Showing papers on "Autonomous system (mathematics) published in 2008"
TL;DR: The main components and architecture of RAVEN are described and recent flight test results are presented illustrating the applications discussed above.
Abstract: To investigate and develop unmanned vehicle systems technologies for autonomous multiagent mission platforms, we are using an indoor multivehicle testbed called real-time indoor autonomous vehicle test environment (RAVEN) to study long-duration multivehicle missions in a controlled environment. Normally, demonstrations of multivehicle coordination and control technologies require that multiple human operators simultaneously manage flight hardware, navigation, control, and vehicle tasking. However, RAVEN simplifies all of these issues to allow researchers to focus, if desired, on the algorithms associated with high-level tasks. Alternatively, RAVEN provides a facility for testing low-level control algorithms on both fixed- and rotary-wing aerial platforms. RAVEN is also being used to analyze and implement techniques for embedding the fleet and vehicle health state (for instance, vehicle failures, refueling, and maintenance) into UAV mission planning. These characteristics facilitate the rapid prototyping of new vehicle configurations and algorithms without requiring a redesign of the vehicle hardware. This article describes the main components and architecture of RAVEN and presents recent flight test results illustrating the applications discussed above.
452 citations
TL;DR: In this paper, a voltage control strategy for an electronically-interfaced distribution generation (DG) unit that utilizes a voltage-sourced converter (VSC) as the interface medium is presented.
Abstract: This paper presents a new voltage control strategy for an electronically-interfaced distribution generation (DG) unit that utilizes a voltage-sourced converter (VSC) as the interface medium. The control strategy is based on the concept of voltage-controlled VSC (VC-VSC) rather than the conventional current-controlled VSC (CC-VSC). The proposed VC-VSC 1. enables operation of a DG unit in both grid-connected and islanded (autonomous) modes, 2. provides current-limit capability for the VSC during faults, 3. inherently provides an islanding detection method without non-detection zone, 4. provides smooth transition capability between grid-connected and autonomous modes, and 5. can accommodate ride-through capability requirements under a grid-connected mode. This paper also investigates performance of the proposed VC-VSC strategy based on an eigenanalysis in MATLAB, and time-domain simulations in the PSCAD/EMTDC environment.
343 citations
TL;DR: The areas of AI for autonomous ship collision avoidance are examined in this paper are evolutionary algorithms, fuzzy logic, expert systems, and neural networks, as well as a combination of them (hybrid system).
Abstract: This study provides both a spherical understanding about autonomous ship navigation for collision avoidance (CA) and a theoretical background of the reviewed work. Additionally, the human cognitive abilities and the collision avoidance regulations (COLREGs) for ship navigation are examined together with water based collision avoidance algorithms. The requirements for autonomous ship navigation are addressed in conjunction with the factors influencing ship collision avoidance. Humans are able to appreciate these factors and also perform ship navigation at a satisfactory level, but their critical decisions are highly subjective and can lead to error and potentially, to ship collision. The research for autonomous ship navigation may be grouped into the classical and soft computing based categories. Classical techniques are based on mathematical models and algorithms while soft-computing techniques are based on Artificial Intelligence (AI). The areas of AI for autonomous ship collision avoidance are examined in this paper are evolutionary algorithms, fuzzy logic, expert systems, and neural networks (NN), as well as a combination of them (hybrid system).
319 citations
24 Apr 2008
TL;DR: P predictive information in sensor space is considered as a measure for the behavioral complexity of a two-wheel embodied robot moving in a rectangular arena with several obstacles and can be generalized and may help to derive explicit learning rules from complexity theoretic measures.
Abstract: Measures of complexity are of immediate interest for the field of autonomous robots both as a means to classify the behavior and as an objective function for the autonomous development of robot behavior. In the present paper we consider predictive information in sensor space as a measure for the behavioral complexity of a two-wheel embodied robot moving in a rectangular arena with several obstacles. The mutual information (MI) between past and future sensor values is found empirically to have a maximum for a behavior which is both explorative and sensitive to the environment. This makes predictive information a prospective candidate as an objective function for the autonomous development of such behaviors. We derive theoretical expressions for the MI in order to obtain an explicit update rule for the gradient ascent dynamics. Interestingly, in the case of a linear or linearized model of the sensorimotor dynamics the structure of the learning rule derived depends only on the dynamical properties while the value of the MI influences only the learning rate. In this way the problem of the prohibitively large sampling times for information theoretic measures can be circumvented. This result can be generalized and may help to derive explicit learning rules from complexity theoretic measures.
