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Mechanism enables robot to change tools on end of arm. Actuated by motion of robot: requires no additional electrical or pneumatic energy to make or break connection between tool and wrist at end of arm. Includes three basic subassemblies: wrist interface plate attached to robot arm at wrist, tool interface plate attached to tool, and holster. Separate tool interface plate and holster provided for each tool robot uses.
Proposed truss joint designed for assembly by robot. Requires only simple motions of end effector of robot, tolerates relatively large initial misalignment of strut, and assembled with little feedback. Principal features of joint: expanding collet latches it to node ball and collet expanded by flexible drive shaft operated by robot. Developed for Space Station, also used for robotic construction in hazardous or undersea locations.
A robot for space applications will be required to complete a variety of tasks in an uncertain, harsh environment. This fact presents unusual and highly difficult challenges to ensuring the safety of astronauts and keeping the equipment they depend on from becoming damaged. The systematic approach being taken to control hazards that could result from introducing robotics technology in the space environment is described. First, system safety management and engineering principles, techniques, and requirements are discussed as they relate to Shuttle payload design and operation in general. The concepts of hazard, hazard category, and hazard control, as defined by the Shuttle payload safety requirements, is explained. Next, it is shown how these general safety management and engineering principles are being implemented on an actual project. An example is presented of a hazard control system for controlling one of the hazards identified for the Development Test Flight (DTF-1) of NASA's Flight Telerobotic Servicer, a teleoperated space robot. How these schemes can be applied to terrestrial robots is discussed as well. The same software monitoring and control approach will insure the safe operation of a slave manipulator under teleoperated or autonomous control in undersea, nuclear, or manufacturing applications where the manipulator is working in the vicinity of humans or critical hardware.
A low friction, object guidance, and gripping finger device for a robotic end effector on a robotic arm is disclosed, having a pair of robotic fingers each having a finger shaft slideably located on a gripper housing attached to the end effector. Each of the robotic fingers has a roller housing attached to the finger shaft. The roller housing has a ball bearing mounted centering roller located at the center, and a pair of ball bearing mounted clamping rollers located on either side of the centering roller. The object has a recess to engage the centering roller and a number of seating ramps for engaging the clamping rollers. The centering roller acts to position and hold the object symmetrically about the centering roller with respect to the X axis and the clamping rollers act to position and hold the object with respect to the Y and Z axis.
Robots operating in the microgravity environment of an orbiting laboratory should be capable of manipulating payloads such that the motion of the robot does not disturb adjacent experiments. The current results of a NASA Lewis Research Center technology program to develop smooth, reaction-compensated manipulation based on both mechanism technology and trajectory planning strategies are present. Experimental validation of methods to reduce robot base reactions through the use of redundant degrees of freedom is discussed. Merits of smooth operation roller-driven robot joints for microgravity manipulators are also reviewed.
An adaptive position control scheme for manipulators possessing either kinematic or actuator redundancy is presented. The controller is developed by considering the end-effector position control problem and redundancy resolution problem separately. The end-effector position control problem is solved by using an adaptive scheme to generate the Cartesian-space control input required to track the desired end-effector position trajectory; this control problem is nonredundant even for redundant robots. The Cartesian-space position controller is derived using a model reference adaptive control (MRAC) approach, and does not require knowledge of the complex robot dynamic model or parameter values for the robot or the payload. As a result, the scheme is applicable to both open-chain and closed-chain robots, and is computationally efficient for on-line implementations.
The Marshall Space Flight Center is developing welding and robotics technologies to improve manufacturing of space hardware. Commercial robots are used for these development programs, but they are teamed with advanced sensors, process controls, and computer simulation to form highly productive manufacturing systems. Application of welding robotics and controls to structural welding for the space shuttle and space station Freedom programs is addressed. Several advanced welding process sensors under development for application to space hardware are discussed, as well as the application of commercial robotic simulation software to provide offline programming.
