Input Shaping Based on an Experimental Transfer Function for an Electrostatic Microscanner in a Quasistatic Mode

This paper describes an input shaping method based on an experimental transfer function to effectively obtain a desired scan output for an electrostatic microscanner driven in a quasistatic mode. This method features possible driving extended to a higher frequency, whereas the conventional control needs dynamic modeling and is still ineffective in mitigating harmonics, sub-resonances, and/or higher modes. The performance of the input shaping was experimentally evaluated in terms of the usable scan range (USR), and its application limits were examined with respect to the optical scan angle and frequency. The experimental results showed that the usable scan range is as wide as 96% for a total optical scan angle (total OSA) of up to 9° when the criterion for scan line error is 1.5%. The usable scan ranges were degraded for larger total optical scan angles because of the nonlinear electrostatic torque with respect to the driving voltage. The usable scan range was 90% or higher for most frequencies up to 160 Hz and was drastically decreased for the higher driving frequency because fewer harmonics are included in the input shaping process. Conclusively, the proposed method was experimentally confirmed to show good performance in view of its simplicity and its operable range, quantitatively compared with that of the conventional control.

The BIPM measurements of the Newtonian constant of gravitation, G

This paper is a complement to the two short papers published in 2001 and 2013 in which we presented the results of the two BIPM determinations of the Newtonian constant of gravitation G . While this review contains no new results, it includes more detailed descriptions of certain key parameters that enter into the determination of G . Following a description of the overall method and the two versions of the experiment, we discuss the properties of the torsion strip, including the effects of anelasticity, then the electrostatic torque transducer, the source and test masses, dimensional metrology, angle measurement, the calculation and measurement of the moment of inertia, calculation of the torque, possible magnetic interactions and finally we discuss uncertainties and correlations in the derivation of a value for G .

Modeling and Analysis of a MEMS-Based Thermal Emissivity Variable Thermal Control Device

The study was made on a MEMS-based thermal emissivity variable micro-thermal control device to meet the requirements of the thermal control system of the spacecraft. An emissivity adjustment model for louvers was established. Main parameters that influence the equivalent emissivity of the louver were also investigated. Characteristics such as the electrostatic torque driven by parallel electrodes were modeled and analyzed. As a result, curves of the relationship between angles driven by parallel electrodes and electrostatic torques were obtained. Based on theoretical analysis, the adjustment range of the thermal emissivity was obtained for torsional micro-thermal control devices. The results showed that the properties meet the requirements for the control of space thermal emissivity.

A Compact, Easily Assembled Micromirror With Liquid Metal Pivot

We have developed a new approach to achieve a high-speed micromirror, which can rapidly tilt large angles with a low voltage and a compact footprint. In our approach we use a liquid metal drop with a low vapor pressure as the pivot, and the micromirror is tilted by an electrostatic torque. Micromirrors (1 mm x 1 mm) and the actuating circuit are microfabricated with a centralized wetting area surrounded by a non-wetting Parylene area to confine the drop. The frequency response curve shows that the mirror has 78V snap-down voltage and resonant frequency at 165Hz, and has a potential resonant frequency more than 3k Hz if the size of the mirror and liquid metal pivot is reduced. A micromirror with a liquid metal pivot is expected to have significantly higher reliability since a liquid drop does not suffer from mechanical fatigue. Due to the single point support, the micromirror can be tilted in an arbitrary direction, and the fabrication process is simpler than those required to create solid torsional weak links.