Potential problems and switching control for visual servoing

This paper proposes a potential switching scheme that enlarges the stable region of feature-based visual servoing. Relay images that interpolate initial and reference image features are generated by using affine transformation. Artificial potentials defined by the relay images are patched around the reference point of the original potential to enlarge the stable region. Simulations with simplified configuration and experiments on a 6 DOF robot show the validity of the proposed control scheme</p

Joint-coupled compensation effects in visually servoed tracking

Humans have degrees-of-freedom (DOF) of varying bandwidths and one casually observes that we coordinate these DOF while visually tracking. This suggests that joint interplay aids tracking performance. In a control scheme we call partitioning, both image and kinematic data are used to visually-servo a 5-DOF robot by defining a joint-coupling among the rotational and translational DOF. Analysis of simulations and experiments reveal that a robot's fast bandwidth joints physically serve as lead compensators when coupled to slower joints thus reducing tracking lag

Control Servo-Visual de un Robot Manipulador Planar Basado en Pasividad

En este trabajo se diseña un controlador servo visual basado en la propiedad de pasividad del sistema visual. Se propone un regulador con ganancias de control variables, de tal manera que se evita la saturacion de los actuadores y al mismo tiempo presenta la capacidad de corregir errores de pequena magnitud. Asimismo el diseno se hace teniendo en cuenta el desempeno L2, a fin de darle capacidad de seguimiento de objetos en movimiento, con un error de control pequeno. Se muestran resultados experimentales realizados en un robot manipulador industrial tipo planar para verificar el cumplimiento de los objetivos del controlador propuesto

High-Performance Control of an On-Board Missile Seeker Using Vision Information

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 하인중.본 논문에서는 미사일 탐색기에 영상센서를 도입하여 고성능, 고효율의 제어 성능을 보장할 수 있는 탐색기 제어기를 설계한다. 특히 표적의 깊이 정보 없이도 조준선 오차를 빠르게 0으로 수렴시켜 표적을 추적할 수 있음을 보였다. 제안하고 있는 새로운 탐색기 제어기는 표적 운동에 대한 선형 시불변 추정기를 도입하였다. 먼저 영상센서로부터 획득한 정보를 이용하여 이동 표적에 대한 호모그래피 행렬을 유도하였다. 또한 호모그래피 행렬을 분해하여 표적과 탐색기의 운동에 대한 정보를 획득한다. 획득한 운동 정보를 바탕으로 병진 운동 표적의 동역학 방정식과 측정 방정식을 선형 시불변 시스템으로 나타낸다. 이러한 병진 운동 표적 동역학 방정식에 기반하여 표적의 크기에 대한 불확실성을 고려한 루엔버거 관측기 형태의 표적 병진 운동 정보 추정기를 사용한다. 도입한 표적 병진 운동 정보 추정기는 기존의 기법들과 달리 영상 센서의 움직임과 관계없이 항상 수렴성을 보장할 수 있다. 이는 미사일 탐색기 제어기에 활용하기 매우 적합한 형태이다. 또한 영상 센서를 활용한 탐색기의 동역학 방정식을 유도하였다. 탐색기의 동역학 방정식과 표적 병진 운동 추정기에서 획득한 표적의 운동 정보를 이용하여 시선 변화율 추정기를 설계하였다. 더 나아가 설계한 추정기를 바탕으로 시선 변화율을 보상한 탐색기 제어 명령을 생성하도록 한다. 마지막으로 본 논문에서 제안한 탐색기 제어기가 표적을 추적할 수 있음을 증명하기 위해 수학적으로 엄밀한 분석을 제공한다. 또한 모의 실험을 실행하여 기존의 탐색기 제어기와 성능을 비교하고 제안한 기법의 실용성을 입증하도록 한다.This dissertation proposes a high-performance controller of an on-board missile seeker using vision information. The seeker controller can approach to a moving target without knowing the information of the target depth. Our approach consists of two parts: 1) an innovative time invariant linear estimator of the target motion, 2) a nonlinear seeker controller. First, by using the parameters of the homography matrix for a moving target, we derive the dynamic equation of a moving target as a time invariant system. This equation was derived under the assumption that the velocities of both seeker and the target are varying slowly. Based on the derived dynamic equation of the target motion, an innovative time invariant linear estimator is constructed, which could provide the information of target velocity. Different from the previous works, the proposed estimator does not require any motion of the seeker, such as snaking or accelerating of the seeker, for estimation convergence. Besides, it can guarantee the convergence even without knowing the information of the target depth. Next, a nonlinear seeker controller to bring the boresight error down to zero is proposed. We present some rigorous mathematical convergence analysis to demonstrate that the proposed seeker controller can track the moving target even when the information of the target depth is not given. Furthermore, we present the simulation result of conventional seeker controller to clarify the practicability of the proposed seeker controller. Thus, the proposed approach should be used and applied widely in industries and military applications.1. 서 론 1 1.1 연구 배경 1 1.2 연구 목표 5 2. 기존 탐색기 제어기법 7 2.1 표적의 운동을 고려한 호모그래피 행렬 8 2.2 이동 표적을 고려한 탐색기 제어 기법 12 2.2.1 미사일 탐색기의 동역학 방정식 12 2.2.2 표적 6자유도 운동 정보 추정 기법 19 2.3 표적 병진 운동 추정 기법 23 3. 새로운 탐색기 제어기 설계 40 3.1 새로운 제어기 설계 및 분석 40 3.2 모의 실험 결과 51 4. 결론 및 향후 연구 과제 57 참고문헌 59 Abstract 67Maste

