Galil Motion Control DMC-42 0 Series, Руководство пользователя

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The units of the error limit are quadrature counts. The error is the difference between the command position and
actual encoder position. If the absolute value of the error exceeds the value specified by ER, the controller will
generate several signals to warn the host system of the error condition. These signals include:
Signal or Function State if Error Occurs
# POSERR Jumps to automatic excess position error subroutine
Error Light Turns on
OE Function Shuts motor off if OE1 or OE3
AEN Output Line Switches to Motor Off state
The Jump on Condition statement is useful for branching on a given error within a program. The position error of
X,Y,Z and W can be monitored during execution using the TE command.
Encoder Failure detection
The encoder failure detection on the controller operates based upon two factors that are user settable, a threshold
of motor command output (OV), a time above that threshold (OT) in which there is no more than 4 counts of
change on the encoder input for that axis. The encoder failure detection is activated with the OA command. When
an encoder failure is detected and OA is set to 1 for that axis, the same conditions will occur as a position error.
Conditions for proper operation of Encoder Failure detection
•
The axis must have a non-zero KI setting order to detect an encoder failure when the axis is not profiling.
•
The IL command must be set to a value greater than the OV setting
•
The TL command must be set to a value greater than the OV setting
Example:
The A axis is setup with the following settings for encoder failure detection:
OA 1
OT 500
OV 3
OE 1
ER 1000
The A axis is commanded to move 300 counts, but the B channel on the encoder has failed and no longer operates.
Because the ER setting is greater than the commanded move, the error will not be detected by using the OE and ER
commands, but this condition will be detected as a encoder failure. When the axis is commanded to move a 300
counts, the position error will cause the motor command voltage to be increased to a value that will be greater
than the OV value, 3 volts in this case. Once the motor command output is greater than the OV threshold for more
than than the 500ms defined by the OT command AND there has been less than 4 counts of change on the
encoder, then the controller will turn off that axis due to an encoder failure. The motor will have moved some
distance during this operation, but it will be shut down before a full runaway condition occurs.
Using Encoder Failure to detect a hard stop or stalled motor
The encoder failure detection can also be used to detect when an axis is up against a hard stop. In this scenario the
motor command will be commanded above the OV threshold, but because the motor is not moving the controller will
detect this scenario as an encoder failure.
Programmable Position Limits
The DMC-42x0 provides programmable forward and reverse position limits. These are set by the BL and FL
software commands. Once a position limit is specified, the DMC-42x0 will not accept position commands beyond
the limit. Motion beyond the limit is also prevented.
Chapter 8 Hardware & Software Protection ▫ 149 DMC-42x0 User Manual