Conference Paper

Sliding mode control for a quadrotor slung load system

Authors:
  • , Shenyang Institue of Automation, Chinese Academy of Sciences
  • Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang, China
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Abstract

This paper studies the modeling and control of a quadrotor with a suspended load. It is shown that the excessive load swing is the part of the system dynamics, which may degrade the quadrotor control performance. A detailed analysis about the system modeling with the load swing effect is carried out based on Newton-Euler and Euler-Lagrange method. A framework for sliding mode control of the quadrotor slung load system is then developed. The simulation results show the excellent modeling and control performance.

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... Diverse research works have explored original solutions for the Unmanned Aircraft System (UAS)-based payload transportation problem for constant and variable mass payloads. As a few examples, the authors in [1] developed an autonomous vehicle to transport a payload by using a tensor embedded in the vehicle, while the authors in [2] designed strategies for load transportation that involves a team of cooperative vehicles. Previously, the authors in [3] presented the MORUS project where they conducted the control design for a multirotor vehicle to transport an autonomous submarine vehicle to a desired zone. ...
... Considering the dynamic model of the multirotor UAS given in (1), and defining the configuration vector as = [ , , , , , ] ⊤ , with =̇ , the overall system can be expressed in the following nonlinear special form [23]: ...
... Consider the UAS altitude dynamics̈ given in (1), and represented in the special nonlinear form (2). Defining the state variables: ...
Article
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This paper deals with the development of an adaptive robust controller for an Unmanned Aircraft System with variable mass. The goal is to improve trajectory tracking and energy performance while the aircraft mass is gradually reducing due to payload release. To improve the trajectory tracking performance, we propose an algorithm that merges the concepts of least squares method and sliding mode observer for the estimation of the vehicle mass. The nonlinear observer estimates the linear velocities and accelerations, which are further used to obtain the vehicle mass. A robust adaptive pole placement controller based on the Attractive Ellipsoid Method uses this estimation to update the controllers gains due to the mass variation. To validate the effectiveness of the proposed algorithm for performing aerial transportation and deployment of payloads, we present a numerical example comparing the performance of the proposed method with respect to using Proportional Derivative controllers as well as Robust Controllers.
... According to [26] [27] [28], the thrust force generated by the i th rotor of the quadrotor is given by: ...
... The roll torque (τϕ) is responsible for the turning effect of the propellers during rotation when the quadrotor moving in the rotational phi (ϕ) direction as shown Fig. 3.3. That is directly proportional to the difference of thrust force generated by the 2 nd and 4 th motors (F4 -F2) [26]- [28]. ...
... Where ℒ is the distance from the center of each rotors to center of the gravity (the quadrotor object center) [26]- [28]. ...
Thesis
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In this thesis, trajectory tracking control of quadrotor Unmanned Aerial Vehicle (UAV) is done by controlling attitude and position of the quadrotor using Sliding Mode Controller (SMC) and fuzzy Proportional, Integrator and Derivative (PID) controller, simultaneously. Quadrotor UAV have been an increasingly popular research topic in recent years due to their low cost, maneuverability, simplicity of structure, ability to hover, vertical takeoff and landing (VTOL) capacity and ability to perform variety of tasks. Here two type of controllers were used to track reference trajectories with improved performance. SMC is used for position and altitude (translational dynamics), whereas fuzzy PID controller is used for attitude and heading (rotational dynamics). Dynamic modeling of the quadrotor was derived using Newton-Euler formalization including aerodynamic effects. The proposed SMC and fuzzy PID controller strategies were designed for the non-linear quadrotor dynamics. The controller robustness are tested by adding external random disturbance on the out state. The control performance of SMC alone and mixed sliding mode-fuzzy PID controller are compared. Finally, the behavior of the quadrotor under the proposed control system was validated by using MATLAB/Simulink. The simulation results showed that the performance of the proposed control scheme have better trajectory performance and good disturbance rejection ability. Keywords: Quadrotor, UAV, Dynamic modeling, SMC, Fuzzy PID control
... It is directly proportional to the difference of the thrust force generated by the second and fourth propellers 42 (F -F ) [7][8][9]. ...
... It is directly proportional to the difference of the thrust force generated by the first and third propellers 31 (F -F ) [7][8][9]. ...
... Yaw torque which is directly proportional to the difference of thrust force generated by all propellers [7][8][9]. ...
