done to achieve high-precision motion control. First, an error model combining structural parameters and joint output angles was established, and the global sensitivity of each error source was analyzed to distinguish both primary and secondary sources. Based on the measured data of a laser tracker, the ant colony optimization was then used to identify six error sources. This resulted in both link length and joint driving errors of the designed manipulator. As it is a type of systematic error, the rounding error of the theoretical trajectory was carefully analyzed, and feedforward control methods with different coefficients were designed to further improve positioning accuracy based on the kinematic calibration. Experimental results showed that the proposed kinematic calibration and feedforward control methods achieved relatively precise motion control for the designed manipulator.

Comparative analysis of angular contact bearing stiffness calculated by Hertz contact and thermo-elastohydrodynamic lubrication

Stiffness is the key dynamic parameter of the angular contact ball bearing. This work established a dynamic bearing model based on Hertz theory and thermo-elastohydrodynamic lubrication (TEHL) and compared the contact angle, inner race position, and stiffness. In most cases, the stiffness calculated via Hertz was higher than when using TEHL. The axial stiffness values determined via the two theories were close, while the radial stiffness calculated via the Hertz theory was smaller than that determined by TEHL under light load and high speed. Considering the elastic deformation of the races and the initial contact angle, the results obtained by TEHL displayed a lower error rate in the experiment than Hertz.

Effects of light- vs. heavy-load squat training on velocity, strength, power, and total mechanical work in recreationally trained men and women.

The purpose of this study was to investigate the effects of light and heavy loads in the squat exercise on kinematics and mechanical variables in recreationally trained men and women. Twenty-two men and sixteen women were assigned to 4 groups: 40% and 80% one-repetition maximum (1RM) male (M40 and M80) and female (F40 and F80). Over 6 weeks, participants performed twice a week the full back-squat (SQ) exercise with initially equated relative volume load (Sets*Repetitions/Set*%1RM). All groups performed different amounts of work (p < 0.05), while relative work (work/1RM) only differed between load groups (p < 0.001). There was no significant Time*Sex*Load interaction. Based on the magnitude of effect sizes: M80 achieved small improvements in the SQ maximum isometric force (MIF; ES = 0.43, 95% CI [0.16, 0.81]); small gains in squat estimated 1RM strength were observed in the 80%-1RM groups (M80: 0.42 [0.18, 0.77]; F80: 0.44 [0.26, 0.76]) and the F40 group (0.42 [0.17, 0.81]); all groups made moderate to large gains in the average velocity attained against heavy loads (> 60%1RM; F40: 1.20 [0.52, 2.27]; F80: 2.20 [1.23, 3.93]; M40: 0.85 [0.29, 1.59]; M80: 1.03 [0.55, 1.77]), as well as small to moderate improvements in the average velocity against light loads (< 60%1RM; F40: 0.49[-0.24, 1.68]; F80: 1.10 [0.06, 3.16]; M40: 0.80 [0.41, 1.35]; M80: 0.93 [0.25, 1.84]). Lastly, only the F40 group showed small improvements in countermovement jump (CMJ) height (ES = 0.65 [0.14, 1.37]). In conclusion, light and heavy loads produced similar strength gains in men and women when initially equated by relative volume load, although the standardized mean differences suggest nuances depending on the sample and task.

Experimental Investigation of Concrete‐Infilled Bamboo for Structural Performance in Compression for Low‐Cost Building

The study explored an innovative scheme to improve the load‐bearing capacity of bamboo by infilling it with concrete to form a composite column as a compression member for low‐cost buildings. A total of four samples of bamboo of five different lengths (0.2, 0.4, 0.6, 0.8, and 1 m) were prepared with concrete (concrete infilled) and without concrete for three different commonly used concrete grades (C12/15, C15/20, and C20/25) and the load‐carrying capacity tested to determine its resistance under compression. Generally, there was a considerable improvement in structural performance in terms of load‐carrying capacity when the bamboo culms were infilled with plain concrete. The failure load capacity of plain bamboo (no concrete infill) was reduced by 26.4% with an increase in the length of the bamboo from 0.2 to 1 m. Concrete‐infilled bamboo with C15, C20, and C25 led to an increment of 58.7%, 103%, and 139.1% of the failure load capacity relative to that of the plane bamboo culms sample test length at 1 m, respectively. Bamboo infilled with concrete grade C25 had a larger failure load as compared to those infilled with concrete grade C20 and C15. The study concludes that concrete in‐filled bamboo increases the buckling resistance as well as the load‐carrying capacity and it can be an alternative composite building material to steel and concrete for building under light loads.

