Systems control theory applied to natural and synthetic musical sounds

Systems control theory is a far developped field which helps to study stability, estimation and control of dynamical systems. The physical behaviour of musical instruments, once described by dynamical systems, can then be controlled and numerically simulated for many purposes. The aim of this paper is twofold: first, to provide the theoretical background on linear system theory, both in continuous and discrete time, mainly in the case of a finite number of degrees of freedom ; second, to give illustrative examples on wind instruments, such as the vocal tract represented as a waveguide, and a sliding flute

Some remarks on wheeled autonomous vehicles and the evolution of their control design

Recent investigations on the longitudinal and lateral control of wheeled autonomous vehicles are reported. Flatness-based techniques are first introduced via a simplified model. It depends on some physical parameters, like cornering stiffness coefficients of the tires, friction coefficient of the road, ..., which are notoriously difficult to identify. Then a model-free control strategy, which exploits the flat outputs, is proposed. Those outputs also depend on physical parameters which are poorly known, i.e., the vehicle mass and inertia and the position of the center of gravity. A totally model-free control law is therefore adopted. It employs natural output variables, namely the longitudinal velocity and the lateral deviation of the vehicle. This last method, which is easily understandable and implementable, ensures a robust trajectory tracking problem in both longitudinal and lateral dynamics. Several convincing computer simulations are displayed.Comment: 9th IFAC Symposium on Intelligent Autonomous Vehicles (Leipzig, Germany, 29.06.2016 - 01.07.2016

A new model-free design for vehicle control and its validation through an advanced simulation platform

A new model-free setting and the corresponding "intelligent" P and PD controllers are employed for the longitudinal and lateral motions of a vehicle. This new approach has been developed and used in order to ensure simultaneously a best profile tracking for the longitudinal and lateral behaviors. The longitudinal speed and the derivative of the lateral deviation, on one hand, the driving/braking torque and the steering angle, on the other hand, are respectively the output and the input variables. Let us emphasize that a "good" mathematical modeling, which is quite difficult, if not impossible to obtain, is not needed for such a design. An important part of this publication is focused on the presentation of simulation results with actual and virtual data. The actual data, used in Matlab as reference trajectories, have been obtained from a properly instrumented car (Peugeot 406). Other virtual sets of data have been generated through the interconnected platform SiVIC/RTMaps. It is a dedicated virtual simulation platform for prototyping and validation of advanced driving assistance systems. Keywords- Longitudinal and lateral vehicle control, model-free control, intelligent P controller (i-P controller), algebraic estimation, ADAS (Advanced Driving Assistance Systems).Comment: in 14th European Control Conference, Jul 2015, Linz, Austria. 201

Design of Algebraic Observers for Brass Instruments

International audiencePhysical high-fidelity models of brass instruments are available in the literature, but controlling them to obtain a proper musical restitution is still a challenge. The inversion of the model from a unique observation, namely the sound produced by the instrument, is therefore a natural way to deal with this situation. The observer design problem consisting in an estimation of the vibro-acoustic state of the system is essential for that purpose. The observer design problem was addressed in [@AN10] for an elementary brass system using elastic player lips and straight pipe models. A neutral system representation of the system and Lyapunov methods were used ; a proof of the observer stability was obtained and simulations have demonstrated that the estimation method is robust in the presence of noisy measurements. However no adaptation to the noise power was performed, leading to a rate of convergence of the observer that was suboptimal. Moreover, as the observer dynamics was related to the uncoupled lips dynamics, the response could be slow and oscillatory. Using a representation of the same brass model as a delay-differential algebraic system [@B13], together with a sensitivity analysis and Kalman filter theory, we address these limitations through a new observer design resulting in a substantial improvement of the observer rate of convergence

Muscle strength and exercise intensity adaptation to resistance training in older women with knee osteoarthritis and total knee arthroplasty

