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114 An industrial application of multivariable linear quadratic control to a cement mill
Abstracts
105 Turnpike Sets on Manufacturing Systems: Some Recent Progress G. Yln, Q. Zhang, pp 501-$04 This work is cotmemed with turnpike sets of stochastic manufacturing systems, which is an important concept in analyzing and developing optimal production policies for a wide variety of manufacturing systems. Several problems, including turnpike sets and their analysis in production planning with discounted costs over an infinite horizon, finite-horizon turnpike sets and associated optimal control problems, and numerical methods for approximating optimal controls under threshold control policies, are examined. The crucial idea lies on using the tum#ke sets as a bridge to design optimal or suboptimal strategies via stochastic control and/or opttmization methods.
106 Optimal Feedback Production Planning In a Stochastic NMachine ~owshop g. Presman, S. Sethl, Qlng ghang, pp S05.508 This paper considers a production planning problem in an Nmachine flowshop subject to breakdown and repair of machines and to non-negativity constraints on work-in-process. The machine capacities and demand processes art assumed to be f'mitestate Markov chains. The problem is to choose the rate of production over time so as to minimize the expected discounted cost of production and inventory/bacldog over an inf'mite horizon. The problem is formulated as a stochastic dynamic programming problem. It is shown that the value function of the problem is locally Lipschitz, and is a solution to the dynamic programming equation, together with certain boundary conditions. Optimal feedback control policies are obtained.
107 Concurrent Resource Scheduling for Flexible Automation P.B. Mirchandani, pp 509-510 Recent advances in automation and computer integrated manufacturing have resulted in the introduction of "flexible" machines. Such machines can perform several operations with little or no set-up, whereas dedicated machines in conventional manufacturing can perform one type of operation per machine. This paper presents a method that concurrently schedules the operations of jobs and resources required to perform them.
108 Real-Time Lot-Sizing Subject to Random Setup Times M.H. Burmann, S.B. Gershwin, pp 511-516
1073
111 Optimal Control of a Tandem Queue with Blocking Xiuli Chao, Hong Chen, pp 527-530 This paper considers a two-station tandem queue with no intermediate buffer. Jobs at the tint station may be blocked when the following station is occupied by another job. The objective is to control the arrival and departure processes, subject to some capacity limits, so that an expected discounted profit function is maximized. The paper proves that the optimal control policy is of a threshold type, and provides the characterization of the threshold.
112 An Automatic Laser Scanning System for Mine Tunnel Surface Characterlsatlon A.J. Jeffery, S. Durucan, J. Dennis, pp 531.534 The study of the surface characteristics of undergmond tmmds has led to the development of an automated turmel surfacemeasurement system, using two coupled intelligent motor drives to manipulate a range-finding laser. Working unattended for up to 4 hours, the system collects a suite of distance measurements, from a mono-rail positioned parallel to the tonnel axis, to points around its circumference. After each measured point is translated from polar to rectangular coordinates, the resulting data represents the tunnel surface in the form of a digital terrain model, which can be viewed and manipulated as a topography.
113 Tomographic Systems for Measurement and Control of Minerals Processing Plants J.A. Gutierrez, T. Dyakowski, F.J. Dickln, R. Thorn, R.C. Waterfall, R.A. Williams, C.G. Xle, M.S. Beck, pp 535-538 Improvements in the control of mineral-processing plants may be made possible by using tomographic techniques to measure the quantity and spatial distribution of material at certain points in the rocess. Electrical tomography can provide real-time (100 mes/sec) distribution maps with a resolution of 1 in 20 lines (400 pixels over cross-section) which can be used for model verification and for measuring material concentrations at critical locations within process vessels as part of an ovesaU control scheme. Case studies are presented on electrical capacitance tomography for non-conducting process fluids (e.g. for use in pneumatic conveyors), and electrical resistance tomography for electrically conducting fluids (e.g. for use in hydrocyclones). 114 An Industrial Application of Multivariable Linear Quadratic Control to a Cement Mill V. Van Breusegem, L. Chen, V. Werbrouck, G. Bastln, V. Wertz, pp 539.542
A real-time, closed-loop setup control algorithm for a manufacturing facility with due dates and significant setup times is proposed. The problem is formulated as a dynamic program and numerically analyzed for a simple example. Extensions for prototyping are briefly discussed.
