The Experts below are selected from a list of 69 Experts worldwide ranked by ideXlab platform

G.a. Pratt - One of the best experts on this subject based on the ideXlab platform.

  • force controllable hydro elastic actuator
    International Conference on Robotics and Automation, 2000
    Co-Authors: D W Robinson, G.a. Pratt
    Abstract:

    We present a hydro-elastic actuator that has a linear spring intentionally placed in series between the hydraulic piston and actuator output. The spring strain is measured for an accurate estimate of force. This measurement alone is used in PI feedback to control the force in the actuator. The spring allows for high force fidelity, good force control, minimum impedance, and large dynamic range. A third order linear actuator model is divided into two fundamental cases: fixed load-high force (Forward Transfer Function), and free load-zero force (impedance). These two equations completely describe the linear characteristics of the actuator. This model is presented with dimensional analysis to allow for generalization. A prototype actuator that demonstrates force control and low impedance is also presented. Dynamic analysis of the prototype actuator correlates well with the linear mathematical model.

  • Series elastic actuator development for a biomimetic walking robot
    1999 IEEE ASME International Conference on Advanced Intelligent Mechatronics (Cat. No.99TH8399), 1999
    Co-Authors: D W Robinson, D.j. Paluska, J E Pratt, G.a. Pratt
    Abstract:

    Series elastic actuators have linear springs intentionally placed in series between the motor and actuator output. The spring strain is measured to get an accurate estimate of force. A second order linear actuator model is broken into two fundamental cases: fixed load-high force (Forward Transfer Function), and free load-zero force (impedance). This model is presented with dimensional analysis and extends previous linear models to include friction. Using the model and dimensionless groups, we examine nonlinear effects of motor saturation as it relates to large force bandwidth and nonlinear friction effects such as stiction. The model also helps to clarify how the springs help and hinder the operation of the actuator. The information gained from the model helps to create a design procedure for series elastic actuators. Particular emphasis is placed on choosing the spring constant for the elastic element

Anthony W Gummer - One of the best experts on this subject based on the ideXlab platform.

  • Forward and reverse Transfer Functions of the middle ear based on pressure and velocity DPOAEs with implications for differential hearing diagnosis.
    Hearing research, 2011
    Co-Authors: Ernst Dalhoff, Diana Turcanu, Anthony W Gummer
    Abstract:

    Recently it was shown that distortion product otoacoustic emissions (DPOAEs) can be measured as vibration of the human tympanic membrane in vivo, and proposed to use these vibration DPOAEs to support a differential diagnosis of middle-ear and cochlear pathologies. Here, we investigate how the reverse Transfer Function (r-TF), defined as the ratio of DPOAE-velocity of the umbo to DPOAE-pressure in the ear canal, can be used to diagnose the state of the middle ear. Anaesthetized guinea pigs served as the experimental animal. Sound was delivered free-field and the vibration of the umbo measured with a laser Doppler vibrometer (LDV). Sound pressure was measured 2-3 mm from the tympanic membrane with a probe-tube microphone. The Forward Transfer Function (f-TF) of umbo velocity relative to ear-canal pressure was obtained by stimulating with multi-tone pressure. The r-TF was assembled from DPOAE components generated in response to acoustic stimulation with two stimulus tones of frequencies f(1) and f(2); f(2)/f(1) was constant at 1.2. The r-TF was plotted as Function of DPOAE frequencies; they ranged from 1.7 kHz to 23 kHz. The r-TF showed a characteristic shape with an anti-resonance around 8 kHz as its most salient feature. The data were interpreted with the aid of a middle-ear transmission-line model taken from the literature for the cat and adapted to the guinea pig. Parameters were estimated with a three-step fitting algorithm. Importantly, the r-TF is governed by only half of the 15 independent, free parameters of the model. The parameters estimated from the r-TF were used to estimate the other half of the parameters from the f-TF. The use of r-TF data - in addition to f-TF data - allowed robust estimates of the middle-ear parameters to be obtained. The results highlight the potential of using vibration DPOAEs for ascertaining the Functionality of the middle ear and, therefore, for supporting a differential diagnosis of middle-ear and cochlear pathologies.

D W Robinson - One of the best experts on this subject based on the ideXlab platform.

  • force controllable hydro elastic actuator
    International Conference on Robotics and Automation, 2000
    Co-Authors: D W Robinson, G.a. Pratt
    Abstract:

    We present a hydro-elastic actuator that has a linear spring intentionally placed in series between the hydraulic piston and actuator output. The spring strain is measured for an accurate estimate of force. This measurement alone is used in PI feedback to control the force in the actuator. The spring allows for high force fidelity, good force control, minimum impedance, and large dynamic range. A third order linear actuator model is divided into two fundamental cases: fixed load-high force (Forward Transfer Function), and free load-zero force (impedance). These two equations completely describe the linear characteristics of the actuator. This model is presented with dimensional analysis to allow for generalization. A prototype actuator that demonstrates force control and low impedance is also presented. Dynamic analysis of the prototype actuator correlates well with the linear mathematical model.

  • Series elastic actuator development for a biomimetic walking robot
    1999 IEEE ASME International Conference on Advanced Intelligent Mechatronics (Cat. No.99TH8399), 1999
    Co-Authors: D W Robinson, D.j. Paluska, J E Pratt, G.a. Pratt
    Abstract:

    Series elastic actuators have linear springs intentionally placed in series between the motor and actuator output. The spring strain is measured to get an accurate estimate of force. A second order linear actuator model is broken into two fundamental cases: fixed load-high force (Forward Transfer Function), and free load-zero force (impedance). This model is presented with dimensional analysis and extends previous linear models to include friction. Using the model and dimensionless groups, we examine nonlinear effects of motor saturation as it relates to large force bandwidth and nonlinear friction effects such as stiction. The model also helps to clarify how the springs help and hinder the operation of the actuator. The information gained from the model helps to create a design procedure for series elastic actuators. Particular emphasis is placed on choosing the spring constant for the elastic element

Ernst Dalhoff - One of the best experts on this subject based on the ideXlab platform.

