Showing papers on "Mobile robot published in 1989"

Using occupancy grids for mobile robot perception and navigation

Abstract: An approach to robot perception and world modeling that uses a probabilistic tesselated representation of spatial information called the occupancy grid is reviewed. The occupancy grid is a multidimensional random field that maintains stochastic estimates of the occupancy state of the cells in a spatial lattice. To construct a sensor-derived map of the robot's world, the cell state estimates are obtained by interpreting the incoming range readings using probabilistic sensor models. Bayesian estimation procedures allow the incremental updating of the occupancy grid, using readings taken from several sensors over multiple points of view. The use of occupancy grids from mapping and for navigation is examined. Operations on occupancy grids and extensions of the occupancy grid framework are briefly considered. >

Real-time obstacle avoidance for fast mobile robots

Abstract: A real-time obstacle avoidance approach for mobile robots has been developed and implemented. It permits the detection of unknown obstacles simultaneously with the steering of the mobile robot to avoid collisions and advance toward the target. The novelty of this approach, entitled the virtual force field method, lies in the integration of two known concepts: certainty grids for obstacle representation and potential fields for navigation. This combination is especially suitable for the accommodation of inaccurate sensor data as well as for sensor fusion and makes possible continuous motion of the robot with stopping in front of obstacles. This navigation algorithm also takes into account the dynamic behavior of a fast mobile robot and solves the local minimum trap problem. Experimental results from a mobile robot running at a maximum speed of 0.78 m/s demonstrate the power of the algorithm. >

Motor Schema — Based Mobile Robot Navigation

Abstract: Motor schemas serve as the basic unit of behavior specifica tion for the navigation of a mobile robot. They are multiple concurrent processes that operate in conjunction with asso ciated perceptual...

Multisensor integration and fusion in intelligent systems

Abstract: The issues involved in integrating multiple sensors into the operation of a system are presented in the context of the type of information these sensors can uniquely provide. A survey is provided of the variety of approaches to the problem of multisensor integration and fusion that have appeared in the literature in recent years ranging from general paradigms, frameworks, and methods for integrating and fusing multisensory information to existing multisensor systems used in different areas of application. General multisensor fusion methods, sensor selection strategies, and world models are examined, along with approaches to the integration and fusion of information from combinations of different types of sensors. Short descriptions of the role of multisensor integration and fusion in the operation of a number of existing mobile robots are provided, together with proposed high-level multisensory representations suitable for mobile robot navigation and control. Existing multisensor systems for industrial and other applications are considered. >

World modeling and position estimation for a mobile robot using ultrasonic ranging

Abstract: The author describes a system for dynamically maintaining a description of the limits to free space for a mobile robot using a belt of ultrasonic range sensors. A model is presented for the uncertainty inherent in such sensors, and the projection of range measurements into external Cartesian coordinates is described. Line segments are then expressed by a set of parameters represented by an estimate and a precision. A process is presented for extracting line segments from adjacent collinear range measurements, and a fast algorithm is presented for matching these line segments to a model of the limits to free space of the robot. A side effect of matching observations to a local model is a correction to the estimated position of the robot at the time that the observation was made. A Kalman filter update equation is developed to permit the correspondence of a line segment to the model to be applied as a correction to estimated position. Examples of segment extraction, position correction and modeling are presented using real ultrasonic data. >

Maintaining representations of the environment of a mobile robot

Abstract: A description is given of current ideas related to the problem of building and updating three-dimensional representations of the environment of a mobile robot that uses passive vision as its main sensory modality. The authors attempt to represent both geometry and uncertainty. The authors motivate their approach by defining the problems they are trying to solve and then give some simple didactic examples. They then present a tool they think is extremely well adapted to solving most of these problems: the extended Kalman filter (EKF). The authors discuss the notions of minimal geometric representations for three-dimensional lines, planes, and rigid motions. They show how the EKF and the representations can be combined to provide solutions for some of the problems. A number of experimental results on real data are given. >

Solving time-dependent planning problems

Abstract: We are interested in constructing solutions to time-dependent planning problems: problems in which time spent planning affects the utility of the system''s performance. In a previous paper, we define a fraomework for constructing solutions to time-dependent planning problems called expectation-driven iterative refinement. In this paper, we analyze and solve a moderately complex time-dependent planning problem involving path planning for a mobile robot, as a way of exploring a methodology for applying expectation-driven iterative refinement.

