Impact-Aware Planning and Control for Aerial Robots with Suspended Payloads

A quadrotor with a cable-suspended payload imposes great challenges in impact-aware planning and control. This joint system has dual motion modes, depending on whether the cable is slack or not, and presents complicated dynamics. Therefore, gen- erating feasible agile flight while preserving the retractable nature of the cable is still a challenging task. In this article, we propose a novel impact-aware planning and control framework that resolves potential impacts caused by motion mode switching. Our method leverages the augmented Lagrangian method to solve an optimiza- tion problem with nonlinear complementarity constraints, which ensures trajectory feasibility with high accuracy while maintaining efficiency. We further propose a hybrid nonlinear model predictive control method to address the model mismatch issue in agile flight. Our methods have been comprehensively validated in both simula- tion and experiments, demonstrating superior performance com- pared to existing approaches. To the best of our knowledge, we are the first to successfully perform automatic multiple motion mode switching for aerial payload systems in real-world experiments.