Product variation reduction is critical to improve process efficiency and product quality, especially for multistage machining process（MMP）. However, due to the variation accumulation and propagation, it becomes qui...Product variation reduction is critical to improve process efficiency and product quality, especially for multistage machining process（MMP）. However, due to the variation accumulation and propagation, it becomes quite difficult to predict and reduce product variation for MMP. While the method of statistical process control can be used to control product quality, it is used mainly to monitor the process change rather than to analyze the cause of product variation. In this paper, based on a differential description of the contact kinematics of locators and part surfaces, and the geometric constraints equation defined by the locating scheme, an improved analytical variation propagation model for MMP is presented. In which the influence of both locator position and machining error on part quality is considered while, in traditional model, it usually focuses on datum error and fixture error. Coordinate transformation theory is used to reflect the generation and transmission laws of error in the establishment of the model. The concept of deviation matrix is heavily applied to establish an explicit mapping between the geometric deviation of part and the process error sources. In each machining stage, the part deviation is formulized as three separated components corresponding to three different kinds of error sources, which can be further applied to fault identification and design optimization for complicated machining process. An example part for MMP is given out to validate the effectiveness of the methodology. The experiment results show that the model prediction and the actual measurement match well. This paper provides a method to predict part deviation under the influence of fixture error, datum error and machining error, and it enriches the way of quality prediction for MMP.展开更多
This paper investigates State Space Model Predictive Control (SSMPC) of an aerothermic process. It is a pilot scale heating and ventilation system equipped with a heater grid and a centrifugal blower, fully connected ...This paper investigates State Space Model Predictive Control (SSMPC) of an aerothermic process. It is a pilot scale heating and ventilation system equipped with a heater grid and a centrifugal blower, fully connected through a data acquisition system for real time control. The interaction between the process variables is shown to be challenging for single variable controllers, therefore multi-variable control is worth considering. A multi-variable state space model is obtained from on-line experimental data. The controller design is translated into a Quadratic Programming (QP) problem, in which a cost function subject to actuators linear inequality constraints is minimized. The outcome of the experimental results is that the main control objectives, such as set-point tracking and perturbations rejection under actuators constraints, are well achieved for both controlled variables simultaneously.展开更多
半导体设备是芯片制造的核心单元,承担光刻、刻蚀、薄膜沉积等关键工艺,其调度效率直接影响晶圆产能与工厂效益,设计出一个高效稳定的调度系统是保证最优产能的前提。然而,一方面,高精度、多环节的晶圆加工步骤使设备调度系统设计难度提...半导体设备是芯片制造的核心单元,承担光刻、刻蚀、薄膜沉积等关键工艺,其调度效率直接影响晶圆产能与工厂效益,设计出一个高效稳定的调度系统是保证最优产能的前提。然而,一方面,高精度、多环节的晶圆加工步骤使设备调度系统设计难度提升;另一方面,设备内对晶圆的调度效率会影响产能,导致对系统计算效率的要求较高。传统的调度设计方法往往基于遗传算法在解空间上搜索最优解,难以满足系统的实时性需求。文中设计通过对双集束型晶圆加工半导体设备中的出片限制、模块使用限制、禁止超片、阀门互斥限制、Just in Time共5个调度限制进行系统性分析,创新性地将加工仓任务池、机械臂任务池的任务调度问题抽象为混合整数规划(MIP)模型,并且基于数学规划求解器Gurobi进行快速求解,相较于传统算法求解速度提升了一个数量级。展开更多
We focuse on design process in concurrent engineering and propose an, approach to collaborative design based on distributed constraint-net. The approach adopts agent technology to express kinds of distributed constrai...We focuse on design process in concurrent engineering and propose an, approach to collaborative design based on distributed constraint-net. The approach adopts agent technology to express kinds of distributed constraints. And through the cooperation among agents, the consistency of constraint is maintained and the constraint conflict is detected and eliminated. The constraints are satisfied concurrently and distributively. Based on the proposed approach, the collaborative design process in concurrent engineering can be well supported.展开更多
Identifying each process and their constraint relations from the complex wiring harness drawings quickly and accurately is the basis for formulating process routes. According to the knowledge of automotive wiring harn...Identifying each process and their constraint relations from the complex wiring harness drawings quickly and accurately is the basis for formulating process routes. According to the knowledge of automotive wiring harness and the characteristics of wiring harness components, we established the model of wiring harness graph. Then we research the algorithm of identifying technology processes automatically, finally we describe the relationships between processes by introducing the constraint matrix, which is in or- der to lay a good foundation for harness process planning and production scheduling.展开更多
Scarce resources,precedence and non-determined time-lag are three constraints commonly found in small and medium manufacturing enterprises(SMEs),which are deemed to block the application of workflow management system(...Scarce resources,precedence and non-determined time-lag are three constraints commonly found in small and medium manufacturing enterprises(SMEs),which are deemed to block the application of workflow management system(WfMS). To tackle this problem,a workflow scheduling approach is proposed based on timing workflow net(TWF-net) and genetic algorithm(GA). The workflow is modelled in a form of TWF-net in favour of process simulation and resource conflict checking. After simplifying and reconstructing the set of workflow instance,the conflict resolution problem is transformed into a resource-constrained project scheduling problem(RCPSP),which could be efficiently solved by a heuristic method,such as GA. Finally,problems of various sizes are utilized to test the performance of the proposed algorithm and to compare it with first-come-firstserved(FCFS) strategy. The evaluation demonstrates that the proposed method is an overwhelming and effective approach for scheduling the concurrent processes with precedence and resource constraints.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51205286,51275348)
