Deadlock Resolution in Automated Manufacturing Systems With Robots

An automated manufacturing system (AMS) contains a number of versatile machines (or workstations), buffers, and an automated material handling system (MHS). The MHS can be an automated guide vehicle (AGV) system, and/or a system that consists of multiple robots. Deadlock resolution in AMS is an important issue. For the AMS with an AGV system as MHS, the problems of deadlock resolution for part processing process and AGV system as an integrated system has been studied. It is shown that AGVs can serve as both material handling devices and central buffers at the same time to help resolve deadlocks. For AMS with robots as MHS, the existing work treated the robots just as material handling devices and showed that the robots had contribution to deadlock. In this paper, such AMS is modeled by resource-oriented Petri nets. Contrary to the existing work, it is shown that the robots have no contribution to deadlock by adopting such nets to control AMS. More interestingly, they can be used to resolve deadlock by serving as temporary part storage devices. A new deadlock control policy is proposed by treating robots as both material handling devices and buffers. The new policy outperforms the existing ones.     

System reliability and congestion in a material handling system

Congestion in a transportation system prevents vehicles from traveling freely. Therefore, congestion in a material handling system can reduce the system's performance. This paper: (1) develops an analytical methodology for measuring congestion in a material handling system, (2) develops a congestion measure that is measurable in real-time and readily incorporated into existing analytical models for material handling system design and (3) develops quantitative relationships between critical material handling system variables and system congestion.     

Precise automated control of fluid volumes inside glass capillaries

A precise automated apparatus for controlling the position of small fluid sample volumes inside glass capillaries has been developed as part of an automated system for handling submicroliter reaction volumes for genomic analysis. The apparatus uses a linear charge-coupled device (CCD) array, dc motor, pneumatic pump, feedback controller, and a digital signal processor (DSP) to detect the menisci and control in real-time the position of fluid in a clear glass capillary with a resolution of 50 μm. This information is used to infer fluid volumes and control aspiration and dispensing to within 15 nanoliters depending on the inner diameter of the capillary. A computer simulation was developed to determine the effect of thick- and thin-walled capillaries on the detected signals. This simulation showed that, with a geometry appropriate for the overall automated system, a capillary with an inner diameter greater than 0.6 times the outer diameter is optimal to detect the presence of fluid inside the capillary. Thicker walled glass capillaries may be employed if a focusing lens is placed between the light source and the capillary. This result was verified experimentally     

A microcomputer-based decision support system for the management of lumber mill production

Production management for a lumber mill includes the choice of saw patterns, as well as drying, sorting, grading and materials handling operations. The decision support system developed for an existing mill includes a linear programming (LP) model, data base software and a spreadsheet aid for detailed production scheduling. The LP model was structured to minimize total production cost subject to constraints on the available supply of raw material, the required output of timber, the available saw patterns and capacities on production facilities and materials handling operations. The LP solution is used by the spreadsheet support program to schedule product flow on a daily basis. The system was implemented on a microcomputer.     

An investigation of a human material handler on part flow in automated manufacturing systems

This paper presents a formal approach to resolve an important question concerning changes in the control of computerized manufacturing systems when a human operator is involved as a task-performing agent. It requires building a model of human functional specifications used in executing tasks and integrating it into a control scheme for the model. More importantly, analysis of control complexity needs to be conducted to build an effective control mechanism. In this paper, a human material handler is considered, and an assessment of part flow complexity affected by human tasks in a highly automated manufacturing system is presented. For this purpose, a formal model of human task-performing processes is proposed in terms of a part and location(s) of a task. A classification for human material handling tasks is presented based on the proposed model. Furthermore, human errors and the impact of human errors on part flow are considered. Part flow complexity of a manufacturing system from the control perspective is then investigated in terms of the human tasks and errors. A shop floor control example where a human operator performs material handling tasks is provided to illustrate the proposed model.     

