This paper presents an asymmetric magnetic coupling piezoelectric energy harvester (PEH) based on galloping to scavenge low-speed wind. The piezoelectric beam of energy harvester undergoes bending and torsional vibration simultaneously due to the eccentric distance. By analyzing the kinetic energy, potential energy, and virtual work of the energy harvesting system, the mathematical model of harvester is constructed and verified by experiments. The optimal external load resistance is confirmed at different eccentric distances and wind speeds by experiments. Compared with traditional galloping piezoelectric energy harvester (GPEH), the asymmetric with magnetically coupling GPEH has a lower threshold wind speed, i.e. 2 m s ⁻¹ . And the asymmetric configuration contributes to a lower natural frequency and electromechanical coupling coefficient, which results in a lower power and voltage output. The potential energy of harvesting systems at different distances between two magnets are respectively numerical analyzed in detail. The theoretical results illustrate that the energy harvester operates in monostable and bistable at different magnet distances. And the threshold wind speed of energy harvester increases when the energy harvester works at bistable. According to the above analysis, this work provides a detailed guideline for mathematical modeling and performance improvement of asymmetric PEH based on galloping.

This paper presents a direction adaptive energy harvester to scavenge multiple wind directions. A pair of rotatable hinges were fixed on a rotation axis to realize the orientation adaptive. The transverse bending vibration of piezoelectric beam induced by vortex shedding was converted into electricity while the change of relative position between magnets and coils output electricity too. The prototype of the energy harvester was fabricated and experiments were carried out. The harvester exhibited that the optimal power of piezoelectric and electromagnetic generation are, respectively, 5.19 mW and 0.32 mW in the wind speed range of 3.8 m/s to 6.4 m/s.

Aiming at the demand of rapid detection for coaxiality of crankshaft journal, a method of visual measurement of coaxiality error based on 3D point cloud is proposed. In this research, a laser scanner is utilized to obtain a 3D point cloud model of the part to be measured, and a circular method of rotary cutting is put forward to obtain equally spaced optimal slices of the journal. The center of the slice is then obtained using the Pratt circle fitting method optimized in this paper. After that, the center of the slice is used to obtain the common reference axis using the least squares method, which finally realizes the measurement of the coaxiality error. The experimental results show that the proposed method of getting the slices is more accurate, the maximum absolute error of the circle fitting method compared with the results of the coordinate measuring machine (CMM) is no more than 4.2 μm, and the maximum absolute error of the coaxiality detection results and the results of the CMM is 5.5 μm, which can satisfy the practical needs of fast and efficient measurement of the coaxiality error of crankshafts.

In order to overcome the shortcomings in the traditional envelope analysis, the methods based on the wavelet transform and morphological filters are introduced for detecting defects in rolling element bearings. The method based on the analytic wavelet can be applied to non-linear and non-stationary bearing vibration signals. The method based on the morphological filters has the advantage of less computation, and it can be used for on-line diagnosis. The results show that the proposed methods can diagnose the faults in rolling element bearings.

This paper presents a magnetic coupling piezoelectric energy harvester based on galloping and vortex-induced vibration to scavenge low-speed wind. The influence of magnet spacing on the piezoelectric energy harvester is analyzed by using a mathematical model. The power generation performance of the energy harvester is explored by changing the magnet spacing. The experimental results show that the distance is negative related to the onset wind speed. Vortex induced vibration still make the system have voltage output. The output power can be effectively improved by increasing the magnet spacing while the magnetic force beyond a certain range can be ignored.