This letter presents the design, modeling, and control of a multirotor for inspection of bridges with full contact. The letter analyzes the aerodynamic ceiling effect when the aerial robot approaches the bridge surface from below, including its aerodynamic characterization using computational fluid dynamics. The proposed multirotor design takes the modeled aerodynamic effects into account, improving the performance of the aerial platform terms of the stability and position accuracy during the inspection. Nonlinear attitude and position controllers to manage the aerodynamic effects are derived and tested. Finally, outdoor experiments in a real bridge inspection task have been used to validate the system, as well as, the controller and the aerodynamic characterization. The experiments carried out also include a complete autonomous mission of the aerial platform during a structural assessment application.

This paper presents the design, modeling and control of a fully actuated aerial robot for infrastructure contact inspection as well as its localization system. Health assessment of transport infrastructure involves measurements with sensors in contact with the bridge and tunnel surfaces and the installation of monitoring sensing devices at specific points. The design of the aerial robot presented in the paper includes a 3DoF lightweight arm with a sensorized passive joint which can measure the contact force to regulate the force applied with the sensor on the structure. The aerial platform has been designed with tilted propellers to be fully actuated, achieving independent attitude and position control. It also mounts a “docking gear” to establish full contact with the infrastructure during the inspection, minimizing the measurement errors derived from the motion of the aerial platform and allowing full contact with the surface regardless of its condition (smooth, rough, ...). The localization system of the aerial robot uses multi-sensor fusion of the measurements of a topographic laser sensor on the ground and a tracking camera and inertial sensors on-board the aerial robot, to be able to fly under the bridge deck or close to the bridge pillars where GNSS satellite signals are not available. The paper also presents the modeling and control of the aerial robot. Validation experiments of the localization system and the control system, and with the aerial robot inspecting a real bridge are also included.

This work introduces the G-Fly-Crane, a proof-of-concept aerial multi-robot system designed to demonstrate the advantage of using multiple aerial robots as a valuable tool for novel construction techniques, not requiring the use of heavy engines and costly infrastructures. We experimentally demonstrate its capability to perform pick-and-place and manipulation tasks in a construction scenario, with an increased payload capacity and dexterity compared to the single robot case. The system is composed of three aerial robots connected to a platform by three pairs of cables. The platform is equipped with a gripper, enabling the grasping of objects. The paper describes in detail the hardware and software architecture of our prototype and explains the implemented control methods. A shared control strategy incorporates the human operator in the control loop, thus increasing the overall system reliability when performing complex tasks. The paper also discusses the next steps required to bring this technology from indoor laboratory conditions to real-world applications.

We present the control in physical interaction with the environment of a Cable-suspended Aerial Multi-Robot Manipulator (CS-AMRM) called the Fly-Crane, composed of three aerial vehicles towed to a platform by means of six cables. The control strategy enables the system to accurately and safely perform tasks involving expected or unexpected interactions between the platform and the environment, in the absence of dedicated force/torque sensors. A previously developed Inverse Kinematic Controller (IKC) is enhanced with an admittance framework, and contacts are estimated through a generalized momentum-based observer. To assess the validity of our approach, and to provide practical insights into the method, we perform extensive experimental tests, comprehending the admittance property shaping to modulate stiffness, damping, and virtual mass, as well as experiments in a more realistic scenario involving contacts between the Fly-Crane and the environment.