189 citations
TL;DR: In this paper, an actuator and sensor FDI system for small autonomous helicopters is presented, which evaluates any significant change in the behaviour of the vehicle with respect to the fault-free behaviour, which is estimated by using observers.
165 citations
TL;DR: This paper reports on AnnieWAY, an autonomous vehicle that is capable of driving through urban scenarios and that successfully entered the finals of the 2007 DARPA Urban Challenge competition.
Abstract: This paper reports on AnnieWAY, an autonomous vehicle that is capable of driving through urban scenarios and that successfully entered the finals of the 2007 DARPA Urban Challenge competition. After describing the main challenges imposed and the major hardware components, we outline the underlying software structure and focus on selected algorithms. Environmental perception mainly relies on a recent laser scanner that delivers both range and reflectivity measurements. Whereas range measurements are used to provide three-dimensional scene geometry, measuring reflectivity allows for robust lane marker detection. Mission and maneuver planning is conducted using a hierarchical state machine that generates behavior in accordance with California traffic laws. We conclude with a report of the results achieved during the competition. © 2008 Wiley Periodicals, Inc.
157 citations
TL;DR: In this paper, the authors introduced a 3D quadratic autonomous system, which can generate two coexisting single-wing chaotic attractors and a pair of diagonal double-wing attractors.
Abstract: This paper introduces a new 3-D quadratic autonomous system, which can generate two coexisting single-wing chaotic attractors and a pair of diagonal double-wing chaotic attractors. More importantly, the system can generate a four-wing chaotic attractor with very complicated topological structures over a large range of parameters. Some basic dynamical behaviors and the compound structure of the new 3-D system are investigated. Detailed bifurcation analysis illustrates the evolution processes of the system among two coexisting sinks, two coexisting periodic orbits, two coexisting single-wing chaotic attractors, major and minor diagonal double-wing chaotic attractors, and a four-wing chaotic attractor. Poincare-map analysis shows that the system has extremely rich dynamics. The physical existence of the four-wing chaotic attractor is verified by an electronic circuit. Finally, spectral analysis shows that the system has an extremely broad frequency bandwidth, which is very desirable for engineering applications such as secure communications.
140 citations
TL;DR: This paper defines measures for the quality of spreading, presents a local algorithm for the one-dimensional spreading problem, proves its convergence to the equally spaced configuration and discusses its convergence rate in the synchronous and semi-synchronous settings.
111 citations
TL;DR: In this paper, a cycle time model for conceptualizing autonomous vehicle storage and retrieval systems and comparing their performance with crane-based automated storage-and retrieval systems is presented, based on an iterative computational scheme exploiting random storage assumptions and queuing model approximations.
Abstract: A computationally efficient cycle time model for conceptualizing autonomous vehicle storage and retrieval systems and comparing their performance with crane-based automated storage and retrieval systems is presented. The model is based on an iterative computational scheme exploiting random storage assumptions and queuing model approximations. Relative to earlier models, the procedure scales up efficiently for large problems thereby enabling more extensive search of a design solution space. Simulation based validation studies suggest that model accuracy is adequate for system conceptualization. The procedure is demonstrated using realistically sized sample problems.
95 citations
TL;DR: A probabilistic framework is presented for designing and analyzing existing CA algorithms proposed in literature, enabling on-line computation of the risk for faulty intervention and consequence of different actions.
95 citations
TL;DR: A new approach to enhance the performance of an active fault tolerant control system based on a modified recovery/trajectory control system in which a reconfigurable reference input is considered when performance degradation occurs in the system due to faults in actuator dynamics.
Abstract: The prospective work reported in this paper explores a new approach to enhance the performance of an active fault tolerant control system. The proposed technique is based on a modified recovery/trajectory control system in which a reconfigurable reference input is considered when performance degradation occurs in the system due to faults in actuator dynamics. An added value of this work is to reduce the energy spent to achieve the desired closed-loop performance. This work is justified by the need of maintaining a reliable system in a dynamical way in order to achieve a mission by an autonomous system, e.g., a launcher, a satellite, a submarine, etc. The effectiveness is illustrated using a three-tank system for slowly varying reference inputs corrupted by actuators faults.
