Sung Hoon Ha

Design and vibration control of military vehicle suspension system using magnetorheological damper and disc spring

This paper proposes a new type of magnetorheological (MR) fluid based suspension system and applies it to military vehicles for vibration control. The suspension system consists of a gas spring, a MR damper and a safety passive damper (disc spring). Firstly, a dynamic model of the MR damper is derived by considering the pressure drop due to the viscosity and the yield stress of the MR fluid. A dynamic model of the disc spring is then established for its evaluation as a safety damper with respect to load and pressure. Secondly, a full military vehicle is adopted for the integration of the MR suspension system. A skyhook controller associated with a semi-active actuating condition is then designed to reduce the imposed vibration. In order to demonstrate the effectiveness of the proposed MR suspension system, a computer simulation is undertaken showing the vibration control performance of such properties as vertical displacement and pitch angle, evaluated for a bumpy road profile.

Accurate position control of a flexible arm using a piezoactuator associated with a hysteresis compensator

In this work, position control of a one-link flexible arm is undertaken by considering the field-dependent hysteresis behavior of a piezoceramic actuator (piezoactuator in short). The proposed arm is controlled by two actuators: a motor mounted at the hub and a piezoceramic bonded to the surface of the flexible link. In the modeling process, two transfer functions: one from the input torque to output hub angle and the other from the input voltage to the output tip deflection are obtained. The hysteretic behavior of the piezoactuator is experimentally identified using the Preisach model, and the first-order descending (FOD) curves are obtained that are required to design a hysteresis compensator. After establishing the overall control block diagram for the position control of the flexible arm, a quantitative feedback theory (QFT) controller is designed by treating parameter variations and external disturbances as uncertainties. Subsequently, a hysteresis compensator that produces additional control input to the piezoactuator is designed to enhance the vibration control performance. An experimental realization of the proposed control scheme is undertaken and the effect of the hysteresis compensator on vibration control of the flexible arm is evaluated in the time domain.

Control performance evaluation of railway vehicle MR suspension using fuzzy sky-ground hook control algorithm

This paper presents control performance evaluation of railway vehicle featured by semi-active suspension system using magnetorheological (MR) fluid damper. In order to achieve this goal, a nine degree of freedom of railway vehicle model, which includes car body and bogie, is established. The wheel-set data is loaded from measured value of railway vehicle. The MR damper system is incorporated with the governing equation of motion of the railway vehicle model which includes secondary suspension. To illustrate the effectiveness of the controlled MR dampers on suspension system of railway vehicle, the control law using the sky-ground hook controller is adopted. This controller takes into account for both vibration control of car body and increasing stability of bogie by adopting a weighting parameter between two performance requirements. The parameters appropriately determined by employing a fuzzy algorithm associated with two fuzzy variables: the lateral speed of the car body and the lateral performance of the bogie. Computer simulation results of control performances such as vibration control and stability analysis are presented in time and frequency domains.

Optimal Design of MR Damper : Analytical Method and Finite Element Method

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

Vibration Suppression of Hull Structure Using Macro Fiber Composite Actuators and Sensors

Dynamic modeling of smart hull structure with advanced piezoelectric actuator; macro-fiber composite (MFC) actuator, is developed and control performance to suppress structural vibration of the system is studied. Finite element technique is used to ensure application to practical geometry and boundary conditions of smart hull structure. Modal analysis is conducted to investigate the dynamic characteristics of smart hull structure. For the verification of the proposed finite element model, numerical results of modal analysis are compared with those of experimental modal test results. Modal mass and stiffness matrix of smart hull structure are extracted for the controller design. Active controller is designed to suppress structural vibration of smart hull structure and control performance is evaluated in the resonance and non-resonance regions.

