Fundamental Research


Current multi-rotor designs typically arrange their propellers in the same plane, or with a small radially-symmetric inward tilt, in order to provide efficient vertical thrust. This results in an under-actuated system that must roll and pitch in order to move laterally. Others have proposed and examined the benefits of configuring a 6-rotor airframe with tilted rotors such that thrust can be directly applied parallel to the ground, eliminating the need to roll or pitch. Existing investigations into such 6 degree-of-freedom control strategies begin with a rotor layout and orientations before analyzing the resulting performance.

This BeagleBone Micro Aerial Vehicle (BeagleMAV) platform instead, presents a method to find the optimum rotor orientations that maximize desired performance characteristics for given airframe parameters such as mass and motor characteristics. As part of the optimization process, the multi-rotor’s mixing matrix is calculated and used in the proposed performance metric describing the resulting multi-rotor’s available control authority in realistic situations [1][2].

A set of techniques to systematically analyze and design the monocoque airframe of this hexrotor UAV system is also developed [3], starting from parametric analyses and testing of the off-the-shelf motors and propellers for selection [4], and then the thruster axes orientations are canted and further optimized for achieving the capability of in-plane maneuverability and direct decoupled 6DOF control [2].

The landing and perching related mechanism and controls design is also of great interest in terms of the BeagleMAV’s application in search and rescue and sensor deployment in the post-disaster scenario with confined spaces and uneven surfaces. A novel soft-robotic gripper design is being developed and will be presented in the future publications, which integrates both the features of contact-driven deformation and tendon-driven actuation [5]. The gripper consists of one or two pairs of tendon-driven compliant fingers, each pair equipped with a tendon winch driven by a servo motor, and a base plate to connect the gripper system to the vehicle main body. With its novel finger design, the gripper can grasp objects with various shapes and sizes with sub-second (~0.8s) actuation and can support loads of up to 20 N with a pair of fingers with its total weight of less than 100 g.

This work was supported by the National Institute for Standards and Technology (NIST) under award #70NANB17H21, ”Improving Disaster Resilience Through Scientific Data Collection with UAV Swarms,” and the National Science Foundation (NSF) under award #DGE-0966375, ”Training, Research and Education in Engineering for Cultural Heritage Diagnostics.” Additional support was provided by the NSF under award #CNS-1338192, ”MRI: Development of Advanced Visualization Instrumentation for the Collaborative Exploration of Big Data,” as well as the Kinsella Heritage Engineering Fund and the Qualcomm Institute at UC San Diego. Opinions, findings, and conclusions from this study are those of the authors and do not necessarily reflect the opinions of the research sponsors.

[1] Strawson, J. R. (2018). Feedback Control Driven Mechanical Design Optimization (Doctoral dissertation, UC San Diego).

[2] Strawson, J., Cao, P., Bewley, T., Kuester, F. (2021) Rotor Orientation Optimization for Direct 6 Degree of Freedom Control of Multirotors. In 42nd IEEE Aerospace Conference (manuscript submitted for publication)

[3] Strawson, J., Tran, D,. Cao, P., Bewley, T., Kuester, F. (2021) Monocoque Multirotor Airframe Design with Rotor Orientations Optimized for Direct 6 DoF Control. In 42nd IEEE Aerospace Conference (manuscript submitted for publication)

[4] Cao, P., Strawson, J. (2018) Motor Propeller Testing. [Online]. Available:

 [5] Cao, P., Bewley, T., Kuester, F. (2021) A Multi-Purpose Soft-Robotic Gripper with Grasping Reliability and Impact Absorption. In 42ndIEEE Aerospace Conference (manuscript submitted for publication)