Dual three-phase permanent magnet synchronous motors (DTPMSM) are used in the steer-by-wire system of electric vehicles that require high reliability. Multiple faults should be considered for the steering system, such as open-circuit faults and speed sensor faults. However, the current speed sensorless control methods of the dual three-phase motor are mainly derived from the promotion of the three-phase motor. They fail when an open-circuit fault occurs, leading to the failure of fault-tolerant control. Researchers have noticed this problem and proposed many methods, but they are very complicated and computationally intensive. This paper proposes one type of improved model reference adaptive system (MRAS). By adding certain fault-related restraints to the output of the adjustable model, speed sensorless control can automatically fit the open-circuit fault and estimate accurately even if an open-circuit fault occurs, which makes sure the whole system continues to operate. Simulation results are presented that contain normal operation, open-circuit fault operation, fault-tolerant control operation, and the whole process from start to fault-tolerant operation. The results show that no matter what period the motor is in, the improved speed sensor can accurately estimate the motor speed and position. The improved model reference adaptive system is significant for improving the reliability of the motor steering system and ensuring the safety of people and property.

Micro cantilever probe of atomic force microscope (AFM) is a typical micro mechanical component, which is under a coupling deformation during the contact scanning process. Numerical simulations of micro scanning forces and micro topography are presented to investigate the influence of the coupling deformation of AFM probe under the AFM contact mode. It is demonstrated that the normal scan force is actually not constant, which is coupled with the lateral force on an asperity of sample surface, increasing together uphill and decreasing together downhill. The coupling relationship increases with the surface slope, tip height, etc. Coupling deformation of the probe proves to play a minor role on the AFM micro topography image and the perpendicular scan force. However, surface slope plays an important role on the variation of lateral force, and the peak positions of lateral force are not accordant with that of surface topography. These results are in good agreement with those previous AFM experiments.

Slip at the interface of solidified electrorheological （ER） fluid and electrodes is harmful for ER applications. Compression tests using four kinds of electrodes, namely the smooth, hole array patterned by laser pulse, nylon net covered, and acid etched column patterned electrodes, have been done, respectively. Results show that laser patterned and nylon net covered electrodes significantly enhanced the compressive stress of the ER fluid. The enhancement is ascribed to the increase of local electric field near electrodes after patterning, which increased the interfacial strength between ER fluid and electrodes, and effectively suppressed the slip of solidified ER fluid from electrode. The tests of current density during compression and the finite element analysis of the electric field distribution of patterned electrodes supported this slip suppression effect. The results raised a fundamental question of what is the real strength of ER fluids, since the slip of highly solidified ER fluid are usually not considered during various tests. This investigation also shows that patterning electrodes is a good way to improve mechanical performances of ER fluids.

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Measurement of wall shear stress (WSS) has important significance in many fields, such as spacecraft surface flow visualization and drag reduction of solid-liquid interface. Various measuring methods have been developed with the rapid development of micro and nano technology. This paper focuses on the measurement of WSS by using nematic liquid crystal coating. A quantitative model is built to describe the relationship between the variations of director orientation and the WSS based on the curvature elasticity theory of liquid crystal. Then an experiment setup is built to verify this model using 5 CB and 7 CB through the optical method. There is good consistence between the theoretical model and experiment results. Finally, the WSS measuring limits and influencing factors are discussed such as the thickness of the liquid crystal layer, the elastic coefficient of the molecule and measurement resolution.