Optimal and Robust Control of Magnetohydrodynamic Channel Flow Instabilities

2006 ◽  
Author(s):  
Karim Debbagh ◽  
Patricia Cathalifaud ◽  
Christophe Airiau
Keyword(s):  
Magnetic Field ◽  
Channel Flow ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Optimal Perturbation ◽  
Loop Control ◽  
Full State ◽  
Robust Formulation ◽  
Magnetohydrodynamic Channel ◽  
Normal Magnetic Field

Active closed-loop control of subcritical and supercritical instabilities amplified in a channel flow submitted to a constant normal magnetic field is investigated. The control is carried out at both the upper and the lower wall by blowing and suction or by a perturbation of the normal magnetic field. A robust formulation (H∞) of the control has been performed to take into account uncertainties coming from the state disturbances and the measurement noise. Optimal and robust dynamic controls have been tested, with full state information or only wall informations. As expected, we found that the closed-loop control modifies the optimal perturbation. However the lift-up mechanisms are still in action. In the supercritical case we found that the control acts almost exclusively on the unstable mode, whose real part becomes negative.

Positioning and Active Damping of Spring-Mass Systems

1989 ◽  
Vol 111 (4) ◽  
pp. 592-599 ◽  
Author(s):  
T. L. Vincent ◽  
S. P. Joshi ◽  
Yeong Ching Lin
Keyword(s):  
Optimal Control Theory ◽  
Closed Loop ◽  
Open Loop ◽  
Closed Loop Control ◽  
Energy Methods ◽  
Loop Control ◽  
State Variable ◽  
Feedback Design ◽  
Full State ◽  
Control Saturation

In this paper, we investigate an alternate approach to the design of controllers for positioning and damping of a system which can be reduced to an equivalent system of springs and masses. The approach taken is to design a controller which uses open-loop positioning followed by closed-loop control for damping. By so doing, we can avoid a conflicting requirements problem associated with traditional state variable feedback design. The open-loop portion of the control is based on optimal control theory, which allows for control saturation. In particular, during this phase of the control, the time to position is minimized. This results in a bang-bang type of control. Once the system has been “positioned,” the controller switches to a closed-loop phase. The particular closed-loop control used here is based on energy methods and is not a full state variable feedback design. The method is illustrated using a low-order spring-mass example, and the results are compared with an LQ design.

Dynamic Interaction in a Slewing Motor-Beam System: Closed Loop Control

1993 ◽  
Author(s):  
J. J. Sah ◽  
J. S. Lin ◽  
Agamemnon L. Crassidis ◽  
Roger W. Mayne
Keyword(s):  
Closed Loop ◽  
Gear Ratio ◽  
Dynamic Interaction ◽  
Closed Loop Control ◽  
Loop Control ◽  
Full State ◽  
Full State Feedback ◽  
Beam Interaction ◽  
Behavior Systems ◽  
And Behavior

Abstract This paper considers the dynamic interaction between a DC motor and its slewing beam load. The system is described in terms of dimensionless parameters which generalize the results and define the tendency for interaction between the motor and beam. The study focuses on the performance and behavior of the system under closed-loop control. Motor-beam arrangements with differing amounts of dynamic interaction are defined by simple adjustments in gear ratio for a specified motor and beam. Each of these systems is controlled with full state feedback and various forms of output feedback. Controller performance is optimized in each case and the systems are compared to evaluate the effect of motor-beam interaction on the closed-loop system behavior. Systems with an appropriate amount of motor-beam interaction tend to be easier to control and require modest amounts of actuation effort. Systems with little motor-beam interaction are especially prone to beam vibrations and require feedback of beam motions for good closed-loop performance. Those systems with excessive interaction require stabilization efforts to obtain good transient performance and tend to consume increased levels of actuation energy.

scholarly journals Enhanced real-time pose estimation for closed-loop robotic manipulation of magnetically actuated capsule endoscopes

