In order to improve the output characteristics of the electromagnetic energy harvester in a high-speed flow field, a spring-coupling electromagnetic energy harvester (SEGEH) is proposed, based on the galloping characteristics of a large amplitude. The electromechanical model of the SEGEH was established, the test prototype was made, and the experiments were conducted using a wind tunnel platform. The coupling spring can convert the vibration energy consumed by the vibration stroke of the bluff body without inducing an electromotive force into the elastic energy of the spring. This not only reduces the galloping amplitude, but it also provides elastic force for the return of the bluff body, and it improves the duty cycle of the induced electromotive force and the output power of the energy harvester. The stiffness of the coupling spring and the initial distance between the coupling spring and the bluff body will affect the output characteristics of the SEGEH. At a wind speed of 14 m/s, the output voltage was 103.2 mV and the output power was 0.79 mW. Compared with the energy harvester without a coupling spring (EGEH), the output voltage increases by 29.4 mV, with an increase of 39.8%. The output power was increased by 0.38 mW, with an increase of 92.7%.

In this paper, a frequency-adjustable tuning fork electromagnetic energy harvester is introduced. The electromagnetic vibration energy harvester can adjust its natural frequency according to a change in the environmental excitation frequency without any change to the structure. In the frequency-adjustable range, it can make the energy harvester resonant with the environment excitation, and the output frequency stays the same. The frequency-adjustable tuning fork electromagnetic energy harvester significantly increases the range of frequencies used. The operating frequency of the centre can be easily switched from 9.2 to 20 Hz, enabling the application of multiple excitation frequencies. In addition, the output power and power density are significantly increased compared to a piezoelectric tuning fork energy harvester of the same size. The peak power is 23.59 mW at 9.2 Hz, the power increases by 14.85 mW, and the power density increases by 169.88%. The experimental results show that the electromagnetic tuning fork frequency-adjustable conversion energy harvester can make the LED lamp work.

Energy harvesting in multi-directional excitation for human wearable devices is a challenge. A rotating electromagnetic energy harvester (REMEH) based on an eccentric rotor structure is proposed in this paper. Two poles of the magnets in the REMEH are alternately arranged in a ring. The electrical output characteristics of the energy harvester are analyzed through theoretical, numerical simulation and experimental testing methods based on the establishment of magnetic flux density models, the coil induced voltage, and the excitation direction of the eccentric rotor structure. Theoretical analysis and experimental results show that the design of the eccentric rotor structure is well adapted to multi-directional and irregular excitation. The circular staggered arrangement of the magnets effectively increases the output voltage and output power. The results show that the average output power increases slowly when the walking speed increases from 1 to 3 km h⁻¹, and the average output power increases substantially when the walking speed increases from 3 to 5 km h⁻¹. When the walking speed is 1 and 3 km h⁻¹, the average output power is 0.439 and 0.638 mW, respectively. At a walking speed of 5 km h⁻¹, the average output power increases rapidly to 1.68 mW, corresponding to a power density of 16.59 μW g⁻¹. This high-performance energy harvester can provide effective power supply for wearable devices or low-powered sensors.

A modular, multi-functional (encompassing data acquisition, management, preprocessing, and transmission) sensing (MMFS) system based upon the Internet of Things (IoT) paradigm is discussed in this paper with the goal of continuous real-time, multi-sensor and multi-location monitoring of aircraft (including drones) structural performances during flight. According to industrial and system requirements, a microcontroller and four sensors (strain, acceleration, vibration, and temperature) were selected and integrated into the system. To enable the determination of potential in-flight failures and estimates of the remaining useful service life of the aircraft, resistance strain gauge networks, piezoelectric sensors for capturing structural vibrations and impact, accelerometers, and thermistors have been integrated into the MMFS system. Real flight tests with Evektor’s Cobra VUT100i and SportStar RTC aircraft have been undertaken to demonstrate the features of recorded data and provide requirements for the MMFS functional design. Real flight test data were analysed, indicating that a sampling rate of 1000 Hz is necessary to balance representation of relevant features within the data and potential loss of quality in fatigue life estimation. The design and evaluation of the performance of a prototype (evaluated via representative stress/strain experiments using an Instron Hydraulic 250 kN machine within laboratories) are detailed in this paper.

The circular Halbach array is of great application value in electromagnetic energy conversion. The Halbach array can be formed with multiple magnets according to a specific method. The magnetic flux intensity of the magnet array is concentrated and enhanced in a certain area. The concentrated magnetic flux intensity could lead to a higher rate of change in the magnetic flux when the magnet and the coil move relatively. The spatial arrangement, structural dimensions, and residual flux density of the Halbach array are the main factors affecting its performance. Some areas with almost no magnetic induction in the Halbach array affect the performance of electromagnetic energy conversion. This paper conducted a comparative study of the Halbach array and the two-directional magnet array in terms of energy conversion. The root mean square (RMS) value and phase of the induced voltage in the coil were analyzed by a finite element method. Simulation shows that the RMS value of the induced voltage in the coil is equal when the gap is 1.55 mm and the REMEH adopts either of the two magnet arrays. The two-directional array has advantages in the energy harvesting performance when the gap is less than 1.55 mm, while the Halbach array has advantages in the energy harvesting performance when the gap is greater than 1.55 mm. The experimental verification of the designed prototype was implemented in this study. The experimental voltage is in good agreement with the simulation voltage. The threshold value of the gap in the experiment is about 2 mm, which is slightly higher than the simulation value. This characteristic has a certain reference value for the application of the Halbach array in the electromagnetic field.