Cooperative control for relative translation of modular spacecraft without velocity measurements

In this paper, the problem of cooperative control for relative translation of modular spacecraft is addressed under a general undirected communication topology without velocity measurements. We consider the full nonlinear translation dynamics near earth. Two cases are studied, namely, the coordinated regulation problem with a stationary reference and the leaderless consensus problem without any leader. In the first case, a control algorithm is proposed to aim that the modules rendezvous at a prescribed point where the position of the point can be measured by only a few modules. In the second case, we propose a control algorithm without velocity measurements for the leaderless consensus of modular spacecraft. The modules rendezvous at a fixed point which is determined by the initial positions and the control gains of the modules. In both cases, passivity-based estimators are designed for the constraints that no velocity information is used.