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Papers by Bengt Lennartson
In this paper the design of a time-optimal controller for a class of hybr id systems where the co... more In this paper the design of a time-optimal controller for a class of hybr id systems where the continuous part is modelled by integrator processes is outli ned. The controller may be used for classical tracking problems where the goal is to follow a given trajectory. However, since the control law can be expressed as a function of the present
When implementing control of discrete event systems, the efficiency and reliability would be grea... more When implementing control of discrete event systems, the efficiency and reliability would be greatly improvedif the control algorithms could be automatically synthesised. Using reusable software modules as models of thephysical resources, and part-routing as specifications on the system-behavior, we will show how such automaticgeneration of control algorithms can be achieved. Our approach is based on the Supervisory Control Theory (SCT)developed
Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), 2012
ABSTRACT Lean design and control of an automated material handling system is investigated in this... more ABSTRACT Lean design and control of an automated material handling system is investigated in this study. A universal framework for modeling and analysis of different types of material handling mechanisms is introduced to obtain a minimum number of resources in a system design and fulfill a desired throughput. This framework is developed in a discrete event simulation environment and applied to a case study based on a real pallet system technology. The minimal design of the pallet system is realized by devising the system universal model.
Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), 2012
ABSTRACT In order to perform efficient geometrical simulation and virtual commissioning in stampi... more ABSTRACT In order to perform efficient geometrical simulation and virtual commissioning in stamping, three fields are investigated namely: simulation building time, collision detection time and optimization time. Hence, reducing time is the main theme of this paper. To reduce simulation building time and optimization time, an efficient stamping simulation model is built and tested. Collision detection time is examined by a relative motion method based on 3D to 2D geometrical collision detection. The presented results mean that simulation and virtual commissioning can be performed at least ten times faster compared to standard approaches.
Proceedings of the 24th International Conference on Flexible Automation & Intelligent Manufacturing, 2014
2010 IEEE International Conference on Automation Science and Engineering, 2010
ABSTRACT Handling and locating pallet system is one of the most important subsystems in a flexibl... more ABSTRACT Handling and locating pallet system is one of the most important subsystems in a flexible production plant. The impact of pallet systems parameters on process and energy efficiency of production plants has been verified and examined by a number of studies in the literature. In this paper, introducing novel design constraints for pallets and buffers, a new optimization algorithm under linear constraint models is developed. It generates the precise optimal values for the most challenging variables in a decoupled multiple-loop pallet system. The design variables are number of pallets, conveyor velocity, scheduling of parts, and buffer capacities. In a case study, the optimization algorithm is compared with a more detailed simulation model. The differences between the solutions are minor, although the optimization algorithm only uses partial information, and the computation time is much lower compared to the simulation approach.
2013 IEEE International Conference on Automation Science and Engineering (CASE), 2013
ABSTRACT Lean and agile design and control of an automated material handling system are investiga... more ABSTRACT Lean and agile design and control of an automated material handling system are investigated in this paper. The demands for a minimal number of handling resources and their maximal utilization emphasize the importance of a concurrent structure and control design for a handling mechanism in the conceptual phase. To provide this concurrency, a universal model based on mathematical linear constraints is developed to define a set of part movements without concerning a specific handling technology. Furthermore, an objective characterizing optimal part movements, according to the lean and agile paradigms, is formulated in the conceptual design phase. Control measures, which are obtained by solving the mixed integer linear model including the objective and constraints, provide important keys for designers to conceptualize a proper design of an automated material handling system. To show the application of developed approach, a case study is presented and discussed.
53rd IEEE Conference on Decision and Control, 2014
Lecture Notes in Computer Science, 1997
In this paper we present two strategies to design a hybrid controller for a system described by s... more In this paper we present two strategies to design a hybrid controller for a system described by several nonlinear vector fields. Besides the overall goal to find a controller that stab ilizes the closed-loop hybrid system, the selection will al so be made in such a way that an exponentially stable closed-loop system is obtained. The design strategies are based
1986 25th IEEE Conference on Decision and Control, 1986
ABSTRACT
Proceedings of 1995 IEEE International Conference on Robotics and Automation, 1995
This paper presents part of the results from a research project aimed at increasing flexibility a... more This paper presents part of the results from a research project aimed at increasing flexibility and reusability of cell-control software. First to be discussed are the concept of flexibility and the advantages and disadvantages of various types of modular controllers. Then guidelines and generic models to support system developers are given. The generic models describe the behavior of manufacturing resources and a message-passing structure. The guidelines and the models should be used as the basis when implementing modular control software for machining cells. The two main case studies examined to achieve the models are also briefly described.
