@article{atay_bryant_buckner_2021, title={Control and Control Allocation for Bimodal, Rotary Wing, Rolling-Flying Vehicles}, volume={13}, ISSN={["1942-4310"]}, DOI={10.1115/1.4050998}, abstractNote={Abstract
               This paper presents a robust method for controlling the terrestrial motion of a bimodal multirotor vehicle that can roll and fly. Factors influencing the mobility and controllability of the vehicle are explored and compared to strictly flying multirotor vehicles; the differences motivate novel control and control allocation strategies that leverage the non-standard configuration of the bimodal design. A fifth-order dynamic model of the vehicle subject to kinematic rolling constraints is the basis for a nonlinear, multi-input, multi-output, sliding mode controller. Constrained optimization techniques are used to develop a novel control allocation strategy that minimizes power consumption while rolling. Simulations of the vehicle under closed-loop control are presented. A functional hardware embodiment of the vehicle is constructed onto which the controllers and control allocation algorithm are deployed. Experimental data of the vehicle under closed-loop control demonstrate good performance and robustness to parameter uncertainty. Data collected also demonstrate that the control allocation algorithm correctly determines a thrust-minimizing solution in real-time.}, number={5}, journal={JOURNAL OF MECHANISMS AND ROBOTICS-TRANSACTIONS OF THE ASME}, author={Atay, Stefan and Bryant, Matthew and Buckner, Gregory}, year={2021}, month={Oct} }
 @article{jenkins_atay_buckner_bryant_2021, title={Genetic Algorithm-Based Optimal Design of a Rolling-Flying Vehicle}, volume={13}, ISSN={["1942-4310"]}, DOI={10.1115/1.4050811}, abstractNote={Abstract
               This work describes a design optimization framework for a rolling-flying vehicle consisting of a conventional quadrotor configuration with passive wheels. For a baseline comparison, the optimization approach is also applied for a conventional (flight-only) quadrotor. Pareto-optimal vehicles with maximum range and minimum size are created using a hybrid multi-objective genetic algorithm in conjunction with multi-physics system models. A low Reynolds number blade element momentum theory aerodynamic model is used with a brushless DC motor model, a terramechanics model, and a vehicle dynamics model to simulate the vehicle range under any operating angle-of-attack and forward velocity. To understand the tradeoff between vehicle size and operating range, variations in Pareto-optimal designs are presented as functions of vehicle size. A sensitivity analysis is used to better understand the impact of deviating from the optimal vehicle design variables. This work builds on current approaches in quadrotor optimization by leveraging a variety of models and formulations from the literature and demonstrating the implementation of various design constraints. It also improves upon current ad hoc rolling-flying vehicle designs created in previous studies. Results show the importance of accounting for oft-neglected component constraints in the design of high-range quadrotor vehicles. The optimal vehicle mechanical configuration is shown to be independent of operating point, stressing the importance of a well-matched, optimized propulsion system. By emphasizing key constraints that affect the maximum and nominal vehicle operating points, an optimization framework is constructed that can be used for rolling-flying vehicles and conventional multi-rotors.}, number={5}, journal={JOURNAL OF MECHANISMS AND ROBOTICS-TRANSACTIONS OF THE ASME}, author={Jenkins, Tyler and Atay, Stefan and Buckner, Gregory and Bryant, Matthew}, year={2021}, month={Oct} }
 @article{atay_bryant_buckner_2021, title={The Spherical Rolling-Flying Vehicle: Dynamic Modeling and Control System Design}, volume={13}, ISSN={["1942-4310"]}, DOI={10.1115/1.4050831}, abstractNote={Abstract
               This paper presents the dynamic modeling and control of a bi-modal, multirotor vehicle that is capable of omnidirectional terrestrial rolling and multirotor flight. It focuses on the theoretical development of a terrestrial dynamic model and control systems, with experimental validation. The vehicle under consideration may roll along the ground to conserve power and extend endurance but may also fly to provide high mobility and maneuverability when necessary. The vehicle uses a three-axis gimbal system that decouples the rotor orientation from the vehicle’s terrestrial rolling motion. A dynamic model of the vehicle’s terrestrial motion is derived from first principles. The dynamic model becomes the basis for a nonlinear trajectory tracking control system suited to the architecture of the vehicle. The vehicle is over-actuated while rolling, and the additional degrees of actuation can be used to accomplish auxiliary objectives, such as power optimization and gimbal lock avoidance. Experiments with a hardware vehicle demonstrate the efficacy of the trajectory tracking control system.}, number={5}, journal={JOURNAL OF MECHANISMS AND ROBOTICS-TRANSACTIONS OF THE ASME}, author={Atay, Stefan and Bryant, Matthew and Buckner, Gregory}, year={2021}, month={Oct} }
 @article{atay_buckner_bryant_2020, title={Dynamic Modeling for Bi-Modal, Rotary Wing, Rolling-Flying Vehicles}, volume={142}, ISSN={["1528-9028"]}, DOI={10.1115/1.4047693}, abstractNote={Abstract
               This paper presents a rigorous analysis of a promising bi-modal multirotor vehicle that can roll and fly. This class of vehicle provides energetic and locomotive advantages over traditional unimodal vehicles. Despite superficial similarities to traditional multirotor vehicles, the dynamics of the vehicle analyzed herein differ substantially. This paper is the first to offer a complete and rigorous derivation, simulation, and validation of the vehicle's terrestrial rolling dynamics. Variational mechanics is used to develop a six degrees-of-freedom dynamic model of the vehicle subject to kinematic rolling constraints and various nonconservative forces. The resulting dynamic system is determined to be differentially flat and the flat outputs of the vehicle are derived. A functional hardware embodiment of the vehicle is constructed, from which empirical motion data are obtained via odometry and inertial sensing. A numerical simulation of the dynamic model is executed, which accurately predicts complex dynamic phenomena observed in the empirical data, such as gravitational and gyroscopic nonlinearities; the comparison of simulation results to empirical data validates the dynamic model.}, number={11}, journal={JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME}, author={Atay, Stefan and Buckner, Gregory and Bryant, Matthew}, year={2020}, month={Nov} }
 @article{atay_jenkins_buckner_bryant_2020, title={Energetic analysis and optimization of a bi-modal rolling-flying vehicle}, volume={4}, ISSN={["2366-598X"]}, DOI={10.1007/s41315-020-00119-2}, number={1}, journal={INTERNATIONAL JOURNAL OF INTELLIGENT ROBOTICS AND APPLICATIONS}, author={Atay, Stefan and Jenkins, Tyler and Buckner, Gregory and Bryant, Matthew}, year={2020}, month={Mar}, pages={3–20} }