Showing papers on "Robot published in 1993"

Elastic bands: connecting path planning and control

Abstract: Elastic bands are proposed as the basis for a framework to close the gap between global path planning and real-time sensor-based robot control. An elastic band is a deformable collision-free path. The initial shape of the elastic is the free path generated by a planner. Subjected to artificial forces, the elastic band deforms in real time to a short and smooth path that maintains clearance from the obstacles. The elastic continues to deform as changes in the environment are detected by sensors, enabling the robot to accommodate uncertainties and react to unexpected and moving obstacles. While providing a tight connection between the robot and its environment, the elastic band preserves the global nature of the planned path. The framework is outlined, and an efficient implementation based on bubbles is discussed. >

Neural Network Perception for Mobile Robot Guidance

Abstract: From the Publisher: Vision based mobile robot guidance has proven difficult for classical machine vision methods because of the diversity and real time constraints inherent in the task. This book describes a connectionist system called ALVINN (Autonomous Land Vehicle In a Neural Network) that overcomes these difficulties. ALVINN learns to guide mobile robots using the back-propagation training algorithm. Because of its ability to learn from example, ALVINN can adapt to new situations and therefore cope with the diversity of the autonomous navigation task. But real world problems like vision based mobile robot guidance present a different set of challenges for the connectionist paradigm. Among them are: how to develop a general representation from a limited amount of real training data, how to understand the internal representations developed by artificial neural networks, how to estimate the reliability of individual networks, how to combine multiple networks trained for different situations into a single system, and how to combine connectionist perception with symbolic reasoning. Neural Network Perception for Mobile Robot Guidance presents novel solutions to each of these problems. Using these techniques, the ALVINN system can learn to control an autonomous van in under 5 minutes by watching a person drive. Once trained, individual ALVINN networks can drive in a variety of circumstances, including single-lane paved and unpaved roads, and multi-lane lined and unlined roads, at speeds of up to 55 miles per hour. The techniques also are shown to generalize to the task of controlling the precise foot placement of a walking robot.

Mobile Robot Miniaturisation: A Tool for Investigation in Control Algorithms

Abstract: The interaction of an autonomous mobile robot with the real world critically depends on the robots morphology and on its environment Building a model of these aspects is extremely complex, making simulation insufficient for accurate validation of control algorithms

A robot exploration and mapping strategy based on a semantic hierarchy of spatial representations

Abstract: Kuipers, B. and Byun, Y.T., A robot exploration and mapping strategy based on a semantic hierarchy of spatial representations, Robotics and Autonomous Systems, 8 (1991) 47-63. We have developed a robust qualitative method for robot exploration, mapping, and navigation in large-scale spatial environments. Experiments with a simulated robot in a variety of complex 2D environments have demonstrated that our qualitative method can build an accurate map of a previously unknown environment in spite of substantial random and systematic sensorimotor error. Most current approaches to robot exploration and mapping analyze sensor input to build a geometrically precise map of the environment, then extract topological structure from the geometric description. Our approach recognizes and exploits qualitative properties of large-scale space before relatively error-prone geometrical properties. [sensorimotor ~ control] ~ topology ---, geometry At the control level, distinctive places and distinctive travel edges are identified based on the interaction between the robot's control strategies, its sensorimotor system, and the world. A distinctive place is defined as the local maximum of a distinctiveness measure appropriate to its immediate neighborhood, and is found by a hill-climbing control strategy. A distinctive travel edge, similarly, is defined by a suitable measure and a path-following control strategy. The topological network description is created by linking the distinctive places and travel edges. Metrical information is then incrementally assimilated into local geometric descriptions of places and edges, and finally merged into a global geometric map. Topological ambiguity arising from sensorily indistinguishable places can be resolved at, the topological level by the exploration strategy. With this representation, successful navigation is not critically dependent on the accuracy, or even the existence, of the geometrical description. We present examples demonstrating the process by which the robot explores and builds a map of a complex environment, including the effect of sensory errors. We also discuss new research directions that are suggested by this approach.

