Second-order LuGre friction model

A second-order LuGre friction model is presented which can be viewed as an extension of the well known LuGre friction model. This model is based on a dynamic extension, which can be seen as an extra dynamic to capture some kind of periodic motion produced by the bristles in motion. The additional dynamic can be viewed as an internal disturbance due to the vibration associated with the use of motors. Our model can capture the friction phenomena of the original LuGre friction model and presents two new behaviors, one is the multi-loop behavior in the hysteresis curve when velocity is varied during unidirectional motion, and the other, in the presliding motion curve of friction force versus displacement in the spring regime, where two jumps appear.Postprint (published version

Recreating the Amoeba Violin Using Physical Modeling and Augmented Reality

The Amoeba violin is a bowed string instrument present at the Danish Music Museum in Copenhagen. The instrument is not played anymore due to its unpleasant sonorities and uncomfortable shape. In this paper we recreate the Amoeba violin using extended reality technologies and sound synthesis by physical models. We design and evaluate two applications that can be used either at the museum (augmented reality version) or at home (desktop version) to learn about the history of the instrument and its sonorities. The app was created for the Danish Music Museum, Musikmuseet, located in Copenhagen, in response to the demand for reduced contact of shared surfaces and official calls to stay indoors that followed the COVID-19 outbreak in 2020. User testing on both versions shows that they both are considered easy-to-access and educative, however the AR version was more favoured overall

Novel Design of a Model Reference Adaptive Controller for Soft Tissue Operations

Model Reference Adaptive Controllers (MRAC) have dual functionality: besides guaranteeing precise trajectory track- ing of the controlled system, they have to provide an “external control loop” with the illusion that it controls a physical system of prescribed dynamic properties, i.e., the “reference system”. The MRACs are designed traditionally by Lyapunov’s 2 nd method that is mathematically complicated, requiring strong skills from the designer. Adaptive controllers alternatively designed by the use of Robust Fixed Point Transformations (RFPT) operate according to Banach’s Fixed Point Theorem , and are normally simple iterative constructions that also have a standard variant for MRAC design. This controller assumes a single actuator that is driven adaptively. Master–Slave Systems form a distinct class of practical applications, in which two arms—the master and the slave—operate simultaneously. The movement of the master must be tracked precisely by the slave in spite of the quite different forces exerted by them. In the present paper, a soft tissue-cutting operation by a master–slave structure is simulated. The master arm has a simple torque–reference friction model, and is driven by the surgeon. The obtained master arm trajectory has to be precisely tracked by the electric DC motor driven slave system, which is in dynamic interaction with the actual tissue under operation. It is shown via simulations that the RFPT-based design can efficiently solve such tasks without considerable mathematical complexity

Does It Ping or Pong? Auditory and Tactile Classification of Materials by Bouncing Events

Two experiments studied the role of impact sounds and vibrations in classification of materials. The task consisted of feeling on an actuated surface and listening through headphones to the recorded feedback of a ping-pong ball hitting three flat objects respectively made of wood, plastic, and metal, and then identifying their material. In Experiment 1, sounds and vibrations were recorded by keeping the objects in mechanical isolation. In Experiment 2, recordings were taken while the same objects stood on a table, causing their resonances to fade faster due to mechanical coupling with the support. A control experiment, where participants listened to and touched the real objects in mechanical isolation, showed high accuracy of classification from either sounds (90% correct) or vibrations (67% correct). Classification of reproduced bounces in Experiments 1 and 2 was less precise. In both experiments, the main effect of material was statistically significant; conversely, the main effect of modality (auditory or tactile) was significant only in the control. Identification of plastic and especially metal was less accurate in Experiment 2, suggesting that participants, when possible, classified materials by longer resonance tails. Audio-tactile summation of classification accuracy was found, suggesting that multisensory integration influences the perception of materials. Such results have prospective application to the nonvisual design of virtual buttons, which is the object of our current research