Theory And Method On Damage Modeling And Prognostics For Planetary Gear Set Of Helicopter Transmission System

As a type of low-flying craft, helicopter is widely used and plays a significant role in many areas of national economy. Due to its non-redundancy structure and severse operation condition, the faults in the parts of transmission system of helicopter are common, which always cause catastrophic accident.The development of Prognostics technology promotes the security of helicopter transmission system. There exist some problems such as the fault mechanics is undefinited, run-to-failure data is hard to obtain, incipient damage is difficult to detect, prognosis feature selection is not quantitative etc. After that, the key component named as planetary gear set in helicopter transmission system is selected, and the corresponding theories and methods of damage modeling and failure prognosis are researched. The detailed contents and innovative work can be summarized as follows.1. The modeling methods of normal damages in planetary gear set are researched systematically, in order to analyze the impact of normal damages to the dynamical characteristics of planetary gear set.(1) The lumped parameter dynamical models of the normal damages in planetary gear set are investigated. By the analysis of damage mechanics and time-varying meshing stiffness, the common damages such as root fatigue crack, pitting, scuffing and tooth breakage in the sun gear of planetary gear set, are developed.(2) The multi-body dynamical modeling methods of common damages in planetary gear set are presented. Based on contact function analysis, the multi-body dynamical models of the damages such as pitting and tooth breakage are built.The research shows that the models above represent dynamically the response of planetary gear set with common damages, which are the basis of incipient damage detection, degradation state recognition and failure prognosis.2. Feature extraction method based on simulation data and statistical algorithm is presented. And then, a grey relational analysis (GRA) based method is proposed for incipient damage detection and pattern recognition.(1) Multiple domain information based feature generation method is researched based on simulation data of the models above. And the feature evaluation and weighting approach is processed utilizing the sensitivity analysis and stability analysis. .(2) Based on the features extracted above, GRA is utilized into incipient damage detection and pattern recognition for planetary gear set.The above research shows the features extracted above are effective for sun gear damages in planetary gear set, which have the merits of sensitivity and stability compared to the traditional indicators. The effectiveness of the detection and recognition approach based on GRA is validated by damage seeded test data. 3. A prognosis feature extraction and selection method based on the simulation information of damage propagation is derived, in order for degradation state recognition and failure prognosis. On the basis of the prognosis feature extracted above, GRA and feature weighting vector are united to recognize the degradation states of planetary gear set.The research shows that a quantitative criterion is set to extract and select prognosis feature, which is suitable for degradation state recognition. The test results validate that the approach based on grey probability relational analysis is effective in degradation state recognition for sun gear root crack of planetary gear set.4. To resolve the problems of failure prognosis for sun gear tooth crack in planetary gear set, the residual useful life (RUL) prediction approach based on damage evolution mechanics is researched, and then the RUL prediction approach based on a modified grey model is presented firstly.(1) A damage evolution mechanics model of sun gear root fatigue crack of planetary gear set based on Paris equation is researched. After that, the RUL prediction approach based on mechanics model is researched. And then the accuracy of prognosis result is evaluated.(2) The grey model is modified and utilized to predict the RUL of planetary gear set with sun gear root fatigue crack for the first time.The research shows that the damage evolution mechanics model need modification by run-to-failure data and operation profile data. And the RUL prediction method based on mechanics model holds high accuracy. Compared to the traditional grey model, RUL prediction method based on modified grey model has merit on the accuracy of prediction results.5. Aiming at the helicopter transmission, the architecture of PHM system is analyzed. After that the corresponding hardware system and software system are developed. After all, the system is tested in experiment condition.The research shows that the PHM prototype system of helicopter transmission system has five main functions, which are composed of data acquisition and real-time condition monitoring, signal playback and feature selection, incipient damage detection and pattern recognition, conditon trend prognosis and RUL prediction, and data & information & knowledge management.