The Design And Experimental Study Of Integrated Test-bed For Hydraulic Oil Bulk Modulus

Modulus of hydraulic oil is an important physical parameter, and it is related to the physical properties and work status of hydraulic oil, which stands for the rigidity of the system, directly affecting the natural frequency and damping ratio of hydraulic oil system. With the requirements of control precision and dynamic response of hydraulic system improving continuously, the impact of modulus of hydraulic oil on dynamic performance of the system increasingly can not be ignored. It is the basis of improving the hydraulic system performance to obtain the accurate measurements and reveal the variation law of hydraulic oil bulk modulus.In this thesis, the defects of the previous measuring device is analyzed and a new oil bulk modulus comprehensive test-bed is designed which includes the vacuum degassing device, oil modulus measuring device and servo-valve cylinder system. The principle, structure and control system is designed in this thesis, and the error analysis for the measuring device is also done. Related experiments are done using the test bed to study the relationship between oil temperature, air content, pressure and oil bulk modulus and the impact of modulus on the dynamic characteristics of servo-control system.The validity and accuracy of the system are verified by experiments.The main research work of this paper is as follows:In the first chapter, the basic theory of oil bulk modulus is introduced, and the influencing factors are analyzed. It also elaborates on the common measuring method of oil bulk modulus, expatiates the research history and status about oil bulk modulus and its measure technology at home and oversea. Then expatiates on practical background of the project, in the end, puts forward the research significance and primary research content.In the second chapter, the principle and hydraulic system for the test-bed are designed, the closed pressure tank system is also designed, the theory design is completed for the vacuum degassing equipment and the servo valve cylinder system, and the component selection is done. According to the proposed design requirements, the performance of the servo valve cylinder system designed is analyzed, where the system performance can not meet the requirements of the design demand is corrected by control algorithm.In the third chapter, the design requirements are proposed, according to the design requirements, the principle, structure and hydraulic system design for the oil modulus measuring device are completed and the device sealing is designed. In order to saving space, most components are integrated in the hydraulic valve block, and the principle and structure of valve block are designed.Finally, the reasons which may cause detection errors are analyzed and the error size is calculated.In the fourth chapter, according to the demand of the measuring and control system, the data acquisition and control points are concluded, the data acquisition and control cards are selected,the control Interface is developed by Labview software,and the hardware and software design for the control system of the test-bed is completed.In the fifth chapter, related experiments are done using the test bed to study the relationship between oil temperature, air content, pressure and oil bulk modulus, and the impact of modulus on the dynamic characteristics of servo-control system. The validity and accuracy of the system are verified by experiments. Repeated experiments are done and the results show that the detection device designed has very high repeatability accuracy.In the sixth chapter, the main research work and production of this paper is summed up. The further research work and direction are in expectation.