Sung-Ryong Hong

Comparison of Field-Controlled Characteristics between ER and MR Clutches

This paper presents torque control characteristics of ER (electro-rheological) and MR (magneto-rheological) clutches. As a first step, Bingham properties of ER and MR fluids are experimentally distilled under the shear mode. A nondimensional model of the clutches is established for reasonable comparison. Two clutches have the same principal design parameters such as outer radius of the disc and electrode gap size. Following the manufacturing of two clutches on the basis of the nondimensional model, field-dependent torque levels are experimentally evaluated. A PID (proportional-integral-derivative) controller is then designed and experimentally realized to achieve desired torque. Both regulating and tracking torque control responses of the two clutches are evaluated and compared. In addition, control durability for torque tracking is undertaken to provide a practical feasibility of the proposed clutches.

Vibration Control of a Structural System Using Magneto-Rheological Fluid Mount

In this work, a mixed mode-type magneto-rheological fluid mount (MR mount in short) is devised by considering the nondimensional formulation of Bingham plastic flow, and applied to vibration control of a structural system subjected to external excitations. The structural system consists of a vibrating mass, semi-active MR fluid mount, and passive rubber mounts. The MR mount is installed on the beam structure as a semi-active actuator and supports the vibrating mass, while the flexible beam structure is supported by two passive rubber mounts. After verifying the field-dependent damping force characteristics of the MR mount, the governing equation of the structural system is derived in the modal coordinate and rewritten as a state space control model. The linear quadratic Gaussian (LQG) controller is then formulated in order to attenuate vibration of the structural system. The LQG controller is experimentally realized and control responses such as accelerations and transmitted forces of the structural system are presented in the frequency domain.

Vibration Isolation of Structural Systems Using Squeeze Mode ER Mounts

This paper presents vibration control of flexible structures using squeeze mode ER mounts. After devising the squeeze mode ER mount, its field-dependent damping forces are evaluated at various exciting frequencies. The ER mounts are then incorporated with a flexible beam structure. The governing equation of motion is obtained and an optimal controller which represents controllable damping force is designed to attenuate unwanted structural vibration. The controller is experimentally realized and control responses are presented in the frequency domain. In addition, vibration control responses of a flexible frame structure integrating with the proposed ER mounts are investigated by experiment.

Vibration control of a frame structure using electro-rheological fluid mounts

A squeeze-mode electro-rheological (ER) mount has been designed, manufactured, and applied to the vibration control of a frame structure subjected to external excitations. After verifying that the damping force of the ER mount can be controlled by controlling the applied voltage, a frame structure system supported by spring mounts and the proposed ER mounts has been assembled. The governing equation of the structural system is derived in the modal coordinate and is rewritten as a state-space control model. An optimal controller, which consists of the velocity feedback signal of the frame structure and the force feedback signal transmitted from the exciting point to the mount position, is formulated in order to attenuate the imposed excitations. The controller has been optimized experimentally and control responses such as the acceleration of the frame structure and the transmitted force at each mount position are presented in both time and frequency domains.

Vibration control of a flexible beam structure using squeeze-mode ER mount

Abstract This paper presents vibration control of a flexible beam structure supported by squeeze-mode electro-rheological (ER) mounts. After devising an appropriate size of the squeeze-mode ER mount, its field-dependent damping forces are evaluated at various exciting frequencies. The damping force controllability of the ER mount is also demonstrated by implementing a proportional integral derivative (PID) controller. The ER mounts are then incorporated with a flexible beam structure subjected to external excitations. The governing equation of the structural system is obtained and an optimal controller which consists of the position and velocity components of the beam structure as feedback signals is designed to attenuate the imposed vibrations. The controller is empirically realized and control responses such as beam acceleration are evaluated in time and frequency domains. In addition, the forces transmitted from the input point (exciting position) to the base plate (mount position) are investigated by applying control voltage and constant voltage.

