rus
Issue #2/2022
D.S.Shakhov, V.P.Mikhailov, A.M.Bazinenkov, M.E.Zhukov
VACUUM TWO-AXIS MOVEMENT MECHANISM WITH ELECTRORHEOLOGICAL SPEED CONTROL
VACUUM TWO-AXIS MOVEMENT MECHANISM WITH ELECTRORHEOLOGICAL SPEED CONTROL
DOI: https://doi.org/10.22184/1993-8578.2022.15.2.144.148
In many areas of modern nanotechnologies carried out in a vacuum it is required to move objects with high precision. The paper considers a two-axis vacuum pneumohydraulic drive capable of performing precise movements. High precision of the mechanism is achieved due to use of intelligent material as a working fluid of the hydraulic part – an electrorheological fluid that can instantly change its rheological properties under the action of an external electric field. It has been experimentally established in the work that the most effective adjustment of the speed of the drive rod movement is carried out at low pressures in the pneumatic cylinder with a 25%concentration of the dispersed phase of the working fluid.
In many areas of modern nanotechnologies carried out in a vacuum it is required to move objects with high precision. The paper considers a two-axis vacuum pneumohydraulic drive capable of performing precise movements. High precision of the mechanism is achieved due to use of intelligent material as a working fluid of the hydraulic part – an electrorheological fluid that can instantly change its rheological properties under the action of an external electric field. It has been experimentally established in the work that the most effective adjustment of the speed of the drive rod movement is carried out at low pressures in the pneumatic cylinder with a 25%concentration of the dispersed phase of the working fluid.
Теги: electrorheological fluid pneumohydraulic drive speed adjustment vacuum viscosity вакуум вязкость пневмогидравлический привод регулировка скорости перемещения электрореологическая жидкость
INTRODUCTION
The predominant part of modern nanotechnology takes place in a vacuum process environment. For example, thin films deposited in a vacuum are used as antifriction coatings for cutting tools and mechanical friction couples. In order to ensure evenness of the applied films, it is often necessary to perform a movement with high positioning accuracy and constant speed. The most efficient speed control is achieved by pneumatic and hydraulic drives. In order to improve accuracy of hydraulic drive movements, a smart material, electro-rheological fluid (ERF), can be used as a working fluid [4, 5]. ERF are suspensions of polarizing material particles distributed in a dielectric fluid. In the absence of an electric field, ERFs behave like most conventional suspensions, exhibiting Newtonian flow properties. However, when an electric field is applied to them, there is an almost instantaneous (up to 100000) increase in viscosity due to formation of the chain structures oriented parallel to the electric field lines. In addition to viscosity, elasticity and plasticity of the liquid will change.
There are numerous studies worldwide related to electro-rheological fluids. Works on ERF research are mainly focused on selection of disperse phase which will provide maximum electrorheological effect of the suspension. The use of barium titanate as the disperse phase allows of obtaining a shear strain of 400 Pa at electric field strength of 800 V/mm [1]. If lithium salts of polystyrene-block copolymer-polyisoprene are used as the suspension solid phase, a shear stress of 50 Pa at 560 V/mm can be achieved [2]. If cerium dioxide is used as the filler, a shear stress of 4,000 Pa at 3000 V/mm can be achieved [3].
Starch can be used as a cheaper analogue for the solid phase of the ERF.
The vacuum two-axis displacement mechanism with electro-rheological speed control (Fig.1) functions as follows.
Carriage 4 is driven by pneumatic cylinder 1 connected to hydraulic cylinder 2 by a common rod. Movement input 6 ensures sealing of the rod in the vacuum chamber. The rod is rigidly fixed to carriage 4 moving along the guides inside vacuum chamber 5. The movement speed is controlled with the aid of a transductor and electro-rheological throttle (ERT) 3 in hydraulic cylinder 2.
RESEARCH METHODS
This study was carried out on a ER controlled single-axis pneumohydraulic drive (Fig.2) which simulates a vacuum two-coordinate movement mechanism with electro-rheological speed control.
The drive is combined and consists of pneumatic cylinder 2 and hydraulic cylinder 7, which have common rod 8 that performs reciprocating motion. The working fluid in the hydraulic cylinder is ERF. As the actuator rod moves, the ERF flows from one cavity of the hydraulic cylinder to the other through the gap in controlled throttle 5. Due to the ER effect, the volume flow of the ERF through the restrictor is reduced and, consequently, the rod is slowed down.
The aim of the experiment to study the rheological characteristics of starch-based ERF was to determine efficiency of the pneumohydraulic drive rod speed control.
At different pressures in the pneumatic cylinder and different stresses on the throttle shells the rod position and pressure difference were measured.
In this work the studied samples with concentration of disperse phase starch 15, 25, 40% are presented. The dispersion environment was an organosilicon fluid PMC-20. In this case water was used as the activator.
RESULTS
The resulting coordinate values were converted to a rod movement speed. As a result of experimental data processing the dependences of the piston rod speed on the pressure on ERТ covers were received for ERF samples with concentration of disperse phase starch of about 15, 25 and 40%. These diagrams of pressure for pneumatic cylinder at 0.4 atm and 0.5 atm are shown on Figs.3, 4, respectively.
It was found that as the voltage on the ERF shells increases, the rod speed decreases. For pressure of 0.4 atm and concentration of the dispersed phase 25 % the change of speed is most pronounced but for concentrations 15 and 40% the change of speed is not essential. At pressure in pneumatic cylinder of 0.5 atm the steady decrease of speed was recorded for all samples.
DISCUSSIONS
The change in speed is due to the electrorheological effect occurring in the ERT working gap. The chain structures formation between the throttle shells provides a local increase in the equivalent viscosity of fluid in the gap, resulting in a reduction in the working fluid flow rate and reduction of the rod speed.
