Magnetorheological Clutch Research Articles

Investigation of the torque transmission time constant of a multi-disc magnetorheological clutch in the case of ramp function excitation

In this work the torque transmission time constant of a multi-disc magnetorheological (MR) fluid clutch is presented. The self-built clutch contains six layers of MR fluid and it is excited by an external electromagnetic coil. The transmitted torque is measured by a torque sensor using a self-developed LabVIEW software. Torque transmission is measured using ramp excitation with different slopes. The time constant of the clutch is derived from the time delay of the torque response. Our measurements showed the time constants as a hyperbolic function of the slope of the ramp excitation.

A multi-pole magnetorheological clutch powered by permanent magnets and excitation coils

This article presents a new design of a multi-pole magnetorheological (MR) clutch, with a hybrid magnetization using several permanent magnets and several excitation coils. The permanent magnets are used as the first source of generating the magnetic field, and the excitation coils are used to adjust the magnetic field to the required value. Firstly, a detailed illustration of the mechanical design of the MR clutch is presented. The principal design parameters of the proposed clutch are determined to achieve maximum torque according to the magnetic circuit. After that, the torque model is established, and simulations are conducted to evaluate the magnetic circuit design. Subsequently, an experimental set-up is established, and the proposed MR clutch is designed and manufactured, and a series of experiments are carried out. The results clearly show that different torque output can be obtained by controlling the current magnitude and direction of each coil. Finally, to achieve a precise feedback torque control, the design of a current controller is carried out using conventional proportional-integral-derivative (PID) control scheme. The results demonstrate that the designed PID controller can be used to obtain the desired torque.

Analysis of magnetorheological clutch with double cup-shaped gap excited by Halbach array based on finite element method and experiment

This work describes the magnetic analysis of an innovative double cup-shaped gap magnetorheological (MR) clutch featuring with three smart MR gels. Four kinds of Halbach array is used to excite the MR gel. The apparatus is designed by using a magneto/mechanical finite element method model, which is numerical calculated by COMSOL Multiphysics software. After describing the configuration, the transmittable torque in the designed MR clutch is derived based on the Bingham-Plastic field-dependent constitutive model of the MR gel. Considering the viscosity in the model building, such as the shear yield stress, which also various with change of magnetic flux density. The magnetic flux density distribution, the shear yield stress distribution, the dynamic viscosity distribution and the shear stress distribution inside the MR gel are obtained and carefully studied. Furthermore, the chain layer of internal cylindrical part, external cylindrical part, internal disc part and external disc part with lowest shear stress are found to calculate the transmission torque and slip torque. Then, the structure of the prototype is optimized based on multi-physics analysis. Finally, the optimal MR clutch is developed and the magneto-static torque is tested with detail analysis.

Principle design and control of a brake-by-wire actuator featuring magnetorheological clutch

Electro-mechanical brake (EMB), driven by a motor to push the brake pads to clamp the brake disk for braking, is considered as the future of vehicle braking system, because of its simple structure and controllable braking force. However, EMB must face the problem of motor blocking when it works in a long-time continuous braking condition. When the motor is blocking, the current in the coil windings is large enough to burn the motor down, leading to the failure of EMB, which is a great threat to driving safety. To solve the problem, a new brake-by-wire actuator featuring magnetorheological (MR) clutch (MRC) – an EMB combining with an MRC, i.e., BBW-MRC, is presented in this paper. Specifically, the BBW-MRC is composed of a driving motor, an MRC, a planetary gear reducer, a ball screw, brake pads, and a brake disk. The motor output is transmitted to the MRC through the reducer, and it is controlled in real-time, continuously, and as expected by the MRC via controlling its applied current. The ball screw is driven by the MRC and pushes the brake pads to clamp the brake disk to realize braking in time. The small-scaled BBW-MRC system and the corresponding test bench are developed, and a hierarchical control strategy applied to the BBW-MRC system is designed. Based on the test bench, a series of tests are carried out on the BBW-MRC system, including the stability test of the BBW-MRC system under a long-time braking condition, the braking force response test of the BBW-MRC, and the braking force tracking test. Research results show that: (1) the BBW-MRC system has a quick and accurate performance to track desired braking forces; (2) under long-time braking conditions, the braking force keeps stable and the surface temperature of the motor has a normal change; and (3) the braking force response time has a 53.5% improvement over the EMB that driven by the motor directly.

