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Control problems in autonomous life support systems, CELSS candidate species, maximum grain yield, plant growth, waste management, air pollution, and mineral separation are discussed.
The Space Station crew will be a critical resource for economical operation of science and commercial payloads. Core station housekeeping and maintenance functions should be provided in a manner that requires a minimum of crew interaction. This paper outlines a prospective functional architecture for allocation of autonomous and automated control of these functions and discusses implementation issues arising from safety of manned operations, integration test requirements, and evolution of future station capabilities.
The Manned Space Station (MSS) involves NASA, and other countries, in the operation, maintenance and expansion of a permanent space facility. The extensive use of automation and robotics will advance those fields, and experimentation will be carried out in scientific and potentially commercial projects. The MSS will provide a base for astronomical observations, spacecraft assembly, refurbishment and repair, transportation intersection, staging for interplanetary exploration, and storage. Finally, MSS operations will be performed semi-autonomously from ground control. Phase B analysis is nearing completion, and precedes hardware development. Studies are being performed on generic advanced technologies which can reliably and flexibly be incorporated into the MSS, such as attitude control and stabilization, power, thermal, environmental and life support control, auxiliary propulsion, data management, etc. Guidelines are also being formulated regarding the areas of participation by other nations.
The Space Station is being defined as a multi-purpose facility with emphasis in the following areas: scientific and technology research laboratory; permanent observatory; spacecraft servicing facility; construction and assembly facility; manufacturing facility; transportation node; and staging base for future space endeavors. The Station complex, in its initial operating capability configuration, includes a continuously habitable manned element, a polar orbiting unmanned platform, and a second unmanned platform co-orbiting with the manned element. All elements are dependent on the Space Transportation System (STS) for initial placement on-orbit and for subsequent logistical services. The manned element will be designed for long duration operations with systems maintainable on-orbit and operationally autonomous from ground control. A major feature of the Station will be its adaptability to evolutionary technology upgrades; and the Space Station, as a system, is to be designed for maximum ease of use by its users.
The program 'Spacecraft 2000' has the objective to identify critical, high-payoff, potential spacecraft technologies, taking into account the formulation, advocation, and the management of the requisite technology development programs. This program represents a joint NASA-industry program. The technology areas addressed by 'Spacecraft 2000' are related to spacecraft power/energy storage, thermal control/thermal management, power management and distribution, autonomous operation-control, on-board system integration, spacecraft environmental interactions, secondary propulsion, communications technologies, a total system response approach, and system-subsystem technology verification. The expected benefits of a development of advanced technologies include decreased spacecraft bus system weights, decreased mission costs, increased reliability/lifetimes, and increased operational flexibility.
The Spacecraft 2000 program has been conceived by NASA with the objective to maintain the U.S. in a strong technical position in the space arena. The program is to involve a cooperative NASA/industry effort with long-range technology development aims. The technology areas addressed are related to spacecraft power, spacecraft energy storage, power management and distribution, autonomous operation-control, onboard systems integration, secondary propulsion, communications technologies, and systems/subsystems technology verification. Aspects of Spacecraft 2000 interactions with industry are discussed, taking into account visitations of NASA personnel to selected industrial concerns, most critical concerns (general), major technical concern, technology drivers for future spacecraft power systems, technology considerations for secondary propulsion, and questions of commercialization. Plans related to a Spacecraft 2000 program formulation are also considered.
A Second Tracking and Data Relay Satellite System (TDRSS) Ground Terminal (STGT) is envisioned as the next step in providing expanded support service for data transmission between spaceborne NASA and related missions, including Space Station and the earth-based user community. This need for expanded support service is projected to exist during the early to late 1990's time frame. This concept description reflects the current NASA requirements for a life-cycle cost-effective acquisition of the STGT. The significant features of this STGT configuration include autonomous subsystems, decentralized control processes and modular functional implementation. These features are expected to reduce acquisition risk and provide efficient manpower utilization during the operational years.
In order to accommodate the increasing number of computerized subsystems aboard today's more fuel efficient aircraft, the Boeing Co. has developed the DATAC (Digital Autonomous Terminal Access Control) bus to minimize the need for point-to-point wiring to interconnect these various systems, thereby reducing total aircraft weight and maintaining an economical flight configuration. The DATAC bus is essentially a local area network providing interconnections for any of the flight management and control systems aboard the aircraft. The task of developing a Bus Monitor Unit was broken down into four subtasks: (1) providing a hardware interface between the DATAC bus and the Z8000-based microcomputer system to be used as the bus monitor; (2) establishing a communication link between the Z8000 system and a CP/M-based computer system; (3) generation of data reduction and display software to output data to the console device; and (4) development of a DATAC Terminal Simulator to facilitate testing of the hardware and software which transfer data between the DATAC's bus and the operator's console in a near real time environment. These tasks are briefly discussed.
