Showing papers on "Autonomous system (mathematics) published in 2000"

Algebraically Simple Chaotic Flows

Abstract: It came as a surprise to most scientists when Lorenz in 1963 discovered chaos in a simple system of three autonomous ordinary differential equations with two quadratic nonlinearities. This paper reviews efforts over the subsequent years to discover even simpler examples of chaotic flows. There is reason to believe that the algebraically simplest examples of chaotic flows with quadratic and piecewise linear nonlinearities have now been identified. The properties of these and other simple systems will be described.

A system for chaos generation and its implementation in monolithic form

Abstract: We propose a novel autonomous system for chaos generation based on a third-order abstract canonical mathematical model. Nonlinearity in this system is introduced by a bipolar switching constant which reflects the behaviour of a simple inverter circuit. Two implementations of the system are given. The first uses commercially available components while the second was designed on a CMOS chip. Numerical simulations and experimental results are provided.

Information-theoretic approach to decentralized control of multiple autonomous flight vehicles

Abstract: Decentralized systems require no central controller or center where information is fused or commands generated Information theoretic ideas have been previously used to develop optimal fusion algorithms for decentralized sensing and data fusion systems The work described in this paper aims to develop equivalent algorithms for the control of decentralized systems The methods and algorithms described center on the use of mutual information gain as a measure in choosing control actions Two example problems are described; area coverage for purposes of surveillance and navigation, and sensor management for cuing and hand-off operations The motivation for this work is the control of multiple unmanned air vehicles (UAVs)© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Obstacle detection by a forward looking sonar integrated in an autonomous underwater vehicle

Abstract: Autonomous underwater vehicles (AUV) by nature operate in partially unknown environments. Any obstacle lying in the path of the vehicle is a potential mission-terminating threat. Inclusion of a forward looking sensor would provide valuable information to the AUV. Threat assessment and navigation plans would use this information in order to avoid obstacles. Any such system should meet the requirements of an embedded autonomous system, that is small size and low power consumption. The obstacle detection system is to be integrated in the AUV via a common interface protocol. It is the intent of this paper to explore one possible solution to implementing such an obstacle detection system. The system used in this project is a forward looking sonar (FLS). This sonar system is a commercially available unit modified for performing obstacle detection tasks. With less than 4 W total power consumption this sonar can be integrated in an AUV. The small volume of the system allows easy placement in existing small AUV designs. The sonar control software is implementing in DOS on a PC/104 486 CPU. Filtered decision information is presented to the control logic of the existing AUV through a standard interface type (Lontalk network). A grid occupancy search method is used to detect the closest object in the vehicle's path. The region forward of the FLS is sub-divided into various cells. The cells are filled with the raw intensity data collected from the FLS sensor. For each filled cell, a cell signature is computed. The maximum signature cell is extracted from the grid. This cell contains transformed target information such as, range, bearing to target, and cell signature. The scanning scheme performs a first sweep at a short range for a quick detection of close targets, followed by a second sweep at a medium range. Cell signature definition and cell mapping are the research efforts associated with this paper. Experiments are performed on a moving platform, with the ultimate goal of testing the detection system integrated in a small AUV. This low-cost obstacle detection system can be easily attached to the existing FAU platforms, greatly improving the system safety and reliability of an AUV operation in high threat areas.

Piecewise-linear chaotic systems with a single equilibrium point

Abstract: As a unique paradigm for chaos, the various versions of Chua's circuits and equations consists of a three-dimensional autonomous system with a three-segment piecewise-linear function which gives rise to three equilibrium points. This paper considers the possibility of simplifying the system configurations of piecewise-linear chaotic systems based on the structures of Chua's systems. We study a new class of piecewise-linear three-dimensional autonomous system with a three-segment piecewise-linear function. However, unlike Chua's systems, the systems we study in this paper have only single equilibrium points. To find chaotic attractors from this class of systems, we use a systematic random-search process to search the parameter space. The searching process consists of three stages. For the first stage, we simply count the number of points on a Poincare section and find candidates for chaotic attractors. At the second stage, Lyapunov exponents are calculated for selecting chaotic attractors from the candidates. Finally, bifurcation diagrams constructed around the located chaotic attractors are used to find different types of chaotic attractors. Many qualitatively different chaotic attractors of this class of systems had been found and presented in this paper. Another method to simplify the configurations of a piecewise-linear chaotic system is to reduce the number of segments of the piecewise-linear function. We have developed some chaotic systems with a two-segment piecewise-linear function and which gives rise to two equilibrium points. Many color illustrations of chaotic attractors and bifurcation diagrams are presented.

