[ Research Article ]
The International Journal of The Korea Institute of Ecological Architecture and Environment - Vol. 22, No. 1, pp.13-20
ISSN: 2288-968X (Print) 2288-9698 (Online)
Print publication date 28 Feb 2022
Received 15 Jan 2022 Revised 27 Jan 2022 Accepted 03 Feb 2022

# Research Trends of Cyber–Physical System Technology Applications in the Fields of Buildings and Equipment

Bo Rang Park* ; Tae Won Kim** ; Nam Hyeon Kim*** ; Jin Woo Moon****
*Associate Research Engineer, School of Architecture and Building Science, Chung-Ang Univ, South Korea pbr_1123@naver.com
**Coauthor, Graduate Student, School of Architecture and Building Science, Chung-Ang Univ, South Korea xnglish@naver.com
***Coauthor, Graduate Student, School of Architecture and Building Science, Chung-Ang Univ, South Korea skagus1546@naver.com
****Corresponding author, Professor, Dept. of Architecture and Building Science, Chung-Ang Univ, South Korea gilerbert73@gmail.com

## Abstract

Purpose:

The purpose of this study is to identify research trends based on a comparative analysis of cyber–physical systems (CPS) application research papers in the fields of domestic and international building and equipment. Papers and recent actual cases were identified to determine the current level and future development potential.

Method:

For this purpose, research papers published in domestic and international journals in the past five years were classified by year, field, topic, and keyword for an in-depth analysis. In addition, domestic and international representative cases were selected, and the applied technologies and performances were analyzed.

Results:

As a result of the research trend analysis, it was confirmed that the research in the fields of CPS and applied building equipment is increasing continuously. Most of the papers were published in the field of the building environment and equipment. In Korea, other fields dealing with policy and spatial psychology were associated with the highest number of papers, followed by the building environment equipment and planning divisions. Overseas, it was found that the number of papers in the fields of the building environment and equipment was significantly higher. Through this study, the level of CPS applications and the potential for development in the field of building and equipment were identified, and the direction and basic technology of the CPS and applied building energy optimization model planned to be developed in future research were confirmed.

## Keywords:

Building System, Cyber–Physical System, Digital Twin

## 1. Introduction

### 1.1. Research Background and Purpose

In the era of the Fourth Industrial Revolution, advancements in information and communications technology (ICT) have led to the provision of smart environments to building users and residents as smart buildings and smart cities industries have become the focal points of the building and equipment fields. A smart environment refers to a new type of environment in which various ICT techniques, such as artificial intelligence (AI), Internet-of-Things (IoT), cloud, big data, mobile, and security are integrated in buildings, thus providing comfort, convenience, safety, and economic benefits in residential environments[1].

An industrial revolution is based on a cyber–physical system (CPS) platform which integrates various ICT types. CPS is a complex system in which a physical environment comprising sensors and actuators is combined with computing elements that control the physical environment in real time by simulating a virtual system[2]. Another term which is frequently mentioned in conjunction with CPS is the digital twin. The reason for which CPS and digital twin are gaining popularity is that they both deliver and utilize the information in the virtual and real worlds[3]. CPS focuses on monitoring and equipment control achieved by using the information of a physical environment, while a digital twin constructs a virtual world resembling the real world based on the information of a physical environment. The relationship between CPS and digital twin is interpreted in different ways depending on applications and research fields, but most perspectives are based on the same concept.

### 4.2. Domestic Cases

The PLUG Builder is an integrated operation platform based on CPS, digital twin, and a three-dimensional (3D) modeling tool of PLUXITY which is a specialized company in Korea. Real-time monitoring and various simulation features are provided by integrating GIS and BIM data based on a 3D virtual environment of buildings and cities. Different situations can be predicted and prepared for through-simulation features that vary depending on building or service types, thus enabling efficient building design and urban planning[22].

