Individual Packet Identification System for Handwritten Characters
Eckelmann AG from Wiesbaden,
Germany, has modernized the stock receipt of a big warehouse based on
powerful standard components.
A descriptive example for modernizing an automated packet identification
system is the warehouse storage of the mail-order house WITT Weiden, Germany. The OCR has to
identify standard labels with handwritten characters by about 400 suppliers
around the world. The identification rate must be higher than 96%.
ECKELMANN AG, Mainz, developed this application based on HALCON that
perfectly fits to the existing environment and the existing proprietary
inventory control system.
Fig. 1: Packages from many different cultural areas deliver different
The goods are delivered via motor trucks, packed in packages of only three
standard dimensions. These boxes are guided trough several registration
conveyor belts operating automatic weighting, measurement, and
identification of the single boxes. The ascertained data are subsequently
transferred to the proprietary warehouse management systems. Identification
and measurement of the boxes is performed by an imaging system which was
substituted within a modernization process. The challenge was to identify
the boxes through arabic numerals (item number, quantity, and size) written
on standardized labels (Figure 1). That means that the system must be able
to identify and classify printed, stamped, and handwritten digits. This
functionality is widely known as Optical Character Recognition (OCR). Each
line must handle 5,000 packages a day with a capacity of about 40 packages
each minute. All components were selected in such a way that in the case of
a process upset it is sufficient to only change the PC. If necessary, the
recovering of the system can be done without problems within only one hour
because the hard drive mirroring is done via network.
Fig. 2: PC user interface displaying different identification results.
The imaging software is based on the standard software library HALCON 8.0
from MVTec. The application building is supported by HALCON's integrated
development environment (HDevelop). Affected by a long transport, the
labels often are polluted or damaged. Thus, the label localization and the
segmentation of the characters can be extremely complex.
The classification of the handwritten characters is partly multi-stage
processed by using different methods, for example the support vector
machine provided by HALCON. "The implementation of the image processing as
we planned it was only possible by several exclusively special HALCON 8.0
attributes", says Arno Dewald, ECKELMANN's responsible project
Fig. 3: The in-house relevant label with item number and storage
position is glued to the supplier's label.
After a first run of classification for a character sequence under the
appliance of neural networks, a plausibility check occurs in adjustment
with the total quantity of allowable results. If necessary, a second
classification process runs with an alternative method (particularly the
support vector machine has proved to be very powerful).
Furthermore, the machine vision software detects the size of packages.
Because only three different packages are permitted, the image software
must only detect one side of a package to conclude the size. Based on this
data, the system decides if two small packages or one bigger package are
stacked on one storage tray and location.
Fig. 4: Entire plant with standard PC, user interface, and labeling
The result of the new application exceeds all expectations of WITT. A first
evaluation over the time-frame of one month showed that the identification
rate was 100%. The processes of the OCR as well as the entire status of the
plant are visualized through clearly arranged user interfaces (Figure 2).
By data exchange with the warehouse management system, different
plausibility checks are processed. Against this plausibility check, the
automatic labeling of the package happens by a newly printed plain written
label (Figure 3).
"We are very content regarding the project settlement and the performance
of the application", says Sabine Schaumberger, project manager at WITT
Weiden. "Even during the fast-paced Christmas business, the launch of the
application without interrupting operations was no problem."
Authors: Winn Hardin, Contributing Editor, and Dr. Lutz Kreutzer,
Article kindly provided by Vision Systems Design.
Eckelmann AG is an MVTec Certified Integration Partner
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