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A novel piezoelectric inchworm actuator driven by one channel dc signal is developed in this article to simplify excitation signal of the inchworm actuators, and the clamping force of the developed actuator is generated by a dc motor and two permanent magnets. The piezoelectric stack is excited by a sensing signal, which is generated by the separate photoelectric sensor to detect the position of the rotational permanent magnets. A mathematical model is established to predict the motion of the slider. The prototype of the proposed piezoelectric actuator is fabricated, and mechanical output performance is measured. At a voltage of 75 V and frequency of 3.2 Hz, the average output step is 0.241 μm under no-load conditions. The proposed inchworm actuator can be operated by just one channel dc signal and the output displacement is stable, which provides a new idea for the integration design of the piezoelectric actuators in the future. [ABSTRACT FROM AUTHOR]

A low-frequency structure-control-type inertial actuator using miniaturized bimorph piezoelectric vibrators is proposed in this paper to achieve high resolution and high stability with a large linear stroke. These vibrators are fabricated by bonding, thinning, and patterning fabrication processes, which are beneficial to realize miniaturization and increase output performance for the system. A theoretical model based on work-energy analysis is established to predict the output displacement characteristics. An experimental system is built to evaluate the performance of the proposed actuator. Experimental results indicate that the stable minimum step displacement is 0.03 μm under a square wave signal of 5 V, 50 Hz, and a clamping difference of 3.5 mm. Under the condition of 7 V and 50 Hz, the sample standard deviation is 0.0337 μm in repeatability test. The proposed actuator achieves a stable and accurate linear bidirectional motion with high resolution, high stability, low power consumption, and a large working stroke. [ABSTRACT FROM AUTHOR]

In multi-agent system (MAS), the communication topology of agent network plays a very important role in its collaboration. Small-world networks are the networks with high local clustering and small average path length, and the communication networks of MAS can be analyzed within the frame of small-world topology. Yet the real multiagent communication networks are abundant and the classical WS small-world model is not suitable for all cases. In this paper, two new small-world network models are presented. One is based on random graph substrate and local nodes preference reconnection and the other is based on regular graph substrate and long-range nodes preference reconnection. The characteristic of the network parameter such as the clustering coefficients, average path length, and eigenvalue λ2 and λn of the Laplacian matrix for these two models and WS model is studied. The consensus problem that based on these three models is also studied. An example is given and the conclusions are made in the end. [ABSTRACT FROM AUTHOR]

In this paper, we mainly investigate the character of consensus convergence speed of Multi-Agent Systems (MAS) with small-world communication network and the method of devising a speed-optimized small-world communication network in consensus problem based on genetic-algorithm (GA). It is found that, for a small-world communication network, the time to reach a consensus changes rapidly with the change of the number of long-range communication links and the agents which the long-range links connect. The convergence speed of consensus of MAS increases rapidly with the number of long-range links increasing. As we construct a small-world communication network for MAS with a smaller network size and fixed long-range links, we can optimize the long-range link configuration using GA methodology to obtain a small-world communication network with faster consensus speed for MAS. [ABSTRACT FROM AUTHOR]

