Roundness is a kind of form error in geometrical measurement in laboratory and industry and contributes significantly to the uncertainty of the measurement instruments using precision spheres, especially microspheres. A new radius and roundness measurement method for microspheres is proposed in this paper. Using this method, not only can separate different run-out errors from the measuring results, but also can obtain the true radii in different directions of the tested microsphere, which are necessary for the roundness evaluation according to ISO 1101. A new roundness measurement system has also been developed, which is mainly composed of two miniaturized Michelson interferometer (MI) systems, two elastic mechanisms, and a precision rotating stage. Repeated measurements have been performed using a ruby microsphere manufactured by Renishaw Corporation as the reference, which has a claimed diameter and roundness of 700 μm and 130 nm respectively. Experimental results show that the average radius of the tested microsphere is 349.99 μm with a maximum error of 65 nm and an expanded uncertainty of 94.0 nm (k=2). The proposed method and system can be used in the precision contact measurements of parts with micro circular characteristics such as microspheres and micro cylinders.

The probe tip of a micro-coordinate Measuring Machine (micro-CMM) is a microsphere with a diameter of hundreds of microns, and its sphericity is generally controlled within tens to hundreds of nanometers. However, the accurate measurement of the microsphere morphology is difficult because of the small size and high precision requirement. In this study, a measurement method with two scanning probes is proposed to obtain dimensions including the diameter and sphericity of microsphere. A series of maximum cross-sectional profiles of the microsphere in different angular directions are scanned simultaneously and differently by the scanning probes. By integrating the data of these maximum profiles, the dimensions of the microsphere can be calculated. The scanning probe is fabricated by combining a quartz tuning fork and a tungsten tip, which have a fine vertical resolution at a sub-nano scale. A commercial ruby microsphere is measured with the proposed method. Experiments that involve the scanning of six section profiles are carried out to estimate the dimensions of the ruby microsphere. The repeatability error of one section profile is 15.1 nm, which indicates that the measurement system has favorable repeatability. The mainly errors in the measurement are eliminated. The measured diameter and roundness are all consistent with the size standard of the commercial microsphere. The measurement uncertainty is evaluated, and the measurement results show that the method can be used to measure the dimensions of microspheres effectively.

Laser beam drift greatly influences the accuracy of a four degrees of freedom (4-DOF) measurement system during the detection of machine tool errors, especially for long-distance measurement. A novel method was proposed using bellows to serve as a laser beam shield and air pumps to stabilize the refractive index of air. The inner diameter of the bellows and the control mode of the pumps were optimized through theoretical analysis and simulation. An experimental setup was established to verify the feasibility of the method under the temperature interference condition. The results indicated that the position stability of the laser beam spot can be improved by more than 79% under the action of pumping and inflating. The proposed scheme provides a cost-effective method to reduce the laser beam drift, which can be applied to improve the detection accuracy of a 4-DOF measurement system.

Piezoelectric ceramics have been widely used in ultra-precision displacement drive systems because of their excellent performance such as fast response and high positioning accuracy. However, its tracking control accuracy is limited by its inherent hysteresis nonlinearity. To date, the parameter identification of the hysteresis model that has been developed is complex. This situation has resulted in the difficulty for the model to be used in the real-time control system of piezoelectric ceramic actuators. This paper proposed a new mathematical model that can accurately describe hysteresis nonlinearity. The hysteresis main loop in the model is approximated using high-order rational fractions. The hysteresis segmentation model is completed through the recursive algorithm. Simulation and experimental results show that the hysteresis characteristic between the input voltages and output displacements have been clearly modeled. This segmentation modeling process is simple. In addition, the computation is low and accuracy is high. The model proposed in this paper can complete the modeling of complex hysteresis phenomena of the multi-degree-of- freedom micromotion stage with force-voltage coupling. Through a series of experiments to verify the effectiveness of the model in this paper, thereby laying the model foundation for the subsequent control of the piezoelectric ceramic actuator. This result also provides strong scientific basis for future research on the application of piezoelectric ceramic actuators in ultra- precision motion systems and further improves the positioning accuracy of the system.

High-Q micro-beam resonators have been widely applied in communication fields such as narrowband filters, but thermoelastic damping restricts the further improvement of quality factor. Traditional method such as overall size optimization used for thermoelastic quality factor (Q_TED) improvement will cause the resonant frequency of the resonator change greatly, which will not be allowed in narrowband filters. In this article, three slots are introduced into a beam resonator to greatly reduce the thermoelastic damping by rationally arranging the length ratio of the central slot and the side slot, while the resonant frequency is basically kept unchanged. The feasibility is verified by parametric finite element simulation method. The results indicate that without changing the overall size of the micro-beam resonator, the resonant frequency remains unchanged and the Q_TED of the resonator can be doubled over twice both in the isothermal region and adiabatic region by placing side slots of 10% and a central slot of 30%. The proposed thermoelastic damping suppression method shows potential applicability for MEMS resonators in high-order mode of vibration.

In dynamic plowing lithography, the sample surface is indented using a vibrating tip in tapping mode atomic force microscopy. During writing, the gap between the cantilever and the sample surface is very small, usually on the order of micrometers. High vibration frequency and small distance induce squeeze film air damping from the air in the gap. This damping can cause variations in the cantilever’s vibrating parameters and affect the accuracy of the nanoscale patterning depth. In this paper, squeeze film air damping was modeled and analyzed considering the inclined angle between the cantilever and the sample surface, and its effects on the resonant amplitude and damping coefficient of the cantilever were discussed. The squeeze film air damping in the approaching curve of cantilever was observed, and its effect on fabricating nanopatterns was discussed.