基于模型的故障诊断方法在处理具有不确定参数的复杂非线性系统时,由于仿真结果的不精确导致诊断错误.而传统的区间算法又容易发散,为此,引入模态区间分析方法对含有不确定性参数的非线性系统进行建模仿真和故障诊断.模态区间分析方法通过定义逻辑谓词对区间进行语义解释,从而得出系统工作区间的精确包络线,在此基础上进行的故障检测与诊断是可靠的.利用模态区间分析方法对某大型液体火箭发动机进行模拟仿真与故障诊断,结果表明:得到的系统工作区间包络线是正确的,进行故障诊断得到的结果是真实可靠的. When dealing with complex nonlinear systems with uncertain parameters, the model-based fault diagnosis results in diagnostic errors due to the inaccuracy of the simulation results, and the traditional interval algorithm is easy to diverge. Therefore, the method of modal interval analysis Nonlinear systems with deterministic parameters for modeling and fault diagnosis.Modal interval analysis method through the definition of logical predicate semantic interpretation of the interval, so as to draw the precise envelope of the system work area, on the basis of fault detection And the diagnosis is reliable.The simulation and fault diagnosis of a large liquid propellant rocket engine are carried out by using the method of modal interval analysis.The results show that the envelope of the system working area obtained is correct and the result of fault diagnosis is true and reliable .