Bai Junjie

Spectral response of carbon nanotube-based device

Being direct band-gap materials, carbon nanotubes have a potential to be efficient spectrum detection material. By depositing the carbon nanotubes on the substrate surface using chemical vapor deposition growth methods, a carbon nanotube-based device is fabricated with micromachined techniques. The structure of the carbon nanotube-based device is characterized using scanning electron microscope image. The spectra of carbon nanotube-based device are measured. The photocurrent as a function of wavelength reveals a broad absorption at wavelength from 500 to 1000 nm, showing the potential application in wide-range spectrum detection.

High-order sliding mode control for a giant telescope

Astronomical telescopes become more and more huge, which lead its driving system to bear heavy nonlinear disturbances. The increased nonlinear disturbances especially caused by friction torque in the control system can easily bring tingle and stick-slip phenomena when the telescope tracks an object with an ultra-low velocity. However, the conventional control approaches are difficult to realize high-precision controls. A high-order sliding mode controller of order 3 was designed for a giant telescopepsilas driving system. High-frequency resonance is avoided because system dynamic which order below 3 is continuous. Computer simulation result shows that this approach can obtain high control precision and may satisfy the requirements of a giant telescope for ultra-low velocity.