ODAR: Aerial Manipulation Platform Enabling Omnidirectional Wrench Generation

Abstract

We propose a novel aerial manipulation platform, an omnidirectional aerial robot, that is capable of omnidirectional wrench generation with opportunistically distributed/aligned Sectional rotors. To circumvent the tight thrust margin and weight budget of currently available rotor and battery technologies, we propose a novel design optimization framework, which maximizes the minimumguaranteed control force/torque for any attitude while incorporating such important and useful aspects as interrotor aerointerference, anisotropic task requirement, gravity compensation, etc. We also provide a closed-form solution of infinity-norm optimal control allocation to avoid rotor saturation with the tight thrust margin. Further, we elaborate the notion of electronic speed controller induced singularity and devise a novel selective mapping algorithm to substantially subdue its destabilizing effect. Experiments are performed to validate the theory, which demonstrate such capabilities not possible with typical aerial manipulation systems, namely, separate translation and attitude control on SE(3), hybrid pose/wrench control with downward force of 60 N much larger than its own weight (2.6 kg), and peg-inhole teleoperation with a radial tolerance of 0.5 mm.

Towards Efficient Full Pose Omnidirectionality with Overactuated MAVs

“…To remain in a thrust region that maintains a good linear approximation, and to reduce the risk of overheating, the maximum output of the rotors is limited to 80%, which corresponds with a thrust of 20 N for each double rotor unit. Using this test data, maximum achievable force and torque envelopes of the system can be determined by feeding commands forward through the allocation matrix (2). The resulting plots for maximum force and torque envelopes are shown in Figure 2(a).…”

Modeling and control of an overactuated aerial vehicle with four tiltable quadrotors attached by means of passive universal joints

“…The authors of [17] design a novel multirotor architecture by solving a technical optimization problem. Similarly, in [18] and [19], vehicle topology is optimized to achieve omnidirectional force and torque exertion by means of bidirectional propellers and [20] studies the theoretical conditions to develop omnidirectional vehicles based on unidirectional propellers with fixed tilting. The same approach can be applied to the collaborative transportation of objects: while attaching several quadrotors to a given payload in the same plane leads to underactuated dynamics [21], the introduction of fixed tilting angles makes the system overactuated [22].…”

Energy-Efficient Trajectory Generation for a Hexarotor with Dual- Tilting Propellers

“…Inspired by [14], [15], in this work we extend this formulation to a hexarotor whose propellers can be simultaneously tilted about two orthogonal axes via two servomotors (henceforth referred to as dual-tilting propellers). When compared to the complex design of the existing omnidirectional aerial robots with eight tilted reversible motors [16], [17], the dual-tilting mechanism offers greater flexibility since the underactuation degree of the vehicle can be easily adapted to the specific task at hand [14]. In particular, the hexarotor can be reconfigured in forward flight to behave as a fully-actuated platform and is capable of independently generating thrust and torque in any direction, which simplifies the execution of physical interaction tasks with the environment [18].…”

“…Under Assumption 1, we can finally introduce the following optimal control problem by combining (17) with system (18):…”