Abstract:The validity and accuracy of a high-fidelity mechanistic multibody model of a vertical piano action mechanism is examined experimentally and through simulation. An overview of the theoretical and computational framework of this previously presented model is given first. A dynamically realistic benchtop prototype mechanism was constructed and driven by a mechanical actuator pressing the key. For simulations, a parameterization based on geometric and dynamic component properties and configuration is used; initia… Show more
“…Since the micromechanical contact model represents the real hysteresis curves corresponding to hammer-string contact point, the results are very similar to the ones presented in Ref. [20] which is based on a math-based contact model, i.e. curve-fitting to the experimental felt compression data.…”
Section: Simulation Results and Experimental Validationsupporting
confidence: 69%
“…the math-based model presented in Ref. [20] and the physics-based model proposed in this work, are shown in Figs. 13 and 14 for piano and forte inputs, respectively.…”
Section: Simulation Results and Experimental Validationmentioning
confidence: 99%
“…The obtained overall contact pressure/force between the bodies (calculated by adding the hysteresis part to the elastic part), along with the generalized coordinates and speeds is fed-back to the input for the next step of simulation. Two different inputs introduced by Masoudi et al [3,20] are utilized to simulate the vertical action, incorporating the micromechanical contact dynamic model developed in previous sections for the hammer-string interaction. The input profiles have been derived from force sensor data attached to the key front, which imitate the pianist finger force when playing a note with different intensities, i.e.…”
Section: Simulation Results and Experimental Validationmentioning
confidence: 99%
“…A precise description of the experimental procedure has been presented in another work by the authors [20]. Displacements of different bodies were measured by tracking marking points (shown in Fig.…”
“…The obtained force sensor data and position data from different cameras were synchronized. All the parameters for the components, including mass and geometrical properties, flexible components and string parameters, and contact points parameters were measured experimentally [20].…”
A micromechanical model of nonlinear hysteretic compression between interacting bodies of multibody systems, covered with fibrous structures, has been created and validated experimentally in this work. As an application, a multibody dynamic model of an upright piano action mechanism with felt-covered contacting bodies is considered, and the obtained results were verified using experiments. Felt, as a typical nonwoven fiber assembly, has been used in various contact surfaces of piano action mechanisms to transfer the force applied on the key to other components, smoothly and continuously. To keep the simulation time tractable in the mechanistic multibody dynamic model, interaction between felt-lined interfaces has to be simplified enough so that in each step of simulation time, contact forces can be calculated as a function of penetration depth between colliding objects. The developed micromechanical approach is capable of estimating nonlinear bulk response of felt in terms of microstructural parameters of the network, assuming a binomial distribution of the number of fiber contacts and bending of constituent fibers. Hysteresis is included based on a fiber-to-fiber friction approach, which generates a speed-independent response to compressive loading schemes, as has been observed in experiments. A computational algorithm is introduced to apply the sophisticated hysteretic micromechanical model to the multibody systems simulation, including transitions between loading-unloading stages.
“…Since the micromechanical contact model represents the real hysteresis curves corresponding to hammer-string contact point, the results are very similar to the ones presented in Ref. [20] which is based on a math-based contact model, i.e. curve-fitting to the experimental felt compression data.…”
Section: Simulation Results and Experimental Validationsupporting
confidence: 69%
“…the math-based model presented in Ref. [20] and the physics-based model proposed in this work, are shown in Figs. 13 and 14 for piano and forte inputs, respectively.…”
Section: Simulation Results and Experimental Validationmentioning
confidence: 99%
“…The obtained overall contact pressure/force between the bodies (calculated by adding the hysteresis part to the elastic part), along with the generalized coordinates and speeds is fed-back to the input for the next step of simulation. Two different inputs introduced by Masoudi et al [3,20] are utilized to simulate the vertical action, incorporating the micromechanical contact dynamic model developed in previous sections for the hammer-string interaction. The input profiles have been derived from force sensor data attached to the key front, which imitate the pianist finger force when playing a note with different intensities, i.e.…”
Section: Simulation Results and Experimental Validationmentioning
confidence: 99%
“…A precise description of the experimental procedure has been presented in another work by the authors [20]. Displacements of different bodies were measured by tracking marking points (shown in Fig.…”
“…The obtained force sensor data and position data from different cameras were synchronized. All the parameters for the components, including mass and geometrical properties, flexible components and string parameters, and contact points parameters were measured experimentally [20].…”
A micromechanical model of nonlinear hysteretic compression between interacting bodies of multibody systems, covered with fibrous structures, has been created and validated experimentally in this work. As an application, a multibody dynamic model of an upright piano action mechanism with felt-covered contacting bodies is considered, and the obtained results were verified using experiments. Felt, as a typical nonwoven fiber assembly, has been used in various contact surfaces of piano action mechanisms to transfer the force applied on the key to other components, smoothly and continuously. To keep the simulation time tractable in the mechanistic multibody dynamic model, interaction between felt-lined interfaces has to be simplified enough so that in each step of simulation time, contact forces can be calculated as a function of penetration depth between colliding objects. The developed micromechanical approach is capable of estimating nonlinear bulk response of felt in terms of microstructural parameters of the network, assuming a binomial distribution of the number of fiber contacts and bending of constituent fibers. Hysteresis is included based on a fiber-to-fiber friction approach, which generates a speed-independent response to compressive loading schemes, as has been observed in experiments. A computational algorithm is introduced to apply the sophisticated hysteretic micromechanical model to the multibody systems simulation, including transitions between loading-unloading stages.
International audienceModels with impact or dry friction, yielding discontinuous velocities or accelerations, have motivated research for appropriate numerical methods in the community of non-smooth dynamics. In this work, we apply such methods on the grand piano action. This multibody system has two properties of interest in terms of modelling and simulation: it is extremely sensitive to small misadjustements, and its functioning strongly relies on dry friction and stick-slip transitions—known to be crucial for the touch of the pianist. Using numerical methods of non-smooth contact dynamics, the non-smooth character of dry friction was conserved, in contrast to classical approaches based on regularization which additionally impose the somewhat arbitrary choice of a regularizing parameter. The use of such numerical method resulted in computations about a few hundred times faster than those reported in recent literature. For the first time, the presented predictions of the piano action's simulations are forces (in particular, the reaction force of the key on the pianist's finger), instead of displacements which filter out most of the dynamical subtleties of the mechanism. The comparisons between measured and simulated forces in response to a given motion are successful, which constitutes an excellent validation of the model, from the dynamical and the haptic points of view. Altogether, numerical methods for non-smooth contact dynamics applied to a non-smooth model of the piano action proved to be both accurate and efficient, opening doors to industrial and haptic applications of sensitive multibody systems for which dry friction is essential.
Simulation-based videos
Simulations of a keystroke:
Comparisons between simulations and experiments:
Experimental and educational videos
High-speed captures of the piano key mechanism (Left: piano keystroke. Right: forte keystroke.) [A. Thorin and X. Boutillon, LMS@École polytechnique / CEA LIST]
Explanations on how the mechanism works [A. Thorin based on O. Remez's drawing]
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