Showing papers in "The International Journal of Robotics Research in 2004"
TL;DR: A domain-independent taxonomy of MRTA problems is given, and it is shown how many such problems can be viewed as instances of other, well-studied, optimization problems.
Abstract: Despite more than a decade of experimental work in multi-robot systems, important theoretical aspects of multi-robot coordination mechanisms have, to date, been largely untreated. To address this issue, we focus on the problem of multi-robot task allocation (MRTA). Most work on MRTA has been ad hoc and empirical, with many coordination architectures having been proposed and validated in a proof-of-concept fashion, but infrequently analyzed. With the goal of bringing objective grounding to this important area of research, we present a formal study of MRTA problems. A domain-independent taxonomy of MRTA problems is given, and it is shown how many such problems can be viewed as instances of other, well-studied, optimization problems. We demonstrate how relevant theory from operations research and combinatorial optimization can be used for analysis and greater understanding of existing approaches to task allocation, and show how the same theory can be used in the synthesis of new approaches.
1,369 citations
TL;DR: It is shown that when represented in the information form, map posteriors are dominated by a small number of links that tie together nearby features in the map, which is developed into a sparse variant of the EIF, called the sparse extended information filter (SEIF).
Abstract: In this paper we describe a scalable algorithm for the simultaneous mapping and localization (SLAM) problem. SLAM is the problem of acquiring a map of a static environment with a mobile robot. The vast majority of SLAM algorithms are based on the extended Kalman filter (EKF). In this paper we advocate an algorithm that relies on the dual of the EKF, the extended information filter (EIF). We show that when represented in the information form, map posteriors are dominated by a small number of links that tie together nearby features in the map. This insight is developed into a sparse variant of the EIF, called the sparse extended information filter (SEIF). SEIFs represent maps by graphical networks of features that are locally interconnected, where links represent relative information between pairs of nearby features, as well as information about the robot’s pose relative to the map. We show that all essential update equations in SEIFs can be executed in constant time, irrespective of the size of the map. We...
716 citations
TL;DR: This design methodology aims to create a virtual tool which accounts for the implicit limitations imposed by the delay, and uses wave variables for the analysis and implementation, and builds a system with consistent and predictable behavior.
Abstract: In this paper we survey the development of the wave variable concept and examine wave-based teleoperation. We study the behavior of force reflecting systems under unknown but constant transmission delays, ranging from periods less than the human reaction time to several seconds. Passive transmission procedures guarantee system stability, but wave reflections and spurious dynamics may interfere with normal operation. Using wave variables for the analysis and implementation, and making appropriate design choices, a system with consistent and predictable behavior is constructed. This design methodology aims to create a virtual tool which accounts for the implicit limitations imposed by the delay. These developments also form the basis for extensions to wave-based prediction and application to variable delays, such as those inherent to Internet-based telemanipulation.
547 citations
TL;DR: By drastically reducing the effective impedance of the manipulator while maintaining high-frequency torque capability, it is shown that the competing design requirements of performance and safety can be successfully integrated into a single manipulation system.
Abstract: In recent years, many successful robotic manipulator designs have been introduced. However, there remains the challenge of designing a manipulator that possesses the inherent safety characteristics...
466 citations
TL;DR: A mathematical model based on hidden Markov models is proposed in order to integrate four abilities: (1) symbol emergence; (2) behavior recognition; (3) self-behavior generation; (4) acquiring the motion primitives.
Abstract: “Mimesis” theory focused in the cognitive science field and “mirror neurons” found in the biology field show that the behavior generation process is not independent of the behavior cognition process. The generation and cognition processes have a close relationship with each other. During the behavioral imitation period, a human being does not practice simple joint coordinate transformation, but will acknowledge the parents’ behavior. It understands the behavior after abstraction as symbols, and will generate its self-behavior. Focusing on these facts, we propose a new method which carries out the behavior cognition and behavior generation processes at the same time. We also propose a mathematical model based on hidden Markov models in order to integrate four abilities: (1) symbol emergence; (2) behavior recognition; (3) self-behavior generation; (4) acquiring the motion primitives. Finally, the feasibility of this method is shown through several experiments on a humanoid robot.
