The weak-signal detection technologies based on stochastic resonance (SR) play important roles in the vibration-based health monitoring and fault diagnosis of rolling bearings, especially at their early-fault stage. Aiming at the parameter-fixed vibration signals in practical engineering, it is feasible to diagnose the potential rolling bearing faults through adaptively adjusting the SR system parameters, as well as other generalized parameters such as the amplitude-transformation coefficient and scale-transformation coefficient. However, extant adaptive adjustment methods focus on the system parameters, while the adjustments of other adjustable parameters have not been fully studied, thus limiting the detection performance of the adaptive SR method. In order to further enhance the detection performance of adaptive SR methods and extend their application in rolling bearing fault diagnosis, an adaptive multiparameter-adjusting SR (AMPASR) method for bistable systems based on particle swarm optimization (PSO) algorithm is proposed in this paper. This method can produce optimal SR output through adaptively adjusting multiparameters, thus realizing fault feature extraction and further fault diagnosis. Furthermore, the influence of algorithm parameters on the optimization results is discussed, and the optimization results of the Langevin system and the Duffing system are compared. Finally, we propose a weak-signal detection method based on the AMPASR of the Duffing system and employ three diagnosis examples involving inner ring fault, outer ring fault, and rolling element fault diagnoses to demonstrate its feasibility in rolling bearing fault diagnosis.
Rotational energy, which is abundant in our living and working environments, provides available sources for energy harvesting (EH) to support wireless sensors and wearable devices. In order to convert rotational energy into electrical one, a novel dielectric elastomer generator (DEG) with crank-connecting rod mechanisms is proposed and studied in this paper. The system structure is first introduced, and the system operation mechanism under rotations is elaborated with the system motion and energy harvesting processes being analyzed theoretically. Next, the theoretical analysis is verified experimentally by measuring the output voltages of a prototype of the proposed DEG system, thus making further numerical simulation results credible. Moreover, the system electrical responses under rotational excitation are presented through numerical simulations, and the influences of some key parameters, including the rotational velocity, the gear ratio, the system dimensional parameters and the initial angles, on the system EH performances are discussed. The simulated results show that the system EH performance can be enhanced by increasing the rotational velocity and gear ratio, and appropriately setting the system dimensional parameters and initial angles. This work also presents how to optimize the system parameters, thus providing some effective guidelines for the design and improvement of the proposed system in rotational EH. A further comparative study demonstrates the superiority of the proposed device in rotational EH.
The mechanical behavior of a circular dielectric elastomer membrane (DEM) under the contact of a rigid ball is studied in this paper. The out-of-plane deformation of the DEM is unfolded to an equivalent in-plane deformation, and the mechanical behavior is further studied through the Helmholtz free energy theory and the Gent model. The theoretical results obtained from the proposed analysis approach are validated through the out-of-plane deformation experiments, and the influence of the DEM's thickness on the mechanical behavior is revealed and explained. Furthermore, the influences of some key dimensional, dynamical and electrical parameters on the DEM's mechanical behavior are investigated and discussed. The research results are helpful for the system analysis of dielectric elastomer actuators and dielectric elastomer generators with out-of-plane deformations.
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