Timothy Hsu

New Command Shaping Methods for Reduced Vibration of a Suspended Payload With Constrained Trolley Motion

In manufacturing environments, a common task is to quickly move a suspended payload point-to-point along a fixed overhead conveyor track without inducing significant payload vibration. Recent research in command shaping has shown remarkably effective ways to reduce the swing of a suspended payload providing the motion of the trolley is not constrained. However, the development of a command shaper where the trajectory of the trolley is constrained to follow a fixed curvilinear path has not been explored. This paper will present the development of a simple feedforward command shaper for fast, low vibration, point-to-point movement of a payload suspended from a trolley constrained to follow a fixed generalized path. The command shaping method involves modifying the command signal by convolving it with a series of impulses. Prior work has suggested command shaping to be very effective for fast, low-vibration movement of flexible systems. In this paper, command shaping methods are applied to an overhead conveyor system constrained to move along a fixed curvilinear path. Two new command shapers are presented for canceling payload vibration induced by motion of the trolley along the path. The designed Tangential Vibration (TV) shaper reduces payload vibrations induced by tangential accelerations of the trolley along the path, while the Centripetal-Tangential Vibration (CTV) shaper reduces vibrations induced by both tangential and centripetal accelerations. A key result of this study is that a command shaper having at least three impulses is required to yield zero residual vibration for motion along a curvilinear path. A simple pendulum payload attached to an actual small-scale overhead trolley following a constrained path is used to evaluate the performance of the designed command shapers. It is shown that the designed shapers significantly reduce payload swing compared to unshaped performance. An experimental sensitivity analysis shows the designed shapers are robust to system modeling errors and variations in path parameters.Copyright

Relating patient physiology to the hospital sound environment.

Sounds in hospital wards have previously been linked to physiologic changes in patients including sleep disturbance, variation in vital signs, and impaired pain management. However, relationships between sound measurements and variations in physiologic measures remain somewhat unclear. This presentation will discuss a pilot study that focuses on the relationships between acoustic measurements and patient physiology in a Swedish medical‐surgical intensive care unit. Sound measurements as well as physiologic measures including heart rate, oxygen saturation, respiratory rate, and blood pressure were recorded simultaneously for 24‐h periods in 18 patients. Several different analyzes were performed to assess the relationships between the acoustic results and the patients’ physiological measurements. The data demonstrated a statistically significant relationship between the recorded physiological responses and acoustic measurements. The results build upon previous results to further elucidate the relationships ...

A diffuser language: Designing quadratic residue diffuser arrays with shape grammars

This paper presents research on a rule-based approach to designing creative acoustic diffuser arrays. A shape grammar-influenced design method is specified that uses shape rules to recursively design arrays of quadratic residue diffusers (QRD) in a way that is neither mechanical nor deterministic. Shape grammar-based generative systems have already been shown to be capable of being used in architecture and engineering to create languages of functional objects but have not yet been extended into the realm of acoustics. The grammar presented by this paper produces a QRD-based acoustic diffusion language that breaks habits in QRD deploying techniques, which is lacking outside of using known equations that give known forms. The grammar can include different design frequencies and open the possibilities of different and non-uniform, intentional diffusion treatment. This paper will specify and demonstrate the formation rules, and discuss on how in combination with material specifications, this design method can...

Effect of acoustic computer model precision on auralization perception

Most modern acoustic simulation programs use geometric acoustics to auralize the sound within a space, providing acceptable results in a relatively quick manner. Still, because of the limitations of geometric acoustics in computer simulations, it is of particular interest to investigate the relationship between model geometry, simulation parameters, and the listener’s perception of auralizations created from iterations of an acoustic model. In the context of this study, differences between auralizations were investigated from a perceptual standpoint, using the subjective judgment of listeners. A modified version of the Multiple Stimulus test with Hidden Reference and Anchor methodology was used to define a threshold at which an increase in model precision no longer results in perceived differences between auralizations, aiming to inform efficient modeling practices in practical applications. Acoustic simulations were performed on a set of speech and music venues modeled at incremental geometrical precisio...

