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Although the quasi-static model is widely employed in various engineering fields to guide the design of magnetorheological (MR) dampers, it is not accurate enough to describe the dynamic behaviors of MR dampers. In this study, an unsteady Bingham plastic (US-BP) model that considers fluid inertia is established. The proposed model can realize flexible switching between flow mode and mixed mode by introducing a mode parameter. To employ the US-BP model for MR dampers under different excitations, a technique combining the Fourier series method and Laplace transform is developed to deduce the velocity profiles of MR fluids. Based on the US-BP model, the damping characteristics of an MR damper under different excitation frequencies, yield stresses, and mode parameters are theoretically investigated. Furthermore, an unsteady hysteretic Bingham plastic (USHY-BP) model that incorporates particle chain deflection theory is developed to characterize the hysteretic behavior and inertia effect of the damping force. Comparisons between the simulation results and the experimental data reveal that the US-BP model can predict the unsteady behaviors of damping forces caused by fluid inertia but fails to capture the hysteresis characteristic. The USHY-BP model achieves good performance and accuracy in characterizing the dynamic properties of MR dampers.

As a novel conductive elastomer, magnetorheological elastomers (MREs) featuring both high sensitivity and wide working range have been employed as a new sensing material for flexible tactile sensors. Their sensing mechanism, that is, the spatial distribution rearrangement of particles under compression, completely differs from their conventional counterparts. The piezo-capacitive effect of MREs resulting from the unique mechanism of particles rearrangement is actually a response to the microscopic mechanical movement of particles. This nature brings a core concern on the intrinsic relationship between their mechanical and electrical properties. This study illuminates them from the perspective of electrical creep and recovery behavior of MREs. We give a meaningful analysis for the capacitance creep-recovery mechanism. The experimental fact strongly demonstrated that the particles rearrangement was the direct cause, while the strain creep was an indirect cause. All the behaviors were well interpreted by an evolution mechanism of the particles rearrangement driven by the mechanical strain creep of the flexible matrix under constant pressure. In simpler terms, the electrical creep was induced by the mechanical creep. We further explored the creep effect in practical applications and found a “self-healing” behavior, which indicated that the MRE sensors could obtain a stable sensing capability after a pre-processing.

The excellent suspension stability of the high-viscosity linear polysiloxane magnetorheological fluid (HVLP MRF) makes it a great controlled medium for magnetorheological energy absorbers (MREAs). In our previous work, the Herschel–Bulkley flow model (HB model) was used to describe the shear-thinning rheological behavior and establish the dynamic model of an HVLP MRF-based MREA with radial flow mode. However, as the established model was implicit, the MREA response time increased and the buffer effect was degraded. To improve the time response characteristics, an explicit dynamic model based on the HB model incorporating minor losses (called the E-HBM model) is proposed in this study. The model parameters were identified based on the HBM model. To verify the E-HBM model, five evaluation parameters for the energy absorption performance of the MREA, that is, peak force, mean force, crush force efficiency, specific energy absorption, and stroke efficiency, were introduced to compare the theoretical results with the experimental results obtained using a high-speed drop tower facility with a mass of 600 kg. Then, the relative error of the crush force efficiency, specific energy absorption, and stroke efficiency was quantitatively and comprehensively analyzed considering the E-HBM model and experimental results. The results indicate that the proposed E-HBM model agrees with the impact behavior of the radial flow mode MREA.

Current source is an indispensable component of magnetorheological (MR) systems. Though MR fluid has a phase change as fast as in 1 ms, the response of MR damper (MRD) to generate the damping force may be two orders of magnitude longer. Therefore, the rapid response of current source is a key to realize the real-time semi-active control of MR devices. This study proposes a programmable high-speed, low-cost current source exclusively for MR devices based on the synergy between supercapacitor and Buck converter (i.e., SSBC current source). SSBC current source features a strategy consisting of a lifting phase of supercapacitor and a following maintaining phase of Buck converter. Specifically, the high power density of supercapacitor contributes to rapidly lifting/raising the initial current, and then, like a “relay race”, the expected output is maintained through a Buck converter. Theoretical modeling and experiments are performed systematically. The response times (@ 95% of expected outputs) measured are 0.44, 0.84 and 1.88 ms for the outputs of 3, 6 and 9 A, respectively; these values are highlighted as the fastest level in this field. Besides, the response can be up to 24.6 and 43.7 times faster than the cases using supercapacitor and Buck converter to directly drive the MRD, respectively. SSBC current source is employed to generate a sequence of currents/magnetic inductions, only four variables of which need to be controlled programmatically: the order of lifting and maintaining phases, switching time of lifting phase, PWM duty cycle of Buck converter and duration of maintaining phase. The response time stability is verified by 100 cycles of on/off tests, showing a fluctuation of only 1.1%, which indicates a very reliable high-speed response. This study provides an exclusive power supply with a novel strategy for MR devices, which is believed to be an important promotion for MR technologies.

