Magnetorheological Fluid Actuators Research Articles

Development and Evaluation of a Backdrivable Vane-Type Rotary Actuator Using Magnetorheological Fluids

Robot systems with both “intrinsic safety” and “high output” are expected to be implemented in heavy-duty industries such asconstruction and manufacturing. But there are currently no effective solutions. In our previous work, a backdrivable piston using magnetorheological fluid (MRF) whose viscosity can vary with the applied magnetic field was developed. However, it was a passive device, and its active control scheme was not proposed. The design was complex enough to hinder its implementation to robot arms. In this article, we develop an easily implementable rotary actuator using MRF and propose a basic controller. The actuator was designed based on a vane motor and was driven by hydraulic oil (i.e., MRF), so it can generate high torque. It also has a built-in MRF valve in the vane which can change the output torque and backdrivability with the magnetic field controlled by coil current. Each component was designed to maximize the dynamic range of output torque and backdrivability based on a multiphysics coupling model of electromagnetics, MRF magnetization, and fluid dynamics. Moreover, three basic control modes including backdrivable, high-response, and power-efficiency modes were designed and tested. The experimental results showed that the proposed MRF actuator had both high output and intrinsic backdrivability, and control modes could show the advantages of the MRF actuator.

Applications of Magnetorheological Fluid Actuator to Multi-DOF Systems: State-of-the-Art from 2015 to 2021

This review article presents various multi-DOF application systems that utilize smart magnetorheological (MR) fluid. It is well known that MR fluid has been actively studied and applied in many practical systems such as vehicle suspension dampers. The design requirements for the effective applications of MR fluid include geometry optimization, working principles, and control schemes. The geometry optimization is mostly related to the size minimization with high damping force, while the working principles are classified into the shear mode, the flow mode, and the squeeze mode depending on the dominant dynamic motion of the application system. The control schemes are crucial to achieve final targets such as robust vibration control against disturbances. It should be addressed that advanced output performances of MR application systems heavily depends on these three requirements. This review article presents numerous application systems such as sandwich structures, dampers, mounts, brakes, and clutches, which have been developed considering the three design requirements. In addition, in this article some merits and demerits of each application system are discussed to enable potential researchers to develop more effective and practical MR application systems featuring the multi-DOF dynamic motions.

Design and control of 2-DoF joystick using MR-fluid rotary actuator

The purpose of this paper is to design a control algorithm for a 2-DoF rotary joystick model. Firstly, the structure of the joystick, which composes of two magneto-rheological fluid actuators (shorten MRFA) with optimal configuration coupled perpendicularly by the gimbal mechanism to generate the friction torque for each independent rotary movement, is introduced. The control strategy of the designed joystick is then suggested. Really, because of two independent rotary movements, it is necessary to design two corresponding controllers. Due to hysteresis and nonlinear dynamic characteristics of the MRFA, controllers based an accurate dynamic model are difficult to realize. Hence, to release this issue, the proposed controller (named self-turning fuzzy controllers-STFC) will be built through the fuzzy logic algorithm in which the parameters of controllers are learned and trained online by Levenberg-Marquardt training algorithm. Finally, an experimental apparatus will be constructed to assess the effectiveness of the force feedback controls. Herein, three experimental cases are performed to compare the control performance of open-loop and close-loop control method, where the former is done through relationship between the force at the knob and the current supplied to coil while the latter is realized based on the proposed controller and PID controller. The experimental results provide strongly the ability of the proposed controller, meaning that the STFC is robust and tracks well the desirable force with high accuracy compared with both the PID controller and the open-loop control method.

Twin-driven actuator with multi-layered disc magnetorheological fluid clutches for haptics

Magnetorheological fluids are composite materials made of ferromagnetic particles, medium oils, and several types of additives. We have developed actuation systems for the fine haptic control of master–slave robots. In this study, we proposed a new structure of a magnetorheological fluid–based actuator suitable for haptic devices. For the basic structure of the actuator, we proposed a twin-driven magnetorheological fluid actuator using two multi-layered disc-type magnetorheological fluid clutches for haptics. We conducted performance measures for the magnetorheological fluid clutches for haptics with three commercially available magnetorheological fluids (i.e. 122EG, 132DG, and 140CG from Lord Corp.). The experimental results show that 132DG is a better material for force control. Then, we proposed two types of twin-driven magnetorheological fluid actuators (i.e. link type and belt type) and compared their performance. The results show that the averages of the time constant are 19.1 and 16.1 ms for the link type and belt type, respectively. Furthermore, the averages of torque error are 0.033 and 0.068 N m for the link type and belt type, respectively. However, the belt-type twin-driven magnetorheological fluid actuator is better if a large range of motion is required, while the link-type twin-driven magnetorheological fluid actuator is better if accurate torque control is required.

