scholarly journals Kinematic synthesis method and eccentricity effects of a Stephenson mechanism

2021 ◽  
Vol 12 (1) ◽  
pp. 1-8
Author(s):  
Amandyk Tuleshov ◽  
Recep Halicioglu ◽  
Azhar Shadymanova ◽  
Moldir Kuatova
Keyword(s):  
Rotation Axis ◽  
Synthesis Method ◽  
Manufacturing Cost ◽  
Mean Square ◽  
Kinematic Synthesis ◽  
Bottom Dead Center ◽  
Working Cycle ◽  
Angular Coordinates ◽  
Slider Motion ◽  
Crank Length

Abstract. When implementing the technological process on crank presses, it is necessary to provide a predetermined working cycle of the slider motion: fast lifting, dwell, and slow lowering. The cycle cannot be realized without controlling the motor. In addition, using controllable motors increases the manufacturing cost. Due to the geometric and kinematic capabilities of the mechanism, changing the kinematics of the working link is the best choice. Thanks to the use of the Stephenson II mechanism, the slider skew is eliminated due to the parallel connecting rods and the increased area of slider contact. This study presents a numerical method for kinematic synthesis of the Stephenson mechanism that has kinematic advantages. The method is based on mean square deviation which is the minimizing of an objective function. Thanks to the proposed synthesis method, approximate dwell movement can be performed when the slider is on the bottom dead center. In this study, values of the crank length and parallel connecting rods' lengths, angular coordinates of the crank and connecting rods, and the eccentricity of the guide slider relative to the crank rotation axis were obtained. It is observed that eccentricity affects the lower forward and higher backward speed of the slider. The kinematic results of the slider movement are comparatively presented in this article.

Kinematic synthesis method for the one-degree-of-freedom jumping leg mechanism of a locust-inspired robot

2019 ◽  
Vol 63 (3) ◽  
pp. 472-487 ◽  
Author(s):  
ZiQiang Zhang ◽  
Qi Yang ◽  
Jing Zhao ◽  
Bin Chang ◽  
XingKun Liu
Keyword(s):  
Synthesis Method ◽  
Degree Of Freedom ◽  
Kinematic Synthesis ◽  
The One

Application of a Customized Optical Force Sensor to a Cable-Driven Leg Exoskeleton

2021 ◽  
Author(s):  
Jiaxu Huang ◽  
Rand Hidayah ◽  
Sunil Agrawal ◽  
Jorge A. Diez ◽  
Nicolas García-Aracil
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Force Sensor ◽  
Optical Force ◽  
Robotic Systems ◽  
Sensor Calibration ◽  
Manufacturing Cost ◽  
Mean Square ◽  
Validation Tests ◽  
Force Profiles

Abstract In this paper, a customized optical force sensor is developed for an application with a cable-driven leg exoskeleton. Sensors are vital components of cable-driven, exoskeletal robotic systems, which require real-time and accurate measurement of cable tensions. While these systems’ accuracy is a consideration, the added weight, volume, and complexity of the system must is an essential part of widespread adoption for wearable applications. These sensors can also be costly, which is undesirable. An optical force sensor has the advantages of being lightweight, lower in manufacturing cost, and easy to incorporate within the exoskeleton architecture. We designed a sensor to accommodate the expected force profiles and magnitudes during gait while wearing the Cable-Driven Active Leg Exoskeleton (C-ALEX) during a walking task. We carried out four different calibration tests with dynamic loading of the sensors from 10N to 40N. Once a sensor calibration was established, the optical sensor’s performance was compared to a traditional load cell in validation tests. Both components were used in an assist-as-needed force controller in a walking task with a user, with the optical force sensor incorporated into the C-ALEX exoskeleton arms. Comparing the sensor responses to the command tension forces, the results show a root-mean-square error (RMSE) of 0.9595N ± 0.5360N.

The Sun as a Magnetic Star

1976 ◽  
Vol 32 ◽  
pp. 457-463
Author(s):  
John M. Wilcox ◽  
Leif Svalgaard
Keyword(s):  
Recent Work ◽  
Rotation Axis ◽  
Polar Field ◽  
Magnetic Star ◽  
Rotational Axis ◽  
Field Variation ◽  
The Sun ◽  
Arbitrary Angle ◽  
Solar Magnetism ◽  
Oblique Rotator

SummaryThe sun as a magnetic star is described on the basis of recent work on solar magnetism. Observations at an arbitrary angle to the rotation axis would show a 22-year polar field variation and a 25-day equatorial sector variation. The sector variation would be similar to an oblique rotator with an angle of 90° between the magnetic and rotational axis.

The Bordeaux Automatic Meridian Circle

1978 ◽  
Vol 48 ◽  
pp. 227-228
Author(s):  
Y. Requième
Keyword(s):  
Mean Square Error ◽  
Mean Square ◽  
Meridian Circle ◽  
The Mean ◽  
Full Automation

In spite of important delays in the initial planning, the full automation of the Bordeaux meridian circle is progressing well and will be ready for regular observations by the middle of the next year. It is expected that the mean square error for one observation will be about ±0.”10 in the two coordinates for declinations up to 87°.