350 citations
TL;DR: Atlas is described, a hybrid metrical/topological approach to simultaneous localization and mapping (SLAM) that achieves efficient mapping of large-scale environments through an efficient map-matching algorithm coupled with a cycle verification step.
Abstract: In this paper we describe Atlas, a hybrid metrical/topological approach to simultaneous localization and mapping (SLAM) that achieves efficient mapping of large-scale environments. The representation is a graph of coordinate frames, with each vertex in the graph representing a local frame and each edge representing the transformation between adjacent frames. In each frame, we build a map that captures the local environment and the current robot pose along with the uncertainties of each. Each map’s uncertainties are modeled with respect to its own frame. Probabilities of entities with respect to arbitrary frames are generated by following a path formed by the edges between adjacent frames, computed using either the Dijkstra shortest path algorithm or breath-first search. Loop closing is achieved via an efficient map-matching algorithm coupled with a cycle verification step. We demonstrate the performance of the technique for post-processing large data sets, including an indoor structured environment (2.2 k...
329 citations
TL;DR: An efficient algorithm based on interval analysis that allows us to solve the forward kinematics, i.e., to determine all the possible poses of the platform for given joint coordinates, which is competitive in term of computation time with a real-time algorithm such as the Newton scheme, while being safer.
Abstract: We consider in this paper a Gough-type parallel robot and we present an efficient algorithm based on interval analysis that allows us to solve the forward kinematics, i.e., to determine all the possible poses of the platform for given joint coordinates. This algorithm is numerically robust as numerical round-off errors are taken into account; the provided solutions are either exact in the sense that it will be possible to refine them up to an arbitrary accuracy or they are flagged only as a “possible” solution as either the numerical accuracy of the computation does not allow us to guarantee them or the robot is in a singular configuration. It allows us to take into account physical and technological constraints on the robot (for example, limited motion of the passive joints). Another advantage is that, assuming realistic constraints on the velocity of the robot, it is competitive in term of computation time with a real-time algorithm such as the Newton scheme, while being safer.
314 citations
TL;DR: A general manipulation planning approach capable of addressing continuous sets for modeling both the possible grasps and the stable placements of the movable object, rather than discrete sets generally assumed by the previous approaches.
Abstract: This paper deals with motion planning for robots manipulating movable objects among obstacles. We propose a general manipulation planning approach capable of addressing continuous sets for modeling both the possible grasps and the stable placements of the movable object, rather than discrete sets generally assumed by the previous approaches. The proposed algorithm relies on a topological property that characterizes the existence of solutions in the subspace of configurations where the robot grasps the object placed at a stable position. It allows us to devise a manipulation planner that captures in a probabilistic roadmap the connectivity of sub-dimensional manifolds of the composite configuration space. Experiments conducted with the planner in simulated environments demonstrate its efficacy to solve complex manipulation problems.
309 citations
TL;DR: Results show that models can deliver both qualitatively and quantitatively correct predictions in time lapses that are at least four orders of magnitude smaller than those required by embodied simulations and that they represent a useful tool for generalizing the dynamics of these highly stochastic, asynchronous, nonlinear systems.
Abstract: In this paper, we present a time-discrete, incremental methodology for modeling, at the microscopic and macroscopic level, the dynamics of distributed manipulation experiments using swarms of autonomous robots endowed with reactive controllers. The methodology is well-suited for nonspatial metrics since it does not take into account robots’ trajectories or the spatial distribution of objects in the environment. The strength of the methodology lies in the fact that it has been generated by considering incremental abstraction steps, from real robots to macroscopic models, each with well-defined mappings between successive implementation levels. Precise heuristic criteria based on geometrical considerations and systematic tests with one or two real robots prevent the introduction of free parameters in the calibration procedure of models. As a consequence, we are able to generate highly abstracted macroscopic models that can capture the dynamics of a swarm of robots at the behavioral level while still being closely anchored to the characteristics of the physical set-up. Although this methodology has been and can be applied to other experiments in distributed manipulation (e.g., object aggregation and segregation, foraging), in this paper we focus on a strictly collaborative case study concerned with pulling sticks out of the ground, an action that requires the collaboration of two robots to be successful. Experiments were carried out with teams consisting of two to 600 individuals at different levels of implementation (real robots, embodied simulations, microscopic and macroscopic models). Results show that models can deliver both qualitatively and quantitatively correct predictions in time lapses that are at least four orders of magnitude smaller than those required by embodied simulations and that they represent a useful tool for generalizing the dynamics of these highly stochastic, asynchronous, nonlinear systems, often outperforming intuitive reasoning. Finally, in addition to discussing subtle numerical effects, small prediction discrepancies, and difficulties in generating the mapping between different abstractions levels, we conclude the paper by reviewing the intrinsic limitations of the current modeling methodology and by proposing a few suggestions for future work.
