Lunar rovers and local positioning system

Telerobotic rovers equipped with adequate actuators and sensors are clearly necessary for extraterrestrial construction. They will be employed as substitutes for humans, to perform jobs like surveying, sensing, signaling, manipulating, and the handling of small materials. Important design criteria for these rovers include versatility and robustness. They must be easily programmed and reprogrammed to perform a wide variety of different functions, and they must be robust so that construction work will not be jeopardized by parts failures. The key qualities and functions necessary for these rovers to achieve the required versatility and robustness are modularity, redundancy, and coordination. Three robotic rovers are being built by CSC as a test bed to implement the concepts of modularity and coordination. The specific goal of the design and construction of these robots is to demonstrate the software modularity and multirobot control algorithms required for the physical manipulation of constructible elements. Each rover consists of a transporter platform, bus manager, simple manipulator, and positioning receivers. These robots will be controlled from a central control console via a radio-frequency local area network (LAN). To date, one prototype transporter platform frame was built with batteries, motors, a prototype single-motor controller, and two prototype internal LAN boards. Software modules were developed in C language for monitor functions, i/o, and parallel port usage in each computer board. Also completed are the fabrication of half of the required number of computer boards, the procurement of 19.2 Kbaud RF modems for inter-robot communications, and the simulation of processing requirements for positioning receivers. In addition to the robotic platform, the fabrication of a local positioning system based on infrared signals is nearly completed. This positioning system will make the rovers into a moving reference system capable of performing site surveys. In addition, a four degree mechanical manipulator especially suited for coordinated teleoperation was conceptually designed and is currently being analyzed. This manipulator will be integrated into the rovers as their end effector. Twenty internal LAN cards fabricated by a commercial firm are being used, a prototype manipulator and a range finder for a positioning system were built, a prototype two-motor controller was designed, and one of the robots is performing its first telerobotic motion. In addition, the robots' internal LAN's were coordinated and tested, hardware design upgrades based on fabrication and fit experience were completed, and the positioning system is running. The rover system is able to perform simple tasks such as sensing and signaling; coordination systems which allow construction tasks to begin were established, and soon coordinated teams of robots in the laboratory will be able to manipulate common objects

Interaction dynamics and control for orbital assembly

The topics are presented in viewgraph form and include the following: dynamics and control problems of joining structures in orbit; spring-and-mass models; and a simple example

Paper Session I-A - In-Space Welding Visions & Realities

This paper establishes the value of having an in-space welding capability and identifies its applications, both near-term for Shuttle-Spacelab missions and Space Station Freedom, and longer-term for the First Lunar Outpost and Manned Mission to Mars. The leading candidate technologies, consisting of Electron Beam, Gas Tungsten Arc, Plasma Arc, and Laser Beam, are examined against the criteria for an in-space welding system. Research and development work to date, striving to achieve an in-space welding capability, is reviewed. Finally, a series of strategic NASA flight experiments is discussed as the remaining development required for achieving a complete in-space welding capability, which can fully serve the Space Exploration Initiative. This paper summarizes the visions and realities associated with in-space welding

Nonlinear input-output systems

Necessary and sufficient conditions that the nonlinear system dot-x = f(x) + ug(x) and y = h(x) be locally feedback equivalent to the controllable linear system dot-xi = A xi + bv and y = C xi having linear output are found. Only the single input and single output case is considered, however, the results generalize to multi-input and multi-output systems

Economic efficiency of coordinated multilateral trades in electricity markets

This paper presents economic efficiency evaluation of electricity markets operating on the basis of a coordinated multilateral trading concept. The evaluation accounts for the overall costs of power generation, network losses, and system and unit constraints. We assume a non-collusive oligopolistic competition. An iterative Cournot model is used to characterize the competitive behavior of suppliers. A supplier maximizes the profit of each of his generating units while taking rivals\u27 generation as given. Time span is over multiple hours. This leads to a mixed integer non-linear programming problem. We use the augmented Lagrangian approach to solve iteratively for globally optimal schedules. An IEEE 24-bus, 8-supplier, and 17-customer test system is used for illustration. The results show that such a market at times of light demands exhibits little market power, and at times of large demands exhibits a great deal of market power. This contrasts with the PCMI and HHI concentration measures, which give fixed measurement values of market power. The results of two-year (730 round) market simulations show a range of deadweight efficiency loss between 0.9 and 6% compared to that of PoolCo which results in a range between 0.5 and 10% for the same test case

Economic efficiency of pool coordinated electricity markets

This paper presents economic efficiency evaluation of pool coordinated electricity markets. The evaluation accounts for the overall cost of power generation, network losses and costs, and various operational constraints. We assume a non-collusive oligopolistic competition. An iterative supply function model is used to characterize the competitive behavior of suppliers. A social welfare function is defined for PoolCo market that operates over multiple hours time span. This leads to a mixed-integer non-linear programming problem. An Augmented Lagrangian approach is used to solve iteratively for global optimal operation schedules (i.e. power generation, load, and price for each bus node) while considering constraints of different sorts. An IEEE 24-bus, eight-supplier, 17-customer test system is used for illustration. The results show deflection of electricity prices from the marginal costs of power generation. The results of 2-year (730 round) market simulations show a range of deadweight efficiency loss between 0.

Augmented Lagrangian approach to hydro-thermal scheduling

This paper presents an augmented Lagrangian approach to hydro-thermal scheduling. It adds to the standard Lagrangian function a quadratic penalty function which associates generation-load balance, spinning reserve and emission constraints. This makes better commitment solutions that may exist in a dual gap very likely reachable by adjusting penalty and Lagrangian multipliers parameters. The advantage of this approach over Lagrangian relaxation and augmented Lagrangian with only the generation-load balance constraint penalized is discussed. An IEEE test system is used for illustration. Our results show that the augmented Lagrangian with all coupling constraints penalized can provide better scheduling results as it can detect in-between-hours shutdown of some units, earlier shutdown, and/or later startup of some other units