Analysis of a nonsynchronized sinusoidally driven dynamical system

Abstract: A nonautonomous system, i.e. a system driven by an external force, is usually considered as being phase synchronized with this force. In such a case, the dynamical behavior is conveniently studied in an extended phase space which is the product of the phase space ℝm of the undriven system by an extra dimension associated with the external force. The analysis is then performed by taking advantage of the known period of the external force to define a Poincare section relying on a stroboscopic sampling. Nevertheless, it may so happen that the phase synchronization does not occur. It is then more convenient to consider the nonautonomous system as an autonomous system incorporating the subsystem generating the driving force. In the case of a sinusoidal driving force, the phase space is ℝm+2 instead of the usual extended phase space ℝm × S1. It is also demonstrated that a global model may then be obtained by using m + 2 dynamical variables with two variables associated with the driving force. The obtained model characterizes an autonomous system in contrast with a classical input/output model obtained when the driving force is considered as an input.

PRIMUS: autonomous driving robot for military applications

Abstract: This article describes the government experimental program PRIMUS (PRogram of Intelligent Mobile Unmanned Systems) and the achieved results of phase C demonstrated in summer 1999 on a military prooving ground. In this program there shall be shown the autonomous driving on an unmanned robot in open terrain. The most possible degree of autonomy shall be reached with today's technology to get a platform for different missions. The goal is to release the soldier from high dangerous tasks, to increase the performance and to come to a reduction of personnel and costs with unmanned systems. In phase C of the program two small tracked vehicles (Digitized Wiesel 2, airtransportable by CH53) are used. One as a robot vehicle the other as a command & control system. The Wiesel 2 is configured as a drive by wire-system and therefore well suited for the adaption of control computers. The autonomous detection and avoidance of obstacles in unknown, not cooperative environment is the main task. For navigation and orientation a sensor package is integrated. To detect obstacles the scene in the driving corridor of the robot is scanned 4 times per second by a 3D- Range image camera (LADAR). The measured 3D-range image is converted into a 2D-obstacle map and used as input for calculation of an obstacle free path. The combination of local navigation (obstacle avoidance) and global navigation leads to a collission free driving in open terrain to a predefined goal point with a velocity of up to 25km/h. A contour tracker with a TV-camera as sensor is also implemented which allows to follow contours (e.g. edge of a meadow) or to drive on paved or unpaved roads with a velocity up to 50km/h. In addition to these autonomous driving modes the operator in the command & control station can drive the robot by remote control. All the functions were successfully demonstrated in the summer 1999 on a military prooving ground. During a mission example the robot vehicle covered a distance of several kilometers in open terrain and on unpaved roads and performed a reconnaissance operation with the built-in RSTA- sensors. PRIMUS-C meets the requirements to drive autonomously and teleoperated in open terrain and on roads. The realized functions can be transfered to any vehicle and adapted to different mission requirements. This means that PRIMUS-C is a universal, modular and vehicle-independent platform for different military applications.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Open multiagent architecture extended to distributed autonomous robotic systems

Abstract: Our research deals with the design and experiment of a control architecture for an autonomous outdoor mobile robot which uses mainly vision for perception. In this case of a single robot, we have designed a hybrid architecture with an attention mechanism that allows dynamic selection of perception processes. Building on this work, we have developed an open multi-agent architecture, for standard multi-task operating system, using the C++ programming language and Posix threads. Our implementation features of efficient and fully generic messages between agents, automatic acknowledgement receipts and built-in synchronization capabilities. Knowledge is distributed among robots according to a collaborative scheme: every robot builds its own representation of the world and shares it with others. Pieces of information are exchanged when decisions have to be made. Experiments are to be led with two outdoor ActiveMedia Pioneer AT mobile robots. Distributed perception, using mainly vision but also ultrasound, will serve as proof of concept.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Real-time collision avoidance in space: the GETEX experiment

