Progress of liquid crystal adaptive optics for applications in ground-based telescopes

2020 ◽  
Vol 494 (3) ◽  
pp. 3536-3540
Author(s):  
Xingyun Zhang ◽  
Zhaoliang Cao ◽  
Quanquan Mu ◽  
Dayu Li ◽  
Zenghui Peng ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Liquid Crystal ◽  
Adaptive Optics ◽  
Low Cost ◽  
Response Speed ◽  
Open Loop ◽  
Loop Control ◽  
Compact Size ◽  
Control Scheme ◽  
Resolution Imaging

ABSTRACT Liquid crystal (LC) adaptive optics systems (AOS) can potentially be used in ground-based large aperture telescopes, because of their high spatial resolution, low cost and compact size. However, their disadvantages, such as low energy efficiency and slow response speed, still hinder their application. In this paper, we demonstrate solutions to these problems. With newly synthesized fast nematic LC material and using an overdriving technique, the response time of a LC wavefront corrector was reduced to 0.75 ms. Under an open-loop control scheme, a novel optical system was designed to improve the energy efficiency of LC AOS. With those problems resolved, a LC AOS was built for a 1.23-m telescope. This system has a disturbance rejection bandwidth of 80 Hz, and could fully use the energy of 400–900 nm wavebands. Observation results showed that the diffraction limit resolution imaging of the telescope could be obtained after correction, which indicates that the LC AOS is ready to be used in ground-based telescopes for visible waveband imaging.

Performance simulation of an adaptive optics system with liquid crystal corrector under closed-loop and open-loop control

2010 ◽  
Vol 283 (10) ◽  
pp. 2017-2019 ◽  
Author(s):  
Quanquan Mu ◽  
Zhaoliang Cao ◽  
Zenghui Peng ◽  
Yonggang Liu ◽  
Lifa Hu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Adaptive Optics ◽  
Closed Loop ◽  
Open Loop ◽  
Open Loop Control ◽  
Performance Simulation ◽  
Loop Control ◽  
Adaptive Optics System

Towards the Design of a Fully Actuated Invertible Flying Quadrotor MAV

2013 ◽  
Author(s):  
Andreas Gelardos ◽  
David J. Cappelleri
Keyword(s):  
Closed Loop ◽  
Mechanical Design ◽  
Low Cost ◽  
Open Loop ◽  
Transmission Mechanism ◽  
Micro Aerial Vehicle ◽  
Loop Control ◽  
Minimal Weight ◽  
Control Scheme ◽  
Aerial Vehicle

In this paper, we present the transmission mechanism design for a fully actuated Invertible Flying Quadrotor (IFQ) micro aerial vehicle (MAV). At the heart of the mechanism is a gearbox which couples and counter rotates two pairs of shafts that have the quadrotor propellers mounted at their ends. This mechanism will allow for the IFQ to follow aggressive maneuvers, hover at an arbitrary attitude, and have sustained inverted flight capabilities. The paper presents the mechanical design challenges and solutions in designing such a transmission mechanism with minimal weight along with low cost and easy manufacturing. The dynamic model for the IFQ MAV is presented along with an optimal open loop trajectory control scheme and related simulations. An approach for a full closed loop control scheme is also discussed. A prototype of the mechanism has been manufactured and functionally tested. The entire transmission mechanism was able to be prototyped with a weight of only approximately 100 grams.

scholarly journals Automatic locking of a parametrically resonating, base-excited, nonlinear beam

2021 ◽  
Author(s):  
Nir Ben Shaya ◽  
Izhak Bucher ◽  
Amit Dolev
Keyword(s):  
Relative Phase ◽  
Closed Loop ◽  
Dynamical Behavior ◽  
Open Loop ◽  
Vibration Modes ◽  
Nonlinear Structure ◽  
Nonlinear Beam ◽  
Loop Control ◽  
Control Scheme ◽  
Slender Beams

