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Showing papers on "Autonomous system (mathematics) published in 2004"


Journal ArticleDOI
TL;DR: A new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display two 1-scroll chaotic attractors simultaneously, with only three equilibria, is introduced, of particular interest is the fact that this chaotic system can generate a complex 4- scroll chaotic attractor or confine two attractors to a 2-scroll Chaos attractor under the control of a simple constant input.
Abstract: This article introduces a new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display (i) two 1-scroll chaotic attractors simultaneously, with only three equilibria, and (ii) two 2-scroll chaotic attractors simultaneously, with five equilibria. Several issues such as some basic dynamical behaviors, routes to chaos, bifurcations, periodic windows, and the compound structure of the new chaotic system are then investigated, either analytically or numerically. Of particular interest is the fact that this chaotic system can generate a complex 4-scroll chaotic attractor or confine two attractors to a 2-scroll chaotic attractor under the control of a simple constant input. Furthermore, the concept of generalized Lorenz system is extended to a new class of generalized Lorenz-like systems in a canonical form. Finally, the important problems of classification and normal form of three-dimensional quadratic autonomous chaotic systems are formulated and discussed.

286 citations


Proceedings ArticleDOI
17 Jun 2004
TL;DR: In this paper, the authors address the issue of autonomous control and safe navigation in an unmanned marine vehicle (UMLV) and examine known legal issues regarding autonomous marine vehicles, and how to provide an autonomous COLREGS capability in an autonomous marine vehicle.
Abstract: This paper addresses the issue of autonomous control and safe navigation in an unmanned marine vehicle. Primarily it is concerned with the issue of effective collision avoidance. The first part of the paper examines known legal issues regarding autonomous marine vehicles, and the second part addresses how to provide an autonomous COLREGS capability in an autonomous marine vehicle.

76 citations


Journal ArticleDOI
TL;DR: In this article, an integrated study is conducted based on long term solar potential experimental measurements in order to determine the optimum configuration of a stand-alone photovoltaic system at representative locations all over Greece.

72 citations


Proceedings ArticleDOI
14 Jun 2004
TL;DR: In this article, the authors used a 4-wheel drive and a roll cage to protect the vehicle components from damage in case of a collision during the DARPA Grand Challenge 2016.
Abstract: The DARPA Grand Challenge (DGC) was an opportunity to test autonomous vehicles in a competitive situation. In addition to intelligent behaviour, the participating vehicles must also exhibit ruggedness and endurance in order to survive the fast ride over rough terrain ("win with the software- lose with the hardware"). The SciAutonics teams decided to use compact and agile vehicles that employ proven mechanical designs very suitable for the desert environment. 4-wheel drive ensures robust controllability even in slippery ground, and a roll cage protects the vehicle components from damage in case of a collision. The control system relies primarily on a differential GPS (Starfire) and a set of inertial sensors for navigating between the given set of waypoints. A sensor suite using infrared laser (LIDAR) and ultrasound sensing provides the capability of obstacle avoidance and path following. This paper shows the components of the vehicle and results from driving at the DGC.

70 citations


Journal ArticleDOI
TL;DR: It is concluded that the four-scroll chaotic attractor of this system, which is observed on both computer and oscilloscope, cannot actually exist in theory.
Abstract: Recently, we have investigated a new chaotic system of three-dimensional autonomous quadratic ordinary differential equations, and found that the system visually displays a four-scroll chaotic attractor confirmed by both numerical simulations and circuit implementation. In this paper, we further study the following question: Is it really true that this system can generate a four-scroll chaotic attractor, or is it only a numerical artifact? By a more careful theoretical analysis along with some further numerical simulations, we conclude that the four-scroll chaotic attractor of this system, which we observed on both computer and oscilloscope, cannot actually exist in theory. The fact is that this system has two co-existing two-scroll chaotic attractors that are arbitrarily close in the phase space for some system parameters, therefore extremely tiny numerical round-off errors or signal fluctuations will nudge the system orbit to switch from one attractor to another, thereby forming the seemingly single four-scroll chaotic attractor on screen display.

