  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.
