Anti-sway method for reducing vibrations on a tower crane structure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Roberto P. L. Caporali
Keyword(s):  
Normal Vibration ◽  
Open Loop ◽  
Smoothing Method ◽  
Elastic Structure ◽  
Underactuated System ◽  
Vibration Modes ◽  
Open Loop System ◽  
Tower Crane ◽  
Iterative Calculation ◽  
Deformable System

Abstract We develop a solution to the problem of the behavior of a tower crane considered as a deformable system, and therefore subject to vibrations, whereas the controlled movement of a payload is implemented. The motion of the payload is calculated taking into account the normal vibration modes of the tower crane and the swaying of the payload. A “command smoothing” method relative to an open-loop system is used for reducing the sway of the payload, through smoothing the original command by the crane operator. This leads, as a consequence, to a reduction in the vibrations of the crane structure. An iterative calculation of the sway angle and the corresponding applied velocity profiles as input to the crane motors is applied. The tower crane is considered as a high nonlinear underactuated system; it is modeled considering the possible deformation of the structure. The results relating to the normal deformations of the crane are obtained, highlighting how these vibrations are strongly attenuated when an anti-sway system for the payload is implemented. Therefore, it is shown how this control leads to the best results in terms of performance for both the payload movement (shortest possible profile for the rotation movement and damping of the load oscillation) and the structure of the tower crane. Applying the method described in this paper, the structure of the tower crane does not undergo the strong horizontal and vertical oscillations that occur when the elastic structure is not considered in the crane model.

scholarly journals A Novel Control Strategy for Grid-Connected Inverter Based on Iterative Calculation of Structural Parameters

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3306 ◽  
Author(s):  
Zhenao Sun ◽  
Dazhi Wang ◽  
Tianqing Yuan ◽  
Zairan Liu ◽  
Jiahui Yu
Keyword(s):  
Control Strategy ◽  
Structural Parameters ◽  
Dynamic Performance ◽  
Open Loop ◽  
Output Current ◽  
Open Loop System ◽  
Iterative Calculation ◽  
Static Performance ◽  
Grid Connected Inverter ◽  
Pv Grid

A novel control strategy that is based on iterative calculation of structural parameters is proposed for grid-connected inverter in this paper. The proposed strategy has a good dynamic performance, which makes it particularly suitable for the application of PV grid-connected generation. First, a second-order discretization mathematical model of grid-connected inverter control is established in the dq frame. The corresponding relation between the control signal and the output current is deduced in formulas. Then, the values of structural parameters in the formulas can be obtained through iterative calculation, which can further reduce the amount of calculation. After several iteration cycles, the structural parameters are approximately equal to their actual values and the inverter can be controlled as an open-loop system with its dynamic performance optimized. At last, simulation and experiments are performed. The results show that the static performance of the proposed strategy is as good as that of the classical ones, but its dynamic performance is improved significantly.

Multi-Stage System Identification of a Gas Turbine

2017 ◽  
Author(s):  
Amit Pandey ◽  
Maurício de Oliveira ◽  
Chad M. Holcomb
Keyword(s):  
Gas Turbine ◽  
Closed Loop ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop Control ◽  
Input Output ◽  
Open Loop System ◽  
Loop Control ◽  
Multi Stage ◽  
Identification Techniques

Several techniques have recently been proposed to identify open-loop system models from input-output data obtained while the plant is operating under closed-loop control. So called multi-stage identification techniques are particularly useful in industrial applications where obtaining input-output information in the absence of closed-loop control is often difficult. These open-loop system models can then be employed in the design of more sophisticated closed-loop controllers. This paper introduces a methodology to identify linear open-loop models of gas turbine engines using a multi-stage identification procedure. The procedure utilizes closed-loop data to identify a closed-loop sensitivity function in the first stage and extracts the open-loop plant model in the second stage. The closed-loop data can be obtained by any sufficiently informative experiment from a plant in operation or simulation. We present simulation results here. This is the logical process to follow since using experimentation is often prohibitively expensive and unpractical. Both identification stages use standard open-loop identification techniques. We then propose a series of techniques to validate the accuracy of the identified models against first principles simulations in both the time and frequency domains. Finally, the potential to use these models for control design is discussed.

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.

