Gotowa bibliografia na temat „Rigid Formation Flying”

This paper investigates robust adaptive coordinated attitude tracking issue for spacecraft formation flying system with nonrigid and rigid spacecraft under directed communication topology, where the inertia and external disturbances are totally unknown time-varying. A novel robust adaptive attitude tracking coordination control algorithm is proposed to regulate the attitude of the spacecraft to a common time-varying reference state. The control law is robust adaptive against external disturbances and time-varying inertia under the directed topology. In addition, a dynamic adjustment function is designed to limit the amplitude of control torque. Simulation results validate the effectiveness of the presented control algorithm and better control performance when compared with an adaptive control scheme.

One of the important applications of the space tethered system is formation flying. To satisfy the requirement for interferometry of ground targets by remote-sensing satellites, a new type of tethered solar sail spacecraft has been proposed in recent research. The replacement of subsatellites of conventional tethered satellite systems with solar sail spacecraft allows for a special formation configuration in which the main satellite is in sun-synchronous orbit and the subsolar sail is in displaced orbit. If the solar sail is at the appropriate attitude, the main satellite and the solar sail spacecraft connected by metal tethers could move side by side, hence this formation system is called transverse formation. The relative baseline of this transverse formation system is perpendicular to the ground trajectory of the satellite, effectively solving the problem that the relative baseline of conventional orbital formations varies in a trigonometric cycle. Researchers on the past ignored the mass and elasticity of the tether, and considered the tether just a constraint in the model system. Since the solar sail is generally quite light compared to the other components of the system, the model inaccuracy caused by ignoring the mass of the tether on the dynamic model and control is extremely obvious. This paper investigates the relative dynamics and control of a proposed system during the deployment process with the mass of the tether. Two precise models of satellite-sail systems are established. One is based on the dumbbell model with the mass tether for the tethered satellite system, and the other is on the basis of the beads model of a tethered satellite system. The rigid one is for control design and the flexible one is for dynamic simulation. It is concluded that the length of the tether and attitude angle of the transverse formation configuration can be decoupled and controlled separately. On the basis of the models, a length rate and LQR control law is developed and the control of the deployment and retrieval process of the tethered solar sail system is investigated. Numerical simulations are performed to verify the accuracy of the conclusions.

To ensure the stability of flight, the butterfly needs to flap its wings and simultaneously move its main body to achieve all kinds of flying motion, such as taking off, hovering, or reverse flight. The high-speed camera is used to record the swing of the abdomen, the movement of the wings, and the pitch angle of the body for butterflies during their free flight; the comprehensive biokinetic observations show that the butterfly’s wings and body are coupled in various flight states. The swing of the abdomen and the flap of the fore wing affect the pitch motion significantly. For theoretical analysis of the butterfly flight, a three-dimensional multi-rigid butterfly model based on real butterfly dimension is established, and the aerodynamic of the butterfly flight is simulated and analyzed via computational fluid dynamics methods to obtain an optimal kinematic model of butterfly forward flight. Moreover, the formation and development of three-dimensional vortex structures in the forward flight are also presented. The detailed structures of vortices and their dynamic behavior show that the wing’s flap and the abdominal swing play a key role in reorienting and correcting the “clap and peel” mechanism, and the force generation mechanisms are evaluated. The research indicates that longitudinal flight performance is mainly related to the kinematic parameters of the wing and body, and it can lead to the development of butterfly-inspired flapping wing air vehicles.

