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6. System Commissioning Trials
This chapter presents the procedures adopted for commissioning the adaptive
control system developed. It starts by showing the calibration procedures used for
adapting the welding models developed by Ogunbiyi [ref. 51] to suit the differences in
power sources and in jigging system. This includes the development of the stand-off
estimation models, along with the aspects involved in the integration of the different
parts of the system and the implementation and tuning of the process and stand-off
controllers.
6.1 Calibration of the welding models
In order to verify the validity of the previously established welding parameter
prediction developed for a Migatronic BDH320 [ref. 51] when a different welding
power source (BDH550) was used, initial flat position fillet welding trials were
carried out. Appendix H shows the technical specifications of the two power sources.
From the initial trials it was observed that the BDH550 produces a welding
voltage lower than the set-up voltage. This resulted in very spattery welds and some
very unstable situations. Previous work on the BDH320 showed no significant
difference between the set-up voltage and the welding voltage. Table 6.1 shows the
welding parameters used in the initial welding trials, along with the welding data
collected during the same trials by using the monitoring hardware outlined in sections
5.3 and 5.4 and the monitoring software CranMon. The welding trials were carried
out with the following fixed conditions:
" Plate thickness: 3.2 mm
" Length of weld: 232 mm
" Welding speed: 0.5 m/min
" Sampling rate: 5 kHz
" Number of samples per data window: 512
" Time interval between windows 0.25 seconds
Figure 6.1 shows the plot of the average welding voltage versus the set-up
welding voltage. The equation shown in the chart and below gives the linear function
that fits the data.
y 0.9107"V.,
(6.1)
The equation (6.1) was inverted and used to adjust the set-up voltage of the
previous welding parameters (see Table 6.1) to the levels that supposedly would
produce the required mean welding voltage. A new set of flat position fillet welding
trials was carried out to observe the process behaviour with the adjusted set-up
voltage. Table 6.2 shows the welding parameters used and the welding data collected.
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