Much of commonsense knowledge about the real world is in the form of procedures or sequences of actions for achieving particular goals. In this paper, a formalism is presented for representing such knowledge using the notion of process. A declarative semantics for the representation is given, which allows a user to state facts about the effects of doing things in the problem domain of interest. An operational semantics is also provided, which shows how this knowledge can be used to achieve particular goals or to form intentions regarding their achievement. Given both semantics, the formalism additionally serves as an executable specification language suitable for constructing complex systems. A system based on this formalism is described, and examples involving control of an autonomous robot and fault diagnosis for NASA's Space Shuttle are provided.
A detailed simulation of a dc inductor resonant driver and receiver is used to demonstrate the transient characteristics of a 20 kHz resonant power system during fault and overload conditions. The simulated system consists of a dc inductor resonant inverter (driver), a 50-meter transmission cable, and a dc inductor resonant receiver load. Of particular interest are the driver and receiver performance during fault and overload conditions and on the recovery characteristics following removal of the fault. The information gained from these studies sets the stage for further work in fault identification and autonomous power system control.
Telerobotic operations, whether under autonomous or teleoperated control, require a much more sophisticated safety system than that needed for most industrial applications. Industrial robots generally perform very repetitive tasks in a controlled, static environment. The safety system in that case can be as simple as shutting down the robot if a human enters the work area, or even simply building a cage around the work space. Telerobotic operations, however, will take place in a dynamic, sometimes unpredictable environment, and will involve complicated and perhaps unrehearsed manipulations. This creates a much greater potential for damage to the robot or objects in its vicinity. The Procedural Safety System (PSS) collects data from external sensors and the robot, then processes it through an expert system shell to determine whether an unsafe condition or potential unsafe condition exists. Unsafe conditions could include exceeding velocity, acceleration, torque, or joint limits, imminent collision, exceeding temperature limits, and robot or sensor component failure. If a threat to safety exists, the operator is warned. If the threat is serious enough, the robot is halted. The PSS, therefore, uses expert system technology to enhance safety thus reducing operator work load, allowing him/her to focus on performing the task at hand without the distraction of worrying about violating safety criteria.
Project Longshot, an exercise in the Advanced Design Program for Space, had as its destination Alpha Centauri, the closest star system to our own solar system. Alpha Centauri, a trinary star system, is 4.34 light years from earth. Although Project Longshot is impossible based on existing technologies, areas that require further investigation in order to make this feat possible are identified. Three areas where advances in technology are needed are propulsion, data processing for autonomous command and control functions, and reliability. Propulsion, possibly by antimatter annihilation; navigation and navigation aids; reliable hardware and instruments; artificial intelligence to eliminate the need for command telemetry; laser communication; and a reliable, compact, and lightweight power system that converts energy efficiently and reliably present major challenges. Project Longshot promises exciting advances in science and technology and new information concerning the universe.
Recently JPL was asked by SDIO to analyze and develop a preliminary design for a deep-space mission to fly by two near-Earth asteroids, Eros and Toutatis. As a part of this mission, JPL was also asked to assess the feasibility of deploying a probe on approach to impact Toutatis. This mission is a candidate for SDIO's Clementine 2. SDIO's motivations were to provide further demonstrations of precision, autonomous navigation for controlling the flight paths of both a spacecraft and a probe. NASA's interest in this mission is driven by the opportunity to obtain the first close-up images and other scientific measurements from a spacecraft of two important near-Earth objects. For Toutatis this is especially important since it was observed and imaged extensively just last Dec. using Earth-based radar; Clementine 2 will provide the opportunity to corroborate the radar data and validate the ultimate potential of the radar technique. Scientifically, the probe impact at Toutatis will allow the acquisition of data pertaining to the dynamic strength of surface material and data on the properties of the regolith and on stratification below the surface, and will potentially allow the measurement of thermal diffusivity between the interior and the surface. These determinations will be accomplished by means of high-resolution imagery of the impact crater and its surroundings in visible, ultraviolet, and infrared wave bands from the spacecraft flying by some 30 min. after the probe strike. In addition, if the spacecraft can be equipped with a lightweight mass spectrometer and dust analyzer, the potential also exists to measure the particle sizes and distribution and the composition of the eject a cloud. This mission is planned to be launched in Jul. 1995, with the Eros encounter on 13 Mar. 1996, and the Toutatis flyby on 4 Oct. 1996, some 440 days after launch.
