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This paper addresses the problem of identifying a system of forces from vehicle crossing a guideway using only the vibration responses caused by the forces as the input without knowledge of the vehicle characteristics. The vehicle is modeled as a single axle and two-axle loads with fixed axle spacing moving on a simply supported beam with viscous damping. The equations of motion of the beam are obtained through modal coordinate transformation, and the resulting set of equations relating the Fourier transforms of the responses and the moving forces are converted into time domain by a new method proposed by the authors. Correctness of the identified forces are checked by the correlation between the measured responses and the responses reconstructed with the identified forces moving on the beam. Experimental result shows that the method is effective to give good correlation when both measured bending moment and acceleration are used, and it is faster and it gives more accurate estimate of the total mass of the vehicle than an existing method.

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As non-traditional applications of hard disk drives emerge, their mechanical robustness during the operating state is of greater concern. A procedure for simulating the shock responses of a disk-suspension-slider air bearing system is proposed in this paper. A finite element model of the system is developed and modified, and it is used to obtain the dynamic normal load and moments applied to the air bearing slider. The dynamic load and moments are then used as input data for the air bearing dynamic simulator to calculate the dynamic flying attitudes. We obtain not only the responses of the structural components, but also the responses of the air bearing slider. The procedure is convenient for practical application, because it separates the work into two essentially uncoupled steps. It is used to simulate the shock response of a drive. The system modeled is linear if the load dimple of the suspension maintains contact with the slider, but it is non-linear if the dimple separates due to a strong shock. The air bearing has different responses for upward and downward shocks. Slider-asperity contacts occur when a strong shock is applied. IntroductionThe interest in the effects of shock on hard disk drives has come into currency due to the increasingly hostile environments encountered in the usage of the portable computer. As non-traditional applications of hard disk drives emerge, their mechanical robustness under shock and other mechanical disturbances during different states is of greater concern. A typical example is a PC with a disk drive installed on high speed boats. Read/write operation of the drive is frequently aborted because of the shocks caused by wave actions. Normal drives cannot properly function in this kind of environment. The main effects of shock are malfunctions during the operating state, damage during initial assembly, testing, installation into the computer chassis, and all unfavorable situations caused by the final users. There are essentially three approaches for dealing with the shock problems. The first is to design a suitable isolation installation for the disk drives. The second is to design a robust servo control mechanism to prevent read/write error during the shock. The third is to design a robust mechanical system and slider/disk interface. We focus on the third approach. There have been several experimental and simulation studies [1-7] on shock response of the mechanical system and its effects on the head/disk interface. However, most of the published works [1-5] are limited to the non-operating state of the drives, and/or to the component level. As the flying height (FH) continues to decrease and more and stronger disturbances during the operating state are encountered, a better understanding of the effects of the disturbances on the slider/disk interface is required.Two published papers [6, 7] considered shock simulation of disk drives in the operating state. They used quite different approaches. Jiang et al.[6] focused on the rotating disk in their paper. The suspension and slider ...