Variable-stiffness Compliant Control of Aerial Manipulator for Sampling in Marsh Wetland Environments

A variable-stiffness compliant control framework is proposed for the issues of compliant manipulation and precise control of an aerial manipulator performing sampling tasks in marsh wetland environments. Firstly, a variable-stiffness admittance control method based on energy tank is designed to achieve compliant sampling by the aerial manipulator. Secondly, a boundary adaptive method is proposed that effectively resolves the issue of insufficient energy in the energy tank caused by variable-stiffness compliance, enhancing the safety of the aerial manipulator during the sampling process. Then, a disturbance observer and a pose controller are designed using the prescribed-time control method, improving the disturbance estimation and trajectory error convergence speed of the aerial manipulator. The stability of the proposed variable-stiffness compliant control framework is analyzed using passivity theory and Lyapunov tools. Finally, the compliance, safety, and stability of the variable-stiffness compliant control framework are verified through simulations and experiments.