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This paper reports the design, fabrication, and performance of a novel rotational energy harvester, utilizing multiple magnetic actuators and piezoelectric beams for the maximum performance in a wide range of rotational speeds. The harvester can be used in different rotational applications with low or high rotational speed and produce high output. Thin lead–zirconium–titanate (PZT) piezoelectric beams were fixed on the axis of a nonmoving wheel. One end of the beams was fixed to the center axis of the stationary wheel, while the other end hung free. Small magnets were bonded on each of the piezoelectric beams’ free ends and on a concentric wheel, fixed to a working shaft. As the working shaft drove the dynamic wheel, the magnets on the moving surface attracted the magnets on the piezoelectric beams, causing the beams to be plucked into vibration as the magnets passed by one another. The device was tested at six different rotational speeds from 180 to 500 r/min, with two different layouts, single and double plucking magnets. There will be potentials to increase up to six plucking magnets and four piezoelectric beams in this design for an increased performance. Voltage output versus time graphs were analyzed for each speed and setup. It was determined that increasing the number of plucking magnets and rotational speed was the most effective ways to increase the beam vibration and maximize the energy harvester’s performance. This is the most effective approach to increase the performance of the energy harvester in the applications that require lower speeds. The least effective case was the low speed, single magnet design, where the beam vibrated little and approximately half of the energy harvester’s time was idle time, minimizing the power harvested. [ABSTRACT FROM AUTHOR]

This paper presents the experimental observation results of contact-induced vibration (CIV) and its compensator design in dual-stage hard disk drive servo systems, where the vibration is caused by the continuous contact of read/write head and recording media. Consistent relationships between the center frequencies and magnitudes of the vibration modes and the tested fly height, rotation speed, and track position are clearly observed and analyzed. It reveals that the CIVs excite and amplify only the resonance modes of the system. In consequence, the so-called PQ method is adopted to perform the compensator design. As such, the relative contributions to system output from the voice coil motor and lead–zirconium–titanate actuator subsystems can be well assigned in the frequency domain. The remarkable performance of the well-designed compensator is demonstrated by simulation. [ABSTRACT FROM PUBLISHER]

Rotational speed is a key parameter for the condition monitoring and control of rotating machineries, such as generators, electromotors, and centrifugal and machine tool spindles. It is essential for precision machining and early warning of faults to measure rotational speed in real time. This paper presents the principle and application of electrostatic sensors and correlation signal processing techniques to real-time measurement of rotational speed. The electrostatic sensors and signal conditioning and processing units were designed and implemented. Experimental tests were conducted on a laboratory-scale test rig under a range of conditions including different diameters of the shaft. The results obtained suggest that the distance between the electrodes and the surface of the rotating object is a key factor affecting the performance of the measurement system. The system performs better in terms of accuracy and repeatability at a higher rotational speed (>1000~r/min) as more electrostatic charge is produced on the rotating surface. High and stable correlation coefficients acquired during the tests suggest that the measurement system is capable of providing reliable measurement of rotational speed under realistic industrial conditions. [ABSTRACT FROM PUBLISHER]