scholarly journals Limit Cycle Behavior of Smart Fluid Dampers Under Closed Loop Control

2005 ◽  
Vol 128 (4) ◽  
pp. 413-428 ◽  
Author(s):  
Neil D Sims
Keyword(s):  
Limit Cycle ◽  
Closed Loop ◽  
Controller Design ◽  
Nonlinear Models ◽  
Control Strategies ◽  
Nonlinear Behavior ◽  
Closed Loop Control ◽  
Loop Control ◽  
Fluid Dampers ◽  
Limit Cycle Behavior

Semiactive vibration dampers offer an attractive compromise between the simplicity and fail safety of passive devices, and the weight, cost, and complexity of fully active systems. In addition, the dissipative nature of semiactive dampers ensures they always remain stable under closed loop control, unlike their fully active counterparts. However, undesirable limit cycle behavior remains a possibility, which is not always properly considered during the controller design. Smart fluids provide an elegant means to produce semiactive damping, since their resistance to flow can be directly controlled by the application of an electric or magnetic field. However, the nonlinear behavior of smart fluid dampers makes it difficult to design effective controllers, and so a wide variety of control strategies has been proposed in the literature. In general, this work has overlooked the possibility of undesirable limit cycle behavior under closed loop conditions. The aim of the present study is to demonstrate how the experimentally observed limit cycle behavior of smart dampers can be predicted and explained by appropriate nonlinear models. The study is based upon a previously developed feedback control strategy, but the techniques described are relevant to other forms of smart damper control.

EVALUATION OF CLOSED-LOOP CONTROL SYSTEM FOR RESTORING STANDING AND SITTING FUNCTIONS BY FUNCTIONAL ELECTRICAL STIMULATION

2005 ◽  
Vol 17 (01) ◽  
pp. 19-26 ◽  
Author(s):  
CHENG-LIANG LIU ◽  
CHUNG-HUANG YU ◽  
SHIH-CHING CHEN ◽  
CHANG-HUNG CHEN
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Closed Loop ◽  
Spinal Cord Injuries ◽  
Control Method ◽  
Control Strategies ◽  
Evaluation Process ◽  
Closed Loop Control ◽  
Loop Control ◽  
Loop Control System

Functional electrical stimulation (FES) is a method for restoring the functional movements of paraplegic or patients with spinal cord injuries. However, the selection of parameters that control the restoration of standing up and sitting functions has not been extensively investigated. This work provides a method for choosing the four main items involved in evaluating the strategies for sit-stand-sit movements with the aid of a modified walker. The control method uses the arm-supported force and the angles of the legs as feedback signals to change the intensity of the electrical stimulation of the leg muscles. The control parameters, Ki and Kp, are vary for different control strategies. Four items are collected through questionnaires and used for evaluation. They are the maximum reactions of the two hands, the average reaction of the two hands, largest absolute angular velocity of the knee joints, and the sit-stand-sit duration time. The experimental data are normalized to facilitate comparison. Weighting factors are obtained and analyzed from questionnaires answered by experts and are added to evaluation process for manipulation. The results show that the best strategy is the closed-loop control with parameters Ki=0.5 and Kp=0.

scholarly journals Neural Network-Based State Estimation for a Closed-Loop Control Strategy Applied to a Fed-Batch Bioreactor

Complexity ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Santiago Rómoli ◽  
Mario Serrano ◽  
Francisco Rossomando ◽  
Jorge Vega ◽  
Oscar Ortiz ◽  
...  
Keyword(s):  
Neural Network ◽  
Closed Loop ◽  
Rbf Neural Network ◽  
Control Strategies ◽  
Tracking Error ◽  
Closed Loop Control ◽  
Online Information ◽  
Fed Batch ◽  
Loop Control ◽  
Batch Bioreactor

The lack of online information on some bioprocess variables and the presence of model and parametric uncertainties pose significant challenges to the design of efficient closed-loop control strategies. To address this issue, this work proposes an online state estimator based on a Radial Basis Function (RBF) neural network that operates in closed loop together with a control law derived on a linear algebra-based design strategy. The proposed methodology is applied to a class of nonlinear systems with three types of uncertainties: (i) time-varying parameters, (ii) uncertain nonlinearities, and (iii) unmodeled dynamics. To reduce the effect of uncertainties on the bioreactor, some integrators of the tracking error are introduced, which in turn allow the derivation of the proper control actions. This new control scheme guarantees that all signals are uniformly and ultimately bounded, and the tracking error converges to small values. The effectiveness of the proposed approach is illustrated on the basis of simulated experiments on a fed-batch bioreactor, and its performance is compared with two controllers available in the literature.

scholarly journals Control of Flexible Manipulator Systems

1996 ◽  
Vol 210 (2) ◽  
pp. 113-130 ◽  
Author(s):  
M O Tokhi ◽  
A K M Azad
Keyword(s):  
Closed Loop ◽  
Control Strategies ◽  
Open Loop ◽  
Flexible Manipulator ◽  
Closed Loop Control ◽  
Loop Control ◽  
Acceleration Feedback ◽  
Low Pass ◽  
Input Torque ◽  
Collocated Control

This paper presents an investigation into the development of open-loop and closed-loop control strategies for flexible manipulator systems. Shaped torque inputs, including Gaussian-shaped and low-pass (Butter-worth and elliptic) filtered input torque functions, are developed and used in an open-loop configuration and their performance studied in comparison to a bang-bang input torque through experimentation on a single-link flexible manipulator system. Closed-loop control strategies that use both collocated (hub angle and hub velocity) and non-collocated (end-point acceleration) feedback are then proposed. A collocated proportional and derivative (PD) control is first developed and its performance studied through experimentation. The collocated control is then extended to incorporate, additionally, non-collocated feedback through a proportional integral derivative (PID) configuration. The performance of the hybrid collocated and non-collocated control strategy thus developed is studied through experimentation. Experimental results verifying the performance of the developed control strategies are presented and discussed.

