Showing papers by "Quoc Hung Nguyen published in 2009"

Optimal design of a vehicle magnetorheological damper considering the damping force and dynamic range

Abstract: This paper presents an optimal design of a passenger vehicle magnetorheological (MR) damper based on finite element analysis. The MR damper is constrained in a specific volume and the optimization problem identifies the geometric dimensions of the damper that minimize an objective function. The objective function consists of the damping force, the dynamic range, and the inductive time constant of the damper. After describing the configuration of the MR damper, the damping force and dynamic range are obtained on the basis of the Bingham model of an MR fluid. Then, the control energy (power consumption of the damper coil) and the inductive time constant are derived. The objective function for the optimization problem is determined based on the solution of the magnetic circuit of the initial damper. Subsequently, the optimization procedure, using a golden-section algorithm and a local quadratic fitting technique, is constructed via commercial finite element method parametric design language. Using the developed optimization tool, optimal solutions of the MR damper, which are constrained in a specific cylindrical volume defined by its radius and height, are determined and a comparative work on damping force and inductive time constant between the initial and optimal design is undertaken.

Optimal design of MR shock absorber and application to vehicle suspension

Abstract: This paper presents an optimal design of a magnetorheological (MR) shock absorber based on finite element analysis. The MR shock absorber is constrained in a specific volume and the optimization problem identifies geometric dimensions of the shock absorber that minimize a multi-objective function. The objective function is proposed by considering the damping force, dynamic range and the inductive time constant of the shock absorber. After describing the configuration of the MR shock absorber, a quasi-static modeling of the shock absorber is performed based on the Bingham model of an MR fluid. The initial geometric dimensions of the shock absorber are then determined based on the assumption of constant magnetic flux density throughout the magnetic circuit. The objective function of the optimization problem is derived based on the solution of the initial shock absorber. An optimization procedure using a golden-section algorithm and a local quadratic fitting technique is constructed via a commercial finite element method parametric design language. Using the developed optimization tool, optimal solutions of the MR shock absorber, which is constrained in a specific cylindrical volume defined by its radius and height, are determined. Subsequently, a quarter-car suspension model with the optimized MR shock absorber is formulated and the vibration control performance of the suspension is evaluated under bump and sinusoidal road conditions.

An analytical method for optimal design of MR valve structures

Abstract: This paper proposes an analytical methodology for the optimal design of a magnetorheological (MR) valve structure. The MR valve structure is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the yield stress pressure drop of a MR valve or the yield stress damping force of a MR damper. In this paper, the single-coil and two-coil annular MR valve structures are considered. After describing the schematic configuration and operating principle of a typical MR valve and damper, a quasi-static model is derived based on the Bingham model of a MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying Kirchoff's law and the magnetic flux conservation rule. Based on quasi-static modeling and magnetic circuit analysis, the optimization problem of the MR valve and damper is built. In order to reduce the computation load, the optimization problem is simplified and a procedure to obtain the optimal solution of the simplified optimization problem is presented. The optimal solution of the simplified optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution of the original optimization problem and the optimal solution obtained from the finite element method.

Dynamic modeling of an electrorheological damper considering the unsteady behavior of electrorheological fluid flow

Abstract: In this study, dynamic modeling of an electrorheological (ER) damper is performed considering the unsteady behaviors of ER fluid flow through the annular duct of the damper. After describing the configuration of the ER damper, quasi-static modeling of the damper is conducted on the basis of the Bingham model of ER fluid. The pressure drop of the unsteady ER fluid flow through the annular duct between the electrodes of the damper with a known variation of flow rate is then obtained by solving the momentum equation of the ER fluid flow using the Laplace transform technique. Based on the proposed unsteady flow solution, the simulated results are obtained and compared with measured ones in order to evaluate the effectiveness of the proposed model. In addition, in order to reduce the computation load, a simplified solution of the dynamic damping force is proposed with validation.

A new approach for dynamic modeling of an electrorheological damper using a lumped parameter method

Abstract: This work proposes a new method for dynamic modeling of an electrorheological (ER) damper using a lumped parameter method. After describing the configuration and operating principle of the ER damper, quasi-static modeling of the damper is conducted on the basis of the Bingham model of ER fluid. Subsequently, the lumped parameter models of ER fluid flows in the damper are established and the integrated lumped model of the whole damper system is obtained by taking into account the dynamic motions of the annular duct, upper chamber, lower chamber and connecting pipe. In order to demonstrate the effectiveness of the proposed dynamic model, a comparative work between the simulation and the experiment is undertaken. This is performed under various piston motions with different excitation magnitudes and frequencies. In addition, the effect of ER fluid compressibility and initial pressure in the accumulator on the hysteresis of the ER damper is investigated.

