A Cooperation Analysis Method Using Internal and External Features for Mechanical and Electro-Hydraulic System

Feature extraction is of great importance for running states monitoring and performance evaluation of mechanical electro-hydraulic systems (MEHS). However, due to the complexity of the multi-domain energy conversion property of MEHS, especially during the varying operation conditions, it is quite difficult to extract the desired features effectively. In addition, the conventional signals are difficult to be collected and analyzed, as different kinds of coupled information are mixed together. Therefore, based on a power distribution analysis of MEHS, it is found that the change rate of the kinetic energy (CRKE) can be considered as a suitable index for evaluating the performance, such as energy saving and output stationarity of the considered MEHS. In order to characterize the magnitude of CRKE, a cooperation analysis method is proposed by using internal and external features. In the proposed method, the kinetic energy stiffness (KES) is selected as the internal feature, while the instantaneous speed fluctuation (ISF) is chosen as the external feature. According to a Lissajous figure-based information fusion approach and the order tracking technology, a systematic method is developed to obtain the magnitudes of KES and ISF. Furthermore, based on the complementary advantages and mutual relationship of KES and ISF, the performance of MEHS is analyzed under varying operation conditions. The proposed method is verified through experiments with a real rig. The results show that the changes of KES and ISF can effectively reflect the change in the operation condition, and lower KES loss can improve the efficiency of the system and also restrain the ISF.