LabVIEW over BACnet, a New Approach for Electromechanical Equipment Remote Monitoring System. Ping REN 1,2,a

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1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland LabVIEW over BACnet, a New Approach for Electromechanical Equipment Remote Monitoring System Ping REN 1,2,a 1 School of Information Engineering, Wuhan University of Technology, Wuhan, , China 2 Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA, UK a rp-2003@163.com Keywords: LabVIEW, BACnet Object, Remote Monitoring System, Electromechanical Equipment. Abstract. BACnet is a standard data communication protocol designed specifically for building automation and control systems. In BACnet network, each device is modeled as a collection of network-accessible, data structure called objects. LabVIEW is a graphical development environment for creating flexible data acquisition, device control and industrial automation applications at minimal cost. In this study, a remote monitoring system based on LabVIEW and BACnet was proposed, in which electromechanical equipment is described by a series of BACnet objects and LabVIEW provides a friendly unified human-computer interface for users. In order to evaluate the feasibility of this system, an experimental model was developed. Due to the characteristic of device-independent, not only can extend the scope of BACnet application, but also make different equipments monitored under the same platform becomes possible. Introduction BACnet (Building Automation and Control networks) is used to provide an open, vendorindependent, and interoperable communication protocol for building automation systems [1]. LabVIEW is a platform and development environment for visual programming language from National Instruments on a variety of operating systems [2]. At present, as an important part of modern advanced manufacturing technology, remote monitoring system plays an important role in ensuring the production safety and promoting the development of national economy. However, most of the remote monitoring systems use special communication protocols and text-based programming languages. Owing to the lack of interoperability and openness, it is difficult for them to share information and resources. In this study, a remote monitoring system based on LabVIEW and BACnet was proposed, which adopts object-oriented analysis and design method, each device is modeled as a collection of objects, and then defines services to visit or operate objects to afford a unified interface. Moreover, the visual components of LabVIEW provide a friendly human-computer interface for users. An experimental model was developed to evaluate the feasibility of this system, and test results show that the system combines advantages of LabVIEW and BACnet. Research Background LabVIEW Software. LabVIEW (short for Laboratory Virtual Instrument Engineering Workbench) is a National Instruments visual programming development environment, which is similar to C/FORTRAN/MATLAB development systems. However, other programming systems use text-based languages to create lines of code, and LabVIEW uses graphical programming language G to create programs in block diagram [2]. BACnet Object. BACnet provides mechanism by which computerized equipments with arbitrary functions may exchange information regardless of the particular services they perform. BACnet is based on a four-layer collapsed architecture that corresponds to physical, datalink, network and application layer [3]. LabVIEW over BACnet architecture is shown in figure 1. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-06/03/16,19:08:30)

2 3808 Frontiers of Manufacturing and Design Science In BACnet network, each device is modeled as a collection of network-accessible, named entities called objects. Each object is composed of a set of attributes or properties. The communication between devices is completed by reading or writing properties of particular objects. BACnet has defined the most widely used object types and their properties. In addition, it is free to create additional object types and services besides this standard already defined if desired [3]. The equipment how to be modeled as BACnet objects is shown in figure 2. Fig.1 LabVIEW over BACnet architecture Fig.2 Equipment modeled as BACnet objects Remote Monitoring System Model System Model. The remote monitoring system is composed of three layers. The first layer, web browser, its main task is used to accomplish information exchange between client and server. The second layer is server, which is used to complete the customer application functions. That is to say, LabVIEW server accepts request from client and connects with OPC server for processing, then returns the result to the LabVIEW server and transmits it to the client again. As for the third layer, the field controller is responsible for data acquisition, equipment control and communication with OPC server. The system structure is shown in figure 3. PC Bowser layer Remote PC Service layer Work Station LabVIEW + BACnet + OPC Server Router Internet BACnet IP BACnet Node BACnet Router Field Controller BACnet Network Field layer BACnet Router Device Object Analog Input Binary Output ReadProperty() WriteProperty() Non- BACnet Gateway BACnet Node Non-BACnet Network Fig.3 Remote monitoring system model In BACnet network, filed controllers are connected by MS/TP fieldbus. MS/TP is the unique fieldbus protocol in BACnet standard and it is widely used in BACnet products for its stability and reliability. As a mixed network, there are two kinds of non-reciprocity nodes exist in MS/TP network, master nodes and slave nodes. Token frame is used to regulate access to the medium [4-5]. Since each controller in this system needs to send data on its own initiative, the MS/TP network is only composed of master nodes to constitute a reciprocity network. Different MS/TP networks are connected by BACnet routers and static routing algorithm is used to transmit packs. OPC Server. OPC (OLE for Process Control) is an industry standard established by the world leading automation system, hardware and software companies and Microsoft for openness and interoperability. OPC server provides a public interface for different vendors hardware devices, software and systems, so that they can communicate with each other for co-operation. OPC server is used to realize OPC server object and group object based on control system's configuration information, and communicate with master controller of DCS system through OPC driver for data acquisition from fieldbus or set data value. In this system, MS/TP protocol is adopted as the fieldbus communication protocol. Because MS/TP is the unique fieldbus protocol in BACnet standard and it is widely used for its real-time performance. In addition, the use of MS/TP will enhance the compatibility with BACnet objects. An OPC server was developed specially for the electromechanical equipment monitoring system, which is shown in figure 4.