Geometric optimal design of MR damper considering damping force, control energy and time constant

Abstract: This paper presents an optimal design of magnetorheological (MR) damper based on finite element analysis. The MR damper is constrained in a specific volume and the optimization problem identifies geometric dimensions of the damper that minimizes an objective function. The objective function is proposed by considering the damping force, dynamic range and the inductive time constant of the damper. After describing the configuration of the MR damper, a quasi-static modelling of the damper is performed based on Bingham model of MR fluid. The initial geometric dimensions of the damper are then determined based on the assumption of constant magnetic flux density throughout the magnetic circuit of the damper. Subsequently, the optimal design variables that minimize the objective function are determined using a golden-section algorithm and a local quadratic fitting technique via commercial finite element method parametric design language. A comparative work on damping force and time constant between the initial and optimal design is undertaken.

Performance evaluation of a high-speed jetting dispenser actuated by a ring-type piezostack

Abstract: This article presents performance results of a new type of jetting dispenser driven by a ring-type piezostack actuator. The proposed dispenser can provide a very small dispensing dot size of a low viscous adhesive, from 50 to 500 cp, at a high dispensing flowrate in semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering behaviours of the piezostack, the actuating spring, the dispensing needle, and the adhesive fluid dynamics. In the modelling, a lumped parameter method is applied to model the adhesive, for which the rheological property is approximately expressed by the Bingham model. The governing equation of the dispensing system is then derived by integrating the structural model with the fluid model. Based on the proposed model, the jetting dispenser is designed and manufactured. The dispensing performances such as dot size and dispensing flowrate are then evaluated from both the...

Unsteady flow modeling of an electrorheological valve system with experimental validation

Abstract: This paper presents an unsteady flow modeling of an electrorheological (ER) valve system and verifies its effectiveness through experimental investigation. After designing a cylindrical ER valve, a dynamic model for unsteady flow of ER fluid is derived by considering the fluid inertia. The field-dependent pressure drop of the unsteady flow is then calculated and validated with the experimental result. In order to clearly observe the difference between the unsteady flow model and the steady model, the flow rate of the ER valve is analyzed under low frequency and high frequency sinusoidal inputs. In addition, in order to demonstrate the effectiveness of the proposed unsteady flow model, a position control system activated by ER valves is constructed. The dynamic model of the control system is formulated on the basis of the unsteady flow analysis, and control responses such as flow rate, pressure drop and displacement are compared between the unsteady flow and the steady flow models.

Dynamic Modeling of ER Damper Considering Fluid Compressibility

Abstract: This paper proposes a new method for dynamic modeling of electrorheological(ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

Unsteady laminar flow analysis of ER valve systems: Modeling and simulation

Abstract: This paper proposes a new method to model electrorheological valve systems based on the unsteady flow analysis. After describing the mechanism and operational principle of the ER valve, the unsteady flow in the valve is identified. A method to model this unsteady flow is developed based on the assumptions that the ER fluid follows Bingham behavior and the pressure drop of the unsteady flow results from the independent pressure drops due to the yield stress, inertia and fluid viscosity. The dynamic model of the valve is then derived based on the unsteady flow analysis. The time response of ER effect is also considered in the dynamic model. Using the proposed model, the performance of the ER valve is predicted and validated by comparing with experimental results. In addition, the flow rate predicted by the unsteady flow model is compared with that by the steady flow model.

Design of Ultrasonic Vibrator for Conformal Coating Spray in LED Packaging

Abstract: This paper presents the design of ultrasonic vibrator utilizing a piezoelectric actuator. After describing a geometric configuration of the proposed atomizer, an analytical model of the ultrasonic atomizer is formulated by considering liquid film surface theory and wave theory. The dynamic analysis is then undertaken using a finite element analysis to determine principal longitudinal vibration modes. An optimization is performed by taking the amplitude of the tip displacement as an objective function. The fluid flow characteristics of the proposed atomizer is also analyzed under operating conditions through commercial software FLUENT.