Use Of Electrorheological Fluids Research Articles

Development of Novel Hydraulic 3D Printed Actuator Using Electrorheological Fluid for Robotic Endoscopy

Endoscopy has made a significant and noteworthy contribution to the field of medical science and technology. Nevertheless, its potential remains constrained due to the limited availability of rigid or flexible endoscopes. This paper introduces a novel hydraulic actuator based on electrorheological fluid (ERF) as a pivotal advancement in bridging the existing gap within the realm of endoscopy. Following a comprehensive introduction that briefly outlines the electrorheological effect, the subsequent section is dedicated to the elucidation of the actuator’s development process. Challenges arise, particularly in terms of miniaturization and the realization of a hydraulically sealed system with integrated valve electrodes. An internal electrorheological valve system consisting of four valves that are controlled using a pulse-width modulated high voltage was suitable for position control of the antagonistic hydraulic actuators. High-precision stereolithography (SLA) printing has proven practical for manufacturing actuator components. For functional testing, a test bench was set up in which the actuator follows a setpoint through a PI control loop. The control deviation ranged from 0.6 to 1 degree, with a response time between 6 and 8 s. The experiments have demonstrated that through the use of ERF and integrated valve electrodes, a miniaturized functional actuator can be constructed.

Semi-active vibration control of high-speed rotor system with electrorheological bearing fluid

Present work focuses on the use of electrorheological fluid (ERF) as a lubricant in the high speed turbocharger rotor supported on floating ring bearings. The rotor is analysed by finite element modelling with gyroscopic effects and bearing forces. The ERF contains one carrier fluid and active particles that react to external electric field, which induces a yield stress in the fluid increasing its viscosity. In order to control the rotor vibration amplitudes, the dynamic changes in the fluid viscosities at the inner and outer films of bearing are employed with external electric field. A case study of automotive turbocharger rotor is considered and the effect of semi-active control is illustrated on the dynamic response of the system.

Evaluation of Electrorheological Fluid Dampers for Applications at 3-T MRI Environment

This paper evaluates the use of electrorheological fluids (ERFs) within a magnetic resonance imaging (MRI) environment. ERF is a semiactive variable impedance material, which could be used as an alternative type of resistive force/torque generation or in combination with other actuators as a damper/clutch to modulate the output force/torque of the actuator. In this paper, an ERF damper/brake is introduced and its magnetic resonance (MR) compatibility is examined at a 3-T MR imaging environment by measuring the output performance of the damper and the SNR of the MRI images. The experimental results showed that damper's resistive force generation while positioned within the MRI is almost the same as that in normal operation. The signal-to-noise investigation was performed both with a phantom and human. The results indicated that the ERF damper did not affect the MRI images when it was operated over 30 cm away from the MRI's RF coil. We hope that the synthesis and tables presented in this paper can facilitate the choice of ERF brake actuation principle to various applications in an MR environment.

MR_CHIROD v.2: Magnetic Resonance Compatible Smart Hand Rehabilitation Device for Brain Imaging

This paper presents the design, fabrication, and testing of a novel, one degree-of-freedom, magnetic resonance compatible smart hand interfaced rehabilitation device (MR_CHIROD v.2), which may be used in brain magnetic resonance (MR) imaging during handgrip rehabilitation. A key feature of the device is the use of electrorheological fluids (ERFs) to achieve computer controlled, variable, and tunable resistive force generation. The device consists of three major subsystems: 1) an ERF based resistive element, 2) handles, and c) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. MR_CHIROD v.2 is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. Our results demonstrate that the MR environment does not interfere with the performance of the MR_CHIROD v.2, and, reciprocally, its use does not cause fMR image artifacts. The results are encouraging in jointly using MR_CHIROD v.2 and brain MR imaging to study motor performance and assess rehabilitation after neurological injuries such as stroke.

FMRI-compatible rehabilitation hand device.

BackgroundFunctional magnetic resonance imaging (fMRI) has been widely used in studying human brain functions and neurorehabilitation. In order to develop complex and well-controlled fMRI paradigms, interfaces that can precisely control and measure output force and kinematics of the movements in human subjects are needed. Optimized state-of-the-art fMRI methods, combined with magnetic resonance (MR) compatible robotic devices for rehabilitation, can assist therapists to quantify, monitor, and improve physical rehabilitation. To achieve this goal, robotic or mechatronic devices with actuators and sensors need to be introduced into an MR environment. The common standard mechanical parts can not be used in MR environment and MR compatibility has been a tough hurdle for device developers.MethodsThis paper presents the design, fabrication and preliminary testing of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that may be used in brain MR imaging during hand grip rehabilitation. We named the device MR_CHIROD (Magnetic Resonance Compatible Smart Hand Interfaced Rehabilitation Device). A novel feature of the device is the use of Electro-Rheological Fluids (ERFs) to achieve tunable and controllable resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. The device consists of four major subsystems: a) an ERF based resistive element; b) a gearbox; c) two handles and d) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. The smart hand device is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time.ResultsLaboratory tests of the device indicate that it was able to meet its design objective to resist up to approximately 50% of the maximum handgrip force. The detailed compatibility tests demonstrated that there is neither an effect from the MR environment on the ERF properties and performance of the sensors, nor significant degradation on MR images by the introduction of the MR_CHIROD in the MR scanner.ConclusionThe MR compatible hand device was built to aid in the study of brain function during generation of controllable and tunable force during handgrip exercising. The device was shown to be MR compatible. To the best of our knowledge, this is the first system that utilizes ERF in MR environment.

