A SiO₂-Al₂O₃-B₂O₃-CaO-MgO-Na₂O glass-based protective lubricant coating was developed for Ti-6Al-4V alloy forging, featuring a fully non-toxic formulation. The coating consisted of a composite glass matrix formed by blending two phases with distinct softening temperatures, extending its operational window to 700–950 °C. The composite glass showed initial softening at 700 °C and complete melting at 800 °C, with contact angle measurements confirming superior wettability (θ < 90°) across the forging range (800~950 °C). With an increase in temperature, the surface tension of the composite glass melt decreased, and subsequently, the wettability of the composite glass melt was significantly improved. XRD revealed that the uncoated Ti-6Al-4V formed a 22 μm thick rutile TiO₂ scale with a porous structure and interfacial cracks, while the coated sample retained an amorphous glass layer with no TiO₂. Cross-sectional SEM showed a crack-free, poreless interface with strong metallurgical bonding, in contrast to the uncoated sample’s spalled oxide layer. EDS showed minimal oxygen diffusion of the glass coating into the substrate. Ring upsetting tests showed that the coating reduced friction from 0.5–0.7 to 0.3 (50–57% decrease). Collectively, the glass protective lubricant coating showed good performance in terms of protection and lubrication.

In order to improve the current dynamic performance of induction motor (IM) drive systems, an internal model current decoupling control strategy is proposed to suppress the stator’s internal coupling effect. First, the IM mathematical model in the complex frequency domain is established, and the expressions of the coupling terms are derived. Then, according to the zero-pole distribution diagram and Bode plots, the design details for the structure and parameters of the internal model controller are presented in a continuous domain, and the impact of stator inductance mismatch on decoupling performance is analyzed. In addition to considering sampling and control delays, the IM mathematical model is established in the discrete domain, and the principle of the controller parameter is presented. Finally, the experimental results prove that the proposed internal model current decoupling control strategy can effectively improve the dynamic performance of IMs. Compared with the traditional feedforward current decoupling control strategy, the proposed method has superior decoupling performance under the operating conditions of low switching frequency. At the same time, a better steady-state performance is obtained by the proposed internal model control strategy.

To eliminate the dependence of the induction motor (IM) flux-oriented control system on position sensors, IM sensorless control based on a full-order state observer is studied in this paper. First, according to the IM rotor flux linkage models of current and voltage, the speed of the full-order state observer for IM and the solution for the feedback matrix are designed. Then, to simplify the expression of the feedback matrix and improve the stability of the observer for high-speed operation, a novel solving method of the feedback matrix by left-shifting the poles of the observer is proposed, and the terms containing rotor speed are simplified. On this basis, a speed estimation method based on the current error and Lyapunov theory is proposed. For low-speed operation, the feedback matrix parameter design method is proposed based on the stability conditions of d–q axis current error model. Finally, the feasibility and effectiveness of the proposed full-order state observer are verified by simulation and experiment. Since the improved full-order state observer can provide accurate speed feedback and rotor flux position for flux-oriented vector control systems, the IM drive system exhibits good steady-state and dynamic performance.

The twin propeller system can be powered by a motor with dual-rotating rotors, which generally necessitates that both rotors run at the same speed to prevent rolling. The motor with dual-rotating rotors is popular for applications that benefit from high torque density and an axially compact form factor. In order to minimize the effects of load disturbances and internal parameter perturbations on the motor performance, this paper proposes a control strategy combining disturbance observer and sliding mode control (SMC) technologies to realize the purpose of both rotors rotating at the same speed. There are issues with the conventional proportional-integral (PI) control for load disturbances and motor parameter variations, whereas the SMC method has its invariant properties. Meanwhile, the system disturbances obtained by a disturbance observer are estimated to be used as feed-forward compensation for the SMC control in order to reduce the undesired chattering during the SMC control process. The validity and practicability of the control strategies proposed in this paper are demonstrated by both simulations and experiments.

In the design process of the existing Line-Start Permanent Magnet Synchronous Motor (LSPMSM), the method to achieve the optimum performance is complicated, and the problem of pull-in synchronization caused by large load inertia is not fully considered. The objective of this research is to introduce a multi-objective optimization technique with efficiency (Eff), power factor (PF), pull-in torque multiple and starting torque multiple as optimization objectives.The impact of parameters such as core length, air gap length, and magnet thickness on efficiency, power factor, pull-in torque, and starting torque are analyzed. To achieve the optimal design outcome, a surrogate model integrating Response Surface Methodology (RSM) and Finite Element Analysis (FEA) for LSPMSM has been developed.The initial scheme based on FEA is analyzed and compared with the optimal scheme in detail, and the prototype manufactured according to the optimal scheme is tested and verified. The results of the optimization analysis show that in the case of a large load inertia, the efficiency, power factor, starting torque multiple and pulse-in torque multiple of the new optimization scheme have all been improved, achieving the collaborative optimization of transient and steady-state performance. Moreover, the results derived from FEA exhibit a high degree of consistency with the experimental data, thereby validating the optimized motor’s superior performance in both transient response and steady-state operation.