Σ =13 tilt grain boundary in silicon bicrystal

1990 ◽  
Vol 48 (4) ◽  
pp. 562-563
Author(s):  
M.J. Kim ◽  
Y.L. Chen ◽  
R.W. Carpenter ◽  
J.C. Barry ◽  
G.H. Schwuttke
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rotation Axis ◽  
Czochralski Method ◽  
High Resolution Electron Microscopy ◽  
Image Simulation ◽  
Simulation Techniques ◽  
Resolution Electron ◽  
The Common ◽  
Tilt Grain Boundary

The structure of grain boundaries (GBs) in metals, semiconductors and ceramics is of considerable interest because of their influence on physical properties. Progress in understanding the structure of grain boundaries at the atomic level has been made by high resolution electron microscopy (HREM) . In the present study, a Σ=13, (510) <001>-tilt grain boundary in silicon was characterized by HREM in conjunction with digital image processing and computer image simulation techniques.The bicrystals were grown from the melt by the Czochralski method, using preoriented seeds. Specimens for TEM observations were cut from the bicrystals perpendicular to the common rotation axis of pure tilt grain boundary, and were mechanically dimpled and then ion-milled to electron transparency. The degree of misorientation between the common <001> axis of the bicrystal was measured by CBED in a Philips EM 400ST/FEG: it was found to be less than 1 mrad. HREM was performed at 200 kV in an ISI-002B and at 400 kv in a JEM-4000EX.

Indikatoren schulischen Wohlbefindens bei gesunden und chronisch kranken Kindern: Psychometrische Prüfung und Validierung adaptierter FEESS-Skalen

2020 ◽  
Vol 34 (3-4) ◽  
pp. 201-219
Author(s):  
Kathleen Schnick-Vollmer ◽  
Christiane Diefenbach ◽  
Christine Gräf ◽  
Dorle Hoffmann ◽  
Isabell Hoffmann ◽  
...  
Keyword(s):  
Item Response ◽  
Mean Square ◽  
Weighted Mean ◽  
Externe Validität ◽  
Chronisch Kranke

Zusammenfassung. Das schulbezogene Wohlbefinden (SBWB) ist eine wichtige Voraussetzung für schulischen Erfolg. Trotzdem existieren – insbesondere mit Blick auf die Erfassung des SBWB von Erstklässlern – im deutschsprachigen Raum nur vereinzelt Studien. Dies lässt sich möglicherweise durch das Fehlen geeigneter Instrumente begründen. Dies gilt auch und insbesondere dann, wenn der Gesundheitszustand der Kinder berücksichtigt werden soll. Das Ziel der vorliegenden Arbeit besteht in der Validierung des adaptierten Fragebogens zur Erfassung von emotionalen und sozialen Schulerfahrungen (FEESS 1 – 2; Rauer & Schuck, 2004 ) mit Fokus auf die Eignung des Instruments für chronisch kranke und gesunde Kinder. Dafür wird zunächst das Konstrukt Wohlbefinden (WB) resp. SBWB definiert und in einschlägige Theorien – die Selbstbestimmungstheorie nach Deci und Ryan (1985) und das Erwartung-mal-Wert-Modell nach Wigfield und Eccles (2000) – eingebettet. Die Bedeutung der verwendeten FEESS-Skalen und ihr Zusammenhang zum schulischen Erfolg werden aufgezeigt. 1491 Kinder wurden zu ihrer Lernfreude (LF), sozialen Integration (SI) und zu ihrem schulbezogenen Fähigkeitsselbstkonzept (SK) befragt. Die Erfassung des Gesundheitszustands wurde über Elternfragebögen und Schuleingangsuntersuchungen eruiert. Zudem wurden die Eltern zur gesundheitsbezogenen Lebensqualität (LQ) ihrer Kinder mit Hilfe eines Fragebogens zur Erfassung der Lebensqualität von Kindern (KINDL; Bullinger, Mackensen & Kirchberger, 1994 ) befragt. Die psychometrische Qualität der adaptierten FEESS-Skalen wurde für beide Gruppen (erkrankt / gesund) auf Skalen- und Itemebene untersucht. Hierzu kamen sowohl klassische Verfahren als auch Verfahren der Item-Response-Theorie zum Einsatz. Die Ergebnisse untermauern die Validität des Konstruktes SBWB und stützen die Annahme der Dreidimensionalität (LF, SI, SK). Alle drei Skalen zeigen eine zufriedenstellende bis sehr gute Reliabilität. Die Items zeigen sehr gute MNSQ-Werte (weighted mean-square; gewichtete Abweichungsquadrate) und geeignete Trennschärfen. Die externe Validität, für deren Berechnung der Zusammenhang zwischen den Angaben der Kinder und den Angaben der Eltern zur gesundheitsbezogenen LQ untersucht wurde, konnte noch nicht ausreichend nachgewiesen werden. Bis auf diese Einschränkung kann mit Hilfe der adaptierten FEESS-Skalen im nächsten Schritt das SBWB von gesunden und erkrankten Kindern verglichen werden, um mögliche Chancenungleichheiten auszugleichen.

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