Quarter Model Research Articles

A fuzzy skyhook control strategy optimized by particle swarm strategy for magnetorheological semi-active suspension

In order to solve the problem of unsatisfactory control effect caused by uncertain parameters in the fuzzy skyhook control method, a fuzzy skyhook control strategy optimized by particle swarm strategy is proposed. The magnetorheological (MR) damper is put on the bench for mechanical characteristics experiment, and the forward model of MR damper is established. The adaptive network fuzzy inference system (ANFIS) system in simulation software is used to build its inverse model to verify the accuracy of the forward model of MR damper. A quarter vehicle suspension model is established, and a fuzzy skyhook control strategy based on particle swarm optimization is designed. Numerical simulations are carried out under the excitation of random road. The acceleration, suspension dynamic deflection and tire dynamic load are used to evaluate its performance. Compared with the passive control, the root mean square (RMS) values of the acceleration for the fuzzy skyhook control strategy are improved by 41.9% and 37.6%, the RMS values of the suspension dynamic deflection for the fuzzy skyhook control strategy are improved by 53.3% and 48.0%, and the RMS values of the tire dynamic load for the fuzzy skyhook control strategy are improved by 17.6% and 14.5% under the B-Class and C-Class road excitations. The simulations and experimental results verify the effectiveness of the controller.

Stability and Control of Car Dynamics with a Quarter Model via a Novel Simple Harmonic Hump under External Force

Effects of the road, such as speed bumps, can significantly affect a car’s stability. This study focuses on how a quarter-car model is affected by a basic harmonic speed hump and how Cubic Negative Velocity Control (CNVC) is used to control the amplitude of disturbances. This study differs from earlier research in considering various control and force kinds that impact the system. The external forces in this context are a component of a non-linear dynamic system. Two-degree-of-freedom (2DOF) differential coupled equations describe the system’s equation. Numerous numerical experiments have been conducted, including proportional derivative (PD), negative derivative feedback (NDF), positive position feedback (PPF), linear negative velocity control (LNVC), and CNVC; the results show that when the hump is represented as a simple harmonic hump, CNVC has the best effect and can regulate vibrations more precisely than the other approaches on this system. Subsequently, the vibration value of the system was numerically analyzed both before and after the control was implemented. Using the frequency response equation and phase plane approaches in conjunction with the Runge–Kutta fourth order method (RK-4) in the context of resonance situation analysis, the stability of the numerical solution has been evaluated.

A novel strengthened road roughness estimation framework based on the adaptive unbiased minimum variance with unknown input

The accurate acquisition of the strengthened road roughness is significant to vehicle reliability and durability. However, the existing road roughness estimation methods are inapplicable due to the non-Gaussian characteristic of the strengthened road roughness. To fulfil this gap, this work proposes a novel strengthened road roughness estimation framework based on the adaptive unbiased minimum variance with unknown input (AUMV-UI) to accurately estimate the roughness of strengthened roads. The proposed AUMV-UI framework consists of four sub-models, i.e. the quarter suspension model, the vehicle parameter identification model, the road roughness estimation model, and the estimation error correction model. In the road roughness estimation model, the unbiased minimum variance with unknown input (UMV-UI) method is proposed for the first to estimate the strengthened road roughness, and thus the first three sub-models are also integrated as the UMV-UI framework. In the estimation error correction model, the Sage–Husa method is introduced to further correct the potential errors of the UMV-UI method. The AUMV-UI framework is validated and compared to the UMV-UI framework by simulations and experiments. The results show that the AUMV-UI framework can significantly improve the estimation accuracy, which can serve as an elegant tool to accurately acquire the strengthened road roughness.

A new hybrid control strategy for improving ride comfort on lateral suspension system of railway vehicle

The ride comfort is a key research area for the quality improvement of railway vehicles. Several control methods have been developed to improve the ride comfort, in which the semi-active control approach inherits the advantages of passive and active control approaches. However, the semi-active control may perform ineffectively in vibration attenuation when the carbody load changes. To address this issue, we proposed a novel hybrid control method that combines the skyhook (SH) and displacement velocity (DV) control methods to reduce vibrations of the carbody in the lateral direction under carbody load changes. First, a hybrid control model built in Matlab software was applied to a quarter railway vehicle model for a preliminary assessment of the ride comfort. Second, to provide a more comprehensive evaluation, the proposed model was applied to a whole railway vehicle model using co-simulation (Matlab-Simpack). In the quarter model, under the sinusoidal excitation, the hybrid control showed a lower acceleration by 48.5% and 42.8% when the carbody load reduced to a half and a quarter, respectively, compared to the passive control. This finding was confirmed with the whole model. Moreover, in the whole model, under the track irregular excitation, the hybrid control showed a lower acceleration by 26.6% and 17.4% when the carbody load reduced to a half and a quarter, respectively. Further, the proposed method showed an acceptable safety level, measured by the derailment coefficient (0.0743 at a half load and 0.089 at a quarter load). In conclusions, the proposed hybrid SH-DV control exhibits high robustness, adaptability, effectiveness, and acceptable safety level in response to variations in body load.