The flame-retardant polyamide 66 composites (FR-PA66) were prepared by in situ loading of amino-functionalized polyphosphazene microspheres (HCNP), which were synthesized in the laboratory and confirmed by a Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM). The thermal stabilities and flame retardancy of FR-PA66 were measured using thermogravimetric analysis (TGA), a thermogravimetric infrared instrument (TG-IR), the limiting oxygen index (LOI), the horizontal and vertical combustion method (UL-94), and a cone calorimeter. The results illustrate that the volatile matter of FR-PA66 mainly contains carbon dioxide, methane4, and water vapor under heating, accompanied by the char residue raising to 14.1 wt% at 600 °C and the value of the LOI and UL-94 rating reaching 30% and V-0, respectively. Moreover, the addition of HCNP decreases the peak of the heat release rate (pHRR), total heat release (THR), mass loss (ML), and total smoke release (TSR) of FR-PA66 to 373.7 kW/m2, 106.7 MJ/m2, 92.5 wt%, and 944.8 m2/m2, respectively, verifying a significant improvement in the flame retardancy of PA66.

A Fe2O3 film homojunction was orderly prepared by magnetron sputtering and a hydrothermal method. The Fe2O3 homojunction-based memristor exhibits an obvious self-selective effect as well as a typical analogue resistive switching (RS) memory behavior. A desirable self-rectifying voltage range (−1 to 1 V), stable resistance ratio, good cycling endurance (>104 cycles), and long retention time (>104 s) can be obtained from the Fe2O3 homojunction-based memristor. Oxygen vacancies (Vo) are inevitably generated during the growth of the Fe2O3 film. The self-selective analogue RS memory behavior is ascribed to the electron tunneling behavior between the potential barrier generated by the FeO x contact and the electron filling dynamic in the Vo-based traps. This work provides a simple method to prepare a self-selective analogue memristor and lays the foundation for the core device of neuromorphic computing.

Despite several salient benefits of numerous control systems utilizing magnetorheological (MR) fluid, practical realization of commercial products is limited due to the particles sedimentation. To overcome this problem, several measures have been proposed to optimize MR fluid settling through the viewpoints of dispersing medium viscosity, suspension force of dispersed phase and additives innovation, but the settling of MR fluid can be alleviated to an extent only. An active dispersing mechanism (ADM) proposed in the previous work is one of attractive ways to resolve the sedimentation problem in a level of device and it is promising to fulfill good serviceability for MR dampers even if the settling remains. In this work, attributive to the investigations in stirring devices, rotary blades are employed to fulfill the redispersing of settled MR fluid under the theory of solid–liquid two phase flow. The parameters and working conditions of the rotary blades are optimized to guide experimental verification in a damper-sized vessel. The vessel can be seen as a prototype for real MR damper. An immersed induction method for the characterization of the localized MR fluid concentration is proposed to designate the dispersing process when ADM is started. With the experiments of different MR fluid volume fractions and rotating speeds of the rotary blades, it is fully testified that the faster the blades rotate, the shorter the mixing time, and the more the inclination angle of blades close to 45°, the better the dispersion capability. In addition, it is also identified that the ADM is effective to disperse the settled MR fluid and promising to the sedimentation immunity of MR damper.

