Observer-based tuning of two-inertia servo-drive systems with integrated SAW torque transducers

This paper proposes controller design and tuning methodologies that facilitate the rejection of periodic load-side disturbances applied to a torsional mechanical system while simultaneously compensating for the observer’s inherent phase delay. This facilitates the use of lower-bandwidth practically realizable disturbance observers. The merits of implementing full- and reduced-order observers are investigated, with the latter being implemented with a new low-cost servo-machine-integrated highband width torque-sensing device based on surface acoustic wave (SAW) technology. Specifically, the authors’ previous work based on proportional–integral–derivative (PID) and resonance ratio control (RRC) controllers (IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1226–1237, Aug. 2006) is augmented with observer disturbance feedback. It is shown that higher-bandwidth disturbance observers are required to maximize disturbance attenuation over the low-frequency band (as well as the desired rejection frequency), thereby attenuating a wide range of possible frequencies. In such cases, therefore, it is shown that the RRC controller is the preferred solution since it can employ significantly higher observer bandwidth, when compared to PID counterparts, by virtue of reduced noise sensitivity. Furthermore, it is demonstrated that the prototype servo-machine-integrated 20-N · mSAWtorque transducer is not unduly affected by machine-generated electromagnetic noise and exhibits similar dynamic behavior as a conventional instrument inline torque transducer

Assessment of Haiti’s electricity sector

INTRODUCTION: This report summarizes the current state of the electricity sector in Haiti, to form a knowledge base from which to subsequently evaluate options for how best to increase electricity access in Haiti. Accordingly, this report summarizes the results of an extensive review of the publicly-available information on the electricity sector in Haiti, supplemented by targeted interviews with selected individuals known to be knowledgeable about electricity in Haiti based on their recent involvement in assessing the sector or in pursuing/supporting development opportunities. [TRUNCATED

Engineering telecommunication services with SDL

If formal techniques are to be more widely accepted then they should evolve as current software engineering approaches evolve. Current techniques in the development of distributed systems use interface definition languages (IDLs) as a basis for the underlying communication and also as an abstraction tool. Object-oriented technologies [6] and the idea of engineering software through frameworks [5] are also widely accepted approaches in developing software. In this paper we show how the formal specification language SDL and associated tool support have been applied in the TOSCA1 project to engineer telecommunication services using these current techniques

Nonlinear Observers for Human-in-the-loop Control Systems

The development of models for a human-in-the-loop with hardware is an area of ongoing research. The ability to simulate a human-in-the-loop with hardware provides a platform for better understanding the dynamics of human and machine cognition. A human-in-the-loop model provides information that can be used to design more efficient human interfaces and smarter autonomous assistant controllers. This can make a complex task such as flying an aircraft safer and more accessible. This thesis explores different possibilities for human operator models to be modeled in the loop with a vehicle. A human is modeled as a linear state feedback controller in the loop with the task of controlling a simple solid ball. The human arm is modeled controlling a joystick as the human is considered to control the ball with a joystick. Nonlinear sliding mode observers are developed to estimate the gains of a feedback control law and nonlinear sliding mode observers are developed to estimate the torques on the shoulder, elbow, and joystick joints. The nonlinear observers are simulated on a human-in-the-loop system to show the accuracy of the observers

Handling Qualities Flight Testing of the Stratospheric Observatory for Infrared Astronomy (SOFIA)

Airborne infrared astronomy has a long successful history, albeit relatively unknown outside of the astronomy community. A major problem with ground based infrared astronomy is the absorption and scatter of infrared energy by water in the atmosphere. Observing the universe from above 40,000 ft puts the observation platform above 99% of the water vapor in the atmosphere, thereby addressing this problem at a fraction of the cost of space based systems. The Stratospheric Observatory For Infrared Astronomy (SOFIA) aircraft is the most ambitious foray into the field of airborne infrared astronomy in history. Using a 747SP (The Boeing Company, Chicago, Illinois) aircraft modified with a 2.5m telescope located in the aft section of the fuselage, the SOFIA endeavors to provide views of the universe never before possible and at a fraction of the cost of space based systems. The modification to the airplane includes moveable doors and aperture that expose the telescope assembly. The telescope assembly is aimed and stabilized using a multitude of on board systems. This modification has the potential to cause aerodynamic anomalies that could induce undesired forces either at the cavity itself or indirectly due to interference with the empennage, both of which could cause handling qualities issues. As a result, an extensive analysis and flight test program was conducted from December 2009 through March 2011. Several methods, including a Lower Order Equivalent Systems analysis and pilot assessment, were used to ascertain the effects of the modification. The SOFIA modification was found to cause no adverse handling qualities effects and the aircraft was cleared for operational use. This paper discusses the history and modification to the aircraft, development of test procedures and analysis, results of testing and analysis, lessons learned for future projects and justification for operational certification