TL;DR: The paper presents several impossibility theorems, limiting the inaccuracy levels that still allow convergence, and prohibiting a general algorithm for gathering, namely, meeting at a point, in a finite number of steps.
Abstract: A number of recent studies concern algorithms for distributed control and coordination in systems of autonomous mobile robots The common theoretical model adopted in these studies assumes that the positional input of the robots is obtained by perfectly accurate visual sensors, that robot movements are accurate, and that internal calculations performed by the robots on (real) coordinates are perfectly accurate as well The current paper concentrates on the effect of weakening this rather strong set of assumptions and replacing it with the more realistic assumption that the robot sensors, movement, and internal calculations may have slight inaccuracies Specifically, the paper concentrates on the ability of robot systems with inaccurate sensors, movements, and calculations to carry out the task of convergence The paper presents several impossibility theorems, limiting the inaccuracy levels that still allow convergence, and prohibiting a general algorithm for gathering, namely, meeting at a point, in a finite number of steps The main positive result is an algorithm for convergence under bounded measurement, movement, and calculation errors
TL;DR: Real-time path planning schemes employing limited information for fully autonomous unmanned air vehicles (UAVs) in a hostile environment and a class of dynamic threats so that the second algorithm can efficiently handle such dynamic threats while guaranteeing its convergence to a given target.
TL;DR: In this article, a new three-dimensional smooth quadratic autonomous chaotic system is presented, which can involve into periodic and chaotic orbits in case of different parameters, when proper parameters are chosen.
Abstract: This letter presents a new three-dimensional smooth quadratic autonomous chaotic system, which can involve into periodic and chaotic orbits in case of different parameters. When proper parameters are chosen, a single four-wing attractor and a single three-wing attractor are generated. The further analysis shows that the two separated attractors coexisted with different initial conditions. Basic properties of the new system were also analyzed by means of Lyapunov exponents, bifurcation diagrams and Poincare map.
TL;DR: An algorithm to design time efficient trajectories corresponding to piecewise constant thrust arcs with few actuator switchings with a direct method to compute the solutions numerically is developed.
TL;DR: A cycle-time model for class-based storage policies is proposed for automated unit load Storage and Retrieval systems that use autonomous vehicle technology to achieve sufficient accuracy and computational efficiency for system design conceptualisation applications.
Abstract: A cycle-time model for class-based storage policies is proposed for automated unit load Storage and Retrieval (S/R) systems that use autonomous vehicle technology. The model is based on a queuing network approach to achieve sufficient accuracy and computational efficiency for system design conceptualisation applications. It is illustrated through a series of realistic case problems.
TL;DR: The proposed approach to the problem of autonomous navigation of a car-like robot evolving in an urban environment lies in the design of perception and planning modules that consider explicitly the dynamic nature of the vehicle and the environment while enforcing the safety constraint.
Abstract: This paper addresses the problem of autonomous navigation of a car-like robot evolving in an urban environment. Such an environment exhibits an heterogeneous geometry and is cluttered with moving obstacles. Furthermore, in this context, motion safety is a critical issue. The proposed approach to the problem lies in the design of perception and planning modules that consider explicitly the dynamic nature of the vehicle and the environment while enforcing the safety constraint. The main contributions of this work are the development of such modules and integration into a single application. Initial full scale experiments validating the approach are presented.
TL;DR: A hybrid agent of behaviour architecture to deal with the autonomous navigation of a farming vehicle fitted with a set of sensors and actuators to acquire continuous location and environmental data to safely and appropriately interact with a dynamic environment is presented.
TL;DR: In this article, the problem of controlling an autonomous wheeled vehicle which must move in its operative space and reach a prescribed goal point avoiding the collision with the obstacles is dealt with.
