Suresh K. Khator

Power distribution planning: a review of models and issues

Power distribution planning is a complex task in which planners must ensure that there is adequate substation capacity (transformer capacity) and feeder capacity (distribution capacity) to meet the load demands. Decisions such as allocation of power flow, installation of feeders and substations, and procurement of transformers are costly ones which must be evaluated carefully. This paper provides a review of research problems as well as models related to the planning of substations and/or distribution feeders. Following a general discussion, we review existing research work under two major groups: planning under normal conditions, and planning for emergency. A discussion on relevant research opportunities is included.

A survey of Petri net applications in modeling controls for automated manufacturing systems

Abstract Recent literature on Petri net applications to model controls of automated manufacturing systems is discussed. Modeling controls is essential to prevent the incidence of system deadlock which could possibly occur due to the concurrent and asynchronous nature of activities. It is difficult to implement an efficient programmable logic controller program for a manufacturing plan without solving this problem. Research findings on control model generation and analysis are discussed in the light of the deadlock problem and performance evaluation. Past and present research in these areas is critically examined in an attempt to focus on the guidelines for on-going research in control modeling.

Cell formation in group technology: a new approach

Abstract In the U.S.A., machine-component cluster formation is considered a poor alternative to classification and coding as a planning tool for Cellular Manufacture. This paper introduces a heuristic procedure, the Occupancy Value method, for identifying clusters in a machine-component matrix created from route card data. A unique feature of this method is that it progressively develops block diagonalization starting from the northwest corner of the matrix. The flexibility of the procedure is illustrated in detail through a small example. Another large matrix is analyzed to demonstrate the inherent simplicity of the method. Further extensions of this method to implement the manufacturing cells from these initial clusters are discussed.

System reconfiguration to avoid deadlocks in automated manufacturing systems

Recent demands for small and medium-batch production runs have put additional constraints on automated manufacturing systems. Controlling the processes in such systems is difficult due to concurrent and asynchronous interactions that cause system deadlocks. Deadlocks occur in a system when a set of concurrent processes becomes interlocked in such a way that they cannot be completed. This paper reports on the control of deadlocks in a simple automated manufacturing system consisting of three workstations arranged around a transporter and process a single part. Deadlock detection and avoidance were performed off-line and the system was reconfigured by re-allocating the buffer capacity at the critical workstations. Petri Net formalism was used as the modeling tool for its ability to model concurrent and asynchronous activities, and its sound mathematical foundations for analysis. The model was numerically tested on the SUN Workstation under varying operating characteristics to study deadlock-free performance and compute effective buffer capacity at the critical workstations.

Analysis of tool sharing in an FMS: a simulation study

Abstract This research concentrates on the impact of tool request selection and tool dispatching rules in a tool sharing environment. Request selection rules are invoked when more than one request for a tool are pending. Tool selection rules, on the other hand, come into play when there are more than one copy of tools in the system. A “look ahead” method has been used to determine the requirement of tools. Various rules for tool sharing have been studied with makespan and tool transporter utilization as performance measures. Simulation was used for modeling the system. The impact of factors such as product mix and duplication of tools have also been addressed. Design of experiments techniques were used to analyze simulation outputs. The analysis of results indicated that the tool selection rules significantly affect the performance of the tool transporter while the request selection rules do not affect the system. Request selection rules affect the makespan of the system when the number of tool copies is one. Factors such as product mix and duplication of tools also affect the system.

Operational control of multi-load vehicles in an automated guided vehicle system

Abstract An alternative to increasing the AGV fleet size in order to improve the availability of vehicles is to introduce vehicles with multiple load carrying capacity. This paper attempts to study the effect of different dispatching rules in the case of multi-load vehicles, on the overall performance of an AGVS. A comparison between the performance of a fleet comprising unit load vehicles is also made with that of multi-load vehicles.

Intermediate tool requirement planning for FMS

Abstract Tool automation is fast becoming a vital aspect of computer-integrated manufacturing. While studies on the control components of tool management have been many, there are relatively few on the planning components. This paper addresses important issues in tool planning, including tool procurement, tool-life inventory, and use of alternative tools. We will explore the issues and decisions involved in tool requirement planning (TRP). A planning model formulated as a linear program is presented along with an illustrative example. In an era when companies are considering schemes such as just in time (JIT) to minimize product inventory, it should prove fruitful to have a coherent tool procurement and inventory policy as well.

A Petri net approach for modelling controls of a computer-integrated assembly cell

Abstract A computer-integrated assembly cell (CIAC) plays an important role in modern manufacturing systems. To maximize cell utilization, multiple assembly jobs are often scheduled concurrently without consideration for the complex interaction between workstations. Sharing of assembly workstations among a set of concurrently flowing processes may cause deadlocks and conflicts, which are difficult to detect during programming of the cells controller. This paper presents an overview of the control models developed for deadlock and conflict detection, and performance evaluation of manufacturing plans processed in a CIAC. Petri net formalism is used as the modelling tool for its ability to model concurrent and asynchronous activities, and for its well developed mathematical foundation for analysis and performance evaluation. The control model presented in this paper consists of modules for Petri net generation, deadlock detection, and performance evaluation. The control model may be applied to debugging con...

Transformer procurement and relocation at a large electric utility: a mixed 0-1 linear programming model

The Power Delivery Substation Division at Florida Power and Light (FPL) must plan and provide logistical support for about two thousand transformers located at roughly four hundred substations. Each year, to meet new transformer requirements, the Division must make the decisions of procuring and/or relocating transformers. Due to the large number of transformers and substations involved, there is a strong need for a systematic approach to determine optimally the decisions for transformer procurement and relocation, as well as their schedules. In this paper, a mixed 0-1 linear programming model is developed for that purpose. >

Multiobjective decision making approach for determining alternate routing in a flexible manufacturing system

Abstract In a Flexible Manufacturing System a particular operation on a job can be performed at several machines because of inherent capability of the machines to load multiple tools. There is a choice in the system as to which workstation each operation should be performed. Any entering workpiece therefore has the choice of several different routes. In such a complex scenario productivity could be improved by selecting an efficient routing under computer control. This paper formulates the problem as a Coal Programming model which provides a way of striving towards several objectives simultaneously. Thus the goals to be considered are - (i) to satisfy the forecasted demand, (ii) to minimize the material movements and (iii) to minimize the workload imbalance on all the machines. The solutions obtained on solving this model specify the efficient routing to be implemented. Non-preemptive penalty values are considered for comparing the goal programming formulation with prevailing single criterion objective formulations. Appropriate reasoning for the determined penalty values for the deviations from each goals are given. An illustrative example is considered to study alternate routing under multiple criteria. Lastly, utilization of the goal programming tool lies in evaluating the different layouts and determining the best layout. The layout with minimum workload imbalance and comparatively less material movement is recommended to be the best layout.