Operator splitting method for friction constrained dynamical systems

Linear and nonlinear spectroscopy techniques are widely used to study numerous important chemical and physical processes. However, the interpretation of these experimental spectra often becomes very complicated because a particular spectrum constitutes a mere footprint of a host of various, possibly intertwined, effects. In this spirit, calculations in the time-dependent picture provide a useful tool for decoding such spectra. Nevertheless, the ultimate challenge is to devise a theoretical framework that could yield sufficient efficiency as well as accuracy to describe the molecular system of interest in a satisfactory way. The strategy is relatively straightforward for low dimensional systems that are directly tractable, e.g., with exact quantum dynamics performed on an equidistant grid. Despite the formidable overall exponential scaling, these calculations can be significantly accelerated by using higher-order split-operator propagation schemes. In general however, one is forced to seek an affordable balance between physical accuracy on one hand and computational efficiency on the other by employing, for instance, some of the techniques from the broad family of semiclassical methods based on classical trajectories. To this end, the thawed Gaussian approximation (TGA) is combined with an on-the-fly ab initio scheme (OTF-AI). The resulting OTF-AI-TGA algorithm is efficient enough to treat all vibrational degrees of freedom (DOFs) on an equal footing even in case of larger molecules such as pentathiophene (105 DOFs). Moreover, in sharp contrast to popular approaches based on global harmonic approximation, OTF-AI-TGA reproduces almost perfectly the absorption and photoelectron spectra of ammonia, i.e., spectra with strong dependence on large amplitude motions. In addition to the mere reproduction of experimental spectra, a novel systematic approach is introduced to assess the importance and the dynamical couplings of individual vibrational DOFs. This is in turn used to gain a deeper insight into the associated physical and chemical processes by attributing specific spectral features to the underlying molecular motion. Specifically, in the case of oligothiophenes, this approach was used to assign the dynamical interplay between quinoid and aromatic characters of individual rings to particular spectral patterns and, furthermore, to explain the changes in the vibrational line shape with an increasing number of rings. Furthermore, in systems that are too large to be treated with accurate quantum methods, efficient methods such as OTF-AI-TGA are expected to be useful as a preliminary tool for identification of the subspace of the important DOFs. On this subspace, one can then unleash some of the less efficient yet better-suited methods. In summary, OTF-AI-TGA combined with this novel analysis approach is intended to provide the first crucial step in a hierarchical computational protocol for studying large molecules such as dyes.

Developing a software system for mission planners at NASA’s Johnson Space Center (JSC) to plan and schedule activities onboard the Space Shuttle or International Space Station (ISS) is a complex task. Due to the scope of the complete user requirements and budget restrictions, a full development of all capabilities was not practical. The planning system had to include not only capabilities for planning the daily activities onboard the spacecraft, but also had to include the capability to upload the plans to the onboard system and to merge plans and activities from planners at other remote planning centers, including Marshall Space Flight Center (MSFC) and International Partners. The Integrated Planning System (IPS) Consolidated Planning System (CPS) was developed in an incremental fashion to continually meet the most immediate needs for the users. CPS has been under development for over 8 years and has been operational at JSC for 5 years, supporting Space Shuttle Program (SSP) and ISS mission planning. The journey to this point of software capabilities has been slow, but steady. The current size of the software application is over 380 K SLOC. Initial development focused on capability for scheduling SSP missions, as this was the most immediate need. Next, the development focused on ISS capability, such as plan upload and advanced long-range planning techniques. Finally, the development focused on including/merging data from MSFC and the International Partners. This paper documents some of the “Lessons Learned” during the development of the CPS. Some examples of these include: • Focusing on current operational needs creates system requirements that may not be applicable in future operations • File exchange mechanism uses a proprietary file format that is not flexible to change • Size and quantity of current planning data seriously hampers performance of the system • Incremental approach to development adds new functionality as peripheral to core functionality The nature of “Lessons Learned” tends to focus our attention on deficiencies in the software. We look at actions or functionality that could have been implemented better or planned better. Focusing on these may give the reader the false impression that the CPS is a short sighted, unusable system. However, the system is stable and quite comprehensive in its capabilities for planning current ISS and SSP operations. The incremental approach allowed the development team to tailor the software to shifting user requirements as planning user operations scenarios and requirements changed. Overall, the CPS is an excellent planning system. This paper is intended to provide some assistance in a “path through the mine field” of software development for planning space mission operations. It is hoped that these “Lessons Learned” can be applied in future space mission planning system projects to avoid some of the limitations of the current system.

