Number and Distribution of Fiducial Fibres in a Spectroscopic Survey Telescope

2021 ◽  
Author(s):  
Shipeng Duan ◽  
Zengxiang Zhou ◽  
Jiale Zuo ◽  
Mengtao Li ◽  
Zhigang Liu ◽  
...  
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Astronomical Observation ◽  
Detection Accuracy ◽  
Optical Fibres ◽  
Feedback Control System ◽  
Swarm Optimization ◽  
Focal Surface ◽  
Loop Feedback ◽  
Closed Loop Feedback

Abstract To date, the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) has been in operation for 12 years. To improve the telescope’s astronomical observation accuracy, the original open-loop fibre positioning system of LAMOST is in urgent need of upgrading. The upgrade plan is to locate several fibre view cameras (FVCs) around primary mirror B to build a closed-loop feedback control system. The FVCs are ~20 m from the focal surface. To reduce a series of errors when the cameras detect the positions of the optical fibres, we designed fiducial fibres on the focal surface to be fiducial points for the cameras. Increasing the number of fiducial fibres can improve the detection accuracy of the FVC system, but it will also certainly reduce the number of fibre positioners that can be used for observation. Therefore, the focus of this paper is how to achieve the quantity and distribution that meet the requirements of system detection. In this paper, we introduce the necessity of using fiducial fibres, propose a method for selecting their number, and present several methods for assessing the uniformity of their distribution. Finally, we use particle swarm optimization to find the best distribution of fiducial fibres.

Stability analysis in machining process by using adaptive closed-loop feedback control system in turning process

2020 ◽  
pp. 107754632095261
Author(s):  
Kashfull Orra ◽  
Sounak K Choudhury
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Closed Loop ◽  
Machining Process ◽  
Feedback Control System ◽  
Turning Process ◽  
Tool Vibration ◽  
Loop Feedback ◽  
Closed Loop Feedback ◽  
The Stability

The study presents model-based mechanism of nonlinear cutting tool vibration in turning process and the strategy of improving cutting process stability by suppressing machine tool vibration. The approach used is based on the closed-loop feedback control system with the help of electro–magneto–rheological damper. A machine tool vibration signal generated by an accelerometer is fed back to the coil of a damper after suitable amplification. The damper, attached under the tool holder, generates counter forces to suppress the vibration after being excited by the signal in terms of current. The study also discusses the use of transfer function approach for the development of a mathematical model and adaptively controlling the process dynamics of the turning process. The purpose of developing such mechanism is to stabilize the machining process with respect to the dynamic uncut chip thickness responsible for the type-II regenerative effect. The state-space model used in this study successfully checked the adequacy of the model through controllability and observability matrices. The eigenvalue and eigenvector have confirmed the stability of the system more accurately. The characteristic of the stability lobe chart is discussed for the present model-based mechanism.

Feedback and Mapping Control of Natural Gas Engines

2002 ◽  
Author(s):  
Greg Sorge
Keyword(s):  
Natural Gas ◽  
Control Systems ◽  
Closed Loop ◽  
Open Loop ◽  
Natural Gas Engines ◽  
Feedback Type ◽  
History Of ◽  
Loop Feedback ◽  
Closed Loop Feedback ◽  
The 19Th Century

Automatic controls have been used on all types of machinery since the first complicated machines became popular in the 19th century. Controls are used to maintain pressures, temperatures, operating speeds, flows and many other operating parameters. Natural gas engines have used a variety of controls for various purposes since the first natural gas engines were produced. This paper will discuss the history of mechanical controls used on natural gas engines and the introduction and application of electronic controls. The paper will discuss open loop (mapping) and closed loop (feedback) type controls and common applications of each. Mechanical control systems such as governors, fuel regulators, fuel mixing valves, thermostats, and turbocharger wastegates will be discussed and classified as open or closed loop controls. Electronic control systems such as governors, air/fuel ratio controls, detonation controls, and turbocharger controls will also be discussed and classified. This paper will also discuss state of the art controls which perform numerous functions to get desired performance, and can be communicated with remotely.

