Optimal Control of Nonlinear Structures

1988 ◽  
Vol 55 (4) ◽  
pp. 931-938 ◽  
Author(s):  
J. N. Yang ◽  
F. X. Long ◽  
D. Wong
Keyword(s):  
Optimal Control ◽  
Control Systems ◽  
Active Control ◽  
Control Algorithm ◽  
Open Loop ◽  
Control Algorithms ◽  
Nonlinear Structures ◽  
Open Loop Control ◽  
Loop Control ◽  
Optimal Control Algorithms

Three optimal control algorithms are proposed for reducing oscillations of flexible nonlinear structures subjected to general stochastic dynamic loads, such as earthquakes, waves, winds, etc. The optimal control forces are determined analytically by minimizing a time-dependent quadratic performance index, and nonlinear equations of motion are solved using the Wilson-θ numerical procedures. The optimal control algorithms developed for applications to nonlinear structures are referred to as the instantaneous optimal control algorithms, including the instantaneous optimal open-loop control algorithm, instantaneous optimal closed-loop control algorithm, and instantaneous optimal closed-open-loop control algorithm. These optimal algorithms are computationally efficient and suitable for on-line implementation of active control systems to realistic nonlinear structures. Numerical examples are worked out to demonstrate the applications of these optimal control algorithms to nonlinear structures. In particular, control of structures undergoing inelastic deformations under strong earthquake excitations are illustrated. The advantage of using combined passive/active control systems is also demonstrated.

Frequency Shaped Semi-Active Control for Magnetorheological Fluid-Based Vibration Control Systems

2013 ◽  
Author(s):  
Young-Tai Choi ◽  
Norman M. Wereley ◽  
Gregory J. Hiemenz
Keyword(s):  
Vibration Control ◽  
Control Systems ◽  
Active Control ◽  
Control Algorithm ◽  
Active Vibration Control ◽  
Control Algorithms ◽  
Model Parameters ◽  
Mr Fluid ◽  
Control Current ◽  
Active Vibration

Novel semi-active vibration controllers are developed in this study for magnetorheological (MR) fluid-based vibration control systems, including: (1) a band-pass frequency shaped semi-active control algorithm, (2) a narrow-band frequency shaped semi-active control algorithm. These semi-active vibration control algorithms designed without resorting to the implementation of an active vibration control algorithms upon which is superposed the energy dissipation constraint. These new Frequency Shaped Semi-active Control (FSSC) algorithms require neither an accurate damper (or actuator) model, nor system identification of damper model parameters for determining control current input. In the design procedure for the FSSC algorithms, the semi-active MR damper is not treated as an active force producing actuator, but rather is treated in the design process as a semi-active dissipative device. The control signal from the FSSC algorithms is a control current, and not a control force as is typically done for active controllers. In this study, two FSSC algorithms are formulated and performance of each is assessed via simulation. Performance of the FSSC vibration controllers is evaluated using a single-degree-of-freedom (DOF) MR fluid-based engine mount system. To better understand the control characteristics and advantages of the two FSSC algorithms, the vibration mitigation performance of a semi-active skyhook control algorithm, which is the classical semi-active controller used in base excitation problems, is compared to the two FSSC algorithms.

An Analytical Tension Model for Continuum Robots with n Generally Positioned Tendons

2019 ◽  
Vol 04 (03n04) ◽  
pp. 1942003
Author(s):  
Mohsen Moradi Dalvand ◽  
Saeid Nahavandi ◽  
Robert D. Howe
Keyword(s):  
Stereo Vision ◽  
Control Algorithm ◽  
Open Loop ◽  
Open Loop Control ◽  
Continuum Robots ◽  
Loop Control ◽  
Proposed Model ◽  
Continuum Robot ◽  
Tension Loading ◽  
Tendon Compliance

The estimation of tension loads in multi-tendon continuum robots or catheters plays an important role not only in the design process but also in the control algorithm to avoid slack. An analytical tension loading model is developed that, for any given beam configuration within the workspace, calculates tendon tensions in [Formula: see text]-tendon continuum robots with general tendon positioning. The model accounts for the bending and axial compliance of the manipulator as well as tendon compliance. A 6-tendon continuum robot integrated with a stereo vision-based 3D reconstruction system is utilized to experimentally validate the proposed analytical model in open-loop control architecture. The proposed model demonstrates around 95% accuracy in estimating tendon tensions in a continuum robot with general tendon positioning and axial stretch in its tendons for all of the trials and experiments.