Model free visual servoing in macro and micro domain robotic applications

This thesis explores model free visual servoing algorithms by experimentally evaluating their performances for various tasks performed both in macro and micro domains. Model free or so called uncalibrated visual servoing does not need the system (vision system + robotic system) calibration and the model of the observed scene, since it provides an online estimation of the composite (image + robot) Jacobian. It is robust to parameter changes and disturbances. A model free visual servoing scheme is tested on a 7 DOF Mitsubishi PA10 robotic arm and on a microassembly workstation which is developed in our lab. In macro domain, a new approach for planar shape alignment is presented. The alignment task is performed based on bitangent points which are acquired using convex-hull of a curve. Both calibrated and uncalibrated visual servoing schemes are employed and compared. Furthermore, model free visual servoing is used for various trajectory following tasks such as square, circle, sine etc. and these reference trajectories are generated by a linear interpolator which produces midway targets along them. Model free visual servoing can provide more exibility in microsystems, since the calibration of the optical system is a tedious and error prone process, and recalibration is required at each focusing level of the optical system. Therefore, micropositioning and three di erent trajectory following tasks are also performed in micro world. Experimental results validate the utility of model free visual servoing algorithms in both domains

Design and implementation of a vision system for microassembly workstation

Rapid development of micro/nano technologies and the evolvement of biotechnology have led to the research of assembling micro components into complex microsystems and manipulation of cells, genes or similar biological components. In order to develop advanced inspection/handling systems and methods for manipulation and assembly of micro products and micro components, robust micromanipulation and microassembly strategies can be implemented on a high-speed, repetitive, reliable, reconfigurable, robust and open-architecture microassembly workstation. Due to high accuracy requirements and specific mechanical and physical laws which govern the microscale world, micromanipulation and microassembly tasks require robust control strategies based on real-time sensory feedback. Vision as a passive sensor can yield high resolutions of micro objects and micro scenes along with a stereoscopic optical microscope. Visual data contains useful information for micromanipulation and microassembly tasks, and can be processed using various image processing and computer vision algorithms. In this thesis, the initial work on the design and implementation of a vision system for microassembly workstation is introduced. Both software and hardware issues are considered. Emphasis is put on the implementation of computer vision algorithms and vision based control techniques which help to build strong basis for the vision part of the microassembly workstation. The main goal of designing such a vision system is to perform automated micromanipulation and microassembly tasks for a variety of applications. Experiments with some teleoperated and semiautomated tasks, which aim to manipulate micro particles manually or automatically by microgripper or probe as manipulation tools, show quite promising results