Article
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1 Abstract-This paper studies the modeling and control of quadcopter. It models the quadcopter nonlinear dynamics using Lagrange formalism and design controller for attitude (pitch & roll), heading & altitude tracking of the quadrotor. Mathematical modeling includes aerodynamic effects and gyroscopic moments. One Non-linear Control strategy, Third-Order Sliding Mode Control (TOSMC), based on a supertwisting algorithm has been proposed. The Controller has been implemented on the quadrotor physical model using Matlab/Simulink software. Finally, the performance of the proposed controller was demonstrated in the simulation study. The simulation results show excellent modeling and control performance.
... It is responsible for turning effect of quadrotor body along z-axis. Which is directly proportional to the difference of thrust force generated by all of the propellers [10][11][12]. ...
... The gyroscopic moment that effects on the physical system due to both the four propellers and quadrotor body. The gyroscopic effect of rotors is smaller than the one caused by the quadrotor body [12]. ...
... torque It is responsible for turning effect of quadrotor body along x-axis. It is directly proportional to the difference of thrust force generated by the second and fourth propellers42 () FF −[10][11][12]. ...
Article
Full-text available
Quadrotor have been an increasingly popular research topic in recent year due to their low cost, maneuverability, simplicity of structure, ability to hover, their vertical takeoff and landing (VTOL) capacity and ability to perform variety of tasks. Besides, it is a great platform for control systems research, which is highly nonlinear and under-actuated system. The main target of this paper is to model the quadrotor nonlinear dynamics using Lagrange formalism and design controller for attitude (pitch & roll), heading & altitude regulation of quadrotor. The mathematical modelling includes aerodynamic effects and gyroscopic moments. One Non-linear Control strategies, Higher-Order Sliding Mode Control (HOSMC) based on super-twisting algorithm has been proposed. Higher-Order Sliding Mode Controller is designed for regulation or stabilization on the four controlled variables. The Controller has been implemented on the quadrotor physical model using Matlab/Simulink software. Finally, the performance of the proposed controller demonstrated in simulation study.
... It is responsible for turning effect of quadrotor body along z-axis. Which is directly proportional to the difference of thrust force generated by all of the propellers [10][11][12]. ...
... The gyroscopic moment that effects on the physical system due to both the four propellers and quadrotor body. The gyroscopic effect of rotors is smaller than the one caused by the quadrotor body [12]. ...
... torque It is responsible for turning effect of quadrotor body along x-axis. It is directly proportional to the difference of thrust force generated by the second and fourth propellers42 () FF −[10][11][12]. ...
Article
Quadrotor have been an increasingly popular research topic in recent year due to their low cost, maneuverability, simplicity of structure, ability to hover, their vertical takeoff and landing (VTOL) capacity and ability to perform variety of tasks. Besides, it is a great platform for control systems research, which is highly nonlinear and under-actuated system. The main target of this paper is to model the quadrotor nonlinear dynamics using Lagrange formalism and design controller for attitude (pitch & roll), heading & altitude regulation of quadrotor. The mathematical modelling includes aerodynamic effects and gyroscopic moments. One Non-linear Control strategies, Higher-Order Sliding Mode Control (HOSMC) based on super-twisting algorithm has been proposed. Higher-Order Sliding Mode Controller is designed for regulation or stabilization on the four controlled variables. The Controller has been implemented on the quadrotor physical model using Matlab/Simulink software. Finally, the performance of the proposed controller demonstrated in simulation study.
... There are two coordinate systems, the local north, east, down (NED) frame {E} = x e , y e , z e for translation and the body frame {B} = x b , y b , z b for rotation. The quadrotor structure and the two coordinate systems are shown in Figure 1, where x, y, z represent the translational displacement in each direction, φ, θ, ψ (the Euler angles corresponding to roll, pitch and yaw), respectively [34,35]. ...
... There are two coordinate systems, the local north x y z = for rotation. The quadrotor structure and the two coordinate systems are shown in Figure 1, where , , x y z represent the translational displacement in each direction, , , φ θ ψ (the Euler angles corresponding to roll, pitch and yaw), respectively [34,35]. According to Newton's second law and the Euler moment of momentum equation, referring to [5,22,36,37], the complete dynamic model of a quadrotor is represented as follows According to Newton's second law and the Euler moment of momentum equation, referring to [5,22,36,37], the complete dynamic model of a quadrotor is represented as follows ...
