Abstract

The main concept of the authors is to place Reinforcement Learning (RL) into various fields of manufacturing. As one of the first implementations, RL for Statistical Process Control (SPC) in production is introduced in the paper; it is a promising approach owing to its adaptability and the continuous ability to perform. The widely used Q-Table method was applied for get more stable, predictable, and easy to overview results. Therefore, quantization of the values of the time series to stripes inside the control chart was introduced. Detailed elements of the production environment simulation are described and its interaction with the reinforcement learning agent are detailed. Beyond the working concept for adapting RL into SPC in manufacturing, some novel RL extensions are also described, like the epsilon self-control of exploration–exploitation ratio, Reusing Window (RW) and the Measurement Window (MW). In the production related transformation, the main aim of the agent is to optimize the production cost while keeping the ratio of good products on a high level as well. Finally, industrial testing and validation is described that proved the applicability of the proposed concept.

Highlights

  • Artificial Intelligence (AI) and Machine Learning (ML) approaches are spreading across all areas in our live, it is valid for technical fields, e.g., for the manufacturing sector as well

  • A significant advantage of this concept was that every component of the reinforcement learning, and its environment was connected to a real application, and real measurements were feed-back to the simulation model and updated the knowledge base

  • Beyond the rare and particular cases presented as process control in the given industrial assignments, the current paper proposes a generalized, widely applicable Reinforcement Learning for Statistical Process Control (RL for SPC) framework to keep the production between the prescribed Lower Tolerance Limit (LTL) and Upper Tolerance Limit (UTL) of the related Statistical Control Chart (SCC), important novel ex­ tensions are introduced as well

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Summary

Introduction

Artificial Intelligence (AI) and Machine Learning (ML) approaches are spreading across all areas in our live, it is valid for technical fields, e.g., for the manufacturing sector as well. The frequently arising, novel AI and ML techniques have to be continuously adopted to the given domain to achieve the best match This mission is valid to manufacturing, while the well-known Industry 4.0 global initiative (called as Industrial Internet or Cyber Physical Production Systems (CPPS)) supports, facilitates, incorporates these directions, the actual situation in this sector is quite promising. As described in the paragraph, the reviewing the scientific literature mirrors that the domain specific adaptation of reinforcement learning to various production fields concentrates mainly, only to production scheduling and robotics. This state-of-the-art status provoked the moti­ vation to extend and adapt reinforcement learning to further potential fields of manufacturing.

Reinforcement learning in production
Statistical process control in manufacuring
RL for SPC in manufacturing
Temporal difference learning
Events
Environment
Reward of production
State representation
Dynamic Q-Table
Knowledge representaion: Q table
State extension with past actions
Exploration control rule
Initial exploration level
Industrial test and validation
Findings
Conclusions and outlook
Full Text
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