Rice Wireless

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https://hdl.handle.net/1911/21945

Formerly the Center for Multimedia Communications, Rice Wireless is part of the university's Electrical and Computer Engineering Department. More information about the group can be found at http://wireless.rice.edu/.

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Laboratory Workstations in Electrical Engineering
(IBM, 1985-06-01) Aneshansley, Daniel J.; Pottle, Christopher; Cavallaro, Joseph R.; Center for Multimedia Communication
Computers, configured for data acquisition and control, have been used in undergraduate laboratories at Cornell University's School of Electrical Engineering since the early 1970s. The introduction of personal computers in the introductory laboratory course sequence (Fall/Spring of Junior Year) has permitted a dramatic expansion of this practice. Previously, computers were used in group experiments with limited student interaction. Now each student has access to an IBM Personal Computer with analog and digital input/output capabilities as well as the usual electronic instruments. Instructionally, data acquisition is emphasized during the fall semester. BASIC commands and programs are implemented to exercise analog-to-digital and digital-to-analog converters. A "canned" program collects samples (to 20,000 samples/sec) and performs spectral analysis (FFT) on periodic waveforms including the exciting current of a transformer. Three experiments in the spring semester demonstrate the capabilities of the laboratory workstation. (1) The spectral analysis program is used to demonstrate aliasing and examine distortion in a class-B amplifier. (2) A computer controlled experiment determines the impurity profiles of p-n junctions by sampling the capacitance as a function of reverse bias. (3) Filter circuits are tested automatically for transient and frequency response using the computer. Numerical integration, FFT, and inverse FFT are used to simulate circuit responses.
CORDIC Arithmetic for an SVD Processor
(The Computer Society of the IEEE, 1987-05-01) Cavallaro, Joseph R.; Luk, Franklin T.; Center for Multimedia Communication
Arithmetic issues in the calculation of the Singular Value Decomposition (SVD) are discussed. Traditional algorithms using hardware division and square root are replaced with the special purpose CORDIC algorithms for computing vector rotations and inverse tangents. The CORDIC 2 x 2 SVD processor can be twice as fast as one assembled from traditional hardware units. A prototype VLSI implementation of a CORDIC SVD processor array is planned for use in real-time signal processing applications.
CORDIC Arithmetic for an SVD Processor
(1988-06-20) Cavallaro, Joseph R.; Luk, Franklin T.; Center for Multimedia Communications (http://cmc.rice.edu/)
Arithmetic issues in the calculation of the Singular Value Decomposition (SVD) are discussed. Traditional algorithms using hardware division and square root are replaced with the special purpose CORDIC algorithms for computing vector rotations and inverse tangents. The CORDIC 2 x 2 SVD processor can be twice as fast as one assembled from traditional hardware units. A prototype VLSI implementation of a CORDIC SVD processor array is planned for use in real-time signal processing applications.
Floating-Point CORDIC for Matrix Computations
(IEEE Computer Society Press, 1988-10-01) Cavallaro, Joseph R.; Luk, Franklin T.; Center for Multimedia Communication
The CORDIC algorithms provide a VLSI hardware technique for computing the inverse tangents and vector rotations needed by many matrix decomposition algorithms. Although normally stated for fixed-point arithmetic, the CORDIC algorithms may be performed in floating-point arithmetic. A novel simplified CORDIC processor composed of floating-point data paths with a fixed-point angle calculation is proposed. This hybrid processor allows sufficient accuracy for matrix computations.
Fault-Tolerant VLSI Processor Array for the SVD
(IEEE Computer Society Press, 1989-10-01) Cavallaro, Joseph R.; Near, Christopher D.; Uyar, M. Umit; Center for Multimedia Communication
Dynamic reconfiguration techniques are presented for a two-dimensional systolic array for the SVD of a matrix. Extra computation time is not required, since idle time inherent in the array is exploited. The scheme does not require additional spare processors and is easily implemented in VLSI. Only minor hardware and communication time increases within each processing element are required.
Parallel VLSI Architectures for Real-Time Control of Redundant Robots
(ANS, 1991-02-01) Walker, Ian D.; Cavallaro, Joseph R.; Center for Multimedia Communication
We present new architectures for the efficient computation of redundant manipulator inverse kinematics. A key component of our architecture is the calculation in VLSI hardware of the Singular Value Decomposition of the manipulator Jacobian. By calculating the core of the problem in hardware, we can make full use of the redundancy by implementing more complex self-motion algorithms. Application-specific (subtask dependent) portions of the inverse kinematics are handled in parallel by an array of programmable Digital Signal Processing chips, which interface with the custom hardware and the host machine. Whole our application utilizes the range of Texas Instruments TMS series DSP chips applied to our 8 degree of freedom arm, the architecture and algorithm development is valid for general redundant manipulators and a wide range of processors currently available and under development commercially.
