Estimating the throughput of a cyclic assembly system

We consider a production system consisting of several fabrication lines feeding an assembly station. The machines in the fabrication lines and at assembly are assumed to have general processing time distributions. Releases to the system are governed by the CONWIP protocol. We model this system as an assembly-like queue and develop approximations for the throughput of the system. Comparisons with simulations show that this approximation is robust over a wide range of conditions. Finally, we observe that throughput tends to be higher when machines with higher mean processing times and/or higher variances are in fabrication rather than assembly.     

Estimating the parameters of semiconductor optical-feedback lasers from time series

A new method is proposed for estimating the control parameters of single-mode semiconductor optical-feedback lasers from experimentally measured time series of the laser intensity. The procedure is based on a statistical analysis of specially selected points of the time series and on the phenomenon of chaotic synchronization of unidirectionally coupled lasers with coinciding parameters.     

Estimating the stability of a complicated system on repeated loading

An approach is proposed to determining the stability of a complicated engineering system under conditions of unregulated effects of destabilizing factors. Forms are obtained for the probability of retaining viability, which allow one to incorporate the repeated action of the destabilizing factors no matter what their differing physical natures. Translated from Izmeritel’naya Tekhnika, No. 2, pp. 17–19, February, 2009.     

On the choice of a production control system

This paper deals with a problem to develop ‘factory automation systems’ which harmonize companies’ needs with workers’ desires. Two kinds of indices and methods of survey are proposed on the basis of the ‘fusion system concept’. One is that of the state of workers’ desires which are based on the ‘stimulus-response model’, the other is that of situations where ‘factory automation’ is implemented in a workshop. The effects of ‘factory automation’ on workers’ desires are clarified in a study of Japanese manufacturing industries in 1983. As a result of this investigation, some problems can be pointed out which should be solved in the future to develop ‘factory automation systems’.     

Component testing of a series system in a random mission

Components of a series system are tested in order to assure desired levels of system reliability during the mission. The components are nonidentical but they all fail exponentially with failure rates that depend on the mission performed. There is a given set of missions that the device can be assigned randomly with respect to a given probability distribution. This directly implies that the failure rates of the components depend on the specific mission that the device performs. The objective is to find an optimal component test plan. We will show that, with some extra effort, this rather complicated but realistic model can be handled using available results in semi-infinite linear programming and d.c. (difference of convex functions) programming.     

Analysis of the receiver response for a noncoaxial lidar system with fiber-optic output

The return signal of a noncoaxial lidar system with fiber-optic output is examined. The dependence of the overlap regions and the overlap factor of the system on the fiber diameter is calculated for several inclination angles between the laser beam and the optical receiver axes. The effect of central obstruction is included and both cases of Gaussian and quasi-Gaussian laser beam profiles are treated. The irradiance spatial distribution on the focal plane of the system is calculated and experimentally determined. Finally, an alignment procedure of the lidar system is described based on the comparison between the range-corrected lidar signal and the range-corrected exponentially attenuated Rayleigh backscattered coefficient.     

A note on 'deliberately slowing down output in a family production context'

In this paper, we consider the economic lot scheduling problem with controllable production rates and imperfect quality. The problem is to schedule the production of several different items in the same facility on a repetitive basis. The facility is such that only one item can be produced at a time and the demand rate for each item is constant over an infinite planning horizon. We focus on the case where quality is imperfect and yield rates decrease with increased production rates and lot sizes. We show that the resulting lot sizes under the proposed extension are smaller. Also, we show that the production rates for some products can be considerably different from the case of perfect quality.     

Integrated maintenance and production control of a deteriorating production system

We consider a make-to-stock production/inventory system consisting of a single deteriorating machine which produces a single item. We formulate the integrated decisions of maintenance and production using a Markov Decision Process. The optimal dynamic policy is shown to have a rather complex structure which leads us to consider more implementable policies. We present a double-threshold policy and derive exact and approximate methods for evaluating the performance of this policy and computing its optimal parameters. A detailed numerical study demonstrates that the proposed policy and our approximate method for computing its parameters perform extremely well. Finally, we show that policies which do not address maintenance and production control decisions in an integrated manner can perform rather badly.     

Increasing the production rate of a just-in-time production system with variable operation times

This paper examines a just-in-time (JIT) system with kanbans with three subassembly lines feeding a final assembly station. Variability in operation times exists and variability effects are reduced by increasing work in process levels or by unbalancing the subassembly lines through assignment of work content at each station. Of the several unbalancing methods that were analysed in this study, only the high-medium-low showed a consistent improvement in the output rate of the JIT production system. The output rates with unbalanced stations were always superior to the output rate of the perfectly balanced configurations used as controls. The extent of improvement over the output rate of balanced systems increased directly with the variability in operation times in final assembly and subassembly stations and inversely with the interstage buffer capacity allowed in the system.     

一类输出时滞系统的振动主动控制方法研究

为实施一类受复杂外扰作用结构系统的低频振动控制,相应的控制系统需引入高阶低通滤波器来消除输出测量中的噪声和高频干扰,以避免观测溢出,从而形成了含输出时滞的受控振动系统.为补偿该类滤波器带来的时滞影响,提出了考虑输出时滞的最优控制方法.首先采用Moore-Penrose广义逆求解方法将含有输出时滞的系统方程转换为对应的输入输出描述形式;然后利用扩维方法将含时滞的系统转换为不显含时滞的系统,并采用传统的LQ方法设计相应的控制律.最后以实际风洞测力试验模型的低频主动减振为研究背景,进行相应的数值仿真和实验验证.结果表明,该方法能有效抑制这类输出时滞系统的低频振动.同时确保输出信号中的高频成分和噪声干扰得到很大程度的衰减,有效避免了控制器的观测溢出问题.     

