Hardware-in-the-loop simulator for research on fault tolerant control of electrohydraulic flight control systems

This paper describes the development of a hardware-in-the-loop (HIL) simulator to support the design and testing of novel fault tolerant control and condition monitoring schemes for fluid power systems emphasizing flight control applications. The simulator uses a distributed architecture to share, in a synchronized manner, the demanding computational load associated with the real-time simulation amongst a number of desktop workstations connected by a dedicated Ethernet network. The simulator runs a high-fidelity model of the F-16 fighter aircraft that is augmented in this paper by the addition of realistic nonlinear models of the hydraulic flight control surface actuators and a model of the nonlinear control surface aerodynamic loads. A specially designed state-of-the-art hydraulic test rig, which has the capacity to experimentally simulate common failure modes of a typical fluid power circuit, is used to emulate a F-16 horizontal tail actuator. The experimental actuator can thus be exercised against the realtime simulation of a F-16 aircraft operating under a variety of normal or faulty conditions. To add further realism to the simulation, a second experimental hydraulic actuator is used to generate the aerodynamic disturbing load. Novel fault tolerant control and diagnosis algorithms can therefore be verified in a realistic application scenario. Pilot-in-the-loop simulations are supported by the inclusion of a graphical visualization of the aircraft motions. The results of a typical HIL experiment, for a normally functioning hydraulic system, are presented to illustrate the operation of the simulator