Backstepping Control Design for the Coordinated Motion of Vehicles in a Flowfield

Motion coordination of autonomous vehicles has applications from target surveillance to climate monitoring. Previous research has yielded stabilizing formation control laws for a self-propelled vehicle model with first-order rotational dynamics; however this model does not adequately describe the rotational and translational dynamics of vehicles in the atmosphere or ocean. This thesis describes the design of decentralized algorithms to control self-propelled vehicles with second-order rotational and translational dynamics. Backstepping controls for parallel and circular formations are designed in the absence of a flowfield and in a steady, uniform flowfield. Backstepping and proportional-integral controllers are then used to stabilize yaw in a rigid-body model. Feedback linearization is used to attain the desired forward speed. These formation control laws extend prior results to a more realistic vehicle model. Aside from the addition of new sensing and communication requirements, the second-order control laws are demonstrated to have comparable performance to the first-order controllers. The theoretical results are illustrated by numerical simulations

Similarity Decomposition Approach to Oscillatory Synchronization for Multiple Mechanical Systems With a Virtual Leader

This paper addresses the oscillatory synchronization problem for multiple uncertain mechanical systems with a virtual leader, and the interaction topology among them is assumed to contain a directed spanning tree. We propose an adaptive control scheme to achieve the goal of oscillatory synchronization. Using the similarity decomposition approach, we show that the position and velocity synchronization errors between each mechanical system (or follower) and the virtual leader converge to zero. The performance of the proposed adaptive scheme is shown by numerical simulation results.Comment: 15 pages, 3 figures, published in 2014 Chinese Control Conferenc

결합된 쿼드로터 무인비행로봇의 모델링 및 제어

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 이동준.본 논문에서는 두 대의 쿼드로터 무인비행로봇을 비스듬히 결합한 새로운 시스템을 제시한다. 본 시스템은 기존의 한 대의 쿼드로터가 가지는 부족구동(underactuation)적인 측면과 낮은 적재하중의 문제를 극복하는 장점을 가진다. 즉, 기존에 쿼드로터가 4개의 구동 자유도를 갖는데 반해 본 시스템은 5개의 구동 자유도를 가져 한 차원의 제어가 추가로 가능하며, 이는 두 쿼드로터가 결합된 축 방향으로의 피치 (pitch) 동작에 대한 자유도로 활용할 수 있다. 이러한 특성은 공중 도구조작 (aerial tool operation) 등과 같은 실제 임무를 수행할 때 매우 유용하게 적용 가능하다. 제시된 비스듬히 결합한 쿼드로터 무인비행로봇 시스템에 대해 동역학 및 추력 관계식을 모델링하고, 궤적 추적 (trajectory tracking) 을 위해 백스텝핑 제어기법을 활용한 제어를 설계하였다. 또한, 각 로터에서의 추력들이 항상 양의 값을 가져야하는 제약조건을 만족시키기 위한 최적화 기법 을 제시하였다. 다양한 시뮬레이션을 통해 본 시스템과 제어기를 검증하였고 그 결과를 제시하였다.In this thesis, we introduce a novel concept of asymmetrically coupled quadrotor UAVs (Unmanned Aerial Vehicles) system. The proposed system is composed with two quadrotor UAVs that are asymmetrically coupled with each other. This coupled system has advantages in the sense of overcoming under-actuation and payload problems compared to single conventional quadrotor UAV. That is, the proposed system has 5 actuation DOFs while single quadrotor UAV has 4 actuation DOFs, where the additional actuation can be exploited for decoupling translation and rotation in a certain direction. This feature increases the versatility and is useful for real tasks such as aerial tool operation. We first model the coupled quadrotor system and design a controller which is based on the backstepping control and optimization to guarantee positiveness of thrusts. Simulation results are presented to validate the theory and to demonstrate the advantages of the proposed system.1 Introduction 1 1.1 Motivation and Objectives 1 1.2 State of the Art 3 1.3 Contribution of this Work 4 2 System Modeling 6 2.1 Asymmetrically Coupled Quadrotor UAVs 6 2.2 Dynamics of Asymmetrically Coupled Quadrotor UAVs 9 2.3 Thrust Relationship 13 3 Control Design 16 3.1 Backstepping Control 17 3.2 Positive Thrust Constraint 23 4 Simulation 26 4.1 Simulation Scheme 26 4.2 Simulation Results 28 4.2.1 Trajectory tracking 29 4.2.2 Translation along x-axis without rotation 31 4.2.3 Rotation without translation 35 4.2.4 Combination case 37 4.2.5 Tool operation example 40 5 Conclusion and Future Work 44 5.1 Conclusion 44 5.2 Future Work 45Maste

