This paper presents an algorithm for solving the complex and critical problem of bending sequence... more This paper presents an algorithm for solving the complex and critical problem of bending sequence in sheet metal manufacturing. Finding the bending sequence and required tool assignment presents a large combinatorial problem which is impossible to solve optimally for practical applications within a reasonable period of time. The paper presents a two-stage algorithm. The first stage finds a feasible solution based upon collision avoidance heuristics. The second stage rapidly seeks an alternative feasible sequence with a lower cost without exceeding time limitations. The algorithm is very practical because it reaches a low-cost solution quickly within computer memory limitations. In this paper, the problem is defined, the approach is presented formally, and finally, the power of the algorithm is demonstrated by solving bending sequences for real products.
2008 IEEE International Conference on Networking, Sensing and Control, 2008
ABSTRACT Behavior permissiveness is the most important criterion in evaluating the performance of... more ABSTRACT Behavior permissiveness is the most important criterion in evaluating the performance of a liveness-enforcing supervisor. For a class of Petri nets, S3PR, this paper explores a sufficient condition under which there exists a maximally permissive monitor-based liveness-enforcing Petri net supervisor. It can be computed in an iterative way. At each iteration, a siphon is derived by the MlP-based deadlock detection method and controlled with its control depth variable being unit. We conclude that, for any S3PR structure N, there exists an initial marking Mo such that a maximally permissive liveness- enforcing supervisor can be always found for (N, M0). The results obtained in this research are fully based on elementary siphons that are developed in our previous work. A flexible manufacturing example is used to demonstrate the proposed methodology.
2008 IEEE International Conference on Networking, Sensing and Control, 2008
ABSTRACT A deadlock prevention policy is proposed for a class of Petri nets with uncontrollable t... more ABSTRACT A deadlock prevention policy is proposed for a class of Petri nets with uncontrollable transitions. It consists of two stages: siphon control and control-induced siphon control. At first stage, a monitor or control place is added for each elementary siphon such that it can never be unmarked. Due to the addition of monitors, new control-induced siphons are possibly generated in the augmented net. The second stage ensures that monitors are added to make always marked control-induced siphons without generating new control-induced siphons. The major difference of the proposed policy is that at each step the existence of uncontrollable transitions in a plant net model is considered. The results obtained in this paper show that elementary siphon based deadlock control policies are much more promising than those in the literature, particularly in coping with large-szied models. A flexible manufacturing example is utilized to illustrate the methods proposed.
ABSTRACT Although Mixed-Model assembly lines have a number of advantages over Single-Model lines,... more ABSTRACT Although Mixed-Model assembly lines have a number of advantages over Single-Model lines, they suffer from several drawbacks, such as increased assembly complexity and greater work flow fluctuations, mainly due to the differences between the models assembled in the line. This research has adopted a new approach to cope with the above disadvantages in which the models are clustered into several assembly lines. The research presents a Model Partitioning and Clustering Algorithm (MPCA), which determines the similarity between models and assigns them accordingly to different parallel assembly lines. Empirical analysis shows that the MPCA can find a better solution than the optimal solution for one Mixed-Model line, which assembles all the models simultaneously.
The paper considers the problem of simultaneous identification and trajectory tracking of moving ... more The paper considers the problem of simultaneous identification and trajectory tracking of moving objects (either 2D or 3D) from moving sensors. The identification is parametric and is based on knowing the family that the object belongs to, e.g. ball, ellipsoid, box, etc. The mathematical formulation results in implicit measurements, i.e. an algebraic equation that includes both state variables and actual measurements. The method of solution is via Extended Kalman Filter where the unknown parameters are regarded as additional state variables. Standard Extended Kalman Filter and Iterative Extended Kalman Filter yielded unsatisfactory results, mainly due to the nonlinearity of the measurements in both the state vector and the noise. A new algorithm, called Noise Updated Iterative Extended Kalman Filter is suggested. Its deviation from the standard iterative Kalman filter is in estimating the measurement noise at each iteration. The estimated noise is then used in the linearization stag...