Modeling of Multibody Flexible Articulated Structures With Mutually Coupled Motions: Part II — Application and Results

1992 ◽  
Author(s):  
Jiechi Xu ◽  
Joseph R. Baumgarten
Keyword(s):  
Experimental Data ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Open Loop ◽  
Body Motion ◽  
Universal Joint ◽  
Open Loop System ◽  
Numerical Examples ◽  
Kinematic Properties ◽  
Good Agreement

Abstract The application of the systematic procedures in the derivation of the equations of motion proposed in Part I of this work is demonstrated and implemented in detail. The equations of motion for each subsystem are derived individually and are assembled under the concept of compatibility between the local kinematic properties of the elastic degrees of freedom of those connected elastic members. The specific structure under consideration is characterized as an open loop system with spherical unconstrained chains being capable of rotating about a Hooke’s or universal joint. The rigid body motion, due to two unknown rotations, and the elastic degrees of freedom are mutually coupled and influence each other. The traditional motion superposition approach is no longer applicable herein. Numerical examples for several cases are presented. These simulations are compared with the experimental data and good agreement is indicated.

A Parametrically Amplified MEMS Gyroscope

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001322-001334
Author(s):  
Barry J. Gallacher ◽  
Z. X. Hu ◽  
J. S. Burdess ◽  
K. M. Harish
Keyword(s):  
Open Loop ◽  
Parametric Amplification ◽  
Vibration Modes ◽  
Q Factor ◽  
Amplitude Control ◽  
Mems Gyroscope ◽  
Primary Mode ◽  
Harmonic Forcing ◽  
Control Schemes ◽  
Order Of Magnitude

The applicability of parametric amplification of either the primary and secondary vibration modes of a MEMS gyroscope, shown in Fig.1 is investigated experimentally in this paper. All control schemes have been implemented digitally onto a SHARC DSP development board. Parametric gains in excess of 80, which correspond to multiplication of the Q-factor by a factor of 80, are demonstrated experimentally for open-loop operation of the primary mode and are shown in Fig. 2. For open-loop operation it is shown that amplitude limiting nonlinearities become important as the vibration amplitude increases (see Figs.3) and that parametric amplification in excess of 80 can be only be achieved by further reducing the harmonic forcing amplitude. In many applications it is desirable to have as high a Q-factor as possible. The rate gyroscope is one application were active control of the Q-factor is extremely pertinent. If applied to the primary mode then it permits reduced forcing levels and hence contamination from “feedthrough”. If applied to the sense mode then the Coriolis force is effectively amplified. Parametric amplification of the secondary mode of the gyroscope is a challenging problem but it has the potential to improve the performance of MEMS rate gyroscope but an order of magnitude. In operation as a rate gyroscope it is important to maintain the amplitude of the primary mode of vibration at a constant level. For the case of a parametrically amplified primary mode the amplitude control circuit automatically adjusts the parametric excitation parameters to ensure the required parametric gain is achieved whilst at the same time reducing the amplitude of the harmonic forcing. In closed loop parametric amplification of the primary mode by a factor 20 have been demonstrated. Experimental results obtained from the amplified primary mode are shown in Fig.4.

Correlation of Microwave Dielectric Properties and Normal Vibration Modes of Ba(Mg1/3Ta2/3)O3-Series Materials

2004 ◽  
Vol 13 (1-3) ◽  
pp. 271-275 ◽  
Author(s):  
Yi-Chun Chen ◽  
Hsiu-Fung Cheng ◽  
Chia-Chi Lee ◽  
Chih-Ta Chia ◽  
Hsiang-Lin Liu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Normal Vibration ◽  
Microwave Dielectric Properties ◽  
Vibration Modes ◽  
Microwave Dielectric

Fretting Behavior of Coated and Treated Titanium Alloy Using an Open-Loop System

2005 ◽  
Author(s):  
G. R. Yantio Njankeu ◽  
J.-Y. Paris ◽  
J. Denape ◽  
L. Pichon ◽  
J.-P. Rivie`re
Keyword(s):  
Titanium Alloy ◽  
Relative Motion ◽  
High Frequency ◽  
Open Loop ◽  
Loop System ◽  
Test Apparatus ◽  
Open Loop System ◽  
Wear Rates ◽  
Low Wear

Titanium alloys are well known to present poor sliding behaviour and high wear values. Various coatings and treatments have been tested to prevent such an occurrence under fretting conditions at high frequency of displacement (100 Hz). An original test apparatus, using an open-loop system instead of a classical imposed displacement simulator, has been performed to directly display the phenomenon of seizure, defined as the stopping of the relative motion between the contacting elements. A classification of the tested coatings has been proposed on the basis of their capacity to maintain full or partial sliding conditions, to present low wear rates and to prevent seizure.

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