Browsing by Author "Pecht, M."

Now showing 1 - 17 of 17
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    An Approach for Building a Rule-Based System for Design Optimization.
    (1986) Azarm, Shapour; Pecht, M.; ISR
    A strategy for design optimization for nonlinearly constrained problems is presented. The strategy combines techniques used in production rule systems with an optimization procedure dealing with local monotonicity and sequential quadratic programming techniques. The rule system is based on observations obtained by applying the optimization procedure to different classes of test problems. The observations made may be incorporated in a rule- based system in such a way that if its premise is true, then the action part of the rule is concluded. This is the first step at developing such a rule-based system for design optimization.
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    An Approach for Building a Rule-Based System for Design Optimization.
    (1985) Azarm, Shapour; Pecht, M.; ISR
    A strategy for design optimization of nonlinearly constrained problems is presented. The strategy combines techniques used in production rule systems with an optimization procedure dealing with local monotonicity and sequential quadratic programming techniques. The rule system is based on observations obtained by applying the optimization procedure to different classes of test problems. The observations made may be incorporated in a rule- based system in such a way that if its premise is true, then the action part of the rule is concluded. This is the first step at developing such a rule-based system for design optimization.
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    Component Placement on PWB's for Routability and Reliability.
    (1987) Osterman, M.D.; Pecht, M.; ISR
    The placement of components on a printed wiring board (PWB) affects reliability, manufacturability, maintainability, and cost. In the past, placement techniques have been developed solely on the basis of minimizing the total wirelength necessary for the complete interconnection of the components. This paper presents techniques to improve placement based on reliability as well as routability. The approach discusses an innovative coupled force-directed methodology.
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    Computer Aided Design for PCB Reliability.
    (1987) Pecht, M.; ISR
    Sophisticated computer tools and techniques have been developed to increase the productivity of the digital electronics design and analysis process. Computer aided design (CAD) tools presently exist for schematic capture, routing, electrical simulation, and reliability prediction. This paper discusses some of the design, analysis and prediction issues, methodologies and critical tasks for up-front computer-aided design for reliability of digital electronics.
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    A Computer Aided Engineering Program for Coplanar and In-Line Printed Wiring Board Thermal and Thermal Reliability Analysis.
    (1985) Pecht, M.; Palmer, M.; ISR
    This report is a review of the cooperative: Westinghouse University of Maryland, Mechanical Engineering, computer-aided design (CAD) of a printed wiring board (PWB) project. In earlier cooperation (1984) with Westinghouse, an interface link was developed between the computer-aided PWB layout and routing routine (RECAL-REDAC) and a thermal analysis routine. A CAD program, called MTEMP resulted, which performs a thermal analysis for in-line PWB's without the requirements of "hand" scaling and node shifting used by previous programs, eliminates much of the I/O by providing a direct link with REDAC, and provides an accurate graphical model of the PWB. Finally, to control development cost and conform to copyrights, MTEMP does not alter REDAC. Our research effort over the 1985 year consisted of developing a coplanar thermal analysis program , a thermal reliability analysis program which was integrated into a user friendly printed wiring board design program. In addition heat dissipation input for each component can now be manually entered or can be accessed from the working database. A component database shell was developed that will aid in the thermal , reliability analysis , can be called from any routine as needed. This solves one of the past limitations in that there was no reference from the PWB components to the actual part numbers.
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    Database and Process Control for RAMCAD.
    (1987) Sawyer, B.T.; Pecht, M.; ISR
    After three years of development, the University of Maryland Reliability and Maintainability Computer Aided Design (RAMCAD) expert system for electronics has been implemented for on-site test and utilization by Westinghouse Defense Electronics in the design of the electronics for the Airborne Self Protection Jammer (ASPJ). This paper focuses on the database and system controller.
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    Design for Reliability of Printed Circuit Boards.
    (1987) Pecht, M.; Sawyer, B.T.; Naft, J.; ISR
    A well designed product satisfies performance requirements and optimizes between reliability, producibility, supportability and cost criteria. In the design of electronics, these design criteria originate from a variety of disciplines. Electrical criteria include meeting signal distribution, power distribution, board I/O, and grounding rules, reducing crosstalk, and minimizing routing track lengths to meet speed and transmission line specifications. Environmental criteria include meeting environmental derating limits. Mechanical criteria involve designing for durability under vibrational and thermalmechanical loading. Manufacturing criteria include meeting geometric constraints for quality control, and providing acceptable assembly conditions.
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    An Expert System for Electronics Design.
    (1987) Sawyer, B.T.; Pecht, M.; ISR
    After three years of development, the University of Maryland Reliability and Maintainability Computer Aided Design (RAMCAD) expert system for electronics has been implemented for on-site test and utilization. This paper discusses the operation of the RAMCAD system, the structure of the system controller, and the impact of RAMCAD on established industrial design practices.
