• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.8 s.113
• /
• pp.822-829
• /
• 2006

This paper presents a robust and superior control performance of a quarter-vehicle electrorheological (ER) suspension system. In order to achieve this goal, a moving sliding mode control algorithm is adopted, and its moving strategy is tuned by fuzzy logic. As a first step, ER damper is designed and manufactured for a passenger vehicle suspension system, and its field-dependent damping force is experimentally evaluated. After formulating the governing equation of motion for the quarter-vehicle ER suspension system, a stable sliding surface and moving algorithm based on fuzzy logic are formulated. The fuzzy moving sliding mode controller is then constructed and experimentally implemented. Control performances of the ER suspension system are evaluated in both time and frequency domains.

• Journal of KSNVE
• /
• v.8 no.2
• /
• pp.313-323
• /
• 1998

This paper addresses a sliding mode control of vibration in a flexible structure using ER(electro-rheological) dampers. A clamped-clamped flexible structure system supported by two short columns is considered. Three ER dampers to be operated in shear mode are designed on the basis of Bingham model of the arabic gum-based ER fluid, and attached to the flexible beam structure. After deriving the governing equation of motion and associated boundary conditions, a sliding mode controller is formulated to effectively suppress the vibration of the beam structure caused by sinusoidal and random excitations. In the formulation of the controller, parameter variations such as natural frequency deviation are treated to take into account the robustness of control system. The effectiveness of the proposed control system is confirmed by both simulation and experimental results.

• Korea-Australia Rheology Journal
• /
• v.18 no.1
• /
• pp.25-30
• /
• 2006

To enhance the stability of dispersed polyaniline (PANI) particles in a silicone oil system, a nonionic surfactant was adopted, and its effect on the electrorheological (ER) performance was investigated under an applied electric field. In the presence of a nonionic surfactant, the PANI based ER fluid exhibited not only an improved sedimentation stability based on the estimated sedimentation ratio but also an enhanced maximum yield stress behavior. Furthermore, the surfactant added ER suspension was applied to an ER damper system, and its damping performance was compared with the ER suspension without a surfactant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.784-787
• /
• 2003

Electrorheological(ER) and magnetorheological(MR) fluid-based dampers are typically analyzed using Bingham-plastic shear model under quasi-steady fully developed flow conditions. A Herschel-Bulkley constitutive shear flow relationship is that the linear shear stress vs. strain rate behavior of Bingham model is replaced by a shear stress that is assumed to be proportional to a power law of shear rate. This power is called the flow behavior index. Depending on the value of the flow behavior index number, varying degrees of post-yield shear thickening or thinning behavior can be analyzed. But it is not practical to analyze the damping force in a flow mode damper using Herschel-Bulkley model because it is needed to solve a polynomial equation. A useful guide is suggested to analyze the damping force in a damper using the Herschel-Bulkley model.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.452-457
• /
• 2000

This paper presents control response of a semi-active electro-rheological(ER) suspension. After showing dynamic characteristics of the ER damper, 1/4 car model is formulated by incorporating with the time constant of the damping force. $H_{\infty}$ controller compensating mass and time constant uncertainties is then designed in order to suppress vibration level of the suspension. The control responses such as vertical acceleration are presented.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.496-500
• /
• 2000

대형 구조물의 진동제어를 위하여 MR 유체 댐퍼를 사용한 반능동 제어기법에 대하여 연구하였다. 기존에 많이 사용되고 있는 수동제어기법은 일단 제어장치를 설치한 후에는 구조물에 실제로 작용하고 있는 외부 하중의 현재 특성에 대해서 적절히 반응할 수 없다는 제한을 가지고 있으며, 이를 극복하기 위하여 연구되어온 능동제어기법은 구조물이 진동을 감소시키기 위하여 구조물에 직접적으로 가해지는 커다란 제어력을 요구하며, 이로 인해 경우에 따라서는 불안정한 상태가 유발될 수도 있다는 점이 단점으로 지적되고 있다. 최근에 Spencer 등은 반능동 제어기법을 제안하였는데, 이는 수동제어장치의 제어특성을 On-Line 으로 조절하는 방식으로서 제어 가능한 수동제어기법으로도 불리운다. 구조물의 진동제어에 필요한 제어력이, 특수한 제어기구에서 발생되는 인위적인 힘이 아니라, 적절한 구조부재에서 발생되는 자연적인 부재력이므로, 무엇보다 강인하고 신뢰할 수 있는 제어기법이며, 이때 제어장치의 구조적 특성을, 측정된 구조물의 응답에 맞추어 적절히 조절함으로써 다양한 외부하중에 대해 보다 효율적인 제어가 이루어질 수 있도록 한 방법이다. 반능동제어를 위한 제어기로서는 Variable Orifice Dampers, Friction Controllable Isolators, Variable Stiffness Devices, Electro-Rheological (ER) Fluid Damper, Magneto-Rheological(MR) Fluid Damper등이 제안되고 있으며, 본 논문에서는 반응속도가 빠르고, 적은 파워만을 요구하며, 커다란 제어력을 낼 수 있는 MR Damper를 사용하여 지진하중을 받는 구조물의 반능동 제어게 대하여 연구하였다. MR Damper의 특성이 비선형이므로 이에 적합한 Sliding Mode Fuzzy Control(SMFC)기법을 사용하였으며 이때 SMFC 의 최적 설계를 위하여 Genetic Algorithm을 적용하였다. 제안된 제어기법의 실제 적용성을 검증하기 위하여 기존이 제어결과와 비교 검토하였으며, 그 결과로부터 MR Damper를 사용한 반능동 제어기법이 구조물의 진동제어에 매우 효과적임을 확인할 수 있었다.