Theoretical modeling is often applied to study magnetorheological dampers (MRDs) with dimensional and non-dimensional analyses. In contrast to dimensional models, non-dimensional analyses can eliminate the influence of dimensionality and reduce the number of redundant parameters to simplify theoretical modeling and provide more universal applicability. However, most previous non-dimensional analyses have been based on quasi-steady flows that cannot reflect the transient response of an MRD because of the key assumption that the fluid velocity changes instantaneously. This study presents an investigation of the transient response of an MRD using a non-dimensional analysis approach based on an unsteady model. We focus on the step response of the MRD with a step excitation of the piston speed, while the magnetic field is kept constant. For a comprehensive analysis, a set of dimensionless parameters are defined, including a non-dimensional coordinate, a non-dimensional time parameter, the Bingham number, a non-dimensional pre-yield thickness, a damping coefficient, and a hydraulic amplification ratio. The relationships between these dimensionless numbers are analyzed. An unusual “concave area” is found in the velocity profile instead of a simple rigid flow during the transient process under a magnetic field. However, when the non-dimensional time is 0.4, the delayed concave area disappears, and the rigid area fluid velocity reaches 98% of its stable value.

In this paper, the crush characteristics of multilayer corrugated tube are theoretically investigated under axial impact loading conditions. The deformation process of corrugated tube during impact is divided into four stages: elastic stage, plastic stage, transitional stage and compact stage. Based on Kellogg model, a theoretical analysis is conducted for the four stages, respectively. Expressions of the four deformation forces with respect to crush displacement at different drop heights are deduced. Further, evaluation parameters for the energy absorption performance of corrugated tube, i.e., specific energy absorption, peak force, mean force, crush force efficiency and stroke efficiency are obtained and analyzed. Experiments at various drop heights are conducted in order to verify the theoretical analysis. The results show a good agreement between the experimental data and theoretical prediction, which indicates a helpful theoretical approach for the further understanding and development of corrugated tube under axial impact.

High-viscosity linear polysiloxane–based magnetorheological fluid features its excellent suspension stability. Few reports could be found for magnetorheological energy absorbers using such highly viscous but highly stable magnetorheological fluids as the controlled medium. This study presents a design strategy for the high-viscosity linear polysiloxane–based magnetorheological fluid–based magnetorheological energy absorber with multi-stage radial flow mode. The design strategy is based on the Herschel–Bulkley flow model incorporating minor losses proposed in our prior work. The optimal geometrical parameters were obtained by gradually reducing the number of unknown variables. By analyzing the effect of thicknesses of baffle and outer cylinder and number of coil turns on magnetic circuit, the distribution of magnetic flux in the effective region of magnetorheological valve was optimized. Furthermore, a magnetorheological energy absorber was fabricated and tested using a high-speed drop tower facility with a 600 kg mass. The maximum nominal impact velocity was 4.2 m/s, and the applied current varied discretely from 0, 1, 2, to 3 A. Comparison of our Herschel–Bulkley flow model with measured data was conducted via analysis of peak force, dynamic range, and maximum displacement that indicate the performance of magnetorheological energy absorber. The results validated the effectiveness of the design strategy for the high-viscosity linear polysiloxane–based magnetorheological fluid–based magnetorheological energy absorber.

Conductive polymers (CPs), which consist of conductive particles dispersed in a flexible polymer matrix, are an emerging material for application in flexible tactile sensors due to their piezo-capacitive effects. We employed a magnetic field to synthesize a CP, i.e., a magnetically structured nickel–silicone rubber composite (S-NSRC hereafter), in order to maximize its sensitivity as well as its working range. The S-NSRC-based sensor features extraordinary sensitivity, e.g., a S-NSRC can achieve up to 460 kPa−1 in value, which is orders of magnitude higher than those of its traditional counterparts. Meanwhile, S-NSRC occupies a wider working range (around 200 kPa) because the dispersed particles reinforce its Young's modulus. We also demonstrate its high temperature stability, where the capacitance change from 30 °C to 100 °C is only 3.5% of the resistance change (the piezo-resistive effect). The piezo-capacitive behavior of S-NSRC is studied under the impacts of curing field strength, field direction and particle volume fraction. Additionally, the piezo-resistive behavior, response time, hysteresis and loading rate effects are investigated experimentally. We found unusual piezo-capacitive behaviors for S-NSRC, such as strong nonlinearity, decreasing capacitance after saturation, and breakdown behavior. These behaviors are a macroscopic reflection of how well the particles rearrange their spatial distribution under compression. All these behaviors can be readily interpreted by analysis of the rearrangement of the particles under compression along with the evolution mechanism of the initial distribution of particle microstructures induced by different magnetic field levels.

