2,079 research outputs found

    Multiple cooperating manipulators: The case of kinematically redundant arms

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    Existing work concerning two or more manipulators simultaneously grasping and transferring a common load is continued and extended. Specifically considered is the case of one or more arms being kinematically redundant. Some existing results in the modeling and control of single redundant arms and multiple manipulators are reviewed. The cooperating situation is modeled in terms of a set of coordinates representing object motion and internal object squeezing. Nominal trajectories in these coordinates are produced via actuator load distribution algorithms introduced previously. A controller is developed to track these desired object trajectories while making use of the kinematic redundancy to additionally aid the cooperation and coordination of the system. It is shown how the existence of kinematic redundancy within the system may be used to enhance the degree of cooperation achievable

    Octopus-Inspired Grasp-Synergies for Continuum Manipulators

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    Human operation of continuum ‚Äúcontinuous-backbone‚ÄĚ manipulators remains difficult, because of both the complex kinematics of these manipulators and the need to coordinate their many degrees of freedom. We present a novel synergy-based approach for operator interfaces, by introducing a series of octopus-arm inspired grasp-synergies. These grasp-synergies automatically coordinate the degrees of freedom of the continuum manipulator, allowing an operator to perform kinematically complex grasping motions through simple and intuitive joystick inputs. This effectively reduces the complexity of operation and allows the operator to devote more of his attention to higher-level concerns (e.g. goal, environment). We demonstrate the grasp-synergies interface design in both simulation and hardware using the nine degree of freedom Octarm continuum manipulator

    The Use of Fault Trees for the Design of Robots for Hazardous Environments

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    This paper addresses the application of fault trees to the analysis of robot manipulator reliability and fault tolerance. Although a common and useful tool in other applications, fault trees have only recently been applied to robots. In addition, most of the fault tree analyses in robotics have focused on qualitative, rather than quantitative, analysis. Robotic manipulators present some special problems, due to the complex and strongly coupled nature of their subsystems, and also their wild response to subsystem failures. Additionally, there is a lack of reliability data for robots and their subsystems. There has traditionally been little emphasis on fault tolerance in the design of industrial robots, and data regarding operational robot failures is relatively scarce.National Science FoundationSandia National LaboratoryNAS

    Robot Reliability Through Fuzzy Markov Models

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    In the past few years, new applications of robots have increased the importance of robotic reliability and fault tolerance. Standard approaches of reliability engineering rely on the probability model, which is often inappropriate for this task due to a lack of sufficient probabilistic information during the design and prototyping phases. Fuzzy logic offers an alternative to the probability paradigm, possibility, that is much more appropriate to reliability in the robotic context.National Science FoundationNASAOffice of Naval ResearchSandia National Laborator

    Fault Detection and Fault Tolerance in Robotics

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    Robots are used in inaccessible or hazardous environments in order to alleviate some of the time, cost and risk involved in preparing men to endure these conditions. In order to perform their expected tasks, the robots are often quite complex, thus increasing their potential for failures. If men must be sent into these environments to repair each component failure in the robot, the advantages of using the robot are quickly lost. Fault tolerant robots are needed which can effectively cope with failures and continue their tasks until repairs can be realistically scheduled. Before fault tolerant capabilities can be created, methods of detecting and pinpointing failures must be perfected. This paper develops a basic fault tree analysis of a robot in order to obtain a better understanding of where failures can occur and how they contribute to other failures in the robot. The resulting failure flow chart can also be used to analyze the resiliency of the robot in the presence of specific faults. By simulating robot failures and fault detection schemes, the problems involved in detecting failures for robots are explored in more depth. Future work will extend the analyses done in this paper to enhance Trick, a robotic simulation testbed, with fault tolerant capabilities in an expert system package.National Science FoundationMitre Corporation Graduate FellowshipNSF Graduate Fellowshi

    Review of the occupational health and safety of Britain’s ethnic minorities

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    This report sets out an evidence-based review on work-related health and safety issues relating to black and minority ethnic groups. Data included available statistical materials and a systematic review of published research and practice-based reports. UK South Asians are generally under-represented within the most hazardous occupational groups. They have lower accident rates overall, while Black Caribbean workers rates are similar to the general population; Bangladeshi and Chinese workers report lowest workplace injury rates UK South Asian people exhibit higher levels of limiting long-term illness (LLI) and self reported poor health than the general population while Black Africans and Chinese report lower levels. Ethnic minority workers with LLI are more likely than whites to withdraw from the workforce, or to experience lower wage rates. Some of these findings conflict with evidence of differentials from USA, Europe and Australasia, but there is a dearth of effective primary research or reliable monitoring data from UK sources. There remains a need to improve monitoring and data collection relating to black and ethnic minority populations and migrant workers. Suggestions are made relating to workshops on occupational health promotion programmes for ethnic minorities, and ethnic minority health and safety 'Beacon' sites

    Risk and Fault Tolerance Analysis for Robotics and Manufacturing

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    This paper describes a novel method for analyzing, within one framework, several important types of risk associated with robotics and manufacturing applications. We will build on the established technique of Fault Tree Analysis to analyze the risk/benefits of the physical process, and extend the concept to build a dual structure for environmental costs/benefits. In addition, our framework includes the ability to perform financial cost-benefit analyses.NASA Graduate FellowshipNational Science Foundatio

    Fault Residual Generation via Nonlinear Analytical Redundancy

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    Fault detection is critical in many applications, and analytical redundancy (AR) has been the key underlying tool for many approaches to fault detection. However, the conventional AR approach is formally limited to linear systems. In this brief, we exploit the structure of nonlinear geometric control theory to derive a new nonlinear analytical redundancy (NLAR) framework. The NLAR technique is applicable to affine systems and is seen to be a natural extension of linear AR. The NLAR structure introduced in this brief is tailored toward practical applications. Via an example of robot fault detection, we show the considerable improvement in performance generated by the approach compared with the traditional linear AR approach

    Robotic Fault Detection Using Nonlinear Analytical Redundancy

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    In this paper we discuss the application of our recently developed nonlinear analytical redundancy (NLAR) fault detection technique to a two-degree of freedom robot manipulator. NLAR extends the traditional linear AR technique to derive the maximum possible number of fault detection tests into the continuous nonlinear domain. The ability to handle nonlinear systems vastly expands the accuracy and viable applications of the AR technique. The effectiveness of the approach is demonstrated through an example.NASANational Science Foundatio
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