Research on tolerance processing method for analog circuit soft-fault diagnosis based on normal quotient distribution

While the slope fault model method can solve the soft-fault diagnosis problem in linear analog circuit effectively, the challenging problem about tolerance is still unsolved. In this paper, a proposed normal quotient distribution method was combined with slope fault model to process the tolerance problem in soft-fault diagnosis for analog circuit. Firstly, several typical tolerance processing methods on the ground of the slope fault model were compared. Then, the approximating distribution function of the slope fault characteristic was deduced, and the basic condition was given to improve the approximation accuracy. The monotonous and continuous mapping between normal quotient distribution and standard normal distribution was proved. Thus the estimation formulas about the range of the slope fault characteristic were deduced. After that, a new test-nodes selection algorithm based on the approximating condition was designed, which can reduce the computation greatly. Finally, the experiments were done to illustrate the proposed method and demonstrate its effectiveness.