The development of an intelligent hybrid active-passive vibration isolator

A hybrid active-passive vibration isolator made up of electromagnetic actuator and air spring in parallel can be used to effectively isolate the broadband and line spectrum vibration of mechanical equipment simultaneously. However, due to its reliability and safety problems caused by the impact, its application in ships is limited. In this paper, an impactresistant structure and an air gap self-sensing method of the passive-active hybrid vibration isolator are proposed and developed on the base of modelling, simulation and analysis. A thin magnetic rubber is filled into the air gap of electromagnetic actuator, which can avoid rigid collision between the armature and the permanent magnet under the action of impact. A suspension armature structure including pre-compression spring is suggested, which can automatically compensate the deformation caused by impact and protect the coil and permanent magnet from impact damage. An air gap self-sensing method is developed through detecting the voltage between the input and output terminals of actuator, which is verified by experiments

A study on calculation method for mechanical impedance of air spring

This paper proposes an approximate analytic method of obtaining the mechanical impedance of air spring. The sound pressure distribution in cylindrical air spring is calculated based on the linear air wave theory. The influences of different boundary conditions on the acoustic pressure field distribution in cylindrical air spring are analysed. A 1-order ordinary differential matrix equation for the state vector of revolutionary shells under internal pressure is derived based on the non-moment theory of elastic thin shell. Referring to the transfer matrix method, a kind of expanded homogeneous capacity high precision integration method is introduced to solve the non-homogeneous matrix differential equation. Combined the solved stress field of shell with the calculated sound pressure field in air spring under the displacement harmonic excitation, the approximate analytical expression of the input and transfer mechanical impedance for the air spring can be achieved. The numerical simulation with the Comsol Multiphysics software verifies the correctness of theoretical analysis result

Theoretical investigation into tunable band gaps of an Euler-Bernoulli beam with 2DOF LR structures

This paper is concerned with an intelligent phonotic crystals (IPC) consisting of an Euler-Bernoulli beam attached with 2DOF locally resonant (LR) structures. The novel design of the dielectric electroactive polymer (DEAP) rings acting as the springs of oscillators is presented that could be employed to control the transmission of flexural waves on the beam. Tunable band gaps (BGs) can be realized by changing the stiffness of each oscillator driven by the external electric field, where the DEAPs transform electric energy directly into mechanical work under the applied voltage. Discrete copper (Cu) strips are then attached to the DEAP to allow the deformation of DEAP rings. The transfer matrix (TM) theory is adopted to assist readers to better understand the formation of the BG. Simulation results show that this particular configuration is effective for attenuating the flexural waves at low frequencies below 1000Hz where the tunable BGs may occur. Moreover, it is found that a wider BG can be achieved and shifts towards higher frequencies by increasing the applied voltages

Research on active control strategy of vibration in complex environment

FxLMS algorithm has been widely used in active vibration control field theoretically. This paper is aimed at the complex situations in actual environment including interference and occasional divergence due to algorithm. Firstly the effects to control process and result caused by those situations are analyzed, then select different means based on different characteristics of the effects to deal with them, and integrate all those means to derive a new optimal control strategy which is suitable to actual applications. The experiment shows that the improved control strategy can response effectively different occasional situations without any weakness of normal control, and it can promote the practical application ability of the algorithm and is able to adapt to complex environments in active vibration control

An application review of dielectric electroactive polymer actuators in acoustics and vibration control

Recent years have seen an increasing interest in the dielectric electroactive polymers (DEAPs) and their potential in actuator applications due to the large strain capabilities. This paper starts with an overview of some configurations of the DEAP actuators and follows with an in-depth literature and technical review of recent advances in the field with special considerations given to aspects pertaining to acoustics and vibration control. Significant research has shown that these smart actuators are promising replacement for many conventional actuators. The paper has been written with reference to a large number of published papers listed in the reference section

Research on the Friction Noise Generation Mechanism and Suppression Method of Submarine Rubber-Based Propeller Bearings—A Review

This article introduces the main mechanisms of friction noise generated by submarine rubber-based propeller bearings and analyzes their respective scope of application and limitations. Then, the research on suppressing friction noise through the optimization of the structure and improvement of materials of rubber-based propeller bearings is discussed. Finally, the article summarizes a promising research direction aimed at eliminating friction noise in submarine rubber-based propeller bearings. By improving the structure and materials, the friction noise of propeller bearings can be effectively suppressed, thereby improving the deterrence and stealth performance of submarines

Molecular Dynamics Simulation and Experimental Study of Friction and Wear Characteristics of Carbon Nanotube-Reinforced Nitrile Butadiene Rubber

Nitrile butadiene rubber (NBR) and its various composite materials are widely employed as friction materials in mechanical equipment. The use of carbon nanotube (CNT) reinforcement in NBR for improved friction and wear characteristics has become a major research focus. However, the mechanisms underlying the improvement in the friction and wear characteristics of NBR with different CNT contents remain insufficiently elucidated. Therefore, we conducted a combined analysis of NBR reinforced with varying CNT contents through molecular dynamics (MD) simulations and ring–block friction experiments. The aim is to analyze the extent to which CNTs enhance the water-lubricated friction and dry wear properties of NBR and explore the improvement mechanisms through molecular chain characteristics. The results of this study demonstrate that as the mass fraction of CNTs (0%, 1.25%, 2.5%, 5%) increases, the water-lubricated friction coefficient of NBR continuously decreases. Under water-lubricated conditions, CNTs improve the water storage capacity of the NBR surface and enhance lubrication efficiency. In the dry wear state, CNTs help reduce scratch depth and dry wear volume

Decoupled Planes’ Non-Singular Adaptive Integral Terminal Sliding Mode Trajectory Tracking Control for X-Rudder AUVs under Time-Varying Unknown Disturbances

This paper analyzes the trajectory tracking problem in decoupled planes for X-rudder AUVs under time-varying, unknown environmental interferences. The proposed scheme consists of the kinematic control law based on the compound line-of-sight guidance law and the dynamic control law based on a non-singular adaptive integral terminal sliding mode control (NAITSMC) to avoid the chattering problems, parameter perturbation, and time-varying disturbances. Meanwhile, we introduce a reduced-order extended state observer (RESO) to compensate for unknown ocean currents by the first-order Gauss–Markov process. We verify the whole system of the proposed scheme through global asymptotic stability, then present a set of numerical simulations revealing robustness and adaptability performances in decoupled planes