Switched Stiffness Vibration Controllers for Fluidic Flexible Matrix Composites

Abstract

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

On the applicability of fluidic flexible matrix composite variable impedance materials for prosthetic and orthotic devices

“…However, when the valve is closed, the F 2 MC tubes are very stiff since the high bulk modulus fluid resists the volume change due to the axial loading and the fiber orientation. In addition, it has been shown that active and semi-active valve control can be effective in modulus tuning [16] and vibration suppression [17].…”

Force Tracking Control of Fluidic Flexible Matrix Composite Variable Stiffness Structures

“…Recently, the F 2 MC structures have been investigated for vibration and impedance control using simple on/off valve control. Lotfi-Gaskarimahalle and Rahn (2009) investigated the use of a zero vibration (ZV) state switch technique (open/closed-valve control) for the F 2 MC system and showed that an optimal ZV controller outperforms an optimal Skyhook controller for vibration control. While the current semi-active control method (on/off switching of valve) provides the adaptive structure with two modes of operation, i.e., soft or stiff, active control of a servovalve can significantly enhance the variability of the stiffness of the single and multicellular structures.…”