Using NI LabVIEW and PXI to Develop End-of-Line Skid Loader Test System

Author(s):
Wei Tung - Vi Engineering

Industry:
Automotive

Products:
PXI/CompactPCI, LabVIEW

The Challenge:
Building a turnkey system within 10 weeks to operate assembly, electrical, hydraulic, and engine/drive train tests on skid steer loaders.

The Solution:
Using LabVIEW 6i with PXI to provide reliable data acquisition and to monitor complex test sequences, as well as utilizing NI MAX to calibrate all channels to save costs and time.

Automating Tests with PXI
VI Engineering, Inc., an NI Alliance Program Select Integrator, provided a turnkey loader end-of-line test system (LTS) for a new manufacturing line for Case New Holland Corporation. The system, which tests skid loaders after final assembly for both the New Holland and Case skid loader models, includes four different test groups that run through an automated test sequence called "runtime test". We used a PXI-6508 embedded controller to control the following test sequences:

• Assembly tests: Inspect pass/fail tests on all assemblies. Assembly tests include visual inspections of decals and basic machine function.
• Electrical tests: Perform pass/fail tests on all electrical connections for battery, alternator, and lights.
• Hydraulic tests: Inspect all hydraulic tests and measurements for pass/fail performance. The software measures 4 and 14 µm (ISO 11171 standard) particle counts in the hydraulic oil using a PC-4000 particle counter. The software also tests boom lift (maximum breakout) force.
• Engine/Drive tests: Inspect wheel RPMs and dynamometer tests. Tests include wheel RPM (forward and reverse); wheel maximum torque (forward and reverse), maximum horsepower (forward and reverse), RPM versus horsepower analysis, and RPM versus torque analysis.

Meeting Production Line
Requirements with LabVIEW
We used LabVIEW to design a user-friendly application to inspect all functionalities throughout the test sequence. The software consists of the following user interface screens:

• Login screen
• Configuration screen
• Calibration screen
• Security manager
• Manual screen
• Runtime screen
• Exit

We also used LabVIEW to design a user-friendly interface that meets the requirements for the manufacturing production line. Any user must first login through a login screen that offers different privilege levels (operator, engineer and administrator). Because of our short time frame and low budget, calibrating all AI/AO transducers to set up a channel list and scaling data to convert into engineering units proved the most crucial point in the software development. However, the virtual channel setups in MAX helped us immensely, giving us added flexibility and ability.

In the manufacturing production line, safety plays an important role for workers. Our LabVIEW program monitors light curtains to stop test sequences when the curtains break. In addition, our LabVIEW-based software monitors digital signals to control an emergency shutdown switch. Engineers can debug or inspect each channel connected to the loader test instrumentation with the manual menu screen, which shows all analog and digital signal channels. This way, our customers can verify they have properly connected all channels and that all transducers work correctly.

Through the test configuration screen, users can select or deselect tests in the test sequence or rearrange the order of the test sequence. First, the user creates a general test sequence file in a Microsoft Access database file to define all test sequences. Then, through the LabVIEW database connectivity toolkit, the general test sequence appears under "Available Tests" column in the testconfiguration screen. The user can start with the general test sequence to define a generic test sequence for each model of the unit-under-test (UUT). For each selected test, the user can double click on the test item to edit the specific test parameters. The user can configure two types of tests in the test configuration screen. One is a visual test where a prompt screen invites a user to enter a pass/fail result into the software. The other test reads a value at a data channel and checks hi/lo limits for the test. For of test, a configuration screen allows the operator to set up the test information. The software then saves the test sequence and other important information for each UUT in a separate test configuration file. Also, the user can load up a previous test sequence to modify or to reuse.

The automated test sequence screen (runtime test screen) executes a test sequence defined in the test configuration screen by the user. The runtime screen shows all necessary information for the UUT and tests all four functional tests in sequence. For every test sequence, an appropriate pop-up screen leads the user to enter the results or to run the test. For all visual tests (both assembly and electrical tests), a generic numeric pop-up screen performs a visual/manual inspection of the UUT and enters the pass/fail result into the software. For the engine/drive test, and horsepower/torque test, a graph screen pops up to measure horsepower and torque by increasing torque in a series of steps and by adjusting a signal to the air brake in the dynamometer. After completing the test sequence, the user can generate a text report to print out or to save to a file in ASCII CSV format.

Conclusion
VI Engineering has developed a turnkey loader end-of-line test system to use for final production test for a skid loader vehicle manufacturer. Even though the requirements for the project were very demanding in terms of time, VI Engineering took full advantage of PXI and LabVIEW to deliver a system with maximum user flexibility and reliability. The software development with LabVIEW 6i gave us impressive ability to configure and run a test sequence easily. Also, MAX provided flexibility and capability that saved us time and money when setting up all channels and scaling transducers.

For more information, contact:

Wei Tung, Namdoo Moon, Jeremy Witikko, or Sundaram Raghuraman

VI Engineering, Inc.

Tel: (248) 489-1200

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