Jeffrey Feaster

Adaptive control for flapping wing robots with history dependent, unsteady aerodynamics

This paper derives a history dependent formulation of the equations of motion of a flapping wing, ground-based robotic system and constructs an associated adaptive control strategy to track observed flapping motions in insect flight. A general methodology is introduced in which lift and drag forces are represented in terms of history dependent integral operators to model and identify the unknown and unmeasurable aerodynamic loading on the flapping wing robot. The resulting closed loop system constitutes an abstract Volterra integral equation whose state consists of the finite-dimensional vector of generalized coordinates for the robotic system and an infinite dimensional unknown function characterizing the kernel of the history dependent integral operator. Finite dimensional approximations of the state equations are derived via quadrature formula and finite element methods. These approximations yield history dependent equations that evolve in euclidean space. An adaptive control scheme based on passivity principles is derived for the approximate history dependent system. Lyapunov analysis guarantees stability of the closed loop system and that the tracking error and its derivative converge to zero. The novel control strategy introduced in this paper is noteworthy in that by introducing a history dependent adjoint operator in the state estimate equation, the analysis for convergence of the closed loop history dependent equations closely resembles the analysis used for conventional ODE systems.

Computational Analysis of Undulatory Batoid Motion for Underwater Robotic Propulsion

Underwater fish of the class Batoidea, commonly known as rays and skates, use large cartilaginous wings to propel themselves through the water. This motion is of great interest in bioinspired robotics as an alternative propulsion mechanism. Prior research has focused primarily on the oscillating kinematics used by some species which resembles flapping; this study investigates undulatory motion induced by propagating sinusoidal waves along the fin. An analytical model of undulatory kinematics is presented and correlated with biological literature, and the model is then simulated via unsteady computational fluid dynamics and multiparticle collision dynamics. A bioinspired robot, Batoid Underwater Robotics Testbed (BURT), was developed to test the kinematics of the undulating propulsion system proposed. Finally, BURT was utilized as a platform to investigate engineering challenges in undulating Batoid robotics.Copyright

Validation of an adaptive meshing implementation of the lattice-Boltzmann method for insect flight

nsects, sustaining flight at low Reynolds numbers (500<Re<10,000), fly utilizing mechanically simple kinematics (3 degrees of freedom) at an extremely high flap frequency (150–200 Hz), resulting in a complicated vortical fluid field. These flight characteristics result in some of the most agile and maneuverable flight capabilities in the animal kingdom and are considered to be far superior to fixed wing flight, such as aircraft. Bees are of particular interest because of the utilization of humuli to attach their front and hind wings together during flight. A Cartesian-based adaptive meshing implementation of the Lattice-Boltzmann Method is utilized to resolve the complex flow field generated during insect flight and is verified against experimental and computational results present in the literature in two dimensions. The Lattice-Boltzmann Method was found to agree well in both qualitative and quantitative comparisons with both two-dimensional computational and three-dimensional experimental results.

A Methodology for the Kinematic and Unsteady Dynamics Analysis of Bat Flight

A methodology to capture and post-process bat flight 3-D Stereo Triangulation data to formulate an approximated rigid body kinematic model was investigated. Bat flight is unique in nature due to the bats inherent agility and many degrees of freedom when compared to other flying animals. This complexity makes capturing accurate aerodynamic data very difficult. Unlike insects, which utilize few degrees of freedom and a high flap frequency for sustained flight and maneuverability, the agility of bats comes in part from the many degrees of freedom present in the bat wing. In order to better understand the aerodynamics present in bat flight, bats Hipposideridae (Old World leaf-nosed bats) were examined. The trajectories of critical points along the bat wings were recorded using 3D stereo triangulation techniques to capture the complexities of the bat flight. Markers were placed at all the joint locations along the bat wing. The resulting trajectories were then translated into a periodic kinematic model for future computational use.Copyright

Unsteady Flow Analysis Strategies for Flapping Flight

A current project is underway to create a prototype of an anatomically correct seagull with biologically accurate flight kinematics. The presented work is focused on the computational fluid dynamics (CFD) analysis of bird flight kinematics. A finite volume approach, using Fluent, was used to attempt to model the kinematics of bird flight with varying degrees of freedom to analyze the lift, drag, pressure, and vortices magnitude associated with a range of flight kinematics. Dimensional analysis has been performed to analyze the effects of angle of incidence on the different sections of a seagull wing. Validated CFD analysis has been performed to identify optimal degree of freedom for generating maximum amount of lift while minimizing drag.The analysis benefitted from dynamic meshing and a user defined function to model the seagull wing, profiles of which were approximated by the S1223 airfoil. The user defined function allowed for variation of degrees of freedom to model the flight in the current bird prototype and to assess the effects of changing angles of incidence and inlet velocity on lift and drag. Difficulties were encountered when trying to accurately analyze unsteady aerodynamics over a flapping motion. The appropriate grid resolution, the user defined function, as well as the appropriate grid and dynamic mesh parameters within Fluent were all possible areas of concern. The grid resolution was determined by analyzing a steady state case and determining the variation in lift and drag values calculated by increasing the grid density. A user defined function was created that accurately represents the kinematics associated with the bird wing. A triangular grid was utilized for the dynamic mesh with re-meshing procedure activated at every iteration during the analysis. The final geometry provided an accurate method for dynamic re-meshing and overcame the problem of negative cell volume associated with re-meshing using a rectangular mesh configuration. It was determined that maximum cell volume, number of time steps, and time step interval were all important criteria when determining parameters for the unsteady flight analysis.Results indicate that the unsteady dynamics of bird flapping motion can be effectively represented with modified CFD analysis with updated finite volume scheme. Data indicates that values associated with varying angles of attack at a steady state cannot be used to model flapping flight. The paper will report on further validation to analyze the pressure, lift and drag associated with flapping flight in a three-dimensional study.Copyright