Automated Vision Based Inspection of Automotive Brake Assemblies

A fully automated brake inspection system was built using the latest in virtual instrumentation and machine vision technology in a period of 10 weeks, say Anand Chinnaswamy, P. Kannan and A. Ashok Kumar

Overview
To develop a reliable machine vision system for automated inspection of brake drum assemblies. The inspection is complicated due to variations in texture, glossiness, colour and shade of the components. Some components are assembled one on top of another which cause changes in background components to influence the inspection of the foreground components.
A highly reliable system was built using National Instruments Vision development module, LabVIEW & the newly introduced NI-IMAQ 1394 driver. IMAQ Vision Builder was used to develop the core image processing algorithms and for validating the developed algorithms on a large sample set.

Introduction
The customer is a Tier 1 automotive supplier of brake drum assemblies with customers both in India & abroad. In the past they have tried a number of different vision systems for brake drum assembly inspection, but have had very limited success. The main problems with the previous systems were the dependence on using pattern matching which proved to be inadequate to handle the wide variations & complexities in the assemblies.
The test requirements call for the detection of the following:

• Presence of various components
• Reversal of springs
• Proper Locking or engagement of components
• Direction of assembly of geared components
• Angular orientation of clips
• Position of brake linings
• Presence of threading in certain components
• Presence of lettering
• Gauging of diameters, lengths & thickness The customer was
  looking for a cost-effective test system that could meet the following requirements:
• Flexibility – The system had to have the capability to
  test various models ofbrake drums
• Reliability – Inspection results had to be reliable & consistent
• Networking – The test results had to be accessible over
  the local network
• Delivery –Aggressive delivery schedule of 10 weeks for complete
  inspection station

Fig. 2: Photograph Showing Brake Assembly on Fixture Mounted on Rotary Table.

• Compact footprint – Efficient utilisation of valuable manufacturing
  floor space

A 1280 x 960 pixel Sony Fire Wire digital camera was chosen, which had a lot of programmable features that were required for this application.
More than 12 parameters such as selection of shutter speed, filter, etc. could be configured from the application software.
It was planned to use the newly introduced IMAQ 1394 driver from NI for interfacing the camera.
From the beginning, the customer was very clear that they needed a vision system that had complete flexibility.
From their previous experience they were convinced that standard vision systems that were merely configurable were not suitable.
A demo of the National Instruments Vision Development module completely convinced them that this was the right product for their application.

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