Lessons learned from the STS-120/ISS 10A robotics operations

In the preparation for missions to Mars, basic knowledge of the mechanisms of growth and development of living plants under microgravity (micro-g) conditions is essential. Focus has centered on the g-effects on rigidity, including mechanisms of signal perception, transduction, and response in gravity resistance. These components of gravity resistance are linked to the evolution and acquisition of responses to various mechanical stresses. An overview is given both on the basic effect of hypergravity as well as of micro-g conditions in the cell wall changes. The review includes plant experiments in the US Space Shuttle and the effect of short space stays (8–14 days) on single cells (plant protoplasts). Regeneration of protoplasts is dependent on cortical microtubules to orient the nascent cellulose microfibrils in the cell wall. The space protoplast experiments demonstrated that the regeneration capacity of protoplasts was retarded. Two critical factors are the basis for longer space experiments: a. the effects of gravity on the molecular mechanisms for cell wall development, b. the availability of facilities and hardware for performing cell wall experiments in space and return of RNA/DNA back to the Earth. Linked to these aspects is a description of existing hardware functioning on the International Space Station.

Validation of the new trapped environment AE9/AP9/SPM at low Earth orbit

In this thesis, we present a dynamical systems approach to adaptive controllers for locomotion control. The approach is based on a rigorous mathematical framework using nonlinear dynamical systems and is inspired by theories of self-organization. Nonlinear dynamical systems such as coupled oscillators are an interesting approach for the on-line generation of trajectories for robots with many degrees of freedom (e.g. legged locomotion). However, designing a nonlinear dynamical system to satisfy a given specification and goal is not an easy task, and, hitherto no methodology exists to approach this problem in a unified way. Nature presents us with satisfactory solutions for the coordination of many degrees of freedom. One central feature observed in biological subjects is the ability of the neural systems to exploit natural dynamics of the body to achieve efficient locomotion. In order to be able to exploit the body properties, adaptive mechanisms must be at work. Recent work has pointed out the importance of the mechanical system for efficient locomotion. Even more interestingly, such well suited mechanical systems do not need complicated control. Yet, in robotics, in most approaches, adaptive mechanisms are either missing or they are not based on a rigorous framework, i.e. they are based on heuristics and ad-hoc approaches. Over the last three decades there has been enormous progress in describing movement coordination with the help of Synergetic approaches. This has led to the formulation of a theoretical framework: the theory of dynamic patterns. This framework is mathematically rigorous and at the same time fully operational. However, it does not provide any guidelines for synthetic approaches as needed for the engineering of robots with many degrees of freedom, nor does it directly help to explain adaptive systems. We will show how we can extend the theoretical framework to build adaptive systems. For this purpose, we propose the use of multi-scale dynamical systems. The basic idea behind multi-scale dynamical systems is that a given dynamical system gets extended by additional slow dynamics of its parameters, i.e. some of the parameters become state variables. The advantages of the framework of multi-scale dynamical systems for adaptive controllers are 1) fully dynamic description, 2) no separation of learning algorithm and learning substrate, 3) no separation of learning trials or time windows, 4) mathematically rigorous, 5) low dimensional systems. However, in order to fully exploit the framework important questions have to be solved. Most importantly, methodologies for designing the feedback loops have to be found and important theoretical questions about stability and convergence properties of the devised systems have to be answered. In order to tackle this challenge, we first introduce an engineering view on designing nonlinear dynamical systems and especially oscillators. We will highlight the important differences and freedom that this engineering view introduces as opposed to a modeling one. We then apply this approach by first proposing a very simple adaptive toy-system, consisting of a dynamical system coupled to a spring-mass system. Due to its spring-mass dynamics, this system contains clear natural dynamics in the form of resonant frequencies. We propose a prototype adaptive multi-scale system, the adaptive frequency oscillator, which is able to adapt its intrinsic frequency to the resonant frequency of the body dynamics. After a small sidetrack to show that we can use adaptive frequency oscillators also for other applications than for adaptive controllers, namely for frequency analysis, we then come back to further investigation of the adaptive controller. We apply the same controller concept to a simple spring-mass hopper system. The spring-mass system consists of a body with two legs attached by rotational joints. The legs contain spring-damper elements. Finally, we present results of the implementation of the controller on a real robot, the experimental robot PUPPY II. This robot is a under-actuated robot with spring dynamics in the knee joints. It will be shown, that due to the appropriate simplification and concentration on relevant features in the toy-system the controller concepts works without a fundamental change on all systems from the toy system up to the real robot.