I remember the first time I saw a dead body. I spawned just before dawn; around me engines were clattering into life, the dim silhouettes of tanks beginning to move out in a steady grinding rumble. I could dimly make out a few other people, the anonymity of their shadowy outlines belied by the names hanging over their heads in a comforting blue. Suddenly, a stream of tracers arced across the sky; explosions sounded nearby, then closer still; a tank ahead of me stopped, turned sluggishly, and fired off a couple of rounds, rocking slightly against the recoil. The radio was filled with talk of Germans in the town, but I couldn’t even see the town. I ran toward what looked like the shattered hulk of a building and dived into what I hoped was a doorway. It was already occupied by another Tommy and together we waited for it to get lighter, listening to the rattle of machine guns, the sharp ping as shells ricocheted off steel, the sickening, indescribable, but immediately recognisable sound when they didn’t. Eventually, the other soldier moved out, but I waited for the sun to peek over the nearby hills. Once I was able to see where I was going, I made straight for the command post on the edge of town, and came across a group of allied soldiers standing in a circle. In the centre of the circle lay a dead German soldier, face up. “Well I’ll be damned,” I said aloud; no one else said anything, and the body abruptly faded. I remember the first time I killed someone. I had barely got the Spit V up to 4000 feet when out of the corner of my eye I caught a glimpse of something below me. I dropped the left wing and saw a Stuka making a bee-line for the base. I made a hash of the turn, almost stalling, but he obviously had no idea I was there. I saddled-up on his six, dropping down low to avoid fire from his gunner, and opened up on him. I must have hit him at perfect convergence because he disintegrated, pieces of dismembered airframe raining down on the field below. I circled the field, putting all my concentration into making the landing that would make the kill count, then switched off the engine and sat in the cockpit for a moment, heart pounding. As you can tell, I’ve been in the wars lately. The first example is drawn from the launch of Cornered Rat Software’s WWII Online: Blitzkrieg (2001) while the second is based on a short stint playing Warbirds 3 (2002). Both games are examples of one of the most interesting recent developments in computer and video gaming: the increasing popularity and range of Massively Multiplayer Online Games (MMOGs); other notable examples of historical combat simulation MMOGs include HiTech Creations Aces High (2002) and Jaleco Entertainment’s Fighter Ace 3.5 (2002). For a variety of technical reasons, most popular multiplayer games—particularly first-person shooter (FPS) games such as Doom, Quake, and more recently Medal of Honor: Allied Assault (2002) and Return to Castle Wolfenstein (2001)—are played on player-organised servers that are usually limited to 32 or fewer players; terrain maps are small and rotated every couple of hours on average. MMOGs, by contrast, feature anywhere from hundreds to tens of thousands of players hosted on a handful of company-run servers. The shared virtual geography of these worlds is huge, extending across tens of thousands of square miles; these worlds are also persistent in that they respond dynamically to the actions of players and continue to do so while individual players are offline. As my opening anecdotes demonstrate, the experience of dealing and receiving virtual death is central to massively multiplayer simulations as it is to so many forms of computer games. Yet for an experience is that is so ubiquitous in computer games (and, some would say, even constitutes their experiential core) death is under-theorised. Mainstream culture tends to see computer and console game mayhem according to a rigid desensitisation argument: the experience of repeatedly killing other players online leads to a gradual erosion of the individual moral sense which makes players more likely to countenance killing people in the real world. Nowhere was this argument more in evidence that in the wake of the murder of fifteen students by Dylan Klebold and Eric Harris at Columbine High School in Littleton, Colorado on April 20, 1999. The discovery that the two boys were enthusiastic players of Id Software’s Doom and Quake resulted in an avalanche of hysterical news stories that charged computer games with a number of evils: eroding kids’ ability to distinguish fantasy from reality, encouraging them to imitate the actions represented in the games, and immuring them to the real-world consequences of violence. These claims were hardly new, and had in fact been directed at any number of violent popular entertainment genres over the years. What was new was the claim that the interactive nature of FPS games rendered them a form of simulated weapons training. What was also striking about the discourse surrounding the Littleton shooting was just how little the journalists covering the story knew about computer, console and arcade games. Nevertheless, their approach to the issue encouraged readers to see games as having real life analogs. Media discussion of the event also reinforced the notion of a connection with military training techniques, making extensive use of Lt. Col. (ret) David Grossman, a former Army ranger and psychologist who led the charge in claiming that games were “mass-murder simulators” (Gittrich, AA06). This controversy over the role of violent computer games in the Columbine murders is part of a larger cultural discourse that adopts the logical fallacy characteristic of moral panics: coincidence equals causation. Yet the impoverished