Festo HGPPI Series, Instructions Manual

Page: 88 / 192

5. Programming
5−12
Festo P.BE−HGPPI−PB−E N en 0605NH
5.3.1 Definition of the coordinate system
Definition of the offsets
The zero point of the coordinate system lies on the centre line
of the HGPPI−... (compare Fig.5/2: point P0). All dimensions
are measured outwards, starting from this zero point,
At the gripper zero point, the position of both gripper jaws is
zero. The gripping points on the gripper fingers can deviate
from this due to the finger geometry or the grip (inner/outer
grip). By defining an offset, the real dimensions of the grip
ping point can be worked with when specifying setpoint
values. For example, an opening when the gripper jaws are
completely closed is not zero, but the minimum distance
between the gripper fingers.
The gripper coordinate system can then be adapted to the
constructive properties of the gripper fingers.
The control always transfers the setpoint values or reads
the actual values in gripper finger coordinates. The closed−
loop controller, on the other hand, always works with the
jaw coordinates. If the offset is chosen to be the value 0,
the finger position and jaw position agree.
Depending on the gripping command, the transferred
coordinates are either absolute positions of the individual
gripper fingers (single jaw commands) or a combination of
the mid−position and opening (gripping commands).