- Email: [email protected]
Study on Architecture and Application Technology of Ubi-bus Network of Building Automation System
Available online at www.sciencedirect.com
ScienceDirect
Available online at www.sciencedirect.com Procedia Engineering 00 (2017) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 1286–1293
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
Study on Architecture and Application Technology of Ubi-bus Network of Building Automation System Jili Zhanga,*, Xiuming Lia, Tian Xinga and Xinxin Tanga aa
Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian University of Technology, Dalian, China
Abstract Characteristics and problem of building automation system (BAS) existed in the practical engineering application are analyzed, and then the development of BAS is discussed from the perspective of network structure and supplied function service. Aiming at the space distribution feature, this paper presents the network architecture of Ubi-bus fieldbus, and then essential feature, operation mechanism and standardized information model are introduced respectively. Software and hardware are designed and developed in the control platform of variable air volume (VAV) air conditioning system. Based on the network architecture of Ubi-bus, it is potential for the solution of BAS integration in the practice application. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Ltd. committee of the 10th International Symposium on Heating, Ventilation and Air Peer-review under responsibility of Elsevier the scientific Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Conditioning. Air Conditioning. Keywords: Building automation system; Network architecture; Task-oriented; Development of key technology
1. INTRODUCTION With the rapid development of intelligent building technology, BAS integration technology based on BACnet[1], LonWords[2], XML/Web Service[3] and OPC[4, 5] has been mature and evolved from high integration to multilevel and multi-information [6] gradually. In the process of system integration, BAS still has following problems: 1) BAS is derived from industrial automation system, which network architecture could not meet the feature of equipment dispersed distribution and multiple fieldbus coexistence; 2) only a simple logic control could be achieved using solidified programs based on present control devices, which cannot support online-optimal control; 3) present systems have a lower automation level. The reason is that the BAS products are provided by different equipment * Corresponding author. E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.382
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manufacturers, which improves the difficulty of networking and debugging and decreases system compatibility and integration efficiency. BAS control and management tasks have spatial distribution attribute, which means that building electromechanical equipment relies on the building space and distributes in each subsystem for different areas, and different functional services also depend on the building space [7]. This paper presents a network architecture of Ubi-bus, and then organization structure, working principle, the key technology and development process are demonstrated step by step. 2. DEVELOPMENT OF BUILDING AUTOMATION TECHNOLOGY From the perspective of function services, BAS is a typical distributed system with multi-task scheduling, in which different kinds of field electromechanical devices are scheduled and managed based on a kind of multi-task distribution mechanism [9] uniformly. Considering of structure and functional service demand [10], BAS development process could be divided into four generations according to that of traditional industrial automation system. First generation for electromechanical devices: The system only contains air compressor-powered pneumatic control devices and a small number of electrical control devices and has no complete equipment and fieldbus network, which could only implement local control based on the independent electromechanical equipment. Second generation for the controller: With the development of electrical automation technology, centralization control system with programmable logic controller and direct digital controller has been widely used. Therefore, private field bus has been established by different manufacturers. However, it is difficult to form a standard filed bus network, which results in the difficulties for sharing information and cooperating. Third generation for the information flow: With the development of information technology, distributed control system, which derived from centralization control system, has formed a complete control system network. Then, manufactures have converted control mode from based-collaborative to based-communication, which improves communication rate and information processing capability. Unfortunately, it is difficult to implement cooperation and share among different subsystems due to lack of attention on functional service demand. Fourth generation for the task: The development direction of BAS haves converted to networked, flattening and professionalization. Task-oriented system could be established with multi-task cooperation mechanism, which satisfies functional service requirements for electromechanical equipment in different subsystems. 3. PROPOSE OF UBI-BUS NETWORK OF BUILDING AUTOMATION SYSTEM 3.1. Analysis of building operation tasks In the perspective of building functional services, operation tasks in BAS mainly include: operating status monitoring, electromechanical device control and daily operation management. Each task is independent with others, and all tasks are considered as a whole and depends on information exchange based on building internal communication network. Details are as follow: 1) Operation status monitoring; 2) Electromechanical device control and operation management; 3) Operation management task. Building operation tasks are implemented with the electromechanical device and various subsystems, all of which constitute a set of building operation service system. As shown in figure 1, the operation task, which is implemented by electromechanical device, has spatial distribution attribution. Building operation tasks are distributed in the building space unit. Specified performance is: 1) the electromechanical device, which has the same function and interacts with each other, is distributed in the building; 2) Building operation task is mainly for collaboration control of the electromechanical device in different subsystems; 3) Electromechanical device in the same space, which belongs to different subsystems, usually implements the control action following the same functional requirements.
