This paper deals with aerial manipulators consisting of an unmanned aerial vehicle equipped with a robotic multi-link arm. The paper presents methods for the control of the aerial platform taking into account the motion of the arm. It shows how a Variable Parameter Integral Backstepping controller outperforms the results obtained by using PID controllers. The paper presents a quadrotor with a new arm designed for assembly tasks and the implementation of the proposed control methods. Simulations and outdoor experiments confirm the validity of the proposed approach.

This paper presents the design and control of a multirotor-based aerial manipulator developed for outdoor operation. The multi-rotor has eight rotors and large payload to integrate a 7-degrees of freedom arm and to carry sensors and processing hardware needed for outdoor positioning. The arm can also carry an end-effector and sensors to perform different missions. The paper focuses on the control design and implementation aspects. A stable backstepping-based controller for the multirotor that uses the coupled full dynamic model is proposed, and an admittance controller for the manipulator arm is outlined. Several experimental tests with the aerial manipulator are also presented. In one of the experiments, the performance of the pitch attitude controller is compared to a PID controller. Other experiments of the arm controller following an object with the camera are also presented.

This paper analyzes the ground effect in multirotors, that is, the change in the thrust generated by the rotors when flying close to the ground due to the interaction of the rotor airflow with the ground surface. This effect is well known in single-rotor helicopters but has been assumed erroneously to be similar for multirotors in many cases in the literature. In this paper, the ground effect for multirotors is characterized with experimental tests in several cases and the partial ground effect, a situation in which one or some of the rotors of the multirotor (but not all) are under the ground effect, is also characterized. The influence of the different cases of ground effect in multirotor control is then studied with several control approaches in simulation and validated with experiments in a test bench and with outdoor flights.

Dual-arm aerial manipulation requires the design and development of high performance robotic arms in terms of safety, robustness, and force/torque/impedance control, taking into account the integration in the aerial platform, the strong weight constraints, and the technological limitations of the servo actuators. A compliant joint arm also improves the response of the aerial manipulator to collisions and external forces during the flight operation. This letter evaluates the control capabilities in a lightweight manipulator built with smart servo actuators and a spring-lever transmission mechanism that provides joint compliance and deflection measurement. The dynamic model of a compliant joint is validated through frequency identification, demonstrating how virtual variable impedance can be achieved without a second motor. Mechanical joint compliance is the base of the Cartesian impedance control scheme of the dual-arm system, integrated with the controller of the aerial platform. A stereo vision system provides the Cartesian deflection of the end effector, derived from the definition of an equivalent stiff joint manipulator, allowing the estimation and control of the contact forces. Experimental results validate the developed concepts.