This study addresses the synthesis and field-dependent rheological characteristics of novel magnetorheological fluids (MRFs) using high viscosity linear polysiloxanes (HVLPs) as a carrier fluid. First of all, the components and preparation of novel HVLP-based MRFs (HVLP MRFs) were explained in detail and the microscopic images of each component were taken by using scanning electron microscope (SEM). Four HVLP MRF samples with different particle volume fractions of 10, 15, 20, and 26 vol% in the same HVLP carrier fluid viscosity of 800 Pa·s were synthesized to investigate the particle concentration effect on their field-dependent rheological properties. In order to understand the effect of the carrier fluid viscosity, two more HVLP MRF samples with different HVLP viscosities of 140 and 440 Pa·s in the same particle concentration of 26 vol% were also fabricated. In addition, the temperature effect on HVLP MRFs was studied by using the sample with 26 vol% in particle concentration and 140 Pa·s in HVLP viscosity under different operating temperatures of 25 °C, 40 °C, 55 °C and 70 °C. The flow curve measurements of shear stress versus shear rate in the magnetic fields were conducted by using controlled shear rate (CSR) test method with a commercial parallel-plate type rotational rheometer. From the flow curves, the field-dependent rheological properties of HVLP MRFs including static and dynamic yield stresses and the dynamic range (ratio of field on to field off yield stress) were obtained. These material characteristics were then examined as a function of varying particle concentration, varying carrier fluid viscosity, and varying temperature. A conventional commercial MRF (i.e. Lord MRF-126CD) was adopted for comparison study and its rheological properties under different temperatures were also measured and compared with those of HVLP MRFs. Using HVLP carrier fluids, it was demonstrated that the HVLP MRFs exhibited much greater suspension stability than the conventional commercial MRF.

To optimize the online friction coefficient adjustment, it is necessary to study the parameter change features of the magneto-sensitive polymer and its influence on the friction characteristics under magnetic field. A series of magnetorheological elastomers (MREs) with different initial surface roughness were prepared, and a sliding friction platform with MRE—copper block pair was built to carry out magnetic-controlled friction characteristic experiment. Results show that the sliding friction coefficient of MRE decreases with the increase of the magnetic field, but the degree of reduction is quite different under different initial surface roughness and elastic modulus. When the initial surface roughness of MRE is between 0.5 and 2.5 μm and the carbonyl iron particles volume fraction is between 10% and 15%, its magnetic-controlled friction coefficient has the largest reduced value of 22.75%. Moreover, features of elastic modulus and surface topography under magnetic field were tested and analyzed. By combining with the single peak contact model and the friction binomial law, the relationship between the surface roughness and elastic modulus of MREs and the sliding friction force is deduced, and it is proved that the friction coefficient is affected by the coupling effect of surface roughness and elastic modulus. The magnetic-controlled elastic modulus is the key factor, which determines the overall downward trend of the friction coefficient of MREs. Magnetic-controlled surface roughness also plays an important role in the adjustable range of friction coefficient, and reducing the initial surface roughness can increase the magnetic-controlled friction coefficient adjustable range.

Even though disk springs with non-uniform thickness have the advantages of improving the load capacity, optimizing the stress distribution, and adjusting the stiffness characteristics, their exploration remains sparse. Prior analytical models for non-uniform disk springs were based on the Almen–Laszlo theory, and the model verifications lacked the support of experiments. A mechanical model of linearly gradient thickness (LGT) disk springs is established in this study in the cylindrical coordinate system based on the theory of plates and shells. A new analytical equation as a function of material and geometric parameters is developed to describe the load–deflection characteristics of LGT disk springs. The load–deflection characteristics of disk springs with different thickness variation parameters are compared through cases with a constant mid-radius thickness and constant flattened load, respectively. Moreover, the stiffness, deformation energy, and stress distribution of the disk springs are also systematically analyzed. To verify the proposed model and characterize the nonlinear load–deflection properties of LGT disk springs, specimens were fabricated, and experimental tests were conducted. Comparisons between the analytical results and experimental data demonstrate the superior effectiveness and accuracy of the developed analytical model in predicting the load–deflection characteristics of disk springs with uniform thickness or LGT. The results from the analytical and finite element methods indicate that the proposed model can describe the load–deflection characteristics of disk springs with different cone angles.

