ElmoMC Multi-Axis Motion Controller-Maestro Motion Control - Manual (Page 20)

In fact, the value defined as
r ≥ (vse) 2 /(vae*vac )
(by default vae = 0.9) must be used in
the calculations.
2.
Implicitly pre-defined by the user via smooth distance
d
along the line from the intersection
point (vsc = 3, vsd defined). This mode can be implemented to the line – line, circle – line
and line – circle trajectory intersections.
3. Calculated as a minimal possible for the given end velocity
V
end
and vector acceleration
AC
v
(vsc = 1).
Regardless of the
r
definition (pre-defined by the user or calculated by (1-1)) movement along the
switch arc is considered to be uniform with the constant tangent velocity
V = V
end
and constant
angle velocity
ω = V/r (1-2)
The intersection geometry imposes constraints on the switch arc radius. So the switch radius in use
r
must satisfy
(V
end
) 2 /AC
v
< r < r
max
(1-3)
Chapter 2 will consider all cases of the two shapes intersections and methods for the calculation of
the switch
radius limit value
r
max.
As a base value for the switch velocity is taken the preceding segment end velocity
V
end
defined
by the parameter vse. This value is considered as a limiting parameter that cannot be exceeded but
can be decreased. It’s also valid in case that polyline segments (preceding switch arc and the
following) are executed in the fixed velocity mode (vum = 3).
In switch mode vsc = 1, the initial value of a switch velocity equal vse and can be decreased to
build a switch arc trajectory equal to the integer number of PVT steps or milliseconds.
In switch mode vsc = 1, the radius of the switch arc is calculated as a minimal possible for the
intersection geometry and given vector acceleration/deceleration (input parameters vac/vdc)
meaning that the calculated value satisfies
(1-3). While the switch arc calculation is also taken into
account the requirement to build switch arc trajectory equal to an integer number of PVT steps. The
Motion Library is trying to build switch arc trajectory with velocity as close to the value given by
the parameter vse for the preceding segment as possible. The switch arc (or two arcs on both ends
of the segment) can take up almost all segment length that sometimes makes trajectory calculation
impossible.
As an example consider the following: segment initial velocity equal
V
o
,
end velocity
V
e
and
min (V
o
,V
e
)ΔT > ΔL (1-4)
(where
ΔL
– the length of the segment truncated by switch arcs,
ΔT –
standard PVT step). When
defining switch radius (input parameter vsr) for vsc = 2 mode or end velocity (input parameter vse)
for vsc = 1 mode, the user must take into account that it can significantly influences the whole
trajectory and in fact replaces the main part of a particular segment by switch arcs.
Maestro Motion Library Tutorial
MAN-INTUG (Ver. 1.7)
17