scholarly journals Closed-loop feedback control for microfluidic systems through automated capacitive fluid height sensing

2017 ◽  
Author(s):  
L. R. Soenksen ◽  
T. Kassis ◽  
M. Noh ◽  
L.G. Griffith ◽  
D.L. Trumper
Keyword(s):  
Feedback Control ◽  
Closed Loop ◽  
Cost Effective ◽  
Capacitive Sensor ◽  
Open Loop ◽  
Small Scale ◽  
Microfluidic Systems ◽  
Wide Range ◽  
Loop Feedback ◽  
Closed Loop Feedback

AbstractPrecise fluid height sensing in open-channel microfluidics has long been a desirable feature for a wide range of applications. However, performing accurate measurements of the fluid level in small-scale reservoirs (<1mL) has proven to be an elusive goal, especially if direct fluid-sensor contact needs to be avoided. In particular, gravity-driven systems used in several microfluidic applications to establish pressure gradients and impose flow remain open-loop and largely unmonitored due to these sensing limitations. Here we present an optimized self-shielded coplanar capacitive sensor design and automated control system to provide submillimeter fluid-height resolution (~250 μm) and control of small-scale open reservoirs without the need for direct fluid contact. Results from testing and validation of our optimized sensor and system also suggest that accurate fluid height information can be used to robustly characterize, calibrate and dynamically control a range of microfluidic systems with complex pumping mechanisms, even in cell culture conditions. Capacitive sensing technology provides a scalable and cost-effective way to enable continuous monitoring and closed-loop feedback control of fluid volumes in small-scale gravity-dominated wells in a variety of microfluidic applications.

Closed-Loop Feedback Control Algorithms for Flow Control Over NACA 0015 Airfoil

2011 ◽  
Author(s):  
Sohaib Obeid ◽  
Rataheshwar Jha ◽  
Goodarz Ahmadi
Keyword(s):  
Feedback Control ◽  
Closed Loop ◽  
Moving Average ◽  
Leading Edge ◽  
Open Loop ◽  
Synthetic Jet ◽  
Identification Technique ◽  
Loop Feedback ◽  
Closed Loop Feedback ◽  
Naca 0015

This study investigates control algorithm for closed-loop feedback control system design aimed at reduction of turbulent flow separation over a NACA 0015 airfoil equipped with leading-edge synthetic jet actuators (SJAs). The algorithm employs system identification technique based on Nonlinear Auto Regressive Moving Average with eXogenous inputs (NARMAX) method to model nonlinear dynamics of the flow and design controller for single-input singleoutput systems. The resulting closed loop response tracks the desired pressure value and significant improvement in the transient response over the open-loop system at high angles of attack is realized.

Control of Impact Microactuators for Precise Positioning

2005 ◽  
Vol 1 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Xiaopeng Zhao ◽  
Harry Dankowicz
Keyword(s):  
System Design ◽  
Closed Loop ◽  
Complex Dynamics ◽  
Open Loop ◽  
Operating Conditions ◽  
System Behavior ◽  
Precise Positioning ◽  
Feedback Scheme ◽  
Loop Feedback ◽  
Closed Loop Feedback

Electrically driven impact microactuators generate nanoscale displacements without large driving distances and high voltages. These systems exhibit complex dynamics because of inherent nonlinearities due to impacts, friction, and electric forces. As a result, dramatic changes in system behavior, associated with so-called grazing bifurcations, may occur during the transition between impacting and nonimpacting dynamics, including the presence of robust chaos. For successful open-loop operating conditions, the system design is limited to certain parameter regions, where desired system responses reside. The objective of this paper is to overcome this limitation to allow for a more precise displacement manipulation using impact microactuators. This is achieved through a closed-loop feedback scheme that successfully controls the system dynamics in the near-grazing region.

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