283 citations
TL;DR: OpenHRP is expected to initiate the exploration of humanoid robotics on an open architecture software and hardware, thanks to the unification of the controllers and the examined consistency between the simulator and a real humanoid robot.
Abstract: This paper introduces an open architecture humanoid robotics platform (OpenHRP for short) on which various building blocks of humanoid robotics can be investigated. OpenHRP is a virtual humanoid robot platform with a compatible humanoid robot, and consists of a simulator of humanoid robots and motion control library for them which can also be applied to a compatible humanoid robot as it is. OpenHRP also has a view simulator of humanoid robots on which humanoid robot vision can be studied. The consistency between the simulator and the robot are enhanced by introducing a new algorithm to simulate repulsive force and torque between contacting objects. OpenHRP is expected to initiate the exploration of humanoid robotics on an open architecture software and hardware, thanks to the unification of the controllers and the examined consistency between the simulator and a real humanoid robot.
258 citations
TL;DR: This paper presents two algorithms for estimating sensor motion from image and inertial measurements, and presents a batch method, which produces estimates of the sensor motion, scene structure, and other unknowns using measurements from the entire observation sequence simultaneously.
Abstract: Robust motion estimation from image measurements would be an enabling technology for Mars rover, micro air vehicle, and search and rescue robot navigation; modeling complex environments from video; and other applications. While algorithms exist for estimating six degree of freedom motion from image measurements, motion from image measurements suffers from inherent problems. These include sensitivity to incorrect or insufficient image feature tracking; sensitivity to camera modeling and calibration errors; and long-term drift in scenarios with missing observations, i.e., where image features enter and leave the field of view.
The integration of image and inertial measurements is an attractive solution to some of these problems. Among other advantages, adding inertial measurements to image-based motion estimation can reduce the sensitivity to incorrect image feature tracking and camera modeling errors. On the other hand, image measurements can be exploited to reduce the drift that results from integrating noisy inertial measurements, and allows the additional unknowns needed to interpret inertial measurements, such as the gravity direction and magnitude, to be estimated.
This work has developed both batch and recursive algorithms for estimating camera motion, sparse scene structure, and other unknowns from image, gyro, and accelerometer measurements. A large suite of experiments uses these algorithms to investigate the accuracy, convergence, and sensitivity of motion from image and inertial measurements. Among other results, these experiments show that the correct sensor motion can be recovered even in some cases where estimates from image or inertial estimates alone are grossly wrong, and explore the relative advantages of image and inertial measurements and of omnidirectional images for motion estimation.
To eliminate gross errors and reduce drift in motion estimates from real image sequences, this work has also developed a new robust image feature tracker that exploits the rigid scene assumption and eliminates the heuristics required by previous trackers for handling large motions, detecting mistracking, and extracting features. A proof of concept system is also presented that exploits this tracker to estimate six degree of freedom motion from long image sequences, and limits drift in the estimates by recognizing previously visited locations.
TL;DR: Experimental results are presented that showpolygonal mobile robots controlled using visual feedback, transporting a convex polygonal object in an obstacle free environment toward a prescribed goal.
Abstract: In this paper we address the problem of transporting objects with multiple mobile robots using the concept of “object closure”. In contrast to other manipulation techniques that are typically derived from form or force closure constraints, object closure requires the less stringent condition that the object be trapped or caged by the robots. Our basic goal in this paper is to develop decentralized control policies for a group of robots to move toward a goal position while maintaining a condition of object closure. We present experimental results that show polygonal mobile robots controlled using visual feedback, transporting a convex polygonal object in an obstacle free environment toward a prescribed goal.
