A general framework for a control-based design of power and mechanical hardware-in-the-loop systems

Many studies on power and mechanical hardware-in-the-loop (HiL) systems emphasise the importance of stability and accuracy issues. These are especially crucial for full-scale HiL systems, because their actuators, linking virtual and real parts, must not be neglected in the design of the overall system. In this paper, we propose a general, control-based strategy with a simple two-step design procedure. First, an inner control loop is designed to provide an appropriate input interface to the hardware part including said actuators. Then, the virtual software part is connected to the hardware using the notion of internal model control. A finding is that, in principle, the choice of interface directions does not matter when an inner control loop is needed because of the non-negligible actuator dynamics. Furthermore, it is demonstrated how the proposed control strategy allows for directly integrating existing software models. A simulation example with a large dynamometer for testing nacelles of wind turbines is presented to illustrate the methodology.