The Journal of the Acoustical Society of America, 2000
The Rayleigh–Ritz method is used to model a smart composite plate and the piezoelectric patches a... more The Rayleigh–Ritz method is used to model a smart composite plate and the piezoelectric patches attached to it. Classical plate theory is used to model the composite plate and electroelastic theory is used to model the segmented piezoelectric patches. Eigenfunctions of a clamped–clamped beam are used as the Ritz functions for the panel and the rigid cavity modes are used to model the acoustic cavity. The dynamic equations of motion for the coupled smart panel-cavity system are derived using Hamilton’s principle. The forcing term due to the cavity acoustic pressure is determined by using virtual work considerations. Five collocated pairs of actuator/sensor pairs are attached to the plate at a predetermined placement scheme. A (multi-input–multi-output) MIMO controller is designed for the coupled vibroacoustic system. The output feedback controller is then employed to emulate the optimal controller by solving the Riccati equations. The performance of the control system in reducing the...
The Journal of the Acoustical Society of America, 1994
Control of noise radiated into an enclosure from an external source is of interest in several app... more Control of noise radiated into an enclosure from an external source is of interest in several applications. The noise is transmitted into the enclosure by the induced structural vibrations of the walls of the enclosure. An active control experiment using discrete piezoelectric sensors and actuators is proposed to sense and control the structure-borne sound. A sound level meter and error microphone are used to measure the acoustic field intensity inside the enclosure with and without control. The results of this experiment will define the feasibility of applying active control methods to larger enclosures such as office partitions, passenger compartments of vehicles, control rooms in factory floors, hospital rooms, and apartments in crowded urban areas.
The Journal of the Acoustical Society of America, 1991
Using piezoelectric sensors and actuators, the vibrating motions of a thin plate could be effecti... more Using piezoelectric sensors and actuators, the vibrating motions of a thin plate could be effectively controlled. Several pieces of Unimorph PZT (lead-titanate-zirconate) were optimally attached on the both sides of a clamped square plate. A series of active vibration control experiments has been tried with different types of control algorithms. Even though the system structure is stiff enough because of the clamped edges, effective vibration control could be implemented with the large electromechanical coupling constant of PZT and well-selected positions of sensors and actuators. Here, particular attention has been paid to several lower-frequency modes. To take advantage of the features of a digital system such as flexibility of the control program and increased logic capability, a microcomputer and a data acquisition board were used to obtain a digital controller.
The Journal of the Acoustical Society of America, 1990
High-frequency air-coupled ultrasonic transducers are used in industrial applications for detecti... more High-frequency air-coupled ultrasonic transducers are used in industrial applications for detecting or ranging with high resolution. The improvement of the coupling between PZT and air is of importance for the transducer performance. Unfortunately, it is difficult to find a material with proper acoustical impedance and small attenuation at high frequency for matching layers. Theoretical analysis and experimental investigation showed that a layer made of a material with an impedance close to that of water is able to improve this matching significantly. Three air-coupled transducers at frequency ranges of 0.5 to 2.0 MHz were fabricated. Reasonable sensitivities and bandwidth were obtained. The variation of performances of the transducers with the thickness of the layer were investigated theoretically and experimentally.
The Journal of the Acoustical Society of America, 2000
The Rayleigh–Ritz method is used to model a smart composite plate and the piezoelectric patches a... more The Rayleigh–Ritz method is used to model a smart composite plate and the piezoelectric patches attached to it. Classical plate theory is used to model the composite plate and electroelastic theory is used to model the segmented piezoelectric patches. Eigenfunctions of a clamped–clamped beam are used as the Ritz functions for the panel and the rigid cavity modes are used to model the acoustic cavity. The dynamic equations of motion for the coupled smart panel-cavity system are derived using Hamilton’s principle. The forcing term due to the cavity acoustic pressure is determined by using virtual work considerations. Five collocated pairs of actuator/sensor pairs are attached to the plate at a predetermined placement scheme. A (multi-input–multi-output) MIMO controller is designed for the coupled vibroacoustic system. The output feedback controller is then employed to emulate the optimal controller by solving the Riccati equations. The performance of the control system in reducing the...
The Journal of the Acoustical Society of America, 1994
Control of noise radiated into an enclosure from an external source is of interest in several app... more Control of noise radiated into an enclosure from an external source is of interest in several applications. The noise is transmitted into the enclosure by the induced structural vibrations of the walls of the enclosure. An active control experiment using discrete piezoelectric sensors and actuators is proposed to sense and control the structure-borne sound. A sound level meter and error microphone are used to measure the acoustic field intensity inside the enclosure with and without control. The results of this experiment will define the feasibility of applying active control methods to larger enclosures such as office partitions, passenger compartments of vehicles, control rooms in factory floors, hospital rooms, and apartments in crowded urban areas.
The Journal of the Acoustical Society of America, 1991
Using piezoelectric sensors and actuators, the vibrating motions of a thin plate could be effecti... more Using piezoelectric sensors and actuators, the vibrating motions of a thin plate could be effectively controlled. Several pieces of Unimorph PZT (lead-titanate-zirconate) were optimally attached on the both sides of a clamped square plate. A series of active vibration control experiments has been tried with different types of control algorithms. Even though the system structure is stiff enough because of the clamped edges, effective vibration control could be implemented with the large electromechanical coupling constant of PZT and well-selected positions of sensors and actuators. Here, particular attention has been paid to several lower-frequency modes. To take advantage of the features of a digital system such as flexibility of the control program and increased logic capability, a microcomputer and a data acquisition board were used to obtain a digital controller.
The Journal of the Acoustical Society of America, 1990
High-frequency air-coupled ultrasonic transducers are used in industrial applications for detecti... more High-frequency air-coupled ultrasonic transducers are used in industrial applications for detecting or ranging with high resolution. The improvement of the coupling between PZT and air is of importance for the transducer performance. Unfortunately, it is difficult to find a material with proper acoustical impedance and small attenuation at high frequency for matching layers. Theoretical analysis and experimental investigation showed that a layer made of a material with an impedance close to that of water is able to improve this matching significantly. Three air-coupled transducers at frequency ranges of 0.5 to 2.0 MHz were fabricated. Reasonable sensitivities and bandwidth were obtained. The variation of performances of the transducers with the thickness of the layer were investigated theoretically and experimentally.
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Papers by Vijay Varadan