Text version of the page 
Text version of the page 
Examples: P-734, P-561, p. 2-68 ff . in the“Piezo Nanopositioners &
Scanning Systems” section. Piezo • Nano • Positioning Parallel and Serial Kinematics There are two basic ways todesign multi-axis positioning systems: Serial kinematics and
parallel kinematics. Serial kine-matics are easier to design andbuild and can be operated with
simpler controllers. They do,
however, have a number of dis-
advantages compared to high-
er-performance and more ele-
gant parallel kinematics sys-
tems. In a multi-axis serial kine-matics system, each actuator isassigned to exactly one degree
of freedom. If there are inte-
grated position sensors, they
are also each assigned to one
drive and measure only the
motion caused by that driveand in its direction of motion.All undesired motion (guiding
error) in the other five degrees
of freedom are not seen and
hence cannot be corrected in
the servo-loop, which leads tocumulative error.In a parallel kinematics multi-axis system, all actuators act
directly on the same moving
platform. Only in this way can the sameresonant frequency anddynamic behavior be obtainedfor the X and Y axes. It is also
easy to implement parallel
metrology in parallel kinemat-
ics systems. A parallel metrolo-
gy sensor sees all motion in its
measurement direction, not
just that of one actuator, sorunout from all actuators canbe compensated in real-time
(active trajectory control). The
results are significantly less
deviation from the ideal trajec-
tory, better repeatability and
flatness, as shown in Fig. 51. Piezo actuators Nanopositioning &
Scanning Systems Active Optics / Steering Mirrors Tutorial: Piezo-
electrics in Positioning Capacitive Position
Sensors Piezo Drivers & Nano-
positioning controllers Hexapods /
Micropositioning Photonics Alignment
Solutions Motion controllers Ceramic Linear motors & Stages Index Fig. 51. Flatness (Z-axis) of a 6-axis nanopositioning system with active trajectorycontrol over a 100 x 100 µm scanning range. The moving portion of this parallelmetrology positioner is equipped with ultra-precise parallel metrology capacitivesensors in all six degrees of freedom. The sensors are continually measuring the
actual position against the stationary external reference.A digital controller compares the six coordinates of the actual position with therespective target positions. In addition to controlling the scanning motion in the X and Y directions, the controller also ensures that any deviations that occur in
the other four degrees of freedom are corrected in real-time. 4-45 4-45
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