OBJECTIVES: To analyze muscle strength and exercise intensity adaptation to resistance training in older women with knee osteoarthritis and total knee arthroplasty. METHODS: Twenty-three community-dwelling women were divided into the following groups: older, with knee osteoarthritis and total knee arthroplasty in the contralateral limb (OKG; N= 7); older, without symptomatic osteoarthritis (OG; N= 8); and young and healthy (YG; N= 8). Muscle strength (1-repetition maximum strength test) and exercise intensity progression (workload increases of 5%-10% were made whenever adaptation occurred) were compared before and after 13 weeks of a twice-weekly progressive resistance-training program. RESULTS: At baseline, OKG subjects displayed lower muscle strength than those in both the OG and YG. Among OKG subjects, baseline muscle strength was lower in the osteoarthritic leg than in the total arthroplasty leg. Muscle strength improved significantly during follow-up in all groups; however, greater increases were observed in the osteoarthritic leg than in the total knee arthroplasty leg in OKG subjects. Greater increases were also seen in the osteoarthritic leg of OKG than in OG and YG. The greater muscle strength increase in the osteoarthritic leg reduced the interleg difference in muscle strength in OKG subjects, and resulted in similar posttraining muscle strength between OKG and OG in two of the three exercises analyzed. Greater exercise intensity progression was also observed in OKG subjects than in both OG and YG subjects. CONCLUSIONS: OKG subjects displayed greater relative muscle strength increases (osteoarthritic leg) than subjects in the YG, and greater relative exercise intensity progression than subjects in both OG and YG. These results suggest that resistance training is an effective method to counteract the lower-extremity strength deficits reported in older women with knee osteoarthritis and total knee arthroplasty

Exercise-induced improvements in cardiorespiratory fitness and heart rate response to exercise are impaired in overweight/obese postmenopausal women

OBJECTIVE: The purpose of this study was to compare the heart rate response to exercise and the exercise-induced improvements in muscle strength, cardiorespiratory fitness and heart rate response between normal-weight and overweight/obese postmenopausal women. METHODS: Sedentary women (n = 155) were divided into normal-weight (n = 79; BMI <25 kg/m²; 58.3 + 8.6 years) and overweight/obese (n = 76; BMI >25 kg/m²; 58.3 + 8.6 years) groups, and have their 1-repetition maximum strength (adjusted for body mass), cardiorespiratory fitness and heart rate response to a graded exercise test compared before and after 12 months of a three times-per-week exercise-training program. RESULTS: Overweight/obese women displayed decreased upper and lower extremity muscle strengths, decreased cardiorespiratory fitness, and lower peak and reserve heart rates compared to normal-weight women. After follow-up, both groups improved their upper (32.9% and 41.5% in normal-weight and overweight/obese women, respectively) and lower extremity(49.5% and 47.8% in normal-weight and overweight/obese women, respectively) muscle strength. However, only normal-weight women improved their cardiorespiratory fitness (6.6%) and recovery heart rate (5 bpm). Resting, reserve and peak heart rates did not change in either group. CONCLUSIONS: Overweight/obese women displayed impaired heart rate response to exercise. Both groups improved muscle strength, but only normal-weight women improved cardiorespiratory fitness and heart rate response to exercise. These results suggest that exercise-induced improvements in cardiorespiratory fitness and heart rate response to exercise may be impaired in overweight/obese postmenopausal women

An acoustic model to control an experimental slide flute

International audienceWe consider the problem of modeling and control of a slide flute: a kind of recorder without finger holes but ended by a piston to modify the length of the resonator. To control dynamical systems, it is important to elaborate a realistic model, so that control laws can be tested efficiently before they are implemented on real size prototypes. The dynamical model we have elaborated takes into account the coupling effects between the jet and the pipe which is a linear acoustic resonator. The jet is obtained by blowing through a flue channel and formed by flow separation at the flue exit, and finally directed towards a sharp edge, called the labium. A modal analysis is then performed using the linearized boundary conditions to compute the suitable blowing pressure and the suitable pipe length to obtain a desired pitch. This will constitute the "feedforward" part of our control algorithm. The Proportional-Integral feedback term is then elaborated to regulate the system to the desired set point, using the length of the piston measured by an encoder and the blowing pressure measured by a pressure sensor. First experimental results, obtained on a "mechatronic" prototype developed at Mines ParisTech will be presented