Proceedings of IECON '95 - 21st Annual Conference on IEEE Industrial Electronics, 1995
Page 1. Database Design for Machining Cell Level Product Specification Sven-Arne Andr6asson Depar... more Page 1. Database Design for Machining Cell Level Product Specification Sven-Arne Andr6asson Department of Computing Science Anders Adlemo Martin Fabian Per Gullander Bengt Lennartson Dept. of Computer Engineering Control Engineering Lab. Dept. ...
The paper describes the concepts that must be considered in order to achieve a flexible manufactu... more The paper describes the concepts that must be considered in order to achieve a flexible manufacturing system that allows introduction of new products and new resources without total reprogramming of the control system. The basic structure of a resource model is presented and also guidelines for achieving a generic resource model. The description of how to manufacture the products is
2007 IEEE International Conference on Automation Science and Engineering, 2007
ABSTRACT This paper demonstrates how PLC-code for process observation can be automatically genera... more ABSTRACT This paper demonstrates how PLC-code for process observation can be automatically generated from a discrete event process model expressed as either PLC-code or as extended finite automata (EFA). The generated code will also detect faults due to unexplainable sensor signal changes. Extended finite automata are automata augmented with variables and transition conditions. These features make EFA suitable for modeling systems that interact with a PLC through binary signals. In order for the generated observer code to work, the EFA model must fulfill some requirements concerning determinism and observability. These requirements are here formalized. Using the PLC-languages of the IEC 61131 standard for process modeling narrows the gap between the pragmatic industry and the formal academia. The cyclic execution model of a PLC is here replaced by execution at stochastic intervals.
Proceedings of the 1997 American Control Conference (Cat. No.97CH36041), 1997
This paper presents results for stability and robustness of hybrid systems consisting of nonlinea... more This paper presents results for stability and robustness of hybrid systems consisting of nonlinear subsystems. Present stability results that are extensions of classical Lyapunov theory are restricted to certain kinds of hybrid systems. For example, it is required that all subsystems have the same equilibrium point. In this paper these results are generalized, but more importantly, it is shown how
[1992] Proceedings of the 31st IEEE Conference on Decision and Control, 1992
Proceedings of the 36th IEEE Conference on Decision and Control, 1997
This paper presents a constructive method for showing ex-ponential stability of autonomous nonlin... more This paper presents a constructive method for showing ex-ponential stability of autonomous nonlinear systems con-sisting of state-dependent weighted linear systems. This kind of system representation is common in for instance fuzzy systems or is the result of an exact or ...
2012 IEEE International Conference on Automation Science and Engineering (CASE), 2012
In this paper the design of a time-optimal controller for a class of hybr id systems where the co... more In this paper the design of a time-optimal controller for a class of hybr id systems where the continuous part is modelled by integrator processes is outli ned. The controller may be used for classical tracking problems where the goal is to follow a given trajectory. However, since the control law can be expressed as a function of the present
When implementing control of discrete event systems, the efficiency and reliability would be grea... more When implementing control of discrete event systems, the efficiency and reliability would be greatly improvedif the control algorithms could be automatically synthesised. Using reusable software modules as models of thephysical resources, and part-routing as specifications on the system-behavior, we will show how such automaticgeneration of control algorithms can be achieved. Our approach is based on the Supervisory Control Theory (SCT)developed
Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), 2012
ABSTRACT Lean design and control of an automated material handling system is investigated in this... more ABSTRACT Lean design and control of an automated material handling system is investigated in this study. A universal framework for modeling and analysis of different types of material handling mechanisms is introduced to obtain a minimum number of resources in a system design and fulfill a desired throughput. This framework is developed in a discrete event simulation environment and applied to a case study based on a real pallet system technology. The minimal design of the pallet system is realized by devising the system universal model.
Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), 2012
ABSTRACT In order to perform efficient geometrical simulation and virtual commissioning in stampi... more ABSTRACT In order to perform efficient geometrical simulation and virtual commissioning in stamping, three fields are investigated namely: simulation building time, collision detection time and optimization time. Hence, reducing time is the main theme of this paper. To reduce simulation building time and optimization time, an efficient stamping simulation model is built and tested. Collision detection time is examined by a relative motion method based on 3D to 2D geometrical collision detection. The presented results mean that simulation and virtual commissioning can be performed at least ten times faster compared to standard approaches.
Proceedings of the 24th International Conference on Flexible Automation & Intelligent Manufacturing, 2014
2010 IEEE International Conference on Automation Science and Engineering, 2010
ABSTRACT Handling and locating pallet system is one of the most important subsystems in a flexibl... more ABSTRACT Handling and locating pallet system is one of the most important subsystems in a flexible production plant. The impact of pallet systems parameters on process and energy efficiency of production plants has been verified and examined by a number of studies in the literature. In this paper, introducing novel design constraints for pallets and buffers, a new optimization algorithm under linear constraint models is developed. It generates the precise optimal values for the most challenging variables in a decoupled multiple-loop pallet system. The design variables are number of pallets, conveyor velocity, scheduling of parts, and buffer capacities. In a case study, the optimization algorithm is compared with a more detailed simulation model. The differences between the solutions are minor, although the optimization algorithm only uses partial information, and the computation time is much lower compared to the simulation approach.
