托盘共用系统托盘回收随机规划模型研究

介绍了托盘共用系统的研究现状,并在现有托盘共用系统的基础上,提出一个改进的托盘共用系统.基于改进的托盘共用系统,建立了托盘共用系统托盘回收随机规划模型,模型中考虑了需求和运输能力不确定等因素,采用机会约束规划方法对模型进行了确定性等价转换.通过算例进行了数值求解和数值分析,验证了模型的有效性,得出了一些有意义的结论.     

托盘共用系统调度两阶段随机机会约束规划模型研究

根据托盘共用系统调度的特点,建立了以托盘共用系统调度总成本最小为目标的两阶段随机机会约束规划模型．该模型综合考虑了需求随机、供给随机、运输能力随机、装卸能力随机等因素;采用机会约束规划方法对模型进行了确定性等价转换;通过算例进行了数值求解和数值分析,验证了模型的可行性和有效性．     

共用模式下的空托盘调配决策方案优化研究

共用模式下合理的空托盘调配能够提高托盘的利用率、降低运输成本、减少资源浪费。基于托盘共用模式,以公路和铁路运输为主要运输方式对空托盘调配决策方案进行优化研究。对空托盘调配的运输网络的节点进行拆分,细化节点处的作业模式。综合考虑各种影响空托盘调运的因素,针对实际运输特点,以包括装运费用、库存费用和租赁费用在内的总的调配费用最小为目标构建优化模型,同时结合客户对空托盘的时间约束构建路径运送时间优化模型。利用ILOG Cplex数学优化软件对模型求解。最后通过算例分析验证了共用模式下该模型的可行性及优越性。     

带有模糊参数的应急物资筹集问题决策模型

应急物资筹集决策是应急物流系统重要研究问题之一,是继应急物资需求预测之后的一项重要应急物资管理活动,它直接关系到应急物流目标的实现。建立了仅动用库存条件下应急物资筹集决策模糊优化模型,利用模糊机会约束规划的思想,给出了与其等价的模糊机会约束规划模型,在此基础上提出了应急物资筹集决策模型的算法,最后通过算例说明了该方法的有效性。     

应用带补偿的机会约束规划策略优化精馏过程的研究

精馏过程优化存在许多不确定变量,其对优化结果的影响是不可忽略的,所以需要找到真实反映不确定变最的数学模型,找到最优的求解方法得到精确解,进而得到最优的优化结果.本研究通过分析随机规划策略和不确定因素的特性及其对精馏优化过程的影响,对不确定因素进行分类,应用带补偿的随机规划和机会约束规划实现不确定因素对优化目标和约束的影响.对于模型中的机会约束,由于不确定输入变量和不确定输出变量间存在单调关系,所以可以通过对不确定输入变量的多重积分将机会约束转化为等价地确定性非线性约束,此时模型转化为含有非线性约束的带补偿的随机规划模型,此模型通过改进的蒙特卡罗(Monte Carlo)积分和含有序列2次规划(SQP)的Benders分解相结合的混合算法有效的求解.所提出的求解方法借助于Matlab软件能够得到比较精确的结果.采用本文所提出的模型及求解方法对精馏塔操作的模拟实验过程进行优化研究,可以看出带补偿的机会约束规划模型能够很好地反映不确定变量对优化过程的影响.所以本文提出的模型和求解方法是有效可行的,且对于以后的不确定优化研究具有很好的指导意义.     

基于可能性理论的模糊支持向量分类机

研究模糊支持向量分类机的构建问题.其特点是:训练点输出的类型和最终的模糊分类函数的函数值均为三角模糊数.首先,以模糊事件的可能性测度为基础,将模糊分类问题转化为求解模糊机会约束规划问题.然后,利用模糊机会约束规划化为清晰等价规划的方法,将其转化为与其等价的二次规划.据此给出模糊支持向量分类机(算法).同时用一个简单算例说明该算法的合理性.     

新零售下生鲜产品闭环物流网络模糊规划

针对我国新零售模式的快速发展，消费者对生鲜产品需求与退货的模糊不确定性问题，考虑最低物流总成本、最佳设施选址以及最优配送车辆运输路径的决策，构建了新零售下生鲜产品闭环物流网络模糊规划模型。为求解该模型，将需求量与退货量看成三角模糊参数，利用模糊机会约束方法将模糊约束转化为等价的清晰条件。以上海市某生鲜电商企业为实例，通过置信水平的敏感性分析以及遗传算法与粒子群算法的双求解，验证了模型的有效性与可行性，进而为相关决策者提供了借鉴。     

同尺寸物品托盘装载的动态规划算法

对同尺寸物品托盘装载问题,提出一种动态规划算法。本文将三维托盘装载问题转化为一系列的二维排样问题来求解。通过对动态规划算法的研究,设计出了适合同尺寸物品的三维托盘装载的算法,并通过实验证明了算法的有效性。     