TL;DR: This paper addresses the control of the wheel-legged robot Hylos traveling on irregular sloping terrain with an algorithm to control the robot posture, based on a velocity model, validated through simulations and experiments that show the capabilities of such a redundantly actuated vehicle to enhance its own safety and autonomy in critical environments.
Abstract: Actively articulated locomotion systems such as hybrid wheel-legged vehicles are a possible way to enhance the locomotion performance of an autonomous mobile robot. In this paper, we address the control of the wheel-legged robot Hylos traveling on irregular sloping terrain. The redundancy of such a system is used to optimize both the balance of traction forces and the tipover stability. The general formulation of this optimization problem is presented, and a suboptimal but computationally efficient solution is proposed. Then, an algorithm to control the robot posture, based on a velocity model, is described. Finally, this algorithm is validated through simulations and experiments that show the capabilities of such a redundantly actuated vehicle to enhance its own safety and autonomy in critical environments.
TL;DR: A rough-terrain control methodology is presented that exploits the actuator redundancy found in multiwheeled mobile robot systems to improve ground traction and reduce power consumption.
Abstract: Mobile robots are being developed for high-risk missions in rough terrain situations, such as planetary exploration. Here, a rough-terrain control methodology is presented that exploits the actuator redundancy found in multiwheeled mobile robot systems to improve ground traction and reduce power consumption. The algorithm optimizes individual wheel torque based on multiple optimization criteria, which are a function of the local terrain profile. A key element of the method is to be able to include estimates of wheel-terrain contact angles and soil characteristics. A method using an extended Kalman filter is presented for estimating these angles using simple on-board sensors. Simulation and experimental results for a micro-rover traversing challenging terrain demonstrate the effectiveness of the algorithm.
TL;DR: The ability to regulate the average walking rate of the biped to a continuum of values by modification of within-stride and stride-boundary characteristics, such as step length is developed.
Abstract: In this paper we present the experimental validation of a framework for the systematic design, analysis, and performance enhancement of controllers that induce stable walking in N -link underactuated planar biped robots. Controllers designed via this framework act by enforcing virtual constraints—holonomic constraints imposed via feedback—on the robot’s configuration, which create an attracting two-dimensional invariant set in the full walking model’s state space. Stability properties of resulting walking motions are easily analyzed in terms of a two-dimensional subdynamic of the full walking model. A practical introduction to and interpretation of the framework is given. In addition, in this paper we develop the ability to regulate the average walking rate of the biped to a continuum of values by modification of within-stride and stride-boundary characteristics, such as step length.
TL;DR: Experimental results show that positioning in the three-dimensional space with a centimeter accuracy can be achieved, thus allowing the possibility to build high-resolution digital elevation maps, and work on terrain mapping with lowaltitude stereovision.
Abstract: In this paper we provide a progress report of the LAAS-CNRS project of autonomous blimp robot development, in the context of field robotics. Hardware developments aimed at designing a generic and versatile experimental platform are first presented. On this base, the flight control and terrain mapping issues, which constitute the main thrust of the research work, are presented in two parts. The first part, devoted to the automatic control study, is based on a rigorous modeling of the airship dynamics. Considering the decoupling of the lateral and longitudinal dynamics, several flight phases are identified for which appropriate control strategies are proposed. The description focuses on the lateral steady navigation. In the second part of the paper, we present work on terrain mapping with lowaltitude stereovision. A simultaneous localization and map building approach based on an extended Kalman filter is depicted, with details on the identification of the various errors involved in the process. Experimental...
TL;DR: This paper introduces a generic model for lattice-based self-reconfigurable robots and presents several generic locomotion algorithms that use this model, inspired by cellular automata.
Abstract: Previous work on self-reconfiguring modular robots has concentrated primarily on designing hardware and developing reconfiguration algorithms tied to specific hardware systems. In this paper, we introduce a generic model for lattice-based self-reconfigurable robots and present several generic locomotion algorithms that use this model. The algorithms presented here are inspired by cellular automata, using geometric rules to control module actions. The actuation model used is a general one, assuming only that modules can generally move over the surface of a group of modules. These algorithms can then be instantiated onto a variety of particular systems. Correctness proofs of many of the rule sets are also given for the generic geometry; this analysis can carry over to the instantiated algorithms to provide different systems with correct locomotion algorithms. We also present techniques for automated analysis that can be used for algorithms that are too complex to be easily analyzed by hand.