Global path planning using artificial potential fields

Abstract: The author describes a path planning technique for robotic manipulators and mobile robots in the presence of stationary obstacles. The planning consists of applying potential fields around configuration-space obstacles and using these fields to select a safe path for the robot to follow. The advantage of using potential fields in path planning is that they offer a relatively fast and effective way to solve for safe paths around obstacles. In the proposed method of path planning, a trial path is chosen and then modified under the influence of the potential field until an appropriate path is found. By considering the entire path, the problem of being trapped in a local minimum is greatly reduced, allowing the method to be used for global planning. The algorithm was tried with success on many different realistic planning problems. By way of illustration, the algorithm is applied to a two-dimensional revolute manipulator, a mobile robot capable of translation only, and a mobile robot capable of both translation and rotation. >

Visual navigation and obstacle avoidance structured light system

Abstract: A vision system for a vehicle, such as a mobile robot (10) includes at least one radiation projector (14, 16) which projects a structured beam of radiation into the robot's environment. The structured beam of radiation (14a, 16a) preferably has a substantially planar pattern of sufficient width to encompass the immediate forward path of the robot and also to encompass laterally disposed areas in order to permit turning adjustments. The vision system further includes an imaging (12) sensor such as a CCD imaging device having a two-dimensional field of view which encompasses the immediate forward path of the robot. An image sensor processor (18) includes an image memory (18A) coupled to a device (18D) which is operable for accessing the image memory. Image processing is accomplished in part by triangulating the stored image of the structured beam pattern to derive range and bearing, relative to the robot, of an object being illuminated. A navigation control system (20) of the robot inputs data from at least the vision system and infers therefrom data relating to the configuration of the environment which lies in front of the robot. The navigation control system generates control signals which drive propulsion and steering motors in order to navigate the robot through the perceived environment.

Stereo vision and navigation in buildings for mobile robots

Abstract: A mobile robot that autonomously functions in a complex and previously unknown indoor environment has been developed. The omnidirectional mobile robot uses stereo vision, odometry, and contact bumpers to instantiate a symbolic world model. Finding stereo correspondences across a single epipolar line is adequate for instantiating the model. Uncertainty in sensor data is represented by a multivariate normal distribution, and uncertainty models for motion and stereo are presented. Uncertainty is reduced by extended Kalman filtering. To execute a high-level command such as 'Enter the second door on the left', a model is instantiated from sensing and motions are planned and executed. Experimental results from the fast, running system are presented. >

Vision-guided servoing with feature-based trajectory generation (for robots)

Abstract: The authors present a vision module which is able to guide an eye-in-hand robot through general servoing and tracking problems using off-the-shelf image-processing equipment. The vision module uses the location of binary image features from a camera on the robot's end-effector to control the position and one degree of orientation of the robot manipulator. A unique feature-based trajectory generator provides smooth motion between the actual image features and the desired image features even with asynchronous and discontinuous vision updates. By performing the trajectory generation in image feature space, image-processing constraints such as the feature extraction time can be accounted for when determining the appropriate segmentation and acceleration times of the trajectory. Experimental results of a PUMA robot tracking objects with vision feedback are discussed. >

A hierarchical strategy for path planning among moving obstacles

Abstract: Absrracr-A method is presented for planning a path in the presence of moving obstacles. Given a set of polygonal moving obstacles, we focus on generating a path for a mobile robot that navigates in the twodimensional plane. Our methodology is to include time as one of the dimensions of the model world. This allows us to regard the moving obstacles as being stationary in the extended world. For a solution to be feasible, the robot must not collide with any other moving obstacles, and, also, it must navigate without exceeding the predetermined range of velocity, acceleration, and centrifugal force. We investigate an appropriate model to represent the extended world for the path planning task, and give a time-optimal solution using this model.

A fine-grained alternative to the subsumption architecture for mobile robot control

Abstract: An architecture is presented for robot control which can be viewed as a very fine-grained layered architecture motivated by the principles underlying the subsumption architecture. The subsumption architecture provides a powerful means for defining intelligent robot control mechanisms through the layered composition of simple behaviors. However, the authors have found that there are basic limitations inherent in this architecture due to the inaccessibility of information internal to a behavior. While adhering to the basic concept of building a robot control system through successive layers of competence, task-achieving behavior in this system is fragmented into many smaller decision-making units. Each of these units simply has the task of transforming a set of input activations into an output activation, so that the role that any unit plays in the system is defined entirely by how it is connected to other units. This fine-grained nature of the architecture permits a more flexible arbitration of commands between behaviors and provides incrementally added behaviors with complete access to the internal state of existing behaviors. >

On non-holonomie mobile robots and optimal maneuvering

Abstract: Les resultats de geometrie differentielle et de controle non lineaire sont utilises pour resoudre le probleme de decision lie a la planification de trajectoires de robots non holonomes. La preuve, non constructive, est completee par la presentation d'un planificateur utilisant une discretisation de l'espace des phases (configurations et vitesses).