Innovation in Life Cycle Engineering and Sustainable Development
ABSTRACT Cultural and public attitudes as well as new business approaches and life cycle concepts... more ABSTRACT Cultural and public attitudes as well as new business approaches and life cycle concepts have impacted and will continue to impact not only matters of consumption and use but indeed almost every aspect of the product life cycle. Ecological awareness, globalization and excess manufacturing capacity along with intensive competition are the main factors that have led to what is no less than a revolution in design and manufacturing. This revolution is enabled by improved information technology. This paper explores and briefly analyzes the forces driving the significant changes in the market that have affected not only design and manufacturing but rather the entire product life cycle. Moreover, it identifies the expected changes and business opportunities in manufacturing due to new legislation requiring manufacturer accountability during the entire life cycle.
The rampant changes marking modern manufacturing are driven by: (a) excess manufacturing capacity... more The rampant changes marking modern manufacturing are driven by: (a) excess manufacturing capacity and the consequent increase in competition, and (b) rising environmental awareness and legislation. This green legislation (WEEE, EuP, RoHS, etc.) has arisen in an attempt to resolve the inherent conflict between a number of competing needs: (1) environmental requirements and constraints, (2) consumer demands and (3) industrial profitability constraints. Consequently, modern industries seeking to maintain corporate profits while complying with new legislation have begun to shift from product delivery to through-life service support. That is, companies supply products and continue to maintain them throughout the product’s lifetime. Industrial profitability in such a paradigm requires technological adaption and innovation as well as enhanced product performance control. All these changes and requirements are dictating change in design approaches and practices. This paper presents a new de...
ABSTRACT A novel, set-operations rather than geometry-oriented, solid geometrical modeler is prop... more ABSTRACT A novel, set-operations rather than geometry-oriented, solid geometrical modeler is proposed. The modeler is based upon the representation of objects by switching functions and thus is capable to perform the set (Boolean) operations very efficiently. The graphical support and communication with the real world are provided via the extended three-dimensional Karnaugh map.
ABSTRACT From the text: This special issue is a compilation of research papers submitted to MAMEN... more ABSTRACT From the text: This special issue is a compilation of research papers submitted to MAMENC 2012, held on October 25–26, 2012 in Beijing.
Although bending is one of the final processes in sheet metal part manufacture, it is relatively ... more Although bending is one of the final processes in sheet metal part manufacture, it is relatively inaccurate compared to the other components of sheet metal processing. Critical tolerances at several locations on the sheet metal part impose limitations on bending operations and sequences. The lack of success up to now in embedding accuracy in process planning for sheet metal products has resulted mainly from the fact that tolerance analysis usually requires simulating the manufacturing process. This paper discusses the issue of automatic determination of the bending sequence in sheet metal products subject to critical tolerance constraints. It proposes conditions for identifying cases where the problem of determining the bending order which results in the best accuracy at specific locations is, in fact, a topological problem. Two explicit rules for achieving the best accuracy in such cases are formulated and then demonstrated by using these rules to construct a precedence graph.
This paper presents a method for classifying pen strokes in an on-line sketching system. The meth... more This paper presents a method for classifying pen strokes in an on-line sketching system. The method, based on linear least squares fitting to a conic section equation, proposes using the conic equation’s natural classification property to help classify sketch strokes and identify lines, elliptic arcs, and corners composed of two lines with an optional fillet. The hyperbola form of the conic equation is used for corner detection. The proposed method has proven to be fast, suitable for real-time classification, and capable of tolerating noisy input, including cusps and spikes. The classification is obtained in o(n) time in a single path, where n is the number of sampled points. In addition, an improved adaptive method for clustering disconnected end-points is proposed. The notion of in-context analysis is discussed, and examples from a working implementation are given.