3 Applied Mechanics and Materials Vols Fig.4 OPC DA server B/S Model. LabVIEW remote panel technology is a means of communication based on B/S and TCP protocol, which can be used by visual and easy-to-use browser for remote monitoring and control. B/S (Browser/Server) model is an innovation or improvement to C/S (Client/Server) model with the rise of Internet. In this mode, web browser is the user s work interface, little logical affair is processed at client-side (Browser), while server-side (Server) deals with the most logical affairs. The greatest advantage of this model is that it is easy to maintain and upgrade, because all clients don t need any maintenance and all operations are served for server [6]. LabVIEW Remote Release. B/S-based LabVIEW remote panel technology doesn t need programming when compared with directly using of lower-layer TCP functions. It is easy to use browser for remote monitoring and control, before that just need to configure network parameters. Namely, the server acquires data and then transmits the real-time interface to client which can be viewed by browser. In order to enhance the network security, it is necessary to set up LabVIEW before the interface released to network. Browser access list shows the browser addresses having rights to access the web server and different browsers have different privileges [7]. Definition of BACnet object. In this system, all equipments are modeled as Device Object, Analog Input Object, Analog Output Object, Binary Input Object and Binary Output Object that corresponds to equipment itself, Analog Input/Output and Digital Input/Output hardware. The example codes to complete BACnet object is shown as follows: Typedef Struct { BACnetObjectIdentifier Object_Identifier; //Object Identifier CharacterString Object_Name; //Object Name BACnetObjectType Object_Type; //Object Type BACnetObjectStatus System_Status; //System Status BACnetCurrentValue Current_Value; //Current Value BACnetServiceSupported Protocol_Service_Supported; //Supported Service Type BACnetObjectTypesSupported Protocol_Object_Types_Supporte; //Supported Object Type } Bacnet_Device; //Device Object Bacnet_Device bacnet_device; //BACnet Device Object Instance ReadProperty(Device_name,Object_type, Object_instance, Object_property ) //ReadProperty WriteProperty(Device_name,Object_type, Object_instance, Object_property ) //WriteProperty LabVIEW Mixed Programming with BACnet. LabVIEW contains a great deal of subprograms and function libraries, so the users can quickly create their own data acquisition and control systems. But in many systems, there is a need for complex mathematical calculation between the acquired data and the output result. If only use LabVIEW G graphic language, not only increase the programming difficulty, but also reduce the implementation efficiency. While using the traditional text-based programming language, then it would be more concise and efficient. C language is a widely used programming language. Make use of CIN technology, users can pass any data structure to CIN. Under normal circumstance, make use of CIN will obtain higher efficiency because the data storage format of LabVIEW is same with that of C language [8].

