Contact-Constrained Hovering by Using Hybrid Force-Position Control Method for Multirotor UAVs in the Rugged Terrain

In rugged terrains, conventional multirotor unmanned aerial vehicles (UAVs) can only hover above the ground and are unable to land properly, making it difficult to accomplish tasks that demand high positional stability for smooth and precise payload delivery. To address this issue, this paper proposes a contact-constrained hovering control method, enabling the UAV to operate in a controlled state between hovering and landing. In this state, the rotors remain active while parts of the landing gear make contact with the terrain, utilizing the irregular surface as external support to adapt to rugged terrains and achieve higher positional stability than conventional hovering. Based on Hertzian contact mechanics and Coulomb friction theory, a contact force modeling framework is developed to accurately simulate the interaction between the UAV landing gear and the ground. Building upon this, a hybrid force–position controller is designed to regulate the contact force for stable interaction while maintaining positional accuracy. Simulation results demonstrate that the proposed method achieves stable contact-hovering control and, compared with traditional hovering, exhibits higher position control accuracy under external disturbances as well as improved energy efficiency during prolonged hovering.