Papers by Author: Pei Jiang Li

Abstract: Acoustic emission is generally high-frequency signal with the characteristics of broadband and burstiness, so it is very difficult to acquire acoustic emission signal in real time as well as rapidly, In this paper, an USB based acquisition system for acoustic emission signal is designed, which adopts CPLD as controller and uses two high-speed A/D converters to achieve synchronous acquisition of two-channel acoustic emission signals, The system first puts collected data into a FIFO and then transfers data to host through USB using CY7C68013, The sampling frequency of the system is up to 10MHz and the transmission rate of USB is 40M/S, Hard body impact test and lead-breaking test indicate that the system can achieve real-time acquisition of acoustic emission signal well,

Abstract: For optimal control of synchronous machine, chattering phenomenon will appear if traditional slider control is adopted because permanent magnet synchronous machine is a complex nonlinear time-dependent system with strong coupling of current and rotational speed to cause the deterioration of system control performance with load or load disturbance. In this article, based on the mathematical model of permanent magnet synchronous machine, a control system for it, which combines sliding mode control and active disturbance rejection control, is proposed to improve the dynamic performance and robustness of control system. In the control system, sliding mode control is adopted to control the inner current of machine and active disturbance rejection control is adopted to control the outer speed. The load disturbance of system is also estimated and offset. The results of matlab simulation show that the control system can eliminate serious chattering phenomenon existing in sliding mode control, improves the robustness of system for load and system parameter disturbance as well as has great dynamic and static performance.

Abstract: The grinding wheel wear status is an important guarantee for the processing efficiency and processing quality of precision and super precision grinding. In this paper, a USB acoustic emission signal acquisition system is designed for online monitoring of grinding wheel status. In the system, CPLD is used as the controller, and a high-speed A/D converter is used to implement the synchronous acquisition of acoustic emission array signals. The collected data are sent into FIFO, and CY7C68013A is used for USB data transmission with upper computer. The sampling frequency of the system can be 10 MHz, and USB transmission speed can reach 40M/S. It is proved that it can meet the monitoring requirements of grinding wheel wear status well by the grinding processing.