## 4 Assembly Line Balancing Problems with Stochastic or Fuzzy Parameters
### Assembly and Production Line Balancing Problems with Fuzzy Parameters
A real-life case study from mass transit railway in Hong Kong is presented to verify the proposed model. The aim of the paper [105] is to reverse an assembly line using a mobile platform equipped with a manipulator. Reversibility means that the assembly line is able to perform disassembly as well. For this purpose, a (dis)assembly line balancing and a synchronized hybrid Petri nets model were used to model and control a (dis)assembly line, with a fixed number of workstations, served by a wheeled mobile robot equipped with a robotic manipulator. The model is of a hybrid type, where the (dis)assembly line is a discrete part while the wheeled mobile robot with a robotic manipulator is a continuous part. The model operates in synchronized mode with signals from several sensors. disassembly starts after the assembly process and after the assembled piece fails the quality test in order to recover the parts. The wheeled mobile robot with a robotic manipulator was used only during disassembly, to transport the parts from the disassembling locations to the storage locations. Using these models, a real-time control structure has been designed and implemented, allowing automated assembly and disassembly, where the latter was assisted by a mobile platform equipped with a manipulator. The paper [106] aims to study a specific type of disassembly line with multi-robotic workstations, where multiple industrial robots perform different disassembly operations on the obsolete products of different models. The industrial robots on the disassembly line were differently skilled and had non-identical disassembly operation durations along with energy consumption. Considering the given conditions of the returned products, a task-based operation digraph and a subassemblies-based and/or graph were used to represent the precedence constraints of the disassembly operation sequence. A mixed-integer mathematical programming was developed for the considered problem, with three conflicting objectives of minimizing the cycle time, the peak-total energy consumption and the cost of hazardous tasks. Successfully solving practical disassembly line balance problems is usually subject to a great number of uncertainties in the real-life problems. The uncertainties in disassembly operation durations were solved by stochastic, fuzzy and interval programming algorithms. Computational results of the conducted experiments on problem instances were presented. The disassembly line is one of the most important tools to handle large quantities of waste electronic and electrical equipment. The DLBP is to assign disassembly operations to each available workstation reasonably while satisfying various given constraints, which is one of the challenging topics. Considering the uncertainty, environmental protection and economic benefits of disassembly, the paper [107] established a stochastic partial DLBP that comprehensively evaluates the number of used workstations, workload smoothness, energy consumption and disassembly profit. To obtain feasible solutions with a high quality, a multi-objective discrete flower pollination algorithm was developed. This algorithm establishes heuristic rules, discrete operations and multi-objective algorithms combined with the characteristics of the partial DLBP. The effectiveness and application ability of the proposed model and algorithms were verified by a disassembly example of a waste printer. Various disassembly schemes were obtained, which can provide guidance for a decision-maker to construct disassembly lines. End-of-life products with large sizes are suitable for disassembly operations on the two-sided disassembly line. The destructive disassembly is required in the disassembly process. The negative impacts caused by destructive disassembly during the disassembly process are usually ignored in the OR literature.