Feed-Forward Adaptive-Optic Correction of Aero-Optical Aberrations Caused by a Two-Dimensional Heated Jet

2005 ◽  
Author(s):  
Daniel Duffin
Keyword(s):  
Adaptive Optic ◽  
Two Dimensional ◽  
Optical Aberrations ◽  
Feed Forward ◽  
Heated Jet

Image Distortion in the Reconstruction of Periodic Images: Effect and Correction

1980 ◽  
Vol 38 ◽  
pp. 684-685
Author(s):  
Jon Rigden ◽  
J.W. Wiggins
Keyword(s):  
Electron Micrographs ◽  
Image Distortion ◽  
Field Of View ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Missing Information ◽  
Optical Aberrations ◽  
Radial Distortion ◽  
Single Number ◽  
Barrel Distortion

There are two electron optical aberrations which are commonly ignored because they are unimportant, even ignored, in most electron micrographs. These aberrations are radial distortion - also known as pincushion or barrel distortion, depending on the sign - and spiral distortion, an effect which never occurs in light optics. They are both illustrated in Figure 1. Since these distortions are generally uninteresting, microscope manufacturers do not provide substantial information about their instruments. Typically, either there is no information at all, or a single number related to the distortion constant is provided with no indication as to where in the field of view it was measured or at what magnification, although both items are needed to actually assess the distortion constant. Taking the most optimistic view of the missing information, one can still determine that radial distortion is a major factor in limiting the resolution attained by Unwin and Henderson in their reconstruction of the two-dimensional structure of bacteriorhodopsin.

scholarly journals A Parallel Solution Scheme for Inverse Dynamics and its Application in Feed-forward Control of Link Mechanisms

2003 ◽  
Vol 15 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Daigoro Isobe ◽  
◽  
Daisaku Imaizumi ◽  
Youichi Chikugo ◽  
Shunsuke Sato
Keyword(s):  
Inverse Dynamics ◽  
Equations Of Motion ◽  
Open Loop ◽  
Joint Torque ◽  
Entire System ◽  
Two Dimensional ◽  
Feed Forward ◽  
Parallel Solution ◽  
Feed Forward Control ◽  
Solution Scheme

This paper describes a three-dimensional parallel solution scheme for inverse dynamics of link mechanisms, which has already been proposed for the two-dimensional case and applied in several in-plane motions. In this theory, the entire system is subdivided into finite elements and evaluated as a continuum. A single-link structure of a pin joint and a rigid bar is expressed using the Shifted Integration (SI) technique, which is conventionally used in finite element analyses of framed structures. This scheme calculates nodal forces by evaluating equations of motion in a matrix form, and thus information from the entire system can be handled in parallel, which is a very useful characteristic when applied in closed-loop or continuously transforming mechanisms. The obtained nodal forces are then converted into the joint torque in the system. Simple numerical tests on two-dimensional and threedimensional open-loop link mechanisms are carried out for comparison with other schemes. The proposed scheme is implemented in a control system to evaluate the performance in actual control with dynamics compensation, and some control experiments are carried out on an open-loop link mechanism. The results reveal the possibility of using the proposed solution scheme in feed-forward control, independently to the system configuration of link mechanisms.

Sign in / Sign up

Export Citation Format

Share Document