Interest in multilift rotorcraft systems has reemerged in recent years to overcome some of the problems in single unmanned aerial vehicle handling and delivery systems. Using multiple unmanned ...rotorcrafts (URs), the load weight can be evenly distributed among the vehicles, extending the flight time and therefore increasing the working distance of such systems. Moreover, with a slung-load configuration, bigger size packages with complex shape and equipment that may interfere with the onboard electronics can be carried. In this context, this article presents a payload-based unified motion control that allows any number of URs to cooperatively transport a slung load in forward flight. The motion control comprises path-following and trajectory-tracking algorithms, considers obstacle avoidance, implements a specific strategy for load weight distribution (load equalization) by regulating the relative altitude of each UR, and is robust to disturbances such as wind. In addition, this work shows that load equalization is essential for slung-load cooperative transport, especially in forward flight. The controller's stability is analytically studied and the good performance of the system is demonstrated through exhaustive simulations using validated dynamic models for mini-helicopters, cables, and payload. Finally, the relation between load weight and number of URs is analyzed by considering several scenarios.
Accurate trajectory tracking is a critical property of unmanned aerial vehicles (UAVs) due to system nonlinearities, under-actuated properties and constraints. Specifically, the use of unmanned ...rotorcrafts with accuracy trajectory tracking controllers in dynamic environments has the potential to improve the fields of environment monitoring, safety, search and rescue, border surveillance, geology and mining, agriculture industry, and traffic control. Monitoring operations in dynamic environments produce significant complications with respect to accuracy and obstacles in the surrounding environment and, in many cases, it is difficult to perform even with state-of-the-art controllers. This work presents a nonlinear model predictive control (NMPC) with collision avoidance for hexacopters’ trajectory tracking in dynamic environments, as well as shows a comparative study between the accuracies of the Euler–Lagrange formulation and the dynamic mode decomposition (DMD) models in order to find the precise representation of the system dynamics. The proposed controller includes limits on the maneuverability velocities, system dynamics, obstacles and the tracking error in the optimization control problem (OCP). In order to show the good performance of this control proposal, computational simulations and real experiments were carried out using a six rotary-wind unmanned aerial vehicle (hexacopter—DJI MATRICE 600). The experimental results prove the good performance of the predictive scheme and its ability to regenerate the optimal control policy. Simulation results expand the proposed controller in simulating highly dynamic environments that showing the scalability of the controller.
A novel kinematic formation controller based on null-space theory is proposed to transport a cable-suspended payload with two rotorcraft UAVs considering collision avoidance, wind perturbations, and ...properly distribution of the load weight. An accurate 6-DoF nonlinear dynamic model of a helicopter and models for flexible cables and payload are included to test the proposal in a realistic scenario. System stability is demonstrated using Lyapunov theory and several simulation results show the good performance of the approach.
•It is proposed a multi-objective control for cooperative payload transport with rotorcraft UAVs based on null-space theory.•The proposal allows to set on-line the load weight that each vehicle must transport.•Strategies to avoid conflicts of interest between objectives are proposed.•Accurate dynamic models for helicopters, flexible cables and payload are used to test the proposal in a realistic scenario.•System stability is proven using Lyapunov theory and several simulation results show the good performance of the approach.
This paper considers the cooperative transport problem of a cable-suspended rigid bar with two rotorcraft UAVs considering collision avoidance, weight distribution, and wind perturbations. The ...proposal is based on null-space theory and includes a landing stage where the load is settled down on a formation of ground robots. Therefore, a variable formation is considered according to the task phase. In order to simulate the proposal in a realistic environment, very complete dynamic models for UAVs, ground robots, and load are considered. An adaptation stage is incorporated to link the control actions with the inputs required by the dynamic models. Theoretical bounds for the errors are studied under the assumption that perfect velocity tracking is not fulfilled.
This paper develops a trajectory tracking control design algorithm to be applied in unmanned aerial vehicles (UAVs). The strategy is simple but effective and it is based on linear algebra theory. The ...proposed approach reforms the column space of a system of linear equations at each sampling time to ensure the tracking objective when environmental disturbances appear. This new formulation ensures a uniform signal without affecting the error convergence to zero (demonstration available), which is one of the main contributions of this work. A statistical method is used to tune the system control minimizing a pre-defined cost function. In addition, the convergence to zero of the tracking errors is demonstrated in this work. Finally, the controller’s effectiveness is tested through several simulations in realistic test scenarios in the presence of disturbances.
•The trajectory tracking control in UAV under uncertainties is addressed.•The controller design for trajectory tracking is based on linear algebra.•The approach is applied in a nonlinear system with additive uncertainty.•The zero convergence of tracking error under polynomial uncertainties is demonstrated.•Several simulations in realistic scenarios were performed.