Fast, Cheap and Out of Control: a Robot Invasion of the Solar System

Abstract: Complex systems and complex missions take years of planning and force launches to become incredibly expensive. The longer the planning and the more expensive the mission, the more catastrophic if it fails. The solution has always been to plan better, add redundancy, test thoroughly and use high quality components. Based on our experience in building ground based mobile robots (legged and wheeled) we argue here for cheap, fast missions using large numbers of mass produced simple autonomous robots that are small by today's standards (1 to 2 Kg). We argue that the time between mission conception and implementation can be radically reduced, that launch mass can be slashed, that totally autonomous robots can be more reliable than ground controlled robots, and that large numbers of robots can change the tradeoff between reliability of individual components and overall mission success. Lastly, we suggest that within a few years it will be possible at modest cost to invade a planet with millions of tiny robots.

Fast motion planning for multiple moving robots

Abstract: The author presents an efficient solution to the motion-planning problem for multiple translating robots in the plane. It is shown that careful priority assignment can greatly reduce the average running time of the planner. A priority assignment method is introduced which attempts to maximize the number of robots which can move in a straight line form their start point to their goal point, thereby minimizing the number of robots for which expensive collision-avoiding search is necessary. This prioritization method is extremely effective in sparse workspaces where the moving robots are the primary obstacle. >

On the Kinematics of Wheeled Mobile Robots

Abstract: A wheeled mobile robot is here modelled as a planar rigid body that rides on an arbitrary number of wheels. The rela tionship between the rigid body motion of the robot and the steering and drive rates of wheels is developed. In particular, conditions are obtained that guarantee that rolling without skidding or sliding can occur. Explicit differential equations are derived to describe the rigid body motions that arise in such ideal rolling trajectories. The simplest wheel configura tion that permits access of arbitrary rigid-body motions is determined. Then the question of slippage due to misalign ment of the wheels is investigated by minimization of a non- smooth convex dissipation functional that is derived from Coulomb's Law offriction. It is shown that this minimization principle is equivalent to the construction of quasi-static motions. Examples are presented to illustrate the models.

Mobile robot navigation employing retroreflective ceiling features

Abstract: Apparatus and method which provides for the determination of a vehicle's orientation and position in an environment, such as a hallway, from an image of a retroreflective ceiling feature. A mobile robot 10 includes a light source 28 and a camera 12 that are pitched up obliquely at an intermediate angle between a horizon and a zenith. The camera views a ceiling having one or more strip-like retroreflective features 16 which are preferably aligned with an axis of the hallway. In that the feature presents a pattern or alignment which is substantially parallel to a long axis of the hallway the pattern is detected and processed to derive robot navigation information therefrom.

A robot that walks; emergent behaviors from a carefully evolved network

Abstract: The author describes a carefully designed series of networks, each one being a strict augmentation of the previous one, which control a six-legged walking machine capable of walking over rough terrain and following a person passively sensed in the infrared spectrum As the completely decentralized networks are augmented, the robot's performance and behavior repertoire demonstrably improve The rationale for such demonstrations is that they can help identify requirements for automatically building massive networks to carry out complex sensory-motor tasks The experiments with an actual robot ensure that an essence reality is maintained and that no critical disabling problems have been ignored The present work is based on the drawing of analogies between evolution in the animal world and robotic evaluation >

A hierarchical strategy for path planning among moving obstacles (mobile robot)

Abstract: A method is presented for planning a path in the presence of moving obstacles. Given a set of polygonal moving obstacles, the authors focus on generating a path for a mobile robot that navigates in the two-dimensional plane. Their methodology is to include time as one of the dimensions of the model world. This enables the authors to regard the moving obstacles as being stationary in the extended world. For a solution to be feasible, the robot must not collide with any other moving obstacles, and, also, it must navigate without exceeding the predetermined range of velocity, acceleration, and centrifugal force. The authors investigate an appropriate model to represent the extend world for the path-planning task, and give a time-optimal solution using this model. >

