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The future of the Army's air delivery mission includes the use of precision-guided autonomous airdrop methods to resupply troops in the field. High-glide systems, ram-air parafoil-based, allow for a safe standoff delivery as well as wind penetration. This paper addresses the development of a six-degree-of-freedom model of a low-aspect ratio control...
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... Yang regarded the parachute body and the parachute rope as a rigid body in plane motion, and the load has a swing degree of freedom around the tether point, and established a longitudinal 4-DOF dynamic model of the dynamic parafoil to solve the dynamic response of the thrust step of the system from level flight to climbing state [4]. Mortaloni identified the unknown quantity in the added mass of the parafoil system by the parameter identification method and established a more accurate 6-DOF model [5]. Xiong established the dynamic model of the 6-DOF parafoil system, in which the aerodynamic force was selected by combining experimental data and engineering subsection processing; on this basis, the influence of different design parameters on the motion characteristics of the parafoil system was analyzed [6]. ...
Due to the problems of flexible parafoil systems that are susceptible to complex disturbances, such as external wind fields and being difficult to control, it is necessary to study the path planning and tracking control methods of parafoil under complex conditions. In this paper, the particle model and dynamic model of the parafoil system are established, and the path planning method based on the original natural (ON) principle coupled with meteorological interference, terrain avoidance, and other environmental models is studied. Sliding mode control is introduced into the path tracking control of the parafoil system, and tracking errors of the parafoil position and velocity are taken as the design criteria for the sliding mode surface. The control law of the sliding mode controller is derived. Through simulation comparison with other path planning and tracking control methods, the methods designed in this paper can reflect better path planning and tracking performance. The methods designed in this paper can effectively suppress the impact of external disturbances, improve accuracy, and enhance robustness.
... Among many representation models for parafoil dynamics including 4-degrees of freedom(DOF) [26], or 6-DOF model [27], 9-DOF model [28][29][30] is widely used to approximate parafoil specific dynamic characteristics. Newton-euler equations that describe translational and rotational motion of a rigid body is applied to both P and B. Since translational motions of P and B are subject to C, those are expressed in terms of translational motion of C using corresponding kinematic equations. ...
View Video Presentation: https://doi.org/10.2514/6.2022-2442.vid This study proposes a data-driven autonomous landing hazard avoidance technique(ALHAT) of a parafoil that carries a payload of a large aerospace platform and lands on a nonhazardous region. Steering law of the parafoil is realized by applying soft actor-critic(SAC) deep reinforcement learning algorithm to carefully tailored Markov decision process which implicitly encompass parafoil states, ground hazard population and their evolution in time. Model-based approaches to parafoil guidance and control are subject to both fidelity of dynamic model and accuracy of model parameters all of which are hardly precisely known. Thus, the research aims at deriving near end-to-end steering logic of parafoil brakes to avoid hazard landing in a data-driven manner. Multiple grayscale images over several time steps stacked in channel direction are utilized as observation of Markov decision process(MDP) to imply temporal evolution of hazard while each image is a projection of hazard population onto parafoil viewpoint whose intensity is adjusted according to parafoil height. The reward function is shaped to let agent value avoiding hazards using the spatially weighted mask. Results of numerical simulation show that the parafoil ALHAT is achievable without any prior knowledge about parafoil dynamics, hazard transition, and human supervision.
... In the following years, the Small Autonomous Parafoil Landing Experiment (ALEX I and II), described in detail by Jann [8,9], set a milestone on modeling, validation, and verification of PADSs using 3-and 4-DOF, employing a ram-air parachute with a payload of 100 kg. Different models have been developed for a varying range of DOF, either considering the parafoil-payload system as a rigid body or allowing relative motion between their components [10][11][12][13]. Comparisons between models happen to be a complex task, since different considerations, payload masses, parafoil aerodynamic properties, and general assumptions are used by different authors. ...
In this research, we focus on the use of Unmanned Aerial Vehicles (UAVs) for the delivery of payloads and navigation towards safe-landing zones, specifically on the modeling of flight dynamics of lightweight vehicles denoted Precision Aerial Delivery Systems (PADSs). While a wide range of nonlinear models has been developed and tested on high-end applications considering various degrees of freedom (DOF), linear models suitable for low-cost applications have not been explored thoroughly. In this study, we propose and compare two linear models, a linearized version of a 6-DOF model specifically developed for micro-lightweight systems, and an alternative model based on a double integrator. Both linear models are implemented with a sensor fusion algorithm using a Kalman filter to estimate the position and attitude of PADSs, and their performance is compared to a nonlinear 6-DOF model. Simulation results demonstrate that both models, when incorporated into a Kalman filter estimation scheme, can determine the flight dynamics of PADSs during smooth flights. While it is validated that the double integrator model can adequately operate under the proposed estimation scheme for up to small acceleration changes, the linearized model proves to be capable of reproducing the nonlinear model characteristics even during moderately steep turns.
