Wenyuan Chen

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.

Development of a micromachined rotating gyroscope with electromagnetically levitated rotor

A micromachined rotating gyroscope with electromagnetically levitated rotor (MRGELR) is proposed. The working principle of the MRGELR is based on the momentum conservation of a frictionless levitated rotor. The levitation, stability and rotation are analyzed through finite element software. The choice of suitable sized coils and micro-rotor is important for the stable levitation of the micro-rotor. The fabrication process of the MRGELR is detailed based on MEMS technology. For a micro-rotor with a diameter of 2.2 mm and a thickness of 20 µm, a rotation speed of 800 rpm is obtained in atmosphere and 4000 rpm in a vacuum package. The test shows that except for air slip damping, electromagnetic damping is another important factor that resists further increasing of the rotation speed. A resolution of 3° s−1 is obtained in the experiment when the rotation speed is 4000 rpm.

Design of electrostatically levitated micromachined rotational gyroscope based on UV-LIGA technology

The prevailing micromachined vibratory gyroscope typically has a proof mass connected to the substrate by a mechanical suspension system, which makes it face a tough challenge to achieve tactical or inertial grade performance levels. With a levitated rotor as the proof mass, a micromachined rotational gyroscope will potentially have higher performance than vibratory gyroscope. Besides working as a moment rebalance dual-axis gyroscope, the micromachined rotational gyroscope based on a levitated rotor can simultaneously work as a force balance tri-axis accelerometer. Micromachined rotational gyroscope based on an electrostatically levitated silicon micromachined rotor has been notably developed. In this paper, factors in designing a rotational gyro/accelerometer based on an electrostatically levitated disc-like rotor, including gyroscopic action of micro rotor, methods of stable levitation, micro displacement detection and control, rotation drive and speed control, vacuum packaging and microfabrication, are comprehensively considered. Hence a design of rotational gyro/accelerometer with an electroforming nickel rotor employing low cost UV-LIGA technology is presented. In this design, a wheel-like flat rotor is proposed and its basic dimensions, diameter and thickness, are estimated according to the required loading capability. Finally, its micromachining methods based on UV-LIGA technology and assembly technology are discussed.

Compact H∞ robust rebalance loop controller design for a micromachined electrostatically suspended gyroscope

In this paper, we design a compact H(infinity) robust rebalance loop controller that is featured with comprehensive performance achievement and relatively easy practical implementation for a dual-axis micromachined rotational gyro. By incorporating the bilinear pole-shifting transform into the weighted multivariable mixed-sensitivity framework, the design procedure of the robust controller is able to allow for various realistic performance requirements in terms of steady-state error, dynamic response characteristics, disturbance rejection and robustness to parametric variations. In comparison with a conventional decentralized lead-lag controller, the H(infinity) robust controller, which is considered as an efficient substitute for the former, is thoroughly analyzed and simulationally validated under a set of realistic scenarios.

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micromachining fabrication of thin film electrodes and interconnections, integration fabrication of thick nickel structures about 500 μm using UV-LIGA by successful removal of SU-8 photoresist mold, DRIE of silicon proof mass in thickness of 450 μm, microassembly and solder bonding, were employed to fabricate this prototype microdevice. A levitation experiment system for the fabricated microaccelerometer chip is introduced, and levitation results show that fast initial levitation within 10 ms and stable full suspension of the proof mass have been successfully demonstrated.

Electroplated hard magnetic material and its application in microelectromechanical systems

We describe the preparation of CoNiMnP-based permanent-magnet material using several sulfate and chloride solutions. We studied eight samples, and all the samples show vertical magnetic anisotropy. Sample8, which was electroplated from a low-concentration chloride solution and under external magnetic field, demonstrates the best magnetic properties with coercivity 2632 Oe, remanence 0.20 T, and maximum magnetic energy 10.185 kJ/m/sup 3/. An array structure can avoid the stress between the electroplated layer and the seed layer. The electroplated Co/sub 0.8/Ni/sub 0.1174/Mn/sub 0.0062/P/sub 0.0762/ permanent magnet has potential for bidirectional actuators in micro-electromechanical systems.

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.

Modeling analysis of piezoelectric micromachined modal gyroscope (PMMG)

A novel kind of MEMS micro-gyroscope, piezoelectric micromachined modal gyroscope (PMMG), is introduced in the paper. PMMG works with the special vibratory mode of solid material, and it is a kind of solid-state micro-gyroscope, which is different from micromachined vibratory gyroscope. There is no moving part and suspended structure in PMMG, and it is robust for the higher resistance to shock and shake. PMMG has no special requirement on vacuum package, so it has higher stability and reliability. The working mechanism of PMMG is introduced in the paper. A model of PMMG with concentrated masses is proposed in the paper, and using finite element method (FEM), its modal and harmonic analysis are compared with the model without concentrated mass. The results show that the model with concentrated masses has lower modal frequency and larger vibratory amplitude. The Coriolis effect analysis of the two kinds of model shows that the model with concentrated mass is favorable to increase the sensitivity of PMMG. The work of the paper provides theory foundation for further research of PMMG.

A novel safety device with metal counter meshing gears discriminator directly driven by axial flux permanent magnet micromotors based on MEMS technology

In a novel safety device based on MEMS technology for high consequence systems, the discriminator consists of two groups of metal counter meshing gears and two pawl/ratchet wheel mechanisms. Each group of counter meshing gears is onepiece and driven directly by an axial flux permanent magnet micromotor respectively. The energy-coupling element is an optical shutter with two collimators and a coupler wheel. The safety devices probability is less than 1/106. It is fabricated by combination of an LiGA-like process and precision mechanical engineering. The device has simple structure, few dynamic problems, high strength and strong reliability.

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.