Design Of An Autonomous And Distributed Robot System: Actress

Abstract: A new concept of an advanced robot system, ACTRESS (ACTor-based Robots and Equipments Synthetic System), is presented in this paper. ACTRESS is an autonomous and distributed robot system composed of multi robotic elements. Each element is provided with functions to make decisions with understanding the target of tasks, recognizing surrounding environments, acting, and managing its own conditions, and to communicate with any other components. In order to manage multiple elements to achieve any given task targets, the protocol for communication between elements is discussed for cooperative action between arbitrary elements. This paper deals with the conceptual design of ACTRESS, focusing on the methodology for synthesizing the autonomous and distributed system. Also based on an assumption that mobility is the indispensable function for advanced robot systems, an experimental system using micro mouse"'^ is developed as a primitive example of ACTRESS.

Structure decision method for self organising robots based on cell structures-CEBOT

Abstract: A dynamically reconfigurable robotic system (DRRS) is one that can reconfigure itself to an optimal structure, depending on the purpose and environment. To realize this concept, the authors propose CEBOT (cell structured robot), which is a distributed robotic system consisting of separable autonomous units. These functional cells are able to communicate with each other and to approach, connect, and separate automatically. If single cells of CEBOT are damaged, they can be repaired or replaced automatically. Since CEBOT is capable of adapting itself to changing environments, it is a very flexible system applicable in space, factory, and hostile environments. The authors propose an optimal structure decision method that can determine cell type, arrangement, degree of freedom, and link length. It is applicable to fixed-base and mobile-base manipulators. A structure evaluation function, which is the sum of parameters relating to the number of work points, required positioning accuracy, torque, distance between given work points, and cell cost, is presented. Simulation results are given. >

Task-level planning of pick-and-place robot motions

Abstract: A task-level robot system named Handey, which is under development, is described. The current system is limited to pick-and-place operations, and it has successfully carried out dozens of such operations involving a variety of parts in relatively complex environments. The pick-and-place problem is described, and approximate approaches to the problem are examined. Heuristic motion planning in Handey is then discussed. >

Sensor fusion in certainty grids for mobile robots

Abstract: A numeric representation of uncertain and incomplete sensor knowledge called certainty grids was used successfully in several recent mobile robot control programs developed at the Carnegie-Mellon University Mobile Robot Laboratory (MRL). Certainty grids have proven to be a powerful and efficient unifying solution for sensor fusion, motion planning, landmark identification, and many other central problems. MRL had good early success with ad hoc formulas for updating grid cells with new information. A new Bayesian statistical foundation for the operations promises further improvement. MRL proposes to build a software framework running on processors onboard the new Uranus mobile robot that will maintain a probabilistic, geometric map of the robot's surroundings as it moves. The certainty grid representation will allow this map to be incrementally updated in a uniform way based on information coming from various sources, including sonar, stereo vision, proximity, and contact sensors. The approach can correctly model the fuzziness of each reading and, at the same time, combine multiple measurements to produce sharper map features; it can also deal correctly with uncertainties in the robot's motion. The map will be used by planning programs to choose clear paths, identify locations (by correlating maps), identify well-known and insufficiently sensed terrain, and perhaps identify objects by shape. The certainty grid representation can be extended in the time dimension and used to detect and track moving objects. Even the simplest versions of the idea allow us to fairly straightforwardly program the robot for tasks that have hitherto been out of reach. MRL looks forward to a program that can explore a region and return to its starting place, using map "snapshots" from its outbound journey to find its way back, even in the presence of disturbances of its motion and occasional changes in the terrain.