68 citations


Proceedings ArticleDOI
27 Aug 2004
TL;DR: This work combines real-time path planning and a simplified physics model to automatically compute control actions to drive a vehicle from an input state to desirable output states based on a behavior cost function.
Abstract: We present a method for synthesizing animations of autonomous space, water, and land-based vehicles in games or other interactive simulations. Controlling the motion of such vehicles to achieve a desirable behavior is difficult due to the constraints imposed by the system dynamics. We combine real-time path planning and a simplified physics model to automatically compute control actions to drive a vehicle from an input state to desirable output states based on a behavior cost function. Both offline trajectory preprocessing and online search are used to build an animation framework suitable for interactive vehicle simulations. We demonstrate synthesized animations of spacecraft performing a variety of autonomous behaviors, including Seek, Pursue, Avoid, Avoid Collision, and Flee. We also explore several enhancements to the basic planning algorithm and examine the resulting tradeoffs in runtime performance and quality of the generated motion.

59 citations


Proceedings ArticleDOI
27 Sep 2004
TL;DR: A shared control framework which allows the human operator to interact with the chair while it is performing an autonomous task, and ensures the user's safety while allowing the user to be in complete control of a potentially autonomous system.
Abstract: We describe the development and assessment of a computer controlled wheelchair equipped with a suite of sensors and a novel interface, called the SMARTCHAIR. The main focus of this paper is a shared control framework which allows the human operator to interact with the chair while it is performing an autonomous task. At the highest level, the autonomous system is able to plan paths using high level deliberative navigation behaviors depending on destinations or waypoints commanded by the user. The user is able to locally modify or override previously commanded autonomous behaviors or plans. This is possible because of our hierarchical control strategy that combines three independent sources of control inputs: deliberative plans obtained from maps and user commands, reactive behaviors generated by stimuli from the environment, and user-initiated commands that might arise during the execution of a plan or behavior. The framework we describe ensures the user's safety while allowing the user to be in complete control of a potentially autonomous system.

57 citations


Book ChapterDOI
Mark Cieliebak1
05 Apr 2004
TL;DR: In this paper, it is shown that the gathering problem can be solved if the robots are non-oblivious, i.e., if they are equipped with memory, and if they can sense the positions of the other robots, perform a deterministic algorithm, and then move towards a destination point.
Abstract: We study the Gathering Problem, where we want to gather a set of n autonomous mobile robots at a point in the plane. This point is not fixed in advance. The robots are very weak, in the sense that they have no common coordinate system, no identities, no central coordination, no means of direct communication, and no synchronization. Each robot can only sense the positions of the other robots, perform a deterministic algorithm, and then move towards a destination point. It is known that these simple robots cannot gather if they have no additional capabilities. In this paper, we show that the Gathering Problem can be solved if the robots are non-oblivious, i.e., if they are equipped with memory.

53 citations


Journal Article
TL;DR: DyKnow is a software framework which provides a set of functionalities for contextually accessing, storing, creating and processing qualitative knowledge and object structures representing aspects of its environment on the fly from raw or preprocessed sensor data.
Abstract: Any autonomous system embedded in a dynamic and changing environment must be able to create qualitative knowledge and object structures representing aspects of its environment on the fly from raw or preprocessed sensor data in order to reason qualitatively about the environment. These structures must be managed and made accessible to deliberative and reactive functionalities which are dependent on being situationally aware of the changes in both the robotic agent's embedding and internal environment. DyKnow is a software framework which provides a set of functionalities for contextually accessing, storing, creating and processing such structures. The system is implemented and has been deployed in a deliberative/reactive architecture for an autonomous unmanned aerial vehicle. The architecture itself is distributed and uses real-time CORBA as a communications infrastructure. We describe the system and show how it can be used in execution monitoring and chronicle recognition scenarios for UAV applications.

51 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for simultaneously creating two symmetrical chaotic attractors in a 3D linear autonomous system, and analyzed the dynamical behaviors of the new chaotic system.
Abstract: It has been demonstrated that a piecewise-linear system can generate chaos under suitable conditions. This paper proposes a novel method for simultaneously creating two symmetrical chaotic attractor––an upper-attractor and a lower-attractor––in a 3D linear autonomous system. Basically dynamical behaviors of this new chaotic system are further investigated. Especially, the chaos formation mechanism is explored by analyzing the structure of fixed points and the system trajectories.

