Showing papers on "Autonomous system (mathematics) published in 1993"
TL;DR: The performance of the AICC system is found to be superior to that of the human driver models considered and has a faster and better transient response that leads to a much smoother and faster traffic flow.
Abstract: Vehicle following and its effects on traffic flow has been an active area of research. Human driving involves reaction times, delays, and human errors that affect traffic flow adversely. One way to eliminate human errors and delays in vehicle following is to replace the human driver with a computer control system and sensors. The purpose of this paper is to develop an autonomous intelligent cruise control (AICC) system for automatic vehicle following, examine its effect on traffic flow, and compare its performance with that of the human driver models. The AICC system developed is not cooperative; i.e., it does not exchange information with other vehicles and yet is not susceptible to oscillations and "slinky" effects. The elimination of the "slinky" effect is achieved by using a safety distance separation rule that is proportional to the vehicle velocity (constant time headway) and by designing the control system appropriately. The performance of the AICC system is found to be superior to that of the human driver models considered. It has a faster and better transient response that leads to a much smoother and faster traffic flow. Computer simulations are used to study the performance of the proposed AICC system and analyze vehicle following in a single lane, without passing, under manual and automatic control. In addition, several emergency situations that include emergency stopping and cut-in cases were simulated. The simulation results demonstrate the effectiveness of the AICC system and its potentially beneficial effects on traffic flow. >
654 citations
TL;DR: The authors complete the solution of a problem posed by Bellman and show that closed nonlinear, autonomous, n-compartment systems can show the full gamut of possible behaviors of systems of ODES.
Abstract: Dynamic models of many processes in the biological and physical sciences which depend on local mass balance conditions give rise to systems of ordinary differential equations, many nonlinear, that are called compartmental systems. In this paper, the authors define compartmental systems, specify their relations to other nonnegative systems, and discuss examples of applications.The authors review the qualitative results on linear and nonlinear compartmental systems, including their relation to cooperative systems. They review the results for linear compartmental systems and then integrate and expand the results on nonlinear compartmental systems, providing a framework for unifying them under a few general theorems. In the course of that they complete the solution of a problem posed by Bellman and show that closed nonlinear, autonomous, n-compartment systems can show the full gamut of possible behaviors of systems of ODES.Finally, to provide additional structure to this study, the authors show how to partiti...
474 citations
150 citations
TL;DR: This work synthesizes and ana lyzes candidate walker configurations, implements and tests a walker of unprecedented capability and design, and develops insights regarding walker configuration and the class of orthogonal-legged walking robots.
Abstract: Robots that can competently, efficiently, and autonomously operate in extreme terrain do not exist. Although walking locomotion offers unique advantages, existing walking mech anisms are not suited...
93 citations
TL;DR: In this paper, the problem of observers for discrete-time nonlinear systems has been considered and a simple, easy-to-implement algorithm is given whose convergence properties are guaranteed for autonomous and forced systems.
64 citations
TL;DR: A dynamic task analysis is presented and used to develop a computational model of driving in traffic called Ulysses, which is a key component for developing autonomous vehicles and intelligent driver aids that operate in traffic, and provides a new tool for traffic research in general.
Abstract: Driving models are needed by many researchers to improve traffic safety and to advance autonomous vehicle design. However, existing models of driving maneuver selection are generally too abstract and do not describe the computation needed to select actions after observing objects. In this paper we present a dynamic task analysis and use it to develop a computational model of driving in traffic. This model has been implemented in a driving program called Ulysses as part of our research program in robot vehicle development. Ulysses encodes legal, safe and practical driving rules as constraints on acceleration and lane selection. The application of constraints depends on particular objects in the world; thus, when constraints are evaluated, they show exactly where the driver needs to look at that moment. We explain the specific knowledge in Ulysses with illustrations from a series of driving scenarios of increasing complexity. We also briefly discuss the computer perception system that Ulysses needs. Finally, we describe how Ulysses drives a robot in a simulated environment provided by our new traffic simulator called PHAROS, which is similar in spirit to previous simulators (such as NETSIM) but far more detailed. Our new driving model is a key component for developing autonomous vehicles and intelligent driver aids that operate in traffic, and provides a new tool for traffic research in general.
