Qijun Xiao

The development of micro-gyroscope technology

This review reports an overview and development of micro-gyroscope. The review first presents different types of micro-gyroscopes. Micro-gyroscopes in this review are categorized into Coriolis gyroscope, levitated rotor gyroscope, Sagnac gyroscope, nuclear magnetic resonance (NMR) gyroscope according to the working principle. Different principles, structures, materials, fabrications and control technologies of micro-gyroscopes are analyzed. This review compares different classes of gyroscopes in the aspects such as fabrication method, detection axis, materials, size and so on. Finally, the review evaluates the key technologies on how to improve the precision and anti-jamming ability and to extend the available applications of the gyroscopes in the market and patents as well.

Vibration analysis of a piezoelectric micromachined modal gyroscope (PMMG)

Piezoelectric micromachined modal gyroscope (PMMG) is a novel kind of rotating rate sensor, which is based on the special thickness-shear vibrating mode of a piezoelectric body. Compared with the general vibratory micro-gyro, the PMMG has no evident mass-spring component in its structure, so it has larger stiffness and robust resistance to shake and strike. Therefore, the PMMG can be used in the high-g environment especially, such as the fuse of smart munitions. In this paper, first, the working mechanism of the PMMG is proposed. Then, two kinds of models of the PMMG are introduced, one of which is the piezoelectric rectangular parallelepiped with driving electrodes or sensing electrodes on the top and bottom surface of the body (model 1), and the other is the piezoelectric rectangular parallelepiped with concentrated masses at four corners of the top and bottom surface of the body (model 2). For the two kinds of models, the modal and harmonic analyses are conducted, and the working mode of the PMMG is obtained based on the finite element method (FEM) analysis results. It is found that for model 2 the resonance frequency of working mode is lower than that of model 1 and the vibration directivity is improved. The fabrication processes and the controlling circuits of the PMMG are detailed in this paper. The PMMG prototype test validated the results of vibration analysis of the PMMG. The introduction of concentrated masses can lower the resonance frequency and improve the vibration directivity of the working mode of the PMMG. The work in this paper provides the theoretical and experimental foundation for realizing this novel kind of micromachined gyroscope.

Simulation of levitation control for a micromachined electrostatically levitated gyroscope

An electrostatically levitated gyroscope based on UV-LIGA fabrication process is introduced. The stable levitation is vitally important for the gyroscope to work efficiently. Two types of levitation control model of such a device are presented to realize initial levitation. The axial squeeze film damping coefficient is calculated by finite element analysis and deduced by analytical solution. From the analysis of the proportional integral differential (PID) control completed by the bias and the feedback linearization control (FLC) without bias. It can be seen that the PID control with the bias can linearize the control equation near the null position and FLC can realize the large travel with desired dynamic performance and global stability. But it has steady-state error, which can be switched to the PID controller to minimize. At last, the levitation control system is constructed.

Virtual prototyping simulation for electrostatically suspended rotor micro gyroscope initial levitation

We use virtual prototyping technique to develop a 3D model for electrostatically suspended rotor micro gyroscope system according to its actual mechanical structure and material properties. System level dynamic simulation results obtained from the established virtual prototyping model provide necessary reference and guidance for micro gyroscope system control. Various PID control methods used to realize rotor initial levitation with different control parameters are evaluated and validated by the analytical model before application. The output motion characteristic curves including force, velocity and displacement of rotor are analyzed. Based on simulation results, we find suitable strategy to realize rotor levitation and obtain superior motion performance. The displacement of rotor in Z direction measured in real working environment shows that the PID control method verified by the virtual prototyping simulation is workable. Rapid initial levitation of rotor provides prerequisite for the follow-up rotating and torque exerting control.

System-level simulation of a micromachined electrostatically suspended gyroscope

This paper presents modeling and system-level simulation of a micromachined electrostatically suspended gyroscope (MESG). The MESG reported here employs a spinning wheel-like rotor, which is suspended by electrostatic force without any mechanical support. With the precession of the rotor sensed capacitively, stator electrodes rebalance the rotor to its null position by an electrostatic feedback control system. This force-feedback system is constructed based on CoventorWare, with which MEMS devices develop faster, higher quality, lower cost and easier optimizing, using both bottom-up and top-down approaches. The former approach creates 3D solid gyro model according to its fabrication process, while the latter one is to combine behavioral models and IC components together, which two are complementary to each other.

Optimization design of an electrostatically suspended microgyroscope

A micromachined electrostatically suspended gyroscope (MESG), with a wheel-like rotor housed by stator electrodes, using LIGA-type microfabrication technology, was presented. Based on two capacitive detecting schemes, where common electrodes are used as signal pickoff and excitation, respectively, a unified multi-objective optimization design model of the structural parameters of the MESG is established. Employing goal attainment method, two optimization design examples using UV-LIGA and x-LIGA technology are given. An initial prototype of the designed microgyroscope was fabricated using UV-LIGA technology.

Single-neuron spinning control system for a non-silicon micromachined rotational gyro

We present here a single-neuron spinning control system (SSCS) for a novel non-silicon rotational MEMS gyro with an electrostatically levitated thick-film Ni rotor. The heavier Ni rotor can provide larger moment of inertia and higher spinning stability than its Si counterpart. With the SSCS, the deficiency of the nonlinear spinning dynamic nature of the gyro can be adaptively tackled. In addition, the SSCS is also able to produce continuously stable torque and keep the steady-state spinning speed robustly constant, which is important for performance improvement of the micromachined MEMS gyro. The SSCS is verified by co-simulations using both the Simulink models and the PSpice driving circuit models, which are joined by the SLPS™ software interface. The simulation results show that the SSCS can counteract the step disturbance torque 5e-10 N·m that is one order higher than the steady-state electrostatic driving torque, and almost no speed ripple occurs.

Structure mechanism of MEMS security stronglink with multi-try function

The MEMS security stronglink with multi-try function has been fabricated for some specified information fields. The structure, code and solidification are introduced. The stronglink consists of two groups of metal counter-meshing gears, two pawl/ratchet mechanisms, and two driving micromotors and two resetting micromotors, which could make the counter-meshing gears withdraw by raising the pawls. The counter-meshing gears are designed and solidified with the operating logic of code mechanism. It is fabricated using the UV-LiGA process and precision mechanical technique.