: This thesis used the certainity equivalence approach and the theory of self-tuning regulators to derive an iterative method which generates an optimal incentive control for the leader in a static, two-player Stackelberg game with unknown cost functionals. The method uses all available degrees of freedom to restrict the incentive matrix to a diagonal structure. This restriction assures the leader of a unique optimal incentive control. Convergence to the optimal incentive control has been proven for the scalar problem and simulation studies have shown good convergence results for the second order problem. It is expected that this method is extendable in its present form to a general n-th order problem. The iterative method is applied to a scalar economic example involving government regulation of a monopoly. A simulation study of the problem revealed that the desired regulation was indeed achieved. The effectiveness of the method is demonstrated on a general second order numerical problem. Future research regarding application of optimal incentive controls to Stackelberg games with unknown cost functionals may now focus on two general areas. Starting with the iterative method detailed in this thesis, one may abandon the diagonal incentive matrix structure and attempt to use the resulting degrees of freedom to satisfy other useful criteria. An example of this is given by the minimum sensitivity design approach mentioned earlier. It is desirable to extend the existing methods to dynamical systems and to problems involving more than two players.

One of the many expectations of the International Space Station (ISS) is the clarification of essential questions in connection with long-lasting spaceflights with a human crew. These questions comprise operational, physiological, psychological, and safety aspects among others. Existing experiences come from the lunar programme, the development of space stations by the Soviet Union, and the Space Shuttle and Mir programmes. They have led to the present operational planning and crew composition tor the ISS that is being executed during the current phase of its assembly and early utilisation. What is still pending is the integration of yet more partner programmes into the existing complex, but not only with their associated hardware and demand on resources. The ISS can only be called truly international when astronauts from all partner states, with their differences in culture and backgrounds, are regularly included in the expedition crews.This paper analyses the demands on such expedition crews from a crew standpoint. Derived from the hands-on experience of the Mir’97 mission in which the author participated, as well as from other Mir and Space Shuttle flights dedicated to science, plus the knowledge gained after almost 2 years of ISS operations, a set of improved selection criteria for the composition of an ISS expedition crew is presented.KeywordsInternational Space StationSpace ShuttleCrew MemberHuman SpaceflightSpace Transportation SystemThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

<div class="htmlview paragraph">The Lithium Hydroxide (LiOH) management plan to control carbon dioxide (CO<sub>2</sub>) for the Shuttle while docked to the International Space Station (ISS) reduces the mass and volume needed to be launched. For missions before Flight UF-1/STS-108, the Shuttle and ISS each removed their own CO<sub>2</sub> during the docked time period. To control the CO<sub>2</sub> level, the Shuttle used LiOH canisters and the ISS used the Vozdukh or the Carbon Dioxide Removal Assembly (CDRA) with the Vozdukh being the primary ISS device for CO<sub>2</sub> removal. Analysis predicted that both the Shuttle and Station atmospheres could be controlled using the Station resources with only the Vozdukh and the CDRA. If the LiOH canisters were not needed for the CO<sub>2</sub> control on the Shuttle during the docked periods, then the mass and volume from these LiOH canisters normally launched on the Shuttle could be replaced with other cargo. On the Flight UF-1/STS-108 mission, a Station Detailed Test Objective (SDTO) showed the feasibility that both the Shuttle and Station atmospheres could be controlled using the Station resources.</div> <div class="htmlview paragraph">This paper will discuss the methods and their priority for removing CO<sub>2</sub>, how CDRA operations affect the plan, the sources of the LiOH canisters, the results of the SDTO, the performance and lifetime of the LiOH canisters, rotations plans, stowage issues, and future plans.</div>