At high pressures of 0.5 atm, the fluid flow rate is relatively high, resulting in low efficiency of rod speed control. The chain structures do not have time to form and are quickly washed out by intensive liquid flow.
The most efficient control of the rod speed was observed at low pressure of 0.4 atm. Simultaneously, the rod speed is reduced by 75% as the voltage increases to 2 kV.
CONCLUSIONS
It has been found that by using the hydraulic part of the ERF drive as a working fluid, the speed of the vacuum double-coordinate movement mechanism can be effectively controlled by influencing the electro-rheological fluid by electric field.
The vacuum drive speed rod movement can be controlled most effectively at a low pressure of 0.4 atm in the pneumatic drive cylinder.
The drive rod speed varies from 12 to 3 mm/s with the increase of control voltage on ERT shells from 0 to 2,000 V when using ERF with disperse phase concentration of 25 %.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The predominant part of modern nanotechnology takes place in a vacuum process environment. For example, thin films deposited in a vacuum are used as antifriction coatings for cutting tools and mechanical friction couples. In order to ensure evenness of the applied films, it is often necessary to perform a movement with high positioning accuracy and constant speed. The most efficient speed control is achieved by pneumatic and hydraulic drives. In order to improve accuracy of hydraulic drive movements, a smart material, electro-rheological fluid (ERF), can be used as a working fluid [4, 5]. ERF are suspensions of polarizing material particles distributed in a dielectric fluid. In the absence of an electric field, ERFs behave like most conventional suspensions, exhibiting Newtonian flow properties. However, when an electric field is applied to them, there is an almost instantaneous (up to 100000) increase in viscosity due to formation of the chain structures oriented parallel to the electric field lines. In addition to viscosity, elasticity and plasticity of the liquid will change.
There are numerous studies worldwide related to electro-rheological fluids. Works on ERF research are mainly focused on selection of disperse phase which will provide maximum electrorheological effect of the suspension. The use of barium titanate as the disperse phase allows of obtaining a shear strain of 400 Pa at electric field strength of 800 V/mm [1]. If lithium salts of polystyrene-block copolymer-polyisoprene are used as the suspension solid phase, a shear stress of 50 Pa at 560 V/mm can be achieved [2]. If cerium dioxide is used as the filler, a shear stress of 4,000 Pa at 3000 V/mm can be achieved [3].
Starch can be used as a cheaper analogue for the solid phase of the ERF.
The vacuum two-axis displacement mechanism with electro-rheological speed control (Fig.1) functions as follows.
Carriage 4 is driven by pneumatic cylinder 1 connected to hydraulic cylinder 2 by a common rod. Movement input 6 ensures sealing of the rod in the vacuum chamber. The rod is rigidly fixed to carriage 4 moving along the guides inside vacuum chamber 5. The movement speed is controlled with the aid of a transductor and electro-rheological throttle (ERT) 3 in hydraulic cylinder 2.
RESEARCH METHODS
This study was carried out on a ER controlled single-axis pneumohydraulic drive (Fig.2) which simulates a vacuum two-coordinate movement mechanism with electro-rheological speed control.
The drive is combined and consists of pneumatic cylinder 2 and hydraulic cylinder 7, which have common rod 8 that performs reciprocating motion. The working fluid in the hydraulic cylinder is ERF. As the actuator rod moves, the ERF flows from one cavity of the hydraulic cylinder to the other through the gap in controlled throttle 5. Due to the ER effect, the volume flow of the ERF through the restrictor is reduced and, consequently, the rod is slowed down.
The aim of the experiment to study the rheological characteristics of starch-based ERF was to determine efficiency of the pneumohydraulic drive rod speed control.
At different pressures in the pneumatic cylinder and different stresses on the throttle shells the rod position and pressure difference were measured.
In this work the studied samples with concentration of disperse phase starch 15, 25, 40% are presented. The dispersion environment was an organosilicon fluid PMC-20. In this case water was used as the activator.
RESULTS
The resulting coordinate values were converted to a rod movement speed. As a result of experimental data processing the dependences of the piston rod speed on the pressure on ERТ covers were received for ERF samples with concentration of disperse phase starch of about 15, 25 and 40%. These diagrams of pressure for pneumatic cylinder at 0.4 atm and 0.5 atm are shown on Figs.3, 4, respectively.
It was found that as the voltage on the ERF shells increases, the rod speed decreases. For pressure of 0.4 atm and concentration of the dispersed phase 25 % the change of speed is most pronounced but for concentrations 15 and 40% the change of speed is not essential. At pressure in pneumatic cylinder of 0.5 atm the steady decrease of speed was recorded for all samples.
DISCUSSIONS
The change in speed is due to the electrorheological effect occurring in the ERT working gap. The chain structures formation between the throttle shells provides a local increase in the equivalent viscosity of fluid in the gap, resulting in a reduction in the working fluid flow rate and reduction of the rod speed.
At high pressures of 0.5 atm, the fluid flow rate is relatively high, resulting in low efficiency of rod speed control. The chain structures do not have time to form and are quickly washed out by intensive liquid flow.
The most efficient control of the rod speed was observed at low pressure of 0.4 atm. Simultaneously, the rod speed is reduced by 75% as the voltage increases to 2 kV.
CONCLUSIONS
It has been found that by using the hydraulic part of the ERF drive as a working fluid, the speed of the vacuum double-coordinate movement mechanism can be effectively controlled by influencing the electro-rheological fluid by electric field.
The vacuum drive speed rod movement can be controlled most effectively at a low pressure of 0.4 atm in the pneumatic drive cylinder.
The drive rod speed varies from 12 to 3 mm/s with the increase of control voltage on ERT shells from 0 to 2,000 V when using ERF with disperse phase concentration of 25 %.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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