Laboratory experimentation of autonomous spacecraft approach and docking to a collaborative target

A new laboratory test bed is introduced that enables the hardware-in-the-loop simulation of the autonomous approach and docking of a chaser spacecraft to a target spacecraft of similar mass. The test bed consists of a chaser spacecraft and a target spacecraft simulator floating via air pads on a flat floor. The prototype docking interface mechanism of the Defense Advanced Research Projects Agency's Orbital Express mission is integrated on the spacecraft simulators. Relative navigation of the chaser spacecraft is obtained by fusing the measurements from a single-camera vision sensor and an inertial measurement unit, through Kalman filters. The target is collaborative in the sense that a pattern of three infrared light emitting diodes is mounted on it as reference for the relative navigation. Eight cold-gas on-off thrusters are used for the translation of the chaser vehicle. They are commanded using a nonlinear control algorithm based on Schmitt triggers. Furthermore, a reaction wheel is used for the vehicle rotation With a proportional derivative linear control. Experimental results are presented of both an autonomous proximity maneuver and an autonomous docking of the chaser simulator to the nonfloating target. The presented results validate the proposed estimation and control methods and demonstrate the capability of the test bed.