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A model-independent control strategy called high-order differential feedback control (HODFC) is applied to a quadrotor unmanned aerial vehicle (QUAV) based on a semi-autopilot indoor optical positioning system. The affine system form of the quadrotor model is provided to facilitate the design of the HODFC. A fifth-order high order differentiator (HOD) is introduced to estimate with high precision the derivatives of the reference input and the QUAV system’s states. A filtering signal of the control output is incorporated in the control law to overcome the system model’s unknown part in the HODFC scheme. The stability of both the HODFC and the HOD are proved. The physical and straightforward parameters are provided to make the HODFC scheme for the QUAV easy to operate. The real-time trajectory tracking experiments with varied reference trajectories and disturbances are carried out to illustrate the superior performance of the HODFC versus the proportional-integral-derivative (PID) method, in terms of the mean of absolute error, the integral of absolute error and the integral of the time-weighted absolute error. The results also demonstrate that the HODFC has superiority in static and dynamic trajectory tracking, especially when the system is disturbed.
... A quadrotor carrying a cable-suspended load is usually called a quadrotor slung load (QSL) system. There are distinct advantages for using a QSL system to transport cargos [1][2][3]. A QSL system can freely pass complex terrains and access the locations which are hard for the ground vehicle transportation. ...
... However, in spite of the benefits the QSL system could provide, the swing load will seriously influence the dynamics of the QSL system [4] and increase its degrees of freedom [5]. The dynamics of a QSL system are strongly nonlinear, coupled, and underactuated, remaining many challenging problems in the controller design [1][2][3][4][5]. Generally, there are two ways to improve the performance of a QSL system, namely: (1) trying to construct a more accurate model that meets the QSL dynamics so that the controller can use it to compensate the complex dynamics; and (2) designing a controller that could reject the unmodeled uncertainties effectively, while achieving good control performance at the same time. ...
Article
Full-text available
In this paper, a simple active-model-based control scheme is developed for the quadrotor slung load (QSL) system. The scheme works to improve the rejection of the influences caused by the abruptly changed load as a complementary enhancement while maintaining the structure and parameters of the original controller. A linearized model is first constructed with respect to the hovering state of a quadrotor. Modeling error is then introduced to describe the uncertainties caused by the load change and the simplified model. The modeling error is actively estimated by a Kalman filter (KF), while the estimation is further integrated into a normal controller, to enhance its performance of disturbance rejection. Experiments are conducted on a quadrotor controlled by the Pixhawk, which is one of the most popular controllers commercially available on the market. The improvements of the proposed scheme are shown by the comparisons between the controls with and without the active-model-based enhancement. The experiments also indicate that, with its simple structure and less computational algorithm, this active-model-based enhancement would be a feasible approach to enhance the commercial UAV controller to handle more uncertainties.
... Palunko et al. focus on generating a trajectory for the UAV that will minimize the payload swing during transportation along the path [30]. Kui et al. propose a sliding mode controller to track a given trajectory with the quadrotor using no explicit payload feedback, which worked well in simulation [31]. The quadcopter is assumed to be symmetrical, there is no damping force on the system, and certain constants are specified in this technique, which limits the generality of the problem solution. ...
... However, they are open-loop control methods and highly sensitive to external interferences. The most representative method based on the regulation control strategy is nonlinear control, which includes the energy-based method [20], back-step method [21], hierarchical control [22], sliding mode control [23,24], and adaptive control [25]. These nonlinear control methods can make a system's state asymptotically or exponentially track the reference instruction and also achieve accurate positioning. ...
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This study investigates the trajectory planning problem for double-pendulum quadrotor transportation systems. The goal is to restrain the hook swing and payload swing while achieving precise positioning. An online trajectory planning method with two capabilities—precise positioning and swing suppression—is proposed. The stability and convergence of the system are proved using the Lyapunov principle and the LaSalle’s invariance theory. Simulation results show that the proposed method has excellent control performance.
... A nonlinear back-stepping controller that allows the UAV to follow the trajectory independently of the pendulum movement was proposed. In [21], the dynamic equations of the suspended load transporting quadrotor and the dynamics of the load oscillation with the quadrotor are discussed in detail. In our previous work [22], SMC has been developed for the control of the quadrotor system carrying suspended payload. ...