文摘Product variation reduction is critical to improve process efficiency and product quality, especially for multistage machining process（MMP）. However, due to the variation accumulation and propagation, it becomes quite difficult to predict and reduce product variation for MMP. While the method of statistical process control can be used to control product quality, it is used mainly to monitor the process change rather than to analyze the cause of product variation. In this paper, based on a differential description of the contact kinematics of locators and part surfaces, and the geometric constraints equation defined by the locating scheme, an improved analytical variation propagation model for MMP is presented. In which the influence of both locator position and machining error on part quality is considered while, in traditional model, it usually focuses on datum error and fixture error. Coordinate transformation theory is used to reflect the generation and transmission laws of error in the establishment of the model. The concept of deviation matrix is heavily applied to establish an explicit mapping between the geometric deviation of part and the process error sources. In each machining stage, the part deviation is formulized as three separated components corresponding to three different kinds of error sources, which can be further applied to fault identification and design optimization for complicated machining process. An example part for MMP is given out to validate the effectiveness of the methodology. The experiment results show that the model prediction and the actual measurement match well. This paper provides a method to predict part deviation under the influence of fixture error, datum error and machining error, and it enriches the way of quality prediction for MMP.
文摘This paper investigates State Space Model Predictive Control (SSMPC) of an aerothermic process. It is a pilot scale heating and ventilation system equipped with a heater grid and a centrifugal blower, fully connected through a data acquisition system for real time control. The interaction between the process variables is shown to be challenging for single variable controllers, therefore multi-variable control is worth considering. A multi-variable state space model is obtained from on-line experimental data. The controller design is translated into a Quadratic Programming (QP) problem, in which a cost function subject to actuators linear inequality constraints is minimized. The outcome of the experimental results is that the main control objectives, such as set-point tracking and perturbations rejection under actuators constraints, are well achieved for both controlled variables simultaneously.
文摘半导体设备是芯片制造的核心单元,承担光刻、刻蚀、薄膜沉积等关键工艺,其调度效率直接影响晶圆产能与工厂效益,设计出一个高效稳定的调度系统是保证最优产能的前提。然而,一方面,高精度、多环节的晶圆加工步骤使设备调度系统设计难度提升;另一方面,设备内对晶圆的调度效率会影响产能,导致对系统计算效率的要求较高。传统的调度设计方法往往基于遗传算法在解空间上搜索最优解,难以满足系统的实时性需求。文中设计通过对双集束型晶圆加工半导体设备中的出片限制、模块使用限制、禁止超片、阀门互斥限制、Just in Time共5个调度限制进行系统性分析,创新性地将加工仓任务池、机械臂任务池的任务调度问题抽象为混合整数规划(MIP)模型,并且基于数学规划求解器Gurobi进行快速求解,相较于传统算法求解速度提升了一个数量级。
基金Supported by the National Natural Science F oundation of China( No.5 9875 0 2 5 )
文摘We focuse on design process in concurrent engineering and propose an, approach to collaborative design based on distributed constraint-net. The approach adopts agent technology to express kinds of distributed constraints. And through the cooperation among agents, the consistency of constraint is maintained and the constraint conflict is detected and eliminated. The constraints are satisfied concurrently and distributively. Based on the proposed approach, the collaborative design process in concurrent engineering can be well supported.
基金Supported by Chinese national Science Foundation (61070124)the Fundamental Research Funds for the Central Universities (2012HGBZ0195)
文摘Identifying each process and their constraint relations from the complex wiring harness drawings quickly and accurately is the basis for formulating process routes. According to the knowledge of automotive wiring harness and the characteristics of wiring harness components, we established the model of wiring harness graph. Then we research the algorithm of identifying technology processes automatically, finally we describe the relationships between processes by introducing the constraint matrix, which is in or- der to lay a good foundation for harness process planning and production scheduling.
基金Supported by the Postdoctoral Science Foundation of China(No.2015M572022)the National Natural Science Foundation of China(No.51175304)
文摘Scarce resources,precedence and non-determined time-lag are three constraints commonly found in small and medium manufacturing enterprises(SMEs),which are deemed to block the application of workflow management system(WfMS). To tackle this problem,a workflow scheduling approach is proposed based on timing workflow net(TWF-net) and genetic algorithm(GA). The workflow is modelled in a form of TWF-net in favour of process simulation and resource conflict checking. After simplifying and reconstructing the set of workflow instance,the conflict resolution problem is transformed into a resource-constrained project scheduling problem(RCPSP),which could be efficiently solved by a heuristic method,such as GA. Finally,problems of various sizes are utilized to test the performance of the proposed algorithm and to compare it with first-come-firstserved(FCFS) strategy. The evaluation demonstrates that the proposed method is an overwhelming and effective approach for scheduling the concurrent processes with precedence and resource constraints.