Notable solutions include PLUG Building, PLUG City, and PLUG Energy, as shown in <Fig. 9.>. PLUG Building provides integrated building security and smart building services wherein more intuitive management and immediate response are possible. It has been applied in Daemyung Resort, Seoul Grand Park, and Suwon City Hall. PLUG City is a CPS-based, contactless, integrated city operation solution which provides various features including monitoring of 3D maps of MOLIT, integrated monitoring of linked public data, urban energy monitoring, and closed-circuit television intelligent monitoring. Recently, a variety of simulations required in the building design stage, such as the sunlight, visibility, prospect, and wind path have been studied. Several existing cases include the digital twin of Busan Eco Delta Smart City, Busan B-Con development, the autonomous driving project in Daejeon, and a 3D indoor map of Seoul. PLUG Energy solution enables efficient energy management based on real-time power generation measurements for new renewable energy. The process of absorbing, storing, and conversion of solar energy is visualized and simulated to provide statistics and analyses for power generation status and energy usage of each facility. Research is conducted continuously on the development and demonstration of the energy-saving smart lighting platform technology, integrated KT-MEG solar light monitoring system, and construction of a zero light pollution model complex in Seoul.

Representative CPS digital twin technologies of PLUXITY

Furthermore, other solutions, such as PLUG Data, which performs real-time monitoring of temperature/humidity of data centers, panel boards, and the heating statuses of servers, and PLUG Warehouse, which is capable of serving as the distribution center for provision and visualization of information on the indoor environment, automatic calculation of warehouse area, and work status visualization, are provided[23].

In addition to the two cases analyzed above, various platforms utilizing CPS and digital twin technology are launched and applied across a diverse range of fields. The competition in the CPS and digital twin market is intensified owing to fusion of the ICT technology fusion and integration of IoT and simulation technologies. However, despite the outstanding of competencies of various companies and research institutes in basic software and hardware required for the development and operation of CPS and digital twin technologies in an advanced ICT country, the core technology in Korea is still dependent on foreign technologies of overseas companies, while integrated solutions for optimization and prediction through CPS are still insufficient.

Immediate inspection and response to the problems occurring in a CPS and digital twin platform are possible, while energy, air conditioning, safety, and firefighting solutions that have been managed separately in existing systems are now subject to integrated management. Therefore, labor and time required for management and operation can be efficiently saved when compared with existing systems.

To ensure compliance with timelines pertaining to the use and domestic applicability of CPS, of which the necessity and influence are gradually growing, the reinforcement of integrated solutions pertaining to original technology competencies must take precedence for lowering the dependence of domestic companies and research institutes on the CPS technologies of overseas companies. In addition, to expand the applicability of CPS in the building the equipment fields, the issues and limitations of conventional technologies, such as building energy management system (BEMS) and building information modeling (BIM), which are based on a similar concept as that of CPS, must be improved to allow further developments and applications of the services integrated with CPS and digital twin.

## 5. Conclusions

This study examined the cases of domestic and international papers published over the past five years (from 2017 to 2021) which were related to CPS applications in the building and equipment fields. The following conclusions have been drawn based on comparative analyses of the papers identified based on year, field, topic, and keyword.

A total of 107 papers were examined in this study. Among these, 46 papers were published in domestic journals, while 61 papers were published in international journals. The number of papers has steadily increased from nine (in 2017) to 39 papers (in 2021). It can thus be concluded that the research on CPS application in the building and equipment fields has been expanding.

The building and equipment fields were further categorized into building environment and system, planning, construction, structure, material, and others. The top three fields with the most number of published papers include the building environment and system with 84 papers (60 %), others with 21 papers (20 %), and planning with 17 papers (16 %). In the building environment and system field with the highest number of published papers, most research focused on building energy. Among the papers published domestically, the highest numbers were in policy and space psychology in the others field, followed by the building environment and system field, and the planning field. The papers published internationally had a significantly higher number of papers in the building environment and system fields. Research in Korea is being conducted across several different topics, whereas overseas studies tended to concentrate on the building environment and system fields.

The studies were analyzed by using a word cloud of keywords. The results showed that the application of CPS and digital twin was mostly focused on IoT, Intelligent, Predictive, Deep learning, and Simulator technologies for achieving optimal control of building energy.