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    Indirective Random Optimal Component Placement.
    (1986) Wong, Y.T.; Palmer, M.; Pecht, M.; ISR
    Presented is a new efficient method for the placement of components on a printed wiring board (PWB). In order to obtain shortest total wire length, all nets are considered as randomly connected minimum Steiner trees. A random optimal net process theory is used to eliminate redundant comparison and an indirective optimal technique is used to avoid calculating the exact length of minimum Steiner trees in the iterative process.
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    Injection Molding Process Control - A Review.
    (1986) Agrawal, Rakesh; Pandelidis, I.O.; Pecht, M.; ISR
    This paper reviews control strategies employed in the injection molding process. For clarity, the controlled variables have been categorized into all phase control, phase-dependent control and cycle to cycle control. All phase control includes variables which must be monitored and controlled at all times i.e. in all the phases. Control of variables which are triggered during a specific phase are discussed under phase dependent control. In cycle to cycle control, use is made of the previous data in order to predict future trends and take corrective actions thereof. The cyclic, dynamic and unsteady state nature of the injection molding process has been discussed with respect to the conventional PI and PID controllers as well as the more advanced control schemes such as self-tuning control, optimal control, and statistical process control. Suggestions involving specific advanced control schemes and recommendations for-future research in injection molding process control have also been made.
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    PCB Design for Thermal Reliability.
    (1987) Pecht, M.; Sawyer, B.T.; ISR
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    Placement of Integrated Circuits for Reliability on Conductively Cooled Printed Wiring Boards.
    (1987) Osterman, M.D.; Pecht, M.; ISR
    This article presents a mathematical theory for component placement for reliability based on the thermal response of conductively cooled printed wiring board. Placement procedures based on the theory are then developed and a general placement methodology is discussed.
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    Random Optimal Net Oriented PWB Design Automation.
    (1986) Wong, Y.T.; Pecht, M.; Palmer, M.; ISR
    Presented is a new automated design approach for the net initial assignment, placement and routing of components on a printed wiring board (PWB). In order to obtain shortest total wire length, all nets under consideration are randomly connected as minimum Steiner trees in every process. The random optimal net process theory is used to eliminate redundant comparisons and the indirective optimal technique is wed to avoid calculating the exact length of minimum Steiner trees in the iterative process. Thus complex PWBs can be designed more efficiently. In the routing process, a modified Lee's algorithm is used to build the minimum spanning trees related to the minimum Steiner trees imagined in the placement process and search proper channels for the Steiner trees in terms of the minimum spanning trees.
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    Reliability Optimization Schemes for Convectively Cooled PCBs.
    (1986) Dancer, David; Pecht, M.; Paimer, M.; ISR
    This article discusses the optimum placement of a single row of convectively cooled electronic components In order to reduce failures. It is shown that this problem is analogous to the classical operations research problem of the optimum time scheduling of n jobs on a single machine, where for each job there is a time dependent completion penalty. Several optimization schemes for solving the idealized problem are compared as to their accuracy and computational speed. For the dynamic programming scheme a new compact labeling procedure is proposed.
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    Towards Intelligent Design Optimization.
    (1985) Azarm, Shapour; Pecht, M.; ISR
    A strategy for design optimization of nonlinearly constrained problems is presented. The strategy combines techniques used in production rule systems with an optimization procedure dealing with local monotonicity and with sequential quadratic programming techniques. The production rule system is based on the observations obtained by applying the optimization program to different classes of test problems. The observations made are incorporated in the rule-based system in such a way that if its premise is true, then the action part of the rule is concluded. This is the first attempt at developing such a microcomputer rule-based system for design optimization.
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    Validation of a Thermal Model Using Infrared Thermography.
    (1988) Resch, C.; Pecht, M.; ISR
    The ability to accurately calculate the temperature profile of a printed wiring board (PWB) is necessary in determining the reliability of the PWB. Calculating temperatures of electronic components on PWBs requires that models be developed and tested for their validity. Infrared thermography provides one method of measuring the temperature profile of a PWB. Using an infrared camera, a thermal "snapshot" is taken of the PWB where the colors on the suapshot represent ranges of temperatures. The temperature profile of a conductively cooled PWB is modeled using the University of Maryland RAMCAD system and validated using both infrared thermography and thermocouples. The two sets of measurements are compared and the validity of using infrared thermography to determine the accuracy of a thermal model is discussed.
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    Work station Requirements for Printed Wiring Boards.
    (1986) Pecht, M.; Naft, J.; Palmer, M.; ISR
    This article presents an overview of the requirements of workstations which are used in the design of printed wiring boards (PWBs). Weaknesses in the current usage of workstations in the design process are discussed and a solution is suggested whereby functionally specific clustered workstations are tied to an intelligent working data base to form a workstation environment tailored to the engineering design process.