36 citations


01 Jan 2004
TL;DR: This work proposes and evaluates an implementation of a framework that, ideally, provides the operator with a means to interact seamlessly with the autonomous control system using an architecture that incorporates sliding autonomy.
Abstract: We are developing a coordinated team of robots to assemble structures. The assembly tasks are sufficiently complex that no single robot, or type of robot, can complete the assembly alone. Even with a group of multiple heterogeneous robots, each adding its unique set of capabilities to the system, the number of contingencies that must be addressed for a completely autonomous system is prohibitively large. Teleoperating a multiple robot system, at the other extreme, is difficult and performance may be highly dependent on the skill of the operator. We propose and evaluate an implementation of a framework that, ideally, provides the operator with a means to interact seamlessly with the autonomous control system. Using an architecture that incorporates sliding autonomy, the operator can augment autonomous control by providing input to help the system recover from unexpected errors and increase system efficiency. Our implementation is motivated by results from an extended series of experiments we are conducting with three robots that work together to dock both ends of a

Proceedings ArticleDOI
29 Nov 2004
TL;DR: A testbed facility - the HoTDeC (hovercraft testbed for decentralized control) - developed by the authors at the University of Illinois, consisting of multiple autonomous hovercraft vehicles which are wirelessly networked.
Abstract: This paper describes a testbed facility - the HoTDeC (hovercraft testbed for decentralized control) - developed by the authors at the University of Illinois, consisting of multiple autonomous hovercraft vehicles which are wirelessly networked. This facility provides a flexible and state-of-the-art testbed for experimentation with inter-networked vehicles and sensors for decentralized and cooperative control, in a dynamically nontrivial setting.

Proceedings ArticleDOI
28 Sep 2004
TL;DR: The difference in performance is shown between a completely teleoperated system, a fully autonomous system, and one in which sliding autonomy has been incorporated, which is capable of accepting input from the operator at any time.
Abstract: We are developing a coordinated team of robots to assemble structures, a task that cannot be performed by any single robot. Even simple operations in this domain require complex interaction between multiple robots and the number of contingencies that must be addressed if the team is to act completely autonomously is prohibitively large. This scenario forces incorporation of a human operator. Ideally we would like a seamless interface between the robots and the operator such that the operator can interact with the system by helping it be more efficient or get out of a stuck condition or performing a task that the robots are not capable of themselves. We use an architecture that implements "sliding autonomy" to accomplish these goals. The system of robots can be fully autonomous as long as all is well. The system is capable of accepting input from the operator at any time, especially when it is unable to recover from a failure. We motivate this scenario with results from an extended series of experiments we have conducted with three robots that work together to dock both ends of a suspended beam. We show the difference in performance between a completely teleoperated system, a fully autonomous system, and one in which sliding autonomy has been incorporated.

Journal ArticleDOI
TL;DR: Following the recognition of their usefulness by the authorities and the scientific community, automatic water monitoring networks were developed again to be able to measure seawater with low power consumption, wireless communicating, and very sensitive.

Proceedings ArticleDOI
31 Oct 2004
TL;DR: By means of PDAC, stable 3-dimensional walking based on the robot inherent dynamics is realized and the proposed passive dynamic autonomous control method is presented.
Abstract: This paper proposes the novel control method named passive dynamic autonomous control PDAC is based on the following concept which Grizzle et al (2001, 2004) used previously: 1) point-contact 2) interlocking Point-contact means that the contact state between a robot and the ground is made point This makes it possible to control based on the robot inherent dynamics although the control becomes difficult We present the new approach using this concept to describe the robot dynamics as a 1-DOF autonomous system By means of PDAC, stable 3-dimensional walking based on the robot inherent dynamics is realized