A materials science experiment has been developed and readied for operation aboard the International Space Station (ISS). Components of this experiment are onboard ISS and are awaiting the flight of science samples. The goal of the experiment is to understand the dynamics of Ostwald ripening, also known as coarsening, a process that occurs in nearly any two-phase mixture found in nature. Attempts to obtain experimental data in ground-based laboratories are hindered due to the presence of gravity, which introduces material transport modes other than that of the coarsening phenomenon. This introduces adjustable parameters in the formulation of theory. The original coarsening in solid-liquid mixtures (CSLM) mission, which flew on the Space Shuttle in 1997, produced data from a coarsened eutectic alloy. Unfortunately, both the science matrix and the hardware, while nominally functional, did not account adequately for operations in microgravity. A significantly redesigned follow-on experiment, CSLM-2 has been developed to redress the inadequacies of the original experiment. This paper reviews the CSLM-2 project: its history, science goals, flight hardware implementation, and planned operations and analysis.

In order to meet the space transportation needs for a new century, America’s National Aeronautics and Space Administration (NASA) has implemented an Integrated Space Transportation Plan to produce safe, economical, and reliable access to space. One near term objective of this initiative is the design and development of a next-generation vehicle and launch system that will transport crew and cargo to and from the International Space Station (ISS), the Orbital Space Plane (OSP). The OSP system is composed of a manned launch vehicle by an existing Evolved Expendable Launch Vehicle (EELV). The OSP will provide emergency crew rescue from the ISS by 2008, and provide crew and limited cargo transfer to and from the ISS by 2012. A key requirement is for the OSP to be safer and more reliable than the Soyuz and Space Shuttle, which currently provide these capabilities.NASA has taken an integrated systems approach in designing the OSP launch system and related ground operations and launch support services. This “System-Centric” approach, as opposed to a “Vehicle-Centric” approach, presents unique challenges in terms of meeting the desired safety and reliability requirements As a result, NASA is utilizing PRA, a methodology for quantitative risk assessment, on the entire system during the design process and throughout the life of the system. When PRA is performed early in the design and development cycle with full engineering design and operations involvement, the PRA based integrated system model will provide a means for methodical and objective optimisation of the conceptual design.This paper discusses the development and implementation of PRA in the OSP Program. The OSP Program is the first major NASA program to perform and use PRA during the concept formulation phase of the program and is expected to produce the paradigm by which future space launch systems can be designed to meet successively higher safety and reliability demands [1].KeywordsInternational Space StationSpace ShuttleQuantitative Risk AssessmentProbabilistic Risk AssessmentIntegrate System ModelThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Cartesian approach for constrained mechanical systems with three degrees of freedom

This paper addresses the question of what contributions the International Space Station (ISS) can make as a sensor based remote sensing platform. There is precedent for the use of manned platforms in Low Earth Orbit (LEO). Skylab had the Earth Resources Experiment Package (EREP). In the Shuttle -Mir program, the Piroda module was dedicated to Earth sensing. One experiment in the Piroda, the Multispectral Stereo Scanner (MOMS-2PP) was used for quantifying the advantages of performing remote sensing on the ISS. The Space Shuttle program also made significant contributions to Earth observations. Sixteen missions carried electronic experiment packages for Earth observations and crew on almost every mission performed earth observations using cameras. Experiments planned for the ISS can also tell us much about the potential the ISS has as a remote sensing platform by examining their design and objectives. In March of 2009 an experiment called Agricultural Camera (AgCam) was delivered to the ISS for installation in the window of the Laboratory module. In fall of 2009 two more remote sensing experiments will arrive on the ISS - the Hyperspectral Imager for the Coastal Ocean (HICO) and the Remote Atmospheric and Ionospheric Detection System (RAIDS). These instruments will be combined on one experiment package, HICO- RAIDS experiment package (HREP), and will be placed outside the ISS, on an external platform.