AbstractDescribed is a closed-loop control scheme capable of stabilizing a parametrically excited nonlinear structure in several vibration modes. By setting the relative phase between the spatially filtered response and the excitation, the open-loop unstable solution branches are stabilized under a 2:1 parametric excitation of a chosen mode of vibration. For a given phase, the closed-loop automatically locks on a limit cycle, through an Autoresonance scheme, at any desired point on the solution branches. Axially driven slender beams and nanowires develop large transverse vibration under suitable amplitudes and frequency base-excitation that are sensitive to small potential coupled field. To utilize such a structure as a sensor, stable and robust operation are made possible by the control scheme. In addition, an optimal operating point with large sensitivity to the sensed potential field can be set using phase as a tunable parameter. Detailed analysis of the dynamical behavior, experimental verifications, and demonstrations sheds light on some features of the system dynamics.

An Integrated Design for a CNC Machine

2014 ◽  
pp. 254-265
Author(s):  
Amro Shafik ◽  
Salah Haridy
Keyword(s):  
Low Cost ◽  
Integrated Design ◽  
Numerical Data ◽  
Open Loop ◽  
Numerical Control ◽  
Future Research ◽  
Cnc Machine ◽  
Loop Control ◽  
Loop Control System ◽  
Stepper Motors

Computer Numerical Control (CNC) is a technology that converts coded instructions and numerical data into sequential actions that describe the motion of machine axes or the behavior of an end effector. Nowadays, CNC technology has been introduced to different stages of production, such as rapid prototyping, machining and finishing processes, testing, packaging, and warehousing. The main objective of this chapter is to introduce a methodology for design and implementation of a simple and low-cost educational CNC prototype. The machine consists of three independent axes driven by stepper motors through an open-loop control system. Output pulses from the parallel port of Personal Computer (PC) are used to drive the stepper motors after processing by an interface card. A flexible, responsive, and real-time Visual C# program is developed to control the motion of the machine axes. The integrated design proposed in this chapter can provide engineers and students in academic institutions with a simple foundation to efficiently build a CNC machine based on the available resources. Moreover, the proposed prototype can be used for educational purposes, demonstrations, and future research.

SIMULATION OF CO-PLANAR WAVEGUIDE LIQUID CRYSTAL BASED PHASE SHIFTER

2015 ◽  
Vol 77 (10) ◽  
Author(s):  
Nasser A ALQuaiti ◽  
Noor Asniza Murad
Keyword(s):  
Liquid Crystal ◽  
Phase Shift ◽  
Phase Shifter ◽  
Low Cost ◽  
Continuous Phase ◽  
Phase Shifting ◽  
Telecommunication System ◽  
Liquid Crystal Material ◽  
Compact Size ◽  
5Cb Liquid Crystal

This paper discussed the design and performances of a liquid crystal phase shifter that can be used in tuning devices. Tuning devices growth with the demand in the emerging in telecommunication system. Tuning devices with smooth continuous phase shifting at low cost and compact size would be an advantage. This paper proposed a phase shifter using 5CB liquid crystal material. The advantages of using the material is the smoothness and continuity of the transitions in the phase shift. It is done by having a structure with cavity filled with the liquid crystal and applied with certain voltage that can be changed. The changes in voltage would change the applied electric field, and thus would change the permittivity of the material. The changes would affect the wave propagation and thus contribute to the phase shifting. The performance of the phase shifter was tested by means of simulation using CST Suite 2014 software. The results show that the higher the frequency, the higher the phase shift would occur. The highest FoM achieved is 68 (deg/dB) at 8 GHz. A phase shifter with smooth and continuous phase shift can be used as the feeding network in an array scanning antennas systems.

