Showing papers on "Autonomous system (mathematics) published in 1996"

Odor-source localization in the clean room by an autonomous mobile sensing system

Abstract: Experiments on odor-source localization using an autonomous mobile system were performed in a clean room A new exploratory algorithm was developed since the algorithm of upwind searching previously developed by our group was found to be applicable only on a limited situation The switchover of two strategies, moving upwind and along the gas-concentration gradient, was introduced to extend the applicable area A threshold value of the gas sensor output used for exchanging two strategies was automatically adjusted during localization movements As the flexibility of the system was enhanced, an ethanol source was successfully localized from almost anywhere in the prepared measurement space

Chaotic behavior in first-order autonomous continuous-time systems with delay

Abstract: In this letter we present a very simple model described by an autonomous continuous-time difference-differential equation with only one variable. By choosing suitable parameters and delay, chaotic behavior has been observed, dynamics of the system are analyzed briefly. This indicates that chaos can occur even in one-dimensional continuous-time systems with delay.

Optimization and control of autonomous renewable energy systems

Abstract: Recently, there has been a growing interest in harnessing renewable energy resources particularly for electricity generation. One of the main concerns in the design of an electric power system that utilizes renewable energy sources, is the accurate selection of system components that can economically satisfy the load demand. This depends on the load that ought to be met, the capacity of renewable resources, the available space for wind machines and solar panels, and the capital and running costs of system components. Once size optimization is achieved, the autonomous system must be controlled in order to correctly match load requirements with instantaneous variation of input energy. In this paper, a new formulation for optimizing the design of an autonomous wind-solar-diesel-battery energy system is developed. This formulation employs linear programming techniques to minimize the average production cost of electricity while meeting the load requirements in a realiable manner. The computer program developed reads the necessary input data, formulates the optimization problem by computing the coefficients of the objective function and the constraints and provides the optimum wind, solar, diesel, and battery ratings. In order to study the effect of parameters predefined by the designer on the optimum design, several sensitivity analysis studies are performed, and the effects of the expected energy not served, the load level, the maximum available wind area, the maximum available solar area, and the diesel engines' lifetime are investigated. A controller that monitors the operation of the autonomous system is designed. The operation of this controller is based on three major policies; in the first, batteries operate before diesel engines and hence the storage system acts as a fuel saver, while in the second diesel engines are operated first so that the unmet energy is lower but the fuel cost is high. According to the third policy, the supply is made through diesel engines only. This is done for the purpose of making a performance comparison between the isolated diesel system and the hybrid renewable energy system. The proposed optimization and control techniques are tested on Lebanese data. Although three different control policies have been adopted in this work, the software is able to accommodate other policies.

Perception, planning, and control for autonomous walking with the Ambler planetary rover

Abstract: Producing a robotic system that can operate autonomously on other planets is a challenging task: The robot must be ex tremely self-reliant; it must be able to operate on a limited power budget; and it must be able to traverse a wide range of rugged terrain features. This article describes an integrated software system that combines perception, planning, real-time control, and task-level control to navigate autonomously the Ambler, a six-legged rover. The overall approach to walking is highly deliberative: Where actions are goal-directed, steps are planned out in detail using explicit models of the terrain and the vehicle, and moves are checked for safety prior to execution. We believe that this approach is well-suited to meet ing the challenges of reliability, efficiency, and terrainability faced by autonomous planetary rovers. The Ambler system has been extensively tested, both indoors and outdoors, and the results confirm our expectations regarding the degree of system capability and performance afforde...

Global and local path planning in natural environment by physical modeling

Abstract: In the field of robotics, some autonomous vehicles work in natural sites. One problem for the autonomous system is to plan a path to the goal. A usual method uses potential fields to find a global path. With this method, obstacles must be clearly defined. But this is not the case in such natural environments. A new physically based potential method is introduced to find paths such as, for instance, a winding path to a pass. Moreover, locally, vehicles have to cope with a geometrically unstable environment and thus have a complex dynamic behavior. Thus it is necessary to elaborate a physical model of the robot-environment system. Generally, the two plannings, global and local, are independent. The introduced potential method resorts to the simulations of the vehicles to find a feasible path.

