Visual Servoing Path Planning for Cameras Obeying the Unified Model

Abstract

This paper proposes a path planning visual servoing strategy for a class of cameras that includes conventional perspective cameras, fisheye cameras and catadioptric cameras as special cases. Specifically, these cameras are modeled by adopting a unified model recently proposed in the literature and the strategy consists of designing image trajectories for eye-in-hand robotic systems that allow the robot to reach a desired location while satisfying typical visual servoing constraints. To this end, the proposed strategy introduces the projection of the available image features onto a virtual plane and the computation of a feasible image trajectory through polynomial programming. Then, the computed image trajectory is tracked by using an image-based visual servoing controller. Experimental results with a fisheye camera mounted on a 6-d.o.f. robot arm are presented in order to illustrate the proposed strategy.     

鱼眼投影在虚拟实景中的应用研究

为了生成大视野的虚拟场景扣逼真的模拟球面，本文把鱼眼投影应用到虚拟实景中，给出由经纬映射图像生成角鱼眼投影的算法，并且在实现了三维浏览扣缩放，最后通过实例证明了鱼眼投影虚拟空间的效果．     

Using Virtual Pheromones and Cameras for Dispersing a Team of Multiple Miniature Robots

To safely and efficiently guide personnel of search and rescue operations in disaster areas, swift gathering of relevant information such as the locations of victims, must occur. Using the concept of ‘repellent virtual pheromones’ inspired by insect colony coordination behaviors, miniature robots can be quickly dispersed to survey a disaster site. Assisted by visual servoing, dispersion of the miniature robots can quickly cover an area. An external observer such as another robot or an overhead camera is brought into the control loop to provide each miniature robot estimations of the positions of all of the other near-by robots in the robotic team. These miniature robots can then move away from the other near-by robots on the team, resulting in the robot collective becoming swiftly distributed through the local area. The technique has been simulated with differing pheromone persistence levels and implemented using the miniature Scout robots, developed by the Center for Distributed Robotics at the University of Minnesota, which are well-suited to surveillance and reconnaissance missions.     

普通数码相机三种检校方法的量测精度评价

普通数码相机常用的检校方法存在参数解算不稳定,或对控制场要求高,或实施难度大等不足。本文通过不同拍摄距离下的量测精度对比实验,依据控制场布设难度、检校计算稳定性以及量测应用精度等3方面指标,分析评价普通数码相机3种检校方法的特性。研究结果表明:光束法适用于精密控制条件下的相机检校,但解算的稳定性欠佳;PTR方法的检校精度与光束法相当,且计算稳定性较高;MSC方法适用于小型平面控制下的检校,量测精度能满足一般的工程量测需求。     

On the potential contributions of hybrid intelligent approaches to Multicomponent Robotic System development

The area of cognitive or intelligent robotics is moving from the single monolithic robot control and behavior problem to that of controlling robots with multiple components or multiple robots operating together, and even collaborating, in dynamic and unstructured environments. This paper introduces the topic and provides a general overview of the current state of the field of Multicomponent Robotic Systems focusing on providing some insights into where Hybrid Intelligent Systems could provide key contributions to its advancement. Thus, the aim is to identify prospective research areas and to try to delimit the field from the point of view of the following essential problem: how to coordinate multiple robotic elements in order to perform useful tasks.     

摄像机线性模型标定中一种投影矩阵的修正方法

线性模型摄像机标定中,由于不考虑非线性畸变,使投影矩阵存在着标定误差,并影响三维重建的精度。在分析投影矩阵标定过程的基础上,提出了一种修正方法,它是将三维重建误差折算到投影矩阵中,通过解超定线性方程组求出参数的偏差值并构造新的投影矩阵。用修正后的矩阵进行三维重建,提高了重建的精度。     

A Generic and Provably Convergent Shape-from-Shading Method for Orthographic and Pinhole Cameras

We describe a mathematical and algorithmic study of the Lambertian “Shape-From-Shading” problem for orthographic and pinhole cameras. Our approach is based upon the notion of viscosity solutions of Hamilton-Jacobi equations. This approach provides a mathematical framework in which we can show that the problem is well-posed (we prove the existence of a solution and we characterize all the solutions). Our contribution is threefold. First, we model the camera both as orthographic and as perspective (pinhole), whereas most authors assume an orthographic projection (see Horn and Brooks (1989) for a survey of the SFS problem up to 1989 and Zhang et al. (1999), Kozera (1998), Durou et al. (2004) for more recent ones); thus we extend the applicability of shape from shading methods to more realistic acquisition models. In particular it extends the work of Prados et al. (2002a) and Rouy and Tourin (1992). We provide some novel mathematical formulations of this problem yielding new partial differential equations. Results about the existence and uniqueness of their solutions are also obtained. Second, by introducing a “generic” Hamiltonian, we define a general framework allowing to deal with both models (orthographic and perspective), thereby simplifying the formalization of the problem. Thanks to this unification, each algorithm we propose can compute numerical solutions corresponding to all the modeling. Third, our work allows us to come up with two new generic algorithms for computing numerical approximations of the “continuous solution of the “Shape-From-Shading” problem as well as a proof of their convergence toward that solution. Moreover, our two generic algorithms are able to deal with discontinuous images as well as images containing black shadows. First online version published in October, 2005     

