Abstract
Hydraulic systems have been widely used in construction machinery, aeronautics, astronautics, automobiles, shipping, and other fields. Piston pumps are power source and core component in the hydraulic system. The detection and assessment of leakage fault in piston pumps is challenging because: 1) piston pump is always subjected to varying loads and operates at variable speeds, and the conventional condition monitoring methods that rely on instantaneous behavior analysis can hardly give reliable prediction to the actual health state of the piston pump and 2) it is not easy to obtain the typical condition monitoring data that can reflect the change of the piston pump in dynamic behavior when it suffers different severity levels of faults under various loading conditions. In order to tackle these issues, a model-based method for leakage detection of piston pump under variable load condition was proposed in this paper. The liquid–solid coupling model of piston pump is developed and verified at first. Then, with the aid of the model, different severity levels of oil leakage faults are simulated. It is found that outlet pressure signals can better indicate the oil leakage of piston pumps in comparison to the casing vibration signals. “Sub-harmonics” will appear in the frequency spectra of outlet pressure signals in the presence of oil leakage fault. Finally, the dynamic responses of the piston pump under different loading and structural health conditions are investigated systematically. The results show that external load can significantly influence the dynamic responses of the piston pump and the gradients of the trend lines of total “sub-harmonic” energy of outlet pressure provide correct prediction to the presence and growth of the oil leakage fault. Based on the investigation results, a reliable oil leakage detection and assessment method is proposed.
Highlights
Hydraulic systems have been widely used in construction machinery, aeronautics, astronautics, automobiles, shipping and other fields
The following key information can be obtained from the above calculation results. They provide important clues for detecting and assessing the oil leakage fault in piston pumps: 1) The outlet oil pressure signals will be deformed in the presence of oil leakage fault
In order to achieve a more reliable technique for detecting and assessing the oil leakage fault occurring in piston pumps, in-depth analysis of the dynamic responses of the piston pumps is conducted based on the liquid-solid coupling model of a seven-piston piston pump
Summary
Hydraulic systems have been widely used in construction machinery, aeronautics, astronautics, automobiles, shipping and other fields. From Fig., it is noticed that the oscillations of both the velocity and acceleration of the reciprocating motion of the piston and total flow obtained from the liquid-solid coupling model are not stable until 0.2s This is because in the calculations, the rotational speed of the input shaft is set to gradually increase from 0 to 1500rev/min within 0.2s. It can be concluded that the liquid-solid coupling model developed in Section 2 can accurately simulate the operation of the piston pumps It is noticed from Fig. that the total flow obtained from the model is slightly smaller than that derived from the equations. All the following research results developed based on this liquid-solid coupling model should be reliable
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