Developed in this research is a control logic for the ARC (Active Roll Control) system that uses rotary-type hydraulic stabilizer actuators at the front and rear axles. The hydraulic components of the system were modeled in detail using AMESim, and a driving logic for the hydraulic circuit was constructed based upon the model. The performance of the driving logic was evaluated on a test bench, and it demonstrated good pressure tracking capability. The control logic was then designed with the target of reducing the roll motion of the vehicle during cornering. The control logic consists of two parts: a feedforward controller that generates anti-roll moments in response to the centrifugal force, and a feedback controller that generates anti-roll moments in order to make the roll angle to follow its target value. The developed ARC logic was evaluated on a test vehicle under various driving conditions including a slowly accelerated circular motion and a sinusoidal steering. Through the test, the ARC system demonstrated successful reduction of the roll motion under all conditions, and any discomfort due to the control delay was not observed even at a fast steering maneuver.
IntroductionChromium chalcogenide spinel MCr 2 X 4 (M = Fe, Co, Cu, Cd, X = S, Se) shows various magnetic propertie with M ions. CuCr 2 Se 4 and CdCr 2 Se 4 are known to show metallic conduction and large magneto-optical effect [1]. In addition to colossal magnetoresistane (CMR) effect, metal-insulator transition and structural phase transition appear in FeCr 2 S 4 [2], spin-frustration effects reveal in FeSc 2 S 4 and MnSc 2 S 4 [3]. These systems have been revisited relaxor ferroelectricity and colossal magnetocapactive effect [4]. These features were attributed to competition of isomorphic ions with the topological frustration, Jahn-Teller distortion, and geometric frustration of magnetic moment. Here, we report the magnetic properties of the FeCr 2 S 4 and FeIn 2 S 4 with special emphasis on cation ordering related to the quadrupole interactions. Experiments Syntheses of the FeCr 2 S 4 and FeIn 2 S 4 were accomplished by the solid state reaction of the highpurity elements Fe, Cr, In and S in an evacuated quartz tube. The crystal structure of the samples was examined using x-ray diffractometer (XRD) with Cu-K α radiation and analyzed by Rietveld refinement. The Mössbauer spectra were recorded using a conventional spectrometer of electromechanical type with a 57 Co source in a rhodium matrix. Results and discussions Fig.1 shows the x-ray diffraction refinements for the FeCr 2 S 4 and FeIn 2 S 4 samples at room temperature, respectively. The spectra shown in Fig. 1 demonstrate the absence of any impurity phases. The determined crystal symmetry of samples is a cubic spinel structure Fd3m. FeIn 2 S 4 is an inverse spinel, with In atoms occupying both tetrahedral (A) and octahedral (B) sites. On the other hand, FeCr 2 S 4 has a normal spinel with Fe atoms occupying A site and Cr atoms occupying B site. The determined lattice constant a 0 for FeCr 2 S 4 and FeIn 2 S 4 were a 0 =10.011 and a 0 =10.616 Å, respectively, since result might be the larger ionic radius for In ions than for Cr ions. In order to study microscopic interaction mechanism, the Mössbauer spectra of sulphur spinel FeCr 2 S 4 and FeIn 2 S 4 have been studied. Fig. 2 shows Mössbauer spectra for the FeCr 2 S 4 and FeIn 2 S 4 at 4.2 K and room temperature, respectively. The Néel temperatures were found to be 175 and 15 K for the FeCr 2 S 4 and FeIn 2 S 4 , respectively, by Mössbauer spectroscopy. It can be understood as the strength of inter-sublattice exchange interaction Fe 2+ (A)-S 2--Cr 3+ (B) is stronger than that of the intra-sublattice exchange interaction Fe 2+ (B)-S 2--Fe 2+ (B). The large asymmetrical line broadening of Mössbauer absorption lines is shown for the samples at 4.2 K. We note that the FeCr 2 S 4 shows a single line resonance spectrum with an isomer shift of 0.72 mm/s at room temperature, while FeIn 2 S 4 at room temperature has an isomer shift of 0.74 mm/s and a electric quadrupole splitting (∆E Q ) of 3.22 mm/s. The charge state of Fe ions is ferrous (Fe 2+ ) as characterized by isomer shift (δ) for the samples. We interpret th...
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