Institute for Systems Research

An important feature of the facility we describe is that it uses severaltypes of sensing modalities including position sensing, tactile sensingand more conventional vision sensing. It can interact with objectsof different complexity and is subject to communication constraints arising in a completelynatural and generic way. In constructing it we have used off-the-shelfcomponents wherever possible and made choices with an eye towardflexibility and reliability.

In this work we report on experimentalresults obtained with a deformable tactile sensor whose properties arewell-suited to manipulation. The results presented here show that thesensor described provides a rich set of tactile data.

In order to conceal errors occurring under bad channel conditions, a novel slicing method and a joint source channel coding scenario that combines RCPC with CRC and utilizes the distortion information to allocate convolutional coding rates are proposed. A new performance index based on JND is proposed and used to evaluate the overall performance at different signal-to-noise ratios (SNR). Our system uses OQPSK modulation scheme.

We propose a new classification scheme, dubbed spectral classification, which uses the spectral characteristics of the image blocks to classify them into one of a finite number of classes. The spectral classifier is used in adaptive image coding based on the discrete wavelet transform and shown to outperform gain-based classifiers while requiring a lower computational complexity. The resulting image coding system provides one of the best available rate-distortion performances in the literature. Also, we introduce a family of multiresolution image coding systems with different constraints on the complexity. For the class of rate-scalable image coding systems, we address the problem of progressive transmission and propose a method for fast reconstruction of a subband-decomposed progressively transmitted image.

Another important problem studied in this dissertation is the transmission of images over noisy channels, especially for the wireless channels in which the characteristics of the channel is time-varying. We propose an adaptive rate allocation scheme to optimally choose the rates of the source coder and channel coder pair in a tandem source-channel coding framework. Also, we suggest two adaptive coding systems for quantization and transmission over a finite-state channel using a combined source and channel coding scheme. Finally, we develop simple table- lookup encoders to reduce the complexity of channel-optimized quantizers while providing a slightly inferior performance. We propose the use of lookup tables for transcoding in heterogeneous networks

Using a systems engineering approach, a computer-based surface integrity assessment methodology is formulated. It combines the most recently developed image processing technology with computer graphics while incorporating the principles of fracture mechanics. Microhardness testing is used to study material properties related to machining. Four types of material selected are human enamel, Dicor-MGC, HCC Dentine, and HCC Enamel. Three- dimensional visualization of the surface impressions is achieved using an environmental scanning electron microscope and an atomic force microscope. Machining experiments are conducted to study the surface integrity, including surface finish, micro- cracking, and edge chipping. Analytical investigation correlates these surface responses to the machining parameters, such as spindle speed, feed rate, and the depth of cut, to seek a parametric region in which quality of machined ceramic components can be ensured. Surface integrity performance indices such as surface roughness, cavity density, and chip aspect ratio are proposed to quantify such evaluations.

Major contributions of this thesis research include the development of the combined SEM- AFM stereophotography method. The high resolution achieved with this method ensures coverage of rich information on the surface texture formed during machining. Specific findings of this thesis research include the identification of micro-mechanics of fracture occurred during the material removal process, and a good understanding of possible influences of the microstructures on the machining performance.