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Mark Hedrick,Lauren Charles,Nicole Drakopoulos Street 대한이비인후과학회 2015 Clinical and Experimental Otorhinolaryngology Vol.8 No.1
Objectives. To determine the influence of hearing loss on perception of vowel slices. Methods. Fourteen listeners aged 20–27 participated; ten (6 males) had hearing within normal limits and four (3 males) had moderate-severe sensorineural hearing loss (SNHL). Stimuli were six naturally-produced words consisting of the vowels /i a u æ ɛ ʌ/ in a /b V b/ context. Each word was presented as a whole and in eight slices: the initial transition, one half and one fourth of initial transition, full central vowel, one-half central vowel, ending transition, one half and one fourth of ending transition. Each of the 54 stimuli was presented 10 times at 70 dB SPL (sound press level); listeners were asked to identify the word. Stimuli were shaped using signal processing software for the listeners with SNHL to mimic gain provided by an appropriately-fitting hearing aid. Results. Listeners with SNHL had a steeper rate of decreasing vowel identification with decreasing slice duration as compared to listeners with normal hearing, and the listeners with SNHL showed different patterns of vowel identification across vowels when compared to listeners with normal hearing. Conclusion. Abnormal temporal integration is likely affecting vowel identification for listeners with SNHL, which in turn affects vowel internal representation at different levels of the auditory system.
Dynamic Surface Control and Its Application to Lateral Vehicle Control
Song, Bongsob,Hedrick, J. Karl,Kang, Yeonsik Hindawi Limited 2014 Mathematical problems in engineering Vol.2014 No.-
<P>This paper extends the design and analysis methodology of dynamic surface control (DSC) in Song and Hedrick, 2011, for a more general class of nonlinear systems. When rotational mechanical systems such as lateral vehicle control and robot control are considered for applications, sinusoidal functions are easily included in the equation of motions. If such a sinusoidal function is used as a forcing term for DSC, the stability analysis faces the difficulty due to highly nonlinear functions resulting from the low-pass filter dynamics. With modification of input variables to the filter dynamics, the burden of mathematical analysis can be reduced and stability conditions in linear matrix inequality form to guarantee the quadratic stability via DSC are derived for the given class of nonlinear systems. Finally, the proposed design and analysis approach are applied to lateral vehicle control for forward automated driving and backward parallel parking at a low speed as well as an illustrative example.</P>
Linear Tracking for a Fixed-Wing UAV Using Nonlinear Model Predictive Control
Yeonsik Kang,Hedrick, J.K. IEEE 2009 IEEE transactions on control systems technology Vol.17 No.5
<P>In this paper, a nonlinear model predictive control (NMPC) is used to design a high-level controller for a fixed-wing unmanned aerial vehicle (UAV). Given the kinematic model of the UAV dynamics, which is used as a model of the UAV with low-level autopilot avionics, the control objective of the NMPC is determined to track a desired line. After the error dynamics are derived, the problem of tracking a desired line is transformed into a problem of regulating the error from the desired line. A stability analysis follows to provide the conditions that can assure the closed-loop stability of the designed high-level NMPC. Furthermore, the control objective is extended to track adjoined multiple line segments. The simulation results demonstrate that the UAV controlled by the NMPC converged rapidly with a small overshoot. The performance of the NMPC was also verified through realistic ¿hardware in the loop simulation.¿</P>
방정화,Mark Hedrick,Deborah von Hapsburg 대한이비인후과학회 2014 Clinical and Experimental Otorhinolaryngology Vol.7 No.4
Objectives. To determine how normal-hearing adults (NHA), normal-hearing children (NHC) and children wearing cochle- ar implants (CI) differ in the perceptual weight given cues for fricative consonants (having a comparatively long static cue and short transition cue) versus stop consonants (having a comparatively short static cue and long transition cue). Methods. Ten NHA, eleven 5- to 8-year-old NHC and eight 5- to 8-year-old children wearing CI were participated. Frica- tive /su/-/∫u/ and stop /pu/-/tu/ continua were constructed by varying the fricative/burst cue and the F2 onset transi- tion cue. A quantitative method of analysis (analysis of variance model) was used to determine cue weighting and measure cue interaction within groups. Results. For the fricative consonant, all groups gave more weight to the frication spectral cue than to the formant transition. For the voiceless stop consonant, all groups gave more weight to the transition cue than to the burst cue. The CI group showed similar cue weighting strategies to age-matched NHC, but integration of cues by the CI group was not significant. Conclusion. All groups favored the longer-duration cue in both continua to make phonemic judgments. Additionally, devel- opmental patterns across groups were evident. Results of the current study may be used to guide development of CI devices and in efforts to improve speech and language of children wearing CIs.
EMERGENCY BRAKING CONTROL OF A PLATOON USING STRING STABLE CONTROLLER
Kang, Y.,Hedrick, J.K. The Korean Society of Automotive Engineers 2004 International journal of automotive technology Vol.5 No.2
In this paper, a safe control strategy is considered in the situation when a platoon of vehicles need to decelerate rapidly. When the vehicles ate spaced closely, it is known that the reference information should be transmitted to the whole platoon to minimize the undesirable effects of small leader disturbances. However, the vehicle control should also depend on the preceding vehicle position to maintain the desired distance. Tracking the preceding vehicle position can lead to amplification of the control input along the following vehicles, therefore the vehicles in the rearward generally exert larger maximum control input than the vehicles in the front. The theoretical bounds for the $i^{th}$ vehicle control input are calculated using a linear vehicle and controller model. In the simple illustrative example, the designed controller maintains string stability, and the control inputs of the following vehicles stay within bounds.