Omnidirectional Aerial Vehicles With Unidirectional Thrusters: Theory, Optimal Design, and Control

Abstract

This paper presents a theoretical study on omnidirectional aerial vehicles with body-frame fixed unidirectional thrusters. Omniplus multi-rotor designs are defined as the ones that allow to exert a total wrench in any direction using positiveonly lift force and drag moment (i.e., positive rotational speed) for each rotor blade. Algebraic conditions for a design to be omniplus are derived, a simple necessary condition being the fact that at least seven propellers have to be used. An energy optimal design strategy is then defined as the one minimizing the maximum norm of the input set needed to span a certain wrench ellipsoid for the adopted input allocation strategy. Two corresponding major design criteria are then introduced: firstly, a minimum allocation-matrix condition number aims at an equal sharing of the effort needed to generate wrenches in any direction; secondly, imposing a balanced design guarantees an equal sharing of the extra effort needed to keep the input in the non-negative orthant. We propose a numerical algorithm to solve such optimal design problem and a control algorithm to control any omnidirectional platform. The work is concluded with informative simulation results in non-ideal conditions.

Development of SAM: cable-Suspended Aerial Manipulator

“…4) Propulsion units: the cable-suspended platform is equipped with 8 propulsion units to resist disturbances induced by the robotic manipulator and to stabilize its own dynamics. From previous research [23], [24], it has been shown that by installing propulsion units in the special arrangement (not collinear), an omnidirectional 6 DoF wrench can be realized 2 . More specifically, the body wrench w and the thrust input vector u can be related by allocation matrix 2 It would be worthwhile to mention that, the minimum required number of propulsion units to realize 6 DoF wrench equals 7.…”

“…Following the line of [24], to design the desirable propulsion unit arrangement, an optimization was carried out. In particular, the cost function to minimize was chosen as the condition number of the allocation matrix in order to guarantee the equal distribution between the propulsion units of the effort required to generate an omnidirectional wrench.…”

Passive Compliance Control of Aerial Manipulators

“…The authors are with Institute of Robotics and Mechatronics, German Aerospace Center (DLR), Wessling, Germany. E-mail: minjun.kim@dlr.de 1 In fact, fully actuated platforms are recently being studied [22], [23]. the interaction, the interaction force (or torque) propagates through the manipulator to the fuselage.…”

Fundamental Actuation Properties of Multirotors: Force–Moment Decoupling and Fail–Safe Robustness

“…Their high versatility allows their application field to range from exploration and mapping to grasping, from monitoring and surveillance to transportiation [1]- [4] Physical interaction for quadrotors has been enabled by theoretical tools such has, e.g., physical property reshaping [5] and external wrench estimation [6]. Nevertheless, the interest of robotic communities is now moving toward modeling, design and control of more complex multi-rotor platforms, where the number of propellers is larger than four [7]- [12]. Several hexarotor and octorotor vehicles have been recently presented for applications spanning from multi-agent cooperative manipulation (see, e.g., [13] and the references within) to human and environment interaction (see, e.g., [14]- [16]).…”