The dynamical characteristics research of planetary gear system with tooth pitting is useful for early fault diagnosis and monitor. However, it is an unsolved puzzle to establish the relationship between tooth pitting and dynamical characteristics. In this study, a pitting fault analytical model is proposed to investigate the effects of tooth pitting on the gear mesh stiffness. Then this mesh stiffness with tooth pitting is incorporated into a dynamical model of planetary gear system, and the effects of the tooth pitting on the vibration characteristics is investigated. The simulated results show that the time-varying mesh stiffness is reduced with tooth pitting propagations along width or depth direction. The mesh frequency and its harmonics are mainly frequencies components in the frequency spectrum of dynamic mesh force, but sidebands caused by the tooth pitting are more sensitive than the mesh frequency and its harmonics. The tooth pitting frequency and its harmonics also increase with the rising rotational speed of the sun gear. In addition, both relative statistical indicators of RMS and Kurtosis increase with the growth of tooth pitting size. But the relative indicators have different sensitivity on the vibration signal type. These results could supply some guidance to the condition monitoring and fault diagnosis of planetary gear system, especially to the gear tooth pitting at early stage.

Magnetic polymeric composite has variable capacitance based on the adjustable arrangement of magnetic particles controlled by magnetic field. Considering the capacitive effect on the surface charge density of tribo-materials has important influence on the output performance of TENG, it is of great significance to study the magnetic polymeric composite as the tribo-material of TENG from a microscopic perspective. Here, an approach of using a magnetic polymeric composite film as the tribo-material is proposed to effectively enhance the output performance of TENG (M-TENG). After studying the influence of the cured magnetic flux density, filling particle concentration and particle size, a sustainable and enhanced output of 32.6 μA (short-circuit current) and 233.4 V (open-circuit voltage) were obtained, and a peak output power of 2.5 mW was gained from the M-TENG under a loading resistance of 3 MΩ, giving over 4.7-fold enhancement than the TENG which was based on the pure silicone rubber mixture film (0.53 mW). Finally, a real-time automatic target-scoring system was constructed to illustrate the practical value of M-TENG as a self-powered sensor.

We theoretically explored the possibility of monolayer tellurene detecting nucleobases and amino acids by means of first-principles calculation. The obvious differences of adsorption energy between nucleobases indicate that monolayer tellurene can be used for DNA sequencing. The order of adsorption strength is G > A > C > T > U. Moreover, monolayer tellurene exhibits more excellent sensing performance to TYR, PHE and TRP than to HIS, which means that tellurene can be used for detecting amino acids. Besides, we explored the adsorption mechanism of nucleobases and amino acids on tellurene by ELF, which demonstrate nucleobases and amino acids are all physically adsorbed on tellurene. The calculated results of PDOS show that orbital hybridization is the primary cause of charge transfer between each biomolecule and monolayer tellurene. Furthermore, the results of absorption coefficient and refractive index further prove that tellurene can detect nucleobases and amino acids. Therefore, we conclude that monolayer tellurene can be a promising candidate for biosensor to detect nucleobases and amino acids.

This article has been retracted at the request of the Editor-in-Chief as the authors have used Professor Miao Yu's name in the article without his authorization. Besides, the work presented in the article came from professor Miao Yu's laboratory and was supported by the National Natural Science Foundation of China. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter.

Magnetorheological elastomers (MRE) are mainly composed of soft magnetic particles and rubber-like matrix. Previous studies have shown that the matrix has a greater impact on mechanical properties of MRE. In this article, a new kind of polyurethane material was fabricated and used as the matrix of MRE. The effect of several factors on the mechanical properties of MRE samples was experimentally studied, such as fabrication condition, content of iron particles, different weight ratio of castor oil and diphenylmethane diisocyanate, plasticizer. Their microstructures were observed, and the mechanical properties were measured using a testing system in the presence of an external magnetic field. The experimental results demonstrate that these factors have different impact on shear storage modulus, magneto-induced modulus, MR effect and damping property. In addition, the damping property of these MRE is also higher than that of MRE based on the other matrix. This study can hopefully be applied to optimize the mechanical properties of MRE. POLYM. COMPOS., 37:1587-1595, 2016. (c) 2014 Society of Plastics Engineers