Jili Zhang et al. / Procedia Engineering 205 (2017) 1286–1293 Jili Zhang et al./ Procedia Engineering 00 (2017) 000–000
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3
变风量空调系统
新风系统 风机盘管系统
消防系统 电梯系统 冷冻站系统
Fig. 1. (a) Spatial distribution attribute for the building operation task; (b) Conformance to requirements for the same space operation task
3.2. Basic characteristics of Ubi-bus network To solve practical engineering problems, the mode of BAS integration need to be changed. During the design process, functional requirements and roles of each subsystem need to be paid attention. In the global perspective, BAS could be considered as a multi-task set, in which general description and relationship are corresponding between functions and the tasks, depending on electromechanical device units. For instance, air conditioning unit could provide supply air volume and supply air temperature adjustment function. Control strategies (constant air pressure control, variable air supply pressure control, and total air volume control, etc.), which could be seen as variable tasks, need be implemented at the same time. There is a generalized relationship between functions and tasks in the building space unit, which makes a diversification of functions for electromechanical devices. That is to say tasks under different working conditions are solved by different methods using the same electromechanical device. Therefore, this paper presents an Ubi-bus network architecture and system integration solution for BAS tasks, which have the spatial distribution characteristics. Characteristic 1: Bus type, delayering and arbitrary extension of the network architecture; Characteristic 2: Specialization, individuation and standardization of the task definition; Characteristic 3: Standardization, modularization and plug-play of the network equipment; Characteristic 4: Standardization, intellectualization and optimization of the information processing. 3.3. Operation mechanism of Ubi-bus network Linker, which is considered as the core component of automatic control system, mainly implements tasks with the electromechanical equipment in the building space units. Substantially, the study of the operation mechanism should consider the topology of Ubi-bus network and electromechanical equipment, which is based on the distribution relationship of linkers. Figure 2 shows the operation mechanism of Ubi-bus network, which is a scheduling process based on the task of the linker standardized information model essentially. Tasks are divided into private tasks and public tasks according to the relationship between linkers and task classifications. Private tasks are only associated with single linker while public tasks are associated with multiple linkers. Public tasks can also divided into serial tasks and parallel tasks according to the data flow classification. For serial tasks, message will be transmitted from the network interface of i-linker to j-linker turn by turn, if the message is generated in i-linker and its purpose is j-th linker. For parallel tasks, the message information of i-linker is only transmitted to its adjacent linkers if the message is generated in i-linker.
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Linker C
Private task
Common task HVAC engeneer
Private task Developer
Common task
Linker A
Function A
Linker D
Function B
Private task
Private task
Private task
Common task
Linker E
Linker B Function C
Linker G
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Private task
Private task Linker F
Function D
Common task Electrical engineer Linker H
Private task
Fig. 2. The operating mechanism of the generalized fieldbus network
Above processes establish a link among electromechanical engineers, HVAC engineers and software engineers based on their cooperation with each other. Operating steps are described as follow: 1) Functional requirements of the controlled object are proposed by HVAC engineers. 2) Electromechanical engineers take standardized designs for electromechanical device units in the building. 3) Software engineers write appropriate software programs, which are based on the specific logical relationships for specified function. 3.4. Linker standardized information model Linker standardized information model is shown in figure 3. Linker is responsibility to connect to field electromechanical devices through their own IO modules directly and create network mappings by bounding ID and channels. Corresponding information is open-ended for electromechanical engineers, software engineers and end users, which makes the networking and configuration standardization at the field equipment layer. Based on the linker standardized information model, IO modules, which are produced by different manufactures, could be arbitrarily replaced after a simple configuration process under the condition that the extended IO module supports a standardized and general communication protocol. In this way, the correlation between the physical address of the electromechanical device and the variable address of the software program is greatly reduced. Furthermore, this could avoid a large number of networking and configuration work.
