Dissipative Energy Flow in Systems at Parametric Anti-Resonance

2012 ◽  
Author(s):  
F. Dohnal
Keyword(s):  
Energy Flow ◽  
Open Loop ◽  
Vibration Modes ◽  
Approximate Analytical Expression ◽  
Loop Control ◽  
System Parameters ◽  
Damped System ◽  
Constant Coefficients ◽  
Time Periodicity ◽  
Time Periodic

Recent investigations have shown theoretically and experimentally that the transient vibrations of a lightly damped system can be suppressed or even stabilized by a time-periodic open-loop control of one of its system parameters. Introducing time-periodicity in system parameters may lead, in general, to a dangerous and well-known parametric resonance. In contrast to such a resonance, a properly tuned time-periodicity is capable to extract vibration energy from the system and to increase the effective damping of transient vibrations. At this specific operation the system is tuned at parametric anti-resonance. The beneficial interaction of damping and time-periodicity was first formulated by A. Tondl in 1998. His pioneering work deals with stabilizing self-excited vibrations. It was proven by F. Dohnal in 2005 that the vibrations of a general lightly damped system (not necessarily unstable) can be reduced by parametric anti-resonance, too. A physical interpretation of the parametric anti-resonance is related to the coupling of vibration modes of the underlying system with constant coefficients. This interpretation leads intuitively to the calculation of the energy flow of each vibration mode and leads to clear physical insight of how parametric anti-resonances work. This interpretation of mode coupling is developed further resulting in an approximate analytical expression for the effective damping of a system driven at parametric anti-resonance. This expression allows the statement of the maximum effective damping achievable by this method. The discussion of the energy flow of a linear, lightly damped system possessing a time-periodic stiffness coefficient its physical and modal displacements highlights the coupling of vibration modes of the underlying system with constant coefficients.

CONTROLLABILITY AND INVARIANCE PROPERTIES OF TIME-PERIODIC SYSTEMS

2005 ◽  
Vol 15 (04) ◽  
pp. 1361-1375 ◽  
Author(s):  
TOBIAS GAYER
Keyword(s):  
Degrees Of Freedom ◽  
Open Loop ◽  
Loop Control ◽  
Invariance Properties ◽  
Control Sets ◽  
Time Periodicity ◽  
Parameter Dependent ◽  
Time Periodic ◽  
Bifurcation Process ◽  
Insight Into

In this paper, control sets, i.e. maximal subsets of approximate controllability, are introduced for time-periodic parameter dependent systems with open loop control. It is shown that the time-periodicity causes some special topological properties of control sets that influence their merging and bifurcation process. These properties allow an enhancement of the available set-oriented numerical methods for the approximation of control sets. For the application of these methods, the so-called inner-pair condition must be satisfied. It is shown that this condition holds for a wide class of time-periodic control-affine systems that includes, for instance, coupled excited oscillators if the number of controls equals the degrees of freedom. The application of the methods to the controlled escape equation with periodic driving term where the parameter acts on the control range gives insight into the changing dynamics and different types of mergers of control sets.

scholarly journals Automatic locking of a parametrically resonating, base-excited, nonlinear beam

2021 ◽  
Author(s):  
Nir Ben Shaya ◽  
Izhak Bucher ◽  
Amit Dolev
Keyword(s):  
Relative Phase ◽  
Closed Loop ◽  
Dynamical Behavior ◽  
Open Loop ◽  
Vibration Modes ◽  
Nonlinear Structure ◽  
Nonlinear Beam ◽  
Loop Control ◽  
Control Scheme ◽  
Slender Beams

AbstractDescribed is a closed-loop control scheme capable of stabilizing a parametrically excited nonlinear structure in several vibration modes. By setting the relative phase between the spatially filtered response and the excitation, the open-loop unstable solution branches are stabilized under a 2:1 parametric excitation of a chosen mode of vibration. For a given phase, the closed-loop automatically locks on a limit cycle, through an Autoresonance scheme, at any desired point on the solution branches. Axially driven slender beams and nanowires develop large transverse vibration under suitable amplitudes and frequency base-excitation that are sensitive to small potential coupled field. To utilize such a structure as a sensor, stable and robust operation are made possible by the control scheme. In addition, an optimal operating point with large sensitivity to the sensed potential field can be set using phase as a tunable parameter. Detailed analysis of the dynamical behavior, experimental verifications, and demonstrations sheds light on some features of the system dynamics.