An Experimental System for Incremental Environment Modelling by an Autonomous Mobile Robot

Abstract: Incremental map-making is a necessary function of an autonomous mobile robot Sensor data are always imprecise, and in the case of a mobile robot, sensor location is itself imprecise and even sometimes false (eg in case of slippage) We show how sensors data inaccuracies can be processed to produce a consistent environment model and an as precise as possible robot positioning The experimental system (a mobile robot with a laser range finder and odometry) is presented and the theoretical approach is applied on actual data

On nonholonomic mobile robots and optimal maneuvering

Abstract: The authors consider the robot path planning problem in the presence of nonintegrable kinematic constraints, known as nonholonomic constraints. Such constraints are generally caused by one or several rolling contacts between rigid bodies and express that the relative velocity of two points in contact is zero. They make the dimension of the space of achievable velocities smaller than the dimension of the robot's configuration space. Using standard results in differential geometry (Frobenius integrability theorem) and nonlinear control theory, the authors first give a formal characterization of holonomy (and nonholonomy) for robot systems subject to linear differential constraints and state some related results about their controllability. They then apply these results to 'car-like' and 'trailer-like' robots. Finally, they present an implemented planner, which generates collision-free paths with a minimal number of maneuvers for car-like and trailer-like robots among obstacles. >

Mobile robot localization using a single image

Abstract: Following and extending the approach of K. Sugihara (1988), the author assumes that a mobile robot is equipped with a single camera and a map marking the positions in its environment of landmarks. The robot moves on a flat surface, acquires one image, extracts vertical edges from it, and computes the directions to visible landmarks. The problem is to determine the robot's position and orientation (pose) by establishing the correspondence between landmark directions and points in the map. This approach capitalizes on the excellent angular resolution of standard CCD cameras, while avoiding the feature-correspondence and 3D reconstruction problems. The problem is formulated as a search in a tree of interpretations (pairings of landmark directions and landmark points), and an algorithm to search the tree efficiently to determine the solution poses(s) is developed, taking into account errors in the landmark directions extracted by image processing. Quantitative results from simulations and experiments with real imagery are presented. >

The robotics review 1

Abstract: Part 1 Programming, planning, and learning: articles - motion planning in the presence of moving obstacles, Jean-Claude Latombe, minimal length curves and optimal paths, Jean-Daniel Boissonat, task level robot programming - on the HANDEY system, Jocelyne Pertin-Troccaz reviews - robot motion planning, Jean-Claude Latombe, John Canny, planar sliding with dry friction, Suresh Goyal, et al. Part 2 Sensing and perception: articles - touch sensing for robotic manipulation and recognition, Robert D. Howe and Mark R. Cutkosky, sensor planning for robotic vision - a review, Konstantinos (Dino) Tarabanis and Rober Y. Tsai, solving for 3-D model parameters from the locations of image features, David Lowe, modeling sonar sensors, Hugh F. Durrant-Whyte and John J. Leonard reviews - authenticating edges produced by zero-crossing algorithms, James J. Clark and Harlyn Baker a few steps toward artificial 3-D vision, Olivier D. Faugeras, W. Eric L. Grimson. Part 3 Kinematics and dynamics: articles - wrist singularities - theory and practice, Charles Wampler reviews - kinematic analysis and design of redundant manipulators, Joel W. Burdick and Vincent Hayward, singular configurations of parallel manipulators and Grassman geometry, Jean-Pierre Merlet and Jorge Angeles, a spatial operator algebra for manipulator modeling and control, G. Rodriquez, et al on the inverse kinematics of redundant manipulators, Daniel R. Baker, et al duality in mechanical properties of sequential and parallel manipulators, Vladimir Zamanov, et al. Part 4 Motion and force control: articles - time-optimal motions of robot manipulators including dynamics, Marc Renaud and J. Yves Fourquet, the state of the art of robot learning control using artificial neural networks - an overview, V.D. Sanchez A. and G. Hirzinger reviews - the application of model-referenced adaptive control to robotic manipulators, S. Dubowsky, et al is adaptive control necessary for manipulation robots, and if so, to what extent?, D. Stokic, et al. Part 5 Design, technology, and applications: articles - a comparative analysis of actuator technologies for robotics, John M. Hollerback, et al, microrobotics - shifting robotics technology toward a different scale world, Paolo Dario and Renzo Valleggi reviews - robotics in service, Joseph F. Engelberger and Russell H. Taylor.

A behavior-based arm controller

Abstract: The author presents a working, implemented controller for an actual mobile robot arm. The goal of the system is to locate and retrieve empty soda cans in an unstructured environment using a variety of local sensors. The controller, however, is not a centralized sequential program, but rather a collection of 15 independent behaviors. Each of these behaviors contains some grain of expertise concerning the collection task and cooperates with the others to accomplish its goal. These behaviors run concurrently, in real time, on a set of eight loosely coupled on-board 8-bit microprocessors. The author describes the methodology used to decompose the collection task and discusses the types of implicit spatial representation and reasoning used by the system. >