Design of an active controller for the enhancement of the sound quality of a classical violin

The structural design of classical musical instruments has a century long tradition. The violin is a typical example of an instrument of which the mechanical construction is based on this tradition. However, even though nowadays all classical violins look almost identical, the sound quality among them varies strongly. This sound quality is the key-property in determining the value of a classical violin. The fact that the design of the classical violin has not evolved much over the past decades indicates that an optimum has been obtained within the reach of the classical mechanical construction with purely passive acoustical sound generation. The aim of this paper is to study the applicability of an active controller for the enhancement of the sound quality generated by the classical violin. More in particular, this study envisages a modular controller which does not affect the classical mechanical construction of the violin. The first section of the paper briefly discusses the typical design aspects infiuencing the acoustical properties of the violin, and an objective measurement technique for violin sound quality. Next, the design of the controller is discussed. A preliminary structural modal analysis on a classical violin forms the basis for the choice of the placement of the sensors and actuators on the structure. An optimal controller is defined based on a control objective function incorporating the objectively determined sound quality indicators. Finally, the actively controlled violin is validated experimentally.status: publishe

Integrating structural and input design of a 2-DOF high-speed parallel manipulator: A flexible model-based approach

This paper discusses the integrated design of parallel manipulators, which exhibit varying dynamics. This characteristic affects the machine stability and performance. The design methodology consists of four main steps: (i) the system modeling using flexible multibody technique, (ii) the synthesis of reduced-order models suitable for control design, (iii) the systematic flexible model-based input signal design, and (iv) the evaluation of some possible machine designs. The novelty in this methodology is to take structural flexibilities into consideration during the input signal design; therefore, enhancing the standard design process which mainly considers rigid bodies dynamics. The potential of the proposed strategy is exploited for the design evaluation of a two degree-of-freedom high-speed parallel manipulator. The results are experimentally validated. (C) 2010 Elsevier Ltd. All rights reserved.EU[IP 011815]K.U. LeuvenCAPES, Brazilian Foundation Coordination for the Improvement of Higher Education Personne

LPV modelling and identification: An overview

The current state-of-the-art in the fields of control-oriented LPV modelling and LPV system identification is surveyed and the potential synergies between the two research areas are highlighted and discussed. Indeed, a number of methods and tools for the development of LPV models from nonlinear systems and for the identification of black-box LPV models from input/output data have been derived, in a rather independent way, in different research communities. The relative merits of analytical and experimental methods for the derivation of LPV models, as well as possible combinations of the two approaches, are analysed and eventually evaluated on a case study based on the modelling of a thermo-fluid system. © 2013 Springer-Verlag

Combining Stressors That Individually Impede Long-Term Memory Blocks All Memory Processes

The effects of stress on memory are typically assessed individually; however, in reality different stressors are often experienced simultaneously. Here we determined the effect that two environmentally relevant stressors, crowding and low calcium availability, have on memory and neural activity following operant conditioning of aerial respiration in the pond snail, Lymnaea stagnalis. We measured aerial breathing behaviour and activity of a neuron necessary for memory formation, right pedal dorsal 1 (RPeD1), in the central pattern generator (CPG) that drives aerial respiration in untrained animals, and assessed how these traits changed following training. In naïve animals both crowding and combined stressors significantly depressed burst activity in RPeD1 which correlated with a depression in aerial breathing behaviour, whereas low calcium availability had no effect on RPeD1 activity. Following training, changes in burst activity in RPeD1 correlated with behavioural changes, decreasing relative to their naïve state at 3 h and 24 h in control conditions when both intermediate-term memory (ITM: 3 h) and long-term memory (LTM: 24 h) are formed, at 3 h but not 24 h when exposed to individual stressors when only ITM is formed, and did not change in combined stressors (i.e. when no memory is formed). Additionally, we also found that Lymnaea formed short-term memory (STM: 10 min) in the presence of individual stressors or under control conditions, but failed to do so in the presence of combined stressors. Our data demonstrate that by combining stressors that individually block LTM only we can block all memory processes. Therefore the effects of two stressors with similar individual affects on memory phenotype may be additive when experienced in combination