Sanka Hettiarachchi - Providev
Kevin Kho - Technologies Unlimited
Bringing Industry to the Classroom
Giving students a hands-on industrial experience has always been a goal of tertiary education. The closer the experience to the actual industrial application, the better the understanding of the concepts involved and the real-world challenges that students might face. Educators in the Nanyang Technological University Chemical Engineering Department had a vision to create a fully functional bioreactor process plant with which students could produce yogurt in a lab.
The idea was to create the bioreactor plant with four bioreactors and proportional-integral-derivative (PID)-controlled water heating, where students could monitor and control the temperature set points with tablet PCs that display real-time data. By studying the various outputs, the students were to validate the process operations and also determine the heat balance by analyzing the logged process data. We aimed to create an experience as close to the real world as possible.
This vision was our challenge during the preliminary discussion conducted by Mr. Kevin Kho, formerly with Nanyang Technological University, together with Providev and NI. Our mission was to create a state-of-the-art process plant and tablet PC-integrated application.
Providev, an NI Alliance Partner with more than eight years of LabVIEW development experience, was introduced to the customer by the NI sales team to support project development and integration. The requirements were perfectly within reach of the CompactRIO platform and LabVIEW. The newly launched Data Dashboard for LabVIEW with improved features was a timely release which connected the table with minimum cross-platform development effort. This, and strong NI Developer Community support, were critical in making this project a success.
The process control plant designed for the laboratory consists of the following subsystems (as shown in Figure 1):
- Reactors A,B,C, and D
- Return Water Line
- Cold Water Line
- Hot Water Line
- Steam Input
Three CompactRIO real-time controllers monitor and control the subsystems. Two cRIO-9075 controllers share control of the four reactors, whereas all utilities (hot and cold water temperature and water reservoir levels) are controlled by one. All parameters are monitored in real time and sent to the instructor PC through Ethernet, and then to student tablet PCs through WiFi (Figures 2, 3, and 4).
Meeting Requirements with the Right Tools
The reactor parameter monitor and controller we needed must:
- Run a temperature control loop with resistance temperature detector (RTD) sensor feedback and solenoid valve actuators
- Monitor RTD sensors and 4-20 mA sensors; control 4-20 mA analog actuators and 230 VAC solenoid actuators; read 24 V industrial I/O; and perform frequency measurements
- Provide fast development and deployment to complete the project within a tight schedule
Offer easy monitored-data viewing from the tablet PC and the ability to send certain control signal commands from the tablet
- PCs to the controllers
- Be small and strong, given the limited instrumentation cabinet space
- Fulfill design requirements with maximum cost savings
During the requirements analysis, we determined that a small CompactRIO system would be ideal for the application. The wide range of C Series modules available for CompactRIO meets all required types of control and measurement signal interfacing. Because the C Series modules contain built-in signal conditioning, sensor layout and connections were simple and neat. We selected the following modules:
|| Sensor/Actuator Connectivity
||8-Channel, ±20 mA, 200 kS/s, 16-Bit Analog Current Input
||Directly connect pH sensor signals for monitoring
||4-Channel, 100 Ω RTD, 24-Bit Analog Input Module
||Directly connect all RTD temperature signals that provide the feedback measurement
||4-Channel Relay [30 VDC (2 A), 60 VDC (1 A), 250 VAC
|Directly actuate 230VAC solenoid valves for water flow control
||8-Channel, 24 V to 60 V, 250 µs, Sinking/Sourcing Digital Input
||Water level sensor measurement and pulse frequency measurements for flow sensors
||4-Channel, 100 kS/s, 16-Bit, 0 to 20 mA Analog Output Module
||Actuate air-actuated valve that controls hot water utility tank heating
Table 1. CompactRIO Module Signal Connections
A 2 Hz temperature control loop was sufficient to meet the reactor and hot water temperature control requirements. Therefore, we decided to use the NI Scan Engine Interface to accelerate our development process. The NI Scan Engine interface provided basic functionality and low-level FPGA code for the selected modules. To get the basic I/O connections ready for testing, our developers only had to configure the LabVIEW project by inserting the modules and the I/O configurations in the LabVIEW project. Using the NI Scan Engine, we were controlling and monitoring signals without wiring a single wire of code.
Getting a Head Start with Sample Projects
Once the initial system requirements were set and I/O connections verified, our next step was to determine application system architecture. The LabVIEW in-product sample projects were invaluable during this stage because they gave us a scalable, well-documented starting point that perfectly fit our overall system requirements. The "NI LabVIEW Real-Time Control on CompactRIO (RIO Scan Interface)" sample project template that we used included extensive documentation that clearly indicated how the code worked and useful comments for adding and modifying functionality.
The sample project wizard in LabVIEW helped us create a fully functional project inclusive of the Scan Engine interface for CompactRIO, a real-time application, host PC communications, and a sample monitor and control user interface. We organized all code neatly in a scalable folder structure. As developers, we truly appreciated the efficiency of the built-in system-level integration support in LabVIEW, and knew our choice of development framework truly set us ahead of the pack.
With the above project as a starting point, the development team customized and modified the template project to suit the fine details of the application. At the end of the project, we extended the template to three CompactRIO systems and implemented many additional features on top of the built-in project template.
Tablet PC Integration Without Cross-Platform Development
The customer had a vision to create a next-generation learning experience. The ability to monitor, control, and interact with the process control system through iOS or Android tablets was an integral part of this vision. Our confidence in realizing this was only possible due to the Data Dashboard for LabVIEW app.
Using this free app on iOS, our engineers could create beautiful learning pages with real-time data updates, all received through the NI Shared Variables from the host PC. By utilizing the web services support in LabVIEW and the Data Dashboard app, we were able to display the monitored data with minimum latency, and students could enter their email addresses and request that the logged data be sent to them via email at the end of each laboratory session. Our effort was further reduced because the dashboards created on iOS were also fully compatible with Android tablets without any modifications.
At project completion, we successfully linked iOS devices to the system without any cross-platform development effort (Figures 5 and 6). The costs incurred for tablet development tools, equipment, and specialized app developers could have easily been in the tens of thousands of dollars. But the Data Dashboard app resulted in massive time and effort savings.
Helping students learn and experience the future of industrial systems requires a clear vision and the right tools. Using NI hardware and software equips us with the tools needed to meet such requirements with maximum efficiency and effectiveness.
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