Abstract: Intelligent autonomous robotic systems require efficient safety components to assure system reliability during the entire operation. Especially if commanded over long distances, the robotic system must be able to guarantee the planning of safe and collision free movements independently. Therefore the IRF developed a new collision avoidance methodology satisfying the needs of autonomous safety systems considering the dynamics of the robots to protect. To do this, the collision avoidance system cyclically calculates the actual collision danger of the robots with respect to all static and dynamic obstacles in the environment. If a robot gets in collision danger the methodology immediately starts an evasive action to avoid the collision and guides the robot around the obstacle to its target position. This evasive action is calculated in real-time in a mathematically exact way by solving a quadratic convex optimization problem. The secondary conditions of this optimization problem include the potential collision danger of the robots kinematic chain including all temporarily attached grippers and objects and the dynamic constraints of the robots. The result of the optimization procedure are joint accelerations to apply to prevent the robot from colliding and to guide it to its target position. This methodology has been tested very successfully during the Japanese/German space robot project GETEX in April 1999. During the mission, the collision avoidance system successfully protected the free flying Japanese robot ERA on board the satellite ETS-VII at all times. The experiments showed, that the developed system is fully capable of ensuring the safety of such autonomous robotic systems by actively preventing collisions and generating evasive actions in cases of collision danger.

Classical exact output regulation

Abstract: The precise formulation and study of the classical exact output regulation problem is the topic of this chapter We consider a system with an exogenous input and a control input (both might be vector-valued) The exogenous input is generated by an autonomous system (ie a system without inputs) which is called the exosystem The objective is to find a feedback controller such that an output of the system converges to zero as time tends to infinity This can be used to model asymptotic tracking as well as asymptotic disturbance rejection

Intelligent steering control of an autonomous underwater vehicle

Abstract: This paper considers the development of three autopilots for controlling the yaw responses of an autonomous underwater vehicle model. The autopilot designs are based on the adaptive network-based fuzzy inference system (ANFIS), a simulated, annealing-tuned control algorithm and a traditional proportional-derivative controller. In addition, each autopilot is integrated with a line-of-sight (LOS) guidance system to test its effectiveness in steering round a series of waypoints with and without the presence of sea current disturbance. Simulation results are presented that show the overall superiority of the ANFIS approach.

Autonomous small robots for military applications

Abstract: We discuss the research developed in our lab these past years, leading to autonomous robots evolving in non-cooperative, even hostile outdoor environments.

An integrated vision system for alv navigation

Abstract: In this paper an integrated vision system for autonomous land vehicle is described. The vision system includes 2D and 3D vision modules and information fusion module. The task of 2D vision is to provide the physical and geometry information of road, and the task of 3D vision system is to detect the obstacles in the surrounding. Fusion module combines 2D and 3D information to generate a feasible region provided for vehicle navigation.

Self-organizing control of carrier sequence in AGV transportation system

Abstract: This paper proposes a system which realizes a collective autonomous behavior such as an autonomous conveyance order formation in the automatic guided vehicle (AGV) transportation system. We attempt to deal with a large scale distributed autonomous system in a dynamic environment. When using a global evaluation function in order to control each agent, it is necessary to rewrite the global evaluation function of the system whenever the environment changes. If we use such a method, the system cannot be regarded as a real distributed autonomous system. In this paper, we propose two ideas in order to realize a dynamically reconfigurable formation in a dynamic environment, namely, the learning based on the agent's own action and the interaction with the other agents by the relative evaluation. By using these ideas, it is shown that the dynamically reconfigurable formation emerges as an autonomous conveyance order formation of AGV transportation systems.

A technique for determining autonomous 3-ODEs being non-chaotic

Abstract: In this paper we discuss some features of chaotic dynamical systems described by autonomous three-dimensional ordinary differential equation (3-ODE) and establish a technique to determine the non-chaoticity of dynamical systems. As application, we use them to prove the non-chaotic behavior in some quadratic systems posed in the literature.

