Design optimization considering performance and reliability

Current design and optimization of a flight control actuator system is based on a traditional design theory and sophisticated methods to get stable and good performance ability, but designed scheme may be sensitive to the environment fluctuation, internal parameter variation and component catastrophic failure. Reliability of actuator system is the ability that system can satisfactorily implement its defined function. There are two kinds of factors influencing actuator reliability, one is component catastrophic failure; the other is disturbance from internal parameters and environment variations. Both factors may cause performance degradation (soft failure) and even result in mission abort (hard failure). In a redundant actuator system, component catastrophic failure will result in more serious performance degradation, even if it cannot cause hard failure. In this research, in order to improve the reliability and performance simultaneously, we have developed an integrated design optimization method which integrates performance and reliability requirements into the design process. A mathematical model for an electro-hydrostatic actuator (EHA) has been built first and then injected with uncertain characters of parameters variations, component failure and disturbance from environment based on their distributions and mission profile. After that, a response surface between reliability and system design dependent parameters (DDPs) has been created based on the simulation performance results, thus producing optimized DDPs. The simulation results have also shown that this method is feasible.