Micromirrors based on micro-electro-mechanical systems (MEMS) technology are widely employed in different areas, such as optical switching and medical scan imaging. As the key component of MEMS LiDAR, electromagnetic MEMS torsional micromirrors have the advantages of small size, a simple structure, and low energy consumption. However, MEMS micromirrors face severe disturbances due to vehicular vibrations in realistic use situations. The paper deals with the precise motion control of MEMS micromirrors, considering external vibration. A dynamic model of MEMS micromirrors, considering the coupling between vibration and torsion, is proposed. The coefficients in the dynamic model were identified using the experimental method. A feedforward sliding mode control method (FSMC) is proposed in this paper. By establishing the dynamic coupling model of electromagnetic MEMS torsional micromirrors, the proposed FSMC is evaluated considering external vibrations, and compared with conventional proportion-integral-derivative (PID) controls in terms of robustness and accuracy. The simulation experiment results indicate that the FSMC controller has certain advantages over a PID controller. This paper revealed the coupling dynamic of MEMS micromirrors, which could be used for a dynamic analysis and a control algorithm design for MEMS micromirrors.

Direct-drive motors (DDM) serve a vital role in reducing assemble complexity of mechatronics system and improve operation efficiency. However, design of DDM for washing machine is difficult, DDM needs to generate high torque at ultra-low-speed during rinse and reach high speed during dehydration, while keeping high efficiency. This paper puts forward a direct-drive switched reluctance motor (DDSRM) with reconfigurable drive topology for washing machine, the connections between pole windings in one phase of DDSRM can be reconfigured according to rotational speed. Three winding topologies are proposed in this paper, which leads to different speed range, efficiency and winding current. Topology switching mechanism are given, efficiency of DDSRM under different topologies are compared to find optimal speed to switch topology. A fast power loss calculation model is built to analyze the influence of turn-on and turn-off angles on DDSRM efficiency under different topologies, an online switching angles optimization method that matches topology switching strategy is proposed. A 24/16 3-phase out-rotor DDSRM was used in experiment to verify the effectiveness of topology switching strategy and switching angels optimization method, the results showed that the speed range of DDSRM is extended, efficiency of DDSRM over wild speed range can be significantly improved. The DDSRM with reconfigurable winding topology is of great value in promoting direct-drive technology for house-hold appliances, hydraulic system and aerospace actuators.

Flexible magnetic-field-based tactile sensors (FMFTS) have numerous advantages including low cost, ease of manufacture, simple wiring, high sensitivity, and so on. Flexible magnetic-field-based tactile sensors need to be calibrated before use to build accurate mapping between contact force and magnetic field intensity measured by magnetic sensors; however, when considering remanence inconsistency of magnetic source, each FMFTS needs to be calibrated independently to enhance accuracy, and the complex preparation prevents FMFTS from being used conveniently. A robust estimation method of contact force and location that can tolerate remanence inconsistency of magnetic source in FMFTS is proposed. Firstly, the position and orientation of magnetic source were tracked using the Levenberg–Marquart algorithm, and the tracking results were insensitive to the remanence of magnetic source with appropriate cost function. Secondly, the mapping between magnitude and location of contact force and position and orientation of magnetic source was built with calibration of one sensor; the mapping only depends on the structural response of flexible substrate, and thus can be extended to estimate external force and location for other sensors with the same structure. The proposed method was evaluated in both simulations and experiments, and the results confirm that the estimation of magnitude and location of external force for FMFTS with the same structure and different remanence could reach acceptable accuracy, depending on single calibration. The proposed method can be used to simplify the calibration procedure and remove the barrier for large-scale application of FMFTS and replacement of damaged FMFTS.

Harmonic magnetic gears (HMGs) have the advantage of lubrication‐free, high speed ratio and high torque density, which make it an attractive solution for safety critical applications. Due to eccentricity caused by machining and assembly, HMG suffers from dynamic eccentricity (DE) in operation, however, its effect on HMG performance is still unknown. Transmission characteristic of HMG under DE is studied. First, a magnetic equivalent circuit (MEC) model of HMG is proposed to build the magnetic coupling torque analytically, and the geometry of air gap is analysed parametrically to derive its equivalent reluctances. Flux density and coupling torque can be acquired by solving MEC equations. The accuracy of the MEC model is verified by finite element method. To study the transmission characteristic, an electromechanical coupling simulation framework for HMG is constructed, motion trajectories of rotors are investigated in case of DE, the output torque in locked‐rotor condition and speed response in continuous operation can be derived by simulation. It is found that torque ripples that have the same frequency with input rotor are induced by DE; the results are then verified in the experiment. This paper provides a theoretical guidance for the design and condition monitoring of HMG.

Aircraft brake discs undergo rapid temperature rises during braking, critically impacting safety, lifespan, and adjacent components. Therefore, it is particularly important to study the heat transfer mechanism during the braking process and predict the temperature distribution of the brake disc. To address challenges in experimental studies (e.g., high costs and extreme conditions), this study employs full-scale numerical simulations to investigate heat transfer behaviours in medium-sized passenger aircraft brake discs. In the numerical simulation process, a coupling model that comprehensively considers the friction heat generation of the brake disc, the solid heat transfer between the discs, and the heat dissipation of the outer surface of the disc and the surrounding air is constructed to accurately describe the heat transfer characteristics of the brake disc under dynamic conditions. The study shows that the surface temperature of the brake disc rises sharply during the braking process, resulting in a significant increase in the temperature gradient; at the same time, the surrounding air flow state significantly affects the heat dissipation efficiency of the brake disc and affects its temperature distribution. Finally, the effectiveness of the numerical simulation was verified by experiments, and the maximum relative error between the experimental results and the simulation results was about 4.5%. This study provides a research basis for optimizing the structural design of the brake disc, improving its heat dissipation performance and operating safety.