Deep learning based intelligent fault detection for mechanical equipment has become an important research fields. However, due to various equipment and working conditions, it is difficult to collect sufficient fault samples by monitoring sensors, which restricts the accuracy of existing intelligent fault diagnostic approaches. In this paper, we propose a novel generative adversarial networks (GAN) based on local weights-shared multi-generator for the generation of fault data and building a fault diagnosis model. Unlike existing GAN based data augmentation methods, the proposed model contains multiple generators which are divided into several groups with each groups' prior layers of generators weights-shared. By adversarial training, the discriminator gradually improves the performance of judging authenticity and fault categories with each group of generators acquiring the ability to generate a type of fault data. In this way, the proposed local shared multiple-generator GAN method effectively reduces mode collapse and generates more diverse fault data. The performance of the proposed method was validated on the fault datasets that are not applied in training stage. Compared with traditional deep learning diagnosis methods, the accuracy of fault diagnosis could be improved up to 30%, which indicates that the data generation model can generate diverse data and expand the fault data space.

As an important form of ocean energy, wave energy is gradually being developed and utilized by coastal countries around the world. Researchers have developed various forms of wave energy conversion devices. In this paper, a new type of horizontal rotor wave energy power generation device is designed and manufactured. The device is in a moored floating state when working at sea. The heave belongs to the vertical movement up and down, which directly affects the stability of the device. Based on the engineering prototype making model and conducting regular wave experiments, four test conditions with the same period and different wave heights were designed to verify the influence of wave height changes on heave plates of different shapes and different installation distances on the stability of the device. Determining the shape of the heave plate and the optimal installation distance under the test conditions provides a theoretical basis for the manufacture of engineering prototypes and sea trials.

The development and utilization of wave energy is inseparable from the wave energy converter, and its stability is an important condition for operation. Heave is the biggest factor affecting the stable power generation of wave energy converters. The key method to solve this problem is to install a suitable heave plate. Therefore, the design of the heave plate is particularly important. Based on a new type of horizontal rotor wave energy converter, this paper proposes three different shapes of heave plate design schemes and completes the calculation and modeling of the engineering prototype. First, the three types of heave plate devices were numerically simulated using hydrodynamic calculation software to compare their stable performances and verify the feasibility of the scheme. Subsequently, an experimental model was made according to the parameters of the engineering prototype, and a tank experiment was carried out under the same working conditions to further study the influence of the heave plate installation distance on the stability of the wave energy generator. The results showed that when the distance was between 10 mm and 20 mm, the average amplitude change was large, and when the distance was between 20 mm and 30 mm, the average amplitude change was small. Therefore, the installation distance should be between 20 mm and 30 mm. In the case of the same heave plate area and installation distance, the average amplitude of the chamfered heave plate device was smaller than the other two types, indicating that its stability was better. The optimization of the shape and installation distance of the heave plate proposed in this study has obvious effects on improving the stability of the device and provides a reference for the design of the wave energy converter device.

For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the

In coastal sea areas with the bimodal Ochi—Hubble wave spectrum, such as parts of the China Sea and Indian Ocean, wave energy is the superposition of wind wave and swell. Traditional heaving buoy wave energy converters developed with narrowband wave spectrums suffer from big energy loss in these areas, leading to lower power absorption efficiency and higher generating costs. In contrast, multi-freedom buoy has different resonant frequencies and maximal power capture wave frequencies in different degrees of freedom (DOFs). Therefore, this study proposed using two DOFs to capture the energy of wind wave and swell correspondingly. A heave and pitch buoy model was established by potential flow theory and validated by experimental data. Coupling effect on the motion and power absorption, power capture frequency distribution and power absorption with different linear power takeoff system damping coefficients were analyzed to reveal the hydrodynamic response and the power performance of the two DOFs. The results indicate that by using heave and pitch DOFs, the wave energy components of wind wave and swell were captured in a targeted manner. It demonstrates that the 2-DOF buoy is an effective tool to avoid the energy loss and realize the efficient power absorption in coastal sea areas with bimodal Ochi—Hubble waves. © 2022, Chinese Ocean Engineering Society and Springer-Verlag GmbH Germany, part of Springer Nature.

Reliability and energy conversion ability are the most concerned performance indexes of Wave Energy Converter Eccentric Rotating Wave Energy Converter (ERWEC) with closed shell can protect energy conversion unit away from seawater, which has shown excellent reliability. However, energy conversion ability of Eccentric Rotating Wave Energy Converter is poor and the method to improve performance of ERWEC is still not clear. The objective of this work is to improve mooring security, motion attitude stability and energy conversion ability of ERWEC. In this paper, experimental model of ERWEC was developed, and energy conversion mechanism was clarified. Experiments on various mooring modes and various internal mass block layouts were carried out. Besides, breaking coefficient, instability coefficient and energy conversion coefficient were calculated to evaluate performance of ERWEC. The result showed that the effect of mooring mode on mooring security, motion attitude stability and energy conversion ability was coupled to the effect of internal mass block layout on those three indexes. Furthermore, under determined mooring mode condition, internal mass block layout was optimized by multi-objective genetic algorithm. This paper provides basis for conceptual design of mooring mode and real-time control of mass block layout to achieve better mooring security, motion attitude stability and energy conversion ability of ERWEC.

Oscillating buoy device, also known as point absorber, is an important wave energy converter (WEC) for wave energy development and utilization. The previous work primarily focused on the optimization of mechanical design, buoy's array configuration and the site selection with larger wave energy density in order to improve the wave energy generation performance. In this work, enlightened by the potential availability of Bragg reflection induced by multiple submerged breakwaters in nearshore areas, we investigate the energy conversion behavior of oscillating buoy devices under different wave types (traveling waves, partial and fully standing waves) by flume experiments. The localized partial standing wave field is generated by the Bragg resonance at the incident side of rippled bottoms. Furthermore, the fully standing wave field is generated by the wave reflection of vertical baffle installed in flume. Then the wave power generation performance is discussed under the conditions with the same wave height but different wave types. The experimental measurements show that the energy conversion performance of the oscillating buoy WEC could be improved under the condition of standing waves when compared with traveling waves. This work provides the experimental comparison evidence of wave energy conversion response of oscillating buoy devices between travelling waves and standing (fully or partial) wave conditions.

Intensive wave reflection occurs when the wavelengths of the incident waves and bottom undulations are in a 2:1 ratio. Existing studies have included the Bragg resonance phenomenon of waves passing over a continuous undulating bottom parallel to and oblique to the shoreline. More generally, the Bragg resonance mechanism is used as a means of coastal protection, rather than wave power generation. To focus the wave energy in a specific area, here, we propose sinusoidal sandbars of a horizontal V-shaped pattern, which is formed by two continuous undulating bottoms inclined at an angle to each other and the center axis of the angle is perpendicular to the shoreline. Based on the high-order spectral (HOS) numerical model, both the characteristics of Bragg resonance induced by the regular waves and random waves are investigated. In the scenario of regular waves, it shows that the wave-focusing effect is related to the angle of the V-shaped undulating bottom, and the optimal angle of inclination for the V-shaped undulating bottom is 162.24 degrees. On that basis, considering the interactions between the random waves and the V-shaped undulating bottom of 162.24 degrees, the Bragg resonance characteristics of random waves are studied. The BFI factor combining wave steepness and spectrum width can evaluate the focusing intensity of the Bragg resonance of the random waves. For BFI, in the range of 0.15-1.0, the values of H-smax/H-s0 linearly increase with the increase of BFI.