A two-arm free-flying robot has been constructed to study thrusterless locomotion in space. This is accomplished by pushing off or landing on a large structure in a coordinated two-arm maneuver. A new control method, called system momentum control, allows the robot to follow desired momentum trajectories and thus leap or crawl from one structure to another. The robot floats on an air-cushion, simulating in two dimensions the drag-free zero-g environment of space. The control paradigm has been verified experimentally by commanding the robot to push off a bar with both arms, rotate 180 degrees, and catch itself on another bar.
The areas of application for space robots in the Space Exploration Initiative (SEI) are examined by reviewing the roles of SEI supervised robots particularly with planet-surface systems (PSSs). Treatment is given to both teleoperated conventional robot systems and autonomous intelligent systems for comparison in terms of safety, reliability, and productivity. Two development stages are proposed including one with a robotic actor, human observer, and a human supervisor and a second in which a closed-loop control and monitoring system is established. The use of remote control is shown to require robustness, self-calibration and -diagnosis, adjustable autonomy, and multitask capability. The requirements of intelligent control are also listed so that the PSSs of the SEI can be used to enable surface exploration, local-resource utilization potential, and reductions of human tasks.
Special-purpose sets of equipment, packaged in identical modules with identical interconnecting mechanisms, attached to or detached from each other by specially designed robot, according to proposal. Two-arm walking robot connects and disconnects modules, operating either autonomously or under remote supervision. Robot walks along row of connected modules by grasping successive attachment subassemblies in hand-over-hand motion. Intended application for facility or station in outer space; robot reconfiguration scheme makes it unnecessary for astronauts to venture outside spacecraft or space station. Concept proves useful on Earth in assembly, disassembly, or reconfiguration of equipment in such hostile environments as underwater, near active volcanoes, or in industrial process streams.
Report presents additional information about robotic system described in "Robotic Gripper With Force Control And Optical Sensors" (MFS-28537). "Flexible Agricultural Robotics Manipulator System" (FARMS) serves as prototype of robotic systems intended to enhance productivities of agricultural assembly-line-type facilities in large commercial greenhouses and nurseries.
A satellite floating space is diagnosed with a telerobot attached performing maintenance or replacement tasks. This research included three objectives. The first objective was to generate intelligent path planning for a robot to move around a satellite. The second objective was to diagnose possible faulty scenarios in the satellite. The third objective included two tasks. The first task was to combine intelligent path planning with diagnosis. The second task was to build an interface between the combined intelligent system with Robosim. The ability of a robot to deal with unexpected scenarios is particularly important in space since the situation could be different from time to time so that the telerobot must be capable of detecting that the situation has changed and the necessity may exist to alter its behavior based on the new situation. The feature of allowing human-in-the-loop is also very important in space. In some extreme cases, the situation is beyond the capability of a robot so our research project allows the human to override the decision of a robot.
An integrated dexterous robotic system was developed as a testbed to evaluate various robotics technologies for advanced space applications. The system configuration consisted of a Utah/MIT Dexterous Hand, a PUMA 562 arm, a stereo vision system, and a multiprocessing computer control system. In addition to these major subsystems, a proximity sensing system was integrated with the Utah/MIT Hand to provide capability for non-contact sensing of a nearby object. A high-speed fiber-optic link was used to transmit digitized proximity sensor signals back to the multiprocessing control system. The hardware system was designed to satisfy the requirements for both teleoperated and autonomous operations. The software system was designed to exploit parallel processing capability, pursue functional modularity, incorporate artificial intelligence for robot control, allow high-level symbolic robot commands, maximize reusable code, minimize compilation requirements, and provide an interactive application development and debugging environment for the end users. An overview is presented of the system hardware and software configurations, and implementation is discussed of subsystem functions.
