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The sequencing and line balancing of manual mixed-model assembly lines are challenging tasks due to the complexity and uncertainty of operator activities. The control of cycle time and the sequencing of production can mitigate the losses due to non-optimal line balancing in the case of open-station production where the operators can work ahead of schedule and try to reduce their backlog. The objective of this paper is to provide a cycle time control algorithm that can improve the efficiency of assembly lines in such situations based on a specially mixed sequencing strategy. To handle the uncertainty of activity times, a fuzzy model-based solution has been developed. As the production process is modular, the fuzzy sets represent the uncertainty of the elementary activity times related to the processing of the modules. The optimistic and pessimistic estimates of the completion of activity times extracted from the fuzzy model are incorporated into a model predictive control algorithm to ensure the constrained optimization of the cycle time. The applicability of the proposed method is demonstrated based on a wire-harness manufacturing process with a paced conveyor, but the proposed algorithm can handle continuous conveyors as well. The results confirm that the application of the proposed algorithm is widely applicable in cases where a production line of a supply chain is not well balanced and the activity times are uncertain.

Digital twin plays a key role in the current development of smart manufacturing systems. Through simulation in the cyber world, real phenomena in the physical world can be predicted and optimized before the final implementation. The usage of the digital twin is enhanced along with the uprising of Industry 4.0, in which data availability supports the further insight of system status, helping the operation managers understand their system and perform resources adjustment more easily. Based on this digitization mature, Lean 4.0, a new concept elaborated from Lean manufacturing, has been interested recently. There are several technologies constituted digital twin that provide a favourable condition for Lean 4.0, such as augmented reality, cloud computing. In this paper, the integration of the Real-time Locating System (RTLS) into digital twin is proposed, which facilitates the performance of Lean 4.0 in manufacturing operation. Not only gain effective control over the facility’s assets, but this integration also enhances the resources utilization, cut down operational wastes, thus brings a better turnover for industrial systems. A case study of successful implementation is shown, which proved the possible advantages of this approach.

Dynamic cycle time setting and line balancing are the most significant problems in modular manufacturing. Industry 4.0 and IIoT (Industrial Internet of Things) based production management systems connect decentralized production units and information sources to increase productivity and flexibility. We developed an IIoT based solution to ensure a real-time connection between products and assembly lines. The proposed dynamic cycle time setting algorithm takes into account the varying complexity of the product based on the real-time information provided by smart wireless sensors and an Indoor Positioning System (IPS). In this paper, we overview Industry 4.0 based assembly line management solutions, present the developed IIoT based infrastructure, and demonstrate the applicability of the proposed cycle time setting algorithm in a simulation example motivated by an industrial open station conveyor.

The fast development of smart sensors and wearable devices has provided the opportunity to develop intelligent operator workspaces. The resultant Human-Cyber-Physical Systems (H-CPS) integrate the operators into flexible and multi-purpose manufacturing processes. The primary enabling factor of the resultant Operator 4.0 paradigm is the integration of advanced sensor and actuator technologies and communications solutions. This work provides an extensive overview of these technologies and highlights that the design of future workplaces should be based on the concept of intelligent space.

Industry 4.0-based human-in-the-loop cyber-physical production systems are transforming the industrial workforce to accommodate the ever-increasing variability of production. Real-time operator support and performance monitoring require accurate information on the activities of operators. The problem with tracing hundreds of activity times is critical due to the enormous variability and complexity of products. To handle this problem a software-sensor-based activity-time and performance measurement system is proposed. To ensure a real-time connection between operator performance and varying product complexity, fixture sensors and an indoor positioning system (IPS) were designed and this multi sensor data merged with product-relevant information. The proposed model-based performance monitoring system tracks the recursively estimated parameters of the activity-time estimation model. As the estimation problem can be ill-conditioned and poor raw sensor data can result in unrealistic parameter estimates, constraints were introduced into the parameter-estimation algorithm to increase the robustness of the software sensor. The applicability of the proposed methodology is demonstrated on a well-documented benchmark problem of a wire harness manufacturing process. The fully reproducible and realistic simulation study confirms that the indoor positioning system-based integration of primary sensor signals and product-relevant information can be efficiently utilized in terms of the constrained recursive estimation of the operator activity.