Conexões intermidiáticas entre transmissões audiovisuais ao vivo e redes sociais online: possibilidades e tensionamentos

Resumo &nbsp;No artigo discutimos as conexões intermidiáticas entre transmissões audiovisuais ao vivo e os debates alavancados nas redes sociais online, como o Twitter.&nbsp; Dialogando com diferentes autores e perspectivas conceituais (entre as quais a Teoria Ator-Rede), identificamos três tipos de conexão intermidiática: 1) iniciativas, como aplicativos de segunda tela, de canais de TV e outras empresas interessadas na convergência midiática; 2) debates online auto-organizados através de hashtags e dos quais emergem sistemas de resposta e controvérsias que resignificam as transmissões e 3) transmissões via streaming, como a Mídia Ninja, que se efetivam como uma enunciação coletiva que opera na lógica das redes sociotécnicas. As discussões têm como pano de fundo o tensionamento entre os modelos massivo e colaborativo de comunicação. &nbsp; Palavras-Chave:&nbsp;Convergência; Transmissão audiovisual ao vivo; Redes sociais online; Intermídia&nbsp; &nbsp; &nbsp; Resumen &nbsp;El artículo analiza las diferentes posibilidades de&nbsp;conexiones intermedia entre las transmisiones audiovisuales en directo y las interacciones impulsados por ellos en las redes sociales como Twitter. A través de una articulación de diferentes perspectivas conceptuales (como Teoría del Actor-Red), se identificaron tres tipos de conexiones intermedia. En primer lugar, las iniciativas, como aplicaciones de segunda pantalla, diseñado por canales de televisión y otras empresas interesadas en la convergencia de los medios. Segundo, debates autoorganizados usando hashtags a través de las cuales emergem controversias y comentarios críticos sobre los transmitions. Por último, streaming de transmisiones en vivo, como "Mídia Ninja", que, en colaboración con las redes sociales, ofrece una experiencia colectiva. &nbsp; Palabras clave:&nbsp;&nbsp;Convergencia; Transmisiones audiovisuales en directo; Redes sociales; Intermedia &nbsp; Abstract The article discusses the different possibilities of intermedia relations between live audiovisual transmissions and the interactions powered by them in online social networks, like Twitter. Articulating different conceptual perspectives (like Actor-Network Theory), we identified three kinds of intermedia connections. First, those executed by TV channels and other companies involved in media convergence (for example, “second screen” apps). Second, self-organized debates using hashtags and from which emerges controversies and critical feedback about the transmissions. Finally, streaming live transmissions, like Ninja Media, which, working together with online social networks, provides a collective experience. &nbsp; Keywords:&nbsp;Convergence; Audiovisual live transmissions; Online social networks; Intermedi

DISSIPATIVE BOUNDARY CONDITIONS FOR ONE-DIMENSIONAL NONLINEAR HYPERBOLIC SYSTEMS

International audienceWe give a new sufficient condition on the boundary conditions for the exponential stability of one-dimensional nonlinear hyperbolic systems on a bounded interval. Our proof relies on the construction of an explicit strict Lyapunov function. We compare our sufficient condition with other known sufficient conditions for nonlinear and linear one-dimensional hyperbolic systems

Coupled nonlinear vehicle control: Flatness-based setting with algebraic estimation techniques

International audienceA combined nonlinear longitudinal and lateral vehicle control is investigated. Flatness-based nonlinear control and new algebraic estimation techniques for noise removal and numerical differentiation are the main theoretical tools. An accurate automatic path-tracking via vehicle steering angle and driving/braking wheel torque is thus ensured. It combines the control of the lateral and longitudinal motions in order to track straight or curved trajectories and to perform a combined lane-keeping and steering control during critical driving situations such as obstacle avoidance, stop-and-go control, lane-change maneuvers or any other maneuvers. Promising results have been obtained with noisy experimental data, which were acquired by a laboratory vehicle with high dynamic loads and high lateral accelerations