The Design And Investigation Of The Measurement And Control Platform For The Variable Speed Mechanical And Electrical Hydraulic System

Conventional control methods applied in the engineering machine hydraulic system,like servo valve control,variable displacement control,load sensitive control,etc,have many disadvantages,such as energy saving effect is poor,slow speed of response,and so on.Through introducing the technique of frequency conversion velocity modulation and variable rotational speed pump-control-motor system design,the system performance,including the response speed、energy saving effect,reliability,and service life,can be effectively improved.In order to realize the multi-source information acquisition and on-line monitoring for the variable speed mechanical and electrical hydraulic system,we investigate the practical problems in the comprehensive research and design the measurement and control platform based on virtual instrument for the variable speed mechanical and electrical hydraulic system.This designed platform will be promising for measuring running status,performance evaluation,intelligent control and fault diagnosis of the variable speed mechanical and electrical hydraulic system.The main contribution of this paper is shown below.First,we determine the design scheme for the measurement and control platform of the variable speed mechanical and electrical hydraulic system,based on the measurement and control requirement analysis for the variable speed mechanical and electrical hydraulic test rig.Moreover,the softwares and hardwares for measurementand control are introduced in detail,as well as the sensors.Second,we design the PC software of data acquisition and system control for the variable speed mechanical and electrical hydraulic system with Lab VIEW.Verified by experiments,this designed software helps to realize a lot of functions,such as system parameter acquisition,display,storage,load simulation,motor speed control,etc,which satisfies the requirement of the measurement and control for the variable-speed electromechanical liquid system.At last,in order to mitigate the frequency converter interference in the measurement and control system,two methods are proposed,namely,the hardware and software filtering.For the hardware filting,we compare the analyze the optoelectronic isolator experiments with different installation positions,and get the results that hardware isolation with judicious utilization of the optoelectronic isolator can effectively restrain the system interference;For the software filtering,we use the FIR digital filter and wavelet de-noising processing to mitigate the interference based on the signal analysis with Fourier transform,and obtain the results that,both of these two methods can filter out most of the interference,and wavelet de-noising performs better.Furthermore,the hardware isolation method leads to a better and more steady system state for the variable-speed electromechanical liquid system measurement and control platform.