James W. Kamman

Multibody Dynamics Modeling of Variable Length Cable Systems

This paper presents a procedure for studying the dynamics ofvariable length cable systems. Such systems commonly occur in deploymentand retrieval (pay-out and reel-in) in cable towing systems such as inship and marine applications.The cable is modeled as a chainand treated as a multibody system. The chain links in turn are modeledas lumped masses. The pay-out/reel-in process is modeled with variablelength links near the towing point.Application in marine systems are presented and discussed.

Narrow band active control of sound radiated from a baffled beam using local volume displacement minimization

Abstract Further development of a control technique for reduction of sound radiated from vibrating structures is presented. This control technique is based on minimization of local volume displacement, velocity, or acceleration of a vibrating structure. Multiple, single-input/single-output cancellation devices are used. Each device controller employs a motion sensor and an acoustic actuator (loudspeaker). The motion sensor signal is related to the local volume displacement of the structure which is then reduced by a loudspeaker driven with an equal but opposing volume displacement. Previous work showed the successful implementation of this technique for uniformly vibrating radiators. This paper presents the development of this technique for reduction of sound radiated from a vibrating beam. A PVDF sensor was used for measurement of local volume displacement of the beam. This sensor was used in conjunction with an internal pressure sensor mounted in the loudspeaker enclosure. Sound reductions of up to 20 dB were achieved within a narrow range of vibration frequencies (centered around the first beam mode). Finally, design of a single integrated sensor is suggested for implementation of many PVDF sensors on a beam.

Theoretical development and experimental validation of local volume displacement sensors for a vibrating beam

Further development of local volume displacement sensors is presented. This development supports the implementation of noise control techniques that are based on minimization of local volume displacements, velocities, or accelerations of a vibrating structure. In this paper, we present a general methodology for the development of local volume displacement sensors for vibrating beams using PolyVinyliDene Fluoride (PVDF). This methodology was verified experimentally for a clamped beam. The local volume displacement measured using a single PVDF sensor matched the local volume displacement found using multiple accelerometer measurements. The resulting sensors span the entire length of the beam. They have a quadratic shape over that portion of the beam whose volume displacement is desired, and they have a linear shape over all other sections. Sensor design issues for different beam boundary conditions are discussed along with a presentation of some sample sensor shapes for various beam segments and boundary conditions.

Evaluation of an Actuator Placement Method for Active Noise Control Applications

In our previous work, we developed a new actuator placement algorithm that is capable of selecting the best actuator placement for active noise control problems over a broad band of frequencies. The actuator selection algorithm is based on a novel extension of the Householder QR subset selection algorithm. The QR algorithm uses the l 2 matrix norm as a performance measure. In this paper, numerical results generated by that algorithm are compared with numerical results generated using five different performance measures. These measures, which are based on different matrix norms and functions of the actuator frequency responses, yield actuator placements that result in active noise control systems with improved performance and robustness.

Active Reduction of Radiated Noise From a Baffled Piston Using a Volume Velocity, Feedforward Controller

A new active noise-control technique has been developed for control of low-frequency sound generated by vibrating surfaces which is based on minimizing the volume velocity. Noise reduction is achieved by distributing an array of control devices over the surface of the radiating structure. Each device consists of a motion-sensing mechanism, an analog control circuit, and a loudspeaker. The loudspeaker is driven such that it reduces the volume velocity of the radiating structure within its close proximity. This paper briefly presents the theory behind this approach as well as controller design issues. Finally, a discussion of the experimental verification of this concept using a 10-in, uniformly vibrating circular plate (i.e., a baffled piston) and a single noise-control device is given. Broadband (50-500 Hz) sound reductions in the range of 10-20 dB were achieved over a wide spatial area.