High-Precision Regulation of a Pressure Controlled Artificial Mouth: The Case of Recorder-Like Musical Instruments

Abstract

Dated: January 10, 2010 )Real-time regulation of air pressure in an articial mouth i s studied. A closed-loop strategyis developped, including a controller algorithm which upda tes (according to the dierencebetween the target and the measured blowing pressure) the el ectrical command sent to thesero-valve providing air ow. In this paper the targets cons idered may be steady states orslowly varying trajectories. Since both the musical instru ment and the servo-valve behavenonlinearly, the design of the controller algorithm requir es preliminary modelling and identi-cation steps in order to optimize the compromise performan ces/robustness. The controllernally adopted for the experiments is a PI (Proportional Int egral) whose integral gain isadapted according to an online estimator. Moreover, a caref ully tuned dither signal is addedon the electric command in order to limit consequences of fri ction inside the servo-valve.The high-precision regulation is used to investigate the fu nctionning of the recorder. Firstly,it allows to highlight the existence of aeolian sounds which had never been observed on arecorder. Moreover, the inuence of some small details of the chamfers geometry on theglobal behavior of the instrument is investigated. Hence th e inuence of the maker's workcan be evaluated, as well as the important consequences on th e possibilities oered to theplayer: with the optimized chamfers, the instrument can sou nd louder and the transitionbetween the two regimes is safer (larger hysteresis width).PACS numbers: 43.75.Ef, 43.75.Qr, 43.75.YyI. INTRODUCTIONBlowing machines (or articial mouths), were devel-oped since the early stage of research in musical acoustics(at least since 65 years,