New Real-Time Robot Motion Algorithms Using Parallel VLSI Architectures
(SIAM, 1991-03-01) Deo, Arati S.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Real time robot control presents a major numerical challenge. The inverse kinematics problem of determining joint motion for a specified end effector trajectory is formulated as a damped least-squares problem which balances accuracy against feasibility. This approach leads to the Singularity Robust Inverse which yields feasible joint motions even at or in the neighborhood of undesirable singular configurations. We present a new technique that optimally approximates the desired end-effector trajectory with physically realizable joint velocities at all manipulator configurations. This technique uses the Levenberg-Marquardt algorithm to compute an optimal damping factor. the Singular Value Decomposition (SVD) of the manipulator Jacobian plays a key role in this algorithm which is computationally intensive and currently limited to off-line planning. This new algorithm will be run on a parallel VLSI architecture under development at Rice. This system includes a custom CORDIC VLSI array for computing the SVD of a matrix. The array is connected to a linear array of Texas Instruments TMS320C30 DSP processors. The DSP array computes many of the matrix operations in parallel and uses the CORDIC SVD array as a co-processor.
Fault Detection and Fault Tolerance in Robotics
(1991-07-01) Visinsky, Monica L.; Walker, Ian D.; Cavallaro, Joseph R.; Center for Multimedia Communication
Robots are used in inaccessible or hazardous environments in order to alleviate some of the time, cost and risk involved in preparing men to endure these conditions. In order to perform their expected tasks, the robots are often quite complex, thus increasing their potential for failures. If men must be sent into these environments to repair each component failure in the robot, the advantages of using the robot are quickly lost. Fault tolerant robots are needed which can effectively cope with failures and continue their tasks until repairs can be realistically scheduled. Before fault tolerant capabilities can be created, methods of detecting and pinpointing failures must be perfected. This paper develops a basic fault tree analysis of a robot in order to obtain a better understanding of where failures can occur and how they contribute to other failures in the robot. The resulting failure flow chart can also be used to analyze the resiliency of the robot in the presence of specific faults. By simulating robot failures and fault detection schemes, the problems involved in detecting failures for robots are explored in more depth. Future work will extend the analyses done in this paper to enhance Trick, a robotic simulation testbed, with fault tolerant capabilities in an expert system package.
Expert System Framework for Fault Detection and Fault Tolerance in Robotics
(ASME, 1992-11-01) Visinsky, Monica L.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Fault tolerance is of increasing importance for modern autonomous industrial robots. The ability to detect and tolerate failures will enable robots to effectively cope with internal failures and continue performing assigned tasks without the need for immediate human intervention. To monitor fault tolerance actions performed by lower level routines and to provide higher level information about a robot's recovery capabilities, we use an expert system to develop a novel fault tolerance framework combining fault detection and tolerance routines with dynamic fault tree analysis. Fault tree analysis reveals the key components for providing fault detection and tolerance within a system. The trees can also be used quantitatively to provide a dynamic estimate of the probability of failure of the entire system or various subsystems. Using fault trees as a standard framework, the expert system package can provide fault tolerance for robots of significantly different origin and structure.
Dynamic Fault Reconfigurable Intelligent Control Architectures for Robotics
(American Nuclear Society, 1993-04-01) Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
In this paper we describe new progress in our development of an Intelligent Control Framework for robots which dynamically reconfigures itself to cope with faults in either sensors or joint hardware. The Framework is configured to allow the incorporation of new approaches for on-line critiquing of user plans and commands within the framework. We discuss integration of the two components above to produce an Intelligent Robot Operating System which can tolerate failures or unexpected actions from both the logical (user) world and the physical (manipulator) world and continue operation where possible.
