Lakeshore Vision & Robotics

LVR has demonstrated clear ability to inspect gear mesh contact patterns in a production environment at production speeds. With 3 years of testing in production at a leading gear manufacturer, LVR has proven that the technology does indeed have the utility needed. This (patent pending) technology is now available at costs that are attractive and with capability for both inspection and for part tracking.

The key to this development was our concentration on computerized vision inspection methods where we let the gear manufacturing experts provide the inspection criteria. LVR then concentrated on selection of various technologies to provide the needed functionality. Since previous attempts at this technology by others ended in failure, LVR felt that it needed to prove out the technology's utility before applying for a patent, a technology developed by LVR years before the first installation. Our first system was installed at Plant 2 at American Axle & Manufacturing in Detroit. Following this installation, testing proceeded for over three years in various phases. A second generation of product is being designed and offered for sale based on this first system.

The inspection is performed by using the gear teeth themselves to trigger strobed acquisition of images of the gear teeth. Images of each gear tooth are acquired for the full (in this case) ring gear on both drive and coast sides by two cameras simultaneously triggered. Images are then analyzed to find the contact pattern locations and shapes around the gear. This permits knowing that each tooth has a good or bad pattern, and the system also checks for the pattern wandering heel-toe or top-root. Customers set their own inspection regions and criteria, and assign judgment signals to whichever digital output they want, together with an alphanumeric name that shows up on the inspection screen.

Figure 1: Analysis screen showing the lcoation (x and y postions) and sizes (heights and widths) of contact patterns on each tooth. The first graph is a linear plot and the second a radial plot, for both drive and coast sides. Runout on the coast side is clear by the sinusoidal pattern.

A second feature of the system is the ability to take in a serial number from RFID tags or barcodes (for example,) and use this in file names for archival storage of inspection results for each gear. Furthermore, since the images are available for analysis, these images can be turned into files (jpeg, bitmap or other) that can be stored for later retrieval. Together with time/date stamps for each inspection, a part of known serial number can be traced to the specific time and inspection results achieved.

Two other aspects of LVR software are important. The first is that LVR has diagnostic modes that permit storing away complete sets of inspection data, including images and inspection parameters used. Then, by either modem or broadband connection, servicing can start with simple diagnostic file transfers to LVR for further analysis. This is aided by the second feature. LVR programs are written to recognize whether or not cameras are connected. If not, the program automatically goes into an emulation mode (which is also available if the cameras are connected and running) that permits reading in diagnostic files and re-running the analysis with either the parameters used in the initial analysis, or parameters set by the user for that inspection. In the opinion of LVR, this represents the first success in automated inspection of gears at production speeds without the need for a subjective, human inspector. Further advances are already completed, and others planned.

Graphical and text analysis results are provided for the operator and engineer. A linear plot of horizontal (toe-heel, or "PosX") position is shown figure 1 in red. Notice that the heel toe position on the drive side is constant around the gear, whereas on the coast side, there is clear runout with the pattern moving toward the and away from the heel (away and toward the coast.) A clear defect in the coast side that does not show in the drive side in nearly as pronounced a manner. Data for reproducing these graphs is sent to an engineering directory for later reproducing this graph by a simple viewer program.

Figure 2: Full scren during operation of experimental system showing the images being inspected, I/O status, inspection results, and some simple control buttons. Other screens are password protected.

Figure 3: System Main Control Station

The entire operator screen is shown in Figure 2. A simple digital I/O display indicates both the status of signaling on the inputs to the inspection computer, and the results of the inspection on the outputs. The large text box shows results of position information, pattern match quality and other inspection results in text form for use on the line. Figure 3 shows an industrial workstation holding electronics for the gear contact pattern inspection system, including a touchscreen and air conditioning (both options).

Figure 4: One prespective system schematic for the LVR gear contact pattern inspection system.

Figure 5: A second perspection showing more of a camera eye's view.

Figures 4 and 5 show two schematics at different perspectives of the camera system. In this case, the ring gear is in a third member assembly. A through beam optical sensor is used to trigger image acquisition as each tooth passes. When all of the desired images are acquired, the system analyzes the images for contact pattern features, and reports out the results in detail on the screen, both in text and graphically (see Fig. 3 above).