scholarly journals Adversarially Robust Bayesian Optimization for Efficient Auto-Tuning of Generic Control Structures under Uncertainty

2021 ◽  
Author(s):  
Joel Paulson ◽  
Georgios Makrygiorgos ◽  
Ali Mesbah
Keyword(s):  
Process Model ◽  
Closed Loop ◽  
Bayesian Optimization ◽  
Small Scale ◽  
Loop Control ◽  
Control Structures ◽  
Tuning Parameters ◽  
Highly Nonlinear ◽  
Auto Tuning ◽  
Time Invariant

The performance of advanced controllers depends on the selection of several tuning parameters that can affect the closed-loop control performance and constraint satisfaction in highly nonlinear and nonconvex ways. There has been a significant interest in auto-tuning of complex control structures using Bayesian optimization (BO). However, an open challenge is how to deal with uncertainties in the closed-loop system that cannot be attributed to a lumped, small-scale noise term. This paper develops an adversarially robust BO (ARBO) method that is suited to auto-tuning problems with significant time-invariant uncertainties in a plant simulator. ARBO uses a Gaussian process model that jointly describes the effect of the tuning parameters and uncertainties on the closed-loop performance. ARBO uses an alternating confidence-bound procedure to simultaneously select the next candidate tuning and uncertainty realizations, implying only one expensive closed-loop simulation is needed at each iteration. The advantages of ARBO are demonstrated on two case studies.

Modeling and Control of the In-Situ Thermoplastic Composite Tape-Laying Process

1998 ◽  
Vol 120 (4) ◽  
pp. 507-515 ◽  
Author(s):  
Wei-Ching Sun ◽  
Susan C. Mantell ◽  
Kim A. Stelson
Keyword(s):  
Process Model ◽  
Closed Loop ◽  
Thermoplastic Composite ◽  
Closed Loop Control ◽  
Loop Control ◽  
Modeling And Control ◽  
Composite Tape ◽  
Temperature Feedback ◽  
And Control

In thermoplastic tape-laying with in-situ consolidation, a laminated composite is constructed by the local application of heat and pressure. A moving head, applying heat and pressure, lays down and bonds a new layer to the previously bonded layers (substrate). The temperature at the interface between the top ply and the substrate is critical to achieving interlaminar bonding. Recent research on the in-situ thermoplastic composite tape-laying process has focused on modeling, numerical analysis and experimental analysis, but little research has considered the control of this process. In this work, a method is proposed for modeling and control of in-situ thermoplastic composite tape-laying. The key to the control algorithm is predicting the temperature at the interface between the top ply and the substrate. Based on a process model, a state feedback controller and a state estimator for temperature are designed for closed-loop control using the linear quadratic method. Two different approaches are used to develop the process model for real-time closed-loop control through temperature feedback. In the first approach, a low-order lumped parameter model is constructed from a finite difference scheme. The second approach constructs an empirical model through system identification. The structures of the two models are identical, but the parameters differ. The experimental results have shown that the developed estimator and controller can accurately estimate and control the bonding temperature using temperature feedback indicating that the proposed modeling and control methodology can produce a high quality thermoplastic composite laminate.

scholarly journals Restructuring Controllers to Accommodate Plant Nonlinearities

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
William G. La Cava ◽  
Kushal Sahare ◽  
Kourosh Danai
Keyword(s):  
Closed Loop ◽  
Salient Feature ◽  
Closed Loop Control ◽  
Loop Control ◽  
Control Structures ◽  
Nonlinear Controllers ◽  
Gradient Based ◽  
Linearized Model ◽  
Nonlinear Plants ◽  
Nonlinear Plant

A method of controller restructuring is introduced for improved closed-loop control of nonlinear plants. In this method, an initial controller, potentially the linear controller designed according to the linearized model of the plant, is expanded into several candidate nonlinear control structures that are subsequently shaped to achieve a desired closed-loop response. The salient feature of the proposed method is a metric for quantifying structural perturbations to the controllers, which it uses to scale the structural Jacobian for improving its condition number. This improved Jacobian underlies shaping of candidate controllers through gradient-based search. Results obtained from three case studies indicate the success of the proposed restructuring method in finding nonlinear controllers that improve not only the closed-loop response of the nonlinear plant but also its robustness to modeling uncertainty.