The Orion spacecraft will replace the space shuttle and will be the first human spacecraft since the Apollo program to leave low earth orbit. This vehicle will serve as the cornerstone of a complete space transportation system with a myriad of mission requirements necessitating rendezvous to multiple vehicles in earth orbit, around the moon and eventually beyond . These goals will require a complex and robust vehicle that is, significantly different from both the space shuttle and the command module of the Apollo program. Historically, orbit operations have been accomplished with heavy reliance on ground support and manual crew reconfiguration and monitoring. One major difference with Orion is that automation will be incorporated as a key element of the man-vehicle system. The automated system will consist of software devoted to transitioning between events based on a master timeline. This effectively adds a layer of high level sequencing that moves control of the vehicle from one phase to the next. This type of automated control is not entirely new to spacecraft since the shuttle uses a version of this during ascent and entry operations. During shuttle orbit operations however many of the software modes and hardware switches must be manually configured through the use of printed procedures and instructions voiced from the ground. The goal of the automation scheme on Orion is to extend high level automation to all flight phases. The move towards automation represents a large shift from current space shuttle operations, and so these new systems will be adopted gradually via various safeguards. These include features such as authority-to-proceed, manual down modes, and functional inhibits. This paper describes the contrast between the manual and ground approach of the space shuttle and the proposed automation of the Orion vehicle. I will introduce typical orbit operations that are common to all rendezvous missions and go on to describe the current Orion automation architecture and contrast it with shuttle rendezvous techniques and circumstances. The shuttle rendezvous profile is timed to take approximately 3 days from orbit insertion to docking at the International Space Station (ISS). This process can be divided into 3 phases: far-field, mid-field and proximity operations. The far-field stage is characterized as the most quiescent phase. The spacecraft is usually too far to navigate using relative sensors and uses the Inertial Measurement Units (IMU s) to numerically solve for its position. The maneuvers are infrequent, roughly twice per day, and are larger than other burns in the profile. The shuttle uses this opportunity to take extensive ground based radar updates and keep high fidelity orbit states on the ground. This state is then periodically uplinked to the shuttle computers. The targeting solutions for burn maneuvers are also computed on the ground and uplinked. During the burn the crew is responsible for setting the shuttle attitude and configuring the propulsion system for ignition. Again this entire process is manually driven by both crew and ground activity. The only automatic processes that occur are associated with the real-time execution of the burn. The Orion automated functionality will seek to relieve the workload of both the crew and ground during this phase

The Microgravity Acceleration Measurement System (MAMS) is a high resolution and wide dynamic range dual sensor-based accelerometry instrumentation system which is under development for an early Utilization Flight installation within the International Space Station's (ISS) U.S. Laboratory Module. The MAMS instrument will provide highly accurate acceleration measurement data over the nano-g to millig amplitude range characterizing the U.S. Lab Module environment in the frequency spectrum from 104 Hz to 300 Hz. The data will be transmitted to ground users such as microgravity science investigators and the Microgravity Analysis and Integration Team members. The MAMS quasi-steady acceleration measurement instrument, the Orbital Acceleration Measurement Experiment (OARE), and a vibratory microgravity disturbance measurement instrument, the High Resolution Accelerometer Package (HIRAP) were previously flown on the Space Shuttle and will be installed with additional interface and control units into a MAMS enclosure. The MAMS will interface to an EXPRESS Rack and provide acceleration measurement data via an Ethernet link to the Rack Interface Controller for subsequent downlink transmission This paper addresses the MAMS performance specifications imposed and the new design solutions developed to meet the required performance. A description of the MAMS operational modes, calibration techniques and data/command interface is also included.