J. Melli-Huber’s research while affiliated with Princeton University and other places

This paper is concerned with modeling the dynamics of N articulated solid bodies submerged in an ideal fluid. The model is used to analyze the locomotion of aquatic animals due to the coupling between their shape changes and the fluid dynamics in their environment. The equations of motion are obtained by making use of a two-stage reduction process which leads to significant mathematical and computational simplifications. The first reduction exploits particle relabeling symmetry: that is, the symmetry associated with the conservation of circulation for ideal, incompressible fluids. As a result, the equations of motion for the submerged solid bodies can be formulated without explicitly incorporating the fluid variables. This reduction by the fluid variables is a key difference with earlier methods, and it is appropriate since one is mainly interested in the location of the bodies, not the fluid particles. The second reduction is associated with the invariance of the dynamics under superimposed rigid motions. This invariance corresponds to the conservation of total momentum of the solid-fluid system. Due to this symmetry, the net locomotion of the solid system is realized as the sum of geometric and dynamic phases over the shape space consisting of allowable relative motions, or deformations, of the solids. In particular, reconstruction equations that govern the net locomotion at zero momentum, that is, the geometric phases, are obtained. As an illustrative example, a planar three-link mechanism is shown to propel and steer itself at zero momentum by periodically changing its shape. Two solutions are presented: one corresponds to a hydrodynamically decoupled mechanism and one is based on accurately computing the added inertias using a boundary element method. The hydrodynamically decoupled model produces smaller net motion than the more accurate model, indicating that it is important to consider the hydrodynamic interaction of the links.

Force-feedback mechanisms have been designed to simplify and enhance the human-vehicle interface. The increase in secondary controls within vehicle cockpits has created a desire for a simpler, more efficient human-vehicle interface. By consolidating various controls into a single, haptic feedback control device, information can be transmitted to the operator, without requiring the driver's visual attention. In this paper Electro-Rheological Fluids (ERF) based actuated mechanisms are presented that provide haptic feedback ERFs are liquids that respond mechanically to electric fields by changing their properties, such as viscosity and shear stress electroactively. Using the electrically controlled rheological properties of ERFs, we developed haptic devices that can resist human operator forces in a controlled and tunable fashion. The design of two types of ERF-based actuators and joystick is presented in detail. Their analytical model is derived, parametric analysis is performed, and experimental systems and data are presented.

Biomimetic systems attempt to copy the form or the behavior of biological systems to create efficient machines and processes. Since nature has had millions upon millions of years to perfect these systems it is logical to learn from these systems when designing machines and processes. Another way to use the tools that nature has built is to design machines that specifically incorporate a human into the system. These biologically-incorporated systems extend the capabilities of machines by adding a human component or extend the abilities of humans with the assistance of man-made devices.