模糊环境下多周期多决策生鲜闭环物流网络

针对生鲜品因易腐易损性而产生的高频次物流配送及不确定需求与退货量的问题，提出了模糊环境下多周期生鲜闭环物流网络系统，以实现最小系统成本、最优设施选址与最佳配送路径的多决策安排。为求解系统对应的模糊混合整数线性规划（FMILP）模型，首先将生鲜需求量和退货量设定为三角模糊值，其次运用模糊机会约束规划方法将模糊约束等价变换为清晰式，最后利用遗传算法（GA）和粒子群优化（PSO）算法搜索案例的最优解。实验结果表明，多周期闭环系统比单周期更能兼顾多决策规划，同时三角模糊量的置信水平变化对企业最优运作有着显著影响，进而为相关决策者提供借鉴。     

含有模糊和随机参数的混合机会约束规划模型

提出一类混合机会约束规划模型，该模型同时含有模糊和随机参数，运用随机模拟与模糊模拟相结合的技术，给出了求解该机会约束规划模型的遗传算法，通过对生产过程最优化决策的典型问题进行分析建模和数值求解，说明了该模型和算法的合理性和有效性。     

Automatic visual guidance of a forklift engaging a pallet

This paper presents the development of a prototype vision-guided forklift system for the automatic engagement of pallets. The system is controlled using the visual guidance method of mobile camera-space manipulation, which is capable of achieving a high level of precision in positioning and orienting mobile manipulator robots without relying on camera calibration. The paper contains development of the method, the development of a prototype forklift as well as experimental results in actual pallet engagement tasks. The technology could be added to AGV systems enabling them to engage arbitrarily located pallets. It also could be added to standard forklifts as an operator assist capability.     

The effects of operator position,pallet orientation,and palletizing condition on low back loads in manual bag palletizing operations

Many mining commodities are packaged and shipped using bags. Small bags are typically loaded onto pallets for transport and require a significant amount of manual handling by workers. This specific task of manual bag handling has been associated with the development of musculoskeletal disorders (MSDs), especially low back disorders. This study evaluates the biomechanical demands of different work layouts when performing manual palletizing of small bags, and evaluates the biomechanical stresses associated with different stacking techniques. Results indicate that peak forward bending moments as well as spinal compression and shear forces are higher when the pallet is situated at the side of the conveyor as opposed to the end of the conveyor. At low levels of the pallet, controlled bag placement results in higher peak forward bending moments than stacking at higher levels and when dropping the bag to lower levels. The results of this study will be used to inform the development of an audit tool for bagging operations in the mining industry.Relevance to industryIn many cases for workers loading small bags, compression forces exceed the NIOSH criterion of 3400 N. Orientation of the pallet has a significant impact on spinal compression, and positioning the pallet at the end of the conveyor reduces the estimated compressive loading on the lumbar spine by approximately 800 N.     

A computer vision assisted system for autonomous forklift vehicles in real factory environment

Industry 4.0 is an important trend in factory automation nowadays. Among the Automated-Storage-and-Retrieval-System (ASRS) is one of the most important issues for industry. It is widely used in a variety of industries for a variety of storage applications in factories and warehouses. However, the cost of constructing an ASRS is so high that most small/medium enterprises cannot afford it. A forklift system is a cheaper alternative to a complicated ASRS. In this work, a new pallet detection method that uses an Adaptive Structure Feature (ASF) and Direction Weighted Overlapping (DWO) ratio to allow forklifts to pick up a pallet is proposed, using a monocular vision system on the forklift. Combining the ASF and DWO ratio for pallet detection, the proposed method removes most of the non-stationary (dynamic) background and significantly increases the processing efficiency. A Haar like-based Adaboost scheme uses an AS for pallets algorithm to detect pallets. It detects the pallet in a dark environment. Finally, by calculating the DWO ratio between the detected pallets and tracking records, it avoids erroneous candidates during object tracking. Therefore, this work improves the pallet detection to solve the problem with an effective design. As results show that the hybrid algorithms that are proposed in this work increase the average pallet detection rate by 95 %.     

Electromagnetic modular Smart Surface architecture and control in a microfactory context

This paper presents an electromagnetic conveyance system called electromagnetic modular Smart Surface (emSS) permitting to move pallets on a planar surface in a microfactory context. The proposed surface concept allows flexibility in reconfiguring the system layout along with product routing. The possibilities of accurate positioning of the moving pallet and controlling multiple pallets on the surface make the emSS suitable for reconfigurable and flexible manufacturing systems. However, the emSS control needs to be robust and scalable to adapt the changes in manufacturing systems. A framework is therefore defined to monitor and control the emSS by simulation or in-line. It allows to define product routing on the emSS by satisfying numerous requirements such as reduction in energy consumption, collision avoidance, etc., and to minimize the human interventions by changing product routing when emSS component failures occur. A first experiment realized on an emSS prototype, allowed to compare two paths strategies regarding cost function linked to energy consumption and velocities. Two other studies exploit the emSS modeling in terms of pallet path generation and simulation of collision avoidance.     

