Brooks Automation 6. Software Reference
Part Number: PF40-DI-00010 Rev. A Servo Gripper Controller Digital Inputs and Outputs
End of Travel Sensor
The PreciseFlex 23 N EGripper includes a sensor to detect the gripper closed to hard stop position.
The spring will return the gripper to this position if power is off and there is no plate in the gripper.
This sensor is wired to Digital Input 2 on the Gripper Controller Board which can be read at Digital
Input 210002. This input can be viewed in the Web Browser under Control Panels/Remote
IO/Network Node 2 IO. At power up this sensor can be checked to determine if the gripper is fully
closed, and thus not holding a plate. If the gripper is not fully closed it will be holding a plate, and the
operator should be directed to remove the plate before homing the robot, which will open the gripper
to the maximum hard stop. The 60 N servo gripper has an absolute encoder and position can be
checked after homing, which does not move the gripper fingers.
Grip Test and Squeeze Check
It may be desirable to check if a plate is gripped by checking the gripping torque value. The output
torque to the motor is available in Parameter 12304, value 5 in the parameter data base. For a non-
spring gripper, this value varies between 0 and 4378 tcnts for a maximum gripper force of 18N. For
a spring gripper, per above, for a portrait grip, the spring adds about 1600 tcnts to the squeeze and
for a landscape grip, it adds about 2200 torque counts to the squeeze. Since this value is taken into
account by the spring compensation and is offset from the torque commanded to the motor in
Parameter 12304, when checking Parameter 12304 to determine squeeze the spring compensation
must be subtracted from the torque value in Parameter 12304. For example, if the gripper is at the
portrait position and not holding a plate, it must servo against the spring. In this case the value in
Parameter 12304 will be about 1600 tcnts. To determine the effective squeeze torque, subtract
1600 tcnts from this value, which results in zero tcnts of squeeze force. If the value in 12304 is -
2700, then the gripper motor is squeezing with -2700 tcnts, and the spring is adding -1600 tcnts, and
the effective squeeze is -4300 tncts, or about 18 N. The exact spring compensation value is stored
in field 5 of Parameter 12331. For the best accuracy in determining effective squeeze force at any
gripper opening, subtract this value from the value in 12304.
Servo Gripper Controller Digital Inputs and Outputs
The Servo Gripper Controller PCA (GSB) adds three general optically isolated digital outputs and
three general optically isolated digital inputs to the standard digital I/O found on the Guidance
Controller. Like the other general inputs and outputs, they can be assigned for various control
purposes during system setup, or they can be used directly by a GPL procedure.
Unlike the controller's standard digital I/O that are directly accessed on demand, these I/Os are
scanned by the controller. The scanning period is nominally 4 milliseconds, so an application must
be able to handle a delay of up to 4 milliseconds for signal changes to propagate through the
system.
Effective with Revision 4 of the GSB board, two IO pins have optional assignments based on
jumpers. J4 is connected to pins 2 and 3 to connect Digital Input 1 to pin 6 and is connected to pins 1
and 2 to connect pin 6 to a line that goes back to the controller RS-232 RXD input. J7 is connected
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