A Two-Degree-Of-Freedom Time-Optimal Solution for Hard Disk Drive Servo Problems

This paper deals with the hard disk drive (HDD) servo problems. A novel discrete time-optimal control solution is proposed in a two-degree-of-freedom (2DOF) structure, employing both the feedback and feedforward controllers. The time-optimal feedback controller, derived from a simple, double integral plant model, shows remarkable robustness and disturbance rejection in the presence of resonant modes, measurement noises and position and torque disturbances. It eliminates the needs for two separate controllers for track-seeking and track-following operations. The proposed feedforward controller in this 2DOF structure proves to be quite beneficial in reducing the seek time. It also allows the feedback controller to be tuned more aggressively, which helps to improve the quality of track following. The proposed control scheme offers a novel basic control structure for HDD servo, upon which numerous further improvements can be made. It is successfully tested in simulation on an industrial 13.0-kTPI HDD

Microbial fuel cell analysis

Abstract only availableMicrobial Fuel Cells (MFC) are under vast considerations of use, by reason of the energy and economic "crisis" that faces many Western world citizens. MFCs have benefits over other renewable energy systems of creating at least two useful resources for human beings: electricity and sanitary water. However, MFCs are prone to hindrances including low voltage production and decreased efficiency due to fuel strangulation. This study tested the previously stated shortfalls. A fiberglass prototype MFC was used in conjunction with a 10-Amp resistor (i.e. light bulb) was used throughout the study. The prototype was injected with 2mL of anaerobic sludge in the cathode (negative) chamber and 2mL of aerobic sludge was transferred into the anode (positive) chamber. A 2.5mL sample of 600 parts/million chemical solution composed of a pre-mixed solution (300 parts/million), sodium acetate and distilled water (together, at 10,000 parts/million) was introduced to the cathode chamber and in following created .5mV circuit. All entry points were sealed with plastic film to force anaerobic reactions around the cathode. Voltage was measured throughout the day via voltmeter. As voltage flagged, a 10mL injection of extremely concentrated solution (2,240 parts/million) was created, inserted and mixed which made a 1,693 parts/million solution in the cell. Voltage immediately escalated to 1.1 mV and allowed for a rough conclusion that more extreme concentrations of solutions create higher voltage and efficiency. From these outcomes, the physical capacity of the prototype was found and a general understanding that a mass-marketed device similar to this would assist many in daily ventures.Emerge Summer Undergraduate Researc

Revealing A Head-on Major Merger in the Nearby NGC 6338 Group with Chandra and VLA observations

By analyzing the Chandra archival data of the nearby NGC 6338 galaxy group, we identify two X-ray bright clumps (N-clump and S-clump) within the central 100 kpc, and detect an arc-like X-ray brightness discontinuity at the south boundary of the N-clump, which is defined as a cold front with a gas flow Mach number of M<0.8. Furthermore, at the north-east boundary of the S-clump (dominated by galaxy NGC 6338) another X-ray edge is detected that corresponds to a weaker cold front. Therefore, the two clumps are approaching each other approximately from opposite directions, and the group is undergoing a head-on collision that is in a stage of pre-core passage. This merger scenario is also supported by the study of the line-of-sight velocity distribution of the group member galaxies. The merger mass ratio is about 1:1.8 as estimated from the central gas temperature of the two clumps, which suggests the merger is most likely to be a major merger. We also analyze the VLA 1.4 and 4.9 GHz radio data, but we do not detect any extended radio emission that is associated with the merger.Comment: Accepted by Ap