scholarly journals Stator windings condition diagnosis of voltage inverter-fed induction motor in open and closed-loop control structures

2015 ◽  
Vol 64 (1) ◽  
pp. 67-79 ◽  
Author(s):  
Marcin Wolkiewicz ◽  
Grzegorz Tarchała ◽  
Czesław T. Kowalski
Keyword(s):  
Induction Motor ◽  
Closed Loop ◽  
Early Stage ◽  
Motor Drive ◽  
Stator Winding ◽  
Induction Motor Drive ◽  
Loop Control ◽  
Control Structures ◽  
Stator Windings ◽  
Condition Diagnosis

AbstractThis paper deals with detection of the stator windings shorted turns in an induction motor drive working under open (scalar) and closed loop (Direct Field Oriented DFO) control structures. In order to detect the early stage of stator winding fault, the analysis of symmetrical and principal components of stator voltages and currents is used. Experimental results obtained from a specially prepared induction motor are presented.

scholarly journals An Optimal Preview Control for Linear Systems

1980 ◽  
Vol 102 (3) ◽  
pp. 188-190 ◽  
Author(s):  
C. C. MacAdam
Keyword(s):  
Linear Systems ◽  
Closed Loop ◽  
Linear Time ◽  
Closed Loop Control ◽  
Preview Control ◽  
Controlled System ◽  
Loop Control ◽  
Linear Time Invariant ◽  
Linear Time Invariant Systems ◽  
Time Invariant

A technique for synthesizing closed-loop control of linear time-invariant systems during tracking of previewed inputs is presented. The derived control is directly dependent upon the properties of the controlled system and is obtained by minimization of a defined previewed output error.

Multivariable Adaptive Control of Thermal Properties During Welding

1991 ◽  
Vol 113 (1) ◽  
pp. 82-92 ◽  
Author(s):  
C. C. Doumanidis ◽  
David E. Hardt
Keyword(s):  
Adaptive Control ◽  
Thermal Properties ◽  
Process Model ◽  
Closed Loop ◽  
Control Method ◽  
Complete Solution ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Loop Control ◽  
Control Work

Complete solution of the welding control problem involves regulating weld geometry, residual stresses, distortion and weldment metallurgical characteristics. The latter has been largely ignored in closed-loop control work, yet it is a basic determinant of weld integrity. In this paper, a previously developed input-output model for continuous regulation of the critical thermal properties of heat affected zone and cooling rate is used to develop a closed-loop MIMO control scheme. Since the physical system is non-linear and non-stationary, and process disturbances are reflected as model parameter changes, an adaptive control method is used. The implementation of the controller is based on deadbeat adaptive control, and it is applied to several different forms of the basic welding process model. The different models reflect a need to simplify the control system to accommodate available process measurements and hardware capabilities. A series of experiments performed on a robotic Gas Metal Arc welding system are presented that confirm the basic stability, robustness, adaptivity, tracking and disturbance rejection properties of the scheme. Bandwidth limitations are identified and improvements (primarily hardware oriented) are suggested.

The Impact of Visual Feedback Type on the Mastery of Visuo-Motor Transformations

2012 ◽  
Vol 220 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Sandra Sülzenbrück
Keyword(s):  
Empirical Research ◽  
Visual Feedback ◽  
Closed Loop ◽  
Motor Planning ◽  
Visual Input ◽  
Closed Loop Control ◽  
Loop Control ◽  
Feedback Type ◽  
Effective Use ◽  
The Impact

For the effective use of modern tools, the inherent visuo-motor transformation needs to be mastered. The successful adjustment to and learning of these transformations crucially depends on practice conditions, particularly on the type of visual feedback during practice. Here, a review about empirical research exploring the influence of continuous and terminal visual feedback during practice on the mastery of visuo-motor transformations is provided. Two studies investigating the impact of the type of visual feedback on either direction-dependent visuo-motor gains or the complex visuo-motor transformation of a virtual two-sided lever are presented in more detail. The findings of these studies indicate that the continuous availability of visual feedback supports performance when closed-loop control is possible, but impairs performance when visual input is no longer available. Different approaches to explain these performance differences due to the type of visual feedback during practice are considered. For example, these differences could reflect a process of re-optimization of motor planning in a novel environment or represent effects of the specificity of practice. Furthermore, differences in the allocation of attention during movements with terminal and continuous visual feedback could account for the observed differences.

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