Automated design of reconfiguration strategies increases reliability

Modern reliability engineering is challenged by tightening reliability and safety norms on the one hand and increasing flexibility and structural complexity of technical systems on the other. A “conventional” approach in reliability engineering offers plenty of methods for system analysis which can serve as a basis for altering the system design in order to guarantee higher reliability. Although this pattern is effective, it is also expensive (the later it is employed in the design process, the more expensive it will be) and time-consuming. This paper suggests a method that can be used along with the above-described “conventional” approach in order to increase the reliability of a class of mechatronic systems. The method involves the development of a fault-tolerant control system (FTCS). The controller-design process is more flexible than that of system design, and so a control system can be converted into an FTCS at any stage of the system design (even after it has been completed, as was the case with the example described below), thus consuming far less time and expenses. The basic idea behind the method of constructing FTCS is to switch the system after each fault of a component into a control strategy that will not need the faulty component and therefore cannot influence the system performance. In order to realize this task, FTCS consists of a fault detection unit, fault-driven reconfiguration chart (the state chart guiding a reconfiguration of the system after each fault of a component) and a set of emergency controllers (i.e., controllers to be activated after faults have been detected in the system to prevent fault propagation). Our paper presents an algorithm for constructing the fault-driven reconfiguration chart based on the fault tree analysis of emergency strategies. It also contains as an example an implementation of the approach outlined above. An active suspension system for the all-terrain vehicle “DINGO” was employed as a basic system. It has been shown that the concept of fault-driven reconfiguration can increase the reliability of the suspension and thus influence the driving safety. The reconfiguration chart was then analyzed in order to assess the impact of the properties of the FTCS (for example, fault detection probability) on the reliability of the overall system.