非高斯噪声下基于U-粒子滤波器和似然比的非线性系统故障诊断

针对普通粒子滤波器在非线性系统随机系统故障诊断中的“退化”现象和估计精度的不足，进而影响诊断准确率的问题，提出应用U-粒子滤波器(Unscented particle filter，UPF)进行改进的方法。在建立正常/异常UPF滤波器模型的基础上，推导基于UPF的似然概率密度函数和似然比(Log likelihood ratio，LLR)计算方法，构造故障的检测律和诊断律，并给出完整的故障诊断算法，不仅能准确预报故障发生的时刻，而且可以诊断出故障的类型。最后在某直升机非线性舵回路上进行了试验验证，结果证明了该方法的有效性和优越性。

UNSCENTED PARTICLE FILTER AND LOG LIKELIHOOD RATIO BASED FAULT DIAGNOSIS OF NONLINEAR SYSTEM IN NON-GAUSSIAN NOISES

As for the problem of fault diagnosis of nonlinear system in non-Gaussian noises,a new method based on the unscented particle filter(UPF)is proposed,concerning of the shortcoming of degeneracy and estimation precision of generic particle filter.Firstly,normal/abnormal UPF models are estab- lished separately,and the calculation method of likelihood probability density function and log likelihood ratio are de- ducted.Then,the fault detection and diagnosis rule are given, which can forecast both the happening time and type of the fault.At last,some experiments of nonlinear actuator loop of helicopter are carded out,which can demonstrate the validity and superiority of the proposed method.