Design and Control of Multi-Plate MR Clutch Featuring Friction and Magnetic Field Control Modes.

A magnetorheological (MR) multi-plate clutch was proposed with both mechanical friction mode and magnetic field control modes. The magnetic field control mode was based on an MR fluid coupler that changed its viscous properties according to the density of an applied magnetic field. This mode was used in the early stage of clutch operation to reduce the impact of friction between the disc and plate, and eliminate to the extent possible the difference in their relative speeds when contacting each other in later stages. Once the rotational speed difference between the disc and plate was reduced, the clutch was operated in mechanical friction mode by compressing the friction surfaces together. A torque modeling equation was then derived for each mode based on the Bingham model of the MR fluid, and the transmission torque of the proposed multi-plate clutch was derived using these equations as well as magnetic field analysis results obtained using ANSYS Maxwell. A multi-plate MR clutch was then fabricated, and its torque transmission characteristics were evaluated in the magnetic field control and mechanical friction modes. The results confirmed that the model-based torque calculations were consistent with the observed transmission torque. Finally, control algorithms for mechanical friction only and mixed mechanical friction/magnetic field control torque tracking of the proposed MR multi-plate clutch were designed, and their performances were evaluated when applying unit step command, half-sine-wave command, and rotational speed changes. The results indicated that the torque tracking control was performed smoothly, demonstrating the advantages of the proposed clutch.

Design, experiment, and performance analysis of magnetorheological clutch with uniform magnetic field distribution along the radial direction for tension control.

High-precision tension control is very important for industrial production. Benefit from the unique property of magnetorheological (MR) fluid, a MR clutch is a potential device in a tension control system due to its fast response and large output dynamics. In this paper, based on the detailed analysis of axial magnetic induction intensity generated by the coil along the radial distribution, a shear-mode MR clutch with uniform magnetic field distribution along the radial direction is proposed for the tension control system. A theoretical model of torque transmission and a magnetic circuit were derived, and a magnetostatic simulation was carried out to validate the effectiveness of the proposed circuit design. Experimental evaluation was conducted to investigate the static and dynamic transmission torque property. Finally, a proportional-integral-differential controller was designed to regulate the output torque. Experimental testing demonstrated the effectiveness and practical feasibility of the MR clutch in tension control.

Integrated analytical-field design method of multi-disc magnetorheological clutches for automotive applications

Integrated analytical-field design method of multi-disc magnetorheological clutches for automotive applications

The Choice of the Optimal Number of Discs in an MR Clutch from the Viewpoint of Different Criteria and Constraints

This paper focuses on magnetorheological clutches (MR clutches) with a disc structure that can be designed as one-disc or multi-disc clutches (number of discs: N = 1, N > 2). The main goal of the paper is to compare their overall dimensions (lengths and radii), masses, volumes, and characteristic factors—torque per mass ratio and torque per volume ratio for MR clutches that develop the same given clutching torque Tc but differ in the number of discs (it is assumed that the number of discs of the primary member varies from one to four). This analysis develops charts and guidelines that will allow designers to choose the appropriate number of discs from the view point of various criteria, and with various limitations regarding geometry, geometric proportions, mass, volume, or restrictions on the amount of active materials used in the manufacturing process. The limitations on the active materials used are of particular importance in the case of mass production. Our methodology uses a comparative study, which can also be used when comparing design solutions of other electromechanical converters.

A Framework for Demonstration Devices Used in Distance-Learning Environments

Distance-learning has become widespread around the world. Many training areas such as engineering require the acquisition of practical rather than theoretical knowledge. In this paper, a framework is presented in the form of four pilot projects which is used for practical laboratory measurements in a distance-learning environment. Four demonstration devices consisting of an induction motor drivetrain, a magnetorheological clutch as well as a rolling resistance and an ultrasonicsensor were built and several examples of measurements presented.The system, based on accessible and user-friendly hardware, is cost-effective, simple to program and can be adapted to suit any application.

