With the aim of suppressing large vibrations of flexible beams and ensuring stable operation of flexible beams, the vibration suppression structure coupled effects of linear springs and nonlinear magnetic forces is proposed. An experimental prototype is built to investigate influencing factors such as quality, stiffness coefficient, and spacing through experimental methods. Using the control variates, changes in amplitude, resonance frequency, and vibration waveform are analyzed, leading to the following conclusions: Under the influence of vibration absorber, the amplitude of flexible beams decreased from 114.29 mm to 12.21 mm due to energy consumption, realizing a maximum vibration suppression rate of 89.32%. By adjusting the experimental variables, the vibration suppression frequency range extended from 3.2 Hz to 5.3 Hz, broadening the effective operation range. The combined effect of linear springs and non-linear magnetic forces reduces the vibration amplitude of the flexible beam, prolongs its service life, and broadens the applicability of the structure across various low-frequency vibration environments.

Energy harvesting plays a pivotal role in enabling sustainable power supply for the Internet of Things and distributed sensor networks, particularly for low-power devices. Piezoelectric energy harvesters based on vortex-induced vibrations offer a promising solution for low-wind-speed applications, yet their performance is constrained by limited bandwidth and sensitivity to wind speed variations. This study addresses these limitations by proposing a novel multi-parameter adjustable piezoelectric energy harvester featuring an inclined cylindrical bluff body. By systematically tuning the inclination angle and installation position, the device achieves substantial performance improvements. Experimental results indicate that the optimized configuration yields a wider operational frequency band and enhanced energy conversion efficiency. Through the experimental results, we discovered the existence of the double-peak phenomenon and the plateau phenomenon. The voltage value of the second peak can reach up to 122.4% of the maximum voltage of the first peak. The duration of the maximum plateau phase can maintain between the wind speed of 2.3 m/s and 5.7 m/s.

Most of the realistic low-frequency vibrations in an ambient environment are random. Although white Gaussian noise is considered as a more accurate representation of ambient vibration than harmonic excitation, it is still interesting to explore the performance of the energy harvester subjected to a practical application, such as human motions. In this paper, a theoretical and experimental investigation of a dual-coupling beams energy harvester (DEH) is carried out under random excitation and human motion. The proposed DEH comprises two piezoelectric cantilever beams connected with a linear coupling spring. Numerical and experimental results verify that the proposed harvester has a larger output power compared to the traditional bistable energy harvester (BEH) and the linear energy harvester (LEH). When the power spectral density is 0.02 g2/Hz, the RMS power of the DEH with a spring stiffness of 57 N/m (in the monostable region) is increased by 71.2 % than its counterpart. In addition, when the coupling spring stiffness is 26 N/m (the DEH is in the bistable region), experimental results show that the RMS power of the DEH is increased by 525 %, 135.8 %, and 125.6 % at a human motion speed of 2, 4, and 6 km/h, compared to the traditional BEH and LEH.

Aiming at the problem of low conversion efficiency of piezoelectric harvesting energy system, this study proposes a self-powered-synchronous inversion and charge extraction (SP-SICE) circuit on the basis of synchronous inversion charge extraction (SICE) circuit. The output voltage of the SP-SICE circuit is 63.6% higher than that of the SICE circuit through simulation comparison, and the feasibility and correctness of the circuit are verified through comparison of experiment and simulation. To address the limited energy harvesting efficiency of a single piezoelectric element, in this study, multiple SP-SICE circuits are connected in series to obtain a multi-input self-powered synchronous inversion charge extraction (MSP-SICE) piezoelectric energy harvesting circuit for a multimodal piezoelectric energy trap. Both experimental and simulation results show that the output voltage of the MSP-SICE circuit is 172% of the output voltage of the SP-SICE circuit with the same input source.

Aiming to achieve higher energy output under wider bandwidth, a low frequency magnetic coupling bistable piezoelectric and electromagnetic energy harvester is proposed. Two opposite-polarity magnets are introduced into the M-shaped structure. The introduction of magnetic repulsion force can broaden energy harvesting bandwidth and break through the potential well with smaller external excitation. The primary variables are obtained by state equations. The dynamic response and energy harvesting characteristics are obtained by comparing further numerical analysis with experimental methods. Compared with the theoretical and experimental results, both magnetic repulsion and bistable M-shaped structure can effectively improve the energy harvesting characteristics and dynamic response. The maximum output power of piezoelectric and electromagnetic modules is 0.17 mW and 1.24 mW respectively. Due to the structure influence, the maximum bandwidth of energy harvesting increases by 35.71 % than the minimum, the average growth rate of piezoelectric output voltage can reach 0.42V/mm during disorder motion and intra-well motion, piezoelectric and electromagnetic power also increase by 57.57 % and 55.45 % respectively. which enhances environmental adaptability and has great potential for monitoring and energy harvesting in low-frequency vibration environments.

