This research project is a collaborative research effort in the design and development of biologically inspired material systems having distributed sensing, actuation, and intelligent control. The goals of this research project are to achieve a greater understanding of the hierarchical organization and structure of the sensory, muscular, and control systems of fish and to develop advanced biologically-inspired material systems having distributed sensing, actuation, and intelligent control.

This research aims to identify and theoretically describe the computational processing performed at the local sensory level for muscle activation and vertebral-stiffness modulation along the tail structure of fish for locomotion. Through a series of interdisplinary engineered experiments, the research seeks to understand (a) the ability of fish to actively modulate the mechanical properties of the tail via muscle recruitment, (b) how swimming gaits are regulated by a hierarchy of control systems that involve the visual, vestibular, and neuromast sensory systems, and (c) how hydrodynamic stimuli to the lateral line neuromasts directly influence the mechanical properties of the tail. An advanced multifunctional material system having distributed actuation and sensing will be developed to serve as a platform for validation and to provide greater understanding of the biology of these systems. The new material system will utilize innovative artificial neuromasts (sensors) and muscles (actuators) that are distributed and arranged as inspired by the configuration found in fish.

Through coupling of the biological and engineering experiments of the fish and artificial material system, the interdisplinary team will work together to develop a new framework for observing, identifying, and predicting the sensorimotor behavior of fish for locomotion and stiffness modulation. This research will advance the state-of-the-art development of multifunctional materials, leading to new structures that can intelligently sense and actuate a network of distributed robust sensors and actuators. Pioneer efforts include developing an advanced material system using nanotechnology and advanced composite technology, fabricating hierarchically structured sensors, creating new tools for bio-engineering investigations, and instigating a paradigm shift in the understanding of the organization and structure of the hierarchical control fish use for sensing and maneuvering.

Structural health monitoring (SHM) is a technology of employing damage detection strategies to monitor the integrity of a structure in real time using a network of integrated sensors with advanced data acquisition, computation, and communication approaches.  Unlike many commonly known localized nondestructive approaches, such as ultrasonic, acoustic emission, eddy current, thermal field method ah, Lamb waves, or guided elastic waves, have the advantage of wave propagation over large distances with little loss of amplitude.  Thus, a significant advantage is that the sensors do not need to be located in the vicinity of the damage

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This research focuses on improving Lamb wave damage detection strategies using piezoelectric-based actuators. For example, a new beamforming algorithm using MacroFiber Composite (MFC) actuators is being developed to accurately predict the beamforming/beamsensing direction as well as decresing the main lobe width and side lobe magnitudes.

Student: Daewon Kim

Faculty: Michael Philen

A variable stiffness adaptive structure idea that has the potential to achieve orders of magnitude change in stiffness has been proposed. Such components could have potential applications in systems such as soft robotics, isolation mounts, and morphing aircraft. The new adaptive system is a multicellular structure composing many small-diameter fluidic flexible matrix composite (F²MC) tubes integrated into supporting matrix materials. The F²MC tubes are fluid-filled composite tubes where the tubes consist of multiple layers of oriented, high performance fibers such as carbon in a flexible matrix. Due to the internal fluid having a high bulk modulus (e.g. water, oil), significant changes in stiffness can be obtained by simply opening or closing an inlet valve to the F²MC cells. With an open valve, the new adaptive structure can be very flexible. On the other hand, when the valve

is closed, the fluid resists volume change due to its high bulk modulus, and because of the fiber reinforcement, the constrained F²MC structures will develop very high stiffness. In other words, the variable stiffness adaptive structure has the flexibility to easily deform when desired (open valve) and possesses the high stiffness required under loading conditions when deformation is not desired (closed valve – locked state). By actively controlling the flow and pressure in the F²MC cells by use of a variable orifice/valve and a feedback control system, the adaptive structure can achieve a desired force-displacement (stress-strain) trajectory as seen in the figure, thus possessing the unique ability to change stiffness online.

Faculty: Michael Philen

The objective of this research is to develop an autonomous underwater vehicle that can emulate the swimming behavior of a fish. This research is a collaboration with AVID LLC and Professor Waye Neu.

The artificial fish utilizes Flexible Matrix Composite (FMC) actuator technology for propulsion and control.  This innovative approach to fin actuation uses structurally integrated and distributed actuators to avoid the losses associated with conventional means of driving bioinspired propulsors, and more closely match the exceptional performance of natural swimmers.
A prototype of the artificial fish having FMC artificial muscles has been completed and tested at Virginia Tech.  A maximum thrust of 0.6 lbf with a mean thrust of 0.36 lbf has been achieved in the laboratory for a stationary fish swimming between 0.83 and 1.25 Hz frequency. Free-swimming results show that the prototype can swim at approximately 3 ft/s. 

 

Students: Zhiye Zhang, Richard Duelley, Nikolai Vozza, Sean Flemings, and Michael Weaver

Faculty : Michael Philen, Wayne Neu

The objective of this research is to evaluate the feasibility of using Flexible Matrix Composite Actuators for biomimetic propulsion of a caiman. An analytical model of the tail structure was developed using measured crocodilian waveform (Fish, 1984) combined with a hydrodynamic model for the large motion of the tail. Several other smart materials technologies were considered for the application (e.g. piezoelectric, magnetostriction, electrostrictive poymers, shape memory alloys, electroactive polymers), and it was found that none of the smart materials could satisfy all of the performance requirements (e.g. large strain, force, size, speed). Preliminary results show that the FMC actuator is a viable actuator technology for biomimetic propulsion of a caiman tail.

 

The objective of this research is to create a high performance morphing wing tip for a low-speed airfoil based on pressurized flexible matrix composites (FMCs). Specifically, we aim to develop a new novel wing tip that can bend and/or twist through use of the new material/actuation system.
One of the major ingredients of the new material system, inspired by the fibrillar network in plant cell walls, is an actuation structure based on flexible matrix composites. By tailoring the fibers (orientation, number of layers, material, etc.) and selection of matrix materials, one can achieve flexible matrix composite (FMC) structures that have an exceptionally high degree of anisotropy. By designing the fiber orientation in the wall of the FMC tube, one can cause the actuator structure to contract or elongate axially due to internal pressurization. The performance of the system (pressure, stroke, load, etc.) can also be tuned by the proper selection of FMC parameters, such as the matrix and fiber materials, number of fiber layers, and fiber orientation.

By integrating multiple FMC cells (tubes) into a continuous structural system, one can achieve an adaptive structure with multi-directional actuations. By controlling the pressure in the tubes with different sequences, one can achieve various motions of the plate, such as bending and twisting.
This objective of this research is to synthesize a novel multicellular FMC morphing wing tip for flight control where the outer wing tip consists of multiple layers of precisely oriented multicellular FMC active skins to create the high performance morphing wing tip.

Student: Tyler Hinshaw (M.S. Graduate)