The paper presents the design procedure of a model-based control algorithm for the regulation of railings and product levels in a cement mill. The control variables are the feeding rate and the classifier speed. Experimental results of a real-life industrial application are reported and discussed with a view to the control of the fineness.
109 Performance Evaluation for Large Ergodic Markov
115 Development of a Density Softsensor for a Mineral
Chains
Grinding Plant
J.B. Lasserre, pp 517-520
G.D. Gonzalez, M.A. Aguilera, L. Castelli, pp 543-546
A new method for computing the steady-state probability distribution of ergedic Markov chains is presented. Starting with some ergodic chain, the steady-stato distribution of a new Markov chain is computed by updating the steady-state distribution of the old one by a simple updating formula. Experiments on a sample of large-band matrices are reported.
110 Dynamic Scheduling Control for a Network of Queues D. Atkins, Hong Chert, pp 521-526 Motivated by dynamic scheduling control for queueing networks, t h e n and Yao (1989) developed a systematic method to generate dynamic scheduling control policies for a fluid network, a simple and higldyaggregatecl model that approximates the queuemg network. The focus of this study is on the implementation of fluid policies as heuristic scheduling policies for queueing networks, and on the performance evaluation of the heuristic policies. Simulation p~veals that these heuristic policies perform a least comparably to, and sometimes much better than, other simple heuristic policies.
This paper addresses the design of a virtual sensor (softsensor) for the pulp density in a grinding plant, in particular the choice of model parameters after the sensor becomes unavailable. A method is proposed and tested on actual plant data. An assumption of stationarity and ergodicity is required, at least during a long enough time period to determine statistics of the estimated rameter with an acceptable variance using time avesagin,g, fore the sensor becomes unavailable. A method for assessing the validity of the softsensor at the time when it is to replace the actual sensor is based on the above assumption.
~
116 Robust Controller Design for a Run-of-Mine Milling Circuit I.K. Craig, pp 547.553 A new approach to the problem of designing a control system for an industrial run-of-mine milling circuit is described. This problem of formalized in terms of a general linear system synthesis and analysis framework to which the ~-methodology is applied. Correlations of plant parameter uncertainties and the choice of the location of uncertainty weights within the plant
105 Turnpike Sets on Manufacturing Systems: Some Recent Progress G. Yln, Q. Zhang, pp 501-$04 This work is cotmemed with turnpike sets of stochastic manufacturing systems, which is an important concept in analyzing and developing optimal production policies for a wide variety of manufacturing systems. Several problems, including turnpike sets and their analysis in production planning with discounted costs over an infinite horizon, finite-horizon turnpike sets and associated optimal control problems, and numerical methods for approximating optimal controls under threshold control policies, are examined. The crucial idea lies on using the tum#ke sets as a bridge to design optimal or suboptimal strategies via stochastic control and/or opttmization methods.
106 Optimal Feedback Production Planning In a Stochastic NMachine ~owshop g. Presman, S. Sethl, Qlng ghang, pp S05.508 This paper considers a production planning problem in an Nmachine flowshop subject to breakdown and repair of machines and to non-negativity constraints on work-in-process. The machine capacities and demand processes art assumed to be f'mitestate Markov chains. The problem is to choose the rate of production over time so as to minimize the expected discounted cost of production and inventory/bacldog over an inf'mite horizon. The problem is formulated as a stochastic dynamic programming problem. It is shown that the value function of the problem is locally Lipschitz, and is a solution to the dynamic programming equation, together with certain boundary conditions. Optimal feedback control policies are obtained.
107 Concurrent Resource Scheduling for Flexible Automation P.B. Mirchandani, pp 509-510 Recent advances in automation and computer integrated manufacturing have resulted in the introduction of "flexible" machines. Such machines can perform several operations with little or no set-up, whereas dedicated machines in conventional manufacturing can perform one type of operation per machine. This paper presents a method that concurrently schedules the operations of jobs and resources required to perform them.
108 Real-Time Lot-Sizing Subject to Random Setup Times M.H. Burmann, S.B. Gershwin, pp 511-516
1073
111 Optimal Control of a Tandem Queue with Blocking Xiuli Chao, Hong Chen, pp 527-530 This paper considers a two-station tandem queue with no intermediate buffer. Jobs at the tint station may be blocked when the following station is occupied by another job. The objective is to control the arrival and departure processes, subject to some capacity limits, so that an expected discounted profit function is maximized. The paper proves that the optimal control policy is of a threshold type, and provides the characterization of the threshold.
