Research and Study of Analytical Techniques for Predicting Reliability of Flight-Control Systems

摘要

The objective of this program was to develop analytical techniques for predicting the performance variability of flight-control components with respect to time, whereby an inference of their drift reliability can be made without resorting to life testing of the components themselves. The techniques of analytical reliability prediction being developed at Battelle use a model that relates performance aspects of a device to its input and internal parameters. By manipulation of this model, partial derivatives of each performance characteristic with respect to internal parameters are derived. A propagation of variance formula, which utilizes the partial derivatives and values of parameter variance, is used to compute the variance of each aspect of device performance. A reliability estimate can then be derived by comparing the expected range of variability for the time in question with appropriate specification limits. A definite procedure for applying the moment method to a servo valve and hydraulic actuator is illustrated, with emphasis given to modeling this combination and to deriving the necessary data (performance partial derivatives and parameter variance) for utilization in the Propagation of Variance formula. A generalization of this analysis is presented which shows promise for application to other multiparameter precision devices. (Author)