Command shaping applied to nonlinear systems with configuration -dependent resonance

Victor Maxwell Beazel, Purdue University

Abstract

Dynamic systems that are designed for rapid repositioning are typically pushed to the point where they exhibit flexible behavior that hinders the accomplishment of the purpose for which they were designed. Remedial techniques are frequently employed to either enable these systems to achieve the objectives of their original design, or to extend their operating envelope beyond the design limits that were initially envisioned by their designers. Some techniques concentrate on increasing system damping, which may be active or passive in nature. Other techniques, such as command shaping, focus on selecting appropriate input commands to drive a system to its desired final position, without exciting the system's natural frequencies. Command shaping is the focus of this present work. While there has been much accomplished in this area for linear systems with fixed natural frequencies, investigation of appropriate ways to extend these methods to systems with configuration-dependent resonance is still in its infancy. With this objective in mind, a gimbaled telescope turret has been modeled in such a way that it only possesses configuration-invariant natural frequencies. Command shaping has been applied to the system model, demonstrating that, in spite of significant nonlinear behavior, the turret can undergo large angle slew maneuvers and come to a stop with minimal residual vibration. The model has then been modified to include a configuration-dependent resonance. Command shaping methodologies have been extended to accommodate this broader class of dynamic systems, providing significant reduction in endpoint vibration of the system response over that of the unshaped case.

Degree

Ph.D.

Advisors

Meckl, Purdue University.

Subject Area

Mechanical engineering

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