Abstract: The problem of controlling an autonomous wheeled vehicle which must move in its operative space and reach a prescribed goal point avoiding the collision with the obstacles is dealt with. To comply with the non-holonomic nature of the system, a gradient-tracking approach is followed, so that a reference velocity and orientation are suitably generated during the vehicle motion. To track such references, two control laws are designed by suitably transforming the system model into a couple of auxiliary second-order uncertain systems, relying on which second-order sliding modes can be enforced. As a result, the control objective is attained by means of a continuous control law, so that the problems due to the so-called chattering effect, such as the possible actuators wear or the induction of vibrations, typically associated with the use of sliding-mode control, are circumvented.
Proceedings Article•
27 Jun 2008TL;DR: This study presents the componentization of the functional level of a robot, the synthesis of an execution controller as well as validation techniques for checking essential “safety” properties.
Abstract: Autonomous robots are complex systems that require the interaction/cooperation of numerous heterogeneous software components. Nowadays, robots are critical systems and must meet safety properties including in particular temporal and real-time constraints. We present a methodology for modeling and analyzing a robotic system using the BIP component framework integrated with an existing framework and architecture, the LAAS Architecture for Autonomous System, based on GenoM. The BIP componentization approach has been successfully used in other domains. In this study, we show how it can be seamlessly integrated in the preexisting methodology. We present the componentization of the functional level of a robot, the synthesis of an execution controller as well as validation techniques for checking essential “safety” properties.
01 Jan 2008
TL;DR: This study presents the componentization of the functional level of a robot, the synthesis of an execution controller as well as validation techniques for checking essential safety properties in the LAAS Architecture for Autonomous System and its tool GenoM.
Abstract: Autonomous robots are complex systems that require the interaction/cooperation of numerous heterogeneous software components. Nowadays, robots are getting closer to humans and as such are becoming critical systems which must meet safety properties including in particular logical, temporal and real-time constraints. We present an evolution of the LAAS Architecture for Autonomous System and its tool GenoM. This evolution is based on the BIP (Behaviors Interactions Priorities) component based design framework which has been successfully used in other domains (e.g. embedded systems). In this study, we show how we seamlessly integrate BIP in the preexisting methodology. We present the componentization of the functional level of a robot, the synthesis of an execution controller as well as validation techniques for checking essential safety properties. This approach has been integrated in the LAAS architecture and we have performed a number of experiment in simulation but also on a real robot (DALA).
TL;DR: An adaptive critic motion control design is presented, which enables WMR to autonomously generate the control ability by learning through trials, and shows that the DHP adaptive critic design is a useful base of autonomous control.
TL;DR: A hybrid path planning algorithm which is designed for use of autonomous vehicles in indoor environments and mainly contributes the ability of generating a safe and smooth collision avoidance path for attaining a desired position in an unknown and obstructed environment.
Abstract: Purpose – This paper aims to present a hybrid path planning algorithm which is designed for use of autonomous vehicles in indoor environments. The approach mainly contributes the ability of generating a safe and smooth collision avoidance path for attaining a desired position in an unknown and obstructed environment.Design/methodology/approach – The hybrid planner is based on potential field method and Voronoi diagram approach, and it is represented with the ability of concurrent map building and autonomous navigation.Findings – The possibility of controlling the look‐ahead distance allows the mobile robot to smartly control the velocity for creating a smooth trajectory autonomously. The dead‐lock problem is solved by defining necessary sub‐goals between targets on the constructed map.Originality/value – The system controller (look‐ahead control) with the potential field method allows the robot to generate a smooth and safe path for an expected position. Only essential exploration of unknown environment i...
TL;DR: In speed-matched conditions, autonomous mobility was associated with decreased manned vehicle mission time, faster operator reaction times to targets, greater instances of multitasking while under motion, and lower subjective operator workload measures than with manual driving.
Abstract: Autonomous mobility systems developed for unmanned ground vehicles may have additional benefits by enhancing system performance and reducing demands on operators for manned ground vehicles. This effort examines the potential impact of introducing autonomous mobility to control manned vehicles while operators performed secure mobility. Eleven Soldiers participated in an experimental task requiring concurrent control of a manned and an unmanned Stryker performing a road march, scanning of the local environment for targets, and planning of a reconnaissance route for a third simulated asset. The control of the manned vehicle was varied between autonomous and manual control and several speed and accuracy variables were examined for each task. Subjective measures of operator workload, stress, and motion sickness were also examined. The results support the potential benefits of incorporating autonomous mobility into manned platforms. In speed-matched conditions, autonomous mobility was associated with decreased manned vehicle mission time, faster operator reaction times to targets, greater instances of multitasking while under motion, and lower subjective operator workload measures than with manual driving. In conclusion, autonomous mobility technologies have the potential to free up resources from the vehicle operator and allow for better operator performance on tasks other than vehicle control.