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Fig. 3. Linker standardized information model
Data transmission between linkers are bidirectional, which means each linker has two relatively independent network interfaces for network physical connection and addressing. If specified function and service demand is generated, corresponding task can be done through cooperating with several linkers. 4. DEVELOPMENT OF KEY TECHNOLOGY OF UBI-BUS NETWORK IN VAV AIR CONDITIONING SYSTEM 4.1. Ubi-bus network architecture of VAV system According to the control demand of VAV air conditioning system [11], system schematic diagram of VAV control platform based on Ubi-bus network is shown in figure 4. There are three layers in the platform, which includes Field M&C layer, field bus layer and area-ctrl layer.
Fig. 4. Schematic diagram of control platform for VAV air conditioning system
1. Field M&C layer includes all kinds of devices in VAV air conditioning system, includes: 1) electromechanical devices such as air conditioning units, air fan and terminal devices for the basic demand of VAV air conditioning system; 2) temperature sensors, pressure sensors, damper actuators, variable frequency devices and other devices which are responsible for system operation and adjustment; 3) linkers, which means control equipment with fieldbus communication interfaces.
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2. Field bus layer is the transmission medium in the terminal site, which is responsible for data transmission through RS-485 industrial fieldbus. Field bus layer, plays the role of connecting the controllers and linkers, is the transmission medium between Field M&C layer and area-ctrl layer. Linkers adopts standard, open-ended and general Modbus-RTU protocol in order to support most of the on-site electromechanical devices as well as other standard communication protocols. 3. Area-ctrl layer, which is mainly composed of programmable logic controllers, is the key part in the control system. In-site devices are monitored and controlled by a serial of logical operation, sequence control, parameter setting and arithmetic, etc. Area-ctrl layer is located between field bus layer and the wide area network, supporting most of standard communication protocols. 4.2. Design & development of linkers and control terminal 1. Linkers Linkers are mainly composed of extended IO modules, and the selection and configuration for terminals are standardized according to specified points of electromechanical devices. As shown in figure 5(a), IO extension modules in the linker adopts small and medium PLC extension modules produced by Dalian Technology Computer Control Engineering Company (DCCE). These modules have following characteristics: 1) Anti-interference ability all through the electromagnetic compatibility level-3 standard, and interfaces are equipped with isolated circuits for the stability; 2) Supporting the standard Modbus protocol for any third party I/O extension devices; 3) Supporting terminal removable, charged plug and other practical functions; 4) Small and saving space. 2. Intelligent control terminal Considering of the spatial distribution characteristics of VAV terminal equipment, this paper adopts SIEMENS S7-1200 PLC as the core-controller in the intelligent control terminal for VAV air conditioning system, which is shown in figure 5(b).
Fig. 4. (a) Linker; (b) Intelligent control terminal
Intelligent control terminal could be used for central air conditioning control system and provides multiple standard RS-485 communication interfaces for supporting ASCII, USS drive protocol, Modbus RTU and other standard communication protocols. Besides, intelligent control terminal has a separate human-machine interface so that the operating status of on-site electromechanical devices could been displayed and operated intuitively. Intelligent control terminal has monitoring and controlling functions, which are helpful and continent for the realtime operation management, such as human-computer interaction, network interaction, mobile APP and other functions. 4.3. Design and development of software As shown in Figure 3, each extended IO module has unique fieldbus address. Through strict correspondence rules between the electromechanical equipment and the IO module channel, standardized configuration work could been implemented between the IO module channel and the software address. This avoids the secondary development for the software program and provides a flexible system integration solution.