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In this paper, a neuro-sliding mode controller (SMC) has been designed for a quadrotor transporting a suspended payload. SMCs are very efficient under uncertain conditions. However, if the uncertain dynamics change over time, SMC gains need to be updated to maintain the tracking performance. This study proposes a neuro-SMC to control a quadrotor UAV carrying a suspended payload in the existence of time-varying uncertain dynamics. Once the accuracy of the proposed controller is demonstrated theoretically using the Lyapunov stability criterion, the effectiveness of the proposed controller is shown in simulation, which confirms the theoretical claims.
... erefore, it is poor and even not acceptable for the tracking accuracy and the robustness of the quadrotor. To overcome the drawbacks of the aforementioned linear control approaches, a large number of nonlinear control strategies, including backstepping control [12][13][14][15], sliding mode control (SMC) [16][17][18][19][20], and feedback linearization control, are utilized to improve the tracking performance of the flight control system. ...
Article
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A robust adaptive fuzzy nonlinear controller based on dynamic surface and integral sliding mode control strategy (ADSISMC) is proposed to realize trajectory tracking for a class of quadrotor UAVs. In this study, the composite factors including parametric uncertainties and external disturbances are added to controller design, which make it more realistic. The quadrotor model is divided into two subsystems of attitude and position that make the control design become feasible. The main contributions of the proposed ADSISMC strategy are as follows: (1) The combination of dynamic surface and integral sliding mode makes the system always in sliding stage by finding the appropriate initial position compared with the common sliding mode, and the complexity of explosion in backstepping method is eliminated. (2) By introducing the fuzzy system, the unknown functions and uncertainties can be approximated which significantly improves the robustness and the tracking performance. (3) The switching control strategy is utilized to compensate for the errors between estimated and ideal inputs; the tracking performance of the whole system has been significantly improved. The simulation results show the effectiveness of the proposed control method.
... In reference [9], the authors present a solution to the trajectory tracking problem for a quadrotor with a slung load using an exact linearization controller without stability test. Another nonlinear control technique used to solve this problem is the sliding mode, as reported in [10]. The work in [11] proposes a control strategy based on the backstepping method. ...
... In [17], sliding control is applied for the quadrotor+slung-load problem assuring error convergence for the attitude and position of the load. The work in [18] applied input-shaping techniques to a single quadrotor+load system to minimize the load swing of the cable, after restricting motion to a 2D plane and linearizing the model, applying a PI and a PD-controller for the position and attitude dynamics of the load, respectively. ...
Thesis
This work proposes a cooperative control solution to the problem of transporting a suspended load using multiple quadrotor vehicles. The problem is addressed for two quadrotors, with a methodology that can be generalized for any number of quadrotors. A dynamic model of the system is developed, considering a point-mass load, rigid massless cables, and neglecting aerodynamic effects of the cables. The concept of differential flatness is explored and a new set of flat outputs, which can be used to fully characterize the state of the system, is proposed. A nonlinear Lyapunov-based controller in cascaded form is derived, by defining adequate mappings between the cable tension vectors and the quadrotor thrust vectors and exploring the analogy with the problem of controlling a single quadrotor. Simulation results are presented for tracking of load trajectories. Comparisons are made with a free-flying quadrotor control scheme to highlight the enhanced performance of the proposed scheme. Future work is then suggested to increase the accuracy of the full model, generalizing the control scheme and referring to a few estimation problems.
... Furthermore, application of the flexible connection method is restrained by the dimensions of flight space. So far, most researches focused on the former case [9] [10] [11] [12] while only a few researches on the latter one. Wang et al. [13] developed an integral sliding mode based adaptive robust control algorithm to control a quad-rotor helicopter transporting payload with unknown mass. ...
... Ivler [85] and Lee [86] describe a cable angle feedback control system for slung-load operations. Quadrotor control by input shaping [87,88] and sliding mode control [89] ...
