Han Wopereis

Mechanism for perching on smooth surfaces using aerial impacts

One important issue of multirotor UAVs is their limited operational time due to their high power consumption. This issue may hinder the application of aerial robots for security purposes as their flight endurance can be exploited for just a finite amount of time, which is not necessarily sufficient in realistic surveillance scenarios. In order to achieve long endurance missions with multirotor UAVs, e.g. for crowd-surveillance, it can be beneficial to perch the UAV while it is operative to increase the operation time. This work presents an aerial manipulator that allows for reliable and reversible perching of multirotor UAVs on smooth vertical surfaces, using a lightweight mechanism based on passive vacuum-cup technology and the absorption of aerial impacts. This contributes towards enabling drones to become more flexible security systems for long endurance missions, as it allows them to position themselves passively in the environment. In this work, the design of the aerial perching mechanism is presented, as well as the perching strategy performed to achieve reliable perching. Experimental results demonstrate the relevant capabilities of the system for a drone weighing approximately 1.8 kg, including stable perching on the environment, disarming the rotors and reliable take-off.

Application of substantial and sustained force to vertical surfaces using a quadrotor

In the field of aerial robotics, one of the key challenges is to enable aerial manipulators to exert substantial forces on the environment. Enabling this will allow the technology to perform meaningful tasks airborne, such as cleaning or grinding surfaces. While in contact and applying a large, continuous force, control of the UAVs attitude is a challenge. In this work, we show that a regular (PID-based) attitude controller is incapable of stabilizing aerial manipulators that apply physical contact forces on the environment that are comparable to the UAVs weight. We present a novel control algorithm that uses an LQR-optimized state feedback on the roll and yaw angle while in contact. Experiments on a UAV of 1.5 kg show that the proposed controller is capable of applying a contact force of over 15 N — equal to the UAVs weight — sustained for several minutes.

Multimodal Aerial Locomotion : An Approach to Active Tool Handling 10 Author

The research focus in aerial robotics is shifting from contactless inspection toward interaction and manipulation, with the number of potential applications rapidly increasing [1]. Eventually, aerial manipulators, i.e., unmanned aerial vehicles (UAVs) equipped with manipulators, will likely take on hazardous maintenance tasks now performed by humans. For this to happen, aerial manipulators must be able to perform all the different operations required in these maintenance routines.

Autonomous and sustained perching of multirotor platforms on smooth surfaces

Due to their high dexterity and maneuverability, multirotors represent a huge potential for the use in surveillance and crowd-monitoring applications. Unfortunately, one of the main issues of this class of UAVs is their high power consumption, which severely limits their operating time. This yields their application in many surveillance applications impractical as these often imply prolonged missions. Prior steps were made to increase the operating time by the design of an aerial manipulator that enables these multirotors to perch onto smooth surfaces, allowing to disable the rotors, thereby circumventing the problem of limited flight time. This method, based on passive vacuum cups, demonstrated to be effective but lacks any form of automation or failure prevention. This work extends the previous work by automating the perching procedure and by implementing methods to prevent failure. Experiments have validated the approach, demonstrating the capability of the system to remain airborne for over 45 minutes, while only running the rotors for less than 3 minutes in that time period.

A Novel Approach To Surface Operations With Multirotor UAVs

This video shows the indoor experimental evaluation of our latest aerial manipulation system which is capable of brushing surfaces. This is enabled by means of two innovations. The first innovation is a special tool that ‘drives’ over the surface using the friction generated by the interaction forces, while simultaneously applying a tool (here a brush) with a constant force on the surface using a spring. The second innovation is in the control theory, which stabilizes the UAV while allowing this movement. The experiment in the video shows how these innovations are applied to clean a patch on a surface, and is the validation step of the system before working on moving it outdoors towards the realistic scenario.

A comparison of control approaches for aerial manipulators handling physical impacts

This paper presents and compares different control strategies for aerial manipulators to handle highly dynamic physical interaction with the environment. These control strategies are compared in simulation utilizing an ideal model developed using the bond graph representation. Simulation results are presented to demonstrate the effectiveness of and the differences between the proposed solutions.

Bilateral human-robot control for semi-autonomous UAV navigation

This paper proposes a semi-autonomous bilateral control architecture for unmanned aerial vehicles. During autonomous navigation, a human operator is allowed to assist the autonomous controller of the vehicle by actively changing its navigation parameters to assist it in critical situations, such as navigating through narrow paths. The overall goal of the controller is to combine the stability and precision of an autonomous control with the cognitive abilities of a human operator, only when strictly required for the accomplishment of a task. The control architecture has been validated through simulations and experiments.

Vision-IMU based collaborative control of a blind UAV

Position estimation of UAVs is usually done using onboard sensors such as GPS and camera. However, in certain practical situations, the measurements of both the GPS and the onboard camera of the UAV might not always be available or reliable. This paper investigates the possibility to overcome situations in which a UAV is blind, i.e. situations in which its onboard position sensors and estimates fail, by utilizing vision data from an external UAV. The paper demonstrates that by means of a collaborative approach, aimed at fusing information of multiple aerial vehicles, it is still possible to control the position of an UAV with onboard sensor fail. The method makes use of vision measurements from an external UAV in combination with the on-board IMU measurements of the main UAV to create a reliable position estimate. Indoor experiments demonstrate that position control is possible using this estimate.