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According to the standard information model of the linker, the software development could be divided in two steps: 1) Configure standardization the information model of the linker and the extended IO module channel; 2) Compile the standardization information model of the linker, control algorithm logic and human-machine interface. Linker standardization information model is the basis of the software program development, while the channel address of the extended IO module could not be considered in the compile process of control algorithm and logic. Therefore, control algorithm and logic programs, which is the core of the software program, need not rewritten case by case. Software programs mainly includes initialization, linkers, human-machine interface, communication and control algorithm and logic. 1) Initialization: This part is responsible for setting initial values before the system implementation. For example, the damper need to be opened in the system start process to insure the fan safety. 2) Linkers: This part is equivalent to the central nervous of the entire software program, which is responsible to convert the digital signal into the standardization information model. 3) Human-machine interface: This part is responsible for the daily management and maintenance through the information exchange between machines and users, and specified functions includes basic information, operating status information, parameter setting, fault information, graph and report, etc. 4) Communication among subsystems: This part is responsible for communicating with other subsystems such as refrigerating station system, independent fresh air system, fire alarm system, etc. 5) Control algorithm and logic: This part is the core of the entire system software program which is responsible for realize the optimal operation of VAV system based on a serial of security logic, sequential control logic, on-line optimal control algorithm. 5. Conclusion This paper present the Ubi-bus network architecture for building automation control in aspects of the theory and the application. Firstly, this paper discusses the characteristics and development process of building automation system, and points out that the existing network architecture could not satisfy the new functional requirement. Secondly, this paper presents an Ubi-bus network architecture, then basic characteristics, operating mechanism and standardized information model are introduced, respectively. Taking the network control platform of VAV system for example, the design and development process of hardware and software are introduced based on the Ubi-bus network architecture. Results show that building automation system integration solution based on Ubi-bus network has great potential of practical engineering applications, and could make building automation system more standardized, generalized and intelligent. Acknowledgements The authors gratefully acknowledge the financial supports from the National Natural Science Foundation of China (Grant No. 51578102，51378005) This work is supported by National Key Research and Development Project of China No. 2017YFC0704100 (entitled New generation Intelligent building platform techniques) References [1] Edwards R. Intelligent Buildings and Building Automation. J. Construction Management and Economics. 29(2) (2011) 216-217. [2] Figueiredo J, J Sá Da Costa. A SCADA system for energy management in intelligent buildings. J. Energy and Buildings. 49(2012) 85-98. [3] HVAC application [Chapter 47] In Design and application of controls. American Society of Heating, Refrigerating and Air-conditioning Engineers, (ASHRAE), Atlanta. 201147. 7-8. [4] Jianbo Bai, Xiaosong Zhang. Building automation systems and integration technologies based on Web Services, J. Journal Heating Ventilating and Airconditioning. 35(11) (2005) 27-34. [5] Qi Shen. Studies on Architecture of Decentralized System in Intelligent Building. Tsinghua University. [6] Song W S, Hong S H, Bushby S T. A Performance Analysis of BACnet® Local Area Networks, J. HVAC&R Research. 14(2) (2008) 289305. [7] Yu Zhen, LI Huai. Research Progress of Building Automation Technology. J. Building Science. (10)(2013) 106-113
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[8] Yang R and Wang L. Development of multi-agent system for building energy and comfort management based on occupant behaviors. J. Energy and Buildings. 56(2013) 1-7. [9] Zheshen Zhao. Analysis of topological structure and developing trends of building automation systems, J. Journal Heating Ventilating and Airconditioning. 11(2012) 32-37. [10] Zhengyuan Xu, Shengwei Wang. The integrated system of the intelligent building based on OPC and WEB SERVICES middleware technology. J. Intelligent Building and City Information. (01)(2007) 42-45.