Design and testing of a conventional clutch filled with magnetorheological fluid activated by a flexible permanent magnet at low compressive load: Numerical simulation and experimental study

Abstract In this research article, the working of conventional clutch (CC) filled with magnetorheological (MR) fluid was tested at low compressive load. The flexible permanent magnetic sheet (FMS) controlled the chain strength of MR fluid. A single clutch plate based on FMS was fabricated and tested on the developed test rig. The characteristics of the developed single plate MR clutch (SPMRC) were found by the testing and mathematical calculations. Magnetic circuit analysis presents the magnetic field distribution in the developed MR clutch. The mathematical expression for the torque transmission due to shear and compression is presented. COMSOL Multiphysics 5.3a software is used for the magnetic field simulation at different loading conditions. The temperature distribution in the developed clutch is simulated and experimented. It is observed from the results that the input shaft oscillation in the reduces more during disengagement in the SPMRC than the CC.

Thermal and Tribological Performance of Graphite Flake-Based Magnetorheological Fluid Under Shear Mode Clutch

Abstract In this research work, graphite flake has been used as an additive in magnetorheological (MR) fluid to improve its thermal and tribological performance. MR fluids with varying amounts of graphite flakes (0.5, 1, 2, 3, 4, and 5 wt%) are prepared to show effective thermal and tribological performance. A test rig is developed with a DC motor, torque sensor, and MR clutch operated in a shear mode to test the torque transmission. Results show the lubrication effects of graphite flakes in the MR fluid. Torque transmission is improved in on-state and off-state using graphite flakes-based MR fluid as compared with conventional MR fluid. Heating of the MR clutch is also reduced with the graphite flakes-based MR fluid. Wear marks and damages are decreased significantly with the increased amount of graphite flakes as found in surface roughness tests. Scanning electron microscopy and energy-dispersive spectroscopy are used to characterize the worn surfaces. This research provides information about the effectiveness of graphite flakes in the MR clutch to improve the device’s performance.

Lubrication performance of magnetorheological fluid in shear mode magnetorheological clutch with and without groove

In this work, the lubrication performance of magnetorheological fluid-filled parallel discs of shear mode magnetorheological clutch is investigated. A magnetorheological fluid contains magnetic particles responsible for the yield strength and hence torque transmission capability in the magnetorheological clutch. The wear damages of magnetic particles of a magnetorheological fluid and magnetorheological clutch discs are examined by scanning electron microscopy and optical microscopy. Energy-dispersive X-ray spectroscopy is used to investigate the variation in chemical composition before and after the experimental test. A test rig is developed to test the torque transmission for a fabricated magnetorheological clutch with a grooved and non-grooved disc. The grooves' impact on both magnetorheological clutch discs' wear and magnetorheological fluid is investigated. It has been observed that the minimum wear damage occurs in the magnetic particles and the disc surface for the circular grooved magnetorheological clutch disc surface than the non-grooved disc surface. An effect of surface texture on the temperature distribution of the magnetorheological clutch is studied through simulation. Simulation results show that the groove's presence on the disc surface can improve the magnetorheological clutch's heat transfer. Hence, the grooved texture improves the lubrication performance and durability of both magnetorheological fluid and magnetorheological clutch.

High-performance magneto-rheological clutches for direct-drive actuation: Design and development.

