2,303,477 research outputs found
The Profundity of Polychoralism: Exploring the work of Jonathan David Little [Interview and CD review]
No full textExtended (7000-word) composer interview and CD review of "Woefully Arrayed: Sacred & Secular Choral & Polychoral Music of Jonathan David Little", by London-based international music critic, Colin Clarke.
[INTERVIEW:] "The disc of sacred and secular choral and polychoral music by Jonathan David Little, Woefully Arrayed … is nothing short of remarkable. Stunningly recorded, the pure sonic joy is visceral. On a personal level, I haven’t experienced such revelation in choral terms since the Tallis Scholars’ first recording of the Allegri Miserere. As an interviewee, it turns out, Little is every inch as fascinating as his music. The following in-depth interview may be seen as an indispensable complement to the listening experience itself."
[CD REVIEW:] "Jonathan David Little is a composer whose music is vital, urgent and yet somehow timeless at the same time. … Woefully Arrayed has a mesmeric element to it … [and] is a masterpiece of time-stretching. As lines float and interact throughout the soundspace, there is a distinct impression of atemporality, of altering the way the listener experiences time. … sound is superb, full and reverberant … magnificently handled … A superb disc, one that simply gets better on each and every listening. There is a radiance to Little’s writing that seems shot through with spiritual light and which speaks on a very deep level to the listener."
PROJECT OVERVIEW: International Polychoral Music Composition, Recording and Dissemination Project (2015-17)
“The lost potential of the acoustics of performing spaces begins to be rediscovered in these works.”
A complex and ambitious, large-scale, two-year “polychoral” music creation and recording project was commissioned by the Australia Council – involving communicating how “re-discovered” ancient Renaissance and Baroque techniques of acoustically-innovative performer placement may be revived within new, original, contemporary contexts. One aim was to generate interest in largely long-forgotten, but still hugely useful and aurally impressive composition methods. Following a period of research and experimentation, several new, accessible choral works were created – most featuring intricate, a cappella, polychoral-inspired techniques. Therefore different sections of the choir, or different “sub-choirs” and/or vocal soloists, are sometimes placed in various arrangements around and above the audience (occasionally also involving movement). Due to the incorporation of such techniques, a striking extra dimension is added both to recordings and live performances – where the aural “spatial” interest creates a quasi-theatrical effect.
OPEN-ACCESS ONLINE CD BOOKLET (including contextual essay, spatial configuration diagrams, lyrics, pictures and notes): http://www.navonarecords.com/catalog/nv6113/booklet---woefully-arrayed---jonathan-little.htm
High-Order Sliding Mode Control for the Test Mass stabilization of the LISA MIssion: preliminary results
No full textThe main objective of this paper is the design of a controller for the test mass release of the
Laser Interferometer Space Antenna (LISA) mission. Since the test masses are used as sensors
in the science phase for environmental measurements, the control system can be able to robustly
deal with large initial deviations of the release mechanism. Moreover, the control system should
be able to maintain and stabilize the test masses with a precision. For this reason, two Sliding
Mode Control (SMC) are included in this study. A second-order SMC is mainly proposed for this
critical phase, which is able to handle uncertainties and noise introduced by the sensors system.
