Stop Mode

LabVIEW 2018 SoftMotion Module

Edition Date: March 2018

Part Number: 371093W-01

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The type of stop to perform. Valid options are Decelerate, Immediate, and Disable Drive.

Note  Stop commands do not affect setpoints written to the axis. To stop the effects of setpoint, write a new setpoint to negate the motion.

Decelerate

Commands the axis or coordinate to immediately start decelerating using the deceleration and deceleration jerk values specified for the move in progress. The final stop position depends on the deceleration values. The axis or coordinate does not reach the target position.

Note  Contour moves do not have move constraints. Using Decelerate stop mode with a Contour Move immediately stops the move. Use Contour Stop method to allow the current points in the buffer or current iteration to finish before the move is stopped.

If an axis that is part of a coordinate is individually Decelerate stopped, the other axes in the coordinate space are also Decelerate stopped.

Immediate

Stops the axis or coordinate by issuing a controlled hard stop. An Immediate stop has the following behavior depending on the state of the axis:

  • If the axis is not moving and not energized, the axis is energized.
  • If the axis is not moving and energized, calling an immediate stop has no effect.
  • If the axis is moving:
    • On servo axes, full torque is applied in the opposite direction to stop the motor(s) as soon as the command is received.
    • On stepper axes, the step pulses are ceased as quickly as possible. However, it is possible that there may be a small amount of position error after halting the move.

In both cases, the motor(s) attempt to stop with a near infinite rate of deceleration. There is no trajectory profile and motion is not controlled by previously loaded deceleration and deceleration jerk parameters.

NoteNote  For stepper axes configured for p-command mode, ensure that the axis is not moving before halting an axis that was previously killed to avoid position error between NI SoftMotion and the drive. In this case, a call to Immediate stop while the axis is moving resets your reference position to an undefined location, and you should perform a Find Home reference move before executing another move.

If an axis that is part of a coordinate is individually Immediate stopped, the other axes in the coordinate space are Decelerate stopped.

Disable Drive

Stops the axis or coordinate by disabling the drive and switching all outputs to their user-specified safe states, if the hardware supports safe states. On servo axes, a disable drive stop disables the control loop and zeros the output DAC, allowing frictional forces alone to stop the motion. On stepper axes, a disable drive stop ceases the stepper pulse generation as soon as SoftMotion receives the command. On both axis types, there is no trajectory profile during a disable drive stop. If enabled, the Drive Enable output is deactivated to disable the servo or stepper drive. You can enable and configure the Drive Enable output from the Drive Enable page of the Axis Configuration dialog box.

Note  This method does not disable the specified axis. This means that any enabled position compare, position capture, or other operations are not disabled. If you want to ensure that any enabled operations do not execute after reenabling the drive, you must disable the axis using the Power function.
CautionCaution  When the drive is disabled, the motor is allowed to freewheel, and will move if external forces are acting on it. If the axis moves into an enabled limit switch, the axis stops using the Stop Mode specified in the Axis Configuration dialog box. If you do not wish for the axis to become energized under any circumstances, you must disable the axis after disabling the drive using Power or use a motor with a brake fitted.

If an axis that is part of a coordinate is individually Disable Drive stopped, the other axes in the coordinate space are Decelerate stopped. If a slave axis is deactivated, master-slave gearing or camming is automatically disabled.

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