2018 ◽  
Vol 37 (8) ◽  
pp. 890-911 ◽  
Author(s):  
Addisu Z Taddese ◽  
Piotr R Slawinski ◽  
Marco Pirotta ◽  
Elena De Momi ◽  
Keith L Obstein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pose Estimation ◽  
Closed Loop ◽  
Estimation Methods ◽  
Closed Loop Control ◽  
Point Dipole ◽  
Magnetic Actuation ◽  
Loop Control ◽  
Magnetically Actuated ◽  
Capsule Endoscopes

Pose estimation methods for robotically guided magnetic actuation of capsule endoscopes have recently enabled trajectory following and automation of repetitive endoscopic maneuvers. However, these methods face significant challenges in their path to clinical adoption including the presence of regions of magnetic field singularity, where the accuracy of the system degrades, and the need for accurate initialization of the capsule’s pose. In particular, the singularity problem exists for any pose estimation method that utilizes a single source of magnetic field if the method does not rely on the motion of the magnet to obtain multiple measurements from different vantage points. We analyze the workspace of such pose estimation methods with the use of the point-dipole magnetic field model and show that singular regions exist in areas where the capsule is nominally located during magnetic actuation. As the dipole model can approximate most magnetic field sources, the problem discussed herein pertains to a wider set of pose estimation techniques. We then propose a novel hybrid approach employing static and time-varying magnetic field sources and show that this system has no regions of singularity. The proposed system was experimentally validated for accuracy, workspace size, update rate, and performance in regions of magnetic singularity. The system performed as well or better than prior pose estimation methods without requiring accurate initialization and was robust to magnetic singularity. Experimental demonstration of closed-loop control of a tethered magnetic device utilizing the developed pose estimation technique is provided to ascertain its suitability for robotically guided capsule endoscopy. Hence, advances in closed-loop control and intelligent automation of magnetically actuated capsule endoscopes can be further pursued toward clinical realization by employing this pose estimation system.

A Dexterous Surgical Manipulation Tool Using Self-Sensing Magnetoelectric Actuators

2010 ◽  
Author(s):  
Yezuo Wang ◽  
Jayasimha Atulasimha
Keyword(s):  
Magnetic Field ◽  
Control System ◽  
Closed Loop ◽  
Electrical Signal ◽  
Closed Loop Control ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Specific Configuration ◽  
Surgical Manipulation

In this paper, a dexterous surgical manipulation tool is developed, and characterized using a magnetoelectric self-sensing actuator. The magnetoelectric actuator is made up of three magnetoelectric cantilevers, which are mounted in a specific configuration. Each of the magnetoelectric cantilevers is composed of Galfenol and PZT-5H. The device consists of a single larger magnetoelectric cantilever that is capable of producing an up-down movement upon remote application of a magnetic field to the magnetostrictive layer. Towards one of the ends of this actuator two smaller magnetoelectric cantilevers are attached that are capable of producing a deflection in a side-ways direction making them well suited for gripping action. The shape-anisotropy of the magnetostrictive layers is designed to ensure a controlled sequence of gripping action and up-down movement when these cantilevers are actuated via a remote magnetic field which induces bending in them. The electrical signal generated by the piezoelectric layer is used to provide a sensing signal for both tactile sensing (and gripping) and deflection. This can be used in a closed loop control system.

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.

118-LB: Glucose Variability throughout the Menstrual Cycle on Closed-Loop Control in Type 1 DM

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 118-LB
Author(s):  
CAROL J. LEVY ◽  
GRENYE OMALLEY ◽  
SUE A. BROWN ◽  
DAN RAGHINARU ◽  
YOGISH C. KUDVA ◽  
...  
Keyword(s):  
Menstrual Cycle ◽  
Closed Loop ◽  
Glucose Variability ◽  
Closed Loop Control ◽  
Loop Control ◽  
Type 1 Dm
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