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In this paper, we investigate the influence of warpage on the state estimation of the gyro-free IMU. A configuration-optimized gyro-free IMU is designed for investigation. Four triaxial MEMS accelerometers with specified configuration are used in order to directly determine the magnitude and sign of the angular velocity without integration. An optimized configuration geometry is presented to increase the observability of the body motion since the performance of the gyro-free IMU is affected by the configuration geometry of the distributed accelerometers. An effective unscented Kalman filter (UKF) is applied to estimate the system state. The mechatronic implementation of the distributed accelerometers consists of four triaxial MEMS accelerometers, each mounted on a separate board. The warpage model of the board based on thermal stress is built and developed. The main assumptions of this model are that the material of the board is FR4 which is widely used in Printed Circuit Board (PCB) and accelerometers are all rigid. Temperature is set within operating temperature ranging from −40°C to +85°C. We analyze the board warpage induced by thermal stress at −40°C, room temperature (+25°C) and +85°C. Then the position and sensing direction errors of each accelerometer are obtained from the simulation results respectively. Consequently, the board state is robustly estimated by the applied UKF. The results show that warpage induces errors to state estimation of a gyro-free IMU.

The process of dispensing gel above the silicon chip aimed at protecting chip surface and bonding wire is one of the most critical steps in the production of highly accurate low-pressure sensor modules. Numerous research efforts focused on the influences of dispensing process parameters, configuration and mechanical behavior of cured gel on the performance of sensors, while few concerns were taken on the air bubbles formed in cured gel induced by inappropriate technology control that adversely influence the zero offset in full temperature range and sensitivity. In this paper, the packaged modules of sensor chip attached on the ceramic substrate were chosen as the subject investigated, a series of hydrostatic fluid-element based 2D models in consideration of different positions and various diameters of air bubbles were conducted to explore this phenomenon. The simulation results showed that the inflation of bubble and elevated air pressure give rise to extra load on the sensing membrane, and this phenomenon becomes more evident as the initial distance between bubble and sensing element becomes shorter and the original diameter becomes larger. Even for the case of smallest diameter and farest distance, the maximum output variation could be 0.5% for a pressure point, this is still unacceptable for the production of high-precision and reliable low pressure sensors. So a vaccumizing process between the dispensing and curing processes could be preferred.

The thermal effect on performance of micromachined hemispherical vibratory gyroscope subjected to environment temperature change was investigated comprehensively in this paper. Firstly, the structure and principle of typical micromachined hemispherical gyroscope were introduced, and its advantages over other micromachined gyroscopes were demonstrated Taking a typical micromachined hemispherical gyroscope as a model, then, the analysis of modes was implemented under varying environment temperature ranging from −40°C to 120°C, and the relation between resonant frequency shift and temperature change was given based on the reference temperature of 20°C. The results showed that all order resonant frequencies decreased when environment temperature increased, and the high order frequency shifted more than the low order frequency. Finally, the reference state was chosen when the micromachined hemispherical gyroscope was driven at the driving resonant frequency and at room temperature of 20°C, and the sensing vibration amplitude presented the angular rate output. The sensing vibration amplitudes were calculated with the angular rate input from 0/s to π/s and environment temperature changing from −40°C to 120°C, and it concluded that temperature change can seriously degrade the angular rate output.

In this paper, simulation model for the response time of micro flow sensor using COMSOL Multiphysics is presented. The detailed structure of the micro flow sensor chip is considered in the simulation model. What's more, the temperature dependencies of physical properties of air are defined to improve the model precision. The model takes into consideration the transient conduction and convection between the sensor structure and fluid region. The effects of mass flow rate, thermistor position, input power and depth of flow channel on the response time of the micro flow sensor are investigated in detail. The effect of air relative humidity on the response time of the micro flow sensor is also studied. The results show the geometry parameters are the main factors that affect the response time.