Toward robotic pseudo-dynamic testing for hybrid simulations of air-to-air refuelling

Hybrid simulation couples experimental tests of novel components to validated numerical models of the remainder of a system and provides high-confidence predictions of their coupled dynamic behaviour. Air-to-air refuelling (AAR) is an example of the type of system that can benefit from this development approach. The work in this paper concerns the on-ground validation and pre-flight verification of probedrogue contact-impact scenarios in AAR manoeuvres using offthe- shelf multi-axis industrial robots as part of a hybrid test to interface the refuelling hardware with numerical models of the flight environment. While industrial manipulators present a costeffective solution, bandwidth and power limitations inevitably cause practical problems for real-time hybrid testing. These deficiencies typically manifest themselves as significant tracking inaccuracies or instabilities when sharp non-linearities or discontinuities are encountered as part of a contact phase. Here, the novel Robotic Pseudo-Dynamic Testing (RPsDT) method is employed to circumvent the contact-response speed limitations of industrial robots. This paper, (i) presents and discusses the application of RPsDT to contact-impact problems, (ii) outlines the challenges and limitations of the technique in an easily reproducible validation experiment and (iii) details the first RPsDT hybrid simulation of an AAR manoeuvre using scaled refuelling hardware. It is concluded, that RPsDT provides a useful tool for the investigation of a particular sub-class of multi-body contact-impact problems including AAR, where the response of the contacting structures does not possess significant rate-of-loading effects. Future work will comprise tests with fullscale AAR hardware.