  • Forward and reverse Transfer Functions of the middle ear based on pressure and velocity DPOAEs with implications for differential hearing diagnosis.
    Hearing research, 2011
    Co-Authors: Ernst Dalhoff, Diana Turcanu, Anthony W Gummer
    Abstract:

    Recently it was shown that distortion product otoacoustic emissions (DPOAEs) can be measured as vibration of the human tympanic membrane in vivo, and proposed to use these vibration DPOAEs to support a differential diagnosis of middle-ear and cochlear pathologies. Here, we investigate how the reverse Transfer Function (r-TF), defined as the ratio of DPOAE-velocity of the umbo to DPOAE-pressure in the ear canal, can be used to diagnose the state of the middle ear. Anaesthetized guinea pigs served as the experimental animal. Sound was delivered free-field and the vibration of the umbo measured with a laser Doppler vibrometer (LDV). Sound pressure was measured 2-3 mm from the tympanic membrane with a probe-tube microphone. The Forward Transfer Function (f-TF) of umbo velocity relative to ear-canal pressure was obtained by stimulating with multi-tone pressure. The r-TF was assembled from DPOAE components generated in response to acoustic stimulation with two stimulus tones of frequencies f(1) and f(2); f(2)/f(1) was constant at 1.2. The r-TF was plotted as Function of DPOAE frequencies; they ranged from 1.7 kHz to 23 kHz. The r-TF showed a characteristic shape with an anti-resonance around 8 kHz as its most salient feature. The data were interpreted with the aid of a middle-ear transmission-line model taken from the literature for the cat and adapted to the guinea pig. Parameters were estimated with a three-step fitting algorithm. Importantly, the r-TF is governed by only half of the 15 independent, free parameters of the model. The parameters estimated from the r-TF were used to estimate the other half of the parameters from the f-TF. The use of r-TF data - in addition to f-TF data - allowed robust estimates of the middle-ear parameters to be obtained. The results highlight the potential of using vibration DPOAEs for ascertaining the Functionality of the middle ear and, therefore, for supporting a differential diagnosis of middle-ear and cochlear pathologies.

Christopher A. Shera - One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous measurement of middle-ear input impedance and Forward/reverse transmission in cat
    The Journal of the Acoustical Society of America, 2004
    Co-Authors: Susan E. Voss, Christopher A. Shera
    Abstract:

    Reported here is a technique for measuring Forward and reverse middle-ear transmission that exploits distortion-product otoacoustic emissions (DPOAEs) to drive the middle ear "in reverse" without opening the inner ear. The technique allows measurement of DPOAEs, middle-ear input impedance, and Forward and reverse middle-ear Transfer Functions in the same animal. Intermodulation distortion in the cochlea generates a DPOAE at frequency 2f1-f2 measurable in both ear-canal pressure and the velocity of the stapes. The Forward Transfer Function is computed from stapes velocities and corresponding ear-canal pressures measured at the two primary frequencies; the reverse Transfer Function is computed from velocity and pressure measurements at the DPOAE frequency. Middle-ear input impedance is computed from ear-canal pressure measurements and the measured Thevenin equivalent of the sound-delivery system. The technique was applied to measure middle-ear characteristics in anesthetized cats with widely opened middle-ear cavities (0.2-10 kHz). Stapes velocity was measured at the incudo-stapedial joint. Results on five animals are reported and compared with a published middle-ear model. The measured Forward Transfer Functions and input impedances generally agree with previous measurements, and all measurements agree qualitatively with model predictions. The reverse Transfer Function is shown to depend on the acoustic load in the ear canal, and the measurements are used to compute the round-trip middle-ear gain and delay. Finally, the measurements are used to estimate the parameters of a two-port Transfer-matrix description of the cat middle ear.

  • Simultaneous measurement of middle-ear input impedance and Forward/reverse transmission in cat.
    The Journal of the Acoustical Society of America, 2004
    Co-Authors: Susan E. Voss, Christopher A. Shera
    Abstract:

    Reported here is a technique for measuring Forward and reverse middle-ear transmission that exploits distortion-product otoacoustic emissions (DPOAEs) to drive the middle ear "in reverse" without opening the inner ear. The technique allows measurement of DPOAEs, middle-ear input impedance, and Forward and reverse middle-ear Transfer Functions in the same animal. Intermodulation distortion in the cochlea generates a DPOAE at frequency 2f1-f2 measurable in both ear-canal pressure and the velocity of the stapes. The Forward Transfer Function is computed from stapes velocities and corresponding ear-canal pressures measured at the two primary frequencies; the reverse Transfer Function is computed from velocity and pressure measurements at the DPOAE frequency. Middle-ear input impedance is computed from ear-canal pressure measurements and the measured Thévenin equivalent of the sound-delivery system. The technique was applied to measure middle-ear characteristics in anesthetized cats with widely opened middle-ear cavities (0.2-10 kHz). Stapes velocity was measured at the incudo-stapedial joint. Results on five animals are reported and compared with a published middle-ear model. The measured Forward Transfer Functions and input impedances generally agree with previous measurements, and all measurements agree qualitatively with model predictions. The reverse Transfer Function is shown to depend on the acoustic load in the ear canal, and the measurements are used to compute the round-trip middle-ear gain and delay. Finally, the measurements are used to estimate the parameters of a two-port Transfer-matrix description of the cat middle ear.