The spring of magnetorheological energy absorber (MREA) is an indispensable component that provides a restoring force for the piston back to the initial position. To reduce impact force, the stroke of a typical MREA is usually sacrificed (i.e., extended stroke and prolonged buffer time). In some situations, however, a fast return of piston is required and the impact load is huge. It is difficult for conventional coil/gas springs to qualify due to the limitations in obtaining high stiffness. In this study, we employ the disc spring as a rebound element for MREA because of its feature in providing large force within narrow deformation. Optimal designs are significant for improving the MREA performance, but most of them have been developed based on the quasi-static model that ignores inertia effect. However, the inertia effect becomes an important role in dynamic behavior under high-speed impacts. Most recently, we proposed a full dynamic model considering inertia effect by using the non-averaged acceleration. As a further step, this study presents a design methodology based on this full dynamic model for an MREA with disc spring. The design objective is to identify the geometric dimensions of disc spring and MR valve to return the piston back to its initial position as fast as possible after a fast impact loading. The design flowcharts for disc spring and MR valve are presented. The load-deflection relationship of disc spring is obtained based on Almen–Laszlo theory. The magnetic field intensity in the MR gap is analyzed by using Kirchhoff's law and the magnetic flux conversation rule. Two identical MREAs are fabricated and tested via a high-speed drop tower system. The effectiveness of the design methodology is validated by a comparison of MREA behaviors between the tests and full dynamic modeling.

Theoretical models are of great significance in the development of magnetorheological energy absorbers (MREAs). There are two types of models, i.e., quasi-steady and dynamic models, depending on whether considering the inertia effect. It is necessary to perform comparative analysis between different models to determine the superiority of a model regarding a specific type of MREA. In our previous work, we proposed a dynamic model by using non-averaged acceleration (NA-BPIM model). This study focuses on giving a comprehensive comparative analysis for the NA-BPIM model with a quasi-steady and another dynamic model (considering inertia effect using area-averaged acceleration, AA-BPIM) for MREA under impact conditions. In order to evaluate the superiority of the models, the comparative analysis is qualitatively and quantitatively performed from the following three aspects: (1) the accuracy of theoretical model to predict MREA peak force, (2) the global agreement of dynamic force curves between model and experiment results and (3) the accuracy of theoretical model to predict the dynamic range. Specifically, the quantitative evaluations are conducted by means of the relative error, REPF, for MREA peak force, the mean absolute percentage error (MAPE), for the dynamic force curves and the relative error, REDR, for MREA dynamic range. The results show that the REPF, MAPE and REDR of the NA-BPIM model are the smallest when the test condition is given, demonstrating that the dynamic model incorporating non-averaged acceleration is the best to predict MREA dynamic force under high-speed impacts.

The quasi-static model, without considering the inertia effect, is usually used to design and evaluate magnetorheological energy absorbers (MREAs). Although the quasi-static model is generally acceptable to describe the behavior of MREA operated at low velocity and low frequency, it is not sufficient to predict that under high-speed impact conditions. For this situation, we develop an analytical model inclusive of fluid Inertia as well as Minor losses based on the Bingham-plastic model (called BPIM model). In particular, instead of using area-averaged acceleration (assuming fluid acceleration uniformly distributes over the flow cross-sectional area), we directly take the non-averaged acceleration to analyze fluid inertia. Then, the governing equation is obtained from Navier–Stokes equations and continuity equation, in which the time-related term representing inertia effect is no longer neglected. In addition, the expression of damping force is derived by solving the initial-value problems obtained from the governing equation, boundary conditions and initial conditions using the method of separation of variables. Further, the influence of inertia effect and minor losses on MREA force is quantitatively analyzed. Besides, the MREA coupled with disc springs as the storage element is presented, and the nonlinear model of disc spring is employed. To validate the theoretical model, two identical MREAs are fabricated, and a high-speed drop tower is set up to test the two MREAs placed in parallel. It is shown that the BPIM model is capable of well predicting the dynamic behavior of the MREA.

A new adaptive variable stiffness absorber was proposed based on a smart material, magnetorheological elastomer (MRE), and its vibration control performance was investigated. Before developing the proposed absorber, the MREs were firstly fabricated by curing a mixture of 704 silicon rubber, carbonyl iron particles and a small amount of silicone oil under an external magnetic field. Then the mechanical properties of the fabricated MREs were measured. On the basis of the measured mechanical characteristics, the MRE absorber was developed and its working characteristics were also tested under various input currents and excited frequencies. Finally, the control responses of a two-degree-of-freedom dynamic system with a MRE absorber were presented under a chirp input and used to evaluate the effectiveness of the MRE absorber.