14 Oct 2008
TL;DR: The experimental results prove that the developed system performed the autonomous operation smoothly and completed the mission.
Abstract: The authors have been conducting research on an autonomous system for loading operation by wheel loader. Experimental results at a field test site using full-size model (length: 6.1m) will be described in this paper. Basic structure of system consists of three sub systems: measuring and modeling of environment, task planning and motion control. The experimental operation includes four cycles of scooping and loading to dump truck. The experimental results prove that the developed system performed the autonomous operation smoothly and completed the mission.
TL;DR: The concept of Hybrid Parameter-Varying Model Predictive Control (HPV-MPC) is applied for autonomous vehicle steering and a comparison between controllers using prediction models varying from the full nonlinear model, as an indication for the maximal achievable performance, to a linear model was performed.
TL;DR: A novel application of constraint satisfaction in the design of a camera system that addresses the unique and difficult challenges of IDE is described, demonstrating a specialized constraint solver that exploits the spatial structure of the problem, enabling the real-time use of the camera system.
Abstract: Camera control techniques for interactive digital entertainment (IDE) are reaching their limits in terms of capabilities. To enable future growth, new methods must be derived to address these new challenges. Existing academic research into camera control is typically devoted to cinematography and guided exploration tasks, and is not directly applicable to IDE. This paper describes a novel application of constraint satisfaction in the design of a camera system that addresses the unique and difficult challenges of IDE. It demonstrates a specialized constraint solver that exploits the spatial structure of the problem, enabling the real-time use of the camera system. The merit of our solution is highlighted by demonstrating the computational efficiency and ability to extend the cameras capabilities in a simple and effective manner.
TL;DR: A GVD-derived topology of spatial affordances is described, in which junctions are defined by the physical capabilities of the navigating robot, and this topology follows walls in open spaces to ensure robust edge transition so that all features can be modeled egocentcally.
Abstract: This article presents our attempts to direct an autonomous robot using efficient and universal topological instructions, which can be incrementally interpreted by a moving robot that does not have its own map initially. Many real-world experiments are included, featuring autonomous exploration and mapping. Surprisingly, we conclude and show that for this type of navigation, abilities in object recognition are more important than better mapping. The article describes a GVD-derived topology of spatial affordances, in which junctions are defined by the physical capabilities of the navigating robot. Similar to the extended GVD, our topology follows walls in open spaces to ensure robust edge transition so that all features can be modeled egocentcally. The specified wall-following distance is calculated to maximize the stability of the egocentrically modeled topology even when obstacle detection is intermittent.
TL;DR: In this paper, an autonomous tracking control system and a control structure to combine autonomous and teleoperation commands in a bicycle-type mobile robot is proposed, which is proved to be stable in the sense that it asymptotically reaches the tracking objective.
TL;DR: In this article, a novel on-line trajectory generation method for autonomous lane changing is presented, which is guidance based, real-time applicable, and ensures safety and passenger ride comfort.
Abstract: In the context of intelligent transportation, this paper presents a novel on-line trajectorygeneration method for autonomous lane changing. The proposed scheme is guidance based, realtime applicable, and ensures safety and passenger ride comfort. Based on the principles of Rendezvous Guidance, the passing vehicle is guided in real-time to match the position and velocity of a shadow target (i.e., rendezvous with) during the overtaking manoeuvre. The shadow target’s position and velocity are generated based on real-time sensory information gathered about the slower vehicle ahead of the passing vehicle as well as other vehicles which may be travelling in the passing lane. Namely, the guidance principle is also used to prevent any potential collision with these obstacle vehicles. The proposed method can be used as a fully autonomous system or simply as a driver-assistance tool. Extensive simulations and experiments, some of which are presented herein, clearly demonstrate the tangible efficiency of the proposed method.