Space robotics: Recent accomplishments and opportunities for future research

The Langley Guidance, Navigation, and Control Technical Committee (GNCTC) was one of six technical committees created in 1991 by the Chief Scientist, Dr. Michael F. Card. During the kickoff meeting Dr. Card charged the chairmen to: (1) establish a cross-Center committee; (2) support at least one workshop in a selected discipline; and (3) prepare a technical paper on recent accomplishments in the discipline and on opportunities for future research. The Guidance, Navigation, and Control Committee was formed and selected for focus on the discipline of Space robotics. This report is a summary of the committee's assessment of recent accomplishments and opportunities for future research. The report is organized as follows. First is an overview of the data sources used by the committee. Next is a description of technical needs identified by the committee followed by recent accomplishments. Opportunities for future research ends the main body of the report. It includes the primary recommendation of the committee that NASA establish a national space facility for the development of space automation and robotics, one element of which is a telerobotic research platform in space. References 1 and 2 are the proceedings of two workshops sponsored by the committee during its June 1991, through May 1992 term. The focus of the committee for the June 1992 - May 1993 term will be to further define to the recommended platform in space and to add an additional discipline which includes aircraft related GN&C issues. To the latter end members performing aircraft related research will be added to the committee. (A preliminary assessment of future opportunities in aircraft-related GN&C research has been included as appendix A.

Control strategy for cooperating disparate manipulators

To manipulate large payloads typical of space construction, the concept of a small arm mounted on the end of a large arm is introduced. The main purposes of such a configuration are to increase the structural stiffness of the robot by bracing against or locking to a stationary frame, and to maintain a firm position constraint between the robot's base and workpieces by grasping them. Possible topologies for a combination of disparate large and small arms are discussed, and kinematics, dynamics, controls, and coordination of the two arms, especially when they brace at the tip of the small arm, are developed. The feasibility and improvement in performance are verified, not only with analytical work and simulation results but also with experiments on the existing arrangement Robotic Arm Large and Flexible and Small Articulated Manipulator

Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

In der vorliegenden Dissertation wird die Simulation der inversen Dynamik unteraktuierter Mehrkörpersysteme behandelt. Insbesondere werden Steuerungsprobleme der Bahnverfolgung für differentiell flache unteraktuierte Systeme untersucht. Mit Hilfe von Servobindungen werden die Steuerungsprobleme der Bahnverfolgung für unteraktuierte Systeme formuliert. Die betrachteten Probleme werden unteraktuierte Servobindungsprobleme genannt. Minimalkoordinaten, abhängige oder redundante Koordinaten werden zur Formulierung unteraktuierter Servobindungsprobleme verwendet. Die Formulierung ergibt differential-algebraische Gleichungen mit hohem Index. Die diskrete Nullraum-Methode ermöglicht den Übergang von redundanten Koordinaten zu Minimalkoordinaten. Da die numerische Lösung der differential-algebraischen Gleichungen mit hohem Index anspruchsvoll ist und die flachheitsbasierte analytische Lösung für komplizierte unteraktuierte Systeme nicht praktikabel ist, werden Methoden zur Indexreduktion vor der direkten Zeitdiskretisierung eingesetzt. Eine spezielle Projektionsmethode wird angewendet, um den Index von fünf auf drei zu reduzieren. Die Methode erfordert die Berechnung von Projektionsmatrizen, die in der redundanten Koordinaten Formulierung konstant und in der Minimalkoordinaten Formulierung zeitabhängig sind. Eine neue Methode, Indexreduktion durch minimale Erweiterung genannt, wird in dieser Dissertation entwickelt und für Servobindungsprobleme unteraktuierter Systeme verwendet. Die beiden Methoden werden auf repräsentative numerische Beispiele angewandt. Insbesondere wird schon gezeigt, dass sich die neu entwickelte Indexreduktionsmethode zur Lösung involvierter Probleme eignet, die bislang mit der Projektionsmethode nicht gelöst werden konnten

A hyper-redundant manipulator

“Hyper-redundant” manipulators have a very large number of actuatable degrees of freedom. The benefits of hyper-redundant robots include the ability to avoid obstacles, increased robustness with respect to mechanical failure, and the ability to perform new forms of robot locomotion and grasping. The authors examine hyper-redundant manipulator design criteria and the physical implementation of one particular design: a variable geometry truss

Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

The present work deals with the inverse dynamics simulation of underactuated multibody systems. In particular, the study focuses on solving trajectory tracking control problems of differentially flat underactuated systems. The use of servo constraints provides an approach to formulate trajectory tracking control problems of underacutated systems, which are also called underactuated servo constraint problems

An inverse kinematics algorithm for a highly redundant variable-geometry-truss manipulator

