For automotive component manufacturing engineers who build test systems for instrument clusters, National Instrument’s imaging products provide tools for building low-cost machine vision inspection systems. Unlike other vendor’s solutions, National Instruments image acquisition hardware and image processing software can run in a deterministic and reliable software environment that easily integrates with other test equipment and measurement types.
Automotive instrument cluster suppliers are challenged with creating systems for testing instrument displays. Numerous types of automotive instrument clusters need to be tested, including large gauges for speed and RPM, smaller gauges for gas and temperature, status indicators for turn signals and system faults, digital and analog odometers, and digital status displays. Instrument clusters must be tested for functionality and interoperability under a variety of of test conditions. New models with unique features are being introduced every year, so test engineers must create test systems that are adaptable to new requirements.
Figure 1 A typical instrument cluster
The image shown in Figure 1 shows a typical test instrument cluster test article. An inspection test sequence for this model would:
The following steps represent the pseudcode for executing the inspection tasks. The inspection tasks as performed in the sample code are shown in Figure 2. The numbers in blue represent the test steps outlined.
Figure 2. Screenshot of the test sequence on the cluster image.
Figure 3. Closeup of the measurement to find the center of the needle
Figure 4 shows the state flow diagram for inspecting a series of instrument clusters.
Figure 4. Pseudocode State Diagram
There are a few issues that you should be aware of when setting up a system for cluster inspection. Understanding these issues can help you optimize the performance of your test system.
There are also some techniques that leverage prior knowledge of the test article geometry that can be used to improve execution time. For example, in the test step 3 above, the search Region Of Interest (ROI) for the icons could be defined with a very narrow tolerance, which would allow the pattern matching to run more quickly.
When creating an instrument cluster inspection system for continuous measurements, sometimes the inspection cycle time is a critical parameter, i.e., the inspections needs to be accomplished within a specific time. The best solution for this requirement is to use a system based on the LabVIEW Real-TIme execution environment. With LabVIEW RT, and the Vision Development Module for LabVIEW, you have all the tools you need to develop a complete machine vision application on a reliable, embedded platform. LabVIEW RT provides real-time programming and execution capabilities and the Vision Development Module provides the image acquisition, processing and analysis functions. Using this platform would allow the system to run in a time-bounded manner. For implementation details and limitations, please refer to the IMAQ Vision for LabVIEW User Manual.
Recent advances in Automotive test applications have required tighter integration with other measurement and automation devices. National Instruments IMAQ hardware is designed to integrate seamlessly with NI data acquisition, CAN and motion control hardware. You can use the real-time system integration (RTSI) bus for PCI or the PXI trigger bus to distribute timing and triggering signals among National Instruments I/O devices.
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Example Program for Cluster Inspection