Detection,localisation and tracking of pallets using machine learning techniques and 2D range data

The problem of autonomous transportation in industrial scenarios is receiving a renewed interest due to the way it can revolutionise internal logistics, especially in unstructured environments. This paper presents a novel architecture allowing a robot to detect, localise, and track (possibly multiple) pallets using machine learning techniques based on an on-board 2D laser rangefinder only. The architecture is composed of two main components: the first stage is a pallet detector employing a Faster Region-Based Convolutional Neural Network (Faster R-CNN) detector cascaded with a CNN-based classifier; the second stage is a Kalman filter for localising and tracking detected pallets, which we also use to defer commitment to a pallet detected in the first stage until sufficient confidence has been acquired via a sequential data acquisition process. For fine-tuning the CNNs, the architecture has been systematically evaluated using a real-world dataset containing 340 labelled 2D scans, which have been made freely available in an online repository. Detection performance has been assessed on the basis of the average accuracy over k-fold cross-validation, and it scored 99.58% in our tests. Concerning pallet localisation and tracking, experiments have been performed in a scenario where the robot is approaching the pallet to fork. Although data have been originally acquired by considering only one pallet as per specification of the use case we consider, artificial data have been generated as well to mimic the presence of multiple pallets in the robot workspace. Our experimental results confirm that the system is capable of identifying, localising and tracking pallets with a high success rate while being robust to false positives.

     

Generating pallet loading patterns with considerations of item stacking on end and side surfaces

In late 1979 a two phase heuristic algorithm employing dynamic programming was presented by Steudel for solving the two-dimensional cutting stock problem where all the small rectangles were of the same dimensions, but withour any restrictions that the cutting be performed in a purely “guillotine” fashion. The algorithm was applied to solving the common problem of loading rectangular items of size l by w on a rectangular pallet of size L and W so as to maximize the number of items per layer on the pallet deckboard. In this paper, a new three-phase heuristic is presented which extends the 1979 recursive procedure and evaluates the option of stacking items on their end and/or side surface within the best loading pattern of bottom-stacked items. The resulting pattern is then projected into the third dimension to generate the total “cubic” pallet load. Computation results show that end and/or side stacking (when applicable) can yield average improvements in the range of 5% in items per pallet load.     

Ergonomic evaluation of standard and alternative pallet jack handless

AimTransportation of materials using a pallet jack pulled behind the operator is common due to the visual advantages while transporting fully loaded pallets. The objective of this laboratory study was to quantify muscle activity, posture, and low back compressive and shear forces while completing typical pallet jack activities using a standard handle that required one handed pulling of a pallet jack compared to an alternative handle that allowed for two handed pushing.MethodsParticipants (n = 14) performed six to ten trials of common pallet jack tasks (straight travel and turning) with each handle. Posture analysis of the trunk and right upper extremity was performed using Motion Analysis (Santa Rosa, CA, USA) and back compressive and shear forces were analyzed using 3D Static Strength Prediction Program (University of Michigan, Ann Arbor, MI). Activity of the upper trapezius (UT), pectoralis major (PM), flexor digitorum superficialis (FDS) and extensor digitorum (ED) muscles were recorded (Telemyo 2400 T, Noraxon, Scottsdale, Arizona) and normalized to percent reference voluntary contraction values. All outcomes were compared using the paired t-test.ResultsPeak and mean muscle activity of the PM (p < 0.001) and ED (p < 0.01) were significantly higher using the alternative push handle during all three tasks. There were larger compressive forces at L4/L5 (p < 0.08) and L5/S1 (p < 0.002) using the alternative handle, and greater shear forces using the standard handle at both L4/L5 (p < 0.0001) and L5/S1 (p < 0.000).DiscussionThe standard handle outperformed the alternative handle with regard to muscle activity. The alternative handle had significantly greater compressive forces at L5/S1 due to the pushing nature of the hand-handle interface, yet the standard handle increased shear forces at both L4/L5 and L5/S1 levels in the low back.ConclusionIn this analysis, there was not a clear benefit to using either handle in terms of trunk strength capacity and varied benefits and drawbacks to each handle when comparing compressive and shear forces in the low back. However, given favorable subjective reports described in a prior publication, and the increased reliance on dynamic versus passive force production, facilitating a workers' ability to push a pallet jack while travelling with large loads is worth further investigation.     

Modeling and analysis of closed loop manufacturing systems using parameter coupling

Closed loop manufacturing systems (CLMSs) with recirculating material handling devices are extensively used in various industrial environments. The performance of such systems is impacted by many factors such as the total capacity of pallets, the actual number of pallets in the system, the machine reliability and processing time, the pallet index speed, and the positions of loading/unloading points. These factors make the accurate analysis and optimization of complex CLMSs very difficult and challenging. This paper presents a new parameter coupling technique to model and analyze a wide range of CLMSs. It is an enhancement based on the existing open production line analysis with unreliable assembly machines and finite buffers. Virtual assembly machines are introduced to represent the specific phenomena of CLMSs such as the recirculation of empty pallets and the sharing of conveyor space. Two types of parameter coupling patterns, the machine parameter coupling, and the buffer capacity coupling, are introduced to reflect the characteristics of the CLMSs. The parameter coupling technique is simple and effective for analyzing a broad range of CLMSs. Comparisons between this analytic method and simulation experiments demonstrate that the proposed parameter coupling technique is fast, accurate and robust.