discussion of online death and destruction is also due in no small measure to an entrenched hostility toward popular entertainment as a whole, a hostility that is evident even in the work of some academic critics who study popular culture. Andrew Darley, for example, argues that, never has the flattening of meaning or depth in the traditional aesthetic sense of these words been so pronounced as in the action-simulation genres of the computer game: here, aesthetic experience is tied directly to the purely sensational and allied to tests of physical dexterity (143). In this view, the repeated experience of death is merely a part of the overall texture of a form characterised not so much by narrative as by compulsive repetition. More generally, computer games are seen by many critics as the pernicious, paradigmatic instance of the colonisation of individual consciousness by cultural spectacle. According to this Frankfurt school-influenced critique (most frequently associated with the work of Guy Debord), spectacle serves both to mystify and pacify its audience: The more the technology opens up narrative possibilities, the less there is for the audience to do. [. . .]. When the spectacle conceals the practice of the artists who create it, it [announces]…itself as an expression of a universe beyond human volition and effort (Filewood 24). In supposedly sapping its audience’s critical faculties by bombarding them with a technological assault whose only purpose is to instantiate a deterministic worldview, spectacle is seen by its critics as exemplifying the work of capitalist ideology which teaches people not to question the world around them by establishing, in Althusser’s famous phrase, an “imaginary relationship of individuals to their real conditions of their existence” (162). The desensitisation thesis is thus part of a larger discourse that considers computer games paradoxically to be both escapist and as having real-world effects. With regard to online death, neo-Marxism meets neo-Freudianism: players are seen as hooked on the thrill not only of destroying others but also of self-destruction. Death is thus considered the terminus of all narrative possibility, and the participation of individuals in fantasy-death and mayhem is seen to lead inevitably to several kinds of cultural death: the death of “family values,” the death of community, the death of individual responsibility, and—given the characterisation of FPS games in particular as lacking in plot and characterisation—the death of storytelling. However, it is less productive to approach computer, arcade and console games as vehicles for force-feeding content with pre-determined cultural effects than it is to understand them as venues within and around which players stage a variety of theatrical performances. Thus even the bêtes noire of the mainstream media, first-person shooters, serve as vehicles for a variety of interactions ranging from the design of new sounds, graphics and levels, new “skins” for player characters, the formation of “tribes” or “clans” that fight and socialise together, and the creation of elaborate fan fictions. This idea that narrative does not simply “happen” within the immediate experience of playing the game, but is in fact produced by a dynamic interplay of interactions for which the game serves as a focus, also suggests a very different way of looking at the role of death online. Far from being the logical endpoint, the inevitable terminus of all narrative possibility, death becomes the indispensable starting point for narrative. In single-player games, for example, the existence of the simple “save game” function—differing from simply putting the game board to one side in that the save function allows the preservation of the game world in multiple temporal states—generates much of the narrative and dramatic range of computer games. Generally a player saves the game because he or she is facing an obstacle that may result in death; saving the game at that point allows the player to investigate alternatives. Thus, the ever-present possibility of death in the game world becomes the origin of all narratives based on forward investigation. In multiplayer and MMOG environments, where the players have no control over the save game state, it is nevertheless the possibility of a mode of forward projection that gives the experience its dramatic intensity. Flight simulation games in particular are notoriously difficult to master; the experience of serial death, therefore, becomes the necessary condition for honing your flying skills, trying out different tactics in a variety of combat situations, trying similar tactics in different aircraft, and so on. The experience of online death creates a powerful narrative impulse, and not only in those situations where death is serialised and guaranteed. A sizable proportion of the flight sim communities of both Warbirds and Aces High participate in specially designed scenario events that replicate a specific historical air combat event (the Battle of Britain, the Coral Sea, USAAF bomber operations in Europe, etc.) as closely as possible. What makes these scenarios so compelling for many players is that they are generally “one life” events: once the player is dead, they are out for the rest of the event and this creates an intense experience that is completely unlike flying in the everyday free-for-all arenas. The desensitisation thesis notwithstanding, there is little evidence that this narrative investment in death produces a more casual attitude toward real-life death amongst MMOG players. For example, when real-world death intrudes, simulation players often reach for the same rituals of comfort and acknowledgement that are employed offline. Recently, when an