Visual and Kinematic Coordinated Control of Mobile Manipulating Unmanned Aerial Vehicles

Manipulating objects using arms mounted to unmanned aerial vehicles (UAVs) is attractive because UAVs may access many locations that are otherwise inaccessible to traditional mobile manipulation platforms such as ground vehicles. Historically, UAVs have been employed in ways that avoid interaction with the environment at all costs. The recent trend of increasing small UAV lift capacity and the reduction of the weight of manipulator components make the realization of mobile manipulating UAVs imminent. Despite recent work, several major challenges remain to be overcome before it will be common practice to manipulate objects from UAVs. Among these challenges, the constantly moving UAV platform and compliance of manipulator arms make it difficult to position the UAV and end-effector relative to an object of interest precisely enough for reliable manipulation. Solving this challenge will bring UAVs one step closer to being able to perform meaningful tasks such as infrastructure repair, disaster response, law enforcement, and personal assistance. Toward a solution to this challenge, this thesis describes a way forward that uses the UAV as a means to crudely position a manipulator within reach of the end-effector's goal position in the world. The manipulator then performs the fine positioning of the end-effector, rejecting position perturbations caused by UAV motions. An algorithm to coordinate the redundant degrees of freedom of an aerial manipulation system is described that allows the motions of the manipulator to serve as inputs to the UAV's position controller. To demonstrate this algorithm, the manipulator's six degrees of freedom are servoed using visual sensing to drive an eye-in-hand camera to a specified pose relative to a target while treating motions of the host platform as perturbations. Simultaneously, the host platform's degrees of freedom are regulated using kinematic information from the manipulator. This ultimately drives the UAV to a position that allows the manipulator to assume a pose relative to the UAV that maximizes reachability, thus facilitating the arm's ability to compensate for undesired UAV motions. Maintaining this loose kinematic coupling between the redundant degrees of freedom of the host UAV and manipulator allows this type of controller to be applied to a wide variety of platforms, including manned aircraft, rather than a single instance of a purpose-built system. As a result of this loose coupling, careful consideration must be given to the manipulator design so that it can achieve useful poses while minimally influencing the stability of the host UAV. Accordingly, the novel application of a parallel manipulator mechanism is described.Ph.D., Mechanical Engineering -- Drexel University, 201

Visual servo control on a humanoid robot

Includes bibliographical referencesThis thesis deals with the control of a humanoid robot based on visual servoing. It seeks to confer a degree of autonomy to the robot in the achievement of tasks such as reaching a desired position, tracking or/and grasping an object. The autonomy of humanoid robots is considered as crucial for the success of the numerous services that this kind of robots can render with their ability to associate dexterity and mobility in structured, unstructured or even hazardous environments. To achieve this objective, a humanoid robot is fully modeled and the control of its locomotion, conditioned by postural balance and gait stability, is studied. The presented approach is formulated to account for all the joints of the biped robot. As a way to conform the reference commands from visual servoing to the discrete locomotion mode of the robot, this study exploits a reactive omnidirectional walking pattern generator and a visual task Jacobian redefined with respect to a floating base on the humanoid robot, instead of the stance foot. The redundancy problem stemming from the high number of degrees of freedom coupled with the omnidirectional mobility of the robot is handled within the task priority framework, allowing thus to achieve con- figuration dependent sub-objectives such as improving the reachability, the manipulability and avoiding joint limits. Beyond a kinematic formulation of visual servoing, this thesis explores a dynamic visual approach and proposes two new visual servoing laws. Lyapunov theory is used first to prove the stability and convergence of the visual closed loop, then to derive a robust adaptive controller for the combined robot-vision dynamics, yielding thus an ultimate uniform bounded solution. Finally, all proposed schemes are validated in simulation and experimentally on the humanoid robot NAO