Navigating and developing acoustics research and curriculum within the Georgia Tech Center for Music Technology

Acoustics at the Georgia Institute of Technology has primarily been based within mechanical engineering with various other faculty spread throughout the university. Within the last decade, the School of Music has developed an internationally recognized graduate degree program and research center in music technology. Since winning the Student Paper Award, my professional career has started in a unique faculty position within the School of Music at Georgia Tech, where my responsibilities are split between being an ensemble/choral conductor and an active member of the Center for Music Technology. One of the recent challenges is the development of an innovative undergraduate curriculum model that fuses music fundamentals, music technology, general musicianship, and engineering/computer science. At the graduate level, new coursework I have created has included a musical acoustics course for music technologists and a historical acoustics and modeling course. Additionally, developing a research track of acoustic...

Real-time tonal self-adaptive tuning for electronic instruments

A fixed tuning system cannot achieve just intonation on all intervals. A better approximation of just intonation is possible if the frequencies of notes are allowed to vary. Adaptive tuning is a class of methods that adjusts the frequencies of notes dynamically in order to maximize musical consonance. However, finding the optimal frequencies of notes directly based on some definition of consonance has shown to be difficult and computationally expensive. Instead, this paper proposes that the current key of the music is both a good summary of past notes and a good prediction of future notes, which can facilitate adaptive tuning. A method is proposed that uses a hidden Markov model to detect the current key of the music and compute optimal frequencies of notes based on the current key. In addition, a specialized online machine learning method that enforces symmetry among diatonic keys is presented, which can potentially adapt the model for different genres of music. The algorithm can operate in real time, is...

Psychoacoustic measures and their relationship to patient physiology in an intensive care unit.

Many researchers have attempted to characterize the soundscape of hospital wards using traditional acoustic metrics. These traditional metrics, such as average sound level, are readily measured using sound level meters and have been the primary results reported in previous studies. However, it has been shown that these traditional metrics may be insufficient in fully characterizing the wards. This is a continuation of a larger study that evaluates the relationship between hospital soundscape and the effects on the hospital occupants in a medical‐surgical intensive care unit. The previous study in this series showed statistically significant relationships between patient physiology and the traditional sound level meter metrics. This current study aims to expand beyond traditional sound level meters and use digital recordings to describe the ICU rooms with psychoacoustics metrics. Thus, a comprehensive catalog of these metrics for ICUs is compiled and presented. In addition to descriptive results with these...

Comparing novel absorptive treatments in operating rooms.

Hospital noise levels have been rising over the past several decades, and there have been few viable noise control solutions. The hospital environment can have special health requirements due to strict infectious control criteria. In order to meet these requirements, a novel absorbing panel was developed for a previous study in this series and installed in hematological intensive care units at the Johns Hopkins University Hospital Weinberg Building. This current study focuses on the impact of installing the panels in an operating room in the Johns Hopkins University Hospital. The impacts of the addition of sound absorbing materials in these operating rooms were analyzed both acoustically and perceptually. Sound level recordings and reverberation times were measured before and after the installation of the absorbing panels. Comparisons of these acoustic measurements will be presented. Additionally, a before/after questionnaire was administered to the operating room medical staff. Statistically significant ...

Evaluating the intensive care unit soundscape.

The intermittent sounds in hospital wards may induce arousal among patients leading to responses such as annoyance, sleep disturbance, and cardio‐vascular reactions. The sound environment as a whole may also affect the efficiency and general health among the staff. A series of studies are being conducted by the authors to evaluate the modern hospital soundscape including occupant response. Collaborations between engineering and medicine are being utilized to assess the soundscape from both a quantitative and qualitative standpoint. This talk will focus on soundscape evaluations of intensive care units. This includes a pilot study performed in a medical‐surgical intensive care unit (ICU) of a Swedish hospital. Patients were monitored for 24 hours during their stay in the ICU and both acoustic and physiological data were simultaneously recorded. Additionally, the staff wore dosimeters and completed perception questionnaires. The methodology and analyses of these detailed acoustic measurements and preliminar...