## 1 Introduction
The machine's availability prediction, interference prediction, performance evaluation, etc., are utilized to achieve the dynamic scheduling of the workshop in combination with the digital twin [19]. [PERSON] et al. proposed a kind of digital twin framework for the analysis of products to be designed based on current product running data, which utilizes the data of products generated in the operational process and extracts the key information via text processing and association mining. The analysis results provide a suggestion for the design of the next generation of products [20]. [PERSON] et al. comprehensively characterized the operating state of the production line in the folio method based on the combination of online process simulation and multiphysics simulation of digital twin, which can flexibly operate the open-type production line to meet different personalized demands [21]. [PERSON] et al. combined the mathematical algorithm of remaining service life with the relevant repair strategy and digital twin model to confirm the optimal scheme of repair service [22]. It is becoming increasingly popular to research digital twin technology, and technology is gradually becoming mature. In the meantime, the digital twin technology is applied in the product's whole life cycle, including research, manufacturing, O&M, etc. [23]. Mainly featuring the interactive feedback of virtuality and reality and the iterative optimization, it can connect the stage of design, manufacturing and O&M to provide real-time, efficient and intelligent service for the whole life cycle of a product. With the application of digital twin technology in the manufacturing industry as a premise and the integrated design-manufacturing-O&M control of complex products as a goal, this paper puts forward an integrated method of design-manufacturing-O&M of complex products based on digital twin technology. The corresponding virtual layer is established according to the demand analysis of complex product design, the physical manufacturing unit and the real data of the physical O&M center. The design-manufacturing-O&M integration digital twin is constructed by using high-fidelity virtual model development, collaborative design platform development, intelligent data perception, big data processing,data integration and other technologies. In addition, digital twin-driven integrated operation mechanism for complex product design-manufacturing-operations and maintenance is designed. Through the establishment of a digital twin model of complex products and data integration and interaction mechanisms in the virtual-real fusion, an intelligent manufacturing mode that supports the interaction and collaboration in the design, manufacture and O&M of complex products is formed. Finally, the design-manufacturing-O&M integration framework designed in this paper is applied to an enterprise. The number of product part faults is predicted by an LSTM neural network based on the fault data of the twin platform. The fault prediction results are combined with the integration process of design, manufacturing, and O&M stages to realize iterative optimization design, production plan scheduling, manufacturing process control, and optimal allocation of O&M resources. This enables the design, manufacturing and O&M processes to be deeply interconnected.