scholarly journals Pneumatic Servo Bearing Actuator with Multiple Bearing Pads for Ultraprecise Positioning

2013 ◽  
Vol 7 (5) ◽  
pp. 498-505 ◽  
Author(s):  
Shuhei Tsujimura ◽  
◽  
Yusuke Hashimoto ◽  
Takashi Matsuoka ◽  
Tomoko Hirayama ◽  
...  
Keyword(s):  
Research And Development ◽  
Dynamic Characteristics ◽  
Large Scale ◽  
Thrust Bearing ◽  
Open Loop ◽  
Open Loop Control ◽  
Positioning Accuracy ◽  
Loop Control ◽  
Positioning Systems ◽  
The Difference

With the increase in demand for semiconductor products, ultrafine linear patterning technologies for Large-Scale Integrations (LSIs) have been making progress. The requested positioning accuracy in such ultraprecise apparatuses is of nanometer order. To meet such specific needs, the research and development of a variety of actuators has been necessary. Our laboratory has developed a ‘Pneumatic Servo Bearing Actuator (PSBA),’ a novel actuator that uses pneumatic servo technology for ultraprecise positioning. Our past studies have showed that the minimum resolution of PSBA was almost 6 nm, even under open loop control; thus, we concluded that the PSBA was a promising actuator in advanced ultraprecise positioning systems. However, the stroke of the PSBA was comparatively short. To expand the stroke of the actuator, we proposed and developed a new PSBA with multiple thin thrust-bearing pads. The main purpose in this study is to investigate the positioning properties of the new PSBA with multiple thrust bearing pads. The obtained characteristics of the PSBA can be enumerated as follows. (1) The PSBA with multiple bearing pads achieves a longer stroke than the PSBA with a single pad. (2) The difference in the thickness of the bearing pads affects the dynamic characteristics of the actuator. (3) The minimum positioning resolution of the developed PSBA with twenty-nine bearing pads is about 2 – 4 nm with feedback control.

Assessing the Role of Vergence Changes in the Perception of Random-Dot Stereograms by Using Open-Loop Control of Vergence

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 131-131 ◽  
Author(s):  
B J Rogers ◽  
M F Bradshaw
Keyword(s):  
Open Loop ◽  
Open Loop Control ◽  
Complex Surfaces ◽  
Loop Control ◽  
Random Dot Stereograms ◽  
Disparity Range ◽  
The Difference ◽  
Random Dot Stereogram ◽  
University Of Chicago Press

The fact that the 3-D shape of surfaces depicted by random dot stereograms can take several seconds or even tens of seconds to appear has been attributed to the failure to make appropriate vergence changes [B Julesz, 1971 Foundations of Cyclopean Perception (Chicago, IL: University of Chicago Press)]. Alternatively, the long latencies could be a consequence of the processing time needed to match the disparate images. To distinguish between these possibilities we measured perceptual latencies in a situation in which vergence changes had no effect on retinal disparities. To do this, horizontal eye movements were recorded with the aid of close-fitting scleral search coils in both eyes and the difference signal used to shift horizontally the two halves of a random-dot stereogram by equal and opposite amounts. When the amount of shift was equal to the magnitude of the vergence change, changes of vergence had no effect on the pattern of disparities—open-loop vergence. Three observers were presented with a sequence of stereograms depicting both ‘simple’ surfaces (a single square lying in front of the surround) and ‘complex’ surfaces, including spirals, ‘wedding cakes’, and saddle shapes under both normal and open-loop conditions. Under open-loop conditions, the complete 3-D shape was never perceived when the disparity range of the stereogram was large (>40 min arc), demonstrating the necessity of vergence changes, but the 3-D structure of ‘complex’ surfaces did build up over a period of several seconds indicating a separate disparity processing limitation.

scholarly journals A Specific Methodology of Creep Compensation for Piezoelectric Actuators by Open-Loop Control

