A HIL testbed for small unmanned helicopter's initial controller gain tuning

A Hardware-In-The-Loop (HIL) testbed design for small unmanned helicopters is described. The testbed provides a safe and low-cost platform to implement control algorithms and tune the control gains in a controlled environment. Specifically, it allows for testing the robustness of the controller to external disturbances by emulating the hover condition. A 6-DOF nonlinear mathematical model of the helicopter has been validated in real flight tests. This model is implemented in real-time to estimates the states of the helicopter which are then used to determine the actual control signals on the testbed. A damping system with a negligible parasitic effect on the dynamics of the helicopter around hover is incorporated into the testbed design to minimize the structural stress on the fuselage in the case of controller failure or a subsystem malfunction. Three experiments including the longitudinal, lateral and heading control tests are performed. Experimental results show that the HIL testbed allows for designing a controller which is robust to the external disturbances, and achieves an accuracy of ±2cm in the position control along the longitudinal and lateral axes in hover, and that of ±1deg around the yaw axis on the heading trajectory tracking.