Mechanical & Fluid Systems

User’s Guide for ENSAERO

A report summarizes the development, applications, and procedures for use of ENSAERO, a computer program for simulating aeroelastic phenomena (e.g., wing flutter) of aircraft and spacecraft. ENSAERO computes aeroelastic responses by simultaneously numerically integrating Euler and/or Navier-Stokes equations of airflow and modal finite-element equations of structural dynamics on aeroelastically adaptive dynamic grids. The numerical integrations are performed by time-accurate finitedifference schemes. The report describes the coupling of the governing equations of flow with the governing equations of structural dynamics and with equations that describe active controls and thermal loads. The criteria and procedures for generation of zonal adaptive grids are discussed. Results of simulations performed by use of ENSAERO are presented for examples that involve, variously, steady or unsteady flow about rigid full aircraft or elastic wing/body assemblies.

This work was done by Guru P. Guruswamy of Ames Research Center.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Ames Research Center, (650) 604-5104. Refer to ARC-14239.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computer simulation, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Aerodynamics, Aircraft, Spacecraft

Minimally Actuated Hopping Robot

This robot can traverse terrain that is too cluttered for wheeled vehicles.

A small robot that travels by hopping has been built and tested. This is a prototype of hopping robots that would carry video cameras and possibly other sensory devices and that are under consideration for use in exploring cluttered, unpredictable terrain on distant planets. On Earth, robots like this one might have value for entertainment and civilian and military reconnoitering of hazardous areas.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Springs, Optics, Sensors and actuators, Optics, Sensors and actuators, Robotics

Mobile Robot With Foveal Machine Vision

The Foveal Extra-Vehicular Activity Helper-Retriever (FEVAHR) is a mobile robot that features a hierarchical foveal machine-vision system (HFMV). The FEVAHR is a prototype of future robots that could detect, recognize, track, and pursue objects and avoid obstacles while operating autonomously, controlled by human operators via natural-language commands, or both. The design of the FEVAHR merges high- and low-level anthropomorphic designs. The high-level anthropomorphism is represented by (1) the Semantic Network Processing System (SNePS) software for semantic representation of information, inference, and natural-language interaction, and (2) the Grounded Layered Architecture With Integrated Reasoning (GLAIR) software, which acts as an interface between SNePS on the one hand and subconscious processes and sensors on the other hand. The low-level anthropomorphism is represented by the HFMV hardware and software, which exploit the neuromorphic multiacuity sensing and information processing prevalent among vertebrates to achieve an effective visual information-acquisition power that is higher than that of uniform-acuity active vision. SNePS, GLAIR, and HFMV work in unison, each driving and being controlled by the others, to accomplish physical tasks with constrained resources and maintain a high level perception necessary for autonomous interaction with humans.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Architecture, Computer software / hardware, Computer software and hardware, Imaging, Imaging and visualization, Sensors and actuators, Architecture, Computer software / hardware, Computer software and hardware, Imaging, Imaging and visualization, Sensors and actuators, Human machine interface (HMI), Robotics

Rotary Tool and Retractable Foot for Walking Robot

One end effector alternates between two roles.

A mechanism has been developed to serve as an end effector for one of the legs of the Legged Excursion Mechanical Utility Robot (LEMUR) — a walking robot designed for demon- strating robotic cap- abilities for maintenance and repair. [The LEMUR was described in “Six-Legged Experimental Robot” (NPO-20897), NASA Tech Briefs, Vol. 25, No. 12 (December 2001), page 58.] Through controlled actuation of this mechanism, the tip of the leg can become either (1) a foot for stable support during walking or (2) the robotic equivalent of a simple hand tool — a ballend hexagonal driver for a standard hexagonal-socket machine screw. More specifically, the foot can be extended to enable walking, or can be retracted to enable cameras that are parts of the robot to view the insertion of the tool bit in a socket. Retraction of the foot also enables the tool to be used in confined spaces in which the foot cannot fit.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Maintenance, Repair and Service Operations, Maintenance, repair, and service operations, Tools and equipment, Robotics, Fittings, Mountings

Minirovers as Test Beds for Robotic and Sensor-Web Concepts

These units would be highly functional, robust, repairable, and reprogrammable.

The figure depicts a proposed reconfigurable miniature exploratory robotic vehicle (mini- rover) that would serve as a versatile prototype in the development of exploratory robots and “smart”-sensor systems that contain them. For example, minirovers could serve as nodes of sensor webs — networks of spatially distributed autonomous cooperating robots — that have been contemplated for use in exploring large areas of terrain. [The concept of such networks was reported in more detail in “Sensor Webs” (NPO- 20616), NASA Tech Briefs, Vol. 23, No. 10 (October 1999), page 80.]