Robust Team Formation Control for Quadrotors

In this brief, we develop a suboptimal H ∞ controller for a leader-follower formation problem of quadrotors with the consideration of external disturbances and model parameter uncertainties. We also compare the control performances between this H ∞ controller and an integral backstepping (IBS) controller for this problem. The resultant state feedback controller establishes the asymptotically stability of the closed-loop nonlinear system. Simulation results show a good performance for both controllers in normal circumstance, and the H ∞ controller performs much better than the IBS controller under the disturbances. Experimental results of using H ∞ controller show its stability and robustness against the disturbances

Improving Leader-Follower Formation Control Performance for Quadrotors

This thesis aims to improve the leader-follower team formation flight performance of Unmanned Aerial Vehicles (UAVs) by applying nonlinear robust and optimal techniques, in particular the nonlinear H_infinity and the iterative Linear Quadratic Regulator (iLQR), to stabilisation, path tracking and leader-follower team formation control problems. Existing solutions for stabilisation, path tracking and leader-follower team formation control have addressed a linear or nonlinear control technique for a linearised system with limited disturbance consideration, or for a nonlinear system with an obstacle-free environment. To cover part of this area of research, in this thesis, some nonlinear terms were included in the quadrotors' dynamic model, and external disturbance and model parameter uncertainties were considered. Five different controllers were developed. The first and the second controllers, the nonlinear suboptimal H_infinity control technique and the Integral Backstepping (IBS) controller, were based on Lyapunov theory. The H_infinity controller was developed with consideration of external disturbance and model parameter uncertainties. These two controllers were compared for path tracking and leader-follower team formation control. The third controller was the Proportional Derivative square (PD2), which was applied for attitude control and compared with the H_infinity controller. The fourth and the fifth controllers were the Linear Quadratic Regulator (LQR) control technique and the optimal iLQR, which was developed based on the LQR control technique. These were applied for attitude, path tracking and team formation control and there results were compared. Two features regarding the choice of the control technique were addressed: stability and robustness on the one hand, which were guaranteed using the H_infinity control technique as the disturbance is inherent in its mathematical model, and the improvement in the performance optimisation on the other, which was achieved using the iLQR technique as it is based on the optimal LQR control technique. Moreover, one loop control scheme was used to control each vehicle when these controllers were implemented and a distributed control scheme was proposed for the leader-follower team formation problem. Each of the above mentioned controllers was tested and verified in simulation for different predefined paths. Then only the nonlinear H_infinity controller was tested in both simulation and real vehicles experiments

Quadrotor team modeling and control for DLO transportation

94 p.Esta Tesis realiza una propuesta de un modelado dinámico para el transporte de sólidos lineales deformables (SLD) mediante un equipo de cuadricópteros. En este modelo intervienen tres factores: - Modelado dinámico del sólido lineal a transportar. - Modelo dinámico del cuadricóptero para que tenga en cuenta la dinámica pasiva y los efectos del SLD. - Estrategia de control para un transporte e ciente y robusto. Diferenciamos dos tareas principales: (a) lograr una con guración cuasiestacionaria de una distribución de carga equivalente a transportar entre todos los robots. (b) Ejecutar el transporte en un plano horizontal de todo el sistema. El transporte se realiza mediante una con guración de seguir al líder en columna, pero los cuadricópteros individualmente tienen que ser su cientemente robustos para afrontar todas las no-linealidades provocadas por la dinámica del SLD y perturbaciones externas, como el viento. Los controladores del cuadricóptero se han diseñado para asegurar la estabilidad del sistema y una rápida convergencia del sistema. Se han comparado y testeado estrategias de control en tiempo real y no-real para comprobar la bondad y capacidad de ajuste a las condiciones dinámicas cambiantes del sistema. También se ha estudiado la escalabilidad del sistema