CFD Analysis of Magnetorheological Fluid Single Valve with an External Magnetic Field

Magnetorheological fluid (MRF) actuator emerged in the last decade as a potential system to replace electro-hydraulic servo system in precision applications. MRF actuator was control using a valve which is regulated with magnetic field. Because of valve performance relate with flow characteristic inside the valve, knowledge about the flow behaviour when magnetic field is applied was important. Currently analytical method was used to model the valve but limited into simple geometry. Reflect to the need of complex geometry of valve, CFD approached was used in this research work to model the fluid flow with presence of different magnetic strength magnitude as a result CFD model shows a good agreement with experiment with 3% error and the MRF velocity was reduce up to 85% when magnetic field applied. As conclusion, CFD model successfully develop and proven to be used as a tool in analysing the MRF flow.

A new constitutive model of a magneto-rheological fluid actuator using an extreme learning machine method

In this work, a new constitutive model of a magneto-rheological fluid (MRF) actuator is proposed using an extreme learning machine (ELM) technique to enhance the prediction accuracy of the field-dependent actuating force. After briefly reviewing existing rheological constitutive models of MRF actuator, ELM algorithm is formulated using a single-hidden layer feed-forward neural network. In this formulation, both the magnetic field and measured shear rates are used as inputs variables, while the shear stress predicted from the ELM training is used as an output variable. Subsequently, in order to validate the effectiveness of the proposed model, the target defined as the error between the prediction and measured data is set. Then, the fitness of the training and prediction performances is evaluated using a normalized root mean square error (NRMSE) method. It is shown that the shear stress estimation based on the ELM model using sinusoidal activation function is more accurate than conventional rheological constitutive models such as Herschel-Bulkley model. It is also demonstrated that the proposed model is capable of predicting the field-dependent yield stress which is defined as an actuating force of the MRF actuator without causing significant errors.

A new hysteresis model based on force–displacement characteristics of magnetorheological fluid actuators subjected to squeeze mode operation

This paper presents a new hysteresis model based on the force–displacement characteristics of magnetorheological (MR) fluid actuators (or devices) subjected to squeeze mode operation. The idea of the proposed model is originated from experimental observation of the field-dependent hysteretic behavior of MR fluids, which shows that from a view of rate-independence of hysteresis, a gap width-dependent hysteresis is occurred in the force–displacement relationship instead of the typical relationship of the force–velocity. To effectively and accurately portray the hysteresis behavior, the gap width-dependent hysteresis elements, the nonlinear viscous effect and the inertial effect are considered for the formulation of the hysteresis model. Then, a model-based feedforward force tracking control scheme is established through an observer which can estimate the virtual displacement. The effectiveness of the proposed hysteresis model is validated through the identification and prediction of the damping force of MR fluids in the squeeze mode. In addition, it is shown that superior force tracking performance of the feedforward control associated with the proposed hysteresis mode is evaluated by adopting several tracking trajectories.

A new magneto-rheological fluid actuator with application to active motion control

A novel magneto-rheological fluid based actuator (MR actuator in short) is proposed for the micro level motion control application. The proposed MR actuator is working based on the principle of magnetic extension and contraction by the MR fluid sandwiched structure between the two electrode type coils. The key enabling concept in this work is to precisely control the biasing current of electrode-coil for achieving the desired displacement of the proposed actuator. The direction and amount of current input to the top and bottom electrode-coils decides the characteristics like contraction, extension and the force generated by the actuator, respectively. In order to undertake a proof-of-concept of the proposed actuator, a simple proportional-integral (PI) controller is designed and implemented in real time for the MR actuating system to control the desired displacement. The process parameters of the MR actuating system are obtained by applying a step input to the electrode- coils, and the PI controller are designed using internal model control (IMC) tuning rule. The experimental realization of the micro-level motion control is easily performed using the MR actuator. It is demonstrated from displacement tracking results that the proposed MR actuating system has a distinctive control characteristic in an active mode. Therefore, this salient control characteristic leads to wide and various applications, especially in micro electro mechanical systems (MEMS) devices fabrication.

