Normalized passivity control for hardware-in-the-loop with contact

Mechanical contact occurs in many engineering applications. Contact dynamics can lead to unwanted dynamic phenomena in mechanical systems. Hence, it would be desirable to investigate the influence of contact dynamics on a dynamical system already in the development stage. An appropriate method is Hardware-in-the-loop (HiL) on mechanical level. However, the coupling procedure in HiL is prone to stability problems and previous studies revealed that HiL tests of systems with contact are even more challenging, as the system dynamics change rapidly when contact occurs. Passivity-based control schemes, well-known from teleoperation, have recently been used to stabilize HiL simulations of systems with continuous dynamics. Here, we investigate the applicability of Normalized Passivity Control to HiL tests of a one-dimensional mass-spring-damper system experiencing contact. Experimental results reveal that this kind of passivity control keeps the test stable and also improves the test fidelity. This research is an important first step in using passivity control for stable and safe hybrid simulation of complex systems with contact using HiL approaches.