To address the problems of existing 2D image-based imbalanced fault diagnosis methods for rolling bearings, which generate images with inadequate texture details and color degradation, this paper proposes a novel image enhancement model based on a dual-branch generative adversarial network (GAN) combining spatial and frequency domain information for an imbalanced fault diagnosis of rolling bearing. Firstly, the original vibration signals are converted into 2D time–frequency (TF) images by a continuous wavelet transform, and a dual-branch GAN model with a symmetric structure is constructed. One branch utilizes an auxiliary classification GAN (ACGAN) to process the spatial information of the TF images, while the other employs a GAN with a frequency generator and a frequency discriminator to handle the frequency information of the input images after a fast Fourier transform. Then, a shuffle attention (SA) module based on an attention mechanism is integrated into the proposed model to improve the network's expression ability and reduce the computational burden. Simultaneously, mean square error (MSE) is integrated into the loss functions of both generators to enhance the consistency of frequency information for the generated images. Additionally, a Wasserstein distance and gradient penalty are also incorporated into the losses of the two discriminators to prevent gradient vanishing and mode collapse. Under the supervision of the frequency WGAN-GP branch, an ACWGAN-GP can generate high-quality fault samples to balance the dataset. Finally, the balanced dataset is utilized to train the auxiliary classifier to achieve fault diagnosis. The effectiveness of the proposed method is validated by two rolling bearing datasets. When the imbalanced ratios of the four datasets are 0.5, 0.2, 0.1, and 0.05, respectively, their average classification accuracy reaches 99.35% on the CWRU bearing dataset. Meanwhile, the average classification accuracy reaches 96.62% on the MFS bearing dataset. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the stability of hydro-turbine governing system (HTGS) with sloping ceiling tailrace tunnel (SCTT) and upstream surge tank (UST) considering nonlinear hydro-turbine characteristics (NHTCs). Firstly, the mathematical model of HTGS is presented based on nonlinear seventh-order state equation, which is verified by example analysis so as to study the stability of HTGS. Subsequently, the effect of HTGS parameters on the stability of the system is investigated with numerical simulation. Finally, the coupling effect mechanism of SCTT and UST on stability under the effect of NHTCs is revealed by using contrastive analysis. The results are summarized as follows: (1) T a , K d and T wt perform larger effect on the stability of HTGS, while the influence of F and T wy is mild; (2) the NHTCs are beneficial under negative load disturbance and unfavorable under positive load disturbance for the stability and dynamic performance of HTGS; (3) the coupling effect of SCTT and UST outperforms the results of SCTT or UST alone under all load disturbances; (4) the incorporation of UST to the established model plays a certain role in stability compensation, while the introduction of SCTT not only improves the stability but also achieves smaller amplitude and lower frequency. [ABSTRACT FROM AUTHOR]

• The actuator with self-adapting excitation signal based on permanent magnets clamping structure is proposed to simplify the complex control systems of piezoelectric inchworm actuators. • The excitation signal generated by the OLS detecting the position of the permanent magnet is applied to one piezoelectric stack to achieve self-adapting driving. • The actuator using only one DC signal can achieve a stable linear motion, thus it provides a new idea for the integration of PIAs. A self-adapting structure is proposed in this study to match the driving and clamping signals of piezoelectric inchworm actuators. The excitation signal generated from a pair of opposite type laser photoelectric sensors which detect the positions of the permanent magnets. The proposed actuator can achieve stable motion by matching the clamping force controlled by rotating permanent magnets and the driving force generated by the piezoelectric stack. Simulation on magnetic flux density of the rotating permanent magnet and hysteresis characteristics of the flexible hinge with different thicknesses are conducted to optimize the structure parameters of the actuator. The dynamic model of the actuator is established and a series of experiments are carried out to evaluate the performance of the actuator in terms of resolution, maximum load, maximum output force and repeatability. The experimental results indicate that the actuator achieves maximum output force of 15 g, maximum load of 1100 g and resolution of 0.03 μm in the case of U = 150 V and f = 40 Hz respectively. Moreover, by comparing the theoretical and experimental results regarding the output displacement, it is found that they have the same movement trend. In conclusion, the self-adapting structure contributes to the easy integration of the piezoelectric inchworm actuator, which makes it rather promising considering the stable linear motion performance. [ABSTRACT FROM AUTHOR]

• The actuator is driven by the inertial impact forces generated by the clamping blocks with same size of different materials. • The actuator can solve the unstable motion of MCT caused by changing effective length of the vibrators during vibrating. • The relationship between the vibrator displacement and the elastic modulus difference of the clamping blocks are investigated. Asymmetric inertial piezoelectric actuators are driven by the inertial impact difference between the forward and backward cycle. Typical ways to create inertial impact difference involve the application of asymmetric driving signals and clamping blocks with different dimensions. A new asymmetric inertial piezoelectric actuator using clamping blocks with asymmetric materials is proposed in this study. The block materials have different elastic modulus, which generate different inertial impact forces to drive the actuator. The relationship between the vibrator displacement and the elastic modulus difference of the clamping blocks are investigated by comparison of the FEM and theoretical results. A series of experiments are conducted to prove the feasibility of the proposed actuator. The actuator with steel-copper clamping materials achieves more stable working performance compared with other clamping materials, the minimum step displacement, repeatability parameter reaches 2.0 μm, 0.566 μm and 15.7 μm, 4.805 μm in non-resonant and resonant states under the signal of V p-p = 15 V, respectively. The results show the proposed actuator works smoothly in both in non-resonant and resonant states, which provides a new reference for the application of inertial piezoelectric actuators. [ABSTRACT FROM AUTHOR]