63 citations
TL;DR: The role of stored internal state (that is, memory) in the control of autonomous mobile robots is examined and an architecture embodying these design principles is briefly described, able to incorporate standard AI planning and world-modeling algorithms into a real-time situated framework.
Abstract: This article informally examines the role of stored internal state (that is, memory) in the control of autonomous mobile robots. The difficulties associated with using stored internal state are reviewed. It is argued that the underlying cause of these problems is the implicit predictions contained within the state, and, therefore, many of the problems can be solved by taking care that the internal state contains information only about predictable aspects of the environment. One way of accomplishing this is to maintain internal state only at a high level of abstraction. The resulting information can be used to guide the actions of a robot but should not be used to control these actions directly; local sensor information is still necessary for immediate control. A mechanism to detect and recover from failures is also required. A control architecture embodying these design principles is briefly described. This architecture was successfully used to control real-world and simulated real-world autonomous mobile robots performing complex navigation tasks. The architecture is able to incorporate standard AI planning and world-modeling algorithms into a real-time situated framework.
59 citations
TL;DR: It is shown that for constructing the set of initial states that can be driven to the origin asymptotically, one can restrict the search to a polyhedral set in the unstable subspace of the autonomous system, which yields a drastic reduction in the computational burden.
57 citations
01 Jan 1993
TL;DR: In this article, a dynamical system is defined as a map of a manifold to itself or a flow generated by an autonomous system of ordinary differential equations, and its essential ingredients are a lack of predictability and the exponential divergence of nearby orbits.
Abstract: A dynamical system in this article consists of a map of a manifold to itself or a flow generated by an autonomous system of ordinary differential equations. For definiteness, we shall discuss the discrete-time case, although most things here have their continuous-time versions. We shall not attempt to define “chaos, ” except to mention two of its essential ingredients:
1.
exponential divergence of nearby orbits
2.
lack of predictability.
34 citations
14 Jul 1993
TL;DR: An early warning system is described and possible responses to various traffic situations are suggested and various learning algorithms for decision making are described which is based on the current model and immediate history only.
Abstract: An understanding of the scenario in complex traffic situations is essential in order to give an early warning, or in an autonomous system, to intervene in the urban or motorway environment. A collision avoidance system needs both to predict possible collisions or hazards and to plan a less hazardous move in a critical situation. A crucial factor in the success of the system is the use of a priori knowledge. The classical problem with a knowledge-based decision making system is the acquisition and representation of the knowledge. It is diffcult to design and develop a system for real time auto-piloting in varied traffic environments. Neural networks are ideally suited for applications where a large training set is available because they can apply human decision making criteria in different situations. The learning processes encapsulate a wide variety of drivers' reactions to various scenarios. Neural networks' abilities to generalise their training to new scenarios in the light of driving experience and to make emotion-free decisions leads to a system that is adaptive and closely which resembles human action strategy. Recognition of a scenario is achieved by acquiring data about a scene from a variety of sensors. Visual data is preprocessed and features are extracted using a real-time image processing system, while microwave radar provides obstacle information and distances. This paper described an early warning system and suggests possible responses to various traffic situations. The paper focuses on various learning algorithms for decision making which is based on the current model and immediate history only. It would help if we could always recognise the dominant threat at every instant and avoid it by either slowing down or changing direction. In our analysis of situations using neural networks, the test cases show that reasonably such behaviour can be generated. In order to validate the auto pilot it is tested in parallel with expert drivers to assess the drivers' action in a number of scenarios. The network's intervention control is verified by independent observers. The intervention strategies are based on a number of rules by which an intervention controller is trained to generate various actions. These rules are fine tuned on-line to achieve reliable and repeatable actions.
19 citations
TL;DR: In this article, the stability of the periodic motion of a multi-dimensional periodic system with a small parameter is considered. But the system can be unstable and a nonlinear analysis is required, and the influence of small periodic terms on stability is established.
TL;DR: A dynamical concept model is put forward that builds cue models of the phenomena in the world, designs dynamical action sets, and makes them compete in a spreading-activation neural stage to reach decision in a two-dimensional conditionally probabilistic space.
