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Wednesday, July 22, 2020 | History

3 edition of Limiting vibration in systems with constant amplitude actuators through command preshaping found in the catalog.

Limiting vibration in systems with constant amplitude actuators through command preshaping

Limiting vibration in systems with constant amplitude actuators through command preshaping

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Published by Charles Stark Draper Laboratory, Inc., National Aeronautics and Space Administration in Cambridge, Mass, [Washington, DC .
Written in English


Edition Notes

Statementby Keith Eric Rogers.
SeriesCSDL-T -- 1214., [NASA contractor report] -- NASA CR-188284., CSDL-T -- 1214., NASA contractor report -- NASA CR-188284.
ContributionsUnited States. National Aeronautics and Space Administration.
The Physical Object
FormatMicroform
Pagination1 v.
ID Numbers
Open LibraryOL14667873M

The displacement of the spring–mass system oscillates with a frequency of , slightly less than natural frequency ω 0 = 1.! The amplitude variation has a slow frequency of and period of 20π.! A half-period of 10π corresponds to a single cycle of increasing and then decreasing amplitude. Chapter III Harmonic Excitation of Single-Degree-of-Freedom devices, Gusting winds, Vortex shedding, moving vehicles, Earthquakes, Rough road surfaces, and so on. The forced vibrations of systems are usually caused by dynamic forces F (t) or has a frequency ω and constant amplitude of Size: 1MB.

The crank with small mass rotates at constant angular velocity, causing the mass m to , the graph is helpful to understand how the vibration amplitude varies with system parameters. (base excitation might work; or you can apply a force using some kind of actuator, or you could deliberately mount an unbalanced rotor on the system). lost (damper).The vibration of a system involves the alternating transfer of energy between its potential and kinetic forms. In a damped system, some energy is dissi-pated at each cycle of vibration and must be replaced from an external source if a steady vibration is to be gh a single physical structure may storeFile Size: KB.

  Robust time-optimal control of uncertain flexible spacecraft. Command Shapers for Systems with Actuator Saturation. Closed-Form Specified-Fuel Commands for Two-Mode Systems. A comparison of constant and variable amplitude command shaping techniques for vibration Cited by: Excessive vibration can cause damage to a control valve, measurement equipment and the piping system. Plants often try to fix problems by measuring vibration, moving equipment, stiffening the valve structure, rewelding broken pipes, changing the piping system and other remedies — only to find problems still exist.


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Limiting vibration in systems with constant amplitude actuators through command preshaping Download PDF EPUB FB2

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, Author: Keith Eric Rogers.

Get this from a library. Limiting vibration in systems with constant amplitude actuators through command preshaping.

[Keith Eric Rogers; United States. National Aeronautics and. The basic concepts of command preshaping were taken and adapted to the framework of systems with constant amplitude (on-off) actuators.

In this context, pulse sequences were developed which help to attenuate vibration in flexible systems with high robustness to errors in frequency : Keith Eric Rogers. The basic concepts of command preshaping were taken and adapted to the framework of systems with constant amplitude (on-off) actuators.

In this context, pulse sequences were developed which help to attenuate vibration in flexible systems with high robustness to errors in frequency identification. Limiting vibration in systems with constant amplitude actuators through command preshaping.

By Keith Eric Rogers. Abstract. by Keith Eric (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, Includes Author: Keith Eric Rogers. Although there are many sources of vibration, simply moving a flexible system will generally cause it to vibrate.

One technique for limiting undesired motion-induced vibration is input shaping. This paper investigates the input-shaper design for slewing spacecraft flexible appendages actuated by stepper motors or other constant-amplitude : Christopher Adams, William Singhose.

Input shaping is examined as a technique to reduce the residual vibration in flexible space structures. As part of a NASA program, a nonlinear threedimensional model of the Shuttle's Remote Manipulator System (SRMS) was used to test the interactions between feedback and feedforward control techniques.

A short move time penalty is incurred (on the order of one period of the first mode of vibration). The preshaping technique is robust under system parameter uncertainty and may be applied to both. Input shaping is a method for reducing residual vibrations in computer controlled machines.

Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with a desired system command to produce a shaped input.

The shaped input then becomes the command to the system. A method is presented for limiting vibration in flexible systems by smoothing the original command. The original command is smoothed to drive the flexible systems without inducing vibration.

The proposed smoother is designed as a function of system natural frequency and damping by: The constraint on vibration amplitude can be expressed as the ratio of residual vibration Figure 2: System with Flexible aud Rigid Body Modes.

amplitude with shaping to that without shaping. This percentage vibration can be determined by using the expression for residual vibration of a second-order harmonic oscillator of frequency (t) radians Cited by: Free vibration Equilibrium pos.

• When a system is initially disturbed by a displacement, velocity or acceleration,the system begins to vibrate with a constant amplitude and frequency depending on its stiffness and mass.

• This frequency is called as natural frequency, and the form of the vibration. The robustness of residual vibration control, such as input shaping, has conventionally been evaluated from the ratio of residual vibration amplitude with input shaping to that without input shaping at the time of the final by: we get the amplitude as k F C V ˆ = 1 () and the phase angle (using trigonometric functions similar as in chap): 1 2 2 tan () η η ϕ − = = D A B () We can see that as η approaches 1 the amplitude grows rapidly, and its value near or at the resonance is File Size: KB.

Free vibration [8] of a system is vibration that occurs in the absence of external force. The sources of free vibration are initial displacement of system from equilibrium or give the initial velocity to the system.

Fig. 6 Free vibration: string vibration [9]. Forced vibration [8] is caused by an external force that acts on the system. Magee, D. and Book, W.

J., “Experimental Verification of Modified Command Shaping Using a Flexible Manipulator,” Proc. of the 1st International Conference on Motion and Vibration Cited by: Application of H∞ control for multimodal vibration suppression of a slewing spacecraft using piezoelectric actuators is presented in this paper.

For treating vibration suppression independent of attitude control law while taking into account relative modal responses; a method for modeling effect of attitude maneuver excitations as modal disturbances is by: 2.

Mechanical Vibrations - Chapter 3 Vibration Isolation Dynamical response can be minimized through the use of a proper isolation design.

An isolation system attempts either to protect delicate equipment from vibration transmitted to it from its supporting structure or to prevent vibratory forces generated by machines fromFile Size: KB.

Machinery Vibration Limits and Dynamic Structural Response Vibration monitoring of rotating machinery has developed over the years to the point where it is an accepted maintenance tool. Much effort has been applied towards developing guidelines regarding acceptable absolute levels of vibration.

Discussions of some of these standards andFile Size: 1MB. Input shaping reduces residual vibration in computer controlled machines by convolving a sequence of impulses with a desired system command.

The resulting shaped input is then used to drive the system. The impulse sequence has traditionally contained only positively valued by:. Command shaping is an important open-loop control method for improving the settling time and positioning accuracy.

This technique also minimizes residual vibrations. Shaped command profiles are formed by convolving a sequence of impulses or solving special functions for the desired command signal. To determine the input shaper controller commands, estimated values of the system natural Cited by: 4.What kind of actuators and drivers do I need to use to control the frequency and amplitude (varying frequency with the constant amplitude or varying the amplitude with the constant frequency).

2) How can I control the actuator? I looked into some datasheets about LRA and tactors, but I couldn't find how to control their vibrations.The residual vibration when a robot manipulator is operated at high speed needs to be suppressed.

These vibrations are generated by the resonance of a flexible object being moved by the robot, and research on control algorithms and motion profiles is ongoing to reduce them.

In this paper, we propose a method to reduce the residual vibration of an object moved by a robot manipulator by Cited by: 6.