scholarly journals Robustness of Command Input Preshaping Technique Applied to Residual Vibration Reduction

2004 ◽  
Vol 11 (3-4) ◽  
pp. 377-382 ◽  
Author(s):  
Paolo Pennacchi
Keyword(s):  
Vibration Reduction ◽  
Open Loop ◽  
Open Loop Control ◽  
Residual Vibration ◽  
Loop Control ◽  
System Parameters ◽  
Control Techniques ◽  
Command Input

Open-loop control techniques, such as command input preshaping, are quite sensible to modelling errors and noise. In the paper, an analysis and a discussion about the robustness of the technique with respect to the errors than can affect estimation of the values of the system parameters is presented.

Open-Loop Control of a Flexible Manipulator With Two Links: Experimental Results

2001 ◽  
Author(s):  
G. Mimmi ◽  
L. Frosini ◽  
P. Pennacchi ◽  
C. Rottenbacher
Keyword(s):  
Open Loop ◽  
Experimental Results ◽  
Flexible Manipulator ◽  
Control Technique ◽  
Open Loop Control ◽  
Residual Vibration ◽  
Rectangular Section ◽  
Loop Control ◽  
System Parameters ◽  
Set Up

Abstract This paper describes the experimental results of an open-loop control technique applied to a flexible manipulator, specially designed for space duties, in order to reduce the residual vibrations at the end of the positioning. The experimental set-up is a system with two flexible links with rectangular section connected by rotational joints. First, the experimental identification of the system parameters has been carried out. Then, four different motion inputs have been implemented. The performances of these motion inputs are compared in terms of residual vibration at the end of the positioning. The experimental results confirm the effectiveness of the motion input pre-shaping technique in the reduction of the residual vibrations.

Open-loop control of compensation for optical propagation through a turbulent shear flow

1998 ◽  
Author(s):  
C. Truman ◽  
Lenore McMackin ◽  
Robert Pierson ◽  
Kenneth Bishop ◽  
Ellen Chen
Keyword(s):  
Shear Flow ◽  
Open Loop ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Open Loop Control ◽  
Loop Control ◽  
Optical Propagation

scholarly journals Sensuator: A Hybrid Sensor–Actuator Approach to Soft Robotic Proprioception Using Recurrent Neural Networks

Actuators ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 30
Author(s):  
Pornthep Preechayasomboon ◽  
Eric Rombokas
Keyword(s):  
Neural Networks ◽  
Recurrent Neural Networks ◽  
Linear Models ◽  
Open Loop ◽  
Proof Of Concept ◽  
State Estimator ◽  
Loop Control ◽  
Practical Applications ◽  
Soft Actuator ◽  
The Cost

Soft robotic actuators are now being used in practical applications; however, they are often limited to open-loop control that relies on the inherent compliance of the actuator. Achieving human-like manipulation and grasping with soft robotic actuators requires at least some form of sensing, which often comes at the cost of complex fabrication and purposefully built sensor structures. In this paper, we utilize the actuating fluid itself as a sensing medium to achieve high-fidelity proprioception in a soft actuator. As our sensors are somewhat unstructured, their readings are difficult to interpret using linear models. We therefore present a proof of concept of a method for deriving the pose of the soft actuator using recurrent neural networks. We present the experimental setup and our learned state estimator to show that our method is viable for achieving proprioception and is also robust to common sensor failures.

Precise open-loop control of MEMS deformable mirror shape

2008 ◽  
Author(s):  
Thomas Bifano ◽  
Jason Stewart ◽  
Alioune Diouf
Keyword(s):  
Open Loop ◽  
Deformable Mirror ◽  
Open Loop Control ◽  
Loop Control
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