Imbalance Diagnosis And Optimization For Helicopter Rotor Balance

During the production and usage of helicopter rotors, there could be static imbalance,dynamic imbalance and aerodynamic imbalance due to various reasons. The above-mentioned imbalance might increase helicopter's vibration, weakening staffs' persistence, and equipment's performance and endurance, which makes it necessary to level the rotor. However, the leveling nowadays is mostly based on experiences, and the routine of adjustment, test, and readjustment, it may take a long time, and decrease sortie rates. Then a related software is designed in this article,which can diagnose the reason and the extent of imbalance based on the fuselage-vibration, and give the optimal option to level the rotor. This article contains four parts as below.(1) To separate the vibration signal of the fuselage in order to acquire the vibration component of the rotor. Amplitude Comparison is used in this step, according to which, frequency components from the same resource have the same proportion in different mixed signals. This method can achieve nice result when dealing with signals whose frequencies differ from each others', and these frequencies are not close to the structure's natural frequencies.(2) To diagnose the reason and the extent of imbalance based on the vibration signal. Gray relational grade is used in this step. Based on the vibration data under different imbalance conditions, relational grades between signal measured and signals in the data base can be acquired to determine the reason and the extent of imbalance. In this step, gray relational grades between vibration signals under certain conditions are interpolated to acquire a continuous function, based on which the extent of imbalance of any vibration signal can be determined.(3) To acquire the optimal option to level the rotor after determining the imbalance type and degree. In this article, the weighted average of vibration amplitude of different frequencies and under different flight condition is chosen to be the target variable, in order to chose the optimal leveling option, including leveling manner( pitch, counterbalance weight or tab) and extent.Genetic Algorithm(GA) combined with Newton method is used in this step. Vibration amplitudes after adjustment are interpolated, then the continuous function between leveling extent and vibration amplitude could be acquired. After that, GA is used for extent optimization, during which Newton method is used on each individual and each general to find a local minimum value,among which the minimum value in the whole interval can be acquired.