This paper studies semi-active vibration control using Fluidic Flexible Matrix Composites (F2MC) as variable stiffness structures. The apparent stiffness of F2MC tubes can be changed using a variable orifice valve. With fiber reinforcement, the volume inside the tube may change with external load. With an open valve, the liquid is free to move in or out of the tube, so the apparent stiffness will not changed. When the valve is closed, the high bulk modulus liquid is confined, which resists the volume change and causes the apparent stiffness of the tube to increase. The equations of motion of an F2MC-mass system is derived using a 3D elasticity model and the energy method. A reduced order model is then developed for fully-open or fully-closed valves. A Skyhook valve that cycles the valve between open and closed, asymptotically decays the vibration. A Zero Vibration (ZV) Stiffness Shaping technique is introduced to suppress the vibration in finite time. A sensitivity analysis of the ZV Stiffness Shaper studies the robustness to parameteric uncertainties.
This paper presents a novel Tuned Vibration Absorber (TVA) using Fluidic Flexible Matrix Composites (F2MC). Fiber reinforcement of the F2MC tube kinematically links the internal volume with axial strain. Coupling of a fluid-filled F2MC tube through a fluid port to a pressurized air accumulator can suppress primary mass forced vibration at the tuned absorber frequency. 3-D elasticity model for the tube and a lumped fluid mass develops a 4th-order model of an F2MC-mass system. The model provides a closed form isolation frequency that depends mainly on the port inertance, orifice flow coefficient, and the tube parameters. A small amount of viscous damping in the orifice increases the isolation bandwidth. With a fully closed orifice, the zero disappears and the system has a single resonant peak. Variations in the primary mass do not change the isolation frequency, making the F2MC TVA robust to mass variations. Experimental results validate the theoretical predictions in showing a tunable isolation frequency that is insensitive to primary mass variations, and a 94% reduction in forced vibration response relative to the closed-valve case.
This paper investigates semi-active vibration control using Fluidic Flexible Matrix Composites (F 2 MC) as variable stiffness components of exible structures. The stiffness of F 2 MC tubes can be dynamically switched from soft to stiff by opening and closing an on/off valve. Fiber reinforcement of the F 2 MC tube changes the internal volume when externally loaded. With an open valve, the uid in the tube is free to move in or out of the tube, so the stiffness is low. When the valve is closed, the high bulk modulus uid resists volume change and produces high stiffness. The equations of motion of an F 2 MC-mass system is derived using a 3D elasticity model and the energy method. The stability of the unforced dynamic system is proven using a Lyapunov approach. To capture the important system parameters, nondimensional full order and reduced order models are developed. A Zero Vibration (ZV) state switch technique is introduced that suppresses vibration in nite time, and is compared to conventional Skyhook semiactive control. The ITAE performance of the controllers is optimized by adjusting the open valve ow coef cient. Simulation results show that the optimal ZV controller outperforms the optimal Skyhook controller by 13% and 60% for impulse and step response, respectively. IntroductionVibration degrades the performance of many mechanical systems. The accuracy of trajectory tracking and set-point regulation is often limited by structural vibration. Vibration control is categorized as: active [1], passive [2], semi-active [3,4] or hybrid [5], based on the power consumption of the control system.Active vibration control systems normally can achieve
This paper investigates passive and semi-active vibration control using fluidic flexible matrix composites (F2MC). F2MC tubes filled with fluid and connected to an accumulator through a fixed orifice can provide damping forces in response to axial strain. If the orifice is actively controlled, the stiffness of F2MC tubes can be dynamically switched from soft to stiff by opening and closing an on/off valve. Fiber reinforcement of the F2MC tube kinematically relates the internal volume to axial strain. With an open valve, the fluid in the tube is free to move in or out of the tube, so the stiffness is low. With a closed valve, however, the high bulk modulus fluid resists volume change and produces high axial stiffness. The equations of motion of an F2MC-mass system are derived using a 3D elasticity model and the energy method. The stability of the unforced dynamic system is proven using a Lyapunov approach. A reduced-order model for operation with either a fully open or fully closed valve motivates the development of a zero vibration (ZV) controller that suppresses vibration in finite time. Coupling of a fluid-filled F2MC tube to a pressurized accumulator through a fixed orifice is shown to provide significant passive damping. The open-valve orifice size is optimized for optimal passive, skyhook, and ZV controllers by minimizing the integral time absolute error cost function. Simulation results show that the optimal open valve orifice provides a damping ratio of 0.35 compared with no damping in closed-valve case. The optimal ZV controller outperforms optimal passive and skyhook controllers by 32.9% and 34.2% for impulse and 34.7% and 60% for step response, respectively. Theoretical results are confirmed by experiments that demonstrate the improved damping provided by optimal passive control F2MC and fast transient response provided by semi-active ZV control.
Tuned vibration absorbers have been shown to reduce the forced vibration response at a specific frequency for many applications. This paper presents a novel absorber using fluidic flexible matrix composites (F2MC). Fiber reinforcement of the F2MC tube kinematically links the internal volume with axial strain so that fluid flows in and out of an axially vibrating tube. Coupling of an F2MC tube through a fluid port to a pressurized air accumulator produces a novel absorber that can suppress vibration at the tuned absorber frequency. A 3-D elasticity model for the tube and a lumped model for the fluid mass produce a fourth-order F2MC-mass model. The analytical closed-form isolation frequency is derived and shown to depend primarily on the port inertance, orifice flow coefficient, and the tube parameters. Viscous damping in the orifice can be adjusted to reduce the resonant peak and broaden the isolation bandwidth. With a fully closed orifice, the zero disappears and the system has a single resonant peak. For a constant port inertance, variations in the primary mass do not change the isolation frequency, making the F2MC absorber robust to mass variations. Experimental results validate the theoretical predictions by demonstrating a tunable isolation frequency that is insensitive to primary mass variation as well as a 94% reduction in forced vibration response relative to the closed-valve case at the isolation frequency.
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