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This paper studies the modeling and control of quadcopter. It models the quadcopter nonlinear dynamics using Lagrange formalism and design controller for attitude (pitch & roll), heading & altitude regulation of quadrotor. Mathematical modeling includes aerodynamic effects and gyroscopic moments. One Non-linear Control strategy, Third-Order SMC based on a super-twisting algorithm has been proposed. Third-Order SMC Controller is designed for regulation control problem with the four control variables. The Controller has been implemented on the quadrotor physical model using Matlab/Simulink software. Finally, the performance of the proposed controller was demonstrated in the simulation study. The simulation results show excellent modeling and control performance. Index Terms-HOSMC, Lagrange, Mathematical Modelling, Quadrotor, MATLAB/Simulink. 1. INTRODUCTION An Unmanned Aerial Vehicle (UAV) refers to a flying machine without an on-board human pilot [1], [2]. These vehicles are being increasingly used in many civil domains, especially for surveillance, environmental researches, security, rescue, and traffic monitoring. Under the category of rotorcraft UAVs, Quadrotor has acquired much attention among researchers. The quadrotor is a multi-copter that is lifted and propelled by four rotors, each mounted on one end of a cross-like structure. Each rotor consists of a propeller fitted to a separately powered Brushless DC motor. The quadcopter has six degrees of freedom (three translational and three rotational) and only four actuators [3]. Hence, the quadcopter is an underactuated, highly nonlinear, and coupled system. Several linear control approaches, such as PID, Linear Quadratic Regulator (LQR), and Linear Quadratic Gaussian(LQG), have been proposed in the literature and applied for attitude stabilization and/or altitude tracking of Quadrotors[13], [14]. However, these methods can impose limitations on the application of quadrotors for extended flight Regions, i.e., aggressive maneuvers, where the system is no longer linear. Moreover, the stability of the closed-loop system can only be achieved for small regions around the equilibrium point, which are extremely hard to compute. Besides, the performances of these control laws on attitude stabilization are not satisfactory enough compared with other more advanced methods. To overcome this problem, nonlinear control alternatives, such as feedback linearization, SMC [15], [16], [17], and Backstepping [18] approaches are recently used in the VTOL aircraft control framework. An integral predictive nonlinear H∞ strategy has been also proposed and applied by G.V. Raffo et al. in [19]. In summary, the literature on quadrotor control ignores the aerodynamic effects, air disturbance, and gyroscopic moments in the dynamic modeling of the quadrotor. Besides, in the case of sliding mode controller implementation, it does not reduce both the control effort and the chattering effect. This paper uses a novel approach to address the above problems. It also designed a novel Third-order SMC controller with minimum tracking error. The paper is organized into five sections. In section 1, it introduces quadrotor UAV. In Section 2, it models the physical system by considering the aerodynamic and gyroscopic effects. In Section 3, it designs second-order SMC based on the supertwisting algorithm. In Section 4, present the simulation results obtained from the control implementation of the physical system in the Simulink environment. Finally, in Section 5, it shows the control inputs and then concludes the work. 2. MATHEMATICAL MODELLING In this section, a complete dynamical model of the Quadrotor UAV is established using the Lagrange formalism. 2.1 Rotational Matrix The orientation of the quadrotor is represented by Euler angles (pitch, roll, and yaw).To transform the body-fixed frame into the inertial frame; the z-y-x rotational matrix is considered [4].
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This paper presents a feedforward swing reducing control system for augmenting already existing helicopter controllers and enables slung load flight with autonomous helicopters for general cargo transport. The feedforward controller is designed to avoid excitation of the lightly damped modes of the system by shaping the reference trajectory using robust input shaping. It is developed together with a slung load state estimator capable of estimating the slung load swing frequency. This means that the control system can adapt to an unknown wire length for the slung load. Simulations and flight tests show the effectiveness of the input shaping applied to a small scale autonomous helicopter slung load system. Both simulations and flight verifications shows significant slung load swing reduction using the proposed trajectory shaping over flight without. Indeed it is shown how the system is capable of performing almost completely swing free maneuvers using the designed input shaper. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.
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The ability of a helicopter to carry externally slung loads makes the aircraft very versatile for many civil and military operations. However, the piloted handling qualities of the helicopter are degraded by the presence of the slung load. A control system is developed that uses measurements of the slung load motions as well as conventional fuselage feedback to improve the handling qualities for hover/low speed operations. Past research has been limited to studies focused on load damping, as opposed to the piloted handling qualities focus of this paper. The approach implements an explicit model following control system with cable angle feedback for the externally loaded UH-60 Black Hawk helicopter, which is optimized via multi-objective optimization software to simultaneously meet stability, performance, and handling qualities requirements. The improvements provided by this control system are demonstrated in a piloted fixed base UH-60 simulation. Pilot comments and statistics are presented to show the effectiveness of the cable angle feedback control system as compared to a baseline control system.
