Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Making your Application Safe
209
Variable Ixx25 for the motor must contain the address of the flag register for the channel into which these
limit switches are wired. Bit 17 of Ixx24 must be set to the default value of 0 to use these limit inputs. If
this bit is set to 1, Turbo PMAC will not monitor these limit inputs. This bit can be set permanently to 1
if the motor does not have limit switches; it can be set to 1 temporarily for operations such as homing into
a limit.
limit switches are wired. Bit 17 of Ixx24 must be set to the default value of 0 to use these limit inputs. If
this bit is set to 1, Turbo PMAC will not monitor these limit inputs. This bit can be set permanently to 1
if the motor does not have limit switches; it can be set to 1 temporarily for operations such as homing into
a limit.
On hitting a limit, Turbo PMAC decelerates the offending motor at a user-programmed rate as defined by
the motor’s Ixx15. If the motor is in a coordinate system that is running a motion program at the time, all
motors in the coordinate system are decelerated to a stop at their own Ixx15 rate. The effect is equivalent
to issuing an A (abort) command. If the coordinate system has been executing a path move, this
deceleration will not necessarily be along that path.
the motor’s Ixx15. If the motor is in a coordinate system that is running a motion program at the time, all
motors in the coordinate system are decelerated to a stop at their own Ixx15 rate. The effect is equivalent
to issuing an A (abort) command. If the coordinate system has been executing a path move, this
deceleration will not necessarily be along that path.
Note:
Turbo PMAC brings the commanded trajectory for the motor to a stop at the Ixx15
rate as soon as it detects a limit condition. If there is significant following error at
the time, the actual position can try to catch up to the commanded position for a
long period of time. With a large enough following error, it is possible that the
commanded position would be well past the limit and into the hard stop. It is
important to set a reasonable fatal following error limit and to allow sufficient
room past the limit switch to absorb errors up to that following error limit.
rate as soon as it detects a limit condition. If there is significant following error at
the time, the actual position can try to catch up to the commanded position for a
long period of time. With a large enough following error, it is possible that the
commanded position would be well past the limit and into the hard stop. It is
important to set a reasonable fatal following error limit and to allow sufficient
room past the limit switch to absorb errors up to that following error limit.
The limit input pins are direction sensitive: the positive-end limit pin stops positive direction moves only
(those coming at it from the negative side), and the negative-end limit pin stops negative direction moves
only (those coming at it from the positive side). This makes it possible to command a move out of the
limit that you have run into. However, this also makes it essential to have your limit switches wired into
the proper inputs, or they will be useless.
(those coming at it from the negative side), and the negative-end limit pin stops negative direction moves
only (those coming at it from the positive side). This makes it possible to command a move out of the
limit that you have run into. However, this also makes it essential to have your limit switches wired into
the proper inputs, or they will be useless.
Software Overtravel Limit Variables
Turbo PMAC also has positive and negative software limits for each motor to complement or replace the
hardware limits. These limits can use the motor’s desired as well as actual positions. Motor variables
Ixx13 and Ixx14 define the positive and negative actual position limits, respectively, in counts, for Motor
xx. These limits are referenced to the motor’s zero (home) position, and do not change if the
programming origin for the associated axis is offset.
hardware limits. These limits can use the motor’s desired as well as actual positions. Motor variables
Ixx13 and Ixx14 define the positive and negative actual position limits, respectively, in counts, for Motor
xx. These limits are referenced to the motor’s zero (home) position, and do not change if the
programming origin for the associated axis is offset.
Turbo PMAC continually compares the motor’s actual position to these limits. The behavior on
exceeding one of these limits is the same as hitting a hardware limit. A value of zero in one of these
parameters disables that software limit.
exceeding one of these limits is the same as hitting a hardware limit. A value of zero in one of these
parameters disables that software limit.
If bit 15 of Ixx24 for the motor is set to 1, Turbo PMAC will compare the motor’s desired position also,
calculated ahead of time for programmed moves, to the software limits. This permits the motor to come
to a full stop within the limits, not just begin to decelerate at the limits. This in turn can provide an extra
useful range of motion at the perimeter of a machine.
calculated ahead of time for programmed moves, to the software limits. This permits the motor to come
to a full stop within the limits, not just begin to decelerate at the limits. This in turn can provide an extra
useful range of motion at the perimeter of a machine.
Note:
Turbo PMAC cannot pre-calculate the desired position for indefinite jog moves J+
and J-, and so will not begin to decelerate on these moves until the present desired
position exceeds a software limit. If it is desired that jog moves stop within the
limits, a J+ command should be replaced by a definite jog to the positive limit; a
J- command should be replaced by a definite jog to the negative limit.
and J-, and so will not begin to decelerate on these moves until the present desired
position exceeds a software limit. If it is desired that jog moves stop within the
limits, a J+ command should be replaced by a definite jog to the positive limit; a
J- command should be replaced by a definite jog to the negative limit.