ScienceDirect
Available online at www.sciencedirect.com Procedia Engineering 00 (2017) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 1286–1293
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
Study on Architecture and Application Technology of Ubi-bus Network of Building Automation System Jili Zhanga,*, Xiuming Lia, Tian Xinga and Xinxin Tanga aa
Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian University of Technology, Dalian, China
Abstract Characteristics and problem of building automation system (BAS) existed in the practical engineering application are analyzed, and then the development of BAS is discussed from the perspective of network structure and supplied function service. Aiming at the space distribution feature, this paper presents the network architecture of Ubi-bus fieldbus, and then essential feature, operation mechanism and standardized information model are introduced respectively. Software and hardware are designed and developed in the control platform of variable air volume (VAV) air conditioning system. Based on the network architecture of Ubi-bus, it is potential for the solution of BAS integration in the practice application. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Ltd. committee of the 10th International Symposium on Heating, Ventilation and Air Peer-review under responsibility of Elsevier the scientific Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Conditioning. Air Conditioning. Keywords: Building automation system; Network architecture; Task-oriented; Development of key technology
1. INTRODUCTION With the rapid development of intelligent building technology, BAS integration technology based on BACnet[1], LonWords[2], XML/Web Service[3] and OPC[4, 5] has been mature and evolved from high integration to multilevel and multi-information [6] gradually. In the process of system integration, BAS still has following problems: 1) BAS is derived from industrial automation system, which network architecture could not meet the feature of equipment dispersed distribution and multiple fieldbus coexistence; 2) only a simple logic control could be achieved using solidified programs based on present control devices, which cannot support online-optimal control; 3) present systems have a lower automation level. The reason is that the BAS products are provided by different equipment * Corresponding author. E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.382
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Jili Zhang et al. / Procedia Engineering 205 (2017) 1286–1293 Jili Zhang et al. / Procedia Engineering 00 (2017) 000–000
1287
manufacturers, which improves the difficulty of networking and debugging and decreases system compatibility and integration efficiency. BAS control and management tasks have spatial distribution attribute, which means that building electromechanical equipment relies on the building space and distributes in each subsystem for different areas, and different functional services also depend on the building space [7]. This paper presents a network architecture of Ubi-bus, and then organization structure, working principle, the key technology and development process are demonstrated step by step. 2. DEVELOPMENT OF BUILDING AUTOMATION TECHNOLOGY From the perspective of function services, BAS is a typical distributed system with multi-task scheduling, in which different kinds of field electromechanical devices are scheduled and managed based on a kind of multi-task distribution mechanism [9] uniformly. Considering of structure and functional service demand [10], BAS development process could be divided into four generations according to that of traditional industrial automation system. First generation for electromechanical devices: The system only contains air compressor-powered pneumatic control devices and a small number of electrical control devices and has no complete equipment and fieldbus network, which could only implement local control based on the independent electromechanical equipment. Second generation for the controller: With the development of electrical automation technology, centralization control system with programmable logic controller and direct digital controller has been widely used. Therefore, private field bus has been established by different manufacturers. However, it is difficult to form a standard filed bus network, which results in the difficulties for sharing information and cooperating. Third generation for the information flow: With the development of information technology, distributed control system, which derived from centralization control system, has formed a complete control system network. Then, manufactures have converted control mode from based-collaborative to based-communication, which improves communication rate and information processing capability. Unfortunately, it is difficult to implement cooperation and share among different subsystems due to lack of attention on functional service demand. Fourth generation for the task: The development direction of BAS haves converted to networked, flattening and professionalization. Task-oriented system could be established with multi-task cooperation mechanism, which satisfies functional service requirements for electromechanical equipment in different subsystems. 3. PROPOSE OF UBI-BUS NETWORK OF BUILDING AUTOMATION SYSTEM 3.1. Analysis of building operation tasks In the perspective of building functional services, operation tasks in BAS mainly include: operating status monitoring, electromechanical device control and daily operation management. Each task is independent with others, and all tasks are considered as a whole and depends on information exchange based on building internal communication network. Details are as follow: 1) Operation status monitoring; 2) Electromechanical device control and operation management; 3) Operation management task. Building operation tasks are implemented with the electromechanical device and various subsystems, all of which constitute a set of building operation service system. As shown in figure 1, the operation task, which is implemented by electromechanical device, has spatial distribution attribution. Building operation tasks are distributed in the building space unit. Specified performance is: 1) the electromechanical device, which has the same function and interacts with each other, is distributed in the building; 2) Building operation task is mainly for collaboration control of the electromechanical device in different subsystems; 3) Electromechanical device in the same space, which belongs to different subsystems, usually implements the control action following the same functional requirements.
