Hemalatha Gopal - Schneider Electric India Pvt. Limited
Arunkumar Doraiswamy - Schneider Electric India Pvt. Limited
Schneider Electric is a global specialist in energy management that is leading the way in energy efficiency. In India, we design and manufacture integrated solutions for residential areas, business buildings, industrial areas, infrastructures, and data centers. Our research and development center in Bangalore has a product verification and validation (V&V) laboratory, where the V&V activities are handled by several automated test benches that cater to different tests that address various international and market standards.
Products designed at the various Schneider R&D hubs in Bangalore and across Europe are subjected to stringent tests to meet international standards. One such test is a mechanical endurance test to qualify product durability. The standards specify to test the product for normal operating conditions (on/off), abnormal conditions such as undervoltage and overvoltage, and other fault conditions. The product also has to withstand a minimum of 20,000 operating cycles. Conventionally, mechanical endurance tests are performed using pneumatic actuators and selector switches to keep count of the cycles, but this setup allows many factors to influence the end result. The measurement uncertainty of the result was very high. Also, the test conditions had to be monitored in person from time to time. These tests are performed frequently and around the clock. Hence, there was an urgent need to automate the endurance test process to achieve faster, more reliable, and more efficient results. We chose NI products to automate the bench because we could deliver a faster integrated solution. We developed a motorized test bench consisting of three stations to run independent tests on eight products at the same time. Faults occurring in the test are displayed in the user interface (UI) screen as well as communicated as an SMS message to the user. The user can remotely restart the application by replying to the SMS or shut down the test by sending a predefined message based on the failure. The test bench consists of a host PC running on a Windows OS, an NI cRIO-9073 real-time controller controlling three linear motion test stations for testing circuit breakers, another cRIO-9073 controlling three rotary motion test stations for testing products such as rotary switch handles, and another cRIO-9073 for running nonmotorized tests on products such as air circuit breakers and contactors.
In the endurance application on the host PC, the user defines the test sequences that need to be run, the drive position limits, and the operation cycles, which are saved into the corresponding real-time target. The test sequence represents the timing diagram of each input required for the test. The user can see the digital plot of the timing diagram on the screen, and the sequences that are saved can be uploaded later to repeat the test. In addition to the cRIO-9073, the linear motion test station consists of NI C Series modules including the NI 9237 simultaneous bridge module to measure the actuating force; the NI 9403 bidirectional digital I/O module for reading the electrical continuity of up to five product contacts; and the NI 9401 high-speed digital I/O (HSDIO) module for controlling the three NI P70530 DC drives and the three NI N32HRHJ stepper motors. The linear motion is controlled by a custom motion control algorithm on the field-programmable gate array (FPGA) to make the drives move the motor at a specific speed to the specified displacement. The control algorithm also ensures that the product is not broken when the product mechanism under test exceeds the specified force.
The rotary motion test station consists of a cRIO-9073 with the NI 9401 HSDIO module controlling the rotary motion of three P70530 DC drives and three NI N32HRHJ stepper motors. The NI 9403 digital I/O module is used to read the electrical continuity of the contacts. The custom motion control algorithm on the FPGA controls the rotary motion. The third cRIO-9073 includes NI 9403 modules to run the on/off tests on products such as air circuit breakers and contactors by switching the power supply to the relays on or off while monitoring the contact states.
The three CompactRIO devices are connected to a switch and then to the host PC. The UI screen displays the operating status of each station. Real-time communication to the host is achieved using shared variables. The program was designed in such a way that the host application can be updated to add more stations or enhanced without disturbing the individual stations since there could be tests running for a few days or a few months.
Failures occurring in the tests are displayed as faults on the screen. In addition to this, fault signaling SMS messages are sent to the user. When the product is set up for the test, the user has to enter their mobile number on the test station UI. When the mechanical endurance program is running, the SMS server application runs in the background. The general packet radio service (GPRS) modem is connected to the serial port of the host PC. Faults occurring in the tests are continuously polled and sent as a string message along with the phone numbers to the server program. The server sends the string as an SMS message to the user’s mobile phone. This is done by writing the automated test AT commands to the serial port. When the user receives a message, they can restart the test station by replying with the restart command. If the user has not replied to the message, a reminder is sent. A time-out message is sent if there is still no response from the user. The user can also send a shutdown message that cuts off the power supply to the particular station experiencing a failure, thereby saving power. The server application receives a reply string from the user and sends it to the client application from which the fault originated. This is based on a TCP/IP client-server architecture. The server application is programmed to handle fault signaling of multiple test benches running on different computers in different work areas.
Benefits of Using NI Products
The mechanical endurance test bench developed using NI products provides a deterministic, reliable test solution. The graphical programming style includes easier debugging methods and helped us reduce development time. Accurate drive position control and innovative, useful features such as load limitation, fault signaling, and control were made simple with the power of the high-speed FPGA modules. Using fault signaling via SMS proved beneficial because the test can now run without the user frequently monitoring it for faults. The laboratory is also now 10 to 15 percent more energy efficient because stations not in use or those that failed can be remotely turned off during long vacations, weekends, or even overnight.
At the Schneider V&V laboratory in Bangalore, the mechanical endurance test bench is just one of several automated test benches that were developed using NI products. We used an NI Volume License Agreement and software maintenance and support services from NI. Because of this continued support, as new versions of LabVIEW are released, we can incorporate new features in our test bench development and easily upgrade the existing software programs. Additionally, consultation given at crucial stages of the project with respect to design, deployment, and coding best practices from the NI support and service group was invaluable.
Using NI products, we created an integrated, reliable solution that caters to the different requirements in the setup. This reduced application development time and product testing time by almost 50 percent compared to using the conventional setup. We also significantly cut down on the measurement uncertainty factor in our end results.
Schneider Electric India Pvt. Limited
Global Technology Centre India,#88(P), “Sahasra Shree”, EPIP Industrial area, Whitefield Road
Bangalore - 560066