Robotic Fault Tolerance: Algorithms and Architectures
(Prentice Hall, Englewood Cliffs, NJ, 1993-04-01) Visinsky, Monica L.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Fault tolerance is an essential factor in ensuring successful autonomous systems, especially for robots working in remote or hazardous environments. To avoid the cost and risk involved in sending humans into these environs and improve the chances of mission success, robots must be able to quickly detect and recover from internal failures without relying on immediate repairs or human intervention. In developing robotic fault tolerance algorithms, the possible failures within the robot and the interdependence of these failures must first be determined. One useful tool for performing these tasks is Fault Tree Analysis. The tree structures developed by this technique provide a flow chart of possible robot fault events and define the cause and effect relationships between the failures.
Parallel VLSI Architectures for Real-Time Kinematics of Redundant Robots
(IEEE Computer Society Press, 1993-05-01) Walker, Ian D.; Cavallaro, Joseph R.; Center for Multimedia Communication
We describe new architectures for the efficient computation of redundant manipulator kinematics (direct and inverse). By calculating the core of the problem in hardware, we can make full use of the redundancy by implementing more complex self-motion algorithms. A key component of our architecture is the calculation in VLSI hardware of the Singular Value Decomposition of the manipulator Jacobian. Recent advances in VLSI have allowed the mapping of complex algorithms to hardware using systolic arrays with advanced computer arithmetic algorithms. We use CORDIC arithmetic in the novel design of our special-purpose VLSI array, which is used in computation of the Direct Kinematics Solution (DKS), the manipulator Jacobian, as well as the Jacobian Pseudoinverse. Application-specific (subtask-dependent) portions of the inverse kinematics are handled in parallel by a DSP processor which interfaces with the custom hardware and the host machine. The architecture and algorithm development is valid for general redundant manipulators and a wide range of processors currently available and under development commercially.
Layered Dynamic Fault Detection and Tolerance for Robots
(IEEE Computer Society Press, 1993-05-01) Visinsky, Monica L.; Walker, Ian D.; Cavallaro, Joseph R.; Center for Multimedia Communication
Fault tolerance is increasingly important for space and hazardous environment robotics. Robots need to quickly detect and tolerate internal failures in order to continue performing their tasks without the need for immediate human intervention. Using analytical redundancy, this paper derives tests with which the robot can detect failures. The paper also develops a layered intelligent control framework containing these new sensor-based fault detection and tolerance schemes. the servo, interface, and supervisor layers form a hierarchy of fault tolerance which provide different levels of detection and tolerance capabilities for structurally diverse robots.
Dynamic Senor-Based Fault Detection for Robots
(SPIE - The International Society for Optical Engineering, 1993-09-01) Visinsky, Monica L.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Fault detection and fault tolerance are increasingly important for robots in space or hazardous environments due to the dangerous and often inaccessible nature of these environs. We have previously developed algorithms to enable robots to autonomously cope with failures or critical sensors and motors. Typically, the detection thresholds used in such algorithms to mask out model and sensor errors are empirically determined and are based on a specific robot trajectory. We have noted, however, that the effect of model and sensor inaccuracy fluctuates dynamically as the robot and as failures occur. The thresholds, therefore, need to be more dynamic and respond to the changes in the robot system so as to maintain an optimal bound for sensing real failures in the system versus misalignment due to modeling errors. In this paper, we analyze the Reachable Measurement Intervals method of computing dynamic thresholds and explore its applicability to robotic fault detection.
Simulation of Systolic Arrays On The Connection Machine
(1993-09-20) Hemkumar, Nariankadu D.; Cavallaro, Joseph R.; Center for Multimedia Communications (http://cmc.rice.edu/)
The use of a programming model which extends naturally from the underlying hardware, greatly eases the design and implementation of simulators, especially for those systems that resemble the hardware in the paradigm of computation. Given the characteristics of systolic arrays, SIMS computers which employ the data parallel programming model provide an ideal environment. In this paper, we present a systolic array simulator, a simulation tool written for the Connection Machine (model CM2), a SIMD machine with powerful interproccessor communication capabilities. Especially as recent advances have automated the design, there is a need for a verification environment to prototype systolic arrays. Primarily a simulation tool, the systolic array simulator also helps identify inefficiencies and motivates optimal design proir to implementation in either custom VLSI or DSP systems. Currently, we are updating the tool to allow the simulation of dynamic array reconfiguration algorithms under transient and permanent fault conditions. The simulator is also being ported the CM5.
Finite element analysis of the use of temperature feedback for control of laser coagulation in biological tissue
(1994) Glenn, Tami Neal; Tittel, Frank K.
