Showing papers on "Autonomous system (mathematics) published in 1998"

Feedback Control of an Omnidirectional Autonomous Platform for Mobile Service Robots

Abstract: This paper proposes a feedback control scheme for an omnidirectional holonomic autonomous platform, which is equipped with three lateral orthogonal-wheel assemblies. Firstly, the dynamic properties of the platform are studied, and a dynamic model suitable for the application of control is derived. The control scheme constructed is of the resolved-acceleration type, with PI and PD feedback. The control scheme was experimentally applied to an actual mobile robotic platform. The results obtained show that full omnidirectionality can be achieved with decoupled rotational and translational motions. Omnidirectionality is one of the principal requirements for mobile robots designed for health-care and other general-hospital services.

The Development, Control and Operation of an Autonomous Robotic Excavator

Abstract: The excavation of foundations, general earthworks and earth removal tasks are activities which involve the machine operator in a series of repetitive operations, suggesting opportunities for the automation through the introduction of robotic technologies with subsequent improvements in machine utilisation and throughput. The automation of the earth removal process is also likely to provide a number of other benefits such as a reduced dependence on operator skills and a lower operator work load, both of which might be expected to contribute to improvements in quality and, in particular, the removal of the need for a local operator when working in hazardous environments. The Lancaster University Computerised Intelligent Excavator or LUCIE has demonstrated the achievement of automated and robotic excavation through the implementation of an integrated, real-time, artificial intelligence based control system utilising a novel form of motion control strategy for movement of the excavator bucket through ground. Having its origins in the systematic observation of a range of machine operators of differing levels of expertise, the control strategy as evolved enables the autonomous excavation of a high quality rectangular trench in a wide variety of types and conditions of ground and the autonomous removal of obstacles such as boulders along the line of that trench. The paper considers the development of the LUCIE programme since its inception and sets out in terms of the machine kinematics the evolution and development of the real-time control strategy from an implementation on a one-fifth scale model of a back-hoe arm to a full working system on a JCB801 360° tracked excavator.

Feature space transformation using genetic algorithms

Abstract: The authors have developed an autonomous system that transforms feature spaces to improve classification techniques. They apply their method to an eye-detection face recognition system, demonstrating substantially better classification rates than competing systems.

A transportable neural-network approach to autonomous vehicle following

Abstract: This paper presents the development and testing of a neural-network module for autonomous vehicle following. Autonomous vehicle following is defined as a vehicle changing its own steering and speed while following a lead vehicle. The strength of the developed controller is that no characterization of the vehicle dynamics is needed to achieve autonomous operation. As a result, it can be transported to any vehicle regardless of the nonlinear and often unobservable dynamics. Data for the range and heading angle of the lead vehicle were collected for various paths while a human driver performed the vehicle following control function. The data was collected for different driving maneuvers including straight paths, lane changing, and right/left turns. Two time-delay backpropagation neural networks were then trained based on the data collected under manual control-one network for speed control and the other for steering control. After training, live vehicle following runs were done under the neural-network control. The results obtained indicate that it is feasible to employ neural networks to perform autonomous vehicle following.

Hyperchaos from a 4-D manifold piecewise-linear system

Abstract: A piecewise-linear 4-D autonomous system with hyperchaotic behavior is proposed. The system is analyzed by constructing a 2-D return map. We describe this map explicitly and give theoretical evidence for hyperchaos generation. An implementation example is also provided, and its chaotic behavior is demonstrated.

A customizable coordination service for autonomous agents

Abstract: We address the problem of constructing multiagent systems by coordinating autonomous agents, whose internal designs may not be fully known. We develop a customizable coordination service that (a) takes declarative specifications ofthe desired interactions, and (b) automatically enacts them. Our approach is based on temporal logic, and has a rigorous semantics and a naturally distributed implementation.

Self-Localisation in the ‘Senario’ Autonomous Wheelchair

Abstract: This paper introduces the Focused Stochastic Diffusion Network as a novel method of self-localisation for an autonomous wheelchair in a complex, busy environment. The space of possible positions is explored in parallel by a set of cells searching in a competitive co-operative manner for the most likely position of the wheelchair in its environment. Experimental results from the SENARIO autonomous wheelchair project indicate the technique is practical and robust.