Jili Zhang et al. / Procedia Engineering 205 (2017) 1286–1293 Jili Zhang et al./ Procedia Engineering 00 (2017) 000–000
1288
3
变风量空调系统
新风系统 风机盘管系统
消防系统 电梯系统 冷冻站系统
Fig. 1. (a) Spatial distribution attribute for the building operation task; (b) Conformance to requirements for the same space operation task
3.2. Basic characteristics of Ubi-bus network To solve practical engineering problems, the mode of BAS integration need to be changed. During the design process, functional requirements and roles of each subsystem need to be paid attention. In the global perspective, BAS could be considered as a multi-task set, in which general description and relationship are corresponding between functions and the tasks, depending on electromechanical device units. For instance, air conditioning unit could provide supply air volume and supply air temperature adjustment function. Control strategies (constant air pressure control, variable air supply pressure control, and total air volume control, etc.), which could be seen as variable tasks, need be implemented at the same time. There is a generalized relationship between functions and tasks in the building space unit, which makes a diversification of functions for electromechanical devices. That is to say tasks under different working conditions are solved by different methods using the same electromechanical device. Therefore, this paper presents an Ubi-bus network architecture and system integration solution for BAS tasks, which have the spatial distribution characteristics. Characteristic 1: Bus type, delayering and arbitrary extension of the network architecture; Characteristic 2: Specialization, individuation and standardization of the task definition; Characteristic 3: Standardization, modularization and plug-play of the network equipment; Characteristic 4: Standardization, intellectualization and optimization of the information processing. 3.3. Operation mechanism of Ubi-bus network Linker, which is considered as the core component of automatic control system, mainly implements tasks with the electromechanical equipment in the building space units. Substantially, the study of the operation mechanism should consider the topology of Ubi-bus network and electromechanical equipment, which is based on the distribution relationship of linkers. Figure 2 shows the operation mechanism of Ubi-bus network, which is a scheduling process based on the task of the linker standardized information model essentially. Tasks are divided into private tasks and public tasks according to the relationship between linkers and task classifications. Private tasks are only associated with single linker while public tasks are associated with multiple linkers. Public tasks can also divided into serial tasks and parallel tasks according to the data flow classification. For serial tasks, message will be transmitted from the network interface of i-linker to j-linker turn by turn, if the message is generated in i-linker and its purpose is j-th linker. For parallel tasks, the message information of i-linker is only transmitted to its adjacent linkers if the message is generated in i-linker.
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Linker C
Private task
Common task HVAC engeneer
Private task Developer
Common task
Linker A
Function A
Linker D
Function B
Private task
Private task
Private task
Common task
Linker E
Linker B Function C
Linker G
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Private task
Private task Linker F
Function D
Common task Electrical engineer Linker H
Private task
Fig. 2. The operating mechanism of the generalized fieldbus network
Above processes establish a link among electromechanical engineers, HVAC engineers and software engineers based on their cooperation with each other. Operating steps are described as follow: 1) Functional requirements of the controlled object are proposed by HVAC engineers. 2) Electromechanical engineers take standardized designs for electromechanical device units in the building. 3) Software engineers write appropriate software programs, which are based on the specific logical relationships for specified function. 3.4. Linker standardized information model Linker standardized information model is shown in figure 3. Linker is responsibility to connect to field electromechanical devices through their own IO modules directly and create network mappings by bounding ID and channels. Corresponding information is open-ended for electromechanical engineers, software engineers and end users, which makes the networking and configuration standardization at the field equipment layer. Based on the linker standardized information model, IO modules, which are produced by different manufactures, could be arbitrarily replaced after a simple configuration process under the condition that the extended IO module supports a standardized and general communication protocol. In this way, the correlation between the physical address of the electromechanical device and the variable address of the software program is greatly reduced. Furthermore, this could avoid a large number of networking and configuration work.