This paper presents an improved design, complete analysis, and prototype development of high torque-to-mass ratio Magneto-Rheological (MR) clutches. The proposed MR clutches are intended as the main actuation mechanism of a robotic manipulator with five degrees of freedom. Multiple steps to increase the toque-to-mass ratio of the clutch are evaluated and implemented in one design. First, we focus on the Hall sensors’ configuration. Our proposed MR clutches feature embedded Hall sensors for the indirect torque measurement. A new arrangement of the sensors with no effect on the magnetic reluctance of the clutch is presented. Second, we improve the magnetization of the MR clutch. We utilize a new hybrid design that features a combination of an electromagnetic coil and a permanent magnet for improved torque-to-mass ratio. Third, the gap size reduction in the hybrid MR clutch is introduced and the effect of such reduction on maximum torque and the dynamic range of MR clutch is investigated. Finally, the design for a pair of MR clutches with a shared magnetic core for antagonistic actuation of the robot joint is presented and experimentally validated. The details of each approach are discussed and the results of the finite element analysis are used to highlight the required engineering steps and to demonstrate the improvements achieved. Using the proposed design, several prototypes of the MR clutch with various torque capacities ranging from 15 to 200 N·m are developed, assembled, and tested. The experimental results demonstrate the performance of the proposed design and validate the accuracy of the analysis used for the development.

A Cable-Driven Three-DOF Wrist Rehabilitation Exoskeleton With Improved Performance.

This paper developed a cable-driven three-degree-of-freedom (DOF) wrist rehabilitation exoskeleton actuated by the distributed active semi-active (DASA) system. Compared with the conventional cable-driven robots, the workspace of this robot is increased greatly by adding the rotating compensation mechanism and by optimizing the distribution of the cable attachment points. In the meanwhile, the efficiency of the cable tension is improved, and the parasitic force (the force acting on the joint along the limb) is reduced. Besides, in order to reduce the effects of compliant elements (e.g., cables or Bowden cables) between the actuators and output, and to improve the force bandwidth, we designed the DASA system composed of one geared DC motor and four magnetorheological (MR) clutches, which has low output inertia. A fast unbinding strategy is presented to ensure safety in abnormal conditions. A passive training algorithm and an assist-as-needed (AAN) algorithm were implemented to control the exoskeleton. Several experiments were conducted on both healthy and impaired subjects to test the performance and effectiveness of the proposed system for rehabilitation. The results show that the system can meet the needs of rehabilitation training for workspace and force-feedback, and provide efficient active and passive training.

Multi-State Modelling and Observation of Magneto-Rheological Clutch With Rate-Dependent Hysteresis Characteristic

Magneto-rheological clutches (MRCs) are potential for providing jointed robots with the capability of behaving compliantly. However, due to the nonlinear dynamics of rate-dependent hysteresis exhibited by the MRC, precisely controlling its behaviors is still cumbersome. This paper firstly proposes a multi-state MRC model described by multiple ordinary differential equations (ODEs) that captures the complicated rate-dependent hysteresis phenomenon. The model offers better estimation accuracy of rate-dependent hysteresis compared to the Bouc-Wen model. Then, to further improve the modelling performance in various inputs, this paper designs a robust and exact observer based on the super-twisting algorithm (STA) to compensate the model uncertainties. It exactly estimates the output torque of MRC by compensating for the model uncertainties, even when the parameters of the MRC model are not optimized. Comparisons and experiments demonstrate the robustness and estimation accuracy of the STA observer.

Experimental characterization and evaluation of magnetorheological clutch for an electric two-wheeler application

This work makes an effort to explore a magnetorheological clutch (MRC) prototype for a two-wheeled electric vehicle owing to its quick response, accurate torque transmission control by varying the magnetic field; and electro-mechanical interface. A design variation ‘MRC with-slits’ is proposed to enhance the torque transmission capacity and compared with ‘MRC without-slits’. The torque transmitting capability of the MRC with and without-slits is evaluated analytically and experimentally with respect to input parameters viz. current and speeds. The rise in torque transmission due to the presence of slits and thermal behavior is validated experimentally. Correlation and uncertainty analysis are used to confirm the findings. The weight and size of the MRC remains a major challenge for its successful integration with a two-wheeled electric vehicle application.

Experimental assessment of a linear actuator driven by magnetorheological clutches for automotive active suspensions.