The Return of the Rogue

The “rogue trader”—a famed figure of the 1990s—recently has returned to prominence due largely to two phenomena. First, recent U.S. mortgage market volatility spilled over into stock, commodity, and derivative markets worldwide, causing large financial institution losses and revealing previously hidden unauthorized positions. Second, the rogue trader has gained importance as banks around the world have focused more attention on operational risk in response to regulatory changes prompted by the Basel II Capital Accord. This Article contends that of the many regulatory options available to the Basel Committee for addressing operational risk it arguably chose the worst: an enforced selfregulatory regime unlikely to substantially alter financial institutions’ ability to successfully manage operational risk. That regime also poses the danger of high costs, a false sense of security, and perverse incentives. Particularly with respect to the low-frequency, high-impact events—including rogue trading—that may be the greatest threat to bank stability and soundness, attempts at enforced self-regulation are unlikely to significantly reduce operational risk, because those financial institutions with the highest operational risk are the least likely to credibly assess that risk and set aside adequate capital under a regime of enforced self-regulation

Composition and Declassification in Possibilistic Information Flow Security

Formal methods for security can rule out whole classes of security vulnerabilities, but applying them in practice remains challenging. This thesis develops formal verification techniques for information flow security that combine the expressivity and scalability strengths of existing frameworks. It builds upon Bounded Deducibility (BD) Security, which allows specifying and verifying fine-grained policies about what information may flow when to whom. Our main technical result is a compositionality theorem for BD Security, providing scalability by allowing us to verify security properties of a large system by verifying smaller components. Its practical utility is illustrated by a case study of verifying confidentiality properties of a distributed social media platform. Moreover, we discuss its use for the modular development of secure workflow systems, and for the security-preserving enforcement of safety and security properties other than information flow control

The Herschel-SPIRE instrument and its in-flight performance

The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 μm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194–671 μm (447–1550 GHz). The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 0.3 K. The photometer has a field of view of 4´× 8´, observed simultaneously in the three spectral bands. Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired. The spectrometer has an approximately circular field of view with a diameter of 2.6´. The spectral resolution can be adjusted between 1.2 and 25 GHz by changing the stroke length of the FTS scan mirror. Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data. For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view. The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling. Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products. The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 1.5–2

Tasapainottavan järjestelmän robottien säätösuunnittelu

A balancing robot control system is similar to any unstable dynamical system that can be controlled with a PID. Examples of unstable dynamical systems can be e.g. self-balancing scooter and jet fighter missile guidance applications. The versatility and availability of consumer market microcontroller development platforms and control simulation software gives an opportunity for the independent developer to take on an arbitrary unstable dynamics control design assignment. Hence, a balancing control system was utilized in an Arduino based robot that can stabilize itself despite of perturbation and its intrinsic nature of an inverted pendulum. In this Thesis, a MinSeg balancing robot control design is carefully studied and reconstructed. First, the Equations of Motion (EOM) of the robot wheels, body and motor are designed, linearized and the Transfer Function (TF) is determined for a model of the robot. Then this model hypothesis is applied to practice by constructing a PID controller that stabilizes the TF. Following a successful implementation of the controller, a form of disturbance is added to the model and the robot control is simulated and field-tested. In conclusion, the PID controller is derived more robust and thus disturbance tolerant by redesigning the control system primarily for the simulated environment and then for the real world. The implemented solution was to divide the subject into parts that begin from the basics of control and continue to the hands on experiments with the balancing robot. Each component of the mathematical framework was evaluated, prototyped and tested. The meticulous fieldwork resulted in more accurate control parameters that contributed to the final robust design application.Tasapainottavan järjestelmän robottien säätötekniikka on samankaltainen muiden epästabiilien dynaamisten systeemien kanssa, joita voidaan ohjata PID-säätimellä. Epästabiileja dynaamisia systeemejä ovat esimerkiksi tasapainoskootteri ja suihkuhävittäjän ohjusohjausjärjestelmä. Kuluttajalle tarkoitettujen mikrokontrollerien kehitysalustojen ja säätösimulaatio-ohjelmistojen monimuotoisuuden ja saatavuuden ansiosta itsenäiset järjestelmäkehittäjät voivat ottaa mielivaltaisen kehitysprojektin automaation säätötekniikkaan liittyen. Tämän mahdollisuuden ansiosta Arduino-pohjaisen robotin säätöjärjestelmä otettiin kehitettäväksi, jotta saataisiin luotua häiriösietoinen säädin, joka kumoaisi käänteisen heilurin vaikutuksen robotissa. Tässä työssä MinSeg-robotille olemassa oleva säätösuunnitelma tutkittiin huolellisesti ja tehtiin alusta alkaen uudelleen. Aluksi tarvittavat liikeyhtälöt robotin renkaille, rungolle ja moottorille suunniteltiin, linearisoitiin ja yhdistettiin siirtofunktioksi. Sitten saatu mallihypoteesi toteutettiin käytännössä PID-säätimellä, joka stabiloi kyseessä olevan siirtofunktion. Toimivaa säädintä paranneltiin häiriömallin lisäämisellä ja säädön onnistumista tarkkailtiin kenttäkokeilla. Lopuksi PID-säädintä kehitettiin robustimmaksi häiriömallin avulla ensin simulaatioissa ja sitten käytännön kokeissa. Ratkaisu oli jakaa aihe osiin, joissa aloitettiin säätötekniikan perusteista ja päädyttiin kyseisen tasapainorobotin ohjaukseen. Jokainen matemaattinen säätökomponentti ensin tutkittiin, tehtiin siitä testiversio ja lopuksi kokeiltiin toimivaa ratkaisua käytännössä. Huolellisen ja tarkan kenttätyön ansiosta robotille tallennettiin täsmällisemmät säätöparametrit, minkä ansiosta robotin häiriösietokyky parani