A novel 0-1 linear integer programming model for dynamic machine-tool selection and operation allocation in a flexible manufacturing system

This paper considers a problem of dynamic machine-tool selection and operation allocation with part and tool movement policies in a flexible manufacturing system (FMS) environment. For this purpose, a novel 0-1 linear integer programming model is presented in such a way that each part and each tool can move during the production phase. It is assumed that there are a given set of tools and machines that can produce different kinds of orders (or part types). The objective of this model is to determine a machine-tool combination for each operation of the part type by minimizing some production costs, such as machining costs, setup costs, material handling costs and tool movement costs. In addition, due to the NP-hard nature of the problem, a new heuristic method based on five simple procedures (FSP) is proposed for solving the given problem, whose performance is tested on a number of randomly generated problems. The related results are compared with results obtained by a branch-and-bound method. It has been found that the proposed heuristic method gives good results in terms of objective function values and CPU times.     

Disruptive factors in the evaluation of perceived quality aspects – consideration of the brand influence

The implementation of evaluation methods with the aim to gain knowledge of the perceived quality aspects is a challenging task because of versatile disruptive factors on the users’ cognition. Commonly known disruptive factors like the different level of experience in the usage of a system or the publicity of a brand name are considered in research approaches only marginally. This becomes even more important when the evaluated system stays in direct interaction with the evaluator and an increase of external influences can be expected. On the example of a system with strong user interaction, a research approach for an objective evaluation of quality aspects was developed with cordless drills. An experiment has been carried out with 50 craftsmen which are divided into two groups, whereby the first of which will be given original labeled and the other blinded cordless drills for rating the application quality. Evaluation was divided into a preliminary test and a practical test phase, in which selected applications were performed. Results for the preliminary evaluation of the cordless drills indicate a significant brand influence with a strong positive effect on well-known (p<.001, r=0.492, +30.7%) and a negative effect on unknown brands (p=0.029, r=0.309, -17.2%). Practical usage of the devices leads to a significant change of ratings (well-know brand: p=0.007, r=0.378, +1.9%; unknown brand: p=0.053, r=0.274, +12%). Using paired sample t-test it can be shown that the practical use of cordless drills reduces variances in evaluation and ratings become more precise.Relevance for industry: Given approaches can be used in industry to conduct field studies with real users and benchmark systems to identify new development goals (quality aspects) for user-optimized products that are not affected by disruptive factors such as the brand name.     

A deadlock recovery strategy for unified automated material handling systems in 300 mm wafer fabrications

A key issue emerging from the unified automated material handling systems (UAMHSs) in 300 mm wafer fabrications is the system deadlock. This paper addresses the deadlock recovery strategy of unified automated material handling systems (UAMHSs) with limited buffers. A formal model for UAMHSs deadlock detection is proposed. Sufficient conditions for system deadlocks based on actual UAMHS characteristics are defined along with a novel deadlock recovery strategy. Moreover, an effective heuristic algorithm is proposed for parallel resolving UAMHS deadlocks. The performances are evaluated in simulation by monitoring indexes reflecting efficiency of the material handling system. Results of the simulation experiments show that the novel deadlock recovery strategy is superior to the benchmark strategy in reducing deadlock time and improving tools’ utilization. Furthermore, the proposed algorithm features real-time operation and large scale cases, and is suitable for practical applications.     

Design and Implementation of Electronic System and Computer Control of an Indexing Table and Quality Control Unit

Capability and meanwhile simplicity have stupendously expanded the area of application of linear controllers in the industrial applications, particularly the control of robotic arms, and other automated systems. The ultimate goal to accomplish this project is to show this capability in the frame of movement control of the arm of a quality control unit (side device), which forms a part of an automatic cell together with an indexing table. The fact that the existence of the gearbox, dramatically decreases the effects of non-linear dynamic of the arm to linear dynamic of the DC motor, justifies the idea of design and implementation a linear controller like Lead-Lag to control the quality control arm. Of course, we need to apply some other equipment like DC motor torque control system, sensors, and related interface circuits. In this article, it will be explained how the above goal will be accomplished by linear identification of the system with the method of step response identification and then digital implementation of the linear controller in computer and application of the arm motor torque control (Karami, J., Roohi, A., Design and implementation of electronic system and computer control of an indexing table and quality control unit. 2006 IEEE/ASME International Conference on Mechatronics and Embedded Systems and Applications, 2006).     

