On-site inspection of large-scale infrastructure often involves high risks for the operators and high insurance costs. Despite several safety measures already in place to avoid accidents, an increasing concern has brought the need to remotely monitor hard-to-reach locations, for which the use of aerial robots able to interact with the environment has arisen. In this paper a novel approach to aerial manipulation is presented, where a compact manipulator with a single degree-of-freedom is tailored for the placement and retrieval of sensors in the environment. The proposed design integrates on-board sensing, a high-performance force controller on the manipulator, and a thrust-to-force mapping on the flight controller. Experimental results demonstrate the high reliability achieved during both placement and retrieval tasks on flat surfaces (e.g., a bridge wall) and cylindrical surfaces (e.g., tree trunks). A total number of 89 flight experiments were carried out to demonstrate the robustness and potential of the compact, bespoke aerial design.

A wide range of applications for which unmanned aerial vehicles (UAVs) are ideally suited rely on the development of manipulators capable of exchanging forces with the environment. One such application is the installation and retrieval of intelligent sensors for monitoring wide-spread areas and locations that are difficult to access by any other means. Within this letter, we report on both indoor and outdoor flights tests of a novel force controlled lightweight compliant manipulator that allows a UAV to carry out this type of task. Installation and retrieval are both demonstrated with different scenarios, indoors and outdoors. Key results include interaction forces up to 22 N exerted by a small-sized multirotor, placement and retrieval operations carried out on flat as well as cylindrical surfaces, and an analysis of the overall system. The results of multiple flight experiments clearly demonstrate the potential of this approach for the deployment of sensors and other force-related tasks.

In this paper a force controller via energy tanks is implemented for novel applications in aerial contour follow. This control approach allows the aerial vehicle to trace out a boundary whilst in continuous contact with a surface by means of an actively compliant manipulator. This represents the first step towards tactile-based aerial navigation, which can be used to complement more traditional mapping approaches such as visual SLAM. Key results show that the energy-based approach can be used to apply a continuous shear force through the manipulator while the vehicle remains in contact with the surface of interest. Results also show the robustness and repeatability of this approach for prolonged aerial interaction, and the potential for future use in more complex, un-modeled environments.

Manipulation has been a major topic in robotics since its earlier developments. In the last few years, a new research area has focused in the introduction of manipulation capabilities on mobile robots. Several challenges are faced when mobile robots interact with unknown environments, for which inherent compliance is a key feature to achieve the intended outcome in a safe and robust way. This paper proposes a unified method of force control with energy-tank based methods to tackle 3D contour following. This method is tailored for manipulators that are designed for aerial applications, and addresses the interaction with unknown surfaces by also tackling the safety aspect, i.e. the response generated during contact loss.

This paper presents simulation and airborne test results for a quadrotor equipped with an actively-variable compliance manipulator for contact interaction. Typical applications of this type of manipulator might include sensor placement operations and non-destructive testing. It is shown that through the use of the proposed manipulator, the force experienced at the end-effector can be adaptively controlled, and the effect of interactions on the aircraft itself minimised. Simulation and airborne results show a consistent correlation between the peak loads experienced at the end-effector and the actuator gains. A lightweight, adaptively-compliant actuator of this type offers the opportunity not only to tailor different demanded forces at the end-effector, but also to shape the loads applied - effects which can be achieved by changing only the software structure and tuning of the actuator control system.

As roles for unmanned aerial vehicles (UAVs)continue to diversify, the ability to sense and interact closely with the environment becomes increasingly important. Within this paper we report on the initial flight tests of a novel adaptively compliant actuator which will allow a UAV to carry out such tasks as the 'pick and placement' of remote sensors, structural testing and contact-based inspection. Three key results are discussed and presented; the ability to physically apply forces with the UAV through the use of an active compliant manipulator; the ability to tailor these forces through tuning of the manipulator controller gains; and the ability to apply a rapid series of physical pulses in order to excite remotely placed sensors, e.g. vibration sensors. A series of over sixty flight tests have been used to generate initial results which clearly demonstrate the potential of this new type of compliant aerial actuator.