Atmospheric Single-Arm Robot
Troubleshooting
User’s Manual
Checking Limit Switch Status with the
RLS
Command
Brooks Automation
Revision 1
10-19
Checking Limit Switch Status with the
RLS
Command
Limit switches prevent over-travel of the robot into the hard stops of each axis of
motion, and are normally activated just prior to contact with the hard stops. The limit
switches signal the Galil board to kill power to the motor and stop the motion. In nor-
mal operation, the robot should not move into the limit switch area. Limit switches
are also used to home the axes.
The limit switches are optical emitter-detector switches. The T and R axes use diode
and transistor-type limit switches. The Z axis uses an amplifier-type sensor with open
collector output and output polarity selection.
If you disconnect a switch from the robot internal interface board switch, input will
read as active.
Limit switch problems can be caused by software, mechanical position setup, or hard-
ware. To determine if limit switch hardware is functional, perform Diagnostic Step 4,
the Limit & Home Test.
If the robot fails because a limit switch was triggered (Bit 5 in the response to the STAT
command), use the
RLS
command to determine which limit switch was activated.
The response to
RLS
has the following bit assignments for 6.0+ firmware and firm-
ware previous to 6.0. Note that bits 3, 7, 11, 15, 19, 23, 27, and 31 vary by the type of
component and number of axes—a three-axis system (3), a four-axis system (4) or a
six- or eight-axis system (8). For a three-axis system, a robot-only system, a 16-bit
word is returned
. For 6.0+ firmware
, the bits for a robot-only system are standard
with the bits listed in this table.
For earlier firmware
, the bits for a robot-only system
are defined in the second table to follow.
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