ESA GNC Conference Papers Repository

For verification purposes of satellite rendezvous and docking maneuvers, hybrid simulation facilities, e.g. DLR’s rendezvous and docking simulator EPOS, are attractive solutions. They combine 1) numerical, multi-domain satellite simulation, 2) physical execution of computed trajectories by robots carrying satellite mockup and 3) sensor feedback of docking contact forces in a closed loop set-up. However, under typical contact dynamics conditions the docking simulation is numerically unstable and needs to be controlled, accordingly. For problem analysis purposes the hybrid simulator can be treated as network. Inside the network the robot subnet exchanges virtual power and physical power at is ports. However, the power magnitudes never coincide caused by the non-ideal robot dynamics and by control loop time delays. Under docking conditions, the robot subnet appears as active subnet making the entire hybrid simulation numerically unstable. For suppressing numerical instabilities a passivity control mechanism is proposed that makes use of the network approach. It consists of an observer that tracks the accumulated energy error introduced by the robot subnet and a numerical energy dissipator. The proposed control approach is verified by simulations of 1D/1DoF and 3D/6DoF scenarios as well as experimentally validated at the EPOS hybrid simulation facility.