It is genrally known that tracked vehicles are exposed to severe working environments such as rough road and complex ride behaviors. Therefore, high performance suspension units are required to isolate the vehicle body from terrain induced vibrations. This paper presents a novel type of suspension units utilizing an electro-rheological (ER) fluid. An in-arm type of ER suspension units (ERSU) is modeled and its spring and damping characteristics are analyzed with respect to the intensity of the electric field. Subsequently, a 16 degree-of-freedom model for a tracked vehicle is adopted and aneuro-fuzzy skyhook controller is designed for the semi-active ERSU. In the control algorithm, the vertical speed of the body and the rotational angular speed of the wheel are used as fuzzy variables. Vibration control performances of the tracked vehicle subjected to bump and random excitations are evlauated in both the time and frequency domains. In addition, the mobility of the vehicle with the limited power absorption is investigated with respect to the road roughness.
KEYWORDS: Control systems, Roads, Feedback control, Computer simulations, Manufacturing, Vibration isolation, Digital signal processing, Design for manufacturability, Vibration control, Actuators
This paper presents a robust feedback control performance of a full-car suspension system featuring electro-rheological (ER) dampers for a passenger vehicle. The field-dependent yield stress of an ER fluid is obtained using a couette type electroviscometer, and a cylindrical ER damper is designed and manufactured by incorporating the yield stress of the ER fluid. A full-car suspension system installed with four independent ER dampers is then constructed and its governing equation of motion which includes vertical, pitch and roll motions is derived. A sliding mode controller which has inherent robustness against parameter uncertainties is then formulated by taking account of mass uncertainty. Control characteristics for vibration suppression of the ER suspension system are evaluated under various road conditions through the hardware-in-the-loop simulation for the demonstration of its practical feasibility.
Consideration of the radiative transfer through the atmosphere is essential for the quantitative analysis of the satellite- sensed data. To solve the radiative transfer equation directly, a detailed information about atmospheric radiation- related parameters, such as atmospheric soundings, atmospheric aerosol characteristics are required. This study presents a simple method to extract atmospheric aerosol radiative characteristics for LOWTRAN7 simulation of short wave radiation. Atmospheric aerosol radiative characteristics are obtained mainly from observed column optical depth with the statistical data of Spinhirne's atmospheric model of aerosol scattering coefficient and d'Almeida's atmospheric aerosol radiative characteristics. Also, to examine the application of this method, the results simulated by LOWTRAN7 with atmospheric aerosol radiative data are compared with CAGEX (CERES/ARM/GEWEX Experiment) data as ground-truth radiative measurements. Standard errors of LOWTRAN7's results with respect to CAGEX data were 1.9% (downward direct flux at the surface), 6.9% (downward diffuse flux at the surface). It is shown in the results that a large part of error in LOWTRAN7 flux simulation is found in the diffuse component due to scattering mainly by atmospheric aerosol. In a conclusion, better information about the radiative characteristics of atmospheric aerosols is required for improving the accuracy of radiative transfer simulation by model.
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