Door-opening behavior of an autonomous mobile manipulator by sequence of action primitives

Abstract: A goal of this research is to accomplish a long distance navigation task by an autonomous mobile manipulator, including a behavior of Passing through a doorway. In our approach to this problem, we apply the concept of action primitives to the mobile manipulator control system. Action primitives are defined as unit elements of a complex behavior (such as door opening behavior), which control a robot according to a sequence of planned motion primitives. An important feature of the concept is that each action primitive is designed to include an error adjustment mechanism to cope with the accumulated position error of the mobile base. In this article, we report on the design and implementation of action primitives for a door opening task, and show experimental results for Passing through a doorway by an autonomous mobile manipulator using sequences of action primitives.

A simulation study on autonomous decentralized mechanism in fish behaviour model

Abstract: The behaviour of a fish school is considered an interesting phenomenon because a fish school behaves differently in various situations. The paper considers a fish school as an autonomous decentralized system and constructs a mathematical model for the autonomous decentralized mechanism. Simulation results show that, by varying the quantity of information exchange among members in school, the present model describes fish behaviour not only for a school with fixed configuration but also for that with variable form. Furthermore, a remarkable difference in fish trajectory is found between the two schools.

Local perception maps for autonomous robot navigation

Abstract: This paper describes a mobile robotics system that was implemented and is capable of building instantaneous representations of the free space available, and use those representations to perform navigation. The free space representations are done by means of perception maps specially designed to hold and combine ultrasonic data. The maps are built by neural network appropriately trained to minimise undesired ranging errors due to specular reflections that is achieved by taking advantage of the redundancy of sensorial data. The concept of local navigation is developed as a new navigation approach, and is based on full independence on the environment, relying purely on sensorial perception. Local motion is generated according to simple generic behaviour descriptions: the local navigation strategies. The system which was implemented guarantees a safe local motion throughout the environment, requiring no a priori information nor any pre-defined path to follow. An adequate navigation architecture integrates the local navigation module within a framework of other several modules for more complete navigation tasks. The results obtained are quite promising in pointing the way to a truly autonomous system.

Analog VLSI motion projects at Caltech

Abstract: We present different compact analog VLSI motion sensors that compute the 1-D velocity of optical stimuli over a large range and are suitable for integration in focal plane arrays. They have been extensively tested and optimized for robust performance under varying light conditions. Since their output signals are only weakly dependent on contrast, they directly extract optical flow data from an image. Focal plane arrays of such sensors are particularly interesting for application in single-chip systems that perform navigation tasks for moving robots or vehicles, where light weight, low power consumption, and real-time processing are crucial. Several monolithic motion-processing systems based on such velocity sensors have been built and tested. We describe here three chips, designed for the determination of the focus of expansion, the estimation of the time to contact, and the detection of motion discontinuities respectively. The first two systems have been specifically designed for vehicle navigation tasks. The choice of this application domain allows us to make a priori assumptions about the optical flow field that simplifies the structure of the systems and improves their overall performance. The motion-discontinuity-detection system can be more generally used to segment images based on the velocities of its different domains with respect to the camera. It is particularly useful for background-foreground segregation in the case of ego-motion of an autonomous system in a static environment. Tests results of the three systems are presented and their performance is evaluated.

Cooperative Manipulation by Autonomous Intelligent Robots

Abstract: Cooperative manipulation by autonomous intelligent robots promises fertile potential for improving the ability of robotic manipulation and expanding the domain where robots may be used. This paper focuses on the method for calculating the optimal force of each robot based on local sensor feedback and high-level communication. First, we propose adaptive force direction control, which is useful for monitoring the state of force equilibrium, and then describe the theoretical background of this control method. Second, we describe the strategy to find the proper force using our proposed control method. We also describe a control system architecture which is suitable for these operations. In this control system, each manipulator motion function, each sensor function, and each message-passing operation are programmed as primitive tasks which run in parallel. Third, we illustrate the usefulness of our proposed method with some experiments such as tumbling operation by two autonomous robots.

