Active control of flexural vibrations

This paper presents a computationally fast and efficient least-squares method to minimize the vibration of any general rotor-bearing system by the application of external control forces. The D-optimality concept is used to optimize the force locations. The proposed method provides a wide range of statistical information, and the sensitivity of the optimum response to changes in the control forces. Magnetic bearings can be applied to implement the open-loop adaptive vibration control strategies outlined in the paper. These components can also be used to inject a multi-frequency test signal as required for identi­fication studies.

Vibration control of multi-mode rotor-bearing systems

Applying distributed parameter concepts of propagation and reflection to dynamics and controls analysis of bending vibrations in flexible aerospace vehicles

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Application of Distributed Parameter Concepts to Dynamic Analysis and Control of Bending Vibrations

Modal response of a beam with a sensor–actuator pair for the implementation of velocity feedback control

Experiments on the active control of flexural wave power flow

The use of active feedback elements to produce damping of multiresonant structures is examined analytically, and the analysis is compared with experimental results obtained for a 48 in.‐long uniform beam damped at its midpoint. The analysis method involves an adaption of the conventional Nichols‐chart technique and appears to be quite reliable. By using commercially available components, a simultaneous reduction in resonant mobilities of resonances below 10 kc/sec is predicted and demonstrated. Reductions were proportional to the mobility values prior to active‐damping applications and also to the gain in the feedback path. The limitations on the amount of damping possible are imposed by stability conditions for the feedback loop, which in turn depend primarily upon the transfer function of the forcing and pickup components of this loop. The stability analysis for particular components used in the beam experiment is presented.

Theoretical and Experimental Results on Active Vibration Dampers

A method of modifying a percussion tool to provide noise reduction, and a percussion tool having effective noise damping characteristics. In the method of the present invention, a troublesome noise frequency radiated by the tool is identified, and a resonant bending mode shape for the tool is determined, which bending mode shape corresponds to the identified noise frequency. The tool is then assembled and a structural discontinuity is introduced at a point along the length of the tool which is a predetermined axial distance from a selected antinode of the bending mode shape to provide an impedance mismatch at that point. The tool, which is of predetermined length, is formed of one or more sections, each of which is of a selected length. The lengths of the sections are carefully determined such that when the tool is in assembled condition, impedance mismatches are provided at selected points along the length of the tool, to provide noise reduction of several troublesome noise frequencies.

Thomas H. Rockwell

Papers

Theoretical and Experimental Results on Active Vibration Dampers

Percussion tool with noise reducing characteristics and method of making