Seung-Bok Choi

Bio: Seung-Bok Choi is an academic researcher from Inha University. The author has contributed to research in topics: Magnetorheological fluid & Damper. The author has an hindex of 54, co-authored 842 publications receiving 13440 citations. Previous affiliations of Seung-Bok Choi include State University of New York System & Michigan State University.

Vibration Control of a MR Seat Damper for Commercial Vehicles

Abstract: This paper presents vibration control of a semi-active seat suspension with a magneto-rheological (MR) fluid damper, which is applicable to commercial vehicles such as large size of trucks. A cylindrical MR seat damper is designed on the basis of the Bingham model of the MR fluid. After manufacturing the seat damper, field-dependent damping force characteristics are experimentally evaluated. A semi-active seat suspension system installed with the seat damper is then constructed and its governing equation of motion is derived. A skyhook controller to reduce vibration level at the driver’s seat is formulated and realized in a closed-loop control fashion. The control responses, such as acceleration transmissibility, are investigated in both frequency and time domains. In addition, a full-vehicle model featuring the proposed semi-active seat suspension is established and its vibration control performances are evaluated via the hardware-in-the-loop simulation (HILS).

Control and Response Characteristics of a Magneto-Rheological Fluid Damper for Passenger Vehicles:

Abstract: This paper presents control characteristics of a full-car suspension featuring a semi-active magnetorheological (MR) fluid damper A cylindrical MR damper is devised and its field-dependent damping force is evaluated with respect to the piston velocity After verifying that the damping force can be continuously controlled by the intensity of the magnetic field, the MR damper is applied to a full-car model The governing equations of motions, which include vertical, pitch, and roll motions are derived and incorporated with the skyhook controller Control characteristics of the full-car suspension installed with the proposed MR damper are evaluated through hardware-in-the-loop simulation (HILS), and presented in both time and frequency domains

Geometry optimization of MR valves constrained in a specific volume using the finite element method

Abstract: This paper presents the geometric optimal design of magnetorheological (MR) valves in order to improve valve performance, such as pressure drop. The optimization problem is to find the optimal geometric dimensions of MR valves constrained in a specific volume. After describing the configuration of MR valves, their pressure drops are investigated on the basis of the Bingham model of an MR fluid. Then, the valve ratio, which is an objective function, is derived by considering the field-dependent (controllable) and viscous (uncontrollable) pressure drops of the MR valves. Subsequently, the optimization procedure using a golden-section algorithm and a local quadratic fitting technique is constructed via a commercial finite element method (FEM) parametric design language. From the constructed optimization tool, optimal solutions of the MR valves, which are constrained in a specific cylindrical volume defined by its radius and height, are calculated and compared with analytical ones. In addition, several different types of MR valves are optimized in the same specific volume and results are presented.

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Energy harvesting vibration sources for microsystems applications

Abstract: This paper reviews the state-of-the art in vibration energy harvesting for wireless, self-powered microsystems. Vibration-powered generators are typically, although not exclusively, inertial spring and mass systems. The characteristic equations for inertial-based generators are presented, along with the specific damping equations that relate to the three main transduction mechanisms employed to extract energy from the system. These transduction mechanisms are: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ active materials that generate a charge when mechanically stressed. A comprehensive review of existing piezoelectric generators is presented, including impact coupled, resonant and human-based devices. Electromagnetic generators employ electromagnetic induction arising from the relative motion between a magnetic flux gradient and a conductor. Electromagnetic generators presented in the literature are reviewed including large scale discrete devices and wafer-scale integrated versions. Electrostatic generators utilize the relative movement between electrically isolated charged capacitor plates to generate energy. The work done against the electrostatic force between the plates provides the harvested energy. Electrostatic-based generators are reviewed under the classifications of in-plane overlap varying, in-plane gap closing and out-of-plane gap closing; the Coulomb force parametric generator and electret-based generators are also covered. The coupling factor of each transduction mechanism is discussed and all the devices presented in the literature are summarized in tables classified by transduction type; conclusions are drawn as to the suitability of the various techniques.

A review of power harvesting using piezoelectric materials (2003–2006)

Abstract: The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their limited lifespan, thus necessitating their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of a disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with piezoelectric materials. This article will review recent literature in the field of power harvesting and present the current state of power harvesting in its drive to create completely self-powered devices.

Structural control: past, present, and future

Abstract: This tutorial/survey paper: (1) provides a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control and monitoring of civil engineering structures; and (2) provides a link between structural control and other fields of control theory, pointing out both differences and similarities, and points out where future research and application efforts are likely to prove fruitful. The paper consists of the following sections: section 1 is an introduction; section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals with research needs. An extensive list of references is provided in the references section.

Atomization and Sprays

Abstract: Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index