Assessment approaches in undergraduate health professions education: towards the development of feasible assessment approaches for low-resource settings

BackgroundFeasible and effective assessment approaches to measuring competency in health sciences are vital in competency-based education. Educational programmes for health professions in low- and middle-income countries are increasingly adopting competency-based education as a strategy for training health professionals. Importantly, the organisation of assessments and assessment approaches must align with the available resources and still result in the fidelity of implementation. A review of existing assessment approaches, frameworks, models, and methods is essential for the development of feasible and effective assessment approaches in low-resource settings.MethodsPublished literature was sourced from 13 electronic databases. The inclusion criteria were literature published in English between 2000 and 2022 about assessment approaches to measuring competency in health science professions. Specific data relating to the aims of each study, its location, population, research design, assessment approaches (including the outcome of implementing such approaches), frameworks, models, and methods were extracted from the included literature. The data were analysed through a multi-step process that integrated quantitative and qualitative approaches.ResultsMany articles were from the United States and Australia and reported on the development of assessment models. Most of the articles included undergraduate medical or nursing students. A variety of models, theories, and frameworks were reported and included the Ideal model, Predictive Learning Assessment model, Amalgamated Student Assessment in Practice (ASAP) model, Leadership Outcome Assessment (LOA) model, Reporter-Interpreter-Manager-Educator (RIME) framework, the Quarter model, and the model which incorporates four assessment methods which are Triple Jump Test, Essay incorporating critical thinking questions, Multistation Integrated Practical Examination, and Multiple Choice Questions (TEMM) model. Additional models and frameworks that were used include the Entrustable Professional Activities framework, the System of Assessment framework, the Reporter-Interpreter-Manager-Educator (RIME) framework, the Clinical Reasoning framework (which is embedded in the Amalgamated Student Assessment in Practice (ASAP) model), Earl’s Model of Learning, an assessment framework based on the Bayer–Fetzer Kalamazoo Consensus Statement, Bloom's taxonomy, the Canadian Medical Education Directions for Specialists (CanMEDS) Framework, the Accreditation Council for Graduate Medical Education (ACGME) framework, the Dreyfus Developmental Framework, and Miller's Pyramid.ConclusionAn analysis of the assessment approaches, frameworks, models, and methods applied in health professions education lays the foundation for the development of feasible and effective assessment approaches in low-resource settings that integrate competency-based education.Trial registrationThis study did not involve any clinical intervention. Therefore, trial registration was not required.

Energy transfer efficiency and rock damage characteristics of a hydraulic impact hammer with different tool shapes

The energy transfer efficiency and damage characteristics are the theoretical basis for the selection and optimization of hydraulic impact hammer tools. In this paper, quarter three-dimensional models of the piston-tool-rock system are established based on the continuum and discontinuum element method. The incident and reflected stress waves and rock damage characteristics obtained from the simulation model are in good agreement with experimental and theoretical results. The effects of piston impact velocity, tool shape, rock strength, confining pressure and repeated impacts on rock damage zone and energy transfer efficiency between tool and rock are analyzed. The force-penetration curves and penetration coefficients under different impact velocities, rock strength, and confining pressure conditions are obtained. The results illustrate that the energy transfer efficiency and penetration coefficient increase with the increase of rock strength, confining pressure and tip area of tool, but decrease with the increase of impact velocity. Based on the simulation results, a prediction formula for penetration force with consideration of the shape of the tool tip is proposed and the calculation accuracy is verified. Finally, the proportion of energy actually used for rock fracturing is analyzed.

PI-PD Controller Design Based on Weighted Geometric Center Method for Time Delay Active Suspension Systems

In this study, a PI-PD controller was designed via weighted geometric center method (WGC) for a quarter vehicle model to suppress the vertical vibrations. The proposed design is based on finding the weighted geometric center of the area formed by the control parameters that make the system stable. The WGC method has two main stages. First, an area formed by the parameters of the PD controller (kf, kd) in the inner loop is obtained and the weighted geometric center of this area is calculated. Then, using these obtained parameters, the inner loop is reduced to a single block, and the parameters of the PI controller in the external loop (kp, ki) are calculated using the stability boundary curve as in the first step, and the weighted geometric center is calculated. The simulation results show that the PI-PD controller designed with the weighted geometric center method offers successful responses for the time delay quarter vehicle system.