Dynamical systems for the behavioral organization of autonomous robot navigation

Abstract: We present an architecture for the behavioral organization of autonomous robots. For the example of navigation, we describe how complex behavior can be broken up into multiple elementary behaviors. The overall behavior is generated by activating and deactivating the elementary behaviors dependent on both the sensor input and the intrinsic logics of the behavioral plan needed to fulfill the task. The elementary behaviors as well as their organization into behavioral sequences are achieved by appropriately designed nonlinear dynamical systems. We show how intrinsicly discrete functionalities like counting and decision making can be realized by nonlinear dynamical systems and how these dynamics can be coupled stably and flexibly.

Spatially self-similar spherically symmetric perfect-fluid models

Abstract: Einstein's field equations for spatially self-similar spherically symmetric perfect-fluid models are investigated. The field equations are rewritten as a first-order system of autonomous differential equations. Dimensionless variables are chosen in such a way that the number of equations in the coupled system is reduced as far as possible and so that the reduced phase space becomes compact and regular. The system is subsequently analysed qualitatively with the theory of dynamical systems.

Periodic steady-state analysis of an autonomous power electronic system by a modified shooting method

Abstract: This paper proposes a new periodic steady-state analysis method for an autonomous power electronic system by solving a periodic steady-state condition and a switch condition simultaneously for finding periodic initial values. The method utilizes switching operations, which are a characteristic feature of a power electronic circuit, to express variations of state transitions due to a variation of the period. There is no need to include the period as an unknown variable. This modification eliminates two disadvantages in the conventional method-one is failure of finding solutions for one fixed state variable due to a wrong initial value outside its operation range, and the other is that an initial time does not coincide with a starting time of a circuit topological mode.

Mission control of the MARIUS autonomous underwater vehicle: system design, implementation and sea trials

Abstract: This paper describes the design and implementation of a mission control system for the MARIUS autonomous underwater vehicle (AUV). The framework adopted for system design builds on the key concept of vehicle primitive, which is a parametrized specification of an elementary operation performed by the vehicle. Vehicle primitives are obtained by coordinating the execution of a number of concurrent system tasks, which are parametrized specifications of classes of algorithms or procedures that implement basic functionalities in an underwater robotic system. Vehicle primitives are in turn logically and temporally chained to form more abstract mission procedures, which are executed as determined by mission programs, in reaction to external events. System task design is carried out using well-established tools from continuous- or discrete-time dynamic system theory, and finite-state automata to describe their logical (event-based) interaction with vehicle primitives. The design and analysis of vehicle primitives ...

Autonomous Intelligent Cruise Control with Actuator Delays

Abstract: In this paper, we consider the control design problem of vehicle following systems with actuator delays. An upper bound for the time delays is first constructed to guarantee the vehicle stability. Second, sufficient conditions are presented to avoid slinky-effects in the vehicle following. Next, zero steady state achieved by the proposed controller is proven. Finally, simulations are given to examine our claims.

Experiments in realising cooperation between autonomous mobile robots

Abstract: This paper describes experiments in cooperation using autonomous mobile robots to perform a cleaning task. The robots have heterogeneous capabilities and the task is designed so that cooperation is required. Each experiment increases the sophistication of the cooperation scheme to assess the effect on task performance. The experiments range from using emergent cooperation with no communication to explicit cooperation and communication. We also propose an action selection mechanism that can also be used for distributed planning of joint actions inspired by the way primates co-construct joint plans.

Dilaton electromagnetic bianchi-i cosmologies

Abstract: The Einstein-Maxwell dilaton field equations for a Bianchi-I geometry are written as an autonomous system of differential equations The general solution for this system is obtained and its main properties are discussed

Long distance outdoor navigation of an autonomous mobile robot by playback of Perceived Route Map

Abstract: In this paper, we report a development of an autonomous mobile robot for long distance outdoor navigation in our university campus. We propose how to generate a long distance Perceived Route Map (PRM), a position-based navigation algorithm using PRM, and incremental integration of the robot system by multiple processors and multiple agents. Furthermore, we developed an experimental robot system and conducted experiments of autonomous navigation using PRM in our university campus. Finally, from experimental results, we discuss open problems and future work in outdoor navigation.