112 An Automatic Laser Scanning System for Mine Tunnel Surface Characterlsatlon A.J. Jeffery, S. Durucan, J. Dennis, pp 531.534 The study of the surface characteristics of undergmond tmmds has led to the development of an automated turmel surfacemeasurement system, using two coupled intelligent motor drives to manipulate a range-finding laser. Working unattended for up to 4 hours, the system collects a suite of distance measurements, from a mono-rail positioned parallel to the tonnel axis, to points around its circumference. After each measured point is translated from polar to rectangular coordinates, the resulting data represents the tunnel surface in the form of a digital terrain model, which can be viewed and manipulated as a topography.
113 Tomographic Systems for Measurement and Control of Minerals Processing Plants J.A. Gutierrez, T. Dyakowski, F.J. Dickln, R. Thorn, R.C. Waterfall, R.A. Williams, C.G. Xle, M.S. Beck, pp 535-538 Improvements in the control of mineral-processing plants may be made possible by using tomographic techniques to measure the quantity and spatial distribution of material at certain points in the rocess. Electrical tomography can provide real-time (100 mes/sec) distribution maps with a resolution of 1 in 20 lines (400 pixels over cross-section) which can be used for model verification and for measuring material concentrations at critical locations within process vessels as part of an ovesaU control scheme. Case studies are presented on electrical capacitance tomography for non-conducting process fluids (e.g. for use in pneumatic conveyors), and electrical resistance tomography for electrically conducting fluids (e.g. for use in hydrocyclones). 114 An Industrial Application of Multivariable Linear Quadratic Control to a Cement Mill V. Van Breusegem, L. Chen, V. Werbrouck, G. Bastln, V. Wertz, pp 539.542
A real-time, closed-loop setup control algorithm for a manufacturing facility with due dates and significant setup times is proposed. The problem is formulated as a dynamic program and numerically analyzed for a simple example. Extensions for prototyping are briefly discussed.
The paper presents the design procedure of a model-based control algorithm for the regulation of railings and product levels in a cement mill. The control variables are the feeding rate and the classifier speed. Experimental results of a real-life industrial application are reported and discussed with a view to the control of the fineness.
109 Performance Evaluation for Large Ergodic Markov
115 Development of a Density Softsensor for a Mineral
Chains
Grinding Plant
J.B. Lasserre, pp 517-520
G.D. Gonzalez, M.A. Aguilera, L. Castelli, pp 543-546
A new method for computing the steady-state probability distribution of ergedic Markov chains is presented. Starting with some ergodic chain, the steady-stato distribution of a new Markov chain is computed by updating the steady-state distribution of the old one by a simple updating formula. Experiments on a sample of large-band matrices are reported.
110 Dynamic Scheduling Control for a Network of Queues D. Atkins, Hong Chert, pp 521-526 Motivated by dynamic scheduling control for queueing networks, t h e n and Yao (1989) developed a systematic method to generate dynamic scheduling control policies for a fluid network, a simple and higldyaggregatecl model that approximates the queuemg network. The focus of this study is on the implementation of fluid policies as heuristic scheduling policies for queueing networks, and on the performance evaluation of the heuristic policies. Simulation p~veals that these heuristic policies perform a least comparably to, and sometimes much better than, other simple heuristic policies.
This paper addresses the design of a virtual sensor (softsensor) for the pulp density in a grinding plant, in particular the choice of model parameters after the sensor becomes unavailable. A method is proposed and tested on actual plant data. An assumption of stationarity and ergodicity is required, at least during a long enough time period to determine statistics of the estimated rameter with an acceptable variance using time avesagin,g, fore the sensor becomes unavailable. A method for assessing the validity of the softsensor at the time when it is to replace the actual sensor is based on the above assumption.
~
116 Robust Controller Design for a Run-of-Mine Milling Circuit I.K. Craig, pp 547.553 A new approach to the problem of designing a control system for an industrial run-of-mine milling circuit is described. This problem of formalized in terms of a general linear system synthesis and analysis framework to which the ~-methodology is applied. Correlations of plant parameter uncertainties and the choice of the location of uncertainty weights within the plant