2018 International Forest Industries IFI Feb March 2018 Digital | Page 31

OPERATION FOCUS – DELTA COMPUTER SYSTEMS
length with little space between
each machine. Fast motion is
needed to get the machines into
position between each log or cant,
but slow, precise motion is needed
when curve sawing or chipping.
“It is a testament to the
flexibility and multi-axis
synchronization ability of the Delta
controllers that just five motion
controllers were able to coordinate
all the hydraulic motion in the
line,” said Giguere. Table 1 shows
the functions controlled by each of
the motion controllers.
Delta’s Plot Manager, another
component of RMCTools, was used
to monitor how the actual motion
differed from target motion during
an operational cycle. It was using
the Plot Manager that the Prologic+
team identified a problem with
tuning the motion of the gang saw
wiggle box.
“The wiggle box moved on
a smooth oil bearing, but it
wasn’t smooth enough,” said
Delta President Peter Nachtwey,
who helped with the axis
tuning. “Making the problem
worse was the fact that two of the
cylinder diameters were too small,
so the system had a low natural
frequency and was not as stiff as
it should be, which made it more
susceptible to stick-slip.”
When the wiggle box was
moved quickly between cants, the
problem didn’t manifest itself,
but during the curved sawing of
boards the motion from side to side
The new automated
sawline has increased
the mill’s production
by some 140%
Francois Giguere,
Prologic+
and angle changes were relatively
slow, so vibrations could be felt by
touching the machine and easily
seen on the plots. The vibrations
affected the precision of the cuts
LUMBER PROCESSING
and could cause maintenance
problems if allowed to continue.
To overcome the friction
problem, Delta’s Nachtwey
recommended that the Prologic+
engineer tune one of the control
algorithms operating the wiggle
box to increase the gain of the
acceleration parameter, which gave
more power to the actuator at the
start of each move operation.
“The second derivative gain is
applied to the error between the
target and actual accelerations,”
said Nachtwey. “Second-order
tuning helps a lot to overcome the
effects of stick-slip.”
The actuator tuned up easily
after changing the tuning to
acceleration control using Delta’s
auto tuning procedure. The tuning
process took less than 10 minutes.
“The new automated sawline
has increased the mill’s production
by some 140% in board feet
compared to the old mill that
burned,” said Giguere. “And the
new mill is safer and easier for the
operators to run.”
Motion Controller # Axes Controlled Function
RMC #1 8 Rolling the log before chipping and
moving 1st set of canter heads left
and right up and down to produce
two flat sides
RMC #2 4 Roll cant onto flat side after canter,
and cant turner (on flat face) to
align the “horns” of the cant to one
side for the 2nd set of canter heads,
profiler, and gang saws
RMC #3 4 Moving 2nd set of canter heads left
and right to make it a four-sided
cant
RMC #4 8 Move the profiler heads to edge the
4 corners of the cant
RMC #5 6 Moving the gang saw “wiggle box”
to cut the cant along the curve
based on profile provided by the
scanner
Table 1. Five RMC 150 electrohydraulic motion controllers precisely handle motion tasks in the new Scierie Lapointe sawline
Figure 2
The canters, profilers and gang saws manufactured by PHL with optimizing and motion programming by Prologic+
International Forest Industries | FEBRUARY / MARCH 2018 29