Autonomous vehicle parallel parking design using function fitting approaches

Abstract: One of the most fundamental problems in the development of an intelligent highway system or an autonomous mobile robot system for factory use is to find the necessary input control variables for smooth and safe movement of the vehicle, or robot, between any two configurations. In this paper it is demonstrated that this problem can be converted into one of finding a fitting function which satisfies the boundary conditions. Three curves, a quintic polynomial, a cubic polynomial and a triangular function are developed to perform the parallel transfer manoeuvre which forms the basis of several important manoeuvres such as reverse parking, moving off, negotiating a stationary obstacle, overtaking a moving vehicle, and changing lane. A detailed discussion of the effect of the vehicle's steering angle limit on the feasibility of these manoeuvres is presented. Simulation results using three typical vehicles, a long commercial vehicle, an ordinary car, and a small laboratory robot, travelling along three curves are also presented and discussed. Based on the comparative study, some suggestions for further work are made. Compared with other methods, this approach is simple and provides excellent simulation of human driver techniques. The paper concludes with a focused discussion about the integration of these techniques with satellite based GPS systems for automated vehicle guidance on highways.

Miniaturized Autonomous Robot

Abstract: Many projects developing the miniaturized autonomous robot have been carried out in the whole world. This paper deals with our challenges developing a miniaturized autonomous robot. The miniaturized autonomous robot is defined as the miniaturized closed-loop system with micro processor, microactuators and microsensors. We have developed the micro autonomous robotic system (MARS) consisting of the microprocessor, microsensors, microactuators, communication units and batteries. The MARS controls itself by the downloaded program supplied through the IR communication system. In this paper, we demonstrate several performance of the MARS, and discuss the properties of the miniaturized autonomous robot.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An evolutionary strategy for achieving autonomous navigation

Abstract: An approach is presented for the evolutionary development of supervised autonomous navigation capabilities for small "backpackable" ground robots, in the context of a DARPA-sponsored program to provide robotic support to small units of dismounted warfighters. This development approach relies on the implementation of a baseline visual servoing navigation capability, including tools to support operator oversight and override, which is then enhanced with semantically referenced commands and a mission scripting structure. As current and future machine perception techniques are able to automatically designate visual servoing goal points, this approach should provide a natural evolutionary pathway to higher levels of autonomous operation and reduced requirements for operator intervention.

Approximate dynamic buckling loads of discrete systems via geometric considerations of their energy surface

Abstract: The nonlinear dynamic buckling characteristics of multi-degree-of-freedom (MDOF), autonomous, non-dissipative structural systems are investigated both qualitatively and quantitatively. Attention is focused on systems which under the same loading applied statically exhibit snapping. The field equations are highly nonlinear ordinary differential equations (O.D.E.) which can be integrated only numerically. Instead, a qualitative analysis based on energy and geometric criteria is performed which allows to readily obtain approximate dynamic buckling loads, the accuracy of which can be established a priori.

Etherbot - An autonomous mobile robot on a local area network radio tether

Abstract: It is well understood in the robotics research community that an autonomous mobile robot which is physically tethered to extend battery power limits, harness more powerful computational resources, allow convenient monitoring of sensor and process components or to increase the pay load is, at best, just a laboratory curio since the tether renders the vehicle more or less useless in many real working situations because of potential entanglement and actual range limitations. This paper demonstrates that it is feasible and advantageous to build a mobile robot which can navigate competently in an initially unknown and time-varying obstacle cluttered environment with most of the above advantages of tethered operation but without a physical tether; instead, a virtual tether based on a radio ethernet bridge is used.

Auto-agent: a behavior-based architecture for mobile navigation

Abstract: The design and construction of mobile robots is as much art as a science. In hardware architecture, researchers tend to construct a low-cost and reliable platform which equips with various sensory system for sensing the change of the environment to offer useful information to the navigation system. An autonomous navigation system plays a role in an mobile robot as the brain in human being. It generates action command according to those sensory data from the perception system to direct the mobile robot to go to desired positions or accomplish useful tasks without human intervention in real-world. An important problem in autonomous navigation is the need to cope with the large amount of uncertainty that is inherent of natural environment. Therefore the development of techniques for autonomous navigation in real-world environments constitutes one of the major trends in the current research on robotics. Inspired with the concept of software agents, reactive control and behavior-based control, a modular architecture, called Auto-agent, for mobile navigation is proposed. The main characteristic of Auto-agent is as following: Behavioral agents cooperate by means of communicating with other behavioral agents intermittently to achieve their local goal and the goals of the community as a whole because no one individually has sufficient competence, resources and information to solve the entire problem. Auto-agent gains advantages from the characteristics of distributed system, it offers the possibility to find an acceptable solution with a reasonable time and complexity range. Besides, the modular structure is convenient for an engineer to construct a new behavioral agent and to add it into Auto-agent.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Autonomous strategy organization in the dynamical quantitative environment

