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XPS-Q8 Controller
8.1.2
Trajectory Conventions
When defining and executing a Line-arc trajectory, a number of rules must be followed:
• The motion group must be an XY group.
• All trajectories must be stored in the controller's memory under ..\public\trajectories
(one file for each trajectory). Once a trajectory is started, it executes in the
background allowing other groups or positioners to work independently and
simultaneously.
• Each trajectory must have a defined beginning and end. Endless (infinite)
trajectories are not allowed. Although, N-times (N defined by user) non-stop
execution of the same trajectory is allowed. As the trajectory is stored in a file, the
trajectory's maximum size (maximum elements number) is unlimited for practical
purposes.
• Two types of Line-arc trajectory elements (segments) are available: lines Line(X,Y)
and arcs Arc(R,A) (Radius, SweepAngle). Any Line-arc trajectory is a set of
consecutive line or arc segments. The line segments are true linear interpolations y =
A*x + B, the arc segments are true arcs of circles (x - x0)
• A Line-arc trajectory forms a continuous path, so each segment's final position is
equal to the next segment's starting position. However, as the segment's tangential
angles around the connection point of any two consecutive segments may not be
continuous, there might be velocity discontinuities from one segment to next. For
reference, this discontinuity is categorized as R0, wherein the position is continuous,
but velocity is not. An excessive velocity discontinuity at joints can damage the
stages, so the trajectory definition process must take this into account.
• Each Line-arc trajectory element is defined relative to the trajectory starting point.
Every trajectory starting point has the coordinates (0,0), which has no relation to the
zero position of the positioners. All trajectories physically start from the current X
and Y positions of the XY group.
8.1.3
Geometric Conventions
The coordinate system of a Line-arc trajectory is an XY orthogonal system.
The X-axis of this system correlates to the XPositioner and the Y-axis correlates to the
YPositioner of the XY group as defined in the system.ini.
The origin of the XY coordinate system is in the lower left corner, with positive values
up and to the right.
All angles are measured in degrees, presented as floating point numbers. Angle origin
and signs follow the trigonometric convention: positive angles are measured counter-
clockwise.
8.1.4
Defining Line-Arc Trajectory Elements
A Line-arc trajectory is defined by a number of line and arc elements. The trajectory
elements are executed in the same order as defined in the trajectory data file.
Figure 25: Line-arc trajectory example.
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XPSDocumentation V1.4.x (EDH0301En1060 — 10/17)
Motion Tutorial
+ (y - y0)
= R
.
2
2
2
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