Closed-loop control of resonant tunneling diode barrier thickness using in situ spectroscopic ellipsometry

2000 ◽  
Vol 18 (3) ◽  
pp. 1439 ◽  
Author(s):  
J. A. Roth ◽  
W. S. Williamson ◽  
D. H. Chow ◽  
G. L. Olson ◽  
B. Johs
Keyword(s):  
Spectroscopic Ellipsometry ◽  
Resonant Tunneling ◽  
Closed Loop ◽  
Resonant Tunneling Diode ◽  
Closed Loop Control ◽  
Barrier Thickness ◽  
Loop Control ◽  
Tunneling Diode

Closed-Loop Thickness Control of Resonant-Tunneling Diode Mbe Growth Using Spectroscopic Ellipsometry

1995 ◽  
Vol 406 ◽  
Author(s):  
F. G. Celii ◽  
Y.-C. Kao ◽  
T. S. Moise ◽  
M. Woolsey ◽  
T. B. Harton ◽  
...  
Keyword(s):  
Spectroscopic Ellipsometry ◽  
Resonant Tunneling ◽  
Closed Loop ◽  
Dead Reckoning ◽  
Resonant Tunneling Diode ◽  
Short Term ◽  
Thickness Control ◽  
Loop Control ◽  
Tunneling Diode

AbstractThe room temperature electrical characteristics of AlAs/InGaAs/InAs resonant-tunneling diode (RTD) devices are sensitive to sub-monolayer thickness changes, and present a challenging case for closed-loop control. We prepared stacked RTD structures by MBE in which the strained AlAs barrier thicknesses were controlled based on an in situ spectroscopic ellipsometry (SE) system. The short-term and long-term reproducibility of RTDs grown under SE-based control was compared with similar samples grown by “dead-reckoning” (timing-based shutter openings coupled with pre-growth flux calibrations). SE-based calibration can compensate for long-term flux drift, but closed-loop thickness control did not provide a significant improvement over deadreckoning in terms of short-term RTD reproducibility.

scholarly journals In situ measurement and closed-loop control for powder supply processes

2021 ◽  
Author(s):  
Philipp Peter Breese ◽  
Tobias Hauser ◽  
Daniel Regulin ◽  
Stefan Seebauer ◽  
Christian Rupprecht
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Closed Loop ◽  
In Situ Measurement ◽  
Closed Loop Control ◽  
Loop Control ◽  
Powder Feeder ◽  
Powder Mass

AbstractThe powder mass flow rate is one of the main parameters regarding the geometrical precision of built components in the additive manufacturing process of laser metal deposition. However, its accuracy, constancy, and repeatability over the course of the running process is not given. Reasons among others are the performance of the powder conveyors, the complex nature of the powder behavior, and the resulting issues with existing closed-loop control approaches. Additionally, a direct in situ measurement of the powder mass flow rate is only possible with intrusive methods. This publication introduces a novel approach to measure the current powder mass flow rate at a frequency of 125 Hz. The volumetric powder flow evaluation given by a simple optical sensor concept was transferred to a mass flow rate through mathematical dependencies. They were found experimentally for a nickel-based powder (Inconel 625) and are valid for a wide range of mass flow rates. With this, the dynamic behavior of a vibration powder feeder was investigated and a memory effect dependent on previous powder feeder speeds was discovered. Next, a closed-loop control with the received sensor signal was implemented. The concept as a whole gives a repeatable and accurate powder mass flow rate while being universally retrofittable and applicable. In a final step, the improved dynamic and steady performance of the powder mass flow rate with closed-loop control was validated. It showed a reduction of mean relative errors for step responses of up to 81% compared to the uncontrolled cases.

The Application of PLC in the Stepper Motor Closed-Loop Control System Design

2012 ◽  
Vol 605-607 ◽  
pp. 1537-1540 ◽  
Author(s):  
Xiao Yu Wang
Keyword(s):  
Control System ◽  
Closed Loop ◽  
Low Cost ◽  
Stepper Motor ◽  
Closed Loop Control ◽  
Loop Control ◽  
Closed Loop Control System ◽  
System Flow ◽  
Loop Control System

The application of PLC 、Stepper motor driver and Encoder are introduced in stepper motor closed-loop control system. The Principle diagram is analyzed, the Control System flow chart and Software program are designed. Through in-situ operation, the system has been proved well reliability、 stability and simplicity , achieved high accuracy and low cost requirements。

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.

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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