The Investigation of Dimensional, Form and Orientation Accuracy of Polymer Gears Prepared by Additive Manufacturing

Among the additive manufacturing techniques Fused Deposition Modeling (FDM) is a widely used process, due to its rapid development in the recent years, and its consequent drop in price. 3D printing has multiple process parameters, which affect the dimensional, form, and orientation accuracy, and thus the usability of the final product. In this work the effects of layer thickness, printing speed, and infill on the dimensional and geometric deviations were studied with a 3 factor Box-Behnken experimental design. The measured deviations were within the tolerance range specified by the standards. Based on this, it can be stated that 3D printing is a promising gear manufacturing technology for light and medium load applications.

Objective Evaluation of Local Muscle Fatigue in Cerebral Palsy Using A Gait Corrector

The participants were seven individuals (age range 7–36 years) whose walking ability ranged from independent to requiring assistance with a cane, walker, etc. The protocol consisted of resting for at least five minutes before starting to walk, wearing a Gait Corrector device, and walking with light and heavy loads based on the participant's rating of perceived exertion (RPE), followed by resting for 10 minutes before the end of the protocol.Near-infrared spectroscopy (NIRS) electrodes were attached bilaterally to the tibialis anterior and lateral gastrocnemius muscles. NIRS was used to measure blood oxygenation dynamics in local muscles from rest before walking to 10 minutes after walking, and evoked electromyography was used to measure the nerve conduction velocity of the peripheral nerves before and during early and late walking.The tone state of the lateral gastrocnemius muscle was measured three times using an evoked potential-testing device: before walking, immediately after heavy-load walking, and 10 minutes after walking. A recording electrode was attached to the abductor digitorum medialis muscle and a reference electrode was attached to the base of the toe. The M and F waves were recorded using tibial nerve stimulation. The average F/M ratio was used as a parameter of the F-wave.Regarding the change in muscle tone, four of the seven patients exhibited no change or a lower mean F/M ratio after walking than before walking, whereas three patients who exhibited resistance to other dorsiflexion movements of the ankle joint had higher values. Blood oxygenation dynamics revealed a greater disparity between oxyhemoglobin and deoxyhemoglobin concentrations after walking in all participants, suggesting local muscle fatigue, the degree of which showed no improvement even after 10 minutes of rest.

Electrophysiology of Ctenophore Smooth Muscle.

Unlike in the Cnidaria, where muscle cells are coupled together into an epithelium, ctenophore muscles aresingle, elongated,intramesogleal structuresresembling vertebrate smooth muscle. Under voltage-clamp, these fibers can be separated into different classes with different sets of membrane ion channels. The ion channel makeup is related to the muscle's anatomical position and specific function. For example, Beroe ovata radial fibers, which are responsible for maintaining the rigidity of the body wall, generate sequences of brief action potentialswhereas longitudinal fibers, which are concerned with mouth opening and body flexions, often produce single longer duration action potentials.Beroe muscle contractions depend on the influx of Ca2+. During an action potential theinward current is carried by Ca2+, and the increase in intracellular Ca2+ concentrationgenerated can be monitored in FLUO-3-loaded cells. Confocal microscopy in line scan mode shows that the Ca2+ spreads from the outer membrane into the core of the fiber and is cleared from there relatively slowly. The rise in intracellular Ca2+ is linked to an increase in a Ca2+-activated K+ conductance (KCa), which can also be elicited by iontophoretic Ca2+ injection. Near the cell membrane, Ca2+ clearance monitored using FLUO3, matches the decline in the KCa conductance. For light loads, Ca2+ is cleared rapidly, but this fast system isinsufficient when Ca2+ influx is maintained. Action potential frequency may be regulated by the slowly developing KCa conductance.

A Novel Control Scheme for Light Load Power Reduction of Flyback Converter

A Novel Control Scheme for Light Load Power Reduction of Flyback Converter

High green index electromagnetic interference shields with semiconducting Bi2S3 fillers in a PEDOT:PSS matrix.

