Improvement of rheological and transient response of magnetorheological grease with amalgamation of cobalt ferrite

The time responsiveness of magnetorheological grease (MRG) towards magnetic field stimulus is crucial in order to ensure the high performance of MR devices. However, due to the thixotropic properties of grease, MRG has been restricted in terms of responding rapidly towards these magnetic fields. Therefore, polygonal shapes made up of 1–3 of cobalt-ferrite (CoFe2O4) particles with different concentrations from 0 to 5 wt.% were introduced to enhance the responsiveness of the MRG. The results revealed that the linear viscoelastic (LVE) region of the modified MRG improved between 29% and 43% during the off-state and on-state conditions, respectively. The absolute MR effect of MRG increased by at least 60% due to the improvement in the particle's chain alignment with that of the applied magnetic fields. In terms of transient responses, particularly within the highly acceptable LVE region (0.05%), the MRG with CoFe2O4 performed about 5–6 s faster as compared to pure MRG, which was attributed to the improvement in the particle's mobility in the grease medium.

Optimal control strategy for low speed and high speed four-wheel-active steering vehicle

In this work, based on the optimal control theory approach, a four-wheel-active steering (4WAS) system is proposed for low speed and high speed applications. A model following the control structure is adopted consisting of a feed-forward and feedback compensation strategy that serves as correction inputs to enhance the vehicle’s dynamic behavior. The velocity dependent feed-forward control inputs are based on the driver’s steering intention while the feedback control inputs are based on the vehicle’s state feedback errors, being the sideslip and yaw rate of the vehicle. Numerical simulations are conducted using the Matlab/Simulink platform to evaluate the control system’s performance. The performance of the 4WAS controller is tested in two designated open loop tests, being the constant steer and the lane change maneuver, to evaluate its effectiveness. A comparison with conventional passive front-wheel-steering (FWS) and conventional four-wheel-steering (4WS) systems shows the preeminent result performance of the proposed control strategy in terms of the response tracking capability and versatility of the controller to adapt to the system’s speed environment. In high speed maneuvers, the improvement in terms of yaw rate tracking error in rms is evaluated and the proposed active steering system considerably beat the other two structures with 0.2% normalized error compared to the desired yaw rate response. Meanwhile, in low speed, turning radius reductions of 25% and 50% with respect to the capability of normal or typical FWS vehicles are successfully achieve

Modelling and Force Tracking Control for Newly Type Configuration of Magneto-rheological Damper

The objective of this paper is to model hysteresis behaviour of new MR damper configuration by using nonparametric model approaches. The approaches are nonparametric linearised data-driven (NPLDD) single input model, non-parametric linearised data-driven (NPLDD) double input model, and simple polynomial model. The modelling is developed to ensure the force of MR damper is tracked to any input force. The NPLDD model is developed based on look-up table while the polynomial model is developed based on curve fitting from the experimental results and consists of a pair of subsystems namely positive and negative acceleration which corresponds to the upper and lower curves. From the simulation results, the NPLDD double input model shows better performance in describing non-linear hysteresis behaviour of the MR damper compared with others. By using the NPLDD model, a force tracking based on PI controller has been developed. It is verified that the NPLDD model together with the PI control strategy has the capability to track the desired damping force well

Incorporation of cobalt ferrite on the field dependent performances of magnetorheological grease

Magnetorheological grease (MRG) is one of the smart materials that experiences a high off state viscosity, which hassles the operation of devices at the beginning and causes more energy consumption upon operation. Therefore, this paper investigates the off-state viscosity of MR lithium-based grease with various percentages of cobalt ferrite (CoFe2O4), as these particles are believed to potentially enhance the field-dependent stress of MRG by reducing the off-state viscosity and increasing mobility of the magnetic particles as the magnetic field applied. The MRG with various concentrations of CoFe2O4 at a ratio of 1 e5 wt.% were investigated via Field-Emission Scanning Electron Microscopy (FESEM) and Vibrating Sample Magnetometer (VSM) to analyze their morphology and magnetic properties, respectively. The rheological test of MRG samples in terms of viscosity, shear stress and yield stress were investigated upon shear rate, using rheometer. The results demonstrated that with the incorporation of 5wt.% CoFe2O4 particles, the initial off-state viscosity was reduced by 86% as compared to the pure MRG. The presence of CoFe2O4 particles triggered more chaotic motion thus restricted the formation of agglomeration of particles during shearing process. Meanwhile, the initial viscosity of MRG increased as a 0.64 T of magnetic field was applied along with the increased of CoFe2O4 particles. In fact, there was an enhancement of shear stress and yield stress on the CoFe2O4 incorporated MRG samples as compared with pure MRG. This study underlined the influence of CoFe2O4 particles, which could reduce the initial viscosity of MRG and improve the rheological properties upon the application of magnetic field