TL;DR: An application of insect visuomotor behavior to automatic control of landing is explored and the current efforts at exploring the applicability of this and related techniques to the guidance of uninhabited airborne vehicles (UAVs) are outlined.
Abstract: An application of insect visuomotor behavior to automatic control of landing is explored. Insects, being perhaps more reliant on image motion cites than mammals or higher vertebrates, are proving to be an excellent organism in which to investigate how information on optic flow is exploited to guide locomotion and navigation. We have observed how bees perform grazing landings on a flat surface and have deduced the algorithmic basis for the behavior. A smooth landing is achieved by a surprisingly simple and elegant strategy: image velocity is held constant as the surface is approached, thus automatically ensuring that flight speed is close to zero at touchdown. No explicit knowledge of flight speed or height above the ground is necessary. The feasibility, of this landing strategy was tested by implementation in a robotic gantry. We also outline our current efforts at exploring the applicability of this and related techniques to the guidance of uninhabited airborne vehicles (UAVs). Aspects of the algorithm were tested on a small UAV using real imagery, to control descent rate.
TL;DR: The key idea is to geometrically construct families of grasps around a single example such that allGrasps within a family meet user-specified design goals, and it is shown that the construction technique can be used to form force-closure grAsps, partial force- closure graspts, and gr asps above a quality threshold.
Abstract: One goal of grasp selection for robotics is to choose contact points that guarantee properties such as force- or form-closure. Many efficient algorithms have been developed to address this problem, but most of these algorithms focus on grasps having a minimal number of contact points. Increasing the number of contacts can dramatically improve the quality and flexibility of grasps that are constructed. However, computation time becomes a problem, as grasp synthesis algorithms that can be generalized to an arbitrary number of contacts typically require time exponential in the number of contacts. This paper presents an efficient algorithm for synthesis of manycontact grasps. The key idea is to geometrically construct families of grasps around a single example such that all grasps within a family meet user-specified design goals. We show that our construction technique can be used to form force-closure grasps, partial forceclosure grasps, and grasps above a quality threshold. Our approach requires time polynomial in the number of contacts, making it feasible to handle grasps with relatively large numbers of contacts. Results are shown for three-dimensional grasps with friction having five to twelve contacts and specialized for a variety of tasks. We have used this approach to design grasps for a robot hand and quasi-static manipulation plans for a humanoid robot. KEY WORDS—grasping, grasp synthesis, example-based grasping, enveloping grasps, grasp quality, contact regions
TL;DR: A method based on Hamilton’s canonical equations to solve both the inverse and direct problems of dynamics for parallel robots, shown to be computationally more efficient than the more common acceleration-based methods.
Abstract: Parallel manipulators offer much higher rigidity and smaller mobile mass than their serial counterparts, thus allowing much faster and more precise manipulations. The main disadvantage of parallel robots is their small workspace in comparison to serial arms of similar size. Furthermore, the manipulability of parallel robots is often poor in some regions of the (already small) workspace. Another problematic issue is effective modeling of parallel robot dynamics, often needed for control algorithms. Dynamic algorithms developed for serial robots or general closed-loop mechanisms cannot be easily applied to parallel robots when the objective is real-time, dynamicmodelbased control. Therefore, in this work we investigate how to design parallel manipulators so that their workspace size and manipulability are maximized, and how to model parallel robot dynamics effectively. We develop a new performance index that combines measures of manipulability and workspace size, and a kinematic optimization process yieldin...
TL;DR: This paper extends differential geometry to describe linear object deformation including flexure, torsion, and extension and proposes a disturbance force margin to indicate the stability of the grasping and the computation of the margin using the proposed approach.
Abstract: We describe the modeling of linear object deformation based on differential geometry and its applications to manipulative operations. A particle-based approach, the finite element method, and the Cosserat theory have been applied to the modeling of linear object deformation. In this paper, we establish an alternative modeling approach based on an extension of differential geometry. First, we extend differential geometry to describe linear object deformation including flexure, torsion, and extension. Secondly, we show computational results to demonstrate the feasibility of the proposed modeling technique, and we compare computational and experimental results to demonstrate the accuracy of the model. Next, we apply the proposed approach to the grasping of a deformable linear object. We propose a disturbance force margin to indicate the stability of the grasping and we describe the computation of the margin using the proposed approach. Finally, we apply the proposed approach to the deformation path planning ...
