Research Of Hydraulic Small Diameter Ultrasonic Flow And Pressure Measurement Method

Hydraulic system is widely used in the transmission area with its inherent advantages. However ,it has the shortcomings of high failure rate and difficult in fault detection compared with the electric drive and mechanical drive system. The flow and pressure are the main parameters reflecting the hydraulic system condition and the basis of system fault diagnosis. This paper brings forwards the integrated program for flow and pressure measurement in hydraulic system using the ultrasonic technique that achieves non-invasive, real-time online measurement and lays solid foundation for fault diagnosis in hydraulic system.The propagation time method traditionally used in ultrasonic flow measurement is featured with large dispersion of the test result and high requirement on the counting pulse frequency during small diameter, low flow rate measurement. Aiming at this, the equivalent pulse timing method based on FPGA is proposed .To enable the measure system with more stability and reliability in performance, and make the system more integrated and more flexible, Taking the SOPC technology as the development platform and the ultrasonic measurement system with the propagation time method as the research object, initial design of the measurement system on chip based on SOPC is given in the paper and also given the specific implementation method.The main contents are as follows:1. Overview of the ultrasonic measurement development history, the research status and classification at home and abroad, and brief description of several representative ultrasonic measurement principles.2. Establishment of the mathematical model of flow and pressure measurement using the time difference method according to the ultrasound acoustic properties and the focus and difficulty obtained from the above: accurate measurement of ultrasonic propagation time difference.3. Based on discussion of several methods of time measurement, the method used to solve the problem chosen in this subject to obtain high precision measurement of the time is the FPGA based equivalent pulse method, and theoretical analysis is done on it based on the FPGA-based equivalent pulse method.4. The hardware design of the flow and pressure measuring system based on SOPC is introduced and the relevant circuit diagram is given.5. Software design method of the measurement system is discussed, blue print of several modules, the simulation diagram and the program are given. Emphasized introduction is done on the Nios II peripheral construction and the software design ideas. 6. Presentation of the data processing method of the system. Correction method of the time difference-velocity and time difference-pressure is given and the reason for measurement error and improve method are given in briefly in the paper.