Elucidating hepatic lipidosis in stray cats through serum biochemistry, liver histopathology and liver RNA expression of PPAR-δ and PPAR-γ

Early detection of feline hepatic lipidosis (FHL) with appropriate treatment can increase prognosis significantly. This study looks into the serum biochemistry and lipid composition of serum and liver samples in a group of stray cats (N=18) collected from pounds in Klang Valley, Malaysia. Alanine aminotransferase (ALT) in blood serum was used to detect for liver damage possibly due to FHL, confirmed through light microscopy, serum biochemistry (triglyceride, cholesterol, creatinine, and urea), liver triglyceride and cholesterol concentrations, and liver RNA expression of lipid droplet regulators peroxisome proliferator-activated receptors (PPARs). Differing severity of FHL in samples were divided and grouped using an adapted scoring method observing fatty change of liver (FCL) with trends between FCL groups investigated. Elevated serum ALT reflective of increasing FCL severity was observed with elevated concentrations of liver TAG and cholesterol levels. Serum TAG and cholesterol decreased with heightened FCL pointing to fatty acid oxidation and lipid restoration in the liver, supported by PPAR-γ expression which also propose macrophage activation for liver recovery alongside PPAR-δ for lipogenesis and inflammatory reactions. Elevated serum creatinine and urea levels with increasing FCL severity propose overall intact hepatic function in the stray cat samples

Towards the conservation of Sungai Santi catchment: monitoring of land use and vegetation density of mangrove areas

This paper presents analyses of the land use and land cover change of the Sungai Santi catchment area. The purposes of this study were to delineate mangrove and other land use and land cover and to detect and develop land use masp in catchment aresa over the past 17 years. The NDVI method has been applied to observe the vegetation density of mangrove areas. Landsat TM and SPOT 5 imageries with a combination of ERDAS Imagine 8.4 and Arc View/Arc GIS software were used to detect spatial and temporal changes in land use and vegetation density between the years 1991 and 2007. Sungai Santi catchment experienced multiple changes of land use of varying degrees in 1991 and 2007. Results showed that agricultural land of oil palm and mixed agriculture, water bodies, and forest increased in this area, compared to mangroves and urban areas which decreased by 15.8 % (350 ha) and 23.4 % (223.3 ha) respectively. A land use change matrix indicated that the reduction of mangrove areas was due to an increase in water bodies and forest areas. NDVI method indicated six vegetation density values and the most dominant value was (0.4 – 0.5) which recorded 989.9 ha in 1991 and 981 ha in 2007. Even though the NDVI change matrix depicted a significant transition of 144.1 ha display from (0.4 - 0.5) to (0.5 - 0.6) in 2007, there low vegetation density occurred near the main river. The results showed that on-going land use change and deforestation of mangrove areas can be controlled through strict management of land conversion, and as for the mangrove forest, it has to be through total protection by law. This goal can be achieved by improving the Permanent Forest Reserve law and commitment to adopting a sustainable resource polic

Simulation and model verification of a vehicle handling dynamics

The purpose of this study is to model, simulate and verify the entire vehicle handling dynamics of UNS Electric vehicle (Semar-T) using Matlab-Simulink. The modeling of Semar-T electric vehicle begins from the derivation equation of motion and Dugoff tire model. The equations are derived using Second Newton's Law and then simulated in Matlab-Simulink environment. Five handling condition tests are performed for exploring the handling performance namely step steer test, double-lane change test, slalom test, sudden braking test and sudden acceleration test. The disturbances input come from the lateral and longitudinal direction. Disturbance in the lateral direction is steer input while disturbances in the longitudinal direction are braking and throttling. The steering, braking and throttling input in this study is taken from the verification software namely CarSimEd. The results of the validation show that the vehicle model is valid based on verification using CarSimEd with the error magnitude between 5-15 % Therefore, the results of simulation from Matlab-Simulink can be applied to studies the behavior handling dynamics of Semar-T electric vehicle

Modelling and validation of the vehicle longitudinal model

This paper presents the detailed derivation and validation of a full vehicle model to study the behaviour of vehicle dynamics in the longitudinal direction. The model consists of handling and tyre subsystems, an engine model subsystem, an automatic transmission subsystem and a brake model subsystem. The full vehicle model was then validated using an instrumented experimental vehicle based on the driver input from brake and throttle pedals. Vehicle transient handling dynamic tests known as sudden braking tests were performed for the purpose of validation. Several behaviours of the vehicle dynamics were observed during braking and throttling manoeuvres, such as body longitudinal velocity, wheel linear velocity and tyre longitudinal slip, at each quarter of the vehicle. Comparisons of the experimental results and model responses with sudden braking and throttling imposed motions were made in this study. It is concluded that the trends between simulation results and experimental data were found to be almost similar with an acceptable level of error for the application at han