Automated Function Testing of Automotive Seating Components Using NI LabVIEW with NI Motion

“We took full advantage of the built-in parallelism of LabVIEW and created a powerful application that consumed only moderate CPU resources and left plenty of overhead for the operating system.”

- Amit Bhalla, Sci-Mech Technical Services Inc.

The Challenge:

Developing a rugged load- and displacement-controlled system – that interfaces with servo motors, load cells, and encoders and connects to Windows OS platform databases, printers, networks, remote access software, bar code printers, and bar code readers – for the online production testing of automotive seat frames.

The Solution:

Using NI LabVIEW software and NI motion products combined with PXI technology to provide a cost-effective solution for production line testing that recognizes, via bar code, different products and tests them against appropriate parameters.

Author(s):

Amit Bhalla - Sci-Mech Technical Services Inc.
Patrick Allen - Sci-Mech Technical Services
John Purse - Sci-Mech Technical Services

 

Our client produces automotive seating components for leading automotive manufacturers. Its parts must meet the highest quality standards and be 100 percent functionally tested before shipping. In this particular case, we measured and recorded precise displacement parameters on every automobile seat part.

 

 

Our client required a timely and cost-effective solution for production line testing on several of its automotive seating products. The test fixture needed to recognize, via bar code, different products and test them against the appropriate parameters.

 

This project required a test fixture that was flexible – able to test multiple product types; fast – meet a predetermined cycle time; comprehensive – able to test for variables and attribute data; and intuitive – able to allow for inexperienced operators to use with confidence.

 

We at NI Silver Alliance Partner Sci-Mech Technical Services Inc. chose LabVIEW and NI motion products combined with a desktop PC and a remote PXI rack for controls and data acquisition.

 

Because we had a large number of parts to test, we developed an auto-eject system that automatically removed a tested product from the tooling. This streamlined workflow so that an operator could load and begin testing on a new seat frame while the previously tested seat frame was ready for packing. This design reduced unnecessary operator steps and significantly reduced cycle time.

 

 

Test System Design

Due to the high digital channel counts required for this project, a desktop PC alone could not support the required number of PCI boards. We selected an NI PXI remote chassis to perform the extensive data acquisition and to communicate to the PC-based controller. We also used two NI PXI-6511 low-cost, industrial digital input modules, which provided 128 bank-isolated 24 V inputs. With bank isolation, we could connect our sensors directly to save assembly time, reduce circuit complexity, and decrease cost. In addition, we used two NI PXI-6512 low-cost, industrial digital l/O modules for the 128 bank-isolated digital outputs, meaning that we could connect to devices directly from the module’s breakout box without having to put every signal through an optical isolator. With so many channels, this saved us not only setup time but also panel space.

 

We also used an NI PXI-6220 analog input module that offers full 16-bit resolution at 250 kS/s. This was ideal because our client’s specifications required very precise load measurements. We used an NI PXI-6602 counter/timer module to capture data from positional encoders, providing us with eight channels, each with a full 32-bit resolution. To control the four servo motors of the system, we used an NI 7340 four-axis motion controller. Full driver integration with the NI Measurement & Automation (MAX) configuration utility offered an intuitive GUI for both setup and troubleshooting.

 

Finally, we used a MXI-Express link,  the NI PCIe-8361, to connect our PXI rack to a PC. The NI PCIe-8361 features 110 MB/s sustained throughput and provides a transparent link where all PXI modules appear as a PCI board within the PC itself. MAX services simplified the setup process. Our developers quickly assembled and set up the PXI system fully  and took measurements sooner than we expected. We thought the out-of-box experience would take several days but were pleased to find that we had the system running within a few hours.

 

The LabVIEW Solution

The large number of sensors combined with the wide range of possible products to test presented us with a challenge in designing an intuitive user interface for operators. We considered this carefully because this client had no other equipment in its facility that was this complex. As a production line tester, this equipment had to be robust, simple, accurate, and safe to operate.

 

To assist in the software design phase and reduce overall programming time, our developers used the LabVIEW State Diagram Toolkit so they could concurrently visualize program architecture and develop code. With the LabVIEW State Diagram Toolkit, Sci-Mech developers could share machine operation concepts with Sci-Mech management and the client. With this design technique, we could spot potential problems, and Sci-Mech was able to improve on the original design concepts without losing any development time.

 

We also used NI Motion Assistant to set up the initial motion profiles. This tool helped us save hours of development time and was very useful in the initial setup of our servo motors. We could safely check the acceleration and deceleration ramp profiles and overall velocities of the automotive seat testing system before program implementation.

 

We designed this equipment to test two products independently but potentially at the same time. This presented a challenge for our developers to produce a GUI that displayed all relevant controls and data acquisition details in a format that new operators could easily navigate and understand. The LabVIEW front panel controls, specifically the “tabs” on the main GUI, gave us easy access to all the relevant test and diagnostic information and provided password-protected access to setup parameters.

 

We selected a dual-core desktop PC to communicate with the NI PXI-1042 seven-slot PXI chassis. With a dual-core PC, we took full advantage of the built-in parallelism of LabVIEW and created a powerful application that consumed only moderate CPU resources and left plenty of overhead for the operating system and other applications that our client may choose to run.

 

Author Information:

Amit Bhalla
Sci-Mech Technical Services Inc.
312 Alliance Road, Unit #1-6
Milton, Ontario L9T-2V2 L9T-2V2
Tel: (905) 693-0866
abhalla@scimech.com

Figure 1. Backframe tester with auto-eject capability
Figure 2. Schematic of the backframe tester