## 5 Conclusions  
The main goal of this paper was to check the operability of the oil pump maintenance system functionality when the augmented reality system and the dynamic modeling system were used together. The conducted research has shown the possibility and expediency of using this approach. At the same time, it is necessary to mark a number of moments which are worth paying attention to using this approach:  
1. The structure of the system should have a modular principle of construction and be able to scale and expand its functionality. For this purpose, it is required to allocate the central communication level. This level should include software and hardware that allows one to transfer data using the most advanced protocols such as OPC UA, MQTT, and others. In this case, the use of OPC UA is mandatory, as is the main protocol of interaction with physical models and the real object;  
2. The modular principle of the structure of the developed system should support the possibility of allocation of various subsystems involved in common processes (e.g., the control system, power supply system, and other similar systems). This structure will provide an option to replace the real parts of the system with virtual ones and vice versa for the implementation of additional functionality. The virtual models are exact 3D models of each part and a dynamic model that replicates the dynamic properties, including the inertia of each object;  
3. When evaluating the performance of a particular augmented reality solution, it is preferable to use at least two types of testing: testing the application performance and testing the cognitive-psychological impact of the system on a person;  
4. Performance testing of the system has shown that it is possible to use dynamic simulation systems in augmented reality together with real process data. Experiments to evaluate the CPU and memory consumption for the application's performance showed its performance both with minimal and increased load in the form of different numbers of connected dynamic models (the maximum load tested was five dynamic models running simultaneously). Since this test showed no significant performance degradation, the authors considered the connection of five models to be sufficient;  
5. Testing of the cognitive-psychological impact of the system on humans has shown that the emergency shutdown task when using the augmented reality system in collaboration with the dynamic model yielded improvement in the following ways: mental demand, physical demand, temporal demand, performance, and frustration.  
The authors emphasize that this work is a continuation of the study described in [28]. The continuation of the works presented in the article is the works on extension of the connected dynamic models and connection of the dynamic models and diagnostic systems to determine the life cycle and residual life of oil pumps. It also includes methods of the collaborative use of real and virtual parts of the system and the development of an extended method of testing augmented reality applications. Works showing the connection of other digital technologies, such as the digital twin of electrical equipment, and its use in industrial applications and a number of other works are also a continuation of the present work.  
Conceptualization, N.K.; methodology, N.K.; software, N.K. and V.V.; formal analysis, N.K. and V.V.; resources, N.K. and V.V.; writing--original draft preparation, N.K.; writing--review and editing, I.F.; visualization, N.K. and V.V.; supervision, I.F.; experiments--N.K. and V.V.; project administration, N.K. All authors have read and agreed to the published version of the manuscript.  
This research was performed at the expense of the subsidy for the state assignment in the field of scientific activity for 2021 No. FSRW-2020-0014.  
Not applicable.  
The authors declare no conflict of interest.