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Neural networks, Sensors and actuators, Neural networks, Sensors and actuators, Product development, Robotics

Mechanism for Docking a Miniature Spacecraft

This report discusses a proposed docking mechanism to be located in a small hangar on the outside of the International Space Station (ISS). The mechanism would enable docking of a miniature robotic spacecraft (or free flyer) that would carry a video camera and would operate in the vicinity of the ISS. The docking mechanism would include, among other things, (1) an electromagnet for actuation, (2) electrical connectors for transferring data to and from the free flyer and recharging the freeflyer power system, and (3) a quick-disconnect (QD) coupling for recharging a supply of gaseous N2. Once the free flyer had maneuvered into approximate docking alignment, an electromagnet in the mechanism would attract a ferromagnetic plate on the free flyer strongly enough to pull the free flyer in from a distance of as much as several inches (≈10 cm). The mechanism would include surfaces that would mate with surfaces on the free flyer to correct any misalignment as the free flyer was pulled in. Once docked, the free flyer would be held in place by either spring-loaded cam locks or the QD coupling itself. Data, power, and N2 can then be transferred to the vehicle.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Charging stations, Optics, Charging stations, Optics, Robotics, Entry, descent, and landing, Spacecraft

Emergency Tether-Deployment-and-Recoil-Mitigating Systems

A report describes an emergency tether-deployment (ETD) system designed to minimize the harm caused by two events that can occur during deployment of tethered payloads from a space shuttle in orbit. One such event is snagging of the tether during payout while the payload is near the shuttle, causing rebound of the shuttle and payload toward each, thus possibly causing a collision. The other event is recoil of a tether that must be cut while it is under tension. If not suppressed, the recoil can cause the tether to become tangled around the shuttle. The ETD system includes a tether wound on a spool in a standard pattern that minimizes friction during payout, plus a rotating-arm mechanism that prevents snagging. The ETD system can be either (1) used as a primary deployment system or (2) activated automatically through breakage of a tether tiedown in the event of a snag or when the payload is at a safe distance from the shuttle. To suppress recoil, a core of solder is inserted along part of the length of the tether. When a wave of recoil reaches this part, the solder absorbs most of the recoil energy.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Finite element analysis, Welding, Crash prevention, Spacecraft

Cylindrical Shape-Memory Rotary/Linear Actuator

A shape-memory ribbon is wrapped around a cylinder to build up length.

A compact actuator generates rotary or linear motion with a large torque or force, respectively. The original version of this actuator is designed to pull a wedge that, until pulled, prevents retraction of the proposed extended nose landing gear of the space shuttle. The original version is also required to fit into a volume that is severely limited by the size of the landing-gear assembly. The basic actuator design could be adapted to other applications in which there are requirements for compact, large-force actuators with similar geometries.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Landing gear, Sensors and actuators, Sensors and actuators, Spacecraft

Formation Alignment of Multiple Autonomous Vehicles

Alignment is achieved by use of lasers, optical sensors, and rule-based controls.

A table-top experiment on formation alignment of three air-levitated robotic vehicles has been performed to demonstrate the feasibility of a more general concept of controlling multiple robotic vehicles to make them move in specified positions and orientations with respect to each other. The original intended application of the concept is in the control of multiple spacecraft flying in formation, as described in “Synchronizing Attitudes and Maneuvers of Multiple Spacecraft” (NPO-20569) on page 64 in this issue of NASA Tech Briefs. In principle, the concept could also be applied on Earth to control formation flying of aircraft or to coordinate the motions of multiple robots, land vehicles, or ships.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Steer-by-wire, Sensors and actuators, Sensors and actuators, Vehicle to vehicle (V2V), Autonomous vehicles, Unmanned aerial vehicles, Vehicle handling

Microfabricated Flow Controllers and Pressure Regulators

Efforts are underway to develop microfabricated flow controllers and pressure regulators that contain as few discrete components as feasible and that are cheaper, more robust, and orders of magnitude smaller than are currently commercially available devices that have similar capabilities. The developmental devices are designed to interact with electronic sensing and control circuits that include microprocessors that, in turn, communicate with host computers of digital feedback control systems. An example of the prototype devices constructed thus far is a hybrid device that includes a flow sensor, a valve containing a TiNi-alloy microribbon shape-memory actuator, and a temperature sensor, with wire-bonded leads for connection to electronic circuits. Windows™-based software for interaction between host computers and the microprocessors associated with these devices has been written. Contemplated further development efforts would be devoted to advancing from the concept of a flow controller on a ceramic substrate to that of a flow controller on an assembly of two or more semiconductor chips. In principle, fabrication on a semiconductor chip could be accomplished without need to assemble discrete components.

Posted in: Briefs, Mechanical Components, Mechanics, Electronic control systems, Electronic control systems, Product development

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