Application of expert system concepts to a breadboard Mars oxygen processor unit have been studied and tested. The research was directed toward developing the methodology required to enable autonomous operation and control of these simple chemical processors at Mars. Failure detection and isolation was the key area of concern, and schemes using forward chaining, backward chaining, knowledge-based expert systems, and rule-based expert systems were examined. Tests and simulations were conducted that investigated self-health checkout, emergency shutdown, and fault detection, in addition to normal control activities. A dynamic system model was developed using the Bond-Graph technique. The dynamic model agreed well with tests involving sudden reductions in throughput. However, nonlinear effects were observed during tests that incorporated step function increases in flow variables. Computer simulations and experiments have demonstrated the feasibility of expert systems utilizing rule-based diagnosis and decision-making algorithms.
The WALRUS is a wheeled articulating land rover that will provide Ames Research Center with a reliable, autonomous vehicle for demonstrating and evaluating advanced technologies. The vehicle is one component of the Ames Research Center's on-going Human Exploration Demonstration Project. Ames Research Center requested a system capable of traversing a broad spectrum of surface types and obstacles. In addition, this vehicle must have an autonomous navigation and control system on board and its own source of power. The resulting design is a rover that articulates in two planes of motion to allow for increased mobility and stability. The rover is driven by six conical shaped aluminum wheels, each with an independent, internally coupled motor. Mounted on the rover are two housings and a removable remote control system. In the housings, the motor controller board, tilt sensor, navigation circuitry, and QED board are mounted. Finally, the rover's motors and electronics are powered by thirty C-cell rechargeable batteries, which are located in the rover wheels and recharged by a specially designed battery charger.
The Naval Command Control and Ocean Surveillance Center (NCCOSC) has developed an architecture to provide coordinated control of multiple autonomous vehicles from a single host console. The multiple robot host architecture (MRHA) is a distributed multiprocessing system that can be expanded to accommodate as many as 32 robots. The initial application will employ eight Cybermotion K2A Navmaster robots configured as remote security platforms in support of the Mobile Detection Assessment and Response System (MDARS) Program. This paper discusses developmental testing of the MRHA in an operational warehouse environment, with two actual and four simulated robotic platforms.
The footward shift of blood volume and compensatory autonomic reflex responses initiated during the assumption of the upright posture in terrestrial gravity is a common feature in humans. When regular exposure to upright posture is removed, the headward redistribution of blood induces numerous physiological adaptations which compromise this normal response and the development of low blood pressure upon standing (orthostatic hypotension) can ensue. Such microgravity conditions can be produced by prolonged exposure to spaceflight or prolonged bed rest. Since the reduction of blood and plasma volume during exposure to microgravity has been associated with orthostatic instability following spaceflight and bed rest, it has been a reasonable assumption that hypovolemia may be a primary contributing factor to the development of orthostatic hypotension. This view was supported by the observation that the attempt to restore vascular volume in astronauts by drinking saline solutions just prior to re-entry had proven effective in reducing orthostatic instability after spaceflights of short duration. However, as the duration of spaceflight lengthens, orthostatic instability persists despite fluid loading procedures, suggesting that mechanisms other than hypovolemia may contribute to orthostatic hypotension following prolonged exposure to microgravity conditions. Recent evidence has been generated from spaceflight and groundbase experiments that supports the notion that changes in autonomic baroreflexes that control cardiac and vascular responses during orthostatic challenges may be affected by longer periods of microgravity exposure and can contribute to postflight orthostatic instability.
The Fluid Combustion Facility (FCF) Project and the Power Technology Division at the NASA Glenn Research Center (GRC) at Lewis Field in Cleveland, OH along with the Sundstrand Corporation in Rockford, IL are jointly developing an Electrical Power Converter Unit (EPCU) for the Fluid Combustion Facility to be flown on the International Space Station (ISS). The FCF facility experiment contains three racks: A core rack, a combustion rack, and a fluids rack. The EPCU will be used as the power interface to the ISS 120V(sub dc) power distribution system by each FCF experiment rack which requires 28V(sub dc). The EPCU is a modular design which contains three 120V(sub dc)-to-28V(sub dc) full-bridge, power converters rated at 1 kW(sub e) each bus transferring input relays and solid-state, current-limiting input switches, 48 current-limiting, solid-state, output switches; and control and telemetry hardware. The EPCU has all controls required to autonomously share load demand between the power feeds and--if absolutely necessary--shed loads. The EPCU, which maximizes the usage of allocated ISS power and minimizes loss of power to loads, can be paralleled with other EPCUs. This paper overviews the electrical design and operating characteristics of the EPCU and presents test data from the breadboard design.