To broaden the operating bandwidth of the vibration energy harvester at low frequencies, this paper presents a cantilever beam piezoelectric energy harvester (PEH) based on the sloshing of a liquid-filled container. The harvester is designed to recover energy from the multi-order sloshing modes of the liquid in the container. A mathematical model of the coupled system comprising the liquid within the container and the PEH was established. Based on the fluid–structure interaction (FSI) theory, the coupling mechanism between the liquid natural sloshing frequency and the immersed natural frequency of the beam was revealed. Experimental validation shows that the resonance characteristics of the PEH are mainly dominated by the liquid antisymmetric sloshing mode. Through comparative experiments, the effect of liquid-filled container and cantilever beam parameters on the PEH’s peak output voltage and operating bandwidth was systematically analysed. The performance of the PEH was significantly improved when the first-order natural frequency of the partially immersed beam approached the liquid natural sloshing frequency, with the bandwidth coefficient increasing by nearly fourfold under this condition. This research provides new ideas for the design and optimisation of piezoelectric energy harvesters in liquid sloshing environments.

Lempel-Ziv (LZ) complexity has been widely applied in multiple fields, and there are numerous improvements in multiscale computation and encoding to enhance its ability to characterize signal changes. Based on the hierarchical analysis, this article proposes an improved LZ indicator based on multiscale decomposition and multiscale encoding, which is applied to the recognition of bearing failure severity. The signal is first decomposed into multiple scales through hierarchical analysis. Next, the decomposed node signal is further decomposed by coarse-grained methods. Then, the multiscale decomposed signal is further decomposed into low- and high-frequency components using hierarchical analysis and the multiscale encoding is performed based on the decomposed low- and high-frequency components. Finally, the LZ complexity is calculated based on multiscale encoding. The effectiveness of the proposed method is validated by three single-point bearing fault datasets with different failure severity. The proposed method can achieve a classification accuracy of over 97%. The proposed method can be effectively applied to classify the bearing failure severity.

This paper proposes an omnidirectional piezoelectric energy harvester coupling vortex-induced vibration and wake galloping (OPEH-VW), converting wind energy into electrical energy. The vibration behavior of the OPEH-VW is explored by changing the spacing ratio (L/D) and the diameter of the wind cylinder at the end of the cantilever beam. When the wind does not blow directly onto the device, it will rotate due to the imbalance of forces on both sides of wind cylinder B until reaching a state of equilibrium, causing the device to stop rotating, achieving omnidirectional functionality. And at this state, the efficiency of wind energy collection is highest. The results show that when the two wind cylinders of the same diameter were placed in series, at low wind speeds, vortex-induced vibration (VIV) was observed. As wind speed increases, continuous VIV and wake galloping (WG) phenomena appeared at a spacing ratio of 3.5, while only WG was occurred at the other three spacing ratios. And if the two wind cylinders placed in series replaced to different diameters, the OPEH-VW behaved as a bi-stable system with two resonance frequencies. The output power increased with the wind speed within a certain range and raised to peaks twice.

When planetary rovers traverse across extensive megaripple deposits, some planetary rover's wheels climbing up a slope will experience longitudinal slip, while others moving down a slope simultaneously will suffer longitudinal skid. It is important to establish a unified model of longitudinal slip and longitudinal skid for online control optimization and terrain mechanical parameters estimation. However, when the wheel running state changes from longitudinal skid to longitudinal slip, the equivalent shear deformation modulus of a same terrain estimated using traditional terramechanics models is different, while the estimated modified sinkage exponent of a same terrain suffers an unexpected break. It is difficult to establish a unified model with traditional terramechanics theories. A unified model without slip ratio for smooth wheels was first established using a switching function, and named as smooth unified model. The relative error of the drawbar pull estimated using the smooth unified model is less than 19.7 % compared with the experimental data. And a unified terramechanics model without slip ratio for grouser wheels was established by introducing the grouser effect coefficient and equivalent radius to the smooth unified model, and named as grouser unified model. The equivalent terrain mechanical parameters estimated using the grouser unified model change continuously without break, and the relative error of the estimated drawbar pull can be captured within 22.37 % compared with the experimental data. Finally, field experiments were conducted to validate the performance of the grouser unified model.

