Shahid Maqsood

Hybrid Genetic Algorithm (GA) for job shop scheduling problems and its sensitivity analysis

The Job Shop Scheduling Problem (JSSP) is a hard combinatorial optimisation problem. This paper presents a heuristic-based Genetic Algorithm (GA) or Hybrid Genetic Algorithm (HGA) with the aim of overcoming the GA deficiency of fine tuning of solution around the optimum, and to achieve optimal or near optimal solutions for benchmark JSSP. The paper also presents a detail GA parameter analysis (also called sensitivity analysis) for a wide range of benchmark problems from JSSP. The findings from the sensitivity analysis or best possible parameter combination are then used in the proposed HGA for optimal or near optimal solutions. The experimental results of the HGA for several benchmark problems are encouraging and show that HGA has achieved optimal solutions for more than 90% of the benchmark problems considered in this paper. The presented results will provide a reference for selection of GA parameters for heuristic-based GAs for JSSP.

Evaluation of Repetitive Lifting Tasks Performed in Brick and Concrete Block Factories in Pakistan

Repetitive manual lifting and lowering tasks exposes workers to a high-risk musculoskeletal disorder. This paper aims at the assessment of postures of workers during the piling up process of a Concrete Block and Bricks (CB&B) at CB&B manufacturing factories in Pakistan and to study the effect of different risk factors such as contact force, stresses, and repetition of jobs that put muscles under redundant physical forces, which causes musculoskeletal disorders. The lifting indices (LI) of concrete blocks are 1.57 at the origin and 2.04 at the destination similarly LI for the bricks were 0.60 at the origin and 0.77 at the destination using the NOISH equation. For this purpose, the anthropometric data of 103 workers, working in 33 different factories, was collected. The postures were simulated and analyzed, using a human modelling solution HumanCAD software, with an objective to minimize the risk of work-related injuries, and stresses on the different parts of body was calculated. The results showed in current work environment, 38.83% of workers have lower back musculoskeletal disorder, followed by 31.06% with upper back, 29.12% with thorax and 24.27% with neck. Therefore, re-design the lifting methods of CB&B factories are essential in order to reduce the work-related injuries. The reports were shared with the CB&B industries.

Makespan as a design tool for CMS design

Industries have to cope with millions of parts for production on daily basis. Scheduling of those parts for production is a complex process. Parts having properly scheduled processing rarely get delayed and therefore generally delivered on time. Cellular Manufacturing System (CMS) is a proficient production system and can be used as an effective replacement of Batch type manufacturing. Cell Formation (CF) is the fundamental part of Cell design and its effectiveness is checked using a performance index called Grouping Efficacy (GE).Part scheduling is very rarely used as a design tool for Cell Formation Problem (CFP). A software based solution is developed in this research to solve CFP by applying Genetic Algorithm (GA), which is an Artificial Intelligence (AI) technique. The uniqueness of this approach is that it presents an integrated approach for grouping parts into families and machines into cells using Makespan as the performance factor. Results show that minimizing the Make span maximizes the GE.

Investigation of thermal behaviour and kinetic analysis of Pakistani biomass: Rice husk, sugarcane bagasse and wheat straw using thermogravimetric analysis

Sugarcane bagasse, wheat straw and rice husk are amongst the most abundantly available agriculture residues in Pakistan. Constant supply and huge quantities of these residues make them favourable option to replace the fossil fuels. Thermal degradation of these three samples was studied using TGA at three different heating rates of 5 °C min^-1, 20 °C min^-1 and 40 °C min^-1. The three samples were heated from 25 °C to 900 °C and the influence of heating rate was investigated. Coats-Redfern method was applied to calculate the apparent kinetic parameters. The results showed that the apparent kinetic energy varies from 28.27 kJ mol^-1 to 31.98 kJ mol^-1, 38.39 kJ mol^-1 to 70.22 kJ mol^-1 and 25.05 kJ mol^-1 to 30.42 kJ mol^-1 for bagasse, wheat straw and rice husk respectively. A clear linear fit was obtained using the Coats-Redfern method with above 0.96 coefficient of regression for wheat straw and above 0.97 for sugarcane bagasse and wheat straw respectively. For wheat straw at 40 °C min^-1 heating rate and for the first peak in DTG thermogram of sugarcane bagasse at 5 °C min^-1, the order of reaction was found to be 2.0 and for all three samples, order of reaction was found to be 0.5 for rest of the heating rates. Higher heating rates caused the lateral shift in the TGA thermograms of all three biomass samples but the amount of residual char and ash were unaffected. It was observed that the higher heating rate caused the sudden release of volatile matter from the sample merging the different weight loss peaks, as were evident at lower heating rate in the DTG thermogram of sugarcane bagasse. The values of pre-exponential factor were found to be varied from 12.77-111.08 min^-1, 117.92-1.17×10⁶ min^-1 and 21.45-5.92×10⁴ min^-1 for rice husk, wheat straw and sugarcane bagasse respectively. For order of reaction of 0.5 at 20 °C min^-1 heating rate, three biomass samples can be arranged in terms of activation energy: wheat straw > sugarcane bagasse > rice husk.

Novel Heuristic for Low-Batch Manufacturing Process Scheduling Optimisation with Reference to Process Engineering

Scheduling is an important element that has a major impact on the efficiency of all manufacturing processes. It plays an important role in optimising the manufacturing times and costs resulting in energy efficient processes. It has been estimated that more than 75% of manufacturing processes occur in small batches. In such environments, processes must be able to perform a variety of operations on a mix of different batches. Batch-job scheduling optimisation is the response to such low batch manufacturing problems. The optimisation of batch-job process scheduling problem is still a challenge to researchers and is far from being completely solved due to its combinatorial nature. In this paper, a novel hybrid heuristic (HybH) solution approach for batch-job scheduling problem is presented with the objective of optimising the overall Makespan (Cmax). The proposed HybH is the combination of Index Based Heuristic (IBH) and the Finished Batch-Job (FBJ) process schedule. The heuristic assigns the first operation to a batch-job using IBH and the remaining operations on the basis FBJ process schedule. The FBJ process schedule gives priority to the batch-job with early finished operations, without violating the constraints of process order. The proposed HybH is explained with the help of a detailed example. Several benchmark problems are solved from the literature to check the validity and effectiveness of the proposed heuristic. The presented HybH has achieved batch-job process schedules which have outperformed the traditional heuristics. The results are encouraging and show that the proposed heuristic is a valid methodology for batch process scheduling optimisation.

IMPLEMENTATION OF KANBAN SYSTEM AT THE SHOP FLOOR OF A MULTINATIONAL COMPANY

Streamlining and managing flow of material in high volume production lines reduce the cost in terms of reduction of Work-In-Progress (WIP). Kanban system, which acts as a nerve of JIT production, is being used worldwide due to its simplicity and ability to reduce inventories and production lead times. This paper presents a case study of a successful attempt of implementation of Kanban System (KS) at shop floor of a Multi National Tobacco Factory (MNTF). A traditional Push system was replaced by Pull system with the objectives to reduce filter rods and quantity of raw material at workstations. The conversion from PUSH lo KS simplifies the material issuing procedure and benefits the company by reducing lead-time, Work-In-Process and inventory of finished items. The reduction of WIP is estimated about 59% which resulted in 42.99 million Pakistani Rupees (PKR) savings for the company.