2013 IEEE International Conference on Automation Science and Engineering (CASE), 2013
ABSTRACT Lean and agile design and control of an automated material handling system are investiga... more ABSTRACT Lean and agile design and control of an automated material handling system are investigated in this paper. The demands for a minimal number of handling resources and their maximal utilization emphasize the importance of a concurrent structure and control design for a handling mechanism in the conceptual phase. To provide this concurrency, a universal model based on mathematical linear constraints is developed to define a set of part movements without concerning a specific handling technology. Furthermore, an objective characterizing optimal part movements, according to the lean and agile paradigms, is formulated in the conceptual design phase. Control measures, which are obtained by solving the mixed integer linear model including the objective and constraints, provide important keys for designers to conceptualize a proper design of an automated material handling system. To show the application of developed approach, a case study is presented and discussed.
53rd IEEE Conference on Decision and Control, 2014
Lecture Notes in Computer Science, 1997
In this paper we present two strategies to design a hybrid controller for a system described by s... more In this paper we present two strategies to design a hybrid controller for a system described by several nonlinear vector fields. Besides the overall goal to find a controller that stab ilizes the closed-loop hybrid system, the selection will al so be made in such a way that an exponentially stable closed-loop system is obtained. The design strategies are based
1986 25th IEEE Conference on Decision and Control, 1986
ABSTRACT
Proceedings of 1995 IEEE International Conference on Robotics and Automation, 1995
This paper presents part of the results from a research project aimed at increasing flexibility a... more This paper presents part of the results from a research project aimed at increasing flexibility and reusability of cell-control software. First to be discussed are the concept of flexibility and the advantages and disadvantages of various types of modular controllers. Then guidelines and generic models to support system developers are given. The generic models describe the behavior of manufacturing resources and a message-passing structure. The guidelines and the models should be used as the basis when implementing modular control software for machining cells. The two main case studies examined to achieve the models are also briefly described.
Proceedings of IECON '95 - 21st Annual Conference on IEEE Industrial Electronics, 1995
Page 1. Database Design for Machining Cell Level Product Specification Sven-Arne Andr6asson Depar... more Page 1. Database Design for Machining Cell Level Product Specification Sven-Arne Andr6asson Department of Computing Science Anders Adlemo Martin Fabian Per Gullander Bengt Lennartson Dept. of Computer Engineering Control Engineering Lab. Dept. ...
The paper describes the concepts that must be considered in order to achieve a flexible manufactu... more The paper describes the concepts that must be considered in order to achieve a flexible manufacturing system that allows introduction of new products and new resources without total reprogramming of the control system. The basic structure of a resource model is presented and also guidelines for achieving a generic resource model. The description of how to manufacture the products is
2007 IEEE International Conference on Automation Science and Engineering, 2007
ABSTRACT This paper demonstrates how PLC-code for process observation can be automatically genera... more ABSTRACT This paper demonstrates how PLC-code for process observation can be automatically generated from a discrete event process model expressed as either PLC-code or as extended finite automata (EFA). The generated code will also detect faults due to unexplainable sensor signal changes. Extended finite automata are automata augmented with variables and transition conditions. These features make EFA suitable for modeling systems that interact with a PLC through binary signals. In order for the generated observer code to work, the EFA model must fulfill some requirements concerning determinism and observability. These requirements are here formalized. Using the PLC-languages of the IEC 61131 standard for process modeling narrows the gap between the pragmatic industry and the formal academia. The cyclic execution model of a PLC is here replaced by execution at stochastic intervals.
Proceedings of the 1997 American Control Conference (Cat. No.97CH36041), 1997
This paper presents results for stability and robustness of hybrid systems consisting of nonlinea... more This paper presents results for stability and robustness of hybrid systems consisting of nonlinear subsystems. Present stability results that are extensions of classical Lyapunov theory are restricted to certain kinds of hybrid systems. For example, it is required that all subsystems have the same equilibrium point. In this paper these results are generalized, but more importantly, it is shown how
[1992] Proceedings of the 31st IEEE Conference on Decision and Control, 1992
Proceedings of the 36th IEEE Conference on Decision and Control, 1997
This paper presents a constructive method for showing ex-ponential stability of autonomous nonlin... more This paper presents a constructive method for showing ex-ponential stability of autonomous nonlinear systems con-sisting of state-dependent weighted linear systems. This kind of system representation is common in for instance fuzzy systems or is the result of an exact or ...
2012 IEEE International Conference on Automation Science and Engineering (CASE), 2012