• Smart Structures and Systems
• /
• v.1 no.3
• /
• pp.235-256
• /
• 2005

The non-linear behaviour of electrorheological (ER) and magnetorheological (MR) dampers makes it difficult to design effective control strategies, and as a consequence a wide range of control systems have been proposed in the literature. These previous studies have not always compared the performance to equivalent passive systems, alternative control designs, or idealised active systems. As a result it is often impossible to compare the performance of different smart damper control strategies. This article provides some insight into the relative performance of two MR damper control strategies: on/off control and feedback linearisation. The performance of both strategies is benchmarked against ideal passive, semi-active and fully active damping. The study relies upon a previously developed model of an MR damper, which in this work is validated experimentally under closed-loop conditions with a broadband mechanical excitation. Two vibration isolation case studies are investigated: a single-degree-of-freedom mass-isolator, and a two-degree-of-freedom system that represents a vehicle suspension system. In both cases, a variety of broadband mechanical excitations are used and the results analysed in the frequency domain. It is shown that although on/off control is more straightforward to implement, its performance is worse than the feedback linearisation strategy, and can be extremely sensitive to the excitation conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.769-772
• /
• 1995

Most turbo machines, which operate at high speeds, such as gas turbines, jet engines, pumps, and compressors are prone to perrturbing vibrations. The best vibration control method for rotors is to eliminate destabilizing factors. Careful balancing application of "more stable" oil-lubricated bearing, such as tilting pad bearings or use of anti-swirl devices in seals, are examplse of passive vibration control methods. the use of magnetic bearing is an active control method. An obvious advantage of active control is that it provides damping (or modifies system stiffness or other parameters) only when there is a need for that, i.e., in emergency states, while not affecting the rotor normal operational conditions. Moreover, active control methods provide exact position control through on-line control. In this study, a magnetic actuator, digital contrliier using DSP, and bipolar operational power supply/amplifiers were developed to show the effectiveness of reducing robot vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent component was developed. Results presented in this dissertation will provide a well-defined technical parameters in designing magnetic damper system.er system.

• Structural Engineering and Mechanics
• /
• v.22 no.2
• /
• pp.241-262
• /
• 2006

NiTi-wire shape memory alloy (SMA) dampers, that utilize NiTi SMA wires to simultaneously damp tension, compression and torsion, was developed for structural control implementation in this study. First, eight reduced-scale NiTi-wire SMA dampers were constructed. Then tension, compression and torsion experiments using the eight reduced-scale NiTi-wire SMA dampers of different specification were done. The experimental results revealed all of the eight reduced-scale NiTi-wire SMA dampers had the ability to simultaneously supply tension-compression damping and torsion damping. Finally, mechanics analysis of the NiTi-wire SMA dampers was done based on a model of the SMA-wire restoring force and on tension-compression and torsion damping analysis. The damping analytical results were found to be similar to the damping experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1298-1302
• /
• 2000

Electrorheological(HER) and magnetorheologica(MR) fluids have a unique ability to increase the dynamic yield stress of the fluid substantially when electric or magnetic field is applied. ER and MR fluid-based dampers are typically analyzed using Bingham-plastic shear flow analysis under Quasi-steady fully developed flow conditions. An alternative perspective, supported by measurements reported in the literature, is to allow for post-yield shear thinning and shear thickening. To model these, the constant post-yield plastic viscosity in Bingham model can be replaced with a power-law model dependent on shear strain rate that is known as the Herschel-Bulkley fluid model. The objective of this paper is to predict the damping forces analytically in a typical ER bypass damper for variable electric field, or yield stress using Herschel-Bulkley analysis.