Conventional metallic electromagnetic interference (EMI) shields, as well as the emerging 2D material-based shields, meet the shielding effectiveness (SE) needs of most applications. However, their shielding performance is dominated by the reflection of incoming radiation due to their high electrical conductivity, which leads to secondary pollution. This problem is getting exacerbated with the proliferation of electronics and communication networks in modern society. Thus, EMI shields that function dominantly by the absorption of incoming radiation are highly desirable. Such shields would be characterized by a green index, which is the ratio of absorbance over reflectance, close to or greater than one. For nonmagnetic materials, the best way to reduce the undesirable large impedance mismatch is to reduce the effective permittivity of the shield material. Here, we present a new EMI shield with a semiconductor Bi2S3 filler in a conducting PEDOT:PSS polymer matrix, instead of the conventional conductive fillers, to reduce the effective permittivity and demonstrate that even a light loading of only 10% Bi2S3 provides high SE of over 40 dB with a green index value of 0.75. Increasing the filler content to 15 wt% increases the green index close to unity while dropping the SE to 30 dB. The shielding mechanism is explained through electromagnetic parameter measurements and supplemented by density functional theory calculations. This work lays the foundation for the advancement of lightweight and ultrathin green EMI shields with minimum secondary pollution.

A Hierarchical Driving Control Strategy Applied to Parallel SiC MOSFETs

SiC (silicon carbide) MOSFETs have been extensively used in the power electronics industry due to their exceptional characteristics. First, it was found in this study that their driving loss is larger than their conduction loss in high-frequency applications. Based on this finding, this study proposes a hierarchical driving control strategy for improving the parallel-converter efficiency of SiC MOSFETs under light loads. Efficiency under light loads is of great importance for battery-based energy storage systems. To minimize the sum of the conduction loss and driving loss in parallel devices, this study proposes a current-monitoring hierarchical driving strategy based on an active-clamped flyback converter. By monitoring the output current of the converter, the strategy minimizes the sum of the driving and conduction losses by switching the driving state under different loads. The results of simulations indicate the effectiveness of the load-current-monitoring strategy. To verify the effectiveness of this method, a principle prototype of two SiC MOSFETs connected in parallel at 12 V/5 A was fabricated and tested, and the test results showed that there was a maximum improvement of 1.4% in the converter’s efficiency when the load current was in the range of 0.5–1.5 A.

Effects of low-load blood flow restriction on the venous system in comparison to traditional low-load and high-load exercises.

Purpose: Blood-Flow-Restriction (BFR) training provides the ability to achieve hypertrophy effects even though only light mechanical loads are applied. However, its impact on venous pressures and function are still unknown. Therefore, the present study investigates the influence of BFR-training on intravascular venous pressure and venous function in comparison to control exercises with low or high mechanical loads. Methods: In a randomized cross-over design, ten healthy men (27.6 ± 6.4 years) underwent three trials of unilateral knee-extensor exercise with three different training protocols, low-load- (LL-RT, 30% of the individual 1-repetition-maximum, 1RM), low-load BFR- (LL-BFR-RT, 30% 1RM, 50% limb occlusion pressure, LOP) and high-load resistance exercise (HL-RT, 75% 1RM). Exercise protocols contain about four sets of knee extension exercise (Range-of-Motion: 0-0-95°), separated by 60s of rest. Each set was performed until volitional muscle failure. For analysis of changes in intravascular venous pressures and venous function, a venous catheter was placed at the exercising leg before each trial. Whereas venous pressures were recorded throughout the exercise trials, phlebodynamometric investigations were performed before and after each trial. Furthermore, subjective pain perception during and after exercise was accessed by visual analogue scale. One-way ANOVA was used to assess mean differences between training protocols, while two-way repeated-measures ANOVA (rANOVA; time x condition) was performed to compare changes in measures over time among conditions. Data were given as means ± standard deviation (SD). Results: In comparison to the exercise trials without venous occlusion, total workload was significantly lower in the LL-BFR-RT (LL-RT: 1745 ± 604kg vs LL-BFR-RT: 1274 ± 237kg vs HL-RT: 1847 ± 367kg, p = 0.004) without indicating statistical differences in venous pressures during the exercise sets (interaction: p = 0.140) or pain perception (interaction: p = 0.574). Similarly, phlebodynamometric assessment of venous function (e.g. refill-time of the venous system pre-vs. post exercise trials-LL-RT: 29.7 ± 11.0s vs 25.5 ± 9.6s, LL-BFR-RT: 26.6 ± 13.0s vs 27.3 ± 13.8s, HL-RT: 25.9 ± 10.9s vs 23.1 ± 8.2s) revealed no time (p = 0.156), condition effect (p = 0.802) or their interactions (p = 0.382). Conclusion: The present study is the first one describing the acute effects of LL-BFR-RT to muscle failure on venous pressures and function in comparison to a LL- and HL-RT in the lower limbs. In contrast to the existing literature, LL-BFR-RT does not elevate the venous pressures during exercise higher than a comparative exercise without BFR and does not show any adverse effects on venous function after the exercise.