Trajektorienbasierte Strategie für die Regelung des Tiefziehprozesses während des Hubes*/Trajectory-based closed loop control for controlling deep-drawing process

2016 ◽  
Vol 106 (10) ◽  
pp. 684-689
Author(s):  
M. Prof. Liewald ◽  
M. Barthau ◽  
S. Braun
Keyword(s):  
Deep Drawing ◽  
Closed Loop ◽  
Control Strategies ◽  
Closed Loop Control ◽  
Drawing Process ◽  
Control Loop ◽  
Deep Drawing Process ◽  
Loop Control ◽  
Control Intervention ◽  
Measurement Devices

Am IFU der Universität Stuttgart wurde ein Regelkreis für das Tiefziehen entwickelt, welcher einen regelnden Eingriff in den Tiefziehvorgang während des Hubes erlaubt. Die Umsetzung dieses Regelungskonzeptes erfolgte mittels eines Ziehwerkzeugs, das an eine vereinfachte Geometrie eines PKW-Vorderkotflügels angelehnt ist. Beschrieben werden die messtechnische Ausstattung des Versuchswerkzeugs, der Aufbau des Regelkreises und die Entwicklung der Regelstrategie. Des Weiteren werden die Ergebnisse der Simulation sowie der ersten Versuche dargestellt.   At IFU, University of Stuttgart a control loop for deep-drawing process, with control intervention during deep-drawing stroke was developed. The closed-loop control was demonstrated on a fender shaped geometry. Described are the measurement devices, design of the closed-loop and the featured control strategies. Results of simulation and sensitivity analysis are also shown.

Development of Hardware Simulator and Controller for Web Transport Process

2005 ◽  
Vol 128 (1) ◽  
pp. 378-381 ◽  
Author(s):  
Jeetae Kim
Keyword(s):  
Force Control ◽  
Transport Process ◽  
Closed Loop ◽  
Controller Design ◽  
Transport Model ◽  
Tension Force ◽  
Closed Loop Control ◽  
Measuring Device ◽  
Loop Control ◽  
Process Simulator

In this study a hardware simulator and controller for web transport process are developed. First the dynamics of web transport process is analyzed for simulator and controller design. An example Polypropylene transport process is investigated and its simplified transport model is derived. Then the web transport process simulator and its controller are developed. Accurate tension force control is needed to produce high quality web formed materials. The process controller uses the loadcell as a tension measuring device and closed-loop control is used for tension force regulation. The response of the system is tested under the disturbances in tension and the experimental results show that the system regulates tension disturbances properly.

Controller Design for Active Closed-Loop Control of Cavity Flows

2004 ◽  
Author(s):  
Hitay Ozbay ◽  
Onder Efe ◽  
Mo Samimy ◽  
Edgar Caraballo ◽  
Jim DeBonis ◽  
...  
Keyword(s):  
Closed Loop ◽  
Controller Design ◽  
Closed Loop Control ◽  
Cavity Flows ◽  
Loop Control

Design and simulation of a novel FOIMC-PD/P double-loop control structure for CSTRs and bioreactors

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shweta Kumari ◽  
Pulakraj Aryan ◽  
G. Lloyds Raja
Keyword(s):  
Fractional Order ◽  
Closed Loop ◽  
Nonlinear Models ◽  
Control Strategies ◽  
Process Models ◽  
Tuning Parameter ◽  
Double Loop ◽  
Outer Loop ◽  
Loop Control ◽  
Inverse Response

Abstract The design of control methods for unstable plants is somewhat complex than that of stable plants. This is because unstable process models contain one or more poles lying on the right of the s-plane which yields unbounded closed-loop response. Further, the presence of the dead-time induces more complexity as it decreases the gain and phase margins which in turn deteriorates the closed-loop performance. The design of control strategies become more challenging for plants of unstable nature with positive zeros because they exhibit a phenomenon called inverse response. This paper suggests a method to design a double-loop scheme for unstable plants with/without inverse response. Accordingly, a proportional-derivative (PD)/proportional (P) controllers are used in the inner-loop for stabilizing the plant. A fractional order internal model controller (FOIMC) scheme is used to obtain the outer-loop controller using the stabilized plant model. The P/PD controller settings have been obtained by using the Routh-stability criteria and the maximum sensitivity approach. Procedure for selecting the outer-loop tuning parameter and fractional order is also given. Linear and nonlinear models of unstable plants including bioreactors and isothermal chemical reactors are used to demonstrate the merits of the suggested strategy. Robustness of the design and effect of measurement noise are also studied. Integrated absolute/squared error measures are also calculated. The suggested design is found to be more effective in controlling unstable processes than some reported works.

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