Aces High player died unexpectedly of heart failure at the age of 35, his squadron held an elaborate memorial event in his honor. Over a hundred players bailed out over an aerodrome—bailing out is the only way that a player in Aces High can acquire a virtual human body—and lined the edges of the runway as members of the dead player’s squad flew the missing man formation overhead (GrimmCAF). The insistence upon bodily presence in the context of a classic military ceremony marking irrecoverable absence suggests the way in which the connections between real and virtual worlds are experienced by players: as tensions, but also as points where identities are negotiated. This example does not seem to indicate that everyday familiarity with virtual death has dulled the players’ sensibilities to the sorrow and loss accompanying death in the real world. I began this article talking about death in simulation MMOGs for a number of reasons. In the first place, MMOGs are more commonly identified with their role-playing examples (MMORPGs) such as Ultima Online and Everquest, games that focus on virtual community-building and exploration in addition to violence and conquest. By contrast, simulation games tend to be seen as having more in common with first-person shooters like Quake, in the way in which they foreground the experience of serial death. Secondly, it is precisely the connection between simulation and death that makes games in general (as I demonstrated in relation to the media coverage of the Columbine murders) so problematic. In response, I would argue that one of the most interesting aspects of computer games recently has been the degree to which generic distinctions have been breaking down. MMORPGs, which had their roots in the Dungeons and Dragons gaming world, and the text-based world of MUDs and MOOs have since developed sophisticated third-person and even first-person representational styles to facilitate both peaceful character interactions and combat. Likewise, first-person shooters have begun to add role-playing elements (see, for example, Looking Glass Studios’ superb System Shock 2 (1999) or Lucasarts' Jedi Knight series). This trend has also been incorporated into simulation MMOGs: World War II Online includes a rudimentary set of character-tracking features, and Aces High has just announced a more ambitious expansion whose major focus will be the incorporation of role-playing elements. I feel that MMOGs in particular are all evolving towards a state that I would describe as “simulance:” simulations that, while they may be associated with a nominal representational reality, are increasingly about exploring the narrative possibilities, the mechanisms of theatrical engagement for self and community of simulation itself. Increasingly, none of the terms "simulation,” "role-playing" or indeed “game” quite captures the texture of these evolving experiences. In their complex engagement with both scripted and extemporaneous narrative, the players have more in common with period re-enactors; the immersive power of a well-designed flight simulator scenario produces a feeling in players akin to the “period rush” experienced by battlefield re-enactors, the frisson between awareness of playing a role and surrendering completely to the momentary power of its illusory reality. What troubles critics about simulations (and what also blinds them to the narrative complexity in other forms of computer games) is that they are indeed not simply examples of re-enactment —a re-staging of supposedly real events—but a generative form of narrative enactment. Computer games, particularly large-scale online games, provide a powerful set of theatrical tools with which players and player communities can help shape narratives and deepen their own narrative investment. Obviously, they are not isolated from real-world cultural factors that shape and constrain narrative possibility. However, we are starting to see the way in which the games use the idea of virtual death as the generative force for new storytelling frameworks based, in Filewood’s terms, on forward investigation. As games begin to move out of their incunabular state, they may contribute to the re-shaping of culture and consciousness, as other narrative platforms have done. Far from causing the downfall of civilisation, game-based narratives may bring with them a greater cultural awareness of simultaneous narrative possibility, of the past as sets of contingent phenomena, and a greater attention to practical, hands-on experimental problem-solving. It would be ironic, but no great surprise, if a form built around the creative possibilities inherent in serial death in fact made us more attentive to the rich alternative possibilities of living. Works Cited Aces High. HiTech Creations, 2002. http://www.bartleby.com/201/1.html Althusser, Louis. “Ideology and Ideological State Apparatuses (Notes Toward an Investigation).” Lenin and Philosophy and Other Essays. By Louis Althusser, trans. Ben Brewster. New York, 1971. 127-86. Barry, Ellen. “Games Feared as Youths’ Basic Training; Industry, Valued as Aid to Soldiers, on Defensive.” The Boston Globe 29 Apr 1999: A1. LexisNexis. Feb. 7, 2003. Cornered Rat Software. World War II Online: Blitzkrieg. Strategy First, 2001. http://www.wwiionline.com/ Darley, Andrew. Visual Digital Culture: Surface Play and Spectacle in New Media Genres. London: Routledge, 2000. Debord, Guy. The Society of the Spectacle. Donald Nicholson-Smith. New York: Zone Books, 1994. 