Reducing the vibration of an automotive magnetorheological (MR) suspension system can contribute greatly to enhancing vehicle performance. However, it is difficult to design a control system that depends on a complicated whole-vehicle vibration model. This paper proposes a hierarchical controller that consists of a control level and a coordination level for heave, roll, and pitch vibration control of a vehicle with an MR suspension system. On the control level, a local fuzzy controller is designed for each quarter-vehicle MR suspension system, based on a hybrid control strategy of skyhook control and groundhook control. On the coordination level, a coordination controller is designed to tune four local independent fuzzy controllers by adjusting their output parameters on the basis of system feedback. A test and control system for MR suspensions is set up and implemented on a minibus equipped with four controllable MR dampers. The results on random rough roads confirm that the hierarchical controller can reduce automotive vertical vibration, roll motion, and pitch motion more effectively than a passive suspension or an MR suspension using a hybrid control strategy. It achieves better ride comfort and automobile handling stability, although data for bump input indicate that the hierarchical controller does not decrease automotive vertical vibration more effectively than hybrid control or a passive system. However, it yields better results in decreasing pitch and roll motions.

An engine isolation system via tuneable damping mounts can contribute to enhanced automobile performance. In this study, a magnetorheological fluids (MRF) mount in squeeze mode for engine isolation is proposed and its damping characteristics are analysed. Based on an engine isolation dynamic model with three degrees of freedom, a hierarchical fuzzy control (HFC) system is proposed to decrease the vertical vibration force and roll moment transmitted from an engine to a foundation. On the control level, a fuzzy controller is designed to isolate the engine vertical vibration. On the coordination level, fuzzy reasoning is adopted to realize a coordination strategy for tuning the damping of each MRF mount in order to minimize the transmitted torque. The simulation is developed in MATLAB, and the experimental isolation system for an actual engine is built in the laboratory. With wide excitation frequency inputs under different operation conditions, studies on different engine mount isolation systems are carried out. Simulation results indicate that MRF mounts using the HFC strategy have more advantages than passive elastomeric mounts or hydraulic mounts, especially in the low-frequency range. Laboratory results confirm that the engine HFC system via MRF mounts performs markedly better than the passive mount system. The absolute force transmissibility ratio and torque transmissibility ratio are reduced to lower than 0.3 in actual complex excitation, which is very significant for an improvement in noise, vibration, and harshness.

The significant non-linearity and uncertainty in the behavior of magnetorheological (MR) suspension systems has been one of the main challenges in the application of this technology in the development of appropriate control algorithms. Here, four model-free control algorithms studied theoretically in prior work are applied to a full vehicle featuring four MR dampers and evaluated through road test to identify the most suitable control algorithm. The four model-free control algorithms include the well-known skyhook control, the hybrid control, the fuzzy logic control, and a newly proposed intelligent control algorithm, the human simulated intelligent control (HSIC). As the first step, four MR dampers (two for the front parts and two for the rear parts) are designed and manufactured based on the damping-force levels and mechanical dimensions of stock dampers of the test vehicle. After experimentally measuring the magnetic-field-dependent force property and controllability, a precise inverse model of MR damper is formulated. Subsequently, four controllers are developed and implemented using the rapid control prototyping technology. Then the road test with different control schemes is undertaken under various road conditions and vehicle speeds. For comparison purposes, the road test of the passive suspension system with four stock dampers is also carried out under the same conditions as that of the MR suspension system. Finally, the control responses for ride comfort and stability are evaluated in both time and frequency domains. The results support the conclusion made in the prior numerical analysis that the semi-active suspension system with each control algorithm can improve ride comfort and stability in some indexes, but HSIC algorithm is found to be the most suitable one with four MR dampers in the MR suspension system.