Yield Improvement via minimization of step height non-uniformity in Chemical Mechanical Planarization (CMP)

2005 ◽  
Vol 867 ◽  
Author(s):  
Muthukkumar Kadavasal ◽  
Sutee Eamkajornsiri ◽  
Abhijit Chandra ◽  
Ashraf F. Bastawros
Keyword(s):  
Chemical Mechanical Planarization ◽  
Open Loop ◽  
Step Height ◽  
Control Algorithms ◽  
Open Loop Control ◽  
Time Step ◽  
Surface Evolution ◽  
Loop Control ◽  
Final Surface ◽  
Pattern Density

AbstractObtaining local and global planarity is one of the prime criteria in dielectric and metal planarizations. Although Chemical Mechanical Planarization (CMP) helps us achieve this criterion in constant pattern density surfaces, the same is not true for variable pattern density surfaces this results in formation of global step heights across the die. This paper provides a pressure open loop control algorithms for obtaining planarity across a die containing variations in pattern densities. Based on the variation of pattern density and surface heights across the die, the surfaces are separated into zones and the pressure is varied spatially and/or temporally to obtain uniform surface heights, with enhanced step height uniformity. One of the algorithms looks ahead and recalculates/modifies the pressure values by identifying the step heights that could be formed after a specified time step. The final surface predictions have improved uniformity on the upper surface as well as on the step heights across the entire die. The simulation would help us track the polishing process for each time step and guide us with the optimized pressure values that can be applied in order to an uniform final surface evolution.

Suppression of Instabilities in Gaseous Fuel High-Pressure Combustor Using Non-Coherent Oscillatory Fuel Injection

2003 ◽  
Author(s):  
D. Shcherbik ◽  
E. Lubarsky ◽  
Y. Neumeier ◽  
B. T. Zinn ◽  
K. McManus ◽  
...  
Keyword(s):  
High Pressure ◽  
Active Control ◽  
Fuel Injection ◽  
Injection Rate ◽  
Open Loop ◽  
Combustion Instabilities ◽  
Open Loop Control ◽  
Pressure Oscillations ◽  
Loop Control ◽  
Fuel Injection Rate

This paper describes the application of active, open loop, control in effective damping of severe combustion instabilities in a high pressure (i.e., around 520 psi) gas turbine combustor simulator. Active control was applied by harmonic modulation of the fuel injection rate into the combustor. The open-loop active control system consisted of a pressure sensor and a fast response actuating valve. To determine the dependence of the performance of the active control system upon the frequency, the fuel injection modulation frequency was varied between 300 and 420 Hz while the frequency of instability was around 375 Hz. These tests showed that the amplitude of the combustor pressure oscillations strongly depended upon the frequency of the open loop control. In fact, the amplitude of the combustor pressure oscillations varied ten fold over the range of investigated frequencies, indicating that applying the investigated open loop control approach at the appropriate frequency could effectively damp detrimental combustion instabilities. This was confirmed in subsequent tests in which initiation of open loop modulation of the fuel injection rate at a non resonant frequency of 300Hz during unstable operation with peak to peak instability amplitude of 114 psi and a frequency of 375Hz suppressed the instability to a level of 12 psi within approximately 0.2 sec (i.e., 75 periods). Analysis of the time dependence of the spectra of the pressure oscillations during suppression of the instability strongly suggested that the open loop fuel injection rate modulation effectively damped the instability by “breaking up” (or preventing the establishment of) the feedback loop between the reaction rate and combustor oscillations that drove the instability.

scholarly journals Interleaved DC-DC Converter with Discrete Duty Cycle and Open Loop Control

2016 ◽  
Vol 53 (4) ◽  
pp. 14-21
Author(s):  
K. Kroics ◽  
A. Sokolovs
Keyword(s):  
Duty Cycle ◽  
Control Algorithm ◽  
Open Loop ◽  
Current Loop ◽  
Open Loop Control ◽  
Output Current ◽  
Loop Control ◽  
Control Principle ◽  
Conduction Mode ◽  
Current Ripple

Abstract The authors present the control principle of the multiphase interleaved DC-DC converter that can be used to vastly reduce output current ripple of the converter. The control algorithm can be easily implemented by using microcontroller without current loop in each phase. The converter works in discontinuous conduction mode (DCM) but close to boundary conduction mode (BCM). The DC-DC converter with such a control algorithm is useful in applications that do not require precise current adjustment. The prototype of the converter has been built. The experimental results of the current ripple are presented in the paper.