A passivity approach to controller-observer design for robots

Abstract: Passivity-based control methods for robots, which achieve the control objective by reshaping the robot system's natural energy via state feedback, have, from a practical point of view, some very attractive properties. However, the poor quality of velocity measurements may significantly deteriorate the control performance of these methods. In this paper the authors propose a design strategy that utilizes the passivity concept in order to develop combined controller-observer systems for robot motion control using position measurements only. To this end, first a desired energy function for the closed-loop system is introduced, and next the controller-observer combination is constructed such that the closed-loop system matches this energy function, whereas damping is included in the controller- observer system to assure asymptotic stability of the closed-loop system. A key point in this design strategy is a fine tuning of the controller and observer structure to each other, which provides solutions to the output-feedback robot control problem that are conceptually simple and easily implementable in industrial robot applications. Experimental tests on a two-DOF manipulator system illustrate that the proposed controller-observer systems enable the achievement of higher performance levels compared to the frequently used practice of numerical position differentiation for obtaining a velocity estimate. >

Trajectory tracking for unicycle-type and two-steering-wheels mobile robots

Abstract: Through two different approaches, this report proposes two general controllers for unicycle-type and two-steering-wheels mobile robots. For both systems, conditions for asymptotical convergence to a predefined path are established and simulation results are presented. Rather than writing the systems' equations with respect to a fixed reference frame, the robot state is here parametrized relative to the followed path, in terms of distance and orientation.

Sensor-based space robotics-ROTEX and its telerobotic features

Abstract: In early 1993 the space robot technology experiment ROTEX was flown with space-shuttle Columbia. A multisensory robot onboard the spacecraft successfully worked in autonomous modes, teleoperated by astronauts, as well as in different telerobotic ground control modes. These included online teleoperational and telesensor-programming: a task-level oriented programming technique involving learning-by-showing concepts in a virtual environment. The robot's key features were its multisensory gripper and the local sensory feedback schemes that are the basis for shared autonomy. The corresponding man-machine interface concepts, which use a six-degree-of-freedom non-force-reflecting control ball and visual feedback to the human operator, are explained. Stereographic simulation on the ground was used to predict not only the robot's free motion but even the sensor-based path refinement onboard. Prototype tasks performed by this space robot were the assembly of a truss structure, connecting/disconnecting an electrical plug (orbit replaceable unit exchange), and grasping free-floating objects. >

Collective robotics: from social insects to robots

Abstract: Achieving tasks with multiple robots will require a control system that is both simple and scalable as the number of robots increases. Collective behavior as demonstrated by social insects is a form of decentralized control that may prove useful in controlling multiple robots. Nature's several examples of collective behavior have motivated our approach to controlling a multiple robot system using a group behavior. Our mechanisms, used to invoke the group behavior, allow the system of robots to perform tasks without centralized control or explicit communication. We have constructed a system of five mobile robots capable of achieving simple collective tasks to verify the results obtained in simulation. The results suggest that decentralized control without explicit communication can be used to perform cooperative tasks requiring a collective behavior.

Intelligent behavior in animals and robots

Abstract: Intelligent behaviour rational behaviour utility state and cost design and decision motivation and autonomy goals and behaviour accomplishing tasks prerequisites for an autonomous robot the goal function in robot architecture animal and robot learning conclusions.

Nonholonomic multibody mobile robots: Controllability and motion planning in the presence of obstacles

Abstract: We consider mobile robots made of a single body (car-like robots) or several bodies (tractors towing several trailers sequentially hooked). These robots are known to be nonholonomic, i.e., they are subject to nonintegrable equality kinematic constraints involving the velocity. In other words, the number of controls (dimension of the admissible velocity space), is smaller than the dimension of the configuration space. In addition, the range of possible controls is usually further constrained by inequality constraints due to mechanical stops in the steering mechanism of the tractor. We first analyze the controllability of such nonholonomic multibody robots. We show that the well-known Controllability Rank Condition Theorem is applicable to these robots even when there are inequality constraints on the velocity, in addition to the equality constraints. This allows us to subsume and generalize several controllability results recently published in the Robotics literature concerning nonholonomic mobile robots, and to infer several new important results. We then describe an implemented planner inspired by these results. We give experimental results obtained with this planner that illustrate the theoretical results previously developed.