A decision support system for economic justification of material handling investments

This paper presents a decision support system for the economic justification of material handling investments. In particular it provides users with a formal mechanism to consider intangible or “soft” benefits associated with the investment in advanced material handling systems. The approach presented here is an extension to the work of Liggett and Sullivan [Engng. Economist, 37 (1992) 91] and Sullivan and Liggett [Manuf. Rev., 1 (1988) 151]. In addition to the development of the approach, we present a complete VisualBASIC program called JustMAT that serves as the implementation of the decision support system. The entire approach is illustrated with a numerical example.     

Hybrid discrete differential evolution algorithm for biobjective cyclic hoist scheduling with reentrance

Cyclic hoist scheduling problems in automated electroplating lines and surface processing shops attract many attentions and interests both from practitioners and researchers. In such systems, parts are transported from a workstation to another by a material handling hoist. The existing literature mainly addressed how to find an optimal cyclic schedule to minimize the cycle time that measures the productivity of the lines. The material handling cost is an important factor that needs to be considered in practice but seldom addressed in the literature. This study focuses on a biobjective cyclic hoist scheduling problem to minimize the cycle time and the material handling cost simultaneously. We consider the reentrant workstations that are usually encountered in real-life lines but inevitably make the part-flow more complicated. The problem is formulated as a biobjective linear programming model with a given hoist move sequence and transformed into finding a set of Pareto optimal hoist move sequences with respect to the bicriteria. To obtain the Pareto optimal or near-optimal front, a hybrid discrete differential evolution (DDE) algorithm is proposed. In this hybrid evolutional algorithm, the population is divided into several subpopulations according to the maximal work-in-process (WIP) level of the system and the sizes of subpopulations are dynamically adjusted to balance the exploration and exploitation of the search. We propose a constructive heuristic to generate initial subpopulations with different WIP levels, hybrid mutation and crossover operators, an evaluation method that can tackle infeasible individuals and a one-to-one greedy tabu selection method. Computational results on both benchmark instances and randomly generated instances show that our proposed hybrid DDE algorithm outperforms the basic DDE algorithm and can solve larger-size instances than the existing ε-constraint method.     

Inextensible elastic rods with torsional friction based on Lagrange multipliers

Elastic rods are thin flexible objects typically undergoing large non‐linear deformations that cannot be modeled with linear methods. They are used in a number of research fields, e.g., to represent hair or ropes in animations, or catheters or needles in medical simulations. In this paper, we propose a deformation model for inextensible elastic rods. The method of Lagrange multipliers is employed to enforce the inextensibility of the rod, and to couple the material frames with the centerline. The resulting system is banded, allowing for an efficient linear time solution. We also propose a manifold projection method to incorporate the non‐penetration constraints resulting from contact handling into our constrained Lagrangian mechanics (CLM) problem. We further augment the contact model by treating torsional friction. This allows to reproduce friction effects such as dynamic rolling and twisting of rods. Various examples underline the benefits and applicability of our model. Copyright © 2010 John Wiley & Sons, Ltd.     

Implementing a hybrid simulation model for a Kanban-based material handling system

Plant floor material handling is a loose loop in most assembly plants. Simulation offers a quick, controllable and tunable approach for prototyping complex material handling processes in manufacturing environments. This paper proposes a hybrid simulation approach, using both discrete event and agent-based technologies, to model complex material handling processes in an assembly line. A prototype system is implemented using a commercial multi-paradigm modeling tool. In this prototype, JIT principles are applied to both the production and the material handling processes. The system performance is evaluated and system optimization directions are suggested. The proposed hybrid modeling approach facilitates the implementation of a responsive and adaptive environment in that various “what-if” scenarios can be simulated under different simulation configurations and real-time situations.     

