Hardware-in-the-loop simulator for research on fault tolerant control of electrohydraulic actuators in a flight control application

Testing fault tolerant control and diagnosis systems for hydraulic actuators under operating conditions that closely resemble the intended application is an important part of control system verification. This paper describes a hardware-in-the-loop (HIL) simulation framework that enables an experimental hydraulic actuator to be exercised as a flight control actuator against the numerical simulation of a high-performance jet aircraft. The HIL simulator is centered around a state-of-the-art hydraulic test bench that can experimentally simulate many of the common component faults in a servovalve driven actuator circuit. A second experimental hydraulic ram is used to create a wide range of in-flight operating conditions by replicating the aerodynamic load disturbance that is transmitted through the control surface hinge during flight maneuvers. The goal of the HIL simulator is to develop and objectively test novel fault tolerant control and diagnostics algorithms for fluid power actuators and to investigate, for the first time, the complex interaction between faulty flight actuator hardware and the overall aircraft performance. An overview of the HIL simulation architecture, which is executed on four networked desktop computers, is given and the hardware implementation is described. Issues related to the design of the force control system around the load emulator actuator are also discussed. The results of several HIL case studies, including a human-in-the-loop simulation, are presented to demonstrate the functionality of the HIL simulation environment.