4 3810 Frontiers of Manufacturing and Design Science To implement BACnet protocol in LabVIEW is very difficulty. Furthermore, the more complex the procedure is, the lower efficient the system performs. Therefore, this system uses LabVIEW and C mixed programming. CIN node calls BACnet protocol to complete the data transmission for LabVIEW to use and process. Experimental Model and Test Results Experimental Model. In order to evaluate the feasibility of the proposed remote monitoring system based on LabVIEW and BACnet, an experimental model was developed as shown in figure 5. The experimental model consists of Device0 (D0), Device1 (D1), Gateway, Work Station (WS), Monitoring PC, VTS (Visual Test Shell for BACnet), Binary Output (BO) and Analog Input (AI). The MS/TP protocol is adopted as fieldbus, all nodes in this network are configured as master nodes. The baudrate is and two master nodes occupy the same network bandwidth. Monitoring PC WriteProperty Internet BACnet/IP LabVIEW + VTS Test BACnet Object + IIS + OPC Server Work Station ReadProperty RS-232 MS/TP Fieldbus RS-485 Device 0 Binary Output Gateway Analog Input Device 1 Actuator Sensor Fig.5 Experimental model Visual Test Shell for BACnet (VTS) is an application used to test BACnet functionality of various devices in building automation systems [1]. Work Station is the heart of this system, which consists of LabVIEW software, BACnet protocol and OPC server, and it is responsible for data acquisition from sensor, receiving control commands from users and then passing them to actuator. VTS sends WriteProperty and ReadProperty requests to D0 and D1 to test the validity of BACnet protocol through the responses of D0 and D1. Monitoring PC, as a human-computer interface, it is responsible for the surveillance of system operation, and even can control the system wholly if the browser within the power of server. Test Results. BACnet confirmed ReadProperty and WriteProperty services, the most commonly used application services in BACnet system used by a client BACnet-user to request or set value of one property of one BACnet Object, are used to test BACnet Binary Input Object, BACnet Binary Output Object and Device Object [3]. VTS sends a control command to BO using BACnet_WriteProperty_request, and D0 replies the result using BACnet_WriteProperty_response containing the execution result. The VTS test result of WriteProperty service on D0 is shown in figure 6. VTS sends a BACnet_ReadProperty_request to D1 to read the value of AI and D1 replies with BACnet_ReadProperty_response containing the current value. The VTS test result of ReadProperty service on D1 is shown in figure 7. Fig.6 VTS test result of WriteProperty service Fig.7 VTS test result of ReadProperty service When arrangement and release of this remote monitoring system finished, the real-time operation condition of this system can be seen on the remote monitoring PC by web browser. The current value of temperature sensor and binary output are shown on the web page instantaneously. It has a good interoperability and the web page is shown in figure 8.

5 Applied Mechanics and Materials Vols Fig.8 Web page of remote monitoring system Conclusions This remote monitoring system based on LabVIEW and BACnet objects is an innovation which applies BACnet standard in equipment monitoring area. It makes full use of BACnet and LabVIEW s advantages, shields the equipment details to accomplish a simple, high universality, user-friendly, open and easily extend remote monitoring system. The OPC server provides a public interface for different vendors hardware devices, software and systems. It makes control processes of different systems and equipments in factory automation can communicate with each other. Therefore, it has a very broad application prospect, not only illuminates the research on different equipments monitored in the same platform, but also has a great influence on promoting the popularization of BACnet standard in China. Acknowledgement This paper was supported by the National Natural Science Foundation of China ( ). I hereby express my thanks to Hubei Key Laboratory of Broadband Wireless Communication and Sensor Networks for help in conducting the experiments. References [1] IS , Building automation and control systems-part 5: Data communication protocol. ISO, [2] National Instruments Corporation. LabVIEW user manual, Texas City: National Instruments Corporation, [3] ANSI/ASHRAE. Standard BACnet: A Data Communication Protocol for Building Automation and Control Networks, Atlanta: American Society of Heating, Refrigeration, and Air-Conditioning Engineers Inc, [4] Quan LIU, Ping REN. Design and Implementation of MS/TP in Embedded System, ICIEA2007, Harbin, May [5] W. S. Song, S. H. Hong, S. T. Bushby. A Simulation Analysis of the BACnet LANs, NISTIR 7038, National Institute of Standards and Technology, October [6] Fong A C M, Hui S C. An Intelligent Online Machine Fault Diagnosis System, Computing & Control Engineering Journal, [7] National Instruments Corp. LabVIEW Simulation Interface Toolkit User Guide, October 2003 [Online]. Available: [8] National Instruments Corp. Getting Started with LabVIEW, April 2003 [Online]. Available:

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