Toward Robotic Pseudodynamic Testing for Hybrid Simulations of Air-to-Air Refueling

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 behavior. Air-to-air refueling (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 preflight verification of probe-drogue contact-impact scenarios in AAR maneuvers using off-the-shelf multiaxis industrial robots as part of a hybrid test to interface the refueling hardware with numerical models of the flight environment. While industrial manipulators present a cost-effective 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 nonlinearities or discontinuities are encountered as part of a contact phase. Here, the novel robotic pseudodynamic testing (RPsDT) method is employed to circumvent the contact-response speed limitations of industrial robots. This paper presents and discusses the application of RPsDT to contact-impact problems, outlines the challenges and limitations of the technique in an easily reproducible validation experiment, and details the first RPsDT hybrid simulation of an AAR maneuver using scaled refueling hardware. It is concluded that RPsDT provides a useful tool for the investigation of a particular subclass of multibody 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 full-scale AAR hardware.