Due to significant nonlinearity of magnetorheological (MR) suspension, one of the main challenges in the application of this technology is to develop appropriate control algorithms. The main purpose of this study is to identify a suitable control method for semi-active isolation in MR suspension application. The semi-active control schemes include the following: a new proposed intelligent control scheme, Human Simulated Intelligent Control (HSIC) and three representative semi-active control schemes that are skyhook control, hybrid control algorithm, and fuzzy logic control. A full-car dynamic model considering the effect of roll motion is adopted as the baseline model for our analysis. After deriving the governing motion equations of the proposed dynamic model, the HSICler and other three controllers with nonlinearity of MR dampers are formulated. Then each control policy is applied to the baseline model equipped with four MR dampers. The performances of each control algorithm under various road conditions are compared along with the equivalent passive model in both time and frequency domains. The results indicate that the semi-active suspension with each control scheme is more effective than the passive in reducing vibration of the vehicle body. The results further indicate that HSICler performs the best among the considered control policies.

This paper presents the stability of a passenger vehicle system featuring magnetorheological (MR) suspensions. As a first step, MR damper is devised and its field-dependent damping force is experimentally evaluated. A full-car model equipped with the MR damper is established by considering roll motion which is directly related to the vehicle stability. A fuzzy neural network controller (FNNC) incorporated with the self-learn knowledge is then formulated in order to improve vehicle stability. In addition, in order to eliminate adverse effect of the system coupling, nonlinearity and time delay a correction component for updating the weighting matrix and adjusting controller outputs is designed. Both computer simulation and road test are undertaken in order to demonstrate the effectiveness of the proposed control method. The control results obtained in this work indicate that the proposed control scheme with the MR suspension can considerably improve the stability of vehicles with high performance in vibration isolation.

The research on magnetorheological (MR) damping technology is booming in recent years. Especially on application to vehicles, both good ride comfort and steering stability must be taken into account. Accordingly, high scalability of MR dampers and their magnetic design are of significance. In this article, the magnetic design of an MR damper is proposed, and a finite element (FE) analysis on the magnetic saturation is discussed for the utmost improvement of the high force. Through experimental verification, the damper force is effectively scaled by the magnetic design.

A magnetorheological (MR) damper model is established and linearized based on theory analyses and real testing. Since the mathematical model of the suspension system is nonlinear and complicated, a model-free fuzzy control algorithm is employed to design a controller for achieving vibration isolation. As a pilot study, two MR dampers are used to replace the passive ones of the front half-car. A quarter-car fuzzy intelligent controller is employed to control the two MR independent suspension systems, respectively. The performance of the MR suspension system is evaluated by road testing. The test results indicate that the vibration of the vehicle body and unsprung mass are both reduced significantly.

Since magneto-rheological (MR) suspension has nonlinearity and uncertainty, a new adaptive fuzzy control strategy using a hybrid Taguchi genetic algorithm (HTGA) is proposed to improve ride quality. The controller consists of two control loops. The inner open loop controls a nonlinear MR damper to achieve tracking of a desired force. The outer loop implements a fuzzy logic controller (FLC) using HTGA. The HTGA is used to tune the membership functions and fuzzy control rules of FLC with initial skyhook control rules. To verify the control performance, FLC based on HTGA for semi-active suspension system is simulated. The simulation results show that FLC based on HTGA can achieve smaller acceleration root mean square (RMS) than simple FLC and better ride quality compared with passive suspension under random input.

Capacitive pressure (i.e., piezo-capacitive) sensors have manifested their superiority as a potential electronic skin. The mechanism of the traditional piezo-capacitive sensors is mainly to change the relative permittivity of the flexible composites by compressing the specially fabricated microstructures in the polymer matrix under pressure. Instead, we study the piezo-capacitive effect for a newly reported isotropic flexible composite consisting of silicone rubber (SR) and uniformly dispersed micron-sized conductive nickel particles experimentally and theoretically. The Young's modulus of the nickel-SR composites (NSRCs) is designed to meet that of human skin. Experimental results show that the NSRCs exhibit remarkable particle concentration dependent capacitance response under uniaxial pressure, and the NSRCs present a good repeatability. We propose a mathematical model at particle level to provide deep insights into the piezo-capacitive mechanism, by considering the adjacent particles in the axial direction as micro capacitors connected in series and in parallel on the horizontal plane. The piezo-capacitive effect is determined by the relative permittivity induced by the particles rearrangement, longitudinal interparticle gap, and deflection angle of micro particle capacitors under pressure. Specifically, the relative capacitance of NSRC capacitor is deduced to be product of two factors: the degree of particle rearrangement, and the relative capacitance of a micro capacitor with the average longitudinal gap. The proposed model well matches and interprets the experimental results.