Design, fabrication and dynamic performance analysis of Magneto-Rheological damper suitable for vehicle application

In the present scenario, automobile sector has witnessed ample amount research and development to provide a greater comfort zone to the passenger. The term ‘comfort’ includes not only economical meaning but also a pleasant feeling through the journey by mitigating road disturbances reaching the passenger. In the present work, an effort has been dedicated to design, fabricate and characterize a magneto-rheological (MR) damper suitable for automobile application. MR damper is filled with magneto-rheological fluid the attribute of which can be quickly deviated with variation in externally applied magnetic field. Damper characterization has been performed for different amplitudes, frequencies and currents. These rheological results have been used to mathematically model the damper characteristics. Later, using the mathematical model, an attempt has been made to analyze the dynamic mannerism of the MR damper in a quarter car simulation model. For the given road input, the suspension system with MR damper has shown its ability in suppressing the road disturbance in a greater manner.

Analysis of the dynamic characteristics of the gear-shifting process under external excitation

This study focuses on a novel clutchless and synchronizer-free drive system designed explicitly for pure electric vehicles. In contrast to the majority of previous research that solely considers internal excitations, this study not only incorporates various non-linear factors such as time-varying friction forces, time-varying mesh stiffness, and damping associated with internal excitations but also places significant emphasis on analyzing the impact of non-linear external excitations, including road surface unevenness and motor torque fluctuations, on the shifting process of the drive system. Subsequently, a non-linear dynamic model of the shifting process is established. In the modeling process, departing from the traditional two-degree-of-freedom quarter vehicle dynamics model, this study adopts an elastic tire-body and elastic tire-tread tire model, enabling the establishment of a highly accurate multi-degree-of-freedom quarter vehicle dynamics model. The simulation results indicate that road surface roughness and motor torque fluctuation significantly impact the gear-shifting process and the impact of road surface roughness increases with the level of roughness. Moreover, the effect of motor torque fluctuation on the gear-shifting process varies depending on different factors and is not simply additive. Consequently, when formulating and optimizing shifting strategies, it becomes imperative to consider various external factors. The research methodology integrates these factors into the dynamic analysis of the shifting process, providing a theoretical basis for developing effective shifting control strategies while considering external excitations.

Improving the blast resistance of sandwich structures by tailoring honeycomb core through varying cell size and vertex-derivative approach

Honeycomb sandwich panels (HSPs) with efficient core design have the potential to enhance blast resistance to tackle increasing blast threats by terrorist attacks. In this work, an innovative vertex-derived approach is introduced to enhance the blast resistance of HSPs. First, a quarter model of regular quadrilateral core HSP structures (RQH) with a cell size of 30.5 mm (10 × 10) was simulated with various amounts of TNT charges(1,2,&3 kg) kept at a height of 100 mm using the CONWEP algorithm available in ABAQUS/Explicit. The results obtained through simulation were validated with the tested results available in the literature. The study was extended by varying the cell sizes of 61 mm (5 × 5), 15.25 mm (20 × 20), and 7.625 mm (40 × 40) for comparison purposes. Further, honeycomb cores were tailored with the vertex-derived approach to enhance the blast resistance characteristics of RQH structures. The explosion resistance was assessed in terms of the deformation of the face sheets and dissipated energy through plastic deformation (PDE) of the face sheets and core. The result proved that the cell size variation and vertex-derived hierarchical core improved the blast resistance and the energy dissipation capacity of the RQH. The obtained results demonstrated that RQH with a 15.25 mm cell size (20 × 20) was found to have a good blast resistance at low and high-intensity blasts compared to other core sizes. The results also proved that the vertex-derived hierarchical topology enhanced the blast resistance of RQH under the same geometric parameters. The results demonstrate that employing vertex-derived hierarchical topology can enhance the blast resistance of HSPs.

