Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Research and technology

Significant research and technology activities at the Johnson Space Center (JSC) during Fiscal Year 1990 are reviewed. Research in human factors engineering, the Space Shuttle, the Space Station Freedom, space exploration and related topics are covered

Performance evaluation and development of a synchro-drive mobile robot

The work described in this thesis is concerned with the performance of the mechanical system of a mobile robot that is capable of omnidirectional motion. The main attribute of such mobile robots is that their direction of motion is independent of chassis orientation. This attribute endows them with exceptional manoeuvrability, but it is also found to pose substantial problems by changing the level of accuracy and stability of the robot as its direction of travel changes. The main objective of the research is to conduct a detailed evaluation of the performance of a mobile robot which is capable of omnidirectional movement achieved by means of a synchronized all-wheel steering and all-wheel drive (Synchro-drive) technique. The objective is met by comparing the synchro-drive method with other configurations used for mobile robots, by comparing different designs of the synchro-drive method and by analyzing synchro-drive mechanical behaviour in response to drive and steering inputs. A kinematic model of the synchro-drive arrangement is formulated and this is used to analyze different designs and to assess the limits of the control variables beyond which a Synchro-Drive Mobile Robot (SDMR) operation will become unstable. A new version of the synchro-drive arrangement was developed and was used to perform extensive practical testing in order to determine factors affecting positional accuracy and the trajectory actually executed by the mobile robot. The analysis of the boundaries of the control space revealed the limits on acceleration which may be allowed by the robot's control system for it to remain stable. It also showed that the acceleration limits depend on the angle between the wheel heading and the chassis orientation, which is defined as the robot's posture. Practical experimentation identified the major influences on robot accuracy and also related the form, magnitude and direction of these errors to the robot's posture. The experiments revealed that the errors were due partly to aspects of the design itself and partly due to inevitable errors in the complete mechanical system. A continuous position error correction method is proposed which uses experimental data as the basis for correction. Correction quantities vary with posture, and the method uses a modification to the steering rate to minimize trajectory error. Overall the study reveals the factors which must be considered to enable the potential of the synchro-drive mobile robot to be fully realized

The Federal Conference on Intelligent Processing Equipment

Research and development projects involving intelligent processing equipment within the following U.S. agencies are addressed: Department of Agriculture, Department of Commerce, Department of Energy, Department of Defense, Environmental Protection Agency, Federal Emergency Management Agency, NASA, National Institutes of Health, and the National Science Foundation

Proceedings of the NASA Conference on Space Telerobotics, volume 1

The theme of the Conference was man-machine collaboration in space. Topics addressed include: redundant manipulators; man-machine systems; telerobot architecture; remote sensing and planning; navigation; neural networks; fundamental AI research; and reasoning under uncertainty

Task-space dynamic control of underwater robots

This thesis is concerned with the control aspects for underwater tasks performed by marine robots. The mathematical models of an underwater vehicle and an underwater vehicle with an onboard manipulator are discussed together with their associated properties. The task-space regulation problem for an underwater vehicle is addressed where the desired target is commonly specified as a point. A new control technique is proposed where the multiple targets are defined as sub-regions. A fuzzy technique is used to handle these multiple sub-region criteria effectively. Due to the unknown gravitational and buoyancy forces, an adaptive term is adopted in the proposed controller. An extension to a region boundary-based control law is then proposed for an underwater vehicle to illustrate the flexibility of the region reaching concept. In this novel controller, a desired target is defined as a boundary instead of a point or region. For a mapping of the uncertain restoring forces, a least-squares estimation algorithm and the inverse Jacobian matrix are utilised in the adaptive control law. To realise a new tracking control concept for a kinematically redundant robot, subregion tracking control schemes with a sub-tasks objective are developed for a UVMS. In this concept, the desired objective is specified as a moving sub-region instead of a trajectory. In addition, due to the system being kinematically redundant, the controller also enables the use of self-motion of the system to perform sub-tasks (drag minimisation, obstacle avoidance, manipulability and avoidance of mechanical joint limits)

Whole-hand input

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 1992.Includes bibliographical references (p. 219-233).by David Joel Sturman.Ph.D

Conference on Intelligent Robotics in Field, Factory, Service, and Space (CIRFFSS 1994), volume 1

The AIAA/NASA Conference on Intelligent Robotics in Field, Factory, Service, and Space (CIRFFSS '94) was originally proposed because of the strong belief that America's problems of global economic competitiveness and job creation and preservation can partly be solved by the use of intelligent robotics, which are also required for human space exploration missions. Individual sessions addressed nuclear industry, agile manufacturing, security/building monitoring, on-orbit applications, vision and sensing technologies, situated control and low-level control, robotic systems architecture, environmental restoration and waste management, robotic remanufacturing, and healthcare applications

Space station systems: A bibliography with indexes (supplement 2)

This bibliography lists 904 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1, 1985 and December 31, 1985. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems. The coverage includes documents that define major systems and subsystems, servicing and support requirements, procedures and operations, and missions for the current and future space station