Haptic systems incorporate many different components, ranging from virtual simulations, physical robotic interfaces (super joysticks), robotic slaves, signal communication, and digital control; two-port networks offer compact and modular organization of such haptic components. By establishing specific stability properties of the individual component networks, their control parameters can be tuned independently of external components or interfacing environment. This allows the development of independent haptic two-port networks for interfacing with a class of haptic components. Furthermore, by using the two-port network with virtual coupling paradigm to analyze linear haptic systems, the complete duality between an admittance controlled device with velocity (position) feedback and virtual coupling can be compared to an impedance controlled device with force feedback and virtual coupling. This research first provides background on linear haptic two-port networks and use of Llewelyn's Stability Criterion to prove their stability when interfaced with passive environments, with specific comments regarding application of these linear techniques to nonlinear systems. Furthermore, man-machine interaction dynamics are addressed, with specific attention given to the human is a passive element assumption and how to include estimated human impedance / admittance dynamic limits into the two--port design. Two--port numerical tuning algorithms and analysis techniques are presented and lay the groundwork for testing of said haptic networks on HuRBiRT (Human Robotic Bilateral Research Tool), a large scale nonlinear hybrid active / passive haptic display. First, two-port networks are numerically tuned using a linearized dynamic model of HuRBiRT. Resulting admittance and impedance limits of the respective networks are compared to add insight on the advantages / disadvantages of the two different implementations of haptic causality for the same device, with specific consideration given to the advantage of adding force feedback to the impedance network, selection of virtual coupling form, effects of varying system parameters (such as physical or EMF damping, filters, etc.), and effects of adding human dynamic limits into the network formulation. Impedance and admittance two-port network implementations are experimentally validated on HuRBiRT, adding further practical insight into network formulation. Resulting experimental networks are directly compared to those numerically formulated through use of HuRBiRT's linearized dynamic models.

Digital Clay is a next generation human-machine communication interface based on a tangible haptic surface. This thesis embraces this revolutionary concept and seeks to give it a physical embodiment that will confirm its feasibility and enable experimentation relating to its utility and possible improvements. Per the approach adopted in work, Digital Clay could be described as a 3D monitor whose pixels can move perpendicularly to the screen to form a morphing surface. Users can view, touch and modify the shape of the working surface formed by these pixels. In reality, the pixels are the tips of micro hydraulic actuators or Hapcel (i.e. haptic cell, since the Digital Clay supports the haptic interface). The user can get a feel of the desired material properties when he/she touches the working surface. The potential applications of Digital Clay cover a wide range from computer aided engineering design to scientific research to medical diagnoses, 3D dynamic mapping and entertainment. One could predict a future in which, by using Digital Clay, not only could the user watch an actor in a movie, but also touch the face of the actor! This research starts from the review of the background of virtual reality. Then the concept and features of the proposed Digital Clay is provided. Research stages and a 5x5 cell array prototype are presented in this thesis on the structural design and control of Digital Clay. The first stage of the research focuses on the design and control of a single cell system of Digital Clay. Control issues of a single cell system constructed using conventional and off-the-shelf components are discussed first in detail followed by experimental results. Then practical designs of micro actuators and sensors are presented. The second stage of the research deals with the cell array system of Digital Clay. Practical structural design and control methods are discussed which are suitable for a 100x 100 (even 1000X 1000) cell array. Conceptual design and detailed implementations are presented. Finally, a 5 x 5 cell array prototype constructed using the discussed design solutions for testing is presented.

A formable surface is part of an effort to create a haptic device that allows for a three dimensional human-computer interface called digital clay. As with real clay, digital clay allows a user to physically manipulate the surface into some form or orientation that is sensed and directly represented in a computer model. Furthermore, digital clay will allow a user to change the computer model by manipulating the inputs that are directly represented in the physical model. The digital clay device being researched involves a computer-interfaced array of vertically displacing actuators that is bound by a formable surface. The surface is composed of an array of unit cells that are constructed of compliant spherical joints and translational joints. As part of this thesis, a series of unit cells were developed and planar surfaces were fabricated utilizing the additive manufacturing process of stereolithography. The process of computing the resultant shape of a manipulated surface was modeled mathematically through energy minimization algorithms that utilized least squares analysis to compute the positions of the unit cells of the surface. Simulation results were computed and analyzed against the movement of a fabricated planar surface. Once the mathematical models were validated against the manufactured surface, a method for attaching the surface to an array of actuators was recommended.