TIME REGAINED: The complex magic of reverse motion

2007 ◽  
pp. 190-204
Keyword(s):  
2020 ◽  
Vol 46 (2) ◽  
pp. 232-237 ◽  
Author(s):  
Shunsuke Kimura ◽  
Arata Ebihara ◽  
Keiichiro Maki ◽  
Miki Nishijo ◽  
Daisuke Tokita ◽  
...  

Author(s):  
И.Е. СУРИКОВ

В качестве факторов, способствовавших нарастанию варваризации в Афинах второй полвины V в. до н.э., в статье указываются создание Афинской морской державы, движение софистов, конфликт поколений, Пелопоннесская война, наступление «эры демагогов». Обратное же движение в сторону деварваризации (с самого конца Vв. до н.э.) было связано в первую очередь с возрождением уважения к законности, с укреплением стабильности и порядка. Новая афинская демократия IV в. до н.э., которую одни специалисты считают «усовершенствованным» вариантом по сравнению с демократией предшествующего столетия, а другие, напротив, ее упадком, кризисом, была в основном свободна как от охлократических, так и от олигархических тенденций; она может с полным основанием быть определена как умеренная демократия, в отличие от радикальной демократии второй половины V в. до н.э. Конфликтов не то чтобы не было, но их старались разрешать мирным путем, по возможности достигая компромисса и избегая насилия. The article cites as factors, which promoted the growth of barbarization in Athens in the last half of the 5thcentury B.C., the following ones: the emergence of the Athenian Empire, the sophistic movement, the conflict of generations, the Peloponnesian War, and the coming of the “era of demagogues”. As to the reverse motion towards debarbarization (from the very end of the 5th century B.C.), it was connected, in the first instance, with revival of the lawfulness’ authority and with strengthening order and stability. The new Athenian democracy of the 4thcentury B.C. (which is considered by some scholars an “improved” version as compared with democracy of the previous century, but by other scholars, on the contrary, its decline and crisis) was in general free from both ochlocratic and oligarchic tendencies; it may be with good reason defined as a moderate democracy, as distinct from the radical democracy of the last half of the 5thcentury B.C. It is not to say that there were no conflicts, but people sought to solve them by peaceful way, as far as possible, to reach compromises and to avoid violence.


2019 ◽  
pp. 99-106
Author(s):  
A.A. Dobrodeev ◽  
◽  
K.E. Sazonov ◽  
I.A. Sapershteyn ◽  
◽  
...  

2019 ◽  
Vol 18 (3) ◽  
pp. 223-232
Author(s):  
A. V. Glebov ◽  
G. D. Karmaev

Results of the analysis of scientific, technical and patent literature show that while having a great variety of constructive implementation of the proposed catchers there are no efficient and sufficiently reliable devices for catching conveyor belts at its reverse motion which are relatively simple in design. This is proved by practical activity of enterprises involved in extraction and processing of commercial minerals and other industries. A new design of a conveyor belt catcher that meets most requirements for the given equipment has been developed at the Institute of Mining, Ural of Branch of the Russian Academy of Sciences and then it has been tested under industrial conditions. The design makes provision for retention of the conveyor belt at its reverse motion beyond free edges from transported material. Catching devices are installed on both sides of the belt. Braking action of the belt at the reverse motion occurs due to its friction interaction with a catcher friction shoe located above the belt, and an eccentric mounted on the frame under the belt. A friction shoe is made with a concave curved surface facing the belt. The paper presents a calculation methodology of main parameters for the proposed design of catcher conveyor belts that permits to determine a force catching a conveyor belt down and for every braking period distance which has been passed by the belt, value of its compression, value of braking force, braking time and acceleration of belt motion, time and length of the distance passed by the belt to its full stop, parameters of a catcher and supporting structures, and other parameters. The paper also provides results of calculations for main design parameters of catching devices with an inclined conveyor having a belt width of 1400 mm for two catcher design versions: with location of an eccentric under the belt, and a brake shoe over the belt (option I) and with location of the eccentric over the conveyor belt, and the brake friction shoe under the belt (option II).


2019 ◽  
Vol 13 (5) ◽  
pp. 610-618
Author(s):  
Akio Hayashi ◽  
◽  
Tatsuya Mukai ◽  
Yusuke Inomata ◽  
Yoshitaka Morimoto

Lost motion is a phenomenon that often occurs during the motion of a moving table, which is used for machine tools to ensure their precise positioning. Lost motion occurs when the direction of the table’s motion reverses as a result of nonlinear friction characteristics between the feed drive mechanisms such as the ball screw and linear guide. Lost motion directly influences the machining accuracy of a machine tool, because the accuracy of machining depends on the relative motion between the tool and the workpiece. A number of studies have dealt with suppressing the occurrence of lost motion using model-based control. However, nonlinear friction has not been addressed to the same extent, as it is difficult to determine the motion characteristics of and therefore develop a model for the nonlinear friction. Thus, to address these problems, we propose a compensation method for revers motion based on vector control, which is used to control the torque and velocity of the alternating current (AC) servomotor in the moving table. In this study, the current applied to the AC servomotor for a vector with force components in the rotational direction (torque component) and in the direction perpendicular to the axis of rotation (field component) was measured to clarify and establish the relationship between the motion and the control current. The compensation current was then derived as a functional value based on the results of the measured torque at the occurrence of lost motion. Further, tests were carried out using the proposed method, which directly applies the drive current of the AC servomotor by using a field-programmable gate array controller to improve the reverse motion of the table. The results reveal that the motion characteristics of a numerical control (NC) table can be determined by measuring the drive current of the AC servomotor. In addition, it is verified that the proposed method can compensate for the torque command smoothly at the time of velocity reversal, resulting in suppression of the lost motion and reduction of reverse motion of the moving table.


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