... The research on dynamic modeling of parafoil systems began with investigating three degree-of-freedom (DoF) models, of which the system was treated as a particle that usually used for path planning [4], [5]. Afterward, six DoF models, in which the parafoil and the payload were considered to be one rigid body have been developed [3], [6], [7]. Equally by accounting for relative motions between the parafoil and the payload, models with eight or nine DoF have been developed as well, see [8]- [10]. ...
... Meanwhile, a multi-turn potentiometer (3) is equipped on each motor shaft to measure the rotation angle. The parafoil control system is constituted by a power plant, two motor drivers (5 and 6) and a controller (7). The model simulation system is composed of a computer and application software based on Matlab. ...
Parafoil systems represent flexible wing vehicles. In case a vehicle is flying at low altitude, it is well known that the vehicle is more susceptible to winds. Also, due to the nonlinear, large inertial existing within the system, traditional control methods, such as traditional proportional-integral-derivative (PID), cannot guarantee the quality of path following. Therefore, we here apply Generalized Predictive Control (GPC) based method for parafoil systems to follow the designed path for a better control effect. To achieve this, we first propose a novel modeling method based on Computational Fluid Dynamics (CFD) to build a dynamic model of the parafoil system in windy environments. Afterward, a guidance law is designed according to a hybrid approach that combines the cross track error and the line of sight. And the path following controller is established by using GPC. Finally, we generate and interpret numerical results to demonstrate the feasibility of the horizontal path following method in windy environments by utilizing the semi-physical simulation platform. The achieved results show that the GPC controller achieves high precision path following. More precisely, it possesses a better anti-wind ability and tracking accuracy and, therefore, the method outperforms PID controller.
... Mathematical models obtained by theoretical analysis and numerical simulation might help to investigate their stability and flight performance, as well as design and validation of guidance, navigation, and control (GNC) algorithms. In recent decades, several high fidelity models of parafoil systems have been developed, which range from simple three degree of freedom (DoF) models [2,3] to seven-/eight-/nine-DoF models [4][5][6][7]. Compared with the widely known kinematic relationships, one needs to tackle uncertainty when determining the effects of wind on the flight performance of the parafoil system. ...
In this paper, we explore a novel modeling technique to investigate a parafoil flying in wind environments by using computational fluid dynamics. Further, we apply an eight degree of freedom dynamic model of the parafoil in wind environment based on utilizing revised aerodynamic equations. Given that the traditional control methods cannot always tackle trajectory tracking effects properly, we propose an accurate trajectory tracking control method based on active disturbance rejection controller. Semi-physical simulation and airdrop experiments are conducted to evaluate the model as well as the control method. Results demonstrate that the proposed model is effective. Also, ADRC outperforms the PID controller regarding the anti-disturbance ability and control accuracy.
... Tao [5] used a three DOF motion model of parafoil system for planning optimal homing trajectories. Mortaloni [6] addressed the development of a six DOF model of a low aspect ratio controllable parafoil based delivery system which is equally suitable for modeling and simulation and for the design of guidance, navigation and control algorithms. Barrows [7] mainly focused on calculations of the apparent mass of parafoil, and presented dynamic equations including nonlinear terms of a six DOF model. ...
Parafoil systems are a kind of flexible wing vehicle. In view that the vehicle flying at low altitude is more susceptible to wind fields, and considering that the parafoil canopy and the payload are regarded as rigid connection, a six degrees of freedom (DOF) dynamic model is established according to the Kirchhoff motion equation, which consists of three DOF for translational motion and three DOF for rotational motion. Moreover, the effects of wind fields on its flight performances are also discussed. The motion characteristics of parafoil systems under the horizontal constant wind field are studied by numerical simulation. Simulation results demonstrate that the established model can accurately characterize dynamic performances of parafoil systems in wind fields, which is high valuable in engineering applications.
... Parafoils are typically modeled as dynamical systems having six degrees of freedom (Mortaloni et al. (2003); Slegers and Costello (2004)). A number of researchers have also treated the parafoil and the payload as separate rigid bodies and have modeled them as dynamical systems having eight (Iacomini and Cerimele (1999a,b)) and nine degrees of freedom (Slegers and Costello (2003)) under suitable assumptions. ...
This paper addresses the trajectory optimization for precision landing of parafoil assisted high altitude recovery modules. The problem is approached from an optimal control perspective. A simplified kinematic model of the parafoil payload system is considered. The angular velocity of the parafoil in the horizontal plane serves as the control input to the system. A multi objective performance index is formulated so as to ensure that the system achieves flared landing as closely as possible to a target point or region from a specified initial state with minimum control effort. The resulting optimal control problem with control and terminal constraints is solved numerically using the direct multiple shooting method to get the optimal trajectories that minimizes the performance index function. Subsequently, the effect of terminal payload delivery objectives on the optimal trajectories is looked into. This study is performed with a broad objective for obtaining preliminary results for achieving autonomous precision landing for a real world implementation of a high altitude recovery system.