Proceedings ArticleDOI
29 Dec 2004
TL;DR: In this article, a novel computer vision algorithm for collision detection and time-to-impact calculation based on feature density distribution (FDD) analysis is presented. But it does not require accurate feature extraction, tracking, or estimation of focus of expansion (FOE).
Abstract: Recent advances in many multi-discipline technologies have allowed small, low-cost fixed wing unmanned air vehicles (UAV) or more complicated unmanned ground vehicles (UGV) to be a feasible solution in many scientific, civil and military applications. Cameras can be mounted on-board of the unmanned vehicles for the purpose of scientific data gathering, surveillance for law enforcement and homeland security, as well as to provide visual information to detect and avoid imminent collisions for autonomous navigation. However, most current computer vision algorithms are highly complex computationally and usually constitute the bottleneck of the guidance and control loop. In this paper, we present a novel computer vision algorithm for collision detection and time-to-impact calculation based on feature density distribution (FDD) analysis. It does not require accurate feature extraction, tracking, or estimation of focus of expansion (FOE). Under a few reasonable assumptions, by calculating the expansion rate of the FDD in space, time-to-impact can be accurately estimated. A sequence of monocular images is studied, and different features are used simultaneously in FDD analysis to show that our algorithm can achieve a fairly good accuracy in collision detection. In this paper we also discuss reactive path planning and trajectory generation techniques that can be accomplished without violating the velocity and heading rate constraints of the UAV.

Book ChapterDOI
25 Mar 2004
TL;DR: A parameter inference algorithm for autonomous stochastic linear hybrid systems, which computes a maximum-likelihood model, given only a set of continuous output data of the system, and proposes a novel initialization technique to derive good initial conditions for the model parameters.
Abstract: We present a parameter inference algorithm for autonomous stochastic linear hybrid systems, which computes a maximum-likelihood model, given only a set of continuous output data of the system. We overcome the potentially intractable problem of identifying the sequence of discrete modes by using dynamic programming; we then compute the maximum-likelihood continuous models using an Expectation Maximization technique. This allows us to find a maximum-likelihood model in time that is polynomial in the number of discrete modes as well as in the length of the data series. We prove local convergence of the algorithm. We also propose a novel initialization technique to derive good initial conditions for the model parameters. Finally, we demonstrate our algorithm on some examples – two simple one-dimensional examples with simulated data, and an application to real flight test data from a dual-vehicle demonstration of the Stanford DragonFly Unmanned Aerial Vehicles.

Journal ArticleDOI
Dae Eun Kim1
TL;DR: An analysis of memory requirements for T-maze tasks well known as the road sign problem and the influence of noise on internal memory and behaviour performance is focused on, and it is shown that state machines with variable thresholds can improve the performance with a hysteresis effect to filter out noise.
Abstract: In autonomous agent systems, internal memory can be an important element to overcome the limitations of purely reactive agent behaviour. This paper presents an analysis of memory requirements for T-maze tasks well known as the road sign problem. In these tasks, a robot agent should make a decision about turning left or right at the T-junction in the approach corridor, depending on a history of perceptions. The robot agent in simulation can sense the light intensity influenced by light lamps placed on the bank of the wall. We apply the evolutionary multiobjective optimization approach to finite state controllers with two objectives: behaviour performance and memory size. Then the internal memory is quantified by counting internal states needed for the T-maze tasks in noisy environments. In particular, we focused on the influence of noise on internal memory and behaviour performance, and it is shown that state machines with variable thresholds can improve the performance with a hysteresis effect to filter o...

Journal ArticleDOI
TL;DR: This paper surveys recent results on kinematic controllability and on oscillatory controls and emphasizes how to translate geometric controllable conditions into algorithms for generating and tracking trajectories.

Proceedings ArticleDOI
01 Jan 2004
TL;DR: This paper discusses extensions of the basic prey model, showing how a risk-sensitive version can be used to alter policies when time or fuel is limited and ways an agent can estimate environmental parameters when such parameters are not known.
Abstract: Foraging theory is typically used to model animal decision making. We describe an agent such as an autonomous vehicle or software module as a forager searching for tasks. The prey model is used to predict which types of tasks an agent should choose to maximize its rate of reward. We expand and apply these concepts to fit an autonomous vehicle control problem and to provide insight into how to make high-level control decisions. We also discuss extensions of the basic prey model, showing how a risk-sensitive version can be used to alter policies when time or fuel is limited. Throughout the applications, we examine ways an agent can estimate environmental parameters when such parameters are not known.

