A Novel Center-of-Mass Displacing Aerial Manipulation Platform: Design, Modeling, and Control

Aerial manipulators can serve contact-based industrial applications, where fundamental tasks like drilling and grinding often necessitate aerial platforms to handle heavy tools and high loads (i.e., forces and torques). These tasks are frequently performed on non-horizontal surfaces. Current multirotor platforms, which have a fixed CoM (Center of Mass) within the rotor-defined area, typically exhibit a large moment arm between the EE (End-Effector) tip and the system's CoM. This configuration can result in instability and potential damage during physical interactions. In this letter, we present the system design, modeling, and control of a novel aerial vehicle tailored to tool manipulation on non-horizontal surfaces. This platform adapts the form of an H-shaped coaxial octocopter with tiltable back rotors; it can carry heavy components (e.g., the manipulator and battery) on a movable plate within the rotor-defined area during free flight. When interacting with surfaces, the platform actively shifts the plate toward the work surface while preserving the system orientation thanks to the tiltable back rotors. This leads to a displaced CoM location and a reduced moment arm. We use simulations that closely capture the built physical prototype to validate our proposed concepts for complex and risky working scenarios. Moreover, early-stage physical experiments were conducted to evaluate the developed system for free flights and a pushing task.