Dynamic Analysis and Distributed Control of the Tetrobot Modular Reconfigurable Robotic System

Reconfigurable robotic systems can be adapted to different tasks or environments by reorganizing their mechanical configurations. Such systems have many redundant degrees of freedom in order to meet the combined demands of strength, rigidity, workspace kinematics, reconfigurability, and fault tolerance. In order to implement these new generations of robotic system, new approaches must be considered for design, analysis, and control. This paper presents an efficient distributed computational scheme which computes the kinematics, dynamics, redundancy resolution, and control inputs for real-time application to the control of the Tetrobot modular reconfigurable robots. The entire system is decomposed into subsystems based on a modular approach and Newton's equations of motion are derived and implemented using a recursive propagation algorithm. Two different dynamic resolution of redundancy schemes, the centralized Jacobian method and the distributed virtual force method, are proposed to optimize the actuating forces. Finally, distributed dynamic control algorithms provide an efficient modular implementation of the control architecture for a large family of configurations.     

Robotic Optimization and Testing for the Formula One Tire-Changing Robot

Robotics experiences tremendous evolutions every year. Once a topic is mainly approached at research centers, read through highly specialized books and viewed distantly on scientific channels, nowadays it is a common and very approachable subject among undergraduate students of many universities. More and more robots are being designed every day, demanding technological implementation and production. This progress does not come without its glitches, however. A common and increasing problem that appears is the insufficient testing, simulation and optimization steps that a robotic construction needs to pass in order to achieve an efficient design. These steps prove to be difficult and sometimes discouraging, resulting in laborious work, due to lack of tools. This paper presents an example of a robotic optimization and testing, using a generic software package, applied on a custom manipulator, a tire-changing robot. Although the manipulator is designed with its own simulation and control package, it may lack optimality or validity. We implemented a different software package, focused on optimization and control of simple generic robots (XXX.RRR types) and apply the package on the tire-changer manipulator. The results provide improvements for the primary controlling software and confirm its correctness.     

Force Control of Robotic Manipulators Using a Fuzzy Predictive Approach

This paper proposes a force control strategy for robotic manipulators considering a non-rigid environment described by a nonlinear model. This approach uses a fuzzy predictive algorithm to generate, in an optimal way, the reference or virtual position to the classical impedance controller in order to apply a desired force profile on the environment. The main advantage of this control strategy is the possibility of including a nonlinear model of the environment in the controller design in a straightforward way, improving the global force control performance, especially in non-rigid environments. Moreover, in order to reduce the oscillations on the optimized reference position a fuzzy scaling machine is included on the force control strategy. The performance of the force control scheme is illustrated for a two degree-of-freedom PUMA 560 robot, which end-effector is forced to move along a flat surface located on the vertical plane. The simulation results obtained with the fuzzy control scheme reveal significant improvement in the force tracking performance, when compared to the impedance control with force tracking in non-rigid environments.     

群机器人多目标搜索中的合作协同和竞争协同

群机器人进行多目标搜索时,通过任务分工形成多个子群,各子群分别针对一个意向目标协同搜索,故围绕子群协同中存在的合作关系和竞争关系提出控制策略.为进行合作协同,建立子群发言人的动态遴选机制,不同子群的发言人进行通信,交换所属各子群的最优信息,引导本子群的搜索行为;为进行竞争协同,引入承包机制,按子群的优势地位高低决定是承包还是放弃对某些目标的搜索.两类协同控制的仿真结果表明,合作协同扩大了机器人的感知范围,竞争协同降低了空间冲突机率.二者综合作用,明显提高了群机器人的搜索效率.     