This paper presents an algorithm for solving the complex and critical problem of bending sequence... more This paper presents an algorithm for solving the complex and critical problem of bending sequence in sheet metal manufacturing. Finding the bending sequence and required tool assignment presents a large combinatorial problem which is impossible to solve optimally for practical applications within a reasonable period of time. The paper presents a two-stage algorithm. The first stage finds a feasible solution based upon collision avoidance heuristics. The second stage rapidly seeks an alternative feasible sequence with a lower cost without exceeding time limitations. The algorithm is very practical because it reaches a low-cost solution quickly within computer memory limitations. In this paper, the problem is defined, the approach is presented formally, and finally, the power of the algorithm is demonstrated by solving bending sequences for real products.
2008 IEEE International Conference on Networking, Sensing and Control, 2008
ABSTRACT Behavior permissiveness is the most important criterion in evaluating the performance of... more ABSTRACT Behavior permissiveness is the most important criterion in evaluating the performance of a liveness-enforcing supervisor. For a class of Petri nets, S3PR, this paper explores a sufficient condition under which there exists a maximally permissive monitor-based liveness-enforcing Petri net supervisor. It can be computed in an iterative way. At each iteration, a siphon is derived by the MlP-based deadlock detection method and controlled with its control depth variable being unit. We conclude that, for any S3PR structure N, there exists an initial marking Mo such that a maximally permissive liveness- enforcing supervisor can be always found for (N, M0). The results obtained in this research are fully based on elementary siphons that are developed in our previous work. A flexible manufacturing example is used to demonstrate the proposed methodology.
2008 IEEE International Conference on Networking, Sensing and Control, 2008
ABSTRACT A deadlock prevention policy is proposed for a class of Petri nets with uncontrollable t... more ABSTRACT A deadlock prevention policy is proposed for a class of Petri nets with uncontrollable transitions. It consists of two stages: siphon control and control-induced siphon control. At first stage, a monitor or control place is added for each elementary siphon such that it can never be unmarked. Due to the addition of monitors, new control-induced siphons are possibly generated in the augmented net. The second stage ensures that monitors are added to make always marked control-induced siphons without generating new control-induced siphons. The major difference of the proposed policy is that at each step the existence of uncontrollable transitions in a plant net model is considered. The results obtained in this paper show that elementary siphon based deadlock control policies are much more promising than those in the literature, particularly in coping with large-szied models. A flexible manufacturing example is utilized to illustrate the methods proposed.
ABSTRACT Although Mixed-Model assembly lines have a number of advantages over Single-Model lines,... more ABSTRACT Although Mixed-Model assembly lines have a number of advantages over Single-Model lines, they suffer from several drawbacks, such as increased assembly complexity and greater work flow fluctuations, mainly due to the differences between the models assembled in the line. This research has adopted a new approach to cope with the above disadvantages in which the models are clustered into several assembly lines. The research presents a Model Partitioning and Clustering Algorithm (MPCA), which determines the similarity between models and assigns them accordingly to different parallel assembly lines. Empirical analysis shows that the MPCA can find a better solution than the optimal solution for one Mixed-Model line, which assembles all the models simultaneously.
The paper considers the problem of simultaneous identification and trajectory tracking of moving ... more The paper considers the problem of simultaneous identification and trajectory tracking of moving objects (either 2D or 3D) from moving sensors. The identification is parametric and is based on knowing the family that the object belongs to, e.g. ball, ellipsoid, box, etc. The mathematical formulation results in implicit measurements, i.e. an algebraic equation that includes both state variables and actual measurements. The method of solution is via Extended Kalman Filter where the unknown parameters are regarded as additional state variables. Standard Extended Kalman Filter and Iterative Extended Kalman Filter yielded unsatisfactory results, mainly due to the nonlinearity of the measurements in both the state vector and the noise. A new algorithm, called Noise Updated Iterative Extended Kalman Filter is suggested. Its deviation from the standard iterative Kalman filter is in estimating the measurement noise at each iteration. The estimated noise is then used in the linearization stag...