The main functions of automotive suspensions are to improve passenger comfort as well as vehicle dynamic performance. Simultaneously satisfying these functions is not possible because they require opposing suspension adjustments. This fundamental design trade-off can be solved with an active suspension system providing real-time modifications of the suspension behavior and vehicle attitude corrections. However, current active suspension actuator technologies have yet to reach a wide-spread commercial adoption due to excessive costs and performance limitations. This paper presents a design study assessing the potential of magnetorheological clutch actuators for automotive active suspension applications. An experimentally validated dynamic model is used to derive meaningful design requirements. An actuator design is proposed and built using a motor to feed counter-rotating MR clutches to provide upward and downward forces. Experimental characterization shows that all intended design requirements are met, and that the actuator can output a peak force of ±5300 N, a peak linear speed of ±1.9 m/s and a blocked-output force bandwidth of 92 Hz. When compared to other relevant technologies, the MR approach simultaneously shows both better force density and speeds (bandwidth) while adding minimal costs and weight. Results from this experimental assessment suggest that MR slippage actuation is promising for automotive active suspensions.

Hybrid multi-plate magnetorheological clutch featuring two operating modes: Fluid coupling and mechanical friction

Recently, there has been a rising demand for high-performance clutches in mechanical systems owing to the development of industrial technologies. This paper, therefore, proposes a hybrid multi-plate Magnetorheological (MR) clutch that has both fluid coupling and mechanical friction modes. To reduce impact when the plates are in contact with each other, a fluid coupler’s operating mode was used at the beginning of the clutch operation. For this, torque modeling in each mode was induced based on the Bingham model of the MRF. Using the induced torque modeling and ANSYS Maxwell’s magnetic field analysis results, the design procedure for a multi-plate clutch was implemented. Based on the design results, a hybrid multi-plate MR clutch was manufactured. Finally, the performance of the manufactured MR clutch was evaluated using a torque tester. The assessment confirmed that the proposed torque modeling and simulation results mostly matched the test results.

Novel active magnetorheological knee prosthesis presents low energy consumption during ground walking

This study analyses the energy consumption of an active magnetorheological knee (AMRK) actuator that was designed for transfemoral prostheses. The system was developed as an operational motor unit (MU), which consists of an EC motor, a harmonic drive and a magnetorheological (MR) clutch, that operates in parallel with an MR brake. The dynamic models of the MR brake and MU were used to simulate the system’s energetic expenditure during over-ground walking under three different working conditions: using the complete AMRK; using just its motor-reducer, to operate as a common active knee prosthesis (CAKP), and using just the MR brake, to operate as a common semi-active knee prosthesis (CSAKP). The results are used to compare the MR devices power consumptions with that of the motor-reducer. As previously hypothesized, to use the MR brake in the swing phase is more energetically efficient than using the motor-reducer to drive the joint. Even if using the motor-reducer in regenerative braking mode during the stance phase, the differences in power consumption among the systems are remarkable. The AMRK expended 16.3 J during a gait cycle, which was 1.6 times less than the energy expenditure of the CAKP (26.6 J), whereas the CSAKP required just 6.0 J.

Optimized Design for Cable-Driven Shoulder-Elbow Exoskeleton Robot

The cable-driven exoskeletons have the advantages of low inertia and simple structure, and they are widely applied for human augmentation and rehabilitation. However, they have limited workspace and tension efficiency because of the unidirectional nature of the cables. The limited performance affects the human-robot interaction and leads to potential danger. The workspace and tension efficiency can be optimized by conventional methods, which are adjusting the cable attachment points and increasing the actuators. But the workspace still cannot cover the human joint space of activities of daily living, and the efficiency is also not high. This paper analyzed the specific application for shoulder and elbow joints rehabilitation and proposed a dynamic adaptive structure. This design can increase the workspace and improve tension efficiency greatly. The dynamic compensation control strategy is designed for the optimized system. Besides, in order to reduce the effects of compliant elements (e.g., cables or Bowden cables) between the actuators and output, and to improve the force bandwidth, we designed the distributed active semi-active system composed of the geared DC motor and magnetorheological clutches, which has low output inertia. The related experiments are carried out based on several healthy subjects. The results verified that the exoskeleton with the dynamic adaptive structure has a large workspace covering the activities of daily living joint space, high tension efficiency, and high force bandwidth, which is beneficial for the safety and comfort of human-robot interaction during rehabilitation training.