MPM vs. CEL: Numerical modelling of penetration processes

MPM vs. CEL: Numerical modelling of penetration processes

Performance analysis and control of an agricultural tractor suspension system

Suspension systems play a vital role in providing comfortable and safe vehicle ride. This paper aims to improve the passenger ride comfort, vehicle stability, safety, road holding in an active quarter tractor model. the main objective is to obtain a stable, robust, and controlled system. It is necessary to use controller to increase the stability and performance of the system. the controller selection and design aimed to achieve good passenger ride comfort and health, stability, and passenger body acceleration and displacement response under uneven road excitations. PID and LQR controllers are developed, and compare their performances against the road disturbances. The performance of the designed controllers evaluated using simulation work in MATLAB. Simulation results show that the proposed LQR control scheme can successfully achieve the desired ride comfort and passenger safety compared to PID control scheme

Development of deep convolutional neural network for prediction of cycle maximum pin power peaking factor in pressurized water reactor

A deep convolutional neural network (DCNN) model based on the SE-ResNet architecture and AlphaGo’s policy architecture is developed to predict the cycle maximum pin power peaking factor (PPPF) for a pressurized water reactor core. The DCNN model is structuralized to predict an output, the PPPF, corresponding to a unique input set by removing the pooling layer in between the blocks and introducing a padding for a quarter core input model. The developed DCNN model is trained on 17,000 randomly generated loading patterns (LPs) of an OPR1000 core and tested on 2,000 LPs. The accuracy of the newly developed model for the cycle maximum PPPF prediction is on average 6.5 times higher against a fully connected neural network model having the equivalent number of trainable weights.

Two‐plane waveguide coupler with arbitrary coupling ratios in the H‐plane and E‐plane directions

AbstractA comprehensive theoretical analysis of two‐plane waveguide coupler with arbitrary coupling ratios in the H‐plane and E‐plane directions is provided and a design of the two‐plane coupler with coupling ratio in the H‐plane direction and coupling ratio in the E‐plane direction is reported. The analysis of the two‐plane waveguide coupler is fully refined and accomplished by the authors. To realise an arbitrary and different coupling ratio in the two directions, it is crucial to specifically constrain the transition phase of the quarter model of the two‐plane coupler for different boundaries as necessitated by mode polarity. A prototype of the proposed two‐plane coupler is manufactured and measured to verify the concept. Its performance is observed from 27.0 to 29.5 GHz (8.85% fractional bandwidth). The measurement results are basically in accord with the simulation results, demonstrating the reliability of the theoretical analysis. Finally, samples of designed conventional H‐plane and E‐plane couplers are provided, cascading of which can realise the same functionality as the proposed two‐plane coupler. Compared with one‐plane couplers, the two‐plane coupler reported realises overall miniaturisation rates in terms of length and volume around 58.4% and 50.1%, respectively. According to the demonstration and verification of the two‐plane couplers having arbitrary coupling ratios, the employment of the two‐plane couplers to replace the conventional one‐plane couplers to realise miniaturisation of 2‐D beam switching matrices will be promoted in future applications.

Study of magnetic, elastic and Ka-band absorption properties of Zn1−xCoxFe2O4 (0.00 ≤ x ≤ 1.00) spinel ferrites

Magnetic, elastic, electromagnetic, and microwave absorption properties of cobalt-substituted zinc spinel ferrites Zn1-xCoxFe2O4 (0.00 ≤ x ≤ 1.00, Δx = 0.25) fabricated via the sol–gel citrate route are analyzed. The hysteresis loops of constituent ferrites revealed the rapid rise in saturation magnetization and coercivity with the doping of cobalt ions. The FT-IR spectra exhibit two vibrational bands in the scope of 521–560 cm−1 and 397–404 cm−1. Complex permittivity (ɛr) and complex permeability (µr) are analyzed using a vector network analyzer in Ka-band. The absorption is maximized by tuning the thickness of the sample from 0.8 mm to 3.5 mm using the quarter wavelength model. Maximum absorption of 99.14 % at a matching frequency of 34.60 GHz and a matching thickness of 1 mm is obtained by the composition with × = 0.75. The prepared ferrite composition proves to be an efficient microwave-absorbing material at high frequencies ranging from 26.5 to 40 GHz.

Comfort-Oriented Semi-Active Suspension Configuration with Inerter-Based Network Synthesis

This paper presents a comfort-oriented semi-active suspension system composed of a network-synthesized passive section and a controllable section based on a semi-active inerter. Firstly, the semi-active suspension system is divided into a passive part and a controllable part. For the passive part, first-order and second-order robust positive real controllers are designed. The problem with H2 cost is considered, and the bilinear matrix inequalities (BMI) are solved using an iterative method to obtain two admittance functions. The admittance functions are physically realized as two mechanical networks composed of mechanical passive elements such as inerter, spring, and damper (ISD). Then, the parameters of these mechanical elements in those networks are optimized by Particle Swarm Optimization (PSO). Secondly, a semi-active inerter based on Sky-hook control is introduced for the semi-active part of the suspension system. Finally, the semi-active ISD suspension structure is verified by a quarter vehicle model. The simulation results show that the first-order and second-order suspension systems optimize the RMS of the spring mass acceleration by 14.2% and 23.9%, respectively, as compared to traditional suspension systems. Furthermore, frequency-domain analysis also shows that both suspension systems effectively reduce the value of spring mass acceleration in the low-frequency band.