Estimating delay from a dynamical system response to a weak pulsed action

A new method is proposed for estimating the delay time of a delayed-feedback system, which is based on an analysis of the system response to a weak external perturbation in the form of rectangular pulses. The method is applicable to systems that perform both periodic and chaotic oscillations. The efficiency of the proposed procedure is demonstrated based on numerical examples and for the experimental time series of a real radiophysical system.     

Optoelectronic neural system for processing the output data from a fiber-optic measuring network

The results of an investigation of an optoelectronic neural system for processing the output data from a distributed fiber-optic tomographic-type measuring network are reported. The processing system is based on the operation principle of an optical perceptron in which the interneuron coupling matrix is implemented using a collection of amplitude holograms recorded on a disk-shaped holographic carrier. It is shown experimentally that this system makes it possible to reconstruct to within 20% the spatial distribution functions of the physical quantity under investigation. Pis’ma Zh. Tekh. Fiz. 25, 65–70 (March 26, 1999)     

Estimating primary production at depth from remote sensing

By use of a common primary-production model and identical photosynthetic parameters, four different methods were used to calculate quanta (Q) and primary production (P) at depth for a study of high-latitude North Atlantic waters. The differences among the four methods relate to the use of pigment information in the upper water column. Methods 1 and 2 use pigment biomass (B) as an input and a subtropical, empirical relation between K(d) (diffuse attenuation coefficient) and B to estimate Q at depth. Method 1 uses measured B, but Method 2 uses B derived from the Coastal Zone Color Scanner (subtropical algorithm) as inputs. Methods 3 and 4 use the phytoplankton absorption coefficient (a(ph)) instead of B as input, and Method B uses empirically derived a(ph)(440) and K(d) values, and Method 4 uses analytically derived a(ph)(440) and a (total absorption coefficient) values based on the same remote measurements as Method 2. When the calculated and the measured values of Q(z) and P(z) were compared, Method 4 provided the closest results [for P(z), r(2) = 0.95 (n = 24), and for Q(z), r(2) = 0.92 (n = 11)]. Method 1 yielded the worst results [for P(z), r(2) = 0.56 and for Q(z), r(2) = 0.81]. These results indicate that one of the greatest uncertainties in the remote estimation of P can come from a potential mismatch of the pigment-specific absorption coefficient (a(ph)*), which is needed implicitly in current models or algorithms based on B. We point out that this potential mismatch can be avoided if we arrange the models or algorithms so that they are based on the pigment absorption coefficient (a(ph)). Thus, except for the accuracy of the photosynthetic parameters and the above-surface light intensity, the accuracy of the remote estimation of P depends on how accurately a(ph) can be estimated, but not how accurately B can be estimated. Also, methods to derive a(ph) empirically and analytically from remotely sensed data are introduced. Curiously, combined application of subtropical algorithms for both B and K(d) to subarctic waters apparently compensates to some extent for effects that are due to their similar and implicit pigment-specific absorption coefficients for the calculation of Q(z).     

Hardware-in-the-loop simulation for a production system

This paper proposes a hardware-in-the-loop simulation (HILS) approach for the design and verification of a production system. The design of a production system involves two major activities: mechanical design (device specification and layouts) and electrical design (device behaviour and system control). Conventionally, the mechanical and electrical design activities have been performed sequentially, wasting time. We propose a concurrent procedure of mechanical and electrical design based on the HILS methodology to cope with this problem. The proposed HILS approach provides two major benefits: (1) the verified control program can be directly used for the real plant with minor adaptations; and (2) the verified 3D layout model can be used to generate the detailed drawings for the implementation of the plant. We can minimise the stabilisation time of a production system, since most mechanical and electrical errors can be found and fixed using HILS.     

基于DASYLAB的发电机组电流虚拟监测系统的建立

随着虚拟仪器的不断发展其应用也越来越广泛,作者根据发电机组电流监测的实际需要,利用虚拟测试软件(dasylab)开发出一套虚拟测试系统,较高效地实现了对机组不平衡度及电流谐波的监测,为被测系统的正常工作起到了一定作用,同时对用dasylab进行软件开发做了初步探讨。     

A general statistical model for computer experiments with time series output

Manufacturing processes increasingly rely on computer experimentation as a substitute for costly physical experimentation. However, computer experimentation may not be very efficient because it often relies on computationally intensive simulation (or computer) models. To address this computational problem, this paper proposes a general statistical model as a computationally fast approximation for computer models with time series output. More precisely, the statistical models will be regression models with input-dependent design matrix and input-correlated errors. An example from the automotive industry will be used to illustrate the methodology.     

Optimal production planning for a multiproduct,multistage production system

A mathematical model of production planning for a multiproduct, multistage produetionaystom (production equation, transition equation and objective function) was constructed in order to derive the optimal decision rule to be adapted to demand fluctuation. With this model the optimal solution and the computational algorithm were determined by functional space approach. With use of this algorithm, a numerical example of optimal production planning was solved.     

退化串联可修系统瞬态可靠性分析

可修串联系统是一类经典的可靠性模型,在实际工程中较为常见．为满足工程实际需求,所研究的系统由2个部件和1个维修工组成．假设工作时间、维修时间和部件更换时间均服从指数分布,在维修之后系统不能修复如新．系统采用部件故障N次之后将被更新的维修策略．在这些假设下利用几何过程和马尔科夫过程对系统进行建模,再利用半马尔科夫过程和数值积分方法给出系统瞬态可用度和（0,t］时间内故障次数的计算公式．最后给出算例并应用Monte Carlo方法对所得公式进行验证．为进一步研究复杂机械系统的可靠性提供了理论基础．