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This paper presents the design and verification of a state estimator for a helicopter based slung load system. The estimator is designed to augment the IMU driven estimator found in many helicopter UAV's and uses vision based updates only. The process model used for the estimator is a simple 4 state acceleration driven pendulum. Sensor input for the filter is provided by a vision based system that measures the position of the slung load. The estimator needs no prior knowledge of the system as it estimates the length of the suspension system together with the system states. Finally the estimator is verified using flight data and it is shown that it is capable of reliably estimating the slung load states.
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This paper presents the design of a state estimator system for a generic helicopter based slung load system. The estimator is designed to deliver full rigid body state information for both helicopter and load and is based on the unscented Kalman filter. Two dierent approaches are investigated: One based on a parameter free kinematic model and one based on a full aerodynamic helicopter and slung load model. The kinematic model approach uses acceleration and rate information from two Inertial Measurement Units, one on the helicopter and one on the load, to drive a simple kinematic model. A simple and eective virtual sensor method is developed to maintain the constraints imposed by the wires in the system. The full model based approach uses a complex aerodynamical model to describe the helicopter together with a generic rigid body model. This rigid body model is based on a redundant coordinate formulation and can be used to model all body to body slung load suspension systems. Both estimators include bias estimation for the accelerometers and gyros and the model based estimator furthermore includes estimation of external wind disturbances. A vision system is used to measure the motion of the load relative to the helicopter. A method is devised to reduce the execution time of the process model in the unscented Kalman filter. The two approaches are tested through simulation and compared. The full model based approach shows better results than the kinematic model aproach, but at the cost of a larger computational burden.
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This paper presents the result of modelling and verification of a generic slung load system using a small-scale helicopter. The model is intended for use in simulation, pilot training, estimation, and control. The model is derived using a redundant coordinate formulation based on Gauss' Principle of Least Constraint using the Udwadia-Kalaba equation and can be used to model all body to body slung load suspension types. The model gives an intuitive and easy-to-use way of modelling and simulating dierent slung load suspension types and it includes detection and response of wire slacking and tightening, and aerodynamical coupling between the helicopter and the load. Furthermore, it is shown how the model can be easily used for multi-lift systems either with multiple helicopers or multiple loads. A numerical stabilisation algorithm as well as a trim algorithm is presented for the complete helicopter/load system and finally the use of the model is illustrated through simulations.
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of a swing reducing controller for heli- copter slung load systems using intentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous helicopters. The delayed feedback controller is added to ac- tively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integration with a feedforward control scheme based on input shaping for concurrent avoidance and dampening of swing. The de- sign of the delayed feedback controller is presented as an optimization problem which gives the possibility of an automated design process. Simulations and ight test verications of the control system on two dierent autonomous helicopters are presented and it is shown how a signicant improvement of oscillation damping can be achieved.
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This paper presents design and verification of an estimation and control system for a helicopter slung load system. The estimator provides position and velocity estimates of the slung load and is designed to augment existing navigation in autonomous helicopters. Sensor input is provided by a vision system on the helicopter that measures the position of the slung load. The controller is a combined feedforward and feedback scheme for simultaneous avoidance of swing excitation and active swing damping. Simulations and laboratory flight tests show the effectiveness of the combined control system, yielding significant load swing reduction compared to the baseline controller.
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This book offers a comprehensive introduction to intelligent control system design, using MATLAB simulation to verify typical intelligent controller designs. It also uses real-world case studies that present the results of intelligent controller implementations to illustrate the successful application of the theory. Addressing the need for systematic design approaches to intelligent control system design using neural network and fuzzy-based techniques, the book introduces the concrete design method and MATLAB simulation of intelligent control strategies; offers a catalog of implementable intelligent control design methods for engineering applications; provides advanced intelligent controller design methods and their stability analysis methods; and presents a sample simulation and Matlab program for each intelligent control algorithm. The main topics addressed are expert control, fuzzy logic control, adaptive fuzzy control, neural network control, adaptive neural contro l and intelligent optimization algorithms, providing several engineering application examples for each method.
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In view that the quadrotor helicopter flying at low altitude is more susceptible to the turbulent wind field, a dynamic model is established via Newton-Euler formalism to overcome this problem. The turbulent wind field is generated according to Dryden model. The controller includes integral backstepping controller for inner loop and PID controller for outer loop. The stability of the system is validated by Lyapunov theory. The dynamic performance and control ability under the effect of turbulent wind field is studied by numerical simulation. The results demonstrate that the model can accurately reflects dynamic performance of the system, and the controller presents good robustness in the effect of turbulent wind field.
