Changrong Liao

Neural network compensation of semi-active control for magneto-rheological suspension with time delay uncertainty

This study presents a new intelligent control method, human-simulated intelligent control (HSIC) based on the sensory motor intelligent schema (SMIS), for a magneto-rheological (MR) suspension system considering the time delay uncertainty of MR dampers. After formulating the full car dynamic model featuring four MR dampers, the HSIC based on eight SMIS is derived. A neural network model is proposed to compensate for the uncertain time delay of the MR dampers. The HSIC based on SMIS is then experimentally realized for the manufactured full vehicle MR suspension system on the basis of the dSPACE platform. Its performance is evaluated and compared under various road conditions and presented in both time and frequency domains. The results show that significant gains are made in the improvement of vehicle performance. Results include a reduction of over 35% in the acceleration peak-to-peak value of a sprung mass over a bumpy road and a reduction of over 24% in the root-mean-square (RMS) sprung mass acceleration over a random road as compared to passive suspension with typical original equipment (OE) shock absorbers. In addition, the semi-active full vehicle system via HSIC based on SMIS provides better isolation than that via the original HSIC, which can avoid the effect of the time delay uncertainty of the MR dampers.

Characterization of stratification for an opaque highly stable magnetorheological fluid using vertical axis inductance monitoring system

A key requirement for the commercialization of various magnetorheological fluid (MRF)-based applications is sedimentation stability. In this study, a high viscosity linear polysiloxane (HVLP), which has been used for shock absorbers in heavy equipment, is proposed as a new carrier fluid in highly stable MRFs. The HVLP is known to be a thixotropic (i.e., shear thinning) fluid that shows very high viscosity at very low shear rate and low viscosity at higher shear rate. In this study, using the shear rheometer, the significant thixotropic behavior of the HVLP was experimentally confirmed. In addition, a HVLP carrier fluid-based MRF (HVLP MRF) with 26 vol. % was synthesized and its sedimentation characteristics were experimentally investigated. But, because of the opacity of the HVLP MRF, no mudline can be visually observed. Hence, a vertical axis inductance monitoring system (VAIMS) applied to a circular column of fluid was used to evaluate sedimentation behavior by correlating measured inductance with the v...

A study of an inner bypass magneto-rheological damper with magnetic bias

In this paper, a type of magneto-rheological (MR) damper with an inner bypass and magnetic bias is proposed to fulfill the requirements of both large scalability and low base-damping, which are critical for vibration suppression. With the magnetic bias feature, low base-damping and large scalability can be obtained by the bi-directional excitation of the applied current. The inner bypass feature can eliminate or alleviate the flow block that occurs in the damping gap, however keeping the advantage of suitability for vehicle suspension installation. In contrast to the original mixed mode, the new MR damper adds a concentric damping gap in the piston, which is controlled by the magnetic field, while the original gap will be free of any magnetic field because of the shielding by non-magnetic material. The magnetic bias in the added gap is obtained by the inclusion of a permanent magnet in the piston. A magnetic analysis is carried out to verify the magnetic distribution under permanent and electro-magnetic excitation. Based on the fabricated prototype, both quasi-steady and dynamic tests are carried out, and it is shown that the MR damper achieves bi-directional operation of the damping force with scalability up to 8, and that the flow block is partly alleviated in a high applied current.

Long term stability of magnetorheological fluids using high viscosity linear polysiloxane carrier fluids

Stability of magnetorheological fluids (MRFs) or suspensions has been a key issue in the development of various practical applications. In our prior work, it was experimentally confirmed that a high viscosity linear polysiloxane carrier fluid based MRF (hereinafter HVLP MRF) with 26% particle volume fraction (hereinafter 26 vol%) showed high sedimentation stability for 96 days because HVLP carrier fluids have remarkable shear thinning behavior, that is, very high viscosity at low shear rate but low viscosity at high shear rate. In addition, the effects of HVLP carrier fluid viscosity and carbonyl iron (CI) particle concentration on suspension stability were investigated with the objective of synthesizing highly stable HVLP MRFs for practical applications. The HVLP MRFs were synthesized by suspending nominally 32 vol% of CI particles in carrier fluids with different viscosities (i.e., 140, 440, and 800 Pa s). To illustrate the effect of particle concentration on suspension stability, because it is well known that suspension stability increases as particle concentration increases, two low concentrations, 5 and 10 vol%, and two high concentrations, 20 and 32 vol%, were prepared to demonstrate MRFs with relatively severe sedimentation, and stable suspensions, respectively. A vertical axis inductance monitoring system was employed to evaluate the suspension stability of the HVLP MRFs for 365 days by scanning the inductance of the MRF samples in a vertical fluid column, and logging this data with respect to height and time. In addition, the suspension stability of a commercially available MRF (i.e., Lord MRF-132DG) was also measured and compared with similar measurements for HVLP MRFs.

A Comparison of Suitable Control Methods for Full Vehicle with Four MR Dampers Part II Controller Synthesis and Road Test Validation

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.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 damp...

Piezo-capacitive behavior of a magnetically structured particle-based conductive polymer with high sensitivity and a wide working range

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 Youngs 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.