Liquid spring shock absorber with controllable magnetorheological damping

Abstract An automotive suspension strut is investigated that utilizes compressible magnetorheological (CMR) fluid. A CMR strut consists of a double-ended rod in a hydraulic cylinder and a bypass comprising tubing and an MR valve. The diameter of the rods on either side of the piston are set to be different in order to develop spring force by compressing the MR fluid hydrostatically as a result of varying shaft volume in the hydraulic cylinder. The MR bypass valve is adopted to develop a controllable damping force. A hydromechanical model of the CMR strut is derived by considering lumped hydraulic parameters such as compliances of chambers inside the cylinder and flow resistances through the MR bypass valve. The spring force and nominal spring rate owing to fluid compressibility and the controllable flow resistance and pressure drop in the bypass were analytically investigated on the basis of the model. Finally, a CMR strut, filled with silicone oil-based MR fluid, is fabricated and tested. The spring force and variable damping force of the CMR strut are clearly observed in the measured data, and compare favourably with the analytical model. Additionally, characteristics of a double-rod strut whose rod diameters are the same, so that the shaft volume in the hydraulic cylinder is constant, are analysed and compared with a CMR strut whose rod diameters are different.

COMPARISON OF DAMPING FORCE MODELS FOR AN ELECTRORHEOLOGICAL FLUID DAMPER.

In this work, five different models are proposed to predict the field-dependent damping force of an electrorheological (ER) damper and are compared. These are: the Bingham plastic model, the hysteretic Bingham plastic model, the hysteretic biviscous model, the Bouc-Wen model and the hydro-mechanical model. After briefly describing the inherent characteristics of each model, model parameters are identified using a set of experimental data that are obtained by changing electric fields and excitation frequencies. The identified parameters are analysed and used to reconstruct the damping force – the piston velocity plot that directly indicates the hysteresis behaviour of the ER damper and compared with the measured hysteresis loop. In addition, the damping force error between the prediction and experiment is evaluated for each model.

Control and response characteristics of a magnetorheological fluid damper for passenger vehicles

This paper presents control characteristics of a semi-active magneto-rheological (MR) fluid damper for a passenger vehicle. A cylindrical MR damper is devised and its governing equation is derived. After verifying that the damping force of the MR damper can be continuously tuned by the intensity of the magnetic field, PID controller is employed to achieve the desired damping force. The proposed MR damper is then applied to a full-car model and performance characteristics of the full-car such as vertical acceleration of the body are evaluated via hardware-in-the-loop-simulation (HILS).

A Unifying Perspective on the Quasi-steady Analysis of Magnetorheological Dampers

A magnetorheological (MR) fluid, modeled as a Bingham plastic (BP) material, is characterized by a field dependent yield stress, and a (nearly constant) postyield plastic viscosity. Based on viscometric measurements, such a BP model is an idealization to physical MR behavior, albeit a useful one. A better approximation involves modifying both the preyield and postyield constitutive behavior as follows: (1) assume a high viscosity preyield behavior when the shear stress is less than the transition stress, and (2) assume a power law fluid (i.e., strain rate dependent viscosity) when the shear stress is greater than the transition stress. Assuming a power law fluid in postyield allows the model to account for shear thinning behavior exhibited by MR fluids at higher strain rates. Such an idealization for MR fluid constitutive behavior is called an viscous-power law model, or a Herschel—Bulkley (HB) model with preyield viscosity. This study develops a quasi-steady analysis for such a constitutive MR fluid behavior applied to an MR flow mode damper. Closed form solutions are developed for the fluid velocity, as well as key performance metrics, such as damping capacity and dynamic range (ratio of field-on to field-off force). For the given fluid properties and flow mode damper geometry, the fluid velocity profile and gradient, and the relationship of the damper force and piston velocity are analyzed. In addition, specializations to existing models, such as the HB, biviscous, and BP models, are shown to be easily captured by this model when physical constraints (idealizations) are placed on the rheological behavior of the MR fluid.

Active vibration control of a flexible structure using an inertial type piezoelectric mount

This work proposes a new type of inertial mount featuring piezoelectric material and applies it to the vibration control of a flexible structural system. The dynamic model of the piezoelectric actuator consisting of an inertial mass and a piezoceramic stack is established and the inertial force of the actuator is experimentally evaluated. The inertial type of the piezoelectric mount is then devised and its governing equation is derived. In order to demonstrate the effectiveness of the proposed mount, a flexible structural system is constructed and its dynamic model is formulated in the modal coordinate. A linear quadratic Gaussian (LQG) controller associated with the piezoelectric mount is designed to attenuate the vibration of the structural system. The LQG controller is experimentally realized and control responses such as acceleration of the structural system are evaluated in the frequency and time domains.