This controller is compared with a first-order SMC, which was used in LISA Pathfinder mission,
in terms of accuracy and stead-state error. A nonlinear orbital simulator is considered in the
simulations, with limitations both of the actuation system (with saturation and delay) and of the
update frequencies. Model uncertainties, different initial conditions and external disturbances are
also included in the performed simulations
Drag-free and attitude control system for the LISA space mission: an H-infinity constrained decoupling approach
No full textThis article presents an approach to drag-free and attitude control for the laser interferometer space antenna (LISA) space mission, based on a constrained decoupling H-infinity approach. LISA will be a space-based gravitational wave observatory, which is expected to be launched by the European Space Agency (ESA) in 2034. The LISA concept consists of a constellation of three satellites that exchange a bidirectional laser link to perform interferometry. The gravitational waves can be detected by measuring the relative distance variations, by means of laser interferometers, between two free-falling bodies located at a far distance, called the test masses (TMs). In this framework, the spacecraft (SC) drag-free attitude control plays a key role since it allows the TMs to move in free-fall conditions, rejecting external disturbances and noises, at the nanoscopic level, that can compromise the quality of scientific measurements. To this end, we propose an H-infinity drag-free attitude controller, based on a constrained decoupling of the SC linearized dynamics, where the pseudoinverse of the control matrix is obtained by minimizing the inversion error. Moreover, we provide sufficient conditions for stability of the closed-loop, in order to ensure that the decoupling inversion error does not affect the closed-loop stability. The effectiveness of the proposed approach is confirmed by means of an extensive Monte Carlo campaign, carried out employing a high-fidelity simulator
The LISA DFACS: A nonlinear model for the spacecraft dynamics
No full textIn the last few years, the observation of gravitational waves by means of LIGO and Virgo interferometers and the success of LISA Pathfinder, gave a significant boost to the development of space-based gravitational wave observatories. The European Space Agency confirmed LISA as the third large class mission of the Cosmic Vision program. The present work is part of the Drag Free and Attitude Control System (DFACS) preliminary prototyping study, which aims at the development of mathematical models and advanced controllers for the science phases of the LISA mission. Nonlinear modelling is a fundamental step for the derivation of linearized and decoupled models as well as for the development of suitable linear and nonlinear controllers. In this paper, an analytical nonlinear model is derived, which describes all the relevant dynamics of a LISA spacecraft, representing an effective compromise between accuracy and complexity. The model is extensively validated through linearization analysis and Monte Carlo simulations
LISA Drag-Free Attitude Control System: Robust Stability and Performance Analysis
No full textThis paper proposes a robust stability and performance verification of the Drag-Free and Attitude Control System (DFACS) for the Laser Interferometer Space Antenna (LISA) space mission. LISA is a space-based gravitational wave observatory, expected to be launched by the European Space Agency in 2034. LISA was formally adopted by ESA in January 2024 as the third large-class mission of the Cosmic Vision program, marking the transition from the mission conceptual design to hardware development. The mission features a constellation of three spacecraft exchanging bidirectional laser links to perform interferometry: they measure the relative distance variations between free-falling test masses located at far distances. Given the categorical need of obtaining precise measurements, the DFACS plays a key role, since it allows the test masses to move in free-fall conditions, rejecting at the nanoscopic level external disturbances and noises, which can compromise the quality of the scientific measurements. A fundamental issue in this context is to rigorously analyze robust stability and robust performance of the closed-loop system. Based on a previously designed DFACS, in this paper we address this issue by means of mu-analysis. The theoretical analyses are supported by an extensive Monte Carlo campaign, carried out employing a high-fidelity simulator. Both the theoretical analyses and simulations show that the designed DFACS guarantees the desired closed-loop robustness levels
The LISA DFACS: Preliminary Model Predictive Control Design for the Test Mass Release Phase
No full textThis paper presents a preliminary control design for the test mass release phase of the LISA space mission. LISA will feature a triangular constellation of three spacecraft dedicated to the detection of gravitational waves. Each spacecraft carries two cubic free-falling test masses needed for the scientific experiment, which are initially locked by a clamp mechanism. When the plungers are retracted, the free-floating test masses are captured electrostatically by means of an electrostatic suspension system. However, the low actuation authority and the critical initial conditions, make the attitude and translation control of the test mass a difficult task. Model Predictive Control (MPC) appears to be a suitable technique for this application because of its ability to deal with the state constraints and the input saturations. In the present paper, the TM release context is briefly analysed, then the preliminary MPC design and simulation results are shown
The LISA DFACS: Overview of the Control Design Activities for the Drag-Free Mode
No full textThis paper presents the main design steps for the drag-free control of the next LISA mission. This work was carried out during the feasibility study Assessment and Preliminary Prototyping of a drag free control system for the L3 gravity wave observatory supported by the European Space Agency. After a brief introduction about the spacecraft, the main modelling results are reported. Functional and performance requirements are shown and then the control architecture and the H-inf mixed sensitivity control design are discussed. Finally, simulation results are presented
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