Optimal and Efficient Path Planning for Unknown and Dynamic Environments

Abstract: : The task of planning trajectories for a mobile robot has received considerable attention in the research literature. Algorithms exist for handling a variety of robot shapes, configurations, motion constraints, and environments. Most of the work assumes the robot has a complete and accurate model of its environment before it begins to move; less attention has been paid to the problem of unknown or partially-known environments. This situation occurs for an exploratory robot or one that must move to a goal location without the benefit of a floorplan (indoor) or terrain map (outdoor). Existing approaches plan an initial global path or route based on known information and then modify the plan locally as the robot discovers obstacles with its sensors. While this strategy works well in environments with small, sparse obstacles, it can lead to grossly suboptimal and incomplete results in cluttered spaces. An alternative approach is to replan the global path from scratch each time a new obstacle is discovered.

Mobile robots: inspiration to implementation

Abstract: Revised and updated, the second edition includes several new chapters with projects and applications. The authors keep pace with the ever-growing and rapidly expanding field of robotics. The new edition reflects technological developments and includes programs and activities for robot enthusiasts. Using photographs, illustrations, and informative text, Mobile Robots guides the reader through the step-by-step process of constructing two different and inexpensive yet fully functional robots.

Estimating friction using incipient slip sensing during a manipulation task

Abstract: A scheme is presented by which a manipulator can use dynamic tactile sensing to detect when it is about to lose hold of a grasped object. By detecting localized slips on the gripping surface which precede gross slip, the controller can modify the grasp force to prevent the object from slipping. Also, by monitoring normal and tangential forces at the contact when these incipient slip signals occur, the controller obtains an accurate estimate of the friction coefficient which can then be used during the manipulation task. Accurate knowledge of the friction coefficient is essential when grasping fragile objects or manipulating with sliding. >

Toward the development of a material transport system using swarms of ant-like robots

Abstract: A decentralized method for controlling a homogeneous swarm of autonomous mobile robots that collectively transport a single palletized load is proposed. The small tank-like robots have no advanced sensory or communications capabilities. They have no information on the position or number of other robots transporting the small pallet. Instead, all information needed by the robots is derived from the dynamics inherent when the system of robots is contacting a common rigid body. Each robot derives the required local information from a force sensor mounted at the point at which it contacts the pallet. A distributed control law is derived, and the resulting stable behavior of the system is verified by computer simulation. >

Real-time collision avoidance in teleoperated whole-sensitive robot arm manipulators

Abstract: The problem of generating collision-free motion in an operator-assisted teleoperated robot arm manipulator system is discussed. The concentration is on several system requirements: a real real-time operation, a guarantee of collision-free motion for the entire body of the arm manipulator, and an ability to handle obstacles of arbitrary shapes. The suggested methodology draws on recent work on motion planning with incomplete information for whole-sensitive robots. >

Implementation of self-organizing neural networks for visuo-motor control of an industrial robot

Abstract: The implementation of two neural network algorithms for visuo-motor control of an industrial robot (Puma 562) is reported. The first algorithm uses a vector quantization technique, the 'neural-gas' network, together with an error correction scheme based on a Widrow-Hoff-type learning rule. The second algorithm employs an extended self-organizing feature map algorithm. Based on visual information provided by two cameras, the robot learns to position its end effector without an external teacher. Within only 3000 training steps, the robot-camera system is capable of reducing the positioning error of the robot's end effector to approximately 0.1% of the linear dimension of the work space. By employing adaptive feedback the robot succeeds in compensating not only slow calibration drifts, but also sudden changes in its geometry. Hardware aspects of the robot-camera system are discussed. >

Polly: a vision-based artificial agent

Abstract: In this paper I will describe Polly, a low cost visionbased robot that gives primitive tours. The system is very simple, robust and efficient, and runs on a hardware platform which could be duplicated for less than $10K US. The system was built to explore how knowledge about the structure the environment can be used in a principled way to simplify both visual and motor processing. I will argue that very simple and efficient visual mechanisms can often be used to solve real problems in real (unmodified) environments in a principled manner. I will give an overview of the robot, discuss the properties of its environment, show how they can be used to simplify the design of the system, and discuss what lessons can drawn for the design of other systems.