Hybrid Particle Swarm Optimization Genetic LQR Controller for Active Suspension

In this paper, a hybrid particle swarm optimization genetic algorithm LQR controller is used on a quarter car model with an active suspension system. The proposed control algorithm is utilized to overcome the shortcoming that the weight matrix Q and matrix R determined by experience in the traditional LQR control method. The proposed hybrid control method makes it possible to achieve the optimal control effect. A full-order state observer is proposed to observe the state of active suspension. A quarter car active suspension model and road input model are presented at first, and the LQR controller based on the hybrid particle swarm optimization genetic algorithm is utilized in the active suspension system control. Sprung mass acceleration, suspension deflection, and tire dynamic load are selected as the control effect evaluation index. Next, simulation results are presented. According to the results, compared with the passive suspension and active suspension with a traditional LQR control, there is an obvious reduction in the sprung mass acceleration, deflection, and tire dynamic load with an optimized controller under case 1 and case 2. Simultaneously, the system state fed back by the full-order state observer can effectively reflect the true state of the active suspension system.

Theoretical investigation on the underwater sound absorption of a functionally graded anechoic coating under the phased arc array incidence

Laying anechoic coatings on the surface of underwater vehicles is an effective technology to improve the acoustic stealth performance. Meanwhile, the detection waves may have complex directivity, and it is important to study their influence on the sound absorption of the coating. This article introduces a functionally graded coating under a phased arc array incidence, which simulates a novel anechoic coating on an underwater vehicle to absorb sound waves emitted by active sonars. The incident field of the phased array is constructed by spherical harmonic expansion and the superposition principle. The wave propagation of the functionally graded coating is analyzed through an equivalent laminated model and the reverberation matrix method. Utilizing the angular spectrum method, the reflected sound field and absorption coefficient of the coating under the phased arc array incidence are predicted and the theoretical method is formed. Then the selections of parameters in Fourier transforms of the angular spectrum method are discussed for achieving converged results. A finite element analysis is applied to verify the effectiveness and calculation speed of the proposed method through the establishment of detailed quarter or half model. The effect of phased arc array parameters and the coating on the absorption and reflection performances are further studied. The angular spectrum decomposition of the incident sound field explains the changing trends of the sound absorption curves. The present work provides an important way to deal with this complex underwater sound propagation problem.

LQR force command planning–based sliding mode control for active suspension system

In this article, a linear quadratic regulator (LQR)-based sliding model control strategy was proposed for the commercial vehicle seat suspension system. First, the multiple degrees of freedom mechanical dynamics model of a quarter suspension system was built. Then, the LQR force command planner was designed based on mechanical dynamics to ensure driver comfort. Second, considering the mechanical dynamics augmented with hydraulic actuator dynamics, a proportional-integral sliding mode control strategy was developed to track the reference force, which was calculated by the LQR force command planner in real time. Taking the problems of noise disturbances and unavailable full states feedback into consideration, the Kalman filter and tracking differentiator were designed and integrated into the control algorithm. Finally, the quarter suspension AMESim model was built, and the proposed control strategy was implemented and verified in the AMESim-Matlab/Simulink co-simulation environment. Comprehensive simulations were carried out. The simulation results, both from time domain and frequency domain perspective, indicated that the seat ride comfort can be effectively improved with the proposed method.

Process optimization of bottom-blown argon for 130t ladle furnace

ABSTRACT A quarter scale water model experiment is employed to investigate the effect of single and double porous plug placement and blowing flow rates on the mixing time, slag eye area, and slag entrapment depth. As a result, when the blowing flow rate is greater than 180 L min–1, the blowing effect of double blowing plugs is better than that of single blowing plugs. The open eye area and slag entrapment depth in the double blow plug arrangement are smaller than that in the single blow plug arrangement. In general, the ladle refining effect is better when the blow plug is arranged at 0.4R position and the angle between the two blow plugs is 120°. The final recommended argon blowing process is 240–300 L min–1 for the heating and alloying process and 60–120 L min–1 for the soft blowing process, respectively.