A new class of robotic arm consists of a periodic sequence of truss substructures, each of which has several variable-length members. Such variable-geometry-truss manipulator (VGTMs) are inherently highly redundant and promise a significant increase in dexterity over conventional anthropomorphic manipulators. This dexterity may be exploited for both obstacle avoidance and controlled deployment in complex workspaces. The inverse kinematics problem for such unorthodox manipulators, however, becomes complex because of the large number of degrees of freedom, and conventional solutions to the inverse kinematics problem become inefficient because of the high degree of redundancy. A solution is presented to this problem based on a spline-like reference curve for the manipulator's shape. Such an approach has a number of advantages: (1) direct, intuitive manipulation of shape; (2) reduced calculation time; and (3) direct control over the effective degree of redundancy of the manipulator. Furthermore, although the algorithm was developed primarily for variable-geometry-truss manipulators, it is general enough for application to a number of manipulator designs

An intelligent, free-flying robot

The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base

Online Deflection Compensation of a Flexible Hydraulic Loader Crane Using Neural Networks and Pressure Feedback

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Development of Motion Control Systems for Hydraulically Actuated Cranes with Hanging Loads

Automation has been used in industrial processes for several decades to increase efficiency and safety. Tasks that are either dull, dangerous, or dirty can often be performed by machines in a reliable manner. This may provide a reduced risk to human life, and will typically give a lower economic cost. Industrial robots are a prime example of this, and have seen extensive use in the automotive industry and manufacturing plants. While these machines have been employed in a wide variety of industries, heavy duty lifting and handling equipment such as hydraulic cranes have typically been manually operated. This provides an opportunity to investigate and develop control systems to push lifting equipment towards the same level of automation found in the aforementioned industries. The use of winches and hanging loads on cranes give a set of challenges not typically found on robots, which requires careful consideration of both the safety aspect and precision of the pendulum-like motion. Another difference from industrial robots is the type of actuation systems used. While robots use electric motors, the cranes discussed in this thesis use hydraulic cylinders. As such, the dynamics of the machines and the control system designmay differ significantly. In addition, hydraulic cranes may experience significant deflection when lifting heavy loads, arising from both structural flexibility and the compressibility of the hydraulic fluid. The work presented in this thesis focuses on motion control of hydraulically actuated cranes. Motion control is an important topic when developing automation systems, as moving from one position to another is a common requirement for automated lifting operations. A novel path controller operating in actuator space is developed, which takes advantage of the load-independent flow control valves typically found on hydraulically actuated cranes. By operating in actuator space the motion of each cylinder is inherently minimized. To counteract the pendulum-like motion of the hanging payload, a novel anti-swing controller is developed and experimentally verified. The anti-swing controller is able to suppress the motion from the hanging load to increase safety and precision. To tackle the challenges associated with the flexibility of the crane, a deflection compensator is developed and experimentally verified. The deflection compensator is able to counteract both the static deflection due to gravity and dynamic de ection due to motion. Further, the topic of adaptive feedforward control of pressure compensated cylinders has been investigated. A novel adaptive differential controller has been developed and experimentally verified, which adapts to system uncertainties in both directions of motion. Finally, the use of electro-hydrostatic actuators for motion control of cranes has been investigated using numerical time domain simulations. A novel concept is proposed and investigated using simulations.publishedVersio

Investigaciones en las operaciones de transferencia de carga offshore, desafíos, desarrollos y nuevas fronteras

Currently, offshore operations are considered activities with high impact on the economy, which standsin direct relation to the products of great importance and value for diverse economic sectors. Thus, itbecomes necessary to implement new technologies that make the manipulation of these products fasterand easier. In this work, the authors introduce the problem in offshore cargo transfer operations. Thisproblem involves different kinds of areas: logistics, dynamics, and control are some of them. The authorspresent an approach for the last two. In the dynamic problem is presented a study on the dynamics of asuspended load connected to a crane via a mechanism with two prismatic degrees of freedom. The studiesshow the complex large-amplitude motion of the load given the visibly nonlinear behavior of the ship.Therefore, the development of a fuzzy controller was necessary to decrease oscillations and position theload in one definitive point of interest. The work presents the test results, demonstrating that this typeof manipulator in combination with an effective control strategy allows for the reduction of oscillationsin offshore activities.En la actualidad, las operaciones en alta mar se consideran actividades con alto impacto en la economía, lo cual se encuentra en relación directa con los productos de gran importancia y valor para diversos sectores económicos. Así entonces, se hace necesario implementar nuevas tecnologías que permitan más rápida y fácil manipulación de estos productos. En este trabajo, los autores presentan el problema en operaciones de transferencia de carga en alta mar. Este problema involucra diferentes tipos de áreas: logística, dinámica y control, son algunos de ellos. Los autores presentan un acercamiento para las últimas dos. En el problema de dinámica se presenta un estudio sobre la dinámica de una carga suspendida conectada a una grúa mediante un mecanismo con dos grados prismáticos de libertad. Los estudios demuestran el movimiento complejo de gran amplitud de la carga dada el comportamiento visiblemente no-lineal de la embarcación. Entonces, el desarrollo de un controlador de lógica difusa fue necesario para disminuir las oscilacionesy posicionar la carga en un punto de interés definitivo. El trabajo presenta los resultados de pruebas, demostrando que este tipo de manipulador en combinación con una estrategia efectiva de control permite la reducción de oscilaciones en actividades en alta mar