This issue focuses on production planning and scheduling for production system and the related problems that have arisen in these areas in the last half century as digital computer systems developed. These problems relate to production management, production planning, shop floor control, product design and process planning. In the first stage of production planning and scheduling systems R&D, optimization is a key issue that has been widely discussed and many theories and optimization algorithms proposed. Rule-based methods are discussed as potential solutions to these problems.
With rapid advances in computer and information processing technologies and performance, tremendous progress has been made in the areas of production systems such as production planning, production scheduling, advances production systems (APS), enterprise resource planning (ERP), just-in time (JIT) processes, the theory of constraint (TOC), product data management (PDM) and computer-aided design / manufacturing / engineering (CAD/CAM/CAE).
With new approaches being proposed and applied all the time to the production planning and scheduling problems to cope with dynamically changing manufacturing environments, manufacturers must respond quickly and flexibly to customer needs and requests in domestic and international markets under globalized competition. These include metaheuristics, multiagent approaches, object-oriented modeling, and large-scale simulation/evaluation.
This special issue addresses the latest research advances, applications, and case studies in production planning and scheduling covering such as decentralized and autonomous production systems, distributed simulation models, robust capacity planning models, wireless sensor networks for production systems and applications to automotive component and steel production.
We hope that learning about these advances will enable readers to share their own experience and knowledge in technology, new developments and the potential applications of production planning and scheduling methods and solutions.
With the aim of solving the coverage problem of a wireless sensor network, a node deployment algorithm for the wireless sensor network, one based on a perception model, is designed in this work. The simulation results show that this algorithm can effectively deploy the wireless sensor network node, improve the network’s coverage, reduce the energy consumption of the network node, and help the network to function longer.
This paper proposes a robust method of capacity requirements planning (CRP) that can generate a stable load plan against dynamic changes in a manufacturing environment. In our study, robustness refers to the degree of stability in the load plan for the occurrence of unexpected events. The purpose of the proposed method is to determine the processing periods of operation orders with the aim of minimizing the probability that the resource requirement of each operation order will exceed the capacity of corresponding resources. Through numerical experiments, we demonstrate the effectiveness of the proposed CRP method in terms of its robustness.
A questionnaire survey was conducted and analyzed with the analytic hierarchy process (AHP) to evaluate the suitability of carbon-fiber-reinforced plastic (CFRP) for use in automobile parts from an engineer’s viewpoint. The results indicated that carbon fiber has a higher potential for use in the framework than as an outer panel or exterior material. In addition, unidirectional and isotropic CFRPs can be used as alternatives to steel for higher-class automobiles. The critical evaluation criteria for carbon fiber are the material cost, safety, stiffness, and corrosion resistance. With the innovative carbon fiber project of the Ministry of Economy, Trade and Industry, CFRP has high potential as an alternative material for not only Class S but also Class A automobiles. In a dramatic innovation scenario with regard to the safety, stiffness, and thermal degradation of carbon fiber, CFRP was found to be a potential alternative material for more than half of the parts of Class A automobiles and several parts of Class C automobiles.
This paper proposes a solution for casting scheduling, an important process in steel manufacturing. A constraint due to secular changes in quality properties, including slab property degradation in casting, and problems with evaluation indices for slab casting width for the improvement of productivity, are taken into account in the study. These factors have not been focused on in previous studies. In this study, the casting scheduling problem is divided into two. One problem involves determining a schedule frame for each slab, and the other is the problem of determining the slab width. To be more specific, after an initial solution for slab order is reached based on heuristics with the quality property constraint taken into account, a hierarchical solving method of determining the slab width is employed in accordance with the shortest path problem-solving method, and obtained solutions are improved using a simulated annealing technique. The simulation is performed with the data created from actual operation data and an initial solution that satisfies the constraint is derived. An improved solution is then obtained using the solution search technique.
Simulators play important roles in the designing of new manufacturing systems. As manufacturing systems are being created on larger and more complicated scales than ever before, it is increasingly necessary to have opportunities for several persons to design a manufacturing system concurrently. In this case, the designers often use suitable discrete event simulators to evaluate their assigned subsystems. After the subsystems are evaluated, it is necessary to evaluate the full system. To do this, the designers need to make the manufacturing system model by synchronizing several different simulators. In such distributed simulation systems using discrete event simulators, it is important to manage a distributed simulation clock and each simulator clock as well as to define interfaces among the simulation models. With the simulation clock, it is often necessary to perform rollbacks. The rollback function returns the simulation clock to a past time in order to synchronize events among the simulations. However, most commercially available simulators do not include the rollback function.
The purpose of this research is to develop a distributed simulation synchronization method that includes a function for managing distributed simulation clocks without the rollback function and for managing interfaces among simulation models.
In this paper, we propose a storage model concept as the method. We develop an algorithm to implement the proposed concept, and we develop a distributed simulation system configuration using HLA. A case study is then carried out to evaluate the performance of the cooperative work.
In this study, a virtual production line is used to present a method for generating assembly process-relational plans for a product according to the configurations of the production line and verify the effectiveness of the proposed method. In an autonomous production system, process-relational plans are generated dynamically by agents based on process-relation graphs. Usually, such process-relation graphs are not determined uniquely and often have some degrees of freedom. Therefore, more practical and efficient assembly process-relational plans would be obtained if process-relation graphs were rewritten according to changes in the configurations of actual production lines. In the proposed method, process-relation graphs are rewritten dynamically by agents using two simple rewriting rules. The results from simulations on a virtual assembly line provided that the progress of the assembly job differs with the quantities of invested jobs and machine layouts. Accordingly, the simulation results prove the usefulness of rewriting process-relation graphs according to the configurations of actual shop floors.