Design Concept for the Development of Cylinder Drives based on Electrorheological Fluids

This article deals with the practical use of electrorheological fluids (ERFs). At the Institute for Fluid Power Drives and Control (IFAS), a test rig has already been in use for several years and different applications have been investigated with it. During these investigations, information about the various influences on the ER effect, in terms of yield stress and current density, could be gathered. Due to the improvement of the ERF itself and the associated components, it is now possible to build up cylinder drives with improved forces and dynamic behavior. Nevertheless, there is still a lack of design rules and design aids for applications based on ERFs till today. After introducing some of the applications developed at IFAS, this article presents the latest measurements of valves based on ERFs. Knowing the influence of geometric parameters on the ER effect, a mathematical model has been adapted to the fluid used in recent measurements. It is also shown that a modular design of the cylinder drives makes the setup of the simulation model possible and enables the application engineer to carry out an accurate measurement.

Use of electro-rheological fluids in a damping device

This paper presents results of experimental studies of an electro-rheological shock absorber based on a controlled hydrosuspension designed to damp a wheeled tractor driver’s cab accommodating not only the operator but also complex electronic equipment by regulating the rheological characteristics of the working fluid by means of an external electric field. The characteristics and dependences of the operating conditions of the electro-rheological shock absorber are presented. The dissipative processes have been estimated.

Basic performance of ER gel on one-sided structured electrodes

An electro-rheological Gel (ERG) is developed to overcome two shortcomings of Electro-rheological Fluid (ERF): sedimentation of ER particles and the seal structure required to allow the use of ERF in machine elements. The ERG shows a wide shear stress variation in response to an applied electric field. To apply an electric field to the ERG, it is necessary to sandwich the ERG between plane-parallel electrodes. However, it is impractical to wire both electrodes to a high voltage supply. In this study, one-sided electrodes are proposed to simplify the wiring structure. The basic characteristics of ERG on one-sided electrodes are evaluated experimentally. It is found that these electrodes exhibit nearly the same performance as the conventional plane-parallel type. The one-sided ERG mechanism is especially useful in applications involving rotating or sliding parts.

Design and Control Considerations for a High-Speed Electro-Rheological Traversing Mechanism

A high-speed traversing mechanism using two electro-rheological clutches is described. An application of the traversing mechanism is in winding textile filaments onto spinning or weaving bobbins. The design specifications are a traverse speed of 5m/s; a turn round period of 10-20 ms and a traverse length of 250 mm. The turn round position must be controllable and repeatable within ± 1 mm and the traverse length requires to be periodically varied in order to shape the ends of the resulting bobbin. These combined criteria of high speed and controllability makes the use of electro-rheological fluids an attractive proposition. The paper considers the effects of the main geometric and fluid parameters on the performance of the mechanism and uses this to outline the limiting performance of the mechanism, together with the effects on the precision of the mechanism. The paper also outlines control aspects of the mechanism and uses this to indicate important areas for consideration in the future development of electro-rheological fluids.

Electro-rheological effects of liquid crystalline polymer on one-sided pattern electrodes

In most industrial robots, serious problems of vibratory behavior are caused because of elasticity in the drive systems. An electro-rheological (ER) fluid is a substance that can change its apparent viscosity by the application of an electric field, and homogeneous ER fluids are effective in reducing vibration in robots. Conventional research into ER fluids is based on parallel electrodes with ER fluids between them. Since a high voltage is required for use of ER fluids with parallel electrodes, problems of cost, safety and wiring for practical applications are of concern. In this article, we propose one-sided pattern electrodes that solve some of the above problems. A one-sided pattern electrode is an electrode in a pattern arranged on only one of the two surfaces of a pair of electrodes, with an insulator arranged on the other surface. We developed two kinds of one-sided pattern electrodes: a concentric circle form and a radial form, experimentally verifying the manifestation of ER effects in a liquid crystalline polymer (a homogeneous ER fluid). In addition, the effect of disk gap upon viscosity change was investigated.

Dynamic simulation and performance of an electro-rheological clutch based reciprocating mechanism

A reciprocating mechanism which utilizes two electro-rheological clutches is described. An industrial application of the mechanism is in winding filaments onto bobbins. The required traverse speed is 5 m s-1 with a turn-round period of 10-20 ms, the traverse length is 250 mm and the turn-round position must be electronically controllable and repeatable within the ±1 mm. These combined criteria of high-speed and controllability makes the use of electro-rheological fluids an attractive proposition. The operation of the reciprocating mechanism and the dynamic model used to simulate the performance are outlined. The simulation is verified by comparison with experimental results from a prototype mechanism. Simulations are made to illustrate the effect of various fundamental electro-rheological fluid characteristics, such as electro-shear stress, time delays and viscosity. These simulations are considered in relation to the requirements for the operation of the high-speed mechanism.

The electrorheological effect under compressive stress

Despite the greatly superior performance in terms of hardness modulus change, the use of electrorheological fluids under compressive stress has been largely neglected in favour of implementations relying on shear-stress effects alone. This paper shows how electrorheological fluids, in addition to Bingham plasticity, also exhibit what appears to be rheopectic behaviour when subjected to compressive stress.