Proceedings ArticleDOI
10 Nov 2004
TL;DR: In this paper, a control method named Passive Dynamic Autonomous Control (PDAC) is proposed, which is based on the following concept: 1) point-contact 2) interlocking.
Abstract: This paper proposes the novel control method named Passive Dynamic Autonomous Control. PDAC is based on the following concept which Grizzle et al10 used previously: 1) point-contact 2) interlocking. Point-contact means that the contact state between a robot and the ground is made point. This make it possible to control based on the robot inherent dynamics although the control becomes difficult. Interlocking means that all robot joints are connected and interlocked. We present the new approach using this concept to describe the robot dynamics as a 1-DOF autonomous system. Due to autonomy, this approach has two folIowing notabIe point: 1) period from foot-contact to next foot-contact can be obtained 2) there is a conservative quantity. In this paper, the coupling method of the sagittal and lateral motion that takes advantage of point 1 is proposed. In addition, the stabilizing method based on the conservative quantity is de signed. By means of PDAC and these methods, stable 3-dimensional walking based on the robot inherent dynamics is realized.

Proceedings ArticleDOI
02 Sep 2004
TL;DR: In this paper, the U.S. Army Research Laboratory undertook a series of experiments designed to assess the maturity of autonomous mobility technology for the Future Combat Systems Armed Robotic Vehicle concept.
Abstract: During FY03, the U.S. Army Research Laboratory undertook a series of experiments designed to assess the maturity of autonomous mobility technology for the Future Combat Systems Armed Robotic Vehicle concept. The experiments assessed the technology against a level 6 standard in the technology readiness level (TRL) maturation schedule identified by a 1999 Government Accounting Office report. During the course of experimentation, 646 missions were conducted over a total distance of ~560 km and time of ~100 hr. Autonomous operation represented 96% and 88% of total distance and time, respectively. To satisfy the TRL 6 "relevant environment" standard, several experimental factors were varied over the three-site test as part of a formal, statistical, experimental design. This paper reports the specific findings pertaining to relevant-environment questions that were posed for the study and lends additional support to the Lead System Integrator decision that TRL 6 has been attained for the autonomous navigation system.

Proceedings ArticleDOI
02 Sep 2004
TL;DR: The proposed creative controller like the adaptive critic controller has information stored in a dynamic database, plus a dynamic task control center that functions as a command center to decompose tasks into sub-tasks with different dynamic models and multi-criteria functions.
Abstract: Mobile robots must often operate in an unstructured environment cluttered with obstacles and with many possible action paths. That is why mobile robotics problems are complex with many unanswered questions. To reach a high degree of autonomous operation, a new level of learning is required. On the one hand, promising learning theories such as the adaptive critic and creative control have been proposed, while on other hand the human brain’s processing ability has amazed and inspired researchers in the area of Unmanned Ground Vehicles but has been difficult to emulate in practice. A new direction in the fuzzy theory tries to develop a theory to deal with the perceptions conveyed by the natural language. This paper tries to combine these two fields and present a framework for autonomous robot navigation. The proposed creative controller like the adaptive critic controller has information stored in a dynamic database (DB), plus a dynamic task control center (TCC) that functions as a command center to decompose tasks into sub-tasks with different dynamic models and multi-criteria functions. The TCC module utilizes computational theory of perceptions to deal with the high levels of task planning. The authors are currently trying to implement the model on a real mobile robot and the preliminary results have been described in this paper.

Proceedings ArticleDOI
03 Oct 2004
TL;DR: An autonomous system was designed and constructed to traverse the hostile desert terrain in the DARPA Grand Challenge robotics competition and demonstrated the capability to pass stationary vehicles and navigate sloping terrain while negotiating around fences and towers between sequential GPS waypoints.
Abstract: An autonomous system was designed and constructed to traverse the hostile desert terrain in the DARPA Grand Challenge robotics competition. Our autonomous system used GPS measurements in conjunction with a laser range finder to determine the passable terrain and to negotiate around natural and man-made obstacles on the route. The primary navigation portion of this system uses a scalable, heuristic array of data, and determines the preferred heading of the vehicle, factoring desired heading from a GPS sensor and obstacle data from a laser range finder. When implemented, this system demonstrated the capability to pass stationary vehicles and navigate sloping terrain while negotiating around fences and towers between sequential GPS waypoints.

