A neutrosophic set-based TLBO algorithm for the flexible job-shop scheduling problem with routing flexibility and uncertain processing times

Different with the plain flexible job-shop scheduling problem (FJSP), the FJSP with routing flexibility is more complex and it can be deemed as the integrated process planning and (job shop) scheduling (IPPS) problem, where the process planning and the job shop scheduling two important functions are considered as a whole and optimized simultaneously to utilize the flexibility in a flexible manufacturing system. Although, many novel meta-heuristics have been introduced to address this problem and corresponding fruitful results have been observed; the dilemma in real-life applications of resultant scheduling schemes stems from the uncertainty or the nondeterminacy in processing times, since the uncertainty in processing times will disturb the predefined scheduling scheme by influencing unfinished operations. As a result, the performance of the manufacturing system will also be deteriorated. Nevertheless, research on such issue has seldom been considered before. This research focuses on the modeling and optimization method of the IPPS problem with uncertain processing times. The neutrosophic set is first introduced to model uncertain processing times. Due to the complexity in the math model, we developed an improved teaching-learning-based optimization(TLBO) algorithm to capture more robust scheduling schemes. In the proposed optimization method, the score values of the uncertain completion times on each machine are compared and optimized to obtain the most promising solution. Distinct levels of fluctuations or uncertainties on processing times are defined in testing the well-known Kim’s benchmark instances. The performance of computational results is analyzed and competitive solutions with smaller score values are obtained. Computational results show that more robust scheduling schemes with corresponding neutrosophic Gantt charts can be obtained; in general, the results of the improved TLBO algorithm suggested in this research are better than those of other algorithms with smaller score function values. The proposed method in this research gives ideas or clues for scheduling problems with uncertain processing times.

Effect of routing flexibility on the performance of manufacturing system

This work presented in this paper is based on the simulation of the routing flexibility enabled manufacturing system. In this study four levels of each factor (i.e. routing flexibility, system load conditions, system capacity and four part sequencing rules) are considered for the investigation. The performance of the routing flexibility enabled manufacturing system (RFEMS) is evaluated using three performance measures like make-span time, resource utilization and work-in-process. The analysis of results shows that the performance of the manufacturing system may be improved by adding in routing flexibility at the initial level along with other factors. However, the benefit of this flexibility diminishes at higher levels of routing flexibilities.

Maximally permissive deadlock prevention policies for flexible manufacturing systems using control transition

Nowadays, many kinds of flexible manufacturing systems are used to process many complex manufacturing works due to their machine flexibility and routing flexibility. However, such competition (i.e. robots and machines) for shared resources by concurrent job processes can lead to the problem of a system deadlock. In existing researches, almost experts adopted place-based as controllers to solve the deadlock problems of flexible manufacturing systems whatever the concept of siphons or the reachability graph method are used. Among them, only the reachability graph ones can obtain maximally permissive live states. In this article, the authors try to propose one novel transition-based deadlock prevention concept to solve flexible manufacturing system’s deadlock problem. In addition, two algorithms are developed to support above concept. The experimental results indicate that the proposed policy not only can obtain maximally permissive controllers but also recover all original deadlock markings.

A Highly Efficient and Optimised Simulation Based Multi objective Decision-Making for FMS Control

Optimized and efficient decision-making systems is the burning topic of research in modern manufacturing industry. The aforesaid statement is validated by the fact that the limitations of traditional decision-making system compresses the length and breadth of multi-objective decision-system application in FMS. The bright area of FMS with more complexity in control and reduced simpler configuration plays a vital role in decision-making domain. The decision-making process consists of various activities such as collection of data from shop floor; appealing the decision-making activity; evaluation of alternatives and finally execution of best decisions. While studying and identifying a suitable decision-making approach the key critical factors such as decision automation levels, routing flexibility levels and control strategies are also considered. This paper investigates the cordial relation between the system ideality and process response time with various prospective of decision-making approaches responsible for shop-floor control of FMS. These cases are implemented to a real-time FMS problem and it is solved using ARENA simulation tool. ARENA is a simulation software that is used to calculate the industrial problems by creating a virtual shop floor environment. This proposed topology is being validated in real time solution of FMS problems with and without implementation of decision system in ARENA simulation tool. The real-time FMS problem is considered under the case of full routing flexibility. Finally, the comparative analysis of the results is done graphically and conclusion is drawn.

Simulation of Manufacturing System at Different Part Mix Ratio and Routing Flexibility

In present market scenario, manufacturing industries need to focus towards capability to provide high product variety and availability of products at the point of demand. This situation creates pressure on manufacturing firms to be flexible and to reduce lead time to fulfill customer's demand on time. Flexible Manufacturing Systems (FMS) with appropriate Routing Flexibility (RF) in addition to different scheduling strategies is the appropriate manufacturing alternative in such a case. Such systems are capable to adjust changing product mix yet providing higher performance in dynamic business environment. This research work presents simulation analysis of a FMS with varying Routing Flexibility (RF) level at different part mix ratio to validate this. The results show that varying part mix ratio has appreciable effect on the system performance, when no routing flexibility is present in the system. Also for all product mix ratios, increase in routing flexibility levels continues to improve MST performance with diminishing return.