This study analyzed the current status of CPS applications in the building and equipment fields based on research trends and case studies. Accordingly, the current level of CPS applications and development potential in the building and equipment field were proposed, while a) the basic technology was identified, and b) the direction of a building energy optimization model was established based on the anticipated, future CPS applications. Therefore, research with improved efficiency and performance compared with conventional technology is expected to be conducted by applying the advantages of CPS, such as immediate identification of situations, real-time response, and integrated management to a building energy optimization model.

## Acknowledgments

This basic research project has been supported by the National Research Foundation of Korea and funded by the Ministry of Education in 2021 (No. 2021R1I1A1A01045817).

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CPS concept

### Fig. 2.

Definition of digital twin based on a step-by-step process

### Fig. 3.

Chronological trend of CPS publications from 2017 to 2021

### Fig. 4.

Research trends associated with the building and equipment fields

### Fig. 5.

Keyword word cloud

### Fig. 6.

Domestic journal papers in the fields of building and equipment

### Fig. 7.

International journal papers in the fields of building and equipment

### Fig. 8.

GE predix cloud concept diagram and applications (AI: artificial intelligence)

### Fig. 9.

Representative CPS digital twin technologies of PLUXITY

### Table 1.

CPS and digital twins of building and equipment field

Field Main Technology Main Achievements
Abbreviations: CPS: cyber–physical systems, ICT: information and communications technology, IoT: Internet-of-Things, ANN: artificial neural network, MPC: model predictive control, HVAC: heating, ventilation, and air conditioning
Building Smart building [12] ∙ Electrical energy prediction and control
∙ Energy and environmental monitoring
∙ CPS platform service
Smart factory [13] ∙ Saving energy and cost
∙ CPS platform service
∙ Data monitoring
Smart construction management [14] ∙ ICT platform for manager support module
∙ IoT connection
∙ Data monitoring
Equipment Energy Performance [15][16] ∙ Data center cooling system control
∙ Cooling energy saving
∙ Sensing and ANN
∙ CPS control platform
Efficiency [17] ∙ MPC method CPS platform
∙ HVAC system efficiency improvement
City Smart Grid [18] ∙ Management cost of energy transfer
∙ Control, computation, communication, security
Smart City [19] ∙ CPS-based smart city service policy

### Table 2.

Number of papers published in the literature classified by field

Field 2017 2018 2019 2020 2021 Total Ratio (%)
Environment & System 7 7 11 19 20 64 60
Planning 2 2 3 4 6 17 16
Construction 0 0 0 3 1 4 4
Structure 0 0 0 0 1 1 1
Material 0 0 0 0 0 0 0
etc. 0 2 5 3 11 21 20
Total 9 11 19 29 39 107 100

### Table 3.

Research trends by topic

Field Topic No. Ratio (%)
Environment & System Building energy 35 33
System 17 16
Indoor environment 11 10
Renewable energy 1 1
Subtotal 64 60
Planning Urban planning 11 10
Architecture design 6 6
Subtotal 17 16
Construction Process control 4 4
Cost estimation 0 0
Subtotal 4 4
Structure Structural optimized design 1 1
Subtotal 1 1
etc. Review paper 11 10
Policy 5 5
Psychology 5 5
Subtotal 21 20
Total 107 10

### Table 4.

Domestic journal papers in the fields of building and equipment

Field 2017 2018 2019 2020 2021 Total Ratio (%)
Environment & System 1 1 2 7 2 13 28
Planning 2 2 3 3 3 13 28
Construction 0 0 0 3 1 4 9
Structure 0 0 0 0 1 1 2
Material 0 0 0 0 0 0 0
etc. 0 1 4 2 8 15 33
Total 3 4 9 15 15 46 100

### Table 5.

International journal papers in the fields of building and equipment

Field 2017 2018 2019 2020 2021 Total Ratio (%)
Environment & System 6 6 9 12 18 51 84
Planning 0 0 0 1 3 4 7
Construction 0 0 0 0 0 0 0
Structure 0 0 0 0 0 0 0
Material 0 0 0 0 0 0 0
etc. 0 1 1 1 3 6 10
Total 6 7 10 14 24 61 100