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When a heavy load is suspended from a helicopter, excessive load swing degrades helicopter control and can result in obstacle collisions. This work examines the benefits of combining input-shaping and model-following control to improve performance when carrying a suspended load. Model-following control architectures are used in modern helicopter flight control systems to make the helicopter respond like a prescribed model. On its own, model-following control is ineffective when carrying a suspended load because excessive load swing degrades tracking of the prescribed model dynamics and thus control of the helicopter. Therefore, reducing load swing improves tracking of the prescribed model and increases safety and productivity. Input shaping is a control technique that has been used to control vibration of flexible machines, such as robots, satellites, and cranes. By combining input shaping with model-following control, helicopter payload swing is reduced and tracking of the prescribed model is improved. The design of an attitude-command flight control system that combines input-shaping and model-following control is illustrated using dynamic models of a Sikorsky S-61 helicopter. Simulation results are shown for lateral and longitudinal repositioning movements. These results show that applying input shaping to simulated pilot commands greatly improves helicopter performance when carrying a suspended load.
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This paper addresses the problem of using unmanned aerial vehicles for the transportation of suspended loads. The proposed solution introduces a novel control law capable of steering the aerial robot to a desired reference while simultaneously limiting the sway of the payload. The stability of the equilibrium is proven rigorously through the application of the nested saturation formalism. Numerical simulations demonstrating the effectiveness of the controller are provided.
Conference Paper
This paper presents the design and verification of a state estimator for a helicopter based slung load system. The estimator is designed to augment the IMU driven estimator found in many helicopter UAV's and uses vision based updates only. The process model used for the estimator is a simple 4 state acceleration driven pendulum. Sensor input for the filter is provided by a vision based system that measures the position of the slung load. The estimator needs no prior knowledge of the system as it estimates the length of the suspension system together with the system states. Finally the estimator is verified using flight data and it is shown that it is capable of reliably estimating the slung load states.
Conference Paper
Helicopters are often used to transport supplies and equipment to hard-to-reach areas. When a load is carried via suspension cables below a helicopter, the load oscillates in response to helicopter motion and external disturbances, such as wind. This oscillation is dangerous and adversely affects control of the helicopter, especially when carrying heavy loads. To provide better control over the helicopter, one approach is to suppress the load swing dynamics using a command-filtering method called input shaping. This approach does not require real-time measurement or estimation of the load states. A simple model of a helicopter carrying a suspended load is developed and experimentally verified on a micro coaxial radio-controlled helicopter. In addition, the effectiveness of input shaping at eliminating suspended load oscillation is demonstrated on the helicopter. The proposed model may assist with the design of input-shaping controllers for a wide array of helicopters carrying suspended loads.
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The application of rotorcraft to autonomous load carrying and transport is a new frontier for Unmanned Aerial Vehicles (UAVs). This task requires that hovering vehicles remain stable and balanced in flight as payload mass is added to the vehicle. If payload is not loaded centered or the vehicle properly trimmed for offset loads, the robot will experience bias forces that must be rejected. In this paper, we explore the effect of dynamic load disturbances introduced by instantaneously increased payload mass and how those affect helicopters and quadrotors under Proportional-Integral-Derivative flight control. We determine stability bounds within which the changing mass-inertia parameters of the system due to the acquired object will not destabilize these aircraft with this standard flight controller. Additionally, we demonstrate experimentally the stability behavior of a helicopter undergoing a range of instantaneous step payload changes.
Conference Paper
Helicopter sling-load operations are extremely useful, but they can also be dangerous. Excessive swinging of the load can degrade control, cause the payload to collide with obstacles, or allow the suspension cable to get tangled with objects. Suppressing load swing could increase safety and productivity. Input shaping is a control technique that has been used to suppress vibration of flexible machines, such as robots, satellites, and cranes. To investigate the use of input shaping on helicopters, a dynamic model is formed to characterize the translational response of a model helicopter and sling load to lateral control inputs. This translational model is used to simulate point-to-point movements with and without input shaping for a range of move distances. The input-shaped movements show greatly-reduced residual swing, with only a minor increase in move time. Data from an experimental trial using a model helicopter is presented.
Modeling and control of helicopters carrying suspended loads
  • C Adams
Design and flight test of a cable angle feedback control system for improving helicopter slung load operations at low speed
  • C M Ivler
Modeling, estimation, and control of helicopter slung load system
  • M Bisgaard