Yarn speed and length are two important parameters in the winding process. A noncontact method is proposed to measure the speed and length of the microtension moving yarn automatically in the winding process. A moving yarn could vibrate sharply in the microtension range. With a line laser illuminating the moving yarn, a linear charge-coupled diode camera was used to capture the images. Based on different laser reflection of the yarn texture, we calculated the speed and length of the moving yarn by extracting different features of yarn texture. Yarns with different materials were used to prove the validity of the proposed method under different winding speed. Experiment works have been performed and compared with a direct contact sensor, and the results proved that the proposed method is effective.
In recent years, semi-passive vibration damping using Synchronized Switching Damping on Inductor (SSDI) technique has been intensively investigated. In this paper, a self-powered semi-passive vibration damping system based on self sensing approach is proposed and investigated. With the self-sensing technique, the same piezoelectric element can be used as a sensor and an actuator. Compared with the other self-powered SSDI approaches, this technique can not only detect switching time without lag, but also reduce the number of piezoelectric elements. Furthermore, a low-power circuit for semi-passive piezoelectric vibration control based on self-sensing technique is designed. Experimental results demonstrate that the self-sensing SSDI system has good damping performance. The performance of the self-sensing SSDI system is also compared with the externally powered system.
Energy harvesting systems are interesting for use in remote power supplies. Many such systems utilize the motion or deformation associated with vibration, converting the mechanical energy to electrical energy, and supplying power to other electronic devices. In terms of energy harvesting from mechanical vibrations, piezoelectric conversion has received much attention as it can directly convert applied strain energy into useable electric energy and easily be integrated into a microsystem. The removal of mechanical energy from a vibrating structure necessarily leads to a damping effect. This paper addresses the damping associated with a piezoelectric energy harvesting system which is called the adaptive synchronized switching harvesting (ASSH) technique. Furthermore, a self-powered circuit which implements the technique (ASSH) is proposed, which validates that the new technique can be truly self-powered. Experimental results show that the vibration amplitudes of the first two modes are reduced by about 9.27 dB and 0.96 dB in the case of the exciting signal of same amplitude ratio (3:3), respectively. Compared with other self-powered vibration damping technique, this technique not only shows its robustness, but also harvests the energy and supply power to other electronic circuits.