Beijing Jingshida Electromechanical Equipment Research Institute

High-entropy alloys (HEAs), exemplified by the AlCoCrFeNi system, have garnered significant interest in materials science owing to their superior mechanical properties, including exceptional strength and hardness, characteristics that render them particularly well suited for wear-resistant applications. Recent developments have demonstrated that the incorporation of ceramic reinforcement phases into AlCoCrFeNi-based matrices represents an effective strategy for enhancing tribological performance via composite coating architectures. This review offers a comprehensive examination of coating systems, including reinforcement phase selection criteria and matrix functionality. A systematic analysis of matrix-strengthening approaches is provided, elucidating fundamental mechanisms and detailing how variations in alloying elements drive microstructural evolution and consequent improvements in wear resistance. Particular attention is devoted to interfacial optimization, offering a detailed discussion of interface characteristics and optimization strategies achieved through adjustments in elemental composition. Finally, the present limitations of AlCoCrFeNi composite coatings are reviewed, and prospective research avenues are suggested.

Abstract This study proposes a radial basis function neural network disturbance observer- (RBFNNDO) based anti-saturation backstepping controller for hypersonic vehicles with input saturations and multiple disturbances. Firstly, in response to the problem of ‘exploding complexity’ in backstepping controller, we adopt finite-time tracking differentiators (FTD), which realise higher tracking accuracy and tracking speed than those of the existing methods. Secondly, we develop multivariable neural network disturbance observers to estimate the lumped disturbances involving aerodynamic uncertainties and external disturbances, thereby improving the robustness of the proposed controller. Thirdly, in order to alleviate the input saturation and minimise the duration time, we use an adaptive fixed-time anti-saturation compensator (AFAC). The simulation results have proven that our proposed backstepping controller outperforms other existing methods in terms of control performance and saturation time.

Abstract At present, bidirectional piezoelectric actuators (PAs) typically utilise multiple PZT stacks, which make the structure and driving principle complicated. In this work, a non-resonant PA with bidirectional motion using a single PZT stack is proposed. It incorporates a secondary displacement magnification mechanism, which improves the two driving feet’s output displacement. A lever reversing mechanism is designed to change the lever’s output direction, which in turn switches the driving direction of the driving feet, thus enabling the bidirectional drive. The PA’s working principle is described: an oblique linear trajectory is composed at the end of the driving foot, achieved bipedal alternating driving the guide rail. The PA model is analysed using finite element simulation to confirm the structure’s magnification ratio and the driving foot’s motion trajectory. Subsequently, an experimental assessment is performed on the PA prototype, confirming its capability to achieve bidirectional motion. Experimental findings demonstrate that the velocities of driving the guide rail leftward and rightward are 3.894 mm s −1 and 4.07 mm s −1 , respectively, under the conditions of 140 V and 40 Hz. This paper introduces a new idea on the compact structure design of a bidirectional-driven PA.