Due to higher degrees of individualization, shorter product life cycles, and volatile selling markets, fulfilling customer demands – the main task of automotive companies – has become very complex. In order to tackle this complexity, new concepts that enable the decentralization of decision-making within the production process have become promising solutions. The advancement towards self-organized production requires novel approaches in the field of production program planning. This work introduces the concept of the volume cycle as a new design factor in program planning. Additionally, a novel method to identify flexibility potentials in production sequences based on flexibility graphs is proposed, and the method is validated through a case study considering a segment of the assembly process for an automobile. Suitable visualization techniques for flexibility graphs are also discussed. Furthermore, in order to allow automatic analysis and evaluation of the flexibility potentials, methods of graph mining are introduced and the application possibilities of these techniques in terms of analyzing flexibility graphs are clarified. The results obtained from the case study illustrate that routing flexibility is not leveraged in today’s production lines, thus revealing a potential optimization domain.
This paper introduces an adaptive attitude control based on a backstepping control scheme for a quadrotor helicopter test bed. First, aerodynamics and motion equations are provided to model the dynamics of the quadrotor and a Virtual Reality (VR) model is developed incorporating the dynamic model to the virtual results of simulation. Then, an adaptive backstepping algorithm is applied to the attitude control and this algorithm is adaptive according to Lyapunov-based stability analysis. Finally, the simulation results with many types of reference signals are provided to demonstrate the good tracking performance of the proposed control algorithm.
This paper presents an investigation on the sensitivity of a thermal sensor, which will be used as a contact detection sensor for surface defect inspections. In the proposed concept, frictional heat generated at a slight contact between a defect on a measuring surface and the thermal sensor will be utilized to find out existences of defects on the measuring surface. The frictional heat will be detected as a deviation of the electrical resistance of the sensing element in the thermal sensor. According to the principle, the sensor temperature will increase at the contact with defects. However, in the previous research by the authors, the sensor temperature was found to decrease at the contact with the glass-ball probe, whose tip diameter was on the order of several-ten μm. Following the experiments in the previous study, in this paper, further experimental investigation is carried out by employing an AFM probe as a nano-tip probe so that the sensitivity of the thermal sensor as a contact detection sensor for nano-scale defects inspection can be verified. Furthermore, a possible mechanism of the heat flow at the contact interface, which can explain the results observed in these experiments, is also introduced.
A high-speed precision air-bearing tool spindle with active aerodynamic bearing is proposed for improving the quality of machining using small-diameter cutting and grinding tools. The spindle is basically supported by aerostatic radial and thrust bearings. According to the spindle vibration detected by capacitance sensors, the wedge angle of the active aerodynamic bearing was controlled using piezoelectric actuators, thereby suppressing the spindle vibration. In the present paper, the performances of a prototype air-bearing spindle with single-row active aerodynamic bearing and an improved air-bearing spindle with double-row bearings are reported. Through experiments, it was demonstrated that the maximum rotational speed controlled by the active aerodynamic bearing is 800 Hz (48,000 min-1), and that the amplitude of spindle vibration can be suppressed to < 50 nm at the rotational speed of 500 Hz (30,000 min-1).
Inventory management in reverse logistics is more complex than that in conventional logistics because of uncontrollable factors such as inventory levels increasing from reverse logistics, greater-than-expected disposal, and balance of supply and demand with changing market trends. This paper proposes a new economic order quantity (EOQ) model for reuse and recycling by expanding the EOQ model proposed by Dobos and Richter, 2004. The proposed model introduces a sequentially accumulated marginal reuse rate as a parameter in considering the balance of product demand and supply. The marginal reuse rate is calculated by using data on production distribution and disposal distribution of products for every discretized period. This model considers the sequence among recovery options: reuse, recycle and disposal. Parts are reused after having been inspected to determine whether they are reusable or not. Remaining nonreusable parts are recycled and any remaining nonrecycled parts disposed of. The extended EOQ model is applied to a case study using different scenarios for length of use and multiple generations of products. Results of computer experiments confirmed the effectiveness of the proposed method.
Thin functional barrier layers of aluminum oxide (Al2O3) that are used particularly in photovoltaic (PV) modules to prevent the possibility of water vapor ingress should be applied over the entire PV surface without any defects. However, for barrier layer thicknesses within the sub-micrometer range (up to 50 nm) produced through the atomic layer deposition (ALD) method, it is common for defects to occur during the production process. To avoid defective barriers from being incorporated in the final PV unit, defects need to be detected during the barrier production process. In this paper, the implementation of in process inspection system capable of detecting surface defects such as pinholes, scratches, or particles down to a lateral size of 3 μm and a vertical resolution of 10 nm over a 500 mm barrier width is presented. The system has a built-in environmental vibration compensation capability, and can monitor ALD-coated films manufactured using roll-to-roll (R2R) techniques. Ultimately, with the aid of this in process measurement system, it should be possible to monitor the coating surface process of large-area substrates, and if necessary, carry out remedial work on the process parameters.
After the advantages and disadvantages of current methods of calibration are analyzed and contrasted, the comparatively widely applied Zhang Zhengyou calibration method is adopted in this paper, but it is used to solve problems in a different way. The calibration of a double-priority camera on the basis of a round planar target is proposed, and a computation method based on the on-line intersection of the two circles with the closest proximity is put forward to fix the center of a circle. This method of calibration is simple and flexible, with good robustness, precision, and practical value.