2013 ◽  
Vol 281 ◽  
pp. 141-145 ◽  
Author(s):  
Xuan Wang ◽  
Valérie Budinger ◽  
Yves Gourinat
Keyword(s):  
Viscoelastic Model ◽  
Piezoelectric Actuators ◽  
Open Loop ◽  
Creep Model ◽  
Relaxation Model ◽  
Open Loop Control ◽  
Loop Control ◽  
Positioning Systems ◽  
Creep Effect ◽  
Nonlinear Viscoelastic Model

Piezoelectric actuators exhibit creep behavior in open-loop operation, which may lead to unaffordable errors in high precision static positioning systems. An inversion-based compensation strategy by open-loop control is presented for reducing creep effect. The approach utilizes a nonlinear viscoelastic model to portray creep phenomenon, which consists of a linear spring, a nonlinear dashpot and a series of nonlinear Voigt elements. It is shown that for the presented creep model the step responses are very similar to the piezoelectric actuators. In order to compensate creep effect, a concept of voltage relaxation in piezoelectric actuators is proposed. And the voltage relaxation model tantamount to the inverse creep model is derived using a PID closed-loop control system. Experimental results prove that, by insertion of voltage relaxation model in open-loop operation, creep effect is attenuated markedly in piezoelectric actuators.

Open-loop control of compensation for optical propagation through a turbulent shear flow

1998 ◽  
Author(s):  
C. Truman ◽  
Lenore McMackin ◽  
Robert Pierson ◽  
Kenneth Bishop ◽  
Ellen Chen
Keyword(s):  
Shear Flow ◽  
Open Loop ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Open Loop Control ◽  
Loop Control ◽  
Optical Propagation

Precise open-loop control of MEMS deformable mirror shape

2008 ◽  
Author(s):  
Thomas Bifano ◽  
Jason Stewart ◽  
Alioune Diouf
Keyword(s):  
Open Loop ◽  
Deformable Mirror ◽  
Open Loop Control ◽  
Loop Control

Responses and Optimization of a PID-Based Speed Regulating System of the Planetary Mixer

2011 ◽  
Vol 418-420 ◽  
pp. 1865-1868
Author(s):  
Ming Jin Yang ◽  
Xi Wen Li ◽  
Zhi Gang Wang ◽  
Tie Lin Shi
Keyword(s):  
Control System ◽  
Open Loop ◽  
Open Loop Control ◽  
Efficient Operation ◽  
Loop Control ◽  
Loop Control System ◽  
Response Optimization ◽  
Close Loop Control ◽  
Close Loop Control System

The performance of speed regulating is very important to the mixing process with safe, efficient operation and high quality of production. Strategies and practices of responses and optimization of a PID-based speed regulating system of a planetary mixer were presented in this paper. Research results show that: by means of the signal constraint function presented by Simulink Response Optimization, optimization PID parameters of the 2-DOF-PID controller can be obtained, and the response of close-loop control system has quite good performance of overshoot, response time, and stability compared with an open-loop control system.

Experimental Verification of Open-loop Control for an Underwater Eel-like Robot

2002 ◽  
Vol 21 (10-11) ◽  
pp. 849-859 ◽  
Author(s):  
Kenneth A. Mcisaac ◽  
James P. Ostrowski
Keyword(s):  
Experimental Work ◽  
Experimental Verification ◽  
Vision System ◽  
Open Loop ◽  
Open Loop Control ◽  
Loop Control ◽  
Position Sensing ◽  
Theoretical Predictions ◽  
Approximate Expressions ◽  
Good Agreement

In this paper, we describe experimental work using an underwater, biomimetic, eel-like robot to verify a simplified dynamic model and open-loop control routines. We compare experimental results to previous analytically derived, but approximate expressions for proposed gaits for forward/backward swimming, circular swimming, sideways swimming and turning in place. We have developed a five-link, underwater eel-like robot, focusing on modularity, reliability and rapid prototyping, to verify our theoretical predictions. Results from open-loop experiments performed with this robot in an aquatic environment using an off-line vision system for position sensing show good agreement with theory.

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