  Achieving cooperative transportation by teams of aerial robots has been
attracting attention owing to its flexibility with respect to payloads and
robustness against failures. In this paper, we propose a flexible decentralized
controller for the number of robots and the shapes of payloads in a cooperative
transport task using multiple single-rotor robots. Our controller is robust to
mass and center of mass fluctuations and robot failures. Moreover, asymptotic
stability against dynamics errors is guaranteed. Additionally, the controller
supports heterogeneous single-rotor robots. Thus, robots with different
specifications and deterioration can be effectively utilized for cooperative
transportation. In particular, this performance is effective for robot reuse.
To achieve the aforementioned performance, the controller consists of a
parallel structure comprising two controllers: a feedback controller, which
renders the system strictly positive real, and nonlinear controller, which
renders the object asymptotic to the target. First, we confirm cooperative
transportation using 8 and 10 robots for two shapes via numerical simulation.
Subsequently, the cooperative transportation of a rectangle payload (with a
weight of approximately 3 kg and maximum length of 1.6 m) is demonstrated using
a robot team consisting of three types of robots, even under robot failure and
center of mass fluctuation.
