Friction Reduction for a Rotational Gyroscope with Mechanical Support by Fabrication of a Biomimetic Superhydrophobic Surface on a Ball-Disk Shaped Rotor and the Application of a Water Film Bearing

• Main Authors: Dianzhong Chen, Xiaowei Liu, Haifeng Zhang, Hai Li, Rui Weng, Ling Li, Zhongzhao Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2017-07-01
• Series: Micromachines
• Subjects: lotus leaf; superhydrophobic surface; ball-disk shaped rotor; water film bearing; rotational gyroscope
• Online Access: https://www.mdpi.com/2072-666X/8/7/223

Friction between contacting surfaces of metal materials restricts the application of mechanical support in the high-precision inertial device of a rotational gyroscope. Instead, a disk- or ring-shaped rotor is electrostatically or magnetically suspended. However, stability of the rotor suspension restricts further improvement of the measurement precision. In the developed rotational gyroscope, a stable mechanical rotor supporting scheme with low friction is achieved by fabrication of a superhydrophobic surface with similar nanostructures of the lotus leaf on the carbon steel ball of the ball-disk-shaped rotor and the addition of a water film between the rotor ball and bronze hemispherical supporting bowl, which forms a water film bearing. The special design of the ball-disk-shaped rotor makes it possible for the application of a low-friction water bearing in the gyroscope, with rotor tilting motion. With a superhydrophobic surface, friction is further decreased and the rated spinning speed increases 12.4%, resulting in approximately the same proportion of increase in the scale factor. Moreover, superhydrophobic surface reduces mechanical damping torque for precessional motion to one order smaller than electrostatic feedback torque. Thus, through close-loop control, stable damping characteristics for precessional motion are obtained. The gyroscope exhibits excellent performance with the parameters of the measurement range, scale factor, nonlinearity, resolution, bias stability, and dynamic setting time tested to be −30°/s to 30°/s, −0.0985 V/(°/s), 0.43%, 0.1°/s, 0.5°/h, 0.1 s, respectively.