Design and simulation of an ultrasonic linear motor with dual piezoelectric actuators

In this study, an ultrasonic linear motor with dual piezoelectric (PZT) actuators is developed. A traveling wave motion is generated on the stator by a double-sided excitation of the stator of the ultrasonic linear motor, which drives the slider that is connected to the stator. The development and design processes are described. In this paper, the principle of using an ultrasonic motor to drive a traveling wave type is presented. The structure for the ultrasonic linear motor is then demonstrated with its dimensions, driving conditions and material parameters, so that Computer-Aided Engineering (CAE) can be used to simulate the driving performance. The simulation results show the differences to the characteristics that are achieved by adjusting the critical parameters, such as the PZT boned positions, the excitation frequency and the preload, in order to derive the best design. A prototype that uses the best parameter design is presented, and a method to improve development processes is presented in the final section.

     

A proactive material handling method for CPS enabled shop-floor

Cyber physical system (CPS) enables companies to keep high traceability and controllability in manufacturing for better quality and improved productivity. However, several challenges including excessively long waiting time and a serious waste of energy still exist on the shop-floor where limited buffer exists for each machine (e.g., shop-floor that manufactures large-size products). The production logistics tasks are released after work-in-processes (WIPs) are processed, and the machines will be occupied before trolleys arrival when using passive material handling strategy. To address this issue, a proactive material handling method for CPS enabled shop-floor (CPS-PMH) is proposed. Firstly, the manufacturing resources (machines and trolleys) are made smart by applying CPS technologies so that they are able to sense, act, interact and behave within a smart environment. Secondly, a shop-floor digital twin model is created, aiming to reflect their status just like real-life objects, and key production performance indicators can be analysed timely. Then, a time-weighted multiple linear regression method (TWMLR) is proposed to forecast the remaining processing time of WIPs. A proactive material handling model is designed to allocate smart trolleys optimally. Finally, a case study from Southern China is used to validate the proposed method and results show that the proposed CPS-PMH can largely reduce the total non-value-added energy consumption of manufacturing resources and optimize the routes of smart trolleys.     

单片机技术在无绳电话中的应用

介绍了作者自行设计的多信道无绳电话单片机系统,包括手座机系统原理、软件流程及接口电路。该系统采用软件法产生ＤＴＭＦ（Ｄｕａｌｔｏｎｅｍｕｌｔｉｐｌｅｆｒｅｑｕｅｎｃｙ）信号,间歇式通断手机待机电源,１０个信道手工选择,充电瞬间手座机自动设定密码,手机电池低压告警,手座机可双向呼叫,具有成本低、工作可靠性好、耗电少、待机时间长（达７２ｈ）等特点。     

Effects of pacing when using material handling manipulators.

Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required approximately 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in approximately 10% higher spine forces and approximately 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.     

二维直线电机的多入多出无模型自适应轮廓控制

针对传统的单入单出控制器无法解决二维直线电机存在的非线性,不确定性以及强耦合作用等问题,依据无模型自适应控制不依赖于被控系统精确数学模型,仅需受控系统输入输出数据便能实现自适应控制这一特点,采用多入多出的紧格式动态线性化无模型自适应控制算法对二维直线电机XY轴进行整体控制器设计.同时,针对二维直线电机这种含有纯二阶积分环节的非自平衡系统,提出了多入多出无模型自适应控制改良方法,并进行严格的稳定性和收敛性证明.为了提高二维直线电机的轮廓精度,在多入多出无模型自适应控制改良方法的基础上,加入交叉耦合控制器,与传统的交叉耦合控制方法相比较,提高了跟踪精度和轮廓精度.最后通过仿真和实物实验证明了所提方案的有效性.     

Data-driven nonparametric model adaptive precision control for linear servo systems

Nowadays, high-precision motion controls are needed in modern manufacturing industry. A data-driven nonparametric model adaptive control (NMAC) method is proposed in this paper to control the position of a linear servo system. The controller design requires no information about the structure of linear servo system, and it is based on the estimation and forecasting of the pseudo-partial derivatives (PPD) which are estimated according to the voltage input and position output of the linear motor. The characteristics and operational mechanism of the permanent magnet synchronous linear motor (PMSLM) are introduced, and the proposed nonparametric model control strategy has been compared with the classic proportional-integral-derivative (PID) control algorithm. Several real-time experiments on the motion control system incorporating a permanent magnet synchronous linear motor showed that the nonparametric model adaptive control method improved the system’s response to disturbances and its position-tracking precision, even for a nonlinear system with incompletely known dynamic characteristics.