TL;DR: The system design of a machine that is constructed to study a quadrupedal gallop gait and two intelligent strategies have been developed for verification on a one-legged system, successful in operating one leg at speeds necessary for a dynamic gallop of amachine of this scale.
Abstract: In this paper we present the system design of a machine that we have constructed to study a quadrupedal gallop gait. The gallop gait is the preferred high-speed gait of most cursorial quadrupeds. To gallop, an animal must generate ballistic trajectories with characteristic strong impacts, coordinate leg movements with asymmetric footfall phasing, and effectively use compliant members, all the while maintaining dynamic stability. In this paper we seek to further understand the primary biological features necessary for galloping by building and testing a robotic quadruped similar in size to a large goat or antelope. These features include high-speed actuation, energy storage, on-line learning control, and high-performance attitude sensing. Because body dynamics are primarily influenced by the impulses delivered by the legs, the successful design and control of single leg energetics is a major focus of this work. The leg stores energy during flight by adding tension to a spring acting across an articulated k...
TL;DR: A novel pointing parallel mechanism with fully decoupled degrees of freedom, which may be suitable for applications that require aiming bodies such as tools, telescopes, antennas, cameras, solar panels, human or humanoid artificial limbs.
Abstract: In this paper we present a novel pointing parallel mechanism with fully decoupled degrees of freedom. The mechanism consists of two interconnected slider-crank linkages, each one of which independe...
TL;DR: A new method for the type synthesis of non-overconstrained (isostatic) spherical parallel manipulators is proposed, including one obtained by the combination of a 3-RRR sphericalallel manipulator and three Bennett linkages.
Abstract: A spherical parallel manipulator (also called an orientational parallel manipulator or rotational parallel manipulator) refers to a threedegreeof-freedom (3-DoF) parallel manipulator in which the moving platform undergoes a 3-DoF spherical motion or rotates about a fixed point. In this paper, we propose a new method for the type synthesis of non-overconstrained (isostatic) spherical parallel manipulators. In a non-overconstrained three-legged spherical parallel manipulator, each leg is composed of five revolute, prismatic and/or helical joints. Using the proposed approach, non-overconstrained three-legged spherical parallel manipulators can be obtained by the combination of a 3-RRR overconstrained spherical parallel manipulator and three four-bar Delassus linkages with at least one revolute joint. In a 3-RRR spherical parallel manipulator, each leg is composed of three revolute joints whose axes pass through the center of spherical motion. A four-bar Delassus linkage is a single-DoF four-bar linkage compo...
TL;DR: A biomechanical study to evaluate the efficiency of the motion of endoscopic robots in the colon, with a special focus on “inchworm” locomotion, and provided the guidelines to design a high-stroke pneumatic robotic prototype for colonoscopy.
Abstract: This paper concerns a biomechanical study to determine the efficiency of the motion of endoscopic robots in the colon. A quasi-linear viscoelastic model for soft tissues has been introduced to determine the mechanical behavior of colon and mesenteries. A study of efficiency of the phases of the motion, through biomechanical and geometrical factors, allowed to calculate the critical stroke to perform motion inside intestinal walls. This study has provided the guidelines to design a high-stroke pneumatic prototype for colonoscopy. In-vivo tests have been performed and have shown high efficiency of the robot in navigating inside pig’s intestine: the performances of the semiautonomous robot have achieved those of a traditional colonoscope in terms of travelled length.
TL;DR: In this paper, a new paradigm called "snakes and strings" is proposed for developing practical mobile robot systems that may be useful in such situations, which can skillfully move among the debris of the collapsed buildings.