Study of thermal damage processes in laser irradiated tissue can provide further insight into the determination of optimal coagulation procedures. Arrhenius rate thermal damage processes are sensitive to tissue damage coefficients, tissue optical properties, and laser parameters. A specific isotherm appears to be associated with damage front position. Issues of coagulation control were considered by simulating a controlled surface temperature irradiation using thermal feedback to execute an appropriate temporal profile for laser power. A non-uniform pulse sequence achieves a 'constant' surface temperature. When operating the controlled temperature laser subject to convective boundary conditions, the surface temperature reference may need to be lowered to minimize subsurface heating effects. 'Constant' surface temperature irradiation avoids high temperature effects and substantial surface injury, achieves relatively slow, steady progression of damage, allowing potential real-time monitoring and control of coagulation front position, and is less sensitive to temperature dependent properties.
Expert System Framework for Fault Detection and Fault Tolerance in Robotics
(Elsevier Science Ltd, 1994-01-01) Visinsky, Monica L.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Fault tolerance is of increasing importance for modern robots. The ability to detect and tolerate failures enables robots to effectively cope with internal failures and continue performing assigned tasks without the need for immediate human intervention. To monitor fault tolerance actions performed by lower level routines and to provide higher level information about a robot's recovery capabilities, we present an expert system and critic which together form a novel and intelligent fault tolerance framework integrating fault detection and tolerance routines with dynamic fault tree analysis. A higher level, operating system inspired critic layer provides a buffer between robot fault tolerant operations and the user. The expert system gives the framework the modularity and flexibility to quickly convert between a variety of robot structures and tasks. It also provides a standard interface to the fault detection and tolerance software and a more intelligent means of monitoring the progress of failure and recovery throughout the robot system. The expert system further allows for prioritization of tasks so that the components essential to fault detection and tolerance within a system and detail the interconnection between failures in the system. The trees are also used quantitatively to provide a dynamic estimate of the probability of failure of the entire system or various subsystems.
Enhanced VLSI Manufacturability Using an Integrated CAD Framework
(SME Press, 1994-01-01) Fossati, Humberto M.; Tittel, Frank K.; Wilson, William L.; Cavallaro, Joseph R.; Center for Multimedia Communication
Continued improvements in VLSI performance, circuit density and production costs are possible, in part, do to significant advances in lithography. As feature sizes get smaller, design houses are faced with either improving the resolution of their optical lithography lines, or step-up to the cost of newer x-ray based machines. The work at Rice University proposes to integrate design and process-specific CAD tools to provide further use of optical lithography equipment, while reducing feature sizes to improve manufacturability. By integrating photolithography simulators to layout editors, and by providing expert information on the simulated optical and physical resolution of the feature to the designer, compact and smaller circuits can be designated, which are governed by local design rules. This work is complemented by the development of a novel phase shifting technique at Rice based on interferometry which allows for the manufacture of features with high contrast and reduced feature size.
A New Phase Shifting Method for High Resolution Microlithography
(SME Press, 1994-01-01) Kido, Motoi; Cavallaro, Joseph R.; Szabo, Gabor; Wilson, William L.; Tittel, Frank K.; Center for Multimedia Communication
One of the most promising lithographic technique for the future designs of DRAMs is the phase-shifting mask technique. Conventional phase shifting-masks, however, are difficult to fabricate as they require regions of different optical thickness. We present a new phase shifting technique that does not use any phase shifting materials. A special interferometer and a mask that has both transmitting areas and reflective areas accomplish the required phase-shift at the image plane. Using this technique we have demonstrated phase shifting effects using a CCD camera. We also present the results of a computer simulation for the critical resolution of this new method in comparison with the conventional phase shifting approach.
Robot Fault Detection and Fault Tolerance: A Survey
(Elsevier Science Limited, 1994-01-01) Visinsky, Monica L.; Cavallaro, Joseph R.; Walker, Ian D.; Center for Multimedia Communication
Fault tolerance is increasingly important for robots, especially those in remote or hazardous environments. Robots need the ability to effectively detect and tolerate internal failures in order to continue performing their tasks without the need for immediate human intervention. Recently, there has been a surge of interest in robot fault tolerance, and the subject has been investigated from a number of points of view. Ongoing research performs off-line and on-line failure analyses of robotic systems, develops fault-tolerant control environments, and derives fault detection and error recovery techniques using hardware, kinematic, or functional redundancy. This paper presents a summary of the current, limited, state-of-the-art in fault-tolerant robotics and offers some future possibilities for the field.

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