Technology Research On Conditioning And Acquisition For Tip-timing Signal

Fierce blade vibrations often cause running faults in large rotating machinery,and they are subject to complex environments with high temperature,high pressure,high speed,heavy load and many other conditions existing during the rotating of blades,making the research of non-contact tip-timing vibration measurement technique especially important.However,in traditional blade vibration system based on tip-timing principle,tip-timing processing algorithms do not take the impacts brought from tip-clearance into consideration;lacks of the analysis of system accuracy;real-time and high-speed transmission of vibration data will also be limited in the near future.Thus,our research group has conducted some improvements against these problems on the basis of the original tip-timing vibration measurement system.The main contents of this thesis are as follows:1?The self-developed blade vibration measurement system online by our lab based on fiber-bundle has been introduced.And the timing accuracy of tip-timing sensor has been analyzed,including the analysis of the tip-timing sensor model,reflected light model and the tip-timing signal.2?In order to solve the influence of varying tip clearance on tip-timing system,the improvements based on algorithm processing and hardware circuit design for this problem are proposed in this article.In algorithm,new time of arrival can be obtained by using the two edges of the tip-timing signal and calibration of rising time,falling time,which is made hardly change under the variation of tip clearance;in hardware design,we mainly use AGC circuit to keep tip-timing signal amplitude stable,thereby reducing the influence of the tip clearance.And finally these methods' ability to reduce the influence of tip-clearance change on tip-timing system are verified through experiments to enhance measurement accuracy.3?Taking into account the scientific and technological advances and the increase of the rotational speed and rotor series,which cause the vibration data of system real-time transmission growing gradually,the development of high-performance acquisition and processing equipment with high-speed real-time data collection,storage and processing capabilities is needed.It is analyzed that thethird-generation PCIE bus can realize high-speed data acquisition and processing system.And in this paper the PCIE bus system architecture and protocol specification interface,as well as the advantages PCIE bus are introduced.4?Considering performance,cost and other factors,this paper proposes a method of using PEX8311 of PLX to realize the interface between PCIE and Local.Schematic of PCIE acquisition system and PCB design,and debug PCIE acquisition board have been completed.The whole hardware design of the system uses a modular design structure,the hardware system is divided into a digital signal preprocessing module,data caching,PCIE bus interface,a local bus control logic and other major modules.Tests showed that the data transfer speed of the PCIE system can reach 170MB/s,in real time,already meeting the design requirements.