Proceedings ArticleDOI
04 May 2004
TL;DR: In this paper, the authors present a method to establish real time path planning for three-dimensional (3D) autonomous mobile overhead crane system for prospective factories, which includes a visual system and a planning system.
Abstract: This paper presents a method to establish real time path planning for three-dimensional (3-D) autonomous mobile overhead crane system for prospective factories. Proposed crane system includes a visual system and a planning system. In the visual system, CCD image sensors, laser line markers and ultra sonic sensor (USS) are used to scan the environment of transfer space. Environmental map that describes the original transfer environment is built by CCD image sensors and laser line markers by oil-line while USS is used to renovate environmental map as it recognizes partial changes of transfer environment in terms of the quick scanning by on-line. The planning system that establishes the on-line path planning is proposed by expanding the previous research of the off-line path planning. By means of the potential method as its algorithm, updated potential field that describes the latest environment of transfer space is developed from the potential field developed in previous path planning and renovated environmental map in this system. The transfer path for obstacle avoidance is then constructed from the updated potential field and used as crane control references.

Journal ArticleDOI
TL;DR: In this paper, the existence of a nontrivial solution homoclinic to zero is proven for a Hamiltonian system with a superquadratic potential and the system is asymptotic to an autonomous system.
Abstract: A Hamiltonian system with a superquadratic potential is examined. The system is asymptotic to an autonomous system. The difference between the Hamiltonian system and the “problem at infinity,” the autonomous system, may be large, but decays exponientially. The existence of a nontrivial solution homoclinic to zero is proven. Many results of this type rely on a monotonicity condition on the nonlinearity, not assumed here, which makes the problem resemble in some sense the special case of homogeneous (power) nonlinearity. The proof employs variational, minimax arguments. In some similar results requiring the monotonicity condition, solutions inhabit a manifold homeomorphic to the unit sphere in a the appropriate Hilbert space of functions. An important part of the proof here is the construction of a similar set, using only the mountain-pass geometry of the energy functional. Another important element is the interaction between functions resembling widely separated solutions of the autonomous problem.

Proceedings ArticleDOI
25 Jul 2004
TL;DR: In this article, an autonomous mobile robot DREAM-3 has loaded an environmental map for the safety driving, where various sensor information is integrated, and the method to collect the initial position of the robot on the environmental map is described with the traveling control.
Abstract: The aim to develop DREAM-3 is make it travel in indoor environments such as in hospitals and/or welfare facilities for their practical use and serve to take care of old people and physically handicapped person. The autonomous mobile robot DREAM-3 has loaded an environmental map for the safety driving, where various sensor information is integrated. In this paper, method to collect the initial position of the robot on the environmental map is described with the traveling control.

Proceedings ArticleDOI
25 Oct 2004
TL;DR: A novel method for autonomous navigation and obstacle avoidance currently being implemented on the UC Bearcat Robot by synthesis of multiple sources of real-time data including stereo image disparity maps, tilt sensor data, and LADAR data with standard contour, edge, color, and line detection methods to provide robust and intelligent obstacle avoidance.
Abstract: The Bearcat "Cub" Robot is an interactive, intelligent, Autonomous Guided Vehicle (AGV) designed to serve in unstructured environments. Recent advances in computer stereo vision algorithms that produce quality disparity and the availability of low cost high speed camera systems have simplified many of tasks associated with robot navigation and obstacle avoidance using stereo vision. Leveraging these benefits, this paper describes a novel method for autonomous navigation and obstacle avoidance currently being implemented on the UC Bearcat Robot. The core of this approach is the synthesis of multiple sources of real-time data including stereo image disparity maps, tilt sensor data, and LADAR data with standard contour, edge, color, and line detection methods to provide robust and intelligent obstacle avoidance. An algorithm is presented with Matlab code to process the disparity maps to rapidly produce obstacle size and location information in a simple format, and features cancellation of noise and correction for pitch and roll. The vision and control computers are clustered with the Parallel Virtual Machine (PVM) software. The significance of this work is in presenting the methods needed for real time navigation and obstacle avoidance for intelligent autonomous robots.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
TL;DR: This work reduces the proliferation of microscopic states to a manageable set of macroscopic states, using a clustering method, to enable the interaction between humans and autonomous machines.