The low temperature coefficient and high linearity of the input-output characteristics are both required for high-performance microelectromechanical systems (MEMS) capacitive accelerometers. In this work, a structural designing of a bulk MEMS capacitive accelerometer is developed for both low temperature coefficient and high linearity. Firstly, the contrary effect of the wide-narrow gaps ratio (WNGR) on the temperature coefficient of the scale factor (TCSF) and linearity error is discussed. Secondly, the ability of an improved structure that can avoid the contrary effect is illustrated. The improved structure is proposed in our previous work for reducing the temperature coefficient of bias (TCB) and TCSF. Within the improved structure, both the TCSF and linearity error decrease with increasing WNGR. Then, the precise designing of the improved structure is developed for achieving lower TCB, TCSF, and linearity error. Finally, the precise structural designing is experimentally verified.

The Newton-Raphson (N-R) algorithm based on the sum of squared differences (SSD) function used in the digital image correlation (DIC) may obtain unreliable results in deformation measurements because light source variation is not taken into account. Here, a modified N-R algorithm that includes the effect of light source variations on the measurement results is presented. Instead of involving the mean value and square sum of the gray value of the object, variables were employed in the proposed algorithm. Thus, we refer to it as variables-based sum of squared differences (VSSD) function. VSSD has been validated by comparing the computer generated speckle images, which indicates that it could give rise to more accurate results in calculating deformation than SSD when the surrounding light source changes. In addition, VSSD is compared with the zero-normalized sum of squared differences (ZNSSD) function that is often used to remove the light source variation. The results show that VSSD can achieve the same accuracy within in less time compared to ZNSSD.

Micro-displacement detection plays a vital role in the position diagnosis and accurate calibration of MEMS actuators. An optical micro-displacement detector proposed in this paper integrated a vertical cavity surface emitting laser (VCSEL) and nine photodiodes (PDs) to detect the sub-micrometer translation and sub-degree rotation of the piezoelectric micro vibratory stage under the limited space. The highly accurate detection was mainly realized by PDs design and quality improvement. Nine PDs layout with high resolution optical sensors and corresponding calculation guaranteed the detector to precisely acquire out-of-plane displacement and two axis rotation of vibratory platform. And the introduction of the light absorbing layer and the light shielding layer further improved the sensing quality to reach a higher measurement resolution. The micro stage was fabricated by MEMS technology and the experiments of measurement system indicated that the out-of-plane displacement detection accuracy was 150nm in the range of 500μm and the angle detection accuracy reached to 0.1° in the range of 2°.

The ultrasonic motors (USM) based on microelectromechanical systems (MEMS) technology utilize the inverse piezoelectric effects to drive the rotor through the friction force to realize the torque output. Therefore, the generation of a stable traveling wave within the stator is a key to USM performance, which heavily depends on the quality factor ( Q ) and the mode match level of a stator resonator. The current ring stators of micromotor exhibited an apparent mode mismatch and a relatively low Q value due to the displacement constraints and anchor loss of supporting beams. This article, through the modal analysis and energy dissipation evaluation of stators, proposes an elaborate design to improve the mode match and Q value by positioning the supporting beams at the saddle points of the B ₁₃ modal shape and introducing a buffering annular frame between beams and substrate. The designed stator has the natural frequency of 101.63 and 100.90 kHz and Q value of 89.5 obtained from the finite element method. And the prototype experiment shows the natural frequencies of two modes are 100.76 and 101.5 kHz, respectively, the maximum deflection of the stator under driving voltage of 0.5 and 1 V are 3.96 and 4.43 μ m, respectively, and the Q value is 84.58. Both the frequency and rotation tests indicate the proposed motor displays, a much higher Q , and extremely better mode match than current ones.

The traveling wave piezoelectric micromotor is driven by the resonant vibration of the stator through the friction force of contact surface. Therefore, the physical contacting behavior heavily determines the operation efficiency and stability of motors. Current studies on such a behavior mainly focusing on the motor structures with teeth on stator, cannot be utilized to investigate the driving mechanism of micro motors which have no teeth on any components. A new three-dimensional model in cylindrical coordinate system is proposed in this paper to study the actuation characteristics of the ultrasonic micromotor developed by MEMS technology. Both the radial variation and contact area change are considered in modeling the driving force of stator, and the relative velocity between contacting particles on stator and rotor are analyzed in detail to calculate the work done by the friction force. Finally, the micromotor working in B ₁₃ mode with a radius of only 2 mm is fabricated and tested. The experimental results show a great agreement with analytical analysis which exhibits a great significance to the performance optimization of micro motors.