Abstract: A brain model-based alternative to reinforcement learning is presented that integrates artificial neural networks and knowledge-based systems into one unit or agent for goal-oriented problem solving. The agent may possess inherited and learned artificial neural networks and knowledge-based subsystems. The agent has and develops ANN cues to the environment for dimensionality reduction (data compression) to ease the problem of combinatorial explosion. Here, a dynamical concept model is put forward that builds cue models of the phenomena in the world, designs dynamical action sets (concepts), and makes them compete in a spreading-activation neural stage to reach decision. The agent works under closed-loop control. Here we examine a simple robotlike object in a two-dimensional conditionally probabilistic space.
Patent•
17 Aug 1993
TL;DR: In this article, a switching control system for controlling connections on the physical plane and allowing the user systems to formulate their connection requests in an independent manner from the hardware architecture of the communications system is presented.
Abstract: The user software for controlling connections in communications system must be uncoupled from the hardware architecture of the communications system. A switching control system is disclosed which represents an autonomous system for controlling connections on the physical plane and which allows the user systems to formulate their connection requests in an independent manner from the hardware architecture of the communications system.
01 Mar 1993
TL;DR: The authors describe an autonomous system that performs closed loop control of a differential thermal analyzer and a gas chromatograph to identify minerals and organics in soil samples as an instantiation of an integrated agent architecture designed to autonomously control scientific equipment in remote locations.
Abstract: The authors describe an autonomous system that performs closed loop control of a differential thermal analyzer (DTA) and a gas chromatograph (GC) to identify minerals and organics in soil samples. The system is presented as an instantiation of an integrated agent architecture designed to autonomously control scientific equipment in remote locations. The motivational context and general requirements of the application are described, followed by a description of the DTA-GC problem in terms of specific requirements for integrated perception, analysis, planning and control. The AI techniques applied to each of the specified requirements are considered. The system implementation status is discussed. The original contributions include a general architecture that integrates perception, analysis, planning and control for scientific experiments. The new analysis instrument integrates two previously distinct methods. Issues at the integration level as well as those relating to the individual components are examined. >
02 Jun 1993
TL;DR: The Space Exploration Initiative of the United States of America includes plans for unmanned missions to Mars to investigate and examine the terrain and soil samples for a future manned mission, and the use of fuzzy logic in autonomous mobile vehicles is chosen.
Abstract: The Space Exploration Initiative of the United States of America includes plans for unmanned missions to Mars to investigate and examine the terrain and soil samples for a future manned mission. In particular, uncharted obstacles may interfere with the maneuvering of the system. It will be nearly impossible to control the system using radio hookups, as the delays are extensive, and therefore an intelligent autonomous system is necessary. Due to inherent uncertainties in the problem and the wish to design a system that uses intuitive approaches to navigation problems, we have chosen to explore the use of fuzzy logic in autonomous mobile vehicles.
TL;DR: The design and development of a robotic system with Traded and Shared Control capability, able to accept and execute commands both from a hand controller and an autonomous system, or a combination of the two, is described.
04 May 1993
TL;DR: This paper has developed a software system for autonomous navigation that provides for greater capability, and the entire system was tested in simulation, and a subset of the capability was demonstrated on a real vehicle.
Abstract: Autonomous cross-country navigation is essential for outdoor robots moving about in unstructured environments. Most existing systems use range sensors to determine the shape of the terrain, plan a trajectory that avoids obstacles, and then drive the trajectory. Performance has been limited by the range and accuracy of sensors, insufficient vehicle-terrain interaction models, and the availability of high-speed computers. As these elements improve, higher- speed navigation on rougher terrain becomes possible. We have developed a software system for autonomous navigation that provides for greater capability. The perception system supports a large braking distance by fusing multiple range images to build a map of the terrain in front of the vehicle. The system identifies range shadows and interpolates undersamples regions to account for rough terrain effects. The motion planner reduces computational complexity by investigating a minimum number of trajectories. Speeds along the trajectory are set to provide for dynamic stability. The entire system was tested in simulation, and a subset of the capability was demonstrated on a real vehicle. Results to date include a continuous 5.1 kilometer run across moderate terrain with obstacles. This paper begins with the applications, prior work, limitations, and current paradigms for autonomous cross-country navigation, and then describes our contribution to the area.
