1,720,969 research outputs found
Design of an Innovative Spraying System for High Precision Aerial Dispersion in Vineyards
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Artificial Potential Field and Sliding Mode Strategies for Rendezvous Maneuver and Obstacle Avoidance
No full textSliding Mode Control Techniques and Artificial Potential Field for Dynamic Collision Avoidance in Rendezvous Maneuvers
No full textDesign and Stability Analysis of an Agricultural Sprayer UAS Integrated with an Anti-Sloshing Tank
No full textThe efficiency of the precision spraying application employing Unmanned Aircraft Systems (UAS) is significantly influenced by disturbances that impact the system, consequently affecting trajectory accuracy. For this purpose, a hexagonal tank with a capacity of 10 L, featuring two perforated plates, has emerged as the most optimal solution for UAS with an MTOW of 25 kg, aimed at minimizing the adverse effect of liquid sloshing. Computational Fluid Dynamics (CFD) analysis is conducted using SolidWorks Flow Simulation software.
In order to identify the forces and moments acting inside the tank and their impact on UAS dynamics, a simulated scenario involving a sudden change in flight path is employed. The results show that the introduction of perforated plates, combined with the control system's work, effectively mitigates fluid motion, leading to improvements in trajectory tracking, spray performance, and overall safety
High-Order Sliding Mode Control for the Test Mass stabilization of the LISA MIssion: preliminary results
Full text linkThe main objective of this paper is the design of a controller for the test mass release of the
Laser Interferometer Space Antenna (LISA) mission. Since the test masses are used as sensors
in the science phase for environmental measurements, the control system can be able to robustly
deal with large initial deviations of the release mechanism. Moreover, the control system should
be able to maintain and stabilize the test masses with a precision. For this reason, two Sliding
Mode Control (SMC) are included in this study. A second-order SMC is mainly proposed for this
critical phase, which is able to handle uncertainties and noise introduced by the sensors system.
This controller is compared with a first-order SMC, which was used in LISA Pathfinder mission,
in terms of accuracy and stead-state error. A nonlinear orbital simulator is considered in the
simulations, with limitations both of the actuation system (with saturation and delay) and of the
update frequencies. Model uncertainties, different initial conditions and external disturbances are
also included in the performed simulations
Obstacle Avoidance with Potential Field Applied to a Rendezvous Maneuver
Full text linkThis paper outlines a method based on the theory of artificial potential fields combined with sliding mode techniques for spacecraft maneuvers in the presence of obstacles. Guidance and control algorithms are validated with a six degree-of-freed (dof) omorbital simulator. The idea of this paper is to provide computationally efficient algorithms for real time applications, in which the combination of Artificial potential field (APF) and sliding mode control shows the ability of plan trajectories, even in the presence of external disturbances and model uncertainties. A reduced frequency of the proposed controllers and a pulse width modulation (PWM) of the thrusters are considered to verify the performance of the system. The computational performance of APF as a guidance algorithm is discussed and the algorithms are verified by simulations of a complete rendezvous maneuver. The proposed algorithm appears suitable for the autonomous, real-time control of complex maneuvers with a minimum on-board computational effort
Assessment of Quadrotor Near-Wall behaviour using six-Degrees of Freedom CFD simulations
Full text linkThe growth of Unmanned Aerial Systems (UASs) in various applications requires more autonomous and safe missions. The paper introduces an innovative approach that combines the Computational Fluid Dynamics (CFD) model and closed-loop control algorithm to simulate UAS maneuvers precisely. This study proposes a Proportional-Integrative-Derivative (PID) controller for both position and attitude dynamics due to its simple implementation and employment in a commercial autopilot system. Thanks to the numerical simulation of the UAS aerodynamics, it was possible to perform an accurate analysis, especially for critical conditions, such as wall effect or rapid wind gusts. In these particular situations, it is essential to exploit an advanced propulsive model to capture the interaction between vehicle dynamics, aerodynamics, and environmental conditions. The complete CFD/PID framework enables a virtual testing environment for UAS platforms. The paper compares an innovative in-the-loop CFD approach and a classical simplified propulsive model that adopts constant thrust and torque coefficients to verify the numerical model. Furthermore, we present numerical simulations of a quadcopter in the neighborhood of a wall studying the ability of the discussed control algorithm to maintain a hovering position at different distances from the wall
Assessment of Quadrotor PID Control Algorithms using six-Degrees of Freedom CFD simulations
Full text linkThe evolution of technology has made increasingly advantageous the introduction of Unmanned Aerial Systems (UASs) in various applications, especially by exploiting their ability for autonomous flight. This paper presents an innovative approach to simulating UAS maneuvers that integrates a Computational Fluid Dynamics (CFD) model and a closed-loop control algorithm for both position and attitude dynamics. We chose the Proportional-Integrative-Derivative (PID) controller for this preliminary research activity because of its simple implementation and widespread employment in commercial autopilot systems. The numerical simulation of the UAS aerodynamics allows for performing an accurate analysis in critical situations. These include, for example, ground effect or wind gusts scenarios, which require an enhanced propulsive model to capture the interaction between vehicle dynamics, aerodynamics, and environmental conditions. The coupled CFD/PID framework can be a virtual testing environment for UAS platforms. Here we report on its validation. The paper compares such an innovative in-the-loop CFD approach and a classical simplified propulsive model that adopts constant thrust and torque coefficients
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