Genetics-based machine learning and behavior-based robotics: a new synthesis

Abstract: Intelligent robots should be able to use sensor information to learn how to behave in a changing environment. As environmental complexity grows, the learning task becomes more and more difficult. This problem is faced using an architecture based on learning classifier systems and on the structural properties of animal behavioral organization, as proposed by ethologists. After a description of the learning technique used and of the organizational structure proposed, experiments that show how behavior acquisition can be achieved are presented. The simulated robot learns to follow a light and to avoid hot dangerous objects. While these two simple behavioral patterns are independently learned, coordination is attained by means of a learning coordination mechanism. >

A controller design framework for telerobotic systems

Abstract: A framework for designing a telerobotic system controller is presented. This controller is designed so the dynamic behaviors of the master robot and the slave robot are functions of each other. These functions, which the designer chooses based upon the application, are described, and a control architecture is proposed to achieve these functions. To guarantee that the specified functions and proposed architecture govern the system behavior, H/sub infinity / control theory and model reduction techniques are used. Several experiments were conducted to verify the theoretical derivations. This control method is unique, because it does not require any transfer of either position or velocity information between the master robot and the slave robot; it only requires the transfer of forces. Although this property leads to a wider communication bandwidth between the master and slave robots, the entire system may still suffer from a positional error buildup between the master robot and slave robot. >

Robotic graphics: a new approach to force feedback for virtual reality

Abstract: A new conceptual solution is presented for the problem of providing force feedback for virtual reality, concentrating on potential CAD/CAM applications. The essential concept is that force feedback is provided by interactions between the human operator and specialized external (as opposed to worn) robots. This is called "robotic graphics" to express the analogy between robots simulating the feel of an object, and graphics displays simulating its appearance. This is illustrated by introducing the derivative concepts of "robotic shape displays" and "roboxels.". >

Applications of augmented reality for human-robot communication

Abstract: The director/agent (D/A) metaphor of telerobotic interaction is discussed as a potential means for achieving human-robot synergy. In order for the human operator to communicate spatial information to the robot during D/A operations, the medium of augmented reality through overlaid virtual stereographics is proposed, leading to what is referred to as virtual control. An overview is given of the ARGOS (Augmented Reality through Graphic Overlays on Stereovideo) system. In particular, the uses of overlaid virtual pointers for enhancing absolute depth judgement tasks, virtual tape measures for real-world quantification, virtual tethers for perceptual enhancement in manual teleoperation, virtual landmarks for enhancing depth scaling, and virtual object overlays for on-object edge enhancement and display superposition are all presented and discussed.

From Tom Thumb to the Dockers: some experiments with foraging robots

Abstract: In this paper, we experiment, from the point of view of their efficiency, different implementations of the "explorer robots application" Three types of "Tom Thumb robots", whose behavior is based on the foraging behaviors of ants are proposed and their results are critically examined We then introduce chain-making robots (the "dockers"), governed by local perceptions and interactions This helps us to show that only a few changes in the robots' behavior may greatly improve the efficiency of the population

A taxonomy for swarm robots

Abstract: In many cases several mobile robots (autonomous agents) can be used together to accomplish tasks that would be either more difficult or impossible for a robot acting alone. Many different models have been suggested for the makeup of such collections of robots. In this paper the authors present a taxonomy of the different ways in which such a collection of autonomous robotic agents can be structured. It is shown that certain swarms provide little or no advantage over having a single robot, while other swarms can obtain better than linear speedup over a single robot. There exist both trivial and non-trivial problems for which a swarm of robots can succeed where a single robot will fail. Swarms are more than just networks of independent processors - they are potentially reconfigurable networks of communicating agents capable of coordinated sensing and interaction with the environment.

Robot for guiding movements and control method thereof

Abstract: A robot for guiding movements has its power provided by an operator who handles a tool integral with the robot. Like a conventional robot, the guiding robot has several axes respectively associated with rotation sensors that are connected to a computer system memorizing a path to be followed. When the operator moves the tool beyond the stored path, blocking devices, controlled by the computer system and replacing the robot's motors, prevent the tool from continuing to depart from the path. Thus, at any time, the operator can move the tool within the stored path only. The blocking devices are passive, that is, they are such that they can only resist to a movement but cannot generate a movement, which prevents the occurrence of any uncontrolled movement.

Concurrent localisation and map building for mobile robots using ultrasonic sensors

Abstract: Successful autonomous navigation by a mobile robot depends on its ability to map its environment and to accurately determine its position within this environment. In complex environments, where no additional navigational aids are present, the localization and map-building processes are not independent of each other. This paper presents an approach where the boot-strapping problem of concurrent localization and map building is solved by estimating the respective errors introduced by each of the processes and correcting them accordingly. The algorithms were tested in simulation, and results showed that the robot stably navigated in its environment.