To address the narrow working bandwidth issue of traditional cantilever piezoelectric energy harvesters, this study proposes a variable-section multimodal circular array piezoelectric energy harvester structure. By theoretically deriving the strain expressions of rectangular, trapezoidal, and parabolic piezoelectric cantilevers, establishing the electromechanical coupling state equation using MATLAB, and combining COMSOL for finite element simulation, the effects of geometric parameters and external excitation on energy harvesting characteristics are analyzed. A test system is built to compare the output performance of different cross-section vibrators in single and array modes. The results show that the variable-section design can effectively adjust the natural frequency, and the circular array achieves multimodal coupling, expanding the working bandwidth to 7-12 Hz and increasing the output power compared with a single vibrator. The high consistency between experiments and simulations verifies the correctness of the model, providing a theoretical basis for the design of broadband piezoelectric energy harvesters.

To improve the energy harvesting efficiency in a low frequency environment, a low frequency hinge beam bistable piezoelectric-electromagnetic composite energy harvester is proposed. The power generation performance of the energy harvester is analyzed by establishing a mathematical model of the energy harvester and combining numerical simulation and experimental verification. The results show that the optimal resistances of the piezoelectric and electromagnetic parts of the energy harvester are 300 k Omega and 100 Omega respectively; the length of connecting rod, parameter b, the number of turns of the coil, and the excitation acceleration have significant effects on the energy harvesting efficiency, in which the maximum output voltages of the piezoelectric part and the electromagnetic part reach 7.47 V and 0.36 V, which are improved by 66.7% and 121.8% respectively, and the low frequency energy harvesting efficiency is increased. The experimental results are in good agreement with the simulation results, and the relative errors of the peak voltages of the piezoelectric and electromagnetic parts are minimized to 0.19% and 0.44%, respectively, which verifies the reliability of the theoretical model. The energy harvester provides an environmentally sustainable way of powering microelectronic devices, which has a wide range of applications and important research significance.

The limitations of traditional fossil fuels have prompted researchers to develop new renewable energy technologies. Raindrop impact energy has become a research hotspot in the field of energy harvesting due to its wide distribution and renewability, especially in the self-energy supply of microrobots. The energy harvester is installed on the robot, utilizing piezoelectric-energy-harvesting technology to achieve self-energy supply for the robot, but the efficiency of existing raindrop energy harvesters is unsatisfactory. In order to better collect the impact energy of raindrops and broaden the application of piezoelectric energy harvesters in the field of autonomous energy supply of robots, inspired by the vibration generated by raindrop excitation of plant leaves in nature, a raindrop energy harvester for autonomous energy supply for robots was proposed through the bionic leaf design, a mathematical model was established for numerical simulation analysis, and the effects of excitation position, excitation height, petiole length and excitation rate on the output performance of the harvester were analyzed. Numerical simulation and experimental test results show that the piezoelectric energy harvester has a higher output at the excitation position at the tip. The higher the excitation height of the water droplet, the higher the output voltage. Increasing the length of the petiole can significantly improve its performance output, and at the same time, the raindrop excitation rate will also affect its output to a certain extent.

In view of the large disturbance caused by bi-directional fatigue loading and the large inertia of the blade leading to the difficulty of control and the failure of precision, a new electromagnetic compound excitation method for wind turbine blade biaxial fatigue test is proposed. According to the actual working conditions, the influence of electromagnetic mechanism parameters on the characteristic of excitation force are studied, and the mathematical model of electromagnetic fatigue loading system is established with solenoid type electromagnet as the loading device. The multi-stage electromagnetic excitation force is designed and the relationship between the electromagnetic force and the amplitude and frequency of the blade is obtained based on the law of conservation of energy. The magnetic field calculation model has been simulated in the ANSYS Maxwell to analyze the influence of electromagnet structural parameters on loading force and speed. Furthermore, the optimal selection range of coil turns, shape parameters, core length and outer diameter of the electromagnetic mechanism that meet the test requirements under the given blade specifications is obtained, which lays a theoretical foundation for the subsequent development of the electromagnetic fatigue loading test bench.