Dynamic Performance of Different Metal Foam Magnetorheological Fluid Materials

This paper investigates the dynamic response of different metal foam magnetorheological (MR) fluid materials experimentally. Metal foam MR fluid materials can be used to manufacture the low-cost controllable damping devices without the need of a seal and provide a long service life. The MR fluid is stored in metal foam mainly by the capillary force. In the action of magnetic field, the MR fluid will be extracted out from metal foam and fill up the shear gap, and then, produce the MR effect. Three types of metal foams with different relative permeability, such as Fe, Ni, and Cu, are applied to store the MR fluid. A set of testing systems, including the plate-on-plate shear test rig, electromotor, and force sensor, is built to investigate the dynamic performance of these materials. In order to describe the dynamic response accurately, three parameters of response time are introduced and defined. The magnetic field, both in the shear gap and the pore of metal foam, is simulated by finite element method software. The experimental results show that the response time of metal foam MR fluid materials will change with different currents, which provides the theoretical and experimental basis for the further development of metal foam MR fluid dampers or actuators.

Vibration control of the engine body of a vehicle utilizing the magnetorheological roll mount and the piezostack right-hand mount

In this study, a new controllable engine mounting system for vibration control of passenger vehicles is proposed. The proposed mounting system consists of two smart material actuators: a piezostack actuator and a magnetorheological-fluid actuator. First, the dynamic responses of an in-line four-cylinder engine supported by three rubber mounts are mathematically analysed by considering the six-degree-of-freedom motion of the engine body, whose excitation is generated by the inner forces during the engine combustion process. Second, the proper positions of the two actuators are determined. Two magnetorheological mounts are used as roll mounts, and one piezostack mount is used as the right-hand mount, in order to reduce the unwanted engine vibration in a broadband frequency range. Third, the piezostack mount and the magnetorheological mount are designed and manufactured, followed by installation in the engine mounting system. Subsequently, for effective vibration isolation, a sliding-mode controller, which is robust to disturbances and system uncertainties, is designed. Finally, in order to demonstrate the effectiveness of the proposed new engine mounting system, vibration control performances are evaluated by adopting the hardware-in-the-loop simulation test method associated with the sliding-mode controller. The vibration control responses are presented at various engine operating speeds in the time domain and the frequency domain. It was found that the vibration control performance is improved by 30% at an engine speed of 750 r/min and by 17% at an engine speed of 2000 r/min using the proposed engine mounting system associated with the controllers.

High-flux magnetorheology at elevated temperatures

Commercial applications of magnetorheological (MR) fluids often require operation at elevated temperatures as a result of surrounding environmental conditions or intense localized viscous heating. Previous experimental investigations of thermal effects on MR fluids have reported significant reductions in the magnetorheological stress with increasing temperature, exceeding the predictions made by considering the thermal variations in the individual physical properties of the fluid and solid constituents of a typical MR fluid. In the low-flux regime, designers of MR fluid actuators can alleviate this thermal reduction in stress by increasing the applied magnetic field strength. However, this is not possible in the high-flux regime because of magnetic saturation, and it becomes necessary to explore and understand the intrinsic limitations of the fluid at elevated temperature. We describe a new magnetorheological fixture, which was designed as an accessory to a commercial torsional shear rheometer, capable of applying magnetic flux densities up to 1 T and controlling the sample temperature up to 150°C. During the design of the instrument, close attention was given to the uniformity of the magnetic field applied to the sample by using numerical simulations. Incorporation of a custom-built magnetic flux sensor which matches the environmental capabilities of the fixture enables in situ measurement of the local magnetic field at each temperature. The numerical results are also validated by spatially resolved measurements of the local magnetic field. Finally, we explore the ability of a shift factor between fluid magnetization and yield strength to describe the measured variation in the MR fluid response at elevated temperatures.