Dissipative Structure Network for Collective Autonomy: Spatial Decomposition of Robotic Group

Abstract: Distributed autonomous system is not autonomous only because it is composed of autonomous agents. As long as the system requires constraints from outside to maintain the functionality, it is not autonomous, while composing agents are autonomous and intelligent. We consider meaning of autonomy for multi-agent system, and propose a concept of collective autonomy. In analogy to an autopoiesis in perusing collective autonomy, several characteristics are presented. We propose Dissipative Structure Network (DSN) as the framework for the collective autonomy. The importance of spatial self-organization is stressed through the discussion. As a first step for the DSN, spatial decomposition mechanism is considered. We analytically discuss a mechanism and conditions for spatial patterning and implement to the simulation based on the analitical results.

Strategy of perception and temporal representation of beliefs

Abstract: An autonomous system uses sensors in order to update an uncertain representation of its environment, which must remain well-grounded with regards to the risks and the constraints of its mission. The choice of a framework for the representation of beliefs which is adapted to deal with both time and uncertainty is a crucial point. A perception strategy should be founded on an evaluation of the relevance of the beliefs of the system in order to collect the most useful information at the most opportune time. This paper addresses the problem of taking time and ignorance into account in the representation of the uncertain beliefs of the system about the world. The paper proposes a well-adapted approach to the design of a perception strategy for an autonomous surveillance system in a changing environment together with initial results of simulations.

A multiple-sequence generator based on inverted nonlinear autonomous machines

Abstract: A new multiple-sequence generator scheme to generate a set of deterministic ordered sequence of patterns followed by random patterns is presented in this paper. This scheme is based on an inverted nonlinear autonomous machine which utilizes a two-dimension-like LFSR with nonlinear inverters. A systematic procedure is also presented to obtain the autonomous machine which is more regular in the structure and utilizes less hardware. The generated deterministic sequence of patterns, which may have ordered and repeated patterns, and the random patterns are applicable to sequential circuit testing.

Autonomous decentralization system

Abstract: PURPOSE: To easily adjust parameters for organization even when the number of subsystems is large by adjusting the ratio of the computation rate of plural subsystems and the transmission rate of computation results, and centralizing and managing them. CONSTITUTION: The subsystems 11 are connected by a network 12 to constitute the autonomous system. Delay generating devices 21 provided between the network 12 and individual subsystems 11 adjust the ratios of the computation rates of the subsystems and the transmission rates of computation results between the subsystems as parameter adjustments for self-organization. Here, a delay time management device 22 supplies a delay time for the centralized management of the self-organization adjustments of the autonomous decentralization system supplied from a user or external system 23 to the respective delay generating devices 21 through the network 20, and the delay generating devices 21 when sending the computation results from the subsystems 11 to the network 12 delays the transmitting operation according to the delay time.

Reliability of local error control algorithms for initial value ordinary differential equations.

Abstract: Users of software for initial value systems of ordinary differential equations are typically asked to specify a tolerance parameter that indicates, in a somewhat vague sense, the level of accuracy required. In practice, the tolerance parameter is used to drive an error control and meshpoint selection process, but the precise details are transparent to the user. With this scenario, given also some way of measuring the quality of the solution, it is highly appropriate to ask how the behavior of the algorithm depends on the tolerance parameter. Questions of this type have been afforded surprisingly little attention in the literature, despite their obvious relevance. However, positive results have been established in many key areas, and the study of adaptive error control, particularly for long-term simulations, has become an active research area. In this paper a range of results is surveyed. In each case the main aim is to provide guarantees about the behavior of complete algorithms: time-stepping formulas combined with error control procedures that adaptively vary the stepsize. Further, the results are couched in terms of the tolerance parameter, since this is the quantity over which the user has control. We cover classical finite-time error bounds and also more modern work on long-term nonlinear dynamics.