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Fig. 3. Linker standardized information model
Data transmission between linkers are bidirectional, which means each linker has two relatively independent network interfaces for network physical connection and addressing. If specified function and service demand is generated, corresponding task can be done through cooperating with several linkers. 4. DEVELOPMENT OF KEY TECHNOLOGY OF UBI-BUS NETWORK IN VAV AIR CONDITIONING SYSTEM 4.1. Ubi-bus network architecture of VAV system According to the control demand of VAV air conditioning system [11], system schematic diagram of VAV control platform based on Ubi-bus network is shown in figure 4. There are three layers in the platform, which includes Field M&C layer, field bus layer and area-ctrl layer.
Fig. 4. Schematic diagram of control platform for VAV air conditioning system
1. Field M&C layer includes all kinds of devices in VAV air conditioning system, includes: 1) electromechanical devices such as air conditioning units, air fan and terminal devices for the basic demand of VAV air conditioning system; 2) temperature sensors, pressure sensors, damper actuators, variable frequency devices and other devices which are responsible for system operation and adjustment; 3) linkers, which means control equipment with fieldbus communication interfaces.
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2. Field bus layer is the transmission medium in the terminal site, which is responsible for data transmission through RS-485 industrial fieldbus. Field bus layer, plays the role of connecting the controllers and linkers, is the transmission medium between Field M&C layer and area-ctrl layer. Linkers adopts standard, open-ended and general Modbus-RTU protocol in order to support most of the on-site electromechanical devices as well as other standard communication protocols. 3. Area-ctrl layer, which is mainly composed of programmable logic controllers, is the key part in the control system. In-site devices are monitored and controlled by a serial of logical operation, sequence control, parameter setting and arithmetic, etc. Area-ctrl layer is located between field bus layer and the wide area network, supporting most of standard communication protocols. 4.2. Design & development of linkers and control terminal 1. Linkers Linkers are mainly composed of extended IO modules, and the selection and configuration for terminals are standardized according to specified points of electromechanical devices. As shown in figure 5(a), IO extension modules in the linker adopts small and medium PLC extension modules produced by Dalian Technology Computer Control Engineering Company (DCCE). These modules have following characteristics: 1) Anti-interference ability all through the electromagnetic compatibility level-3 standard, and interfaces are equipped with isolated circuits for the stability; 2) Supporting the standard Modbus protocol for any third party I/O extension devices; 3) Supporting terminal removable, charged plug and other practical functions; 4) Small and saving space. 2. Intelligent control terminal Considering of the spatial distribution characteristics of VAV terminal equipment, this paper adopts SIEMENS S7-1200 PLC as the core-controller in the intelligent control terminal for VAV air conditioning system, which is shown in figure 5(b).
Fig. 4. (a) Linker; (b) Intelligent control terminal
Intelligent control terminal could be used for central air conditioning control system and provides multiple standard RS-485 communication interfaces for supporting ASCII, USS drive protocol, Modbus RTU and other standard communication protocols. Besides, intelligent control terminal has a separate human-machine interface so that the operating status of on-site electromechanical devices could been displayed and operated intuitively. Intelligent control terminal has monitoring and controlling functions, which are helpful and continent for the realtime operation management, such as human-computer interaction, network interaction, mobile APP and other functions. 4.3. Design and development of software As shown in Figure 3, each extended IO module has unique fieldbus address. Through strict correspondence rules between the electromechanical equipment and the IO module channel, standardized configuration work could been implemented between the IO module channel and the software address. This avoids the secondary development for the software program and provides a flexible system integration solution.