Abstract: This paper proposes a system, which manages both efficiency and flexibility in the manufacturing system. It has been considered that an autonomous distributed system is superior to a centralized system in terms of fail-proof expansion, load dispersion, flexibility, and the possibility of the evolution. However, it is difficult to manage both efficiency and flexibility according to conventional method in an autonomous distributed system. To solve the problem, we propose a method. The method is that the carrier organizes the whole number of the carrier in the system, according to the volume of the task and the complexity of it. And we evaluate the proposed method of self-organizing behavior by a multi-AGV autonomous system in the quantitative dynamic environment. It shown that the system has higher efficiency in this system than in the centralized system with self-organization in the quantitative dynamic environment.

Autonomous outdoor mobile robot navigation: The EDEN project

Abstract: A cross-country rover cannot rely in general on permanent and immediate communications with a control station. This precludes direct teleoparation of its motions. It has therefore to be endowed with a large autonomy in achieving its navigation. We have designed and experimented with the mobile robot ADAM a complete system for autonomous navigation in a natural unstructured environment. We describe this work in this paper. The approach is primarly based on the adaptation of the perception and motion actions to the environment and to the status of the robot. The navigation task involves several levels of reasoning, several environment representations, and several action modes. The robot is able to select sub-goals, navigation modes, complex trajectories and perception actions according to the situation.

Adaptive fuzzy approach to modeling of operational space for autonomous mobile robots

Abstract: Robots operating in an unstructured environment need high level of modeling of their operational space in order to plan a suitable path from an initial position to a desired goal. From this perspective, operational space modeling seems to be crucial to ensure a sufficient level of autonomy. In order to compile the information from various sources, we propose a fuzzy approach to evaluate each unit region on a grid map by a certain value of transition cost. This value expresses the cost of movement over the unit region: the higher the value, the more expensive the movement through the region in terms of energy, time, danger, etc. The approach for modeling, proposed in this paper, employs fuzzy granulation of information on various terrain features and their combination based on a fuzzy neural network. In order to adapt to the changing environmental conditions, and to improve the validity of constructed cost maps on-line, the system can be endowed with learning abilities. The learning subsystem would change parameters of the fuzzy neural network based decision system by reinforcements derived from comparisons of the actual cost of transition with the cost obtained from the model.

Development of a fuzzy behavioural controller for an autonomous vehicle

Abstract: This paper considers the development of a fuzzy behavioural controller for an autonomous vehicle. The motivation for the work and the issues which need to be addressed are described. An overview of deliberative and reactive controllers is presented leading to the specification of a behavioural controller utilising fuzzy motor schemas and a fuzzy behavioural architecture. The paper concludes with a description of the definition and selection of inhibition schemes.

Autonomous control system with artificial intelligence

Abstract: The autonomous system includes integrated sensors, functions over an expanded period as an independent unit, and undertakes thereby a diversity of tasks which are necessary for the accomplishment of predetermined targets, whereby it responds to stimuli produced by the sensors. The system is built from a number of function modules (40.1, 40.2, ..., 40.n) which are equipped with artificial intelligence, whereby they comprise a structure which enables a self-organization, a learning, and an adjustment to changing situations. The function modules communicate at least partially with each other and form, in combination, a model of the actual world. The system interacts over the sensors (20) and actuators (22) with the actual world.

Navigation and control of blind robots in sensorized environments

Abstract: In this paper we discuss a new approach for developing useful robotic systems. The main idea is to simplify the robotic systems by eliminating the sensory and control hardware from the robotic platform. Such `sensor-less' systems have significant advantages over the more traditional `sensor-driven' systems. The paper demonstrates the efficacy of this new approach for autonomous navigation of removing robots that require no onboard sensing or control.

Fault tolerance of autonomous decentralized adaptive control systems

Abstract: Modem control theory based on the feedback of all states does not give a design method which tolerates some failure of sensors or actuators. Decentralized control, which stabilizes the interconnected subsystems by means of local feedback control, is considered to have more fault tolerance than centralized control systems do. This paper introduces a mathematical model of a decentralized adaptive control and analyzes the fault tolerance of the decentralized adaptive control system, in which an intelligence is distributed as local adaptive controllers.