Abstract: The International Rescue System Institute has been established in Japan to promote research and development of key technologies for the realization of practical search-and-rescue robots, anticipating future large-scale earthquakes and other catastrophic disasters. In this paper we propose a new paradigm called “snakes and strings”, for developing practical mobile robot systems that may be useful in such situations. “Snakes” stands for snake-like robots, which can skillfully move among the debris of the collapsed buildings. “Strings”, on the other hand, means robotic systems using strings or tethers, such as proposed in the “hyper-tether” research. Tethers can continuously supply energy, accomplish reliable communication links, and also exhibit high traction force. In this paper we present many new mechanical implementations of snake-like robots developed in our laboratory, and we also explain in detail the new paradigm.
TL;DR: A complete algorithm is presented that enables the limited pursuer to clear the same environments that a pursuer with a complete map, perfect localization, and perfect control can clear (under certain general position assumptions).
Abstract: We address an on-line version of the visibility-based pursuit-evasion problem. We take a minimalist approach in modeling the capabilities of a pursuer robot. A point pursuer moves in an unknown, simplyconnected, piecewise-smooth planar environment, and is given the task of locating any unpredictable, moving evaders that have unbounded speed. The evaders are assumed to be points that move continuously. To solve the problem, the pursuer must for each target have an unobstructed view of it at some time during execution. The pursuer is equipped with a range sensor that measures the direction of depth discontinuities, but cannot provide precise depth measurements. All pursuer control is specified either in terms of this sensor or wall-following movements. The pursuer does not have localization capability or perfect control. We present a complete algorithm that enables the limited pursuer to clear the same environments that a pursuer with a complete map, perfect localization, and perfect control can clear (unde...
TL;DR: This paper addresses an interval analysis based study that is applied to the design and the comparison of three-degrees-of-freedom (3-DoF) parallel kinematic machines and two 3- doF translational parallel mechanisms designed for machining applications are compared using this method.
Abstract: This paper addresses an interval analysis based study that is applied to the design and the comparison of 3-DOF parallel kinematic machines. Two design criteria are used, (i) a regular workspace shape and, (ii) a kinetostatic performance index that needs to be as homogeneous as possible throughout the workspace. The interval analysis based method takes these two criteria into account: on the basis of prescribed kinetostatic performances, the workspace is analysed to find out the largest regular dextrous workspace enclosed in the Cartesian workspace. An algorithm describing this method is introduced. Two 3-DOF translational parallel mechanisms designed for machining applications are compared using this method. The first machine features three fixed linear joints which are mounted orthogonally and the second one features three linear joints which are mounted in parallel. In both cases, the mobile platform moves in the Cartesian x y z space with fixed orientation.
TL;DR: The general solution of linearized propagation dynamics of both systematic and random errors for vehicle odometry is developed and validated and the associated integral transforms are applied to the task of eliciting the major dynamic behaviors of errors for several forms of odometry.
Abstract: The related fields of mobile robotics and ground vehicle localization lack a linearized theory of odometry error propagation. By contrast, the equivalent Schuler dynamics which apply to inertial guidance have been known and exploited for decades. In this paper, the general solution of linearized propagation dynamics of both systematic and random errors for vehicle odometry is developed and validated. The associated integral transforms are applied to the task of eliciting the major dynamic behaviors of errors for several forms of odometry. Interesting behaviors include path independence, response to symmetric inputs, zeros, extrema, monotonicity and conservation. Applications to systems theory, systems design, and calibration are illustrated. KEY WORDS—AUTHOR: PLEASE PROVIDE
TL;DR: An adaptation scheme based on measurements of ground contact timing obtained from binary sensors on the robot’s feet for adjusting the stride period in a hexapedal running robot is described.
Abstract: We demonstrate an adaptation strategy for adjusting the stride period in a hexapedal running robot. The robot is inspired by discoveries about the self-stabilizing properties of insects and uses a sprawled posture, a bouncing alternating-tripod gait, and passive compliance and damping in the limbs to achieve fast (over four body-lengths per second), stable locomotion. The robot is controlled by an open-loop motor pattern that activates the legs at fixed intervals. For maximum speed and efficiency, the stride period of the pattern should be adjusted to match changes in terrain (e.g., slopes) or loading conditions (e.g., carrying an object). An ideal adaptation strategy will complement the design philosophy behind the robot and take advantage of the self-stabilizing role of the mechanical system. In this paper we describe an adaptation scheme based on measurements of ground contact timing obtained from binary sensors on the robot’s feet. Wediscuss the motivation for the approach, putting it in the context o...