Simultaneous human and autonomous control with constrained human action

Abstract: An approach to the control of an autonomous process with human supervision is presented. The process is modelled as a discrete event system which allows for human intervention. For effective control, the autonomous system should control most of the process, with the human only interfering in an unmodelled situation. This shared control must therefore allow the human to influence the autonomous system as well as allowing the autonomous system to "influence" the human. The autonomous process can influence the human by constraining the human input. We present a method by which these constraints are not only used to restrict the human but also to control the autonomous process. The validity of the proposed method of using constraints to generate velocity control commands as well as restricting the human input is demonstrated by experiments. The experiments are implemented using the Eshed Scorbot VII.

Extracting frequency of an autonomous system by harmonic balance

Abstract: Some considerations on initial partitioning the circuit within harmonic balance analysis are presented. Instead of linear and nonlinear, it is divided into resistive and reactive parts. Following the procedure presented, frequency as a parameter appears no more than once inside each equation, and most of the unknowns are expressed explicitly. The former is advantageous when examining an autonomous system, and the latter enables a simple numerical process. The method proposed is illustrated by an example.

Fuzzy Logic for Autonomous Spacecraft Attitude Control Failure

Abstract: Spacecraft failures occur in many ways. In the worst case they can even provoke the total loss of the mission. Some failures can seriously affect the attitude control system performance. In the majority of cases, attitude control failure recovery is a laborious manual process. The paper presents the advantages of fuzzy control methodology applied to autonomous system failure recovery. The fuzzy controller is especially useful when the plant is difficult to model mathematically, e.g., after a failure has occurred. The paper discusses the sequence of events in the implementation of the fuzzy controller: acquisition and capture of the knowledge of an experienced human spacecraft controller, risk analysis, elaboration of the rules data base, construction of the inference engine, and the final implementation in a microprocessor.

Study on Asymptotic Strategy-Making in Multiple Autonomous Robot System

Abstract: A method of distributed strategymaking in multiple autonomous system is presented in this paper. Every robot in the system has several tactics to be selected, and set of probabilities to select tactics are called “strategy”. The algorithm to make strategy in this paper is iteration of four parts as follows: (1) select and try a certain tactic by means of the strategy, (2) get payoff value for applied tactic from environment, (3) revise the estimated payoff value of tactics, (4) revise the strategy by using (3) . Effectiveness of the proposed method is verified by path selecting simulation of multiple mobile robots. Convergence to optimal solution in the proposed method is discussed by using pay-off matrices in game theory.

Local Perception Maps and Navigation for a Mobile Robot

Abstract: This paper describes a mobile robotics system that was implemented and is capable of building instantaneous representations of the free space available, and use those representations to perform navigation. The free space representations are done by means of perception maps specially designed to hold and combine ultrasonic data. The maps are built by neural networks appropriately trained to minimise undesired ranging errors due to specular reflections; that is achieved by taking advantage of the redundancy of sensorial data. The concept of local navigation is developed as a new navigation approach, and is based on full independence on the environment, relying purely on sensorial perception. Local motion is generated according to simple generic behaviour descriptions: the local navigation strategies. The system, which was implemented, guarantees a safe local motion throughout the environment, requiring no a priori information nor any pre-defined path to follow. An adequate navigation architecture integrates the local navigation module within a framework of other several modules for more complete navigation tasks. The results obtained are quite promising in pointing the way to an autonomous system.

Extracting frequency of an autonomous system by harmonic balance

Abstract: Some considerations on initial partitioningthe circuit within harmonic balance analysis are presented Instead of linear and nonlinear, it is divided into resistive and reactive parts Following the procedure presented, frequency as a parameter appears no more than once inside each equation, and most of the unknowns are expressed explicitly The former is advantageous when examining an autonomous system, and the latter enables a simple numerical process The method proposed is illustrated by an example