Modeling and Control of a Rotary Crane

1985 ◽  
Vol 107 (3) ◽  
pp. 200-206 ◽  
Author(s):  
Y. Sakawa ◽  
A. Nakazumi
Keyword(s):  
Feedback Control ◽  
Equilibrium State ◽  
Open Loop ◽  
The State ◽  
Control Input ◽  
Loop Control ◽  
Modeling And Control ◽  
Control Scheme ◽  
Rotary Crane ◽  
And Control

In this paper we first derive a dynamical model for the control of a rotary crane, which makes three kinds of motion (rotation, load hoisting, and boom hoisting) simultaneously. The goal is to transfer a load to a desired place in such a way that at the end of transfer the swing of the load decays as quickly as possible. We first apply an open-loop control input to the system such that the state of the system can be transferred to a neighborhood of the equilibrium state. Then we apply a feedback control signal so that the state of the system approaches the equilibrium state as quickly as possible. The results of computer simulation prove that the open-loop plus feedback control scheme works well.

Research and Design of Control System for a 3-DOF Hybrid Robot

2010 ◽  
Vol 43 ◽  
pp. 207-210 ◽  
Author(s):  
Ju Li ◽  
Hui Ping Shen ◽  
Y.X. Jiang ◽  
Jia Ming Deng ◽  
Shan Shu Liu ◽  
...  
Keyword(s):  
Control System ◽  
Low Cost ◽  
Hybrid Structure ◽  
Open Loop ◽  
The Body ◽  
Step Motor ◽  
Parallel Structure ◽  
Loop Control ◽  
Loop Control System ◽  
Research And Design

This paper studied a novel 3-DOF hybrid robot, and invented a new hybrid structure which was composed of 2-DOF parallel structure and 1-DOF serial structure. The structure of this mechanism was simple, stiffness and positioning accuracy was high. The control system based on ARM micro-controller was a step motor open-loop control system, which features compact and low cost while the control accuracy can be guaranteed. In this paper, the body composition of the robot was described, and its inverse kinematics were derived and further simplified. Hardware and software of the motion control system was designed in detail and experimented through prototype.

The Design of Spraying Manipulator Control System in Mines

2014 ◽  
Vol 602-605 ◽  
pp. 1157-1160
Author(s):  
Mei Yu ◽  
Guo Wei Liu ◽  
Bing Kong
Keyword(s):  
Control System ◽  
Position Control ◽  
Low Cost ◽  
Open Loop ◽  
Open Loop Control ◽  
Mining Equipment ◽  
Loop Control ◽  
Precise Position ◽  
Loop Control System ◽  
Manipulator Control

In view of the present mining spraying manipulator operation is not flexible ,spraying effect is poor, susceptible to interference and other issues, this paper studies and realizes a kind of low cost, strong practicability of spraying manipulator control system. Using S7-200PLC and 2MA860H drive to control the 86BYG250A stepper motor open-loop control system, and the precise position control is realized. By controlling of the x-y axis mine spraying manipulator. Validate the system operation is simple, highly efficient and stable, energy conservation and environmental protection, strong anti-jamming capability, it can be widely used in all kinds of mining equipment.

Motion Control Analysis of the Fruit-Trees Robot

2011 ◽  
Vol 135-136 ◽  
pp. 1179-1182
Author(s):  
Jia Ao Yu ◽  
Min Cang Fu
Keyword(s):  
Pid Control ◽  
Control Algorithm ◽  
Response Speed ◽  
Fruit Trees ◽  
Open Loop ◽  
Control Analysis ◽  
Open Loop Control ◽  
Loop Control ◽  
Straight Line ◽  
Motor Control System

The article tracks the fruit-trees robot, and analyzes the fruit-trees robot’s dual-motor control system. Based on the speed incremental PID closed-loop control algorithm of the step DC motor, the PID controller’s proportional coefficient, integral coefficient and differential coefficient is concluded. It demonstrates from the stimulations and experiments that the usage of speed incremental PID control do better at the response speed and stability than the open-loop control motor when the robot is run by a straight line on the ground at the 3000rpm.

Open loop adaptive optics testbed on 2.16meter telescope with liquid crystal corrector

2012 ◽  
Vol 285 (6) ◽  
pp. 896-899 ◽  
Author(s):  
Quanquan Mu ◽  
Zhaoliang Cao ◽  
Lifa Hu ◽  
Yonggang Liu ◽  
Zenghui Peng ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Adaptive Optics ◽  
Open Loop
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