Transport, rescue, search, surveillance, and disaster relief tasks are some applications that can be developed with unmanned aerial vehicles (UAVs), where accurate trajectory tracking is a crucial ...property to operate in a cluttered environment or under uncertainties. However, this is challenging due to high nonlinear dynamics, system constraints, and uncertainties presented in cluttered environments. Hence, uncertainties in the form of unmodeled dynamics, aerodynamic effects, and external disturbances such as wind can produce unstable feedback control schemes, introducing significant positional tracking errors. This work presents a detailed comparative study between controllers such as nonlinear model predictive control (NMPC) and non-predictive baseline feedback controllers, with particular attention to tracking accuracy and computational efficiency. The development of the non-predictive feedback controller schemes was divided into inverse differential kinematics and inverse dynamic compensation of the aerial vehicle. The design of the two controllers uses the mathematical model of UAV and nonlinear control theory, guaranteeing a low computational cost and an asymptotically stable algorithm. The NMPC formulation was developed considering system constraints, where the simplified dynamic model was included; additionally, the boundaries in control actions and a candidate Lyapunov function guarantees the stability of the control structure. Finally, this work uses the commercial simulator DJI brand and DJI Matrice 100 UAV in real-world experiments, where the NMPC shows a reduction in tracking error, indicating the advantages of this formulation.
Recent technological advances have brought increased attention to aerial robotic manipulators (ARMs), particularly in applications involving physical interactions. However, translating control ...algorithms into real-world applications for aerial robotic manipulators may prove challenging, given the potential for accidents and the time-consuming nature of experiments; furthermore, the acquisition of aerial robotic manipulators could impose a substantial financial burden on universities, research centers, and companies. Therefore, this work addresses these issues by developing an open access platform to simulate aerial robotic manipulators and test control strategies. The presented simulator is based on the kinematics and dynamics of the Matrice-100 aerial platform equipped with a 3 DOF robotic arm, where the mathematical formulationwas developed using the Euler-Lagrange formalism. In addition, optimization techniques were used to perform the parameter identification procedure, ensuring the development of an accurate model for the open-access platform. The simulator platform is built upon the integration of Python, the Robot Operating System (ROS), and Unity 3D. These components collaborate to describe and demonstrate the behavior of the aerial robotic manipulator during the test process of control system algorithms. Simple tests were conducted to validate the open-access simulator platform. The proposed approach ensures the evaluation, testing of control strategies, and the ability to conduct experiments before hardware implementations. Finally, the proposal was published as an open source platform available in the following Code.
This paper deals with the problem of marine vessels trajectory tracking control in presence of environmental disturbances. In order to achieve this objective, a previously published methodology for ...controllers design was improved. A new model error estimation based scheme is proposed to reduce the effect of the perturbations in the tracking error. The approach is effective and low complexity thanks to uncertainty estimation based on numerical method theory. This modification ensures the tracking error convergence to zero, even in presence of polynomial uncertainties (demonstration available). Different tests are presents and a performance comparison with the previous controller is shown to highlight improvements of up to 29%. The control methodology is developed in discrete time, however, is validated by numerical simulations using a continuous time model.
•The trajectory tracking control in marine vessel under uncertainties is addressed.•The controller design for trajectory tracking is based on linear algebra.•The approach is applied in a nonlinear system with additive uncertainty.•Zero convergence of tracking error under polynomial uncertainties is demonstrated.•Simulations under modeling errors and disturbance in control actions are performed.
Nowadays, the energetic cost of flying in electric-powered UAVs is one of the key challenges. The continuous evolution of electrical energy storage sources is overcome by the great amount of energy ...required by the propulsion system. Therefore, the on-board energy is a crucial factor that needs to be further analyzed. In this work, different control strategies applied to a generic UAV propulsion system are considered and a lithium polymer battery dynamic model is included as the propulsion system energy source. Several simulations are carried out for each control strategy, and a quantitative evaluation of the influence of each control law over the actual energy consumed by the propulsion system is reported. This energy, which is delivery by the battery, is next compared against a well-known control-effort-based index. The results and analysis suggest that conclusions regarding energy savings based on control effort signals should be drawn carefully, because they do not directly represent the actual consumed energy.
•IFour different control strategies are applied to a generic UAV propulsion system•A lithium polymer battery dynamic model is considered as system energy source•Two saving scores are used to compare the actual energy savings•Controllers are analyzed according to energy savings, control effort and performance•Results suggest that conclusions regarding energy savings should be drawn carefully
A substantial interest in aerial robots has grown in recent years. However, the energetic cost of flying is one of the key challenges nowadays. Rotorcrafts are heavier-than-air flying machines that ...use lift generated by one or several rotors (vertically oriented propellers), and because of this, they spend a large proportion of their available energy to maintain their own weight in the air. In this brief, this concept is used to evaluate the relationship between navigation speed and energy consumption in a miniature quadrotor helicopter, which travels over a desired path. A novel path-following controller is proposed in which the speed of the rotorcraft is a dynamic profile that varies with the geometric requirements of the desired path. The stability of the control law is proved using the Lyapunov theory. The experimental results using a real quadrotor show the good performance of the proposed controller, and the percentages of involved energy are quantified using a model of a lithium polymer battery that was previously identified.