Autonomous data consistency for cooperative applications to fairly ally the data in heterogeneous systems

Abstract: Different information systems have been integrated to respond quickly to changing user needs. Important requirements for the integration are not halting the entire system, not violating each system's mission, and deriving the synergetic effect. The data characteristics of each system are different in nature because each system has its original mission. Heterogeneous systems can be easily integrated without stopping their operation and without intervening in another system's characteristics by the on-line property and the recursive model of the autonomous decentralized system (ADS). After integration, the application objects (AOs) exploit other systems' data, thus it becomes possible for application objects in different systems to cooperate by synchronizing with others. In a single system or homogeneous systems, the synchronization can be done with the same timing or timing sequence, but in a heterogeneous system, such synchronization is less effective because the data properties are different. A new concept, data alliance, has been proposed. In data alliance, each system must determine the data combination independently and also the combinations determined in the different systems must be consistent with each other. The autonomous system can be defined by the nature of the autonomous controllability and autonomous coordination and these characteristics must be satisfied even in heterogeneous systems.

Development of a simple autonomous system of small robots to clear unexploded submunition ordnance

Abstract: The Naval Explosive Ordnance Disposal Technology Division (NAVEODTECHDIV) has had an active program for several years for the development of technologies required to realize an autonomous system of small robots to clear an area of unexploded submunitions. The focus thus far has been on the technology elements themselves, with an emphasis on autonomous electronic control and processing. NAVEODTECHDIV is now developing demonstration systems to prove the feasibility of this application. At this stage, the systems are used in relatively benign terrain, and the targets are inert, not live munitions. However, this is adequate to show possibilities, and allow for experimentation before a full-scale development effort is initiated.

Computer vision system for an autonomous mobile robot

Abstract: The purpose of this paper is to compare three methods for 3- D measurements of line position used for the vision guidance to navigate an autonomous mobile robot. A model is first developed to map 3-D ground points into image points to be developed using homogeneous coordinates. Then using the ground plane constraint, the inverse transformation that maps image points into 3-D ground points is determined. And then the system identification problem is solved using a calibration device. Calibration data is used to determine the model parameters by minimizing the mean square error between model and calibration points. A novel simplification is then presented which provides surprisingly accurate results. This method is called the magic matrix approach and uses only the calibration data. A more standard variation of this approach is also considered. The significance of this work is that it shows that three methods that are based on 3-D measurements may be used for mobile robot navigation and that a simple method can achieve accuracy to a fraction of an inch which is sufficient in some applications.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Extended terrain reconstruction for autonomous vehicles

Abstract: This paper presents an image-processing algorithm for estimating both the egomotion of an outdoor robotic platform and the structure of the surrounding terrain. The algorithm is based on correlation, and is embedded in an iterative, multi-resolution framework. As such, it is suited to outdoor ground-based and underwater scenes. Both single-camera rigs and multiple-camera rigs can be accommodated. The use of multiple synchronized cameras results in more rapid convergence of the iterative approach. We describe how the algorithm operates and gives examples of its application in several robotic domains: Autonomous mobility of outdoor robots and Underwater robots.

Using Model-Based Reasoning for Autonomous Instrument Operation

Abstract: Multiprobe missions are an important part of NASA's future: Cluster, Magnetospheric Multi Scale, Global Electrodynamics and Magnetospheric Constellation are representatives from the Sun-Earth Connections Theme. To make such missions robust, reliable, and affordable, ideally the many spacecraft of a constellation must be at least as easy to operate as one spacecraft is today. To support this need for scalability, science instrumentation must become increasingly easy to operate, even as this same instrumentation becomes more capable and advanced. Communication and control resources will be at a premium for future instruments. Many missions will be out of contact with ground operators for extended periods either to reduce operations cost or because of orbits that limit communication to weekly perigee transits. Autonomous capability is necessary if such missions are to effectively achieve their operational objectives. An autonomous system is one that acts given its situation in a mission appropriate manner without external direction to achieve mission goals. To achieve this capability autonomy must be built into the system through judicious design or through a built-in intelligence that recognizes system state and manages system response. To recognize desired or undesired system states, the system must have an implicit or explicit understanding of its expected states given its history and self observations. The systems we are concerned with, science instruments, can have stringent requirements for system state knowledge in addition to requirements driven by health and safety concerns. Without accurate knowledge of the system state, the usefulness of the science instrument may be severely limited. At the same time, health and safety concerns often lead to overly conservative instrument operations further reducing the effectiveness of the instrument. These requirements, coupled with overall mission requirements including lack of communication opportunities and tolerance of environmental hazards, frame the problem of constructing autonomous science instruments. we are developing a model of the Low Energy Neutral Atom instrument (LENA) that is currently flying on board the Imager for Magnetosphere-to-Aurora Global Exploration (IMAGE) spacecraft. LENA is a particle detector that uses high voltage electrostatic optics and time-of-flight mass spectrometry to image neutral atom emissions from the denser regions of the Earth's magnetosphere. As with most spacecraft borne science instruments, phenomena in addition to neutral atoms are detected by LENA. Solar radiation and energetic particles from Earth's radiation belts are of particular concern because they may help generate currents that may compromise LENA's long term performance. An explicit model of the instrument response has been constructed and is currently in use on board IMAGE to dynamically adapt LENA to the presence or absence of energetic background radiations. The components of LENA are common in space science instrumentation, and lessons learned by modelling this system may be applied to other instruments. This work demonstrates that a model-based approach can be used to enhance science instrument effectiveness. Our future work involves the extension of these methods to cover more aspects of LENA operation and the generalization to other space science instrumentation.

