| Electrostatically levitated micro-gyroscope is one kind of MEMS devices composed of a flat rotor and some stator electrodes (including suspending, rotating and detecting electrodes). The micro-gyroscope based on two working ways, one is the high-precision spherical rotor supporting way, and the other is the disk-shaped rotor classical work way. Compared with the vibrating gyroscope, it has potential advantages of high accuracy. Besides, it can simultaneously measure two-axis angular rate, as well as three-axis acceleration. This kind of novel MEMS gyroscope has become the important direction for many micro-inertial sensors with high-precision, multi-axis integration, which shows broad application prospects.The key technologies of the electrostatically levitated micro-gyroscope include the simulation designing, micro-manufacturing, micro-rotor's displacement detecting, stably suspending control, constant-speed rotating and vacuum packaging technologies, and so on. In this paper, the Matlab simulation and experimental methods are combined to study the influence of different control algorithms (PID control algorithm and ahead - lag correction control algorithm) on the 5 degree of freedom (DOF) suspending control system of the electrostatically levitated micro-gyroscope. And its main contents and conclusions are shown as following:In the second chapter of this paper, the linear Reynolds equation is used to describe the squeeze film damping and the Couette equation is used for the sliding film damping, for the purpose of accurately deriving the air damping coefficients of the electrostatically levitated micro-gyroscope and providing some guidances for the 5-DOF levitating system modeling and theoretical study. The squeeze film damping coefficients at axial vibration, radial vibration and the sliding film damping coefficient at Z-axis rotation are derived respectively. Second, with Matlab simulation and design, the 5-DOF levitating system modeling based on the PID control algorithm and ahead—lag control algorithm has been built up from the aspects of stability, open-loop, closed-loop and bearing stiffness. Finally, the variable structure control algorithm--BangBang control algorithm combined with PID control algorithm, which is used to eliminate the non-linear performance in the process of suspending, is proposed.A new kind of DDS hardware circuit based on I/O expanding technologies has been designed to overcome the shortcoming of the AT89C51 micro-controller, whose I/O ports number is very limited. It mainly uses 2 pieces of "3-8 decoder-74LS138 chips" to extend I/O ports. The corresponding infinite-gain multiport feedback circuit (the MFB band-pass filter circuit) and the pre-amplifier circuit are designed to amplify the carrier signals and meet the experimental requirements.The corresponding software programs are needed in the process of designing the DDS signal generated circuits and signal processing. In the third chapter and sixth chapter of this paper, the software programs based on the assembly language are completed in Keil C software. Second, it gives out how to calculate control words of different kinds of carrier signals. The interface of the suspending control system has been made to display the 5-DOF displacement of the rotor in the process of suspending. Finally, the transmission of the alead-lag correction and PID correction parameters between the upper and lower computer are completed.Experimental results show that: under the digital PID control algorithm, the rotor can be accurately controlled with the single signal control; But when multiple signals simultaneously control, there is a certain bias between the actual measured displacement signals and the expecting equilibrium position because of the coupling. |
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