Roller Design of IRB Seismic Isolation Device Using Testing Evaluation : Part I. Geometry Dimension and Crowning

This paper presents a new method for roller design of IRB(isolation roller bearing) seismic isolation device using experimental evaluation. Three layered plate is adopted for the IRB in which the upper plate is placed on x direction and the lower plate is placed on y direction. The rollers placed in each plate make a plate movement. The roller is then optimally designed using variable geometric conditions. Stress distribution depends on the diameter and length of the roller and hence this is used for the determination of optimal geometry of the roller. In the experimental evaluation, it is observed that stress concentration at the end sides of roller is decreased and geometric coefficients depend on crowning dimension. In addition, in order to determine optimal design parameters of the roller the plastic deformation and friction are experimentally identified.

Dynamic modelling and design of tracked vehicle suspension system using magnetorheological valve

This paper presents dynamic modelling and optimal design of magnetorheological fluid (MR) based suspension system for a tracked vehicle. The MR suspension unit (MRSU) is designed to combine with a gas spring. The governing equation of motion of a tracked vehicle suspension is derived and the optimisation problem to find optimal geometric dimensions of the MR valve is undertaken to improve damping force and control energy. The performance characteristics of the optimised MRSU are then evaluated and compared with initial one. In addition, vibration control performances of the tracked vehicle suspension installed with the optimised MRSU are evaluated under bump excitation.

Optimal design of a magnetorheological fluid suspension for tracked vehicle

This paper presents optimal design of controllable magnetorheological suspension system (MRSS) for a tracked vehicle. As a first step, a double-rod type MRSS is designed on the basis of the Bingham model of commercially available MR fluid, and its damping characteristics are evaluated with respect to the intensity of the magnetic field. Subsequently, the governing equation of motion of the MRSS featuring the MR valve is established Then, the optimization problem to find optimal geometric dimensions of the MRSS is formulated by considering an objective function which is related to damping torque and control energy. The first order optimization method intergrated with a commercial finite element method(FEM) software is adopted to obtain optimal solution of the system. The performance characteristics of the optimized MRSS are then evaluated and compared with initial ones.

Vibration Control of Flexible Structures Using Semi-Active Mount : Experimental Investigation

In many dynamic systems such as robot and aerospace areas, flexible structures have been extremely employed to satisfy various requirements for large scale, light weight and high speed in dynamic motion. However, these flexible structures are readily susceptible to the internal/external disturbances (or excitations). Therefore, vibration control schemes should be exerted to achieve high performance and stability of flexible structure systems. Recently, in order to successfully achieve vibration control for flexible structures smart materials such as piezoelectric materials [1-2], shape memory alloys [3-4], electrorheological (ER) fluids [5-6] and magnetorheological (MR) fluids [7] are being widely utilized. Among these smart materials, ER or MR fluid exhibits reversible changes in material characteristics when sub‐ jected to electric or magnetic field. The vibration control of flexible structures using the smart ER or MR fluid can be achieved from two different methods. The first approach is to replace conventional viscoelastic materials by the ER or MR fluid. This method is very effec‐ tive for shape control of flexible structures such as plate [5]. The second approach is to de‐ vise dampers or mounts and apply to vibration control of the flexible structures. This method is very useful to isolate vibration of large structural systems subjected to external excitations [6-7]. In this work, a new type of MR mount is proposed and applied to vibration control of the flexible structures.

Performance evaluation of 6WD military vehicle featured by MR suspension system considering lumped parameter model of MR damper

This paper proposes applies MR fluid based suspension system to military vehicle for vibration control. The suspension system consists of gas spring and MR damper. In order to model of MR damper, a quasi-static modeling of the damper is conducted on the basis of Bingham model of MR fluid after describing the configuration and operating principle of the MR damper. And then the lumped parameter models of MR fluid flows in the damper are established and integrated to whole damper system by taking into account for dynamic motions of annular duct and gas chamber. Subsequently, a military vehicle of 6WD is adopted for the integration of the MR suspension system and its nonlinear dynamic model is established by considering vertical, pitch and roll motion. Then, a sky-hook controller associated with semi-active actuating condition is designed to reduce the imposed vibration. In order to demonstrate the effectiveness of the MR suspension system, computer simulation is undertaken showing vibration control performance such as roll angle and pitch angle. This is vibration control evaluated under bump and random road profiles.