Solutions for a Remote HMI System

Publish Date: Aug 24, 2016 | 0 Ratings | 0.00 out of 5 | Print

Overview

Many remote access options rely on network communication standards such as TCP/IP, UDP, OPC, or web services. Solutions like touch panel computers (TPCs) and thin clients are often used to separate the human machine interface (HMI) from the controller where secure, remote visualization capabilities are needed.

Touch Panel Computers

TPCs, panel PCs, desktop PCs, and other network-based HMI panels start to blur the line between local and remote accessibility when interfacing with the system. These primarily Ethernet-based solutions use common network communication standards such as TCP/IP, UDP, or web services to drive data between a server and client. In this server/client architecture, the controller or controllers act as the servers in the system to publish measurement data and accept control data points from the clients.

Using TPCs and desktop PCs as the client opens up more computational processing power due to a dedicated processor driving the HMI application. Having computing power at each distributed UI increases the hardware costs both up front and for maintenance. However, this type of HMI can drive more complex, graphics-intensive applications in addition to other components of the system.

LabVIEW software includes tools for UI development as well as functions for communication, data analysis, and data storage to quickly create and deploy HMI applications to communicate with NI TPCs and embedded real-time platforms such as CompactRIO.

You also can use a TPC client in your system for tasks such as historical data and alarm logging on the device, industrial bus and enterprise connectivity, or access control development. This expanded functionality is offered by the LabVIEW Datalogging and Supervisory Control (DSC) Module.

Resources
View the Different NI Touch Panel Computer Options

 

Thin Clients

Engineers often implement a “thin client” approach to achieve the most flexibility in accessibility with cross-platform support. Unlike a dedicated TPC or client-installed application, a thin client executes the zero-install UI on the client and relies heavily on the server for data retrieval, analytics, and logic execution.

The first step in this process is to identify the network protocol you want to use to communicate to this thin client. A popular method is HTTP-based web services, which simplify the low-level connection management that protocols like TCP/IP require. Web services are a standard option for web-based applications because they incorporate encryption and authentication security measures. The LabVIEW development environment already incorporates capabilities for the creation and deployment of web services. Refer to the Web Services Getting Started Series to learn more.

Another HTTP-based communication protocol that offers the benefits of this standard web technology approach is the OPC Unified Architecture (OPC UA) protocol. Used by numerous vendors, OPC UA is an open interoperability standard that provides an effective solution for integrating an HMI into a system featuring a variety of subsystem vendor components.

Once you determine your communication protocol, then you need to select your thin client technology. Two popular options for creating a thin client to interact with the system are mobile and browser-based clients.

Resources
Get an Overview of Web-Based Communication With a LabVIEW Application

LabVIEW Web Development Community
Why Does OPC UA Matter?

 

Mobile Client

If your system requires an interface to a mobile target, you can build a tailored native application for a specific smartphone or tablet. Because of the variety of software and hardware technologies in smartphones and tablets, investing in a mobile application can be expensive and requires experience in each of the mobile platforms supported.

To help you take advantage of these devices without requiring mobile programming experience, NI has created several tools for remotely viewing measurements and connecting to DAQ hardware.

Resources
View the NI Mobile Application for Interacting With Your System

 

 

Browser-Based Thin Client

The other option is a browser-based thin client implementation, which has gained popularity thanks to the ubiquity of the Internet and the associated browser software installed on virtually all consumer hardware devices.

A browser-based thin client is an ideal solution for a distributed system that is spread over a large area and has a high ratio of clients to servers. Since the visualization is contained within a standard web browser, it requires no additional software installation. Because tasks are offloaded to a central server, a thin client requires only limited processing power and storage. Centralizing the system’s applications enables easy hardware and software maintenance and upgrades. This results in a lower cost of ownership for high-volume client deployments compared to TPCs and other hardware solutions.

If you are considering a browser-based architecture, remember that it has the potential to consume more of the server-side processing resources, depending on the update rates and number of connected clients. It also requires knowledge of web page programming languages such as JavaScript, CSS, and HTML to create an attractive, interactive panel experience. See the resources at the end of this section for technology options that don’t require web programming as well as tips and tricks on creating a browser-based thin client.

Overall, lower unit cost coupled with browser accessibility and scalability makes a thin client a good solution for portable visualization systems.

Resources
Access LabVIEW VIs Over the Web or a LAN From Any Browser Using LabSocket

W3Schools – Tutorials and References for Web Development

 

Solutions for a Local HMI

Often you need to attach a local HMI directly to the controller to ensure operator or technician access. Usually in the same enclosure as the controller, these local HMIs are single units cabled or attached directly to the controller.

Learn more about Local HMI solutions.

 

 

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