Towards System State Dispatching in High-Variety Manufacturing

This study proposes a shift towards system state dispatching in the production control literature on high-variety manufacturing. System state dispatching lets the decision on what order to produce next be driven by system-wide implications while trading of an array of control objectives. This contrasts the current literature that uses hierarchical order review and release methods that control the system at release, whilst myopic priority rules control order dispatching based on local queue information. We develop such a system state dispatching method, called FOCUS, and test it using simulation. The results show that FOCUS enables a big leap forward in production control performance. Specifically, FOCUS reduces the number of orders delivered late by a factor of one to eight and mean tardiness by a factor of two to ten compared to state-of-the-art production control methods. These results are consistent over a wide variety of conditions related to routing direction, routing length, process time variability and due date tightness

Higher-order mean-field theory of chiral waveguide QED

Waveguide QED with cold atoms provides a potent platform for the study of non-equilibrium, many-body, and open-system quantum dynamics. Even with weak coupling and strong photon loss, the collective enhancement of light-atom interactions leads to strong correlations of photons arising in transmission, as shown in recent experiments. Here we apply an improved mean-field theory based on higher-order cumulant expansions to describe the experimentally relevant, but theoretically elusive, regime of weak coupling and strong driving of large ensembles. We determine the transmitted power, squeezing spectra and the degree of second-order coherence, and systematically check the convergence of the results by comparing expansions that truncate cumulants of few-particle correlations at increasing order. This reveals the important role of many-body and long-range correlations between atoms in steady state. Our approach allows to quantify the trade-off between anti-bunching and output power in previously inaccessible parameter regimes. Calculated squeezing spectra show good agreement with measured data, as we present here.Comment: 16+9 pages, 9+2 figure

Towards System State Dispatching in High‐Variety Manufacturing

This study proposes a shift towards system state dispatching in the production control literature on high-variety manufacturing. System state dispatching lets the decision on what order to produce next be driven by system-wide implications while trading of an array of control objectives. This contrasts the current literature that uses hierarchical order review and release methods that control the system at release, whilst myopic priority rules control order dispatching based on local queue information. We develop such a system state dispatching method, called FOCUS, and test it using simulation. The results show that FOCUS enables a big leap forward in production control performance. Specifically, FOCUS reduces the number of orders delivered late by a factor of one to eight and mean tardiness by a factor of two to ten compared to state-of-the-art production control methods. These results are consistent over a wide variety of conditions related to routing direction, routing length, process time variability and due date tightness

Non-hierarchical work-in-progress control in manufacturing

Reducing Work-In-Process (WIP) in manufacturing systems is associated with advantages such as predictable throughput times and increased manageability. To achieve this, an abundance of WIP control methods have been developed, such as CONWIP1 and Kanban for repetitive manufacturing, and LUMS COR2 and POLCA3 for high-variety manufacturing. These methods take three types of control decisions, viz., release (entry to the manufacturing system), authorization (entry to a work centre) and dispatching (order selection at a work centre). All existing WIP control methods are hierarchical by first deciding on release and authorization before making dispatching decisions, thereby letting the decision whether to produce precede over which order to produce. This hierarchy is traditionally motivated by uncertainty in information between organizational levels, but this is questionable given the advent of Industry 4.0 technologies. We develop a non-hierarchical method – termed DRACO4 – that simultaneously considers release, authorization and dispatching when deciding. The simulation results show that DRACO significantly outperforms LUMS COR and POLCA on mean WIP and delivery performance measures. Additional analysis also indicates that overall manageability is improved by the non-hierarchical method DRACO