Adaptive Optimal Control of Space Tether System for Payload Capture via Policy Iteration

The libration control problem of space tether system(STS) for post-capture of payload is studied. The process of payload capture will cause tether swing and deviation from the nominal position, resulting in the failure of capture mission. Due to unknown inertial parameters after capturing the payload, an adaptive optimal control based on policy iteration is developed to stabilize the uncertain dynamic system in the post-capture phase. By introducing integral reinforcement learning (IRL) scheme, the algebraic Riccati equation (ARE) can be online solved without known dynamics. To avoid computational burden from iteration equations, the online implementation of policy iteration algorithm is provided by the least-squares solution method. Finally, the effectiveness of the algorithm is validated by numerical simulations.