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According to the standard information model of the linker, the software development could be divided in two steps: 1) Configure standardization the information model of the linker and the extended IO module channel; 2) Compile the standardization information model of the linker, control algorithm logic and human-machine interface. Linker standardization information model is the basis of the software program development, while the channel address of the extended IO module could not be considered in the compile process of control algorithm and logic. Therefore, control algorithm and logic programs, which is the core of the software program, need not rewritten case by case. Software programs mainly includes initialization, linkers, human-machine interface, communication and control algorithm and logic. 1) Initialization: This part is responsible for setting initial values before the system implementation. For example, the damper need to be opened in the system start process to insure the fan safety. 2) Linkers: This part is equivalent to the central nervous of the entire software program, which is responsible to convert the digital signal into the standardization information model. 3) Human-machine interface: This part is responsible for the daily management and maintenance through the information exchange between machines and users, and specified functions includes basic information, operating status information, parameter setting, fault information, graph and report, etc. 4) Communication among subsystems: This part is responsible for communicating with other subsystems such as refrigerating station system, independent fresh air system, fire alarm system, etc. 5) Control algorithm and logic: This part is the core of the entire system software program which is responsible for realize the optimal operation of VAV system based on a serial of security logic, sequential control logic, on-line optimal control algorithm. 5. Conclusion This paper present the Ubi-bus network architecture for building automation control in aspects of the theory and the application. Firstly, this paper discusses the characteristics and development process of building automation system, and points out that the existing network architecture could not satisfy the new functional requirement. Secondly, this paper presents an Ubi-bus network architecture, then basic characteristics, operating mechanism and standardized information model are introduced, respectively. Taking the network control platform of VAV system for example, the design and development process of hardware and software are introduced based on the Ubi-bus network architecture. Results show that building automation system integration solution based on Ubi-bus network has great potential of practical engineering applications, and could make building automation system more standardized, generalized and intelligent. Acknowledgements The authors gratefully acknowledge the financial supports from the National Natural Science Foundation of China (Grant No. 51578102，51378005) This work is supported by National Key Research and Development Project of China No. 2017YFC0704100 (entitled New generation Intelligent building platform techniques) References [1] Edwards R. Intelligent Buildings and Building Automation. J. Construction Management and Economics. 29(2) (2011) 216-217. [2] Figueiredo J, J Sá Da Costa. A SCADA system for energy management in intelligent buildings. J. Energy and Buildings. 49(2012) 85-98. [3] HVAC application [Chapter 47] In Design and application of controls. American Society of Heating, Refrigerating and Air-conditioning Engineers, (ASHRAE), Atlanta. 201147. 7-8. [4] Jianbo Bai, Xiaosong Zhang. Building automation systems and integration technologies based on Web Services, J. Journal Heating Ventilating and Airconditioning. 35(11) (2005) 27-34. [5] Qi Shen. Studies on Architecture of Decentralized System in Intelligent Building. Tsinghua University. [6] Song W S, Hong S H, Bushby S T. A Performance Analysis of BACnet® Local Area Networks, J. HVAC&R Research. 14(2) (2008) 289305. [7] Yu Zhen, LI Huai. Research Progress of Building Automation Technology. J. Building Science. (10)(2013) 106-113
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[8] Yang R and Wang L. Development of multi-agent system for building energy and comfort management based on occupant behaviors. J. Energy and Buildings. 56(2013) 1-7. [9] Zheshen Zhao. Analysis of topological structure and developing trends of building automation systems, J. Journal Heating Ventilating and Airconditioning. 11(2012) 32-37. [10] Zhengyuan Xu, Shengwei Wang. The integrated system of the intelligent building based on OPC and WEB SERVICES middleware technology. J. Intelligent Building and City Information. (01)(2007) 42-45.