Vision Based Navigation System for Autonomous Mobile Robot Locomotive Experiments Based on Variable Template Matching

Abstract: We have previously developed a navigation system for autonomous mobile robots. It can find landmarks on the ceiling to move and work. However it is impossible to recognize landmark in case that the size of landmark is different from the size of template. In such cases, the robot cannot continue to work. Therefor we proposed Variable Template Matching (VTM) which makes it possible to recognize landmarks of different sizes. We realize VTM by using the optimization method that is called Evolution Strategy (ES). The robot can recognize the landmark faster by binary density projection to infer landmark parameters. Minus Fuzzy Template is useful for the robot to avoid misidentifying.

An integrated vision system for ALV navigation

Abstract: In this paper an integrated vision system for autonomous land vehicle is described. The vision system includes 2D and 3D vision modules and information fusion module. The task of 2D vision is to provide the physical and geometry information of road, and the task of 3D vision system is to detect the obstacles in the surrounding. Fusion module combines 2D and 3D information to generate a feasible region provided for vehicle navigation.

The stability of the linear systems with delays

Abstract: In this paper, we study the linear autonomous system of differential difference equations with delays. Some simple and practical sufficient conditions of the hyperbolic cone and the asymptotic stable cone are established.

Examples of design and achievement of vision systems for mobile robotics applications

Abstract: Our goal is to design and to achieve a multiple purpose vision system for various robotics applications : wheeled robots (like cars for autonomous driving), legged robots (six, four (SONY's AIBO) legged robots, and humanoid), flying robots (to inspect bridges for example) in various conditions : indoor or outdoor Considering that the constraints depend on the application, we propose an edge segmentation implemented either in software, or in hardware using CPLDs (ASICs or FPGAs could be used too) After discussing the criteria of our choice, we propose a chain of image processing operators constituting an edge segmentation Although this chain is quite simple and very fast to perform, results appear satisfactory We proposed a software implementation of it Its temporal optimization is based on : its implementation under the pixel data flow programming model, the gathering of local processing when it is possible, the simplification of computations, and the use of fast access data structures Then, we describe a first dedicated hardware implementation of the first part, which requires 9CPLS in this low cost version It is technically possible, but more expensive, to implement these algorithms using only a signle FPGA© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

GAT/DeLiTe: an autonomous system for complete micro-gyroscope characterization

Abstract: The advancement of the MEMS micro-gyroscope development effort at the Jet Propulsion Laboratory has necessitated the production of autonomous test equipment. A cost effective and efficient method of performing qualification testing and lifetime characterization was developed in response. Implemented as a set of two independent programs, the Gyroscope Automated Testbed (GAT) and the Device Lifetime Testbed (DeLiTe), provide short-term stability and response characterization and long-term stability analysis. The two programs were designed to automate the time consuming task of performance analysis, accommodate the simultaneous testing of multiple devices, and reduce the risk of operator induced errors. Both systems are implemented on personal computers hardware. Specialized hardware or dedicated systems are not required, which results in a low cost system solution. This paper discusses the design and implementation of the two programs.