Motion Control Analysis of the Fruit-Trees Robot

2011 ◽  
Vol 135-136 ◽  
pp. 1179-1182
Author(s):  
Jia Ao Yu ◽  
Min Cang Fu
Keyword(s):  
Pid Control ◽  
Control Algorithm ◽  
Response Speed ◽  
Fruit Trees ◽  
Open Loop ◽  
Control Analysis ◽  
Open Loop Control ◽  
Loop Control ◽  
Straight Line ◽  
Motor Control System

The article tracks the fruit-trees robot, and analyzes the fruit-trees robot’s dual-motor control system. Based on the speed incremental PID closed-loop control algorithm of the step DC motor, the PID controller’s proportional coefficient, integral coefficient and differential coefficient is concluded. It demonstrates from the stimulations and experiments that the usage of speed incremental PID control do better at the response speed and stability than the open-loop control motor when the robot is run by a straight line on the ground at the 3000rpm.

scholarly journals Modal Engineering for MEMS Devices: Application to Galvos and Scanners

2020 ◽  
Author(s):  
Lawrence Barrett ◽  
Matthias Imboden ◽  
Josh Javor ◽  
David K. Campbell ◽  
David J. Bishop
Keyword(s):  
High Speed ◽  
Open Loop ◽  
Optical Systems ◽  
Control Algorithms ◽  
Mems Devices ◽  
Open Loop Control ◽  
Optical Elements ◽  
Loop Control ◽  
High Q ◽  
Change Position

Optical systems typically use galvanometers (aka galvos) and scanners. Galvos move optical elements such as mirrors, quasi-statically, from one static position to another, and an important figure of merit is their step-settle relaxation time. Scanners move in an oscillatory fashion, typically at the device resonant frequency. MEMS devices, which have many advantages and are often used in such optical systems, are typically high Q devices. Moving from one position to another for a galvo or one frequency/amplitude to another for scanners, can take many periods to settle following the ring down. During these transitions, the optical system is inactive and the time is not being efficiently used. In this article we show how a novel class of open loop control algorithms can be used to rapidly change position, frequency and amplitude, typically in well under the period of the device. We show how the MEMS designer can excite, with complete, high-speed control, a vibrational mode of the system. We call this modal engineering, the ability to control the modes of the system in a practical, fast way. This control of the modes is accomplished with open loop control algorithms.

Control Algorithms for Semi-Active Structural Systems: Do they Really Matter?

2008 ◽  
Vol 56 ◽  
pp. 182-187
Author(s):  
Antonio Occhiuzzi
Keyword(s):  
Control System ◽  
Control Systems ◽  
Active Control ◽  
Structural Control ◽  
Control Algorithm ◽  
Scientific Literature ◽  
Control Algorithms ◽  
Control Law ◽  
Structural Systems ◽  
Active Structural Control

Control algorithms for semi-active structural control system found in the scientific literature often rely on the choice of several parameters included in the control law. The present paper shows the preliminary conclusions of a study aiming to explain the weak dependency of the response reduction associated to semi-active control systems on the particular choice of the control algorithm adopted, provided that the relevant parameters of any control law be properly tuned.

Randomized Algorithms for Open-Loop Control of Clutch-to-Clutch Transmissions

1999 ◽  
Vol 121 (3) ◽  
pp. 508-517 ◽  
Author(s):  
Albert Yoon ◽  
Pramod Khargonekar ◽  
Kumar Hebbale
Keyword(s):  
Optimal Control ◽  
Randomized Algorithms ◽  
Automatic Transmission ◽  
Computational Cost ◽  
Control Design ◽  
Open Loop ◽  
Transmission Model ◽  
Open Loop Control ◽  
Loop Control ◽  
Randomized Search

In this paper, randomized algorithms are used to design an open-loop control for a clutch-to-clutch shift automatic transmission and to study the robustness of that control. The open-loop control design problem can be posed as an optimal control problem but because of the computational cost associated with each simulation and the complexity of the transmission model, classical results from optimal control theory are not a practically feasible approach for this problem. We apply randomized search algorithms for optimization to these problems and present some promising results.

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