TL;DR: This paper presents a trajectory generation method using smooth functions for an automatic guidance system of an autonomous vehicle with two differentially driven wheels within structured environments using an incrementally generated smooth trajectory.
Abstract: This paper presents a trajectory generation method using smooth functions for an automatic guidance system of an autonomous vehicle with two differentially driven wheels within structured environments. A control algorithm based on an incrementally generated smooth trajectory gives a good performance when implemented on an experimental vehicle.
17 Oct 1993
TL;DR: A distributed architecture of such an autonomous system with the capability both to react to the actual circumstances and to control these reactions in order to fulfil the goals is presented and discussed.
Abstract: The author defines autonomy as the capability of a system to use at any time the actual circumstances to serve its purpose. This definition requires the capability both to react to the actual circumstances and to control these reactions in order to fulfil the goals. The reactiveness is achieved by a set of behaviors. The directedness is achieved by a cognitive layer structuring and exploiting the system history. A distributed architecture of such an autonomous system is presented and discussed. >
TL;DR: In this article, the main objective is to find an optimal positional control in feedback form for a linear autonomous system with a mixed cost functional, and the relationship between this problem and an optimal stabilizability problem is also investigated.
Abstract: The main objective of this paper is to find an optimal positional control in feedback form for a linear autonomous system with a mixed cost functional. The method of controllability functions is used. The relationship between this problem and an optimal stabilizability problem is also investigated, and several examples are presented.
TL;DR: In this article, a class of second order linear autonomous differential equations with distributed type deviating arguments is considered and it is proved that a necessary and sufficient condition for the oscillation of all solutions is that the associated characteristic equation have no real roots.
29 Nov 1993
TL;DR: The main techniques that prevent the influence of a fault in an autonomous distributed system from spreading to the whole system are described and several inter-subsystem communication methods are proposed and evaluated.
Abstract: This paper describes the main techniques that prevent the influence of a fault in an autonomous distributed system from spreading to the whole system. Several inter-subsystem communication methods are proposed and evaluated. From the standpoints of fault processing and processing load, frames should be sent though a data link over an ATM connection and when a fault occurs the link should be switched over without loss of data. A pilot system attains sufficient reliability without an excessive number of dynamic program steps. This autonomous control method will lead to a highly reliable switching node system with a large capacity. >
01 Jan 1993
TL;DR: A novel architecture named "Manager in the Computer" is proposed for solving complicated design problems in aero-space field, where intelligent managers implemented in the form of subprograms autonomously analyze the design problem and cooperatively make decisions to direct the search process using knowledge obtained by machine learning.
02 Jun 1993
TL;DR: In this paper, an adaptive hybrid force-position control is proposed to generate contact motion in an unstructured environment for space operations, where the desired motion is split into two parts where the force is controlled in the constrained direction in an adaptive manner while the position control takes place in the free space.
Abstract: This paper presents a comprehensive solution to the problem of robust execution of fine motions within the context of a Supervised Autonomous System and develops an adaptive control technique which provides on-line autonomous trajectory correction and compliant motion in an unstructured environment for space operations. The Adaptive Control Techniques have recently emerged as promising alternatives to the conventional methods of control, to generate contact motion. In Adaptive Hybrid Force-Position Control, the desired motion is split into two parts where the force is controlled in the constrained direction in an adaptive manner while the position control takes place in the free space. The environment parameters are identified on-line to increase the dynamic performance of the force control scheme.
TL;DR: In this article, some explicit criteria of absolute stability for the trivial solution of the real second canonical form of non-linear control system are given, which include and improve the criteria in paper [1].
Abstract: In this paper, some explicit criteria of absolute stability for the trivial solution of the real second canonical form of non-linear control system are given, which include and improve the criteria in paper [1]. By applying these criteria to the well-known equation of the longitudinal motion of aircraft, some results are obtained, which include and improve the corresponding results in papers [1, 2, 3, 4].
01 Nov 1993
01 Jan 1993
TL;DR: The ante-serveur is an autonomous system which automatically connects to the host and always use the same intuitive interface.
Abstract: The ante-serveur is an answer to the problem of end-user access to electronic resources: databases, library catalogs, and documentary products (videotex, internal services…). The ante-serveur is an autonomous system which automatically connects to the host and always use the same intuitive interface.