As the need for robotic manipulation in fields such as manufacturing and telerobotics increases, so does the need for effective methods of controlling the interaction forces between the manipulators and their environment. Position Accommodation (PA) is a form of robotic force control where the nominal path of the manipulator is modified in response to forces and torques sensed at the tool-tip of the manipulator. The response is tailored such that the manipulator emulates a mechanical impedance to its environment. PA falls under the category of position-based robotic force control, and may be viewed as a form of Impedance Control. The practical implementations are explored of PA into an 18 degree-of-freedom robotic testbed consisting of two PUMA 560 arms mounted on two 3 DOF positioning platforms. Single and dual-arm architectures for PA are presented along with some experimental results. Characteristics of position-based force control are discussed, along with some of the limitations of PA.
The need for automated plasma welding was identified in the early stages of the Space Station Freedom Program (SSFP) because it requires approximately 1.3 miles of welding for assembly. As a result of the Variable Polarity Plasma Arc Welding (VPPAW) process's ability to make virtually defect-free welds in aluminum, it was chosen to fulfill the welding needs. Space Station Freedom will be constructed of 2219 aluminum utilizing the computer controlled VPPAW process. The 'Node Radial Docking Port', with it's saddle shaped weld path, has a constantly changing surface angle over 360 deg of the 282 inch weld. The automated robotic VPPAW process requires eight-axes of motion (six-axes of robot and two-axes of positioner movement). The robot control system is programmed to maintain Torch Center Point (TCP) orientation perpendicular to the part while the part positioner is tilted and rotated to maintain the vertical up orientation as required by the VPPAW process. The combined speed of the robot and the positioner are integrated to maintain a constant speed between the part and the torch. A laser-based vision sensor system has also been integrated to track the seam and map the surface of the profile during welding.
A report concerning technology transfer in the area of robotics is presented in vugraph form. The following topics are discussed: definition of technology innovation and tech-transfer; concepts relevant for understanding tech-transfer; models advanced to portray tech-transfer process; factors identified as promoting tech-transfer; factors identified as impeding tech-transfer; what important roles do individuals fulfill in tech-transfer; federal infrastructure for promoting tech-transfer; federal infrastructure for promoting tech-transfer; robotic technology evolution; robotic technology transferred; and recommendations for successful robotics tech-transfer.
Robotic systems are finding increasing use in space applications. Many of these devices are going to be operational on board the Space Station Freedom. Fault tolerance has been deemed necessary because of the criticality of the tasks and the inaccessibility of the systems to maintenance and repair. Design for fault tolerance in manipulator systems is an area within robotics that is without precedence in the literature. In this paper, we will attempt to lay down the foundations for such a technology. Design for fault tolerance demands new and special approaches to design, often at considerable variance from established design practices. These design aspects, together with reliability evaluation and modeling tools, are presented. Mechanical architectures that employ protective redundancies at many levels and have a modular architecture are then studied in detail. Once a mechanical architecture for fault tolerance has been derived, the chronological stages of operational fault tolerance are investigated. Failure detection, isolation, and estimation methods are surveyed, and such methods for robot sensors and actuators are derived. Failure recovery methods are also presented for each of the protective layers of redundancy. Failure recovery tactics often span all of the layers of a control hierarchy. Thus, a unified framework for decision-making and control, which orchestrates both the nominal redundancy management tasks and the failure management tasks, has been derived. The well-developed field of fault-tolerant computers is studied next, and some design principles relevant to the design of fault-tolerant robot controllers are abstracted. Conclusions are drawn, and a road map for the design of fault-tolerant manipulator systems is laid out with recommendations for a 10 DOF arm with dual actuators at each joint.
A robotic manipulator, DTF-1, developed as part of the Flight Telerobotic Servicer (FTS) project at Goddard Space Flight Center is discussed focusing on the technical, operational, and safety requirements. The DTF-1 system design, which is based on the manipulator, gripper, cameras, computer, and an operator control station incorporates the fundamental building blocks of the original FTS, the end product of which was to have been a light-weight, dexterous telerobotic device. For the first time in the history of NASA, space technology and robotics were combined to find new and unique solutions to the demanding requirements of flying a sophisticated robotic manipulator in space. DTF-1 is considered to be the prototype for all future development in space robotics.