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XPS-Q8 Controller
8.0
Trajectories
XPSDocumentation V1.4.x (EDH0301En1060 — 10/17)
The XPS controller supports 3 different types of trajectories:
The Line-arc trajectory is a trajectory defined by a combination of straight and curved
segments. It is available only for positioners in XY groups. The major benefit of a Line-
arc trajectory is the ability to maintain constant speed (speed being the scalar of the
trajectory velocity) throughout the entire path, excluding the acceleration and
deceleration periods. The trajectory is user defined in a text file that is sent to the
controller via FTP. Once defined, the user executes a function to begin the trajectory
and the XPS automatically calculates and executes the motion, including precise
monitoring of the speed and acceleration all along the trajectory. Simply executing the
same trajectory more than once results in continuous path contouring. A dedicated
function performs a precheck of the trajectory which returns the maximum and
minimum travel requirements per positioner as well as the maximum possible trajectory
speed and trajectory acceleration that is compatible with the different positioner
parameters.
The spline trajectory executes a Catmull-Rom spline (which is a 3rd order polynomial
curve) on an XYZ group. The main requirements of a spline are to hit all points (except
for the first and the last point that are only needed to define the start and the end of the
trajectory) and to maintain a constant speed throughout the entire path (except during
the acceleration and deceleration period). The definition and execution of the spline
trajectory is similar to the Line-arc trajectory with similar functions for trajectory pre-
checking.
The PVT-mode is the most complex trajectory and is only available with MultipleAxes
groups. In a PVT trajectory, each trajectory element is defined by the end position and
end speed of each positioner plus the move time for the element. When all elements are
defined, the controller calculates the cubic function trajectory that will pass through all
defined positions at the defined times and velocities. PVT is a powerful tool for any
kind of trajectory with varying speeds and for trajectories with rotation stages or other
nonlinear motion devices.
8.1
Line-Arc Trajectories
8.1.1
Trajectory Terminology
Trajectory: defined as a continuous multidimensional motion path. Line-arc trajectories
are defined in a two-dimensional XY plane. These are used with XY groups. The main
requirement of a Line-arc trajectory is to maintain a constant speed (speed being the
scalar of the vector velocity) throughout the entire path (except during the acceleration
and deceleration periods).
Trajectory element (segment): an element of a trajectory is defined by a simple
geometric shape, in this case a line or an arc segment.
Trajectory velocity: the tangential linear velocity (speed) along the trajectory during its
execution.
Trajectory acceleration: the tangential linear acceleration used to start and end a
trajectory. Trajectory acceleration and trajectory deceleration are equal by default.
90
Motion Tutorial
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