... ft. parafoil, with the payload capacity of 500 lbs is used for modeling purposes as described in Reference (28). One exception in this model is the value of the yaw damping coefficient C nr , the value of which is assumed to be half the value assumed in (28). ...
... parafoil, with the payload capacity of 500 lbs is used for modeling purposes as described in Reference (28). One exception in this model is the value of the yaw damping coefficient C nr , the value of which is assumed to be half the value assumed in (28). Also the coefficients in rolling and yawing moment which are functions of asymmetric brake deflection δ a have been doubled with the assumption that the system is more sensitive to control inputs in the towed condition as compared to that in ...
The objective of this research was to develop a high-fidelity dynamic
model of a parafoil-payload system with respect to its application for
the Ship Launched Aerial Delivery System (SLADS). SLADS is a concept in
which cargo can be transfered from ship to shore using a
parafoil-payload system. It is accomplished in two phases: An initial
towing phase when the glider follows the towing vessel in a passive lift
mode and an autonomous gliding phase when the system is guided to the
desired point. While many previous researchers have analyzed the
parafoil-payload system when it is released from another airborne
vehicle, limited work has been done in the area of towing up the system
from ground or sea. One of the main contributions of this research was
the development of a nonlinear dynamic model of a towed parafoil-payload
system. After performing an extensive literature review of the existing
methods of modeling a parafoil-payload system, a five degree-of-freedom
model was developed. The inertial and geometric properties of the system
were investigated to predict accurate results in the simulation
environment. Since extensive research has been done in determining the
aerodynamic characteristics of a paraglider, an existing aerodynamic
model was chosen to incorporate the effects of air flow around the
flexible paraglider wing. During the towing phase, it is essential that
the parafoil-payload system follow the line of the towing vessel path to
prevent an unstable flight condition called 'lockout'. A detailed study
of the causes of lockout, its mathematical representation and the flight
conditions and the parameters related to lockout, constitute another
contribution of this work. A linearized model of the parafoil-payload
system was developed and used to analyze the stability of the system
about equilibrium conditions. The relationship between the control
surface inputs and the stability was investigated. In addition to
stability of flight, one more important objective of SLADS is to tow up
the parafoil-payload system as fast as possible. The tension in the tow
cable is directly proportional to the rate of ascent of the
parafoil-payload system. Lockout instability is more favorable when tow
tensions are large. Thus there is a tradeoff between susceptibility to
lockout and rapid deployment. Control strategies were also developed for
optimal tow up and to maintain stability in the event of disturbances.
... All aerodynamic coefficients and apparent mass coefficients for the canopy are provided inTable 1. Aerodynamic coefficients were estimated from flights of a small experimental system in a similar manner to [3,10]. It is noted that the coefficients inTable 1 for the small parafoil are somewhat similar to those used and reported for bigger systems [19]. Inertia matrices for both the parafoil and payload are provided next, both having units of slug-ft 2 : ...
An eight-degree-of-freedom model is developed that accurately models relative pitching and yawing motion of a payload with respect to a parafoil. Constraint forces and moments are found analytically rather than using artificial constraint stabilization. A turn rate controller common in precision placement algorithms is used to demonstrate that relative yawing motion of the payload can result in persistent oscillations of the system. A model neglecting relative payload yawing failed to predict the same oscillations. It is shown that persistent oscillations can be eliminated by reduction of feedback gains; however, resulting tracking performance is poor. A reduced-order linear model is shown to be able to adequately predict relative payload dynamics for the proposed turn rate controller on the full eight-degree-of-freedom system.
... Mortaloni et al. reported the development of a 6-DoF Simulink model of the Pegasus-500 parafoil-payload system by FXC Corporation. 10 Both diagonal and non-diagonal terms of the apparent mass matrix were taken into account. Model was tuned to perfectly match results of a real drop of the system. ...
... The dependences of aerodynamic and control coefficients versus angle of attack were developed earlier based on the available data 13 tuned to match the flight test data. 10 Parafoil-payload coupling reactions were modeled in pretty much the same manner as say in Refs. 54,55,66. ...
The paper presents an initial move to develop a scalable high-degree-of-freedom model of the parafoil-payload system. The intention is to develop the tool capable of: (1) determining basic system's geometry parameters by observing the video data of the real descend, (2) readjusting the nominal aerodynamic and control coefficients incorporated into the well-established equations of motions, and (3) performing model identification to tune numerous relative variables to achieve the best fit with the real drop data if available. Since in the certain way such a tool would represent some kind of generalization of the modeling efforts undertaken so far, the present paper starts from a comprehensive review of publications devoted to the modeling of parafoil-payload systems. The paper then briefly addressed the current stage of the development of a scalable model. In anticipation of real drop data to validate the approach paper ends with conclusions.