1967. Der Derian, James. “The Simulation Syndrome: From War Games to Game Wars.” Social Text 8.2 (1990): 187-92. Filewood, Alan. “C:\Games\Dramaturgy: The Cybertheatre of Computer Games.” Canadian Theatre Review 81 (Winter 1994): 24-28. Gittrich, Greg. “Expert Differs with Kids over Video Game Effects.” The Denver Post 27 Apr 1999: AA-06. LexisNexis. Feb. 7 2003. GrimmCAF. “MojoCAF’s Memorial Flight.” Aces High BB, 13 Dec. 2002. http://www.hitechcreations.com/forums/sh... IEntertainment Network. Warbirds III. Simon and Schuster Interactive, 2002.http://www.totalsims.com/index.php?url=w... Jenkins, Henry, comp. “Voices from the Combat Zone: Game Grrlz Talk Back.” From Barbie to Mortal Kombat: Gender and Computer Games. Ed. Justine Cassell and Henry Jenkins. Cambridge, Massachusetts: MIT P, 1998. 328-41. Lieberman, Joseph I. “The Social Impact of Music Violence.” Statement Before the Governmental Affairs Committee Subcommittee on Oversight, 1997. http://www.senate.gov/member/ct/lieberma... Feb. 7 2003. Murray, Janet H. Hamlet on the Holodeck: The Future of Narrative in Cyberspace. New York: Free, 1997. Poole, Steven. Trigger Happy: Videogames and the Entertainment Revolution. New York: Arcade Publishing, 2000. Pyro. “AH2 FAQ.” Aces High BB, 29 Jan. 2003. Internet. http://www.hitechcreations.com/forums/sh... Feb. 8 2003. Links http://www.wwiionline.com/ http://www.idsoftware.com/games/doom/ http://www.hitechcreations.com/ http://www.totalsims.com/index.php?url=wbiii/content_home.php http://www.hitechcreations.com/forums/showthread.php?s=&amp;amp;amp;amp;amp;threadid=77265 http://www.senate.gov/member/ct/lieberman/releases/r110697c.html http://www.idsoftware.com/games/wolfenstein http://www.idsoftware.com/games/quake/ http://www.ea.com/eagames/official/moh_alliedassault/home.jsp http://www.jaleco.com/fighterace/index.html http://www.bartleby.com/201/1.html http://www.hitechcreations.com/forums/showthread.php?s=&amp;amp;amp;amp;amp;threadid=72560 Citation reference for this article Substitute your date of access for Dn Month Year etc... MLA Style Mullen, Mark. "It Was Not Death for I Stood Up…and Fragged the Dumb-Ass MoFo Who'd Wasted Me" M/C: A Journal of Media and Culture 6.1 (2003). Dn Month Year < http://www.media-culture.org.au/0302/03-itwasnotdeath.php>. APA Style Mullen, M., (2003, Feb 26). It Was Not Death for I Stood Up…and Fragged the Dumb-Ass MoFo Who'd Wasted Me. M/C: A Journal of Media and Culture, 6,(1). Retrieved Month Dn, Year, from http://www.media-culture.org.au/0302/03-itwasnotdeath.html

In this dissertation, we discuss the Distributed Spacecraft Attitude Control System Simulator (DSACSS) testbed developed at Virginia Polytechnic Institute and State University for the purpose of investigating various control techniques for single and multiple spacecraft. DSACSS is comprised of two independent hardware-in-the-loop simulators and one software spacecraft simulator. The two hardware-in-the-loop spacecraft simulators have similar subsystems as flight-ready spacecraft (e.g. command and data handling; communications; attitude determination and control; power; payload; and guidance and navigation). The DSACSS framework is a flexible testbed for investigating a variety of spacecraft control techniques, especially control scenarios involving coupled attitude and orbital motion. The attitude hardware simulators along with numerical simulations assist in the development and evaluation of Lyapunov based asymptotically stable, nonlinear attitude controllers with three reaction wheels as the control device. The angular rate controller successfully tracks a time varying attitude trajectory. The Modified Rodrigues Parmater (MRP) attitude controller results in successfully tracking the angular rates and MRP attitude vector for a time-varying attitude trajectory. The attitude controllers successfully track the reference attitude in real-time with hardware similar to flight-ready spacecraft. Numerical simulations and the attitude hardware simulators assist in the development and evaluation of a robust, asymptotically stable, nonlinear attitude controller with three reaction wheels as the actuator for attitude control. The MRPs are chosen to represent the attitude in the development of the controller. The robust spacecraft attitude controller successfully tracks a time-varying reference attitude trajectory while bounding system uncertainties. The results of a Global Positioning System (GPS) hardware-in-the-loop simulation of two spacecraft flying in formation are presented. The simulations involve a chief spacecraft in a low Earth orbit (LEO), while a deputy spacecraft maintains an orbit position relative to the chief spacecraft. In order to maintain the formation an orbit correction maneuver (OCM) for the deputy spacecraft is required. The control of the OCM is accomplished using a classical orbital element (COE) feedback controller and simulating continual impulsive thrusting for the deputy spacecraft. The COE controller requires the relative position of the six orbital elements. The deputy communicates with the chief spacecraft to obtain the current orbit position of the chief spacecraft, which is determined by a numerical orbit propagator. The position of the deputy spacecraft is determined from a GPS receiver that is connected to a GPS hardware-in-the-loop simulator. The GPS simulator creates a radio frequency (RF) signal based on a simulated trajectory, which results in the GPS receiver calculating the navigation solution for the simulated trajectory. From the relative positions of the spacecraft the COE controller calculates the OCM for the deputy spacecraft. The formation flying simulation successfully demonstrates the closed-loop hardware-in-the-loop GPS simulator. This dissertation focuses on the development of the DSACSS facility including the development and implementation of a closed-loop GPS simulator and evaluation of nonlinear feedback attitude and orbit control laws using real-time hardware-in-the-loop simulators.
Ph. D.