A Unified Theory of Uncalibrated Stereo for Both Perspective and Affine Cameras

This paper addresses the recovery of structure and motion from uncalibrated images of a scene under full perspective or under affine projection. Particular emphasis is placed on the configuration of two views, while the extension to $N$ views is given in Appendix. A unified expression of the fundamental matrix is derived which is valid for any projection model without lens distortion (including full perspective and affine camera). Affine reconstruction is considered as a special projective reconstruction. The theory is elaborated in a way such that everyone having knowledge of linear algebra can understand the discussion without difficulty. A new technique for affine reconstruction is developed, which consists in first estimating the affine epipolar geometry and then performing a triangulation for each point match with respect to an implicit common affine basis.     

A computational framework for simulation of Underwater Robotic Vehicle systems

This paper presents a computational framework for efficiently simulating the dynamics and hydrodynamics of Underwater Robotic Vehicle (URV) systems. Through the use of object-oriented mechanisms, a very general yet efficient version of the Articulated-Body (AB) algorithm has been implemented. An efficient solution to branching within chains is developed in the paper so that the algorithm can be used to compute the dynamics for the entire class of open-chain, tree-structured mechanisms. By including compliant contacts with the environment, most closed-chain systems can also be modeled. URV systems with an extended set of topologies can be simulated including proposed underwater walking machines with intra-body powered articulations. Using the encapsulation inherent in C++, the hydrodynamics code has been confined to a single class, thereby explicitly defining this framework and providing an environment for readily implementing desired hydrodynamics algorithms. Resulting simulations are very efficient and can be used in a number of applications both in the development and use of URV systems.     

Applying an Agent-Oriented Methodology to the Design of Artificial Organizations: A Case Study in Robotic Soccer

The multi-agent paradigm is widely used to provide solutions to a number of organizational problems related to the collective achievement of one or more tasks. All these problems share a common difficulty of design: how to proceed from the global specification of a collective task to the specification of the local behaviors to be provided to the agents? We have defined the Cassiopeia method whose specificity is to articulate the design of a multi-agent system around the notion of organization. This paper reports the use of this method for designing and implementing the organization of a soccer-playing robotic team. We show why we chose this application and how we designed it, and we discuss its interest and inherent difficulties in order to clearly express the needs for a design methodology dedicated to DAI.     

基于环视图象的数字相机内参数自定标方法

描述了一种适用于IBR系统的数字相机内参数自定标方法。该方法基于跟踪机机旋转得到的图象系列的特征匹配点以,而不需要标定物。认定在相机旋转过程中,其光学中心是稳定不变的,也即图象中心是固定的,可以事先定标;但容许相机的焦距在各幅图象间有变化,利用真实图象序列进行了实验验证,表明该方法能鲁棒地估算相机内参数。     

建立软件评测实验室一元化技术能力标准的方法

探讨了建立软件评测实验室一元化技术能力标准的一个方法,该方法的实质是在软件质量度量模型与软件测试模型之间建立一种定量映射关系,将目前软件评测实验室技术能力的两个事实标准归化为一体,最终将ISO／IEC 9126标准作为软件评测实验室的一元化技术能力标准。     

Identical Projective Geometric Properties of Central Catadioptric Line Images and Sphere Images with Applications to Calibration

Central catadioptric cameras are imaging devices that use mirrors to enhance the field of view while preserving a single effective viewpoint. Lines and spheres in space are all projected into conics in the central catadioptric image planes, and such conics are called line images and sphere images, respectively. We discovered that there exists an imaginary conic in the central catadioptric image planes, defined as the modified image of the absolute conic (MIAC), and by utilizing the MIAC, the novel identical projective geometric properties of line images and sphere images may be exploited: Each line image or each sphere image is double-contact with the MIAC, which is an analogy of the discovery in pinhole camera that the image of the absolute conic (IAC) is double-contact with sphere images. Note that the IAC also exists in the central catadioptric image plane, but it does not have the double-contact properties with line images or sphere images. This is the main reason to propose the MIAC. From these geometric properties with the MIAC, two linear calibration methods for central catadioptric cameras using sphere images as well as using line images are proposed in the same framework. Note that there are many linear approaches to central catadioptric camera calibration using line images. It seems that to use the properties that line images are tangent to the MIAC only leads to an alternative geometric construction for calibration. However, for sphere images, there are only some nonlinear calibration methods in literature. Therefore, to propose linear methods for sphere images may be the main contribution of this paper. Our new algorithms have been tested in extensive experiments with respect to noise sensitivity.     

统一身份管理在网络中的服务模型分析

基于身份管理和服务的相结合对网络中的统一身份管理服务进行分析。通过介绍组成身份管理模型的关键定义,提出统一身份服务模型图,再综合网络空间中物联网的技术框架和移动互联网的网络结构,分别提出适用物联网和移动互联网的统一身份服务模型。