Full Factorial Design to Study Material Parameters of Magnetorheological Fluid

This paper presents the effects of magnetorheological (MR) fluid parameters, bidisperse ratio, carrier fluid viscosity and particle volume fraction, on its mechanical behaviour using statistical investigation. Silicone oil-based MR fluid samples were compressed using universal testing machine (UTM) in a vertical direction. A set of eight experiments was designed by Design Expert 7 software in which was conducted at two levels for each factor. Stress-strain curves that obtained from the compression test were then analysed by testXpert analyser software. The responses in terms of maximum stresses at 0.75 of strain were extracted from the curves. The result indicated that a combination of high bidisperse ratio and particle volume fraction, and a low carrier fluid viscosity could produce a high compressive stress. The findings are important to be considered in designing squeeze mode MR fluid actuators.

Design and experimental evaluation of a multidisk magnetorheological fluid actuator

A new multidisk magnetorheological fluid actuator was proposed using the shear stress of magnetorheological fluid between rotating disks. The transmission torque was calculated based on the Bingham model, and the magnetic circuit was designed in accordance with electromagnetic theory. Then, a magnetostatic simulation was conducted to validate the designed magnetic circuit. Furthermore, an experimental study was performed to investigate the performance of the prototype. The results show that the transmission torque increases approximately linearly with the input current within the saturation range of magnetorheological fluid. Both the input current and the gap thickness have little influence on the dynamic response property of the proposed magnetorheological fluid actuator. Moreover, the temperature of magnetorheological fluid increases linearly with the time in the slip and loaded states, and the greater the slip power is, the faster the temperature rises. Furthermore, the temperature rise of magnetorheological fluid will result in the reductions of the torque transmission ability and the dynamic response speed. On the whole, the proposed multidisk magnetorheological fluid actuator has a higher torque capacity and a slightly slower dynamic response in comparison with the present magnetorheological devices. It is promising for applications in many high torque occasions.

1A2-E20 MR流体アクチュエータを用いた体重免荷機構と支持点位置制御機能を有する体重免荷型歩行支援装置に関する研究・開発

1A2-E20 MR流体アクチュエータを用いた体重免荷機構と支持点位置制御機能を有する体重免荷型歩行支援装置に関する研究・開発

Performance Improvement of a Rotary MR Fluid Actuator Based on Electromagnetic Design

This study presents an electromagnetic design methodology for a rotary magnetorheological (MR) fluid actuator. In order to improve the performance of the MR fluid actuator, the magnetic field should be effectively applied to the MR fluid. Therefore, it is important that the magnetic circuit composed of the MR fluid, the ferromagnetic material for magnetic flux path, and the electromagnetic coil is well designed. For this purpose, two effective approaches are proposed: one is to shorten the magnetic flux path by removing the unnecessary bulk of the yoke in order to improve the static characteristic of the MR fluid actuator, and the other is to increase the magnetic reluctance of the magnetic circuit by minimizing the cross-sectional area of the yoke through which the magnetic flux passes in order to improve the dynamic and hysteretic characteristics. The effectiveness of the proposed design methodology is verified through magnetic analysis and a series of basic experiments.

MR 유체 작동기의 전자기적 설계 방법

This paper presents an electromagnetic design methodology for the magneto-rheological (MR) fluid actuator. In order to improve the performance of the MR fluid actuator, the magnetic circuit including the MR fluid, the ferromagnetic material for flux path and the electromagnetic coil should be well designed, thereby the magnetic field intensity can be effectively supplied to the MR fluid. First of all, in order to improve the static characteristic, the length of the flux path is decreased by removing the unnecessary bulk of the yoke. Next, in order to improve the dynamic and hysteretic characteristics, the magnetic reluctance of the ferromagnetic material is increased by minimizing the cross section through which the flux passes. The effectiveness of the proposed design methodology is verified by the magnetic analysis and a series of basic experiments.

Development and Control Experiments of MR-Fluid Actuator.

Device in human machine interface such as interactive force display system requires not only high power and quick response, but also safety for human. Magnetorheological (MR) fluids are materials that change their rheological behavior by an applied magnetic field. The devices using MR fluids have an ability to provide high torque, low inertia, safe device and simple interface. In this study, we propose the magnetic circuit method to develop an actuator using MR fluid. The magnetic characteristics is analyzed by means of the finite element method. In order to investigate the characteristics of the developed MR fluid actuator, the experiments are examined. Finally, the torque control system is constructed and the response of torque is improved.