Mechanical Design, Modelling and Control of a Novel Aerial Manipulator

In this paper a novel aerial manipulation system is proposed. The mechanical structure of the system, the number of thrusters and their geometry will be derived from technical optimization problems. The aforementioned problems are defined by taking into consideration the desired actuation forces and torques applied to the end-effector of the system. The framework of the proposed system is designed in a CAD Package in order to evaluate the system parameter values. Following this, the kinematic and dynamic models are developed and an adaptive backstepping controller is designed aiming to control the exact position and orientation of the end-effector in the Cartesian space. Finally, the performance of the system is demonstrated through a simulation study, where a manipulation task scenario is investigated.Comment: Comments: 8 Pages, 2015 IEEE International Conference on Robotics and Automation (ICRA '15), Seattle, WA, US

Design, Modeling, and Geometric Control on SE(3) of a Fully-Actuated Hexarotor for Aerial Interaction

In this work we present the optimization-based design and control of a fully-actuated omnidirectional hexarotor. The tilt angles of the propellers are designed by maximizing the control wrench applied by the propellers. This maximizes (a) the agility of the UAV, (b) the maximum payload the UAV can hover with at any orientation, and (c) the interaction wrench that the UAV can apply to the environment in physical contact. It is shown that only axial tilting of the propellers with respect to the UAV's body yields optimal results. Unlike the conventional hexarotor, the proposed hexarotor can generate at least 1.9 times the maximum thrust of one rotor in any direction, in addition to the higher control torque around the vehicle's upward axis. A geometric controller on SE(3) is proposed for the trajectory tracking problem for the class of fully actuated UAVs. The proposed controller avoids singularities and complexities that arise when using local parametrizations, in addition to being invariant to a change of inertial coordinate frame. The performance of the controller is validated in simulation.Comment: 9 pages, 9 figures, ICRA201

Suspended Load Path Tracking Control Using a Tilt-rotor UAV Based on Zonotopic State Estimation

This work addresses the problem of path tracking control of a suspended load using a tilt-rotor UAV. The main challenge in controlling this kind of system arises from the dynamic behavior imposed by the load, which is usually coupled to the UAV by means of a rope, adding unactuated degrees of freedom to the whole system. Furthermore, to perform the load transportation it is often needed the knowledge of the load position to accomplish the task. Since available sensors are commonly embedded in the mobile platform, information on the load position may not be directly available. To solve this problem in this work, initially, the kinematics of the multi-body mechanical system are formulated from the load's perspective, from which a detailed dynamic model is derived using the Euler-Lagrange approach, yielding a highly coupled, nonlinear state-space representation of the system, affine in the inputs, with the load's position and orientation directly represented by state variables. A zonotopic state estimator is proposed to solve the problem of estimating the load position and orientation, which is formulated based on sensors located at the aircraft, with different sampling times, and unknown-but-bounded measurement noise. To solve the path tracking problem, a discrete-time mixed $\mathcal{H}_2/\mathcal{H}_\infty$ controller with pole-placement constraints is designed with guaranteed time-response properties and robust to unmodeled dynamics, parametric uncertainties, and external disturbances. Results from numerical experiments, performed in a platform based on the Gazebo simulator and on a Computer Aided Design (CAD) model of the system, are presented to corroborate the performance of the zonotopic state estimator along with the designed controller

Visual servoing of aerial manipulators

The final publication is available at link.springer.comThis chapter describes the classical techniques to control an aerial manipulator by means of visual information and presents an uncalibrated image-based visual servo method to drive the aerial vehicle. The proposed technique has the advantage that it contains mild assumptions about the principal point and skew values of the camera, and it does not require prior knowledge of the focal length, in contrast to traditional image-based approaches.Peer ReviewedPostprint (author's final draft

Multi-rotor Aerial Vehicles in Physical Interactions: A Survey

Research on Multi-rotor Aerial Vehicles (MAVs) has experienced remarkable advancements over the past two decades, propelling the field forward at an accelerated pace. Through the implementation of motion control and the integration of specialized mechanisms, researchers have unlocked the potential of MAVs to perform a wide range of tasks in diverse scenarios. Notably, the literature has highlighted the distinctive attributes of MAVs that endow them with a competitive edge in physical interaction when compared to other robotic systems. In this survey, we present a categorization of the various types of physical interactions in which MAVs are involved, supported by comprehensive case studies. We examine the approaches employed by researchers to address different challenges using MAVs and their applications, including the development of different types of controllers to handle uncertainties inherent in these interactions. By conducting a thorough analysis of the strengths and limitations associated with different methodologies, as well as engaging in discussions about potential enhancements, this survey aims to illuminate the path for future research focusing on MAVs with high actuation capabilities

Cooperative aerial manipulation with force control and attitude stabilization

Ranging from autonomous flying cars, fixed wing and rotorcraft UAVs, there has been a tremendous interest in aerial robotics over the last decade. This thesis presents contributions to the state-of-art in cooperative payload transport with force synthesis and dynamic interaction using quadcopter UAVs. In this report, we consider multiple quadcopter aerial robots and develop decentralized force controller for them to manipulate a payload. We use quadcopters with a rigid link attached to it to collaboratively manipulate the payload. We develop a dynamic model of the payload for both point mass and rigid body cases. We model the contact force between the agents and the payload as a mass spring model. This assumption is valid when the vehicles are connected to the payload via elastic cables or when the payload is flexible or surrounded by elastic bumper materials. We also extend our aerial manipulation system to a multi-link arm attached to the quadcopter.We develop an adaptive decentralized control law for transporting a payload of unknown mass without explicit communication between the agents. Our controller ensures that all quadcopters and the payload asymptotically converges to a constant reference velocity. It also ensures that all of the forces applied to the payload converges to desired set-points. Desired thrusts and attitude angles are computed from the control algorithms and a low-level PD controller is implemented to track the desired commands for each quadcopter. The sum of the estimates of the unknown mass from all the agents converge to the true mass. We also employ a consensus algorithm based on connected graphs to ensure that each agent gets an equal share of the payload mass. Furthermore, we develop an orientation control algorithm that guarantees attitude stabilization of the payload. In particular, we develop time varying force set-points to enforce attitude regulation without any moment inputs from the quadcopters