Innovation in Life Cycle Engineering and Sustainable Development
ABSTRACT Cultural and public attitudes as well as new business approaches and life cycle concepts... more ABSTRACT Cultural and public attitudes as well as new business approaches and life cycle concepts have impacted and will continue to impact not only matters of consumption and use but indeed almost every aspect of the product life cycle. Ecological awareness, globalization and excess manufacturing capacity along with intensive competition are the main factors that have led to what is no less than a revolution in design and manufacturing. This revolution is enabled by improved information technology. This paper explores and briefly analyzes the forces driving the significant changes in the market that have affected not only design and manufacturing but rather the entire product life cycle. Moreover, it identifies the expected changes and business opportunities in manufacturing due to new legislation requiring manufacturer accountability during the entire life cycle.
The rampant changes marking modern manufacturing are driven by: (a) excess manufacturing capacity... more The rampant changes marking modern manufacturing are driven by: (a) excess manufacturing capacity and the consequent increase in competition, and (b) rising environmental awareness and legislation. This green legislation (WEEE, EuP, RoHS, etc.) has arisen in an attempt to resolve the inherent conflict between a number of competing needs: (1) environmental requirements and constraints, (2) consumer demands and (3) industrial profitability constraints. Consequently, modern industries seeking to maintain corporate profits while complying with new legislation have begun to shift from product delivery to through-life service support. That is, companies supply products and continue to maintain them throughout the product’s lifetime. Industrial profitability in such a paradigm requires technological adaption and innovation as well as enhanced product performance control. All these changes and requirements are dictating change in design approaches and practices. This paper presents a new de...
ABSTRACT A novel, set-operations rather than geometry-oriented, solid geometrical modeler is prop... more ABSTRACT A novel, set-operations rather than geometry-oriented, solid geometrical modeler is proposed. The modeler is based upon the representation of objects by switching functions and thus is capable to perform the set (Boolean) operations very efficiently. The graphical support and communication with the real world are provided via the extended three-dimensional Karnaugh map.
ABSTRACT From the text: This special issue is a compilation of research papers submitted to MAMEN... more ABSTRACT From the text: This special issue is a compilation of research papers submitted to MAMENC 2012, held on October 25–26, 2012 in Beijing.
Although bending is one of the final processes in sheet metal part manufacture, it is relatively ... more Although bending is one of the final processes in sheet metal part manufacture, it is relatively inaccurate compared to the other components of sheet metal processing. Critical tolerances at several locations on the sheet metal part impose limitations on bending operations and sequences. The lack of success up to now in embedding accuracy in process planning for sheet metal products has resulted mainly from the fact that tolerance analysis usually requires simulating the manufacturing process. This paper discusses the issue of automatic determination of the bending sequence in sheet metal products subject to critical tolerance constraints. It proposes conditions for identifying cases where the problem of determining the bending order which results in the best accuracy at specific locations is, in fact, a topological problem. Two explicit rules for achieving the best accuracy in such cases are formulated and then demonstrated by using these rules to construct a precedence graph.
This paper presents a method for classifying pen strokes in an on-line sketching system. The meth... more This paper presents a method for classifying pen strokes in an on-line sketching system. The method, based on linear least squares fitting to a conic section equation, proposes using the conic equation’s natural classification property to help classify sketch strokes and identify lines, elliptic arcs, and corners composed of two lines with an optional fillet. The hyperbola form of the conic equation is used for corner detection. The proposed method has proven to be fast, suitable for real-time classification, and capable of tolerating noisy input, including cusps and spikes. The classification is obtained in o(n) time in a single path, where n is the number of sampled points. In addition, an improved adaptive method for clustering disconnected end-points is proposed. The notion of in-context analysis is discussed, and examples from a working implementation are given.
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