The efficiency of a single piezoelectric energy harvester (PEH) is inadequate to meet the energy requirements of equipment, requiring the simultaneous operation of multiple PEHs. Consequently, this work conducts research on multi-piezoelectric energy harvesters (MPEH) array based on wind-induced vibration. Analyze the output characteristics of array configurations using simulation and experimental methods, including dual parallel array (PEH-2p), dual series array (PEH-2s), four-square array (PEH-4), and nine-square array (PEH-9) energy harvesters. The results indicate that the spacing ratio (L/D) is the primary factor influencing the output performance of the PEH array. Both of the starting and peak wind speeds of PEH-2p were below the reference value, but the power peak has increased. The starting wind speed of PEH-2s has been reduced, with a more significant improvement in the output performance of the downstream energy harvester compared to the upstream energy harvester. The output power of the downstream energy harvester has increased by 323.35% in comparison to the reference value. Additionally, the PEH-4 demonstrates a boosting effect on the output power of both the upstream and downstream energy harvesters. The energy harvester in the center of the PEH-9 has the highest power peak, being 349.44% higher than the reference value.

This article proposes to improve the charge carrier transport efficiency in perovskite solar cells (PSCs) by adjusting the pore size of each mesoporous layer, so as to improve the performance of the device. The two-dimensional modeling of PSCs is carried out to clarify the relationship between the pore size of the mesoporous layer and the performance of PSCs. The simulation results show that the control of the pore size of the mesoporous layer can help to form a large potential difference and a deep potential well in the PSC and then improve the carrier transport in the PSC and the carrier collection in the PSC. When the pore size is 20 nm, the effect is the best, and the PSC performance is the best. This study provides theoretical and technical support for the research of mesoporous PSCs and promotes the basic research and commercialization of PSCs, which has important scientific significance and economic value.

This article proposes a low-frequency and efficient tension-like nonlinear piezoelectric energy harvester, which increases the harvesting performance of the harvester by swinging the support frame. Firstly, design the structure of the harvester and draw a physical model. Secondly, finite element models are used to simulate and analyze the structure's dynamic characteristics. Finally, make an experimental prototype of the harvester and explore the power generation characteristics of the device through experiments. The results indicate that the harvester has two natural frequencies under low-frequency conditions. The energy harvester has the optimal external resistance to achieve peak output power. The greater the excitation acceleration, the greater the total output power value of the energy harvester. When the mass of the mass block is 3.7 g and the excitation acceleration is 0.4 g, the total output power value of the energy harvester is 3.88 mW, and the harvesting frequency band is wide, indicating excellent output performance of the harvester. The experimental results of the energy harvester device are consistent with the simulation results, fully verifying the correctness of the experiment and simulation. This piezoelectric energy harvester can efficiently harvest vibration energy at low frequencies, providing a good prospect for supplying power to microelectronic devices.

In this study, an L-beam vortex-induced vibration piezoelectric energy harvester with interference step is proposed. The experimental results show that the interference step can broaden the effective wind speed bandwidth in the second resonance region of the energy harvester and increase its energy output amplitude significantly. When the load resistance is 90 k omega, the effective wind speed bandwidth in the second resonance region of the energy harvester can be expanded by a maximum of more than 200%, and the peak output power can be increased by a maximum of 291% by adjusting the position, width and height of the step.

In order to obtain a portable and simple vibration energy harvester and overcome the problem of low output of traditional energy harvesters,a double-L bracket kickback piezoelectric energy harvester was proposed,which combined the nonlinear characteristics of the tensile structure with piezoelectric technology,which could effectively improve the dynamic response and output performance of the energy harvester.The effects of external resistance,magnetic distance,excitation acceleration and angle on the output performance of the harvester were analyzed.The experimental results show that the output power reaches the peak value of the harvester at the optimal external resistance value,and the optimal external resistance value is 200 kΩ.The introduction of magnetic force can significantly improve the output performance of the energy harvester.At a magnetic distance of 18 mm,the harvester captures the most energy,and its optimal output performance reaches 1.12 mW at 12.1 Hz.In addition,the excitation acceleration has an obvious impact on the output characteristics of the energy harvesting system,and the output voltage and output power of the energy harvester also increase with the larger the excitation acceleration,and the maximum output power of the energy harvesting system reaches 1.39 mW under the condition of the excited acceleration of 0.4 g and the frequency of 12 Hz.The harvester has good output voltage and output power in the angle range of 0°～45°,and has the advantage of working under the condition of uncertain excitation direction.Practical application experiments further prove that the energy harvester can continuously output a large and stable voltage,which provides an effective solution to solve the problem of low output of traditional energy harvester.