Drive and voltage output

WARNING

Unpredictable behavior of the axis under special circumstances

Inform yourself about the behavior of the drive in case of overload. There are drives that automatically shut down when overloaded, so that the axle could then be force-free, full of energy and no longer braking.

Determination and setting the most important drive parameters: drive polarity, reference output, reference velocity, drift compensation.

Interface

The drive parameters are accessed via the System Manager.

The drive parameter: determination of the direction

  1. Use the encoder! Restrict the distance of travel using the software limit position min / max on the global tab for the axis.
  2. On the drive's global tab, adjust the output limit to +1.0 or -1.0.
  3. On the controller's global tab, set a value of 1.0 for the feed forward weighting.
  4. If the controller has a PID tab, set the position control factor Kv (and all other control factors) to zero. Deactivate the automatic offset adjustment.
  5. If the drive has an analog tab, set the reference speed in accordance with the information provided by the machine manufacturer to something in the region of the correct value, and set the reference output to 1.0. Set the drift compensation to zero.
  6. On the global tab for the axis, set the same value for the maximum permitted speed as for the drive's reference speed. Set one tenth of this value under manual speed max and manual speed min.
  7. If the controller has a PID tab, set the position control factor Kv (and all other control factors) to zero. Deactivate the automatic offset adjustment.
  8. Now use the <F2> and <F3> keys in the online image of the axis to move in the "smaller" and "larger" directions, and observe the machine. If, when the <F2> key is pressed the machine moves in the "larger" direction, and when the <F3> key is pressed it moves in the "smaller" direction, alter the motor polarity on the drive's global tab, and repeat this step.

The drive parameter: feed forward

This section is only necessary if the drive has an analog tab.

  1. On the controller's global tab, set a value of 1.0 for the feed forward weighting.
  2. On the drive's global tab, adjust the output limit to +1.0 or -1.0.
  3. On the controller's PID tab, set the position control factor Kv to a low value. When correctly set, it will be easy to detect the following error during the test transits that are to be made out, but it will be constant. Example: 1 (mm/sec)/mm or 60 (mm/min)/mm.
  4. On the drive's analog tab, set the reference speed to an approximately correct value in accordance with the information provided by the machine manufacturer. Set the drift compensation to zero. In accordance with the information provided by the machine manufacturer, set the reference output to 1.0 if this refers to 100% (or 10 Volts). If the figure provided is, for example, for 90% (or 9 Volts), 0.9 should correspondingly be set.
  5. On the global tab for the axis, set the maximum permitted speed to about 90% of the drive's reference speed. Set one tenth of this value under manual speed max and manual speed min.
  6. On the dynamic tab of the axis set a provisional value of about 200 mm/s² for the acceleration and deceleration and a jerk of 500 mm/s³. If these values do not allow the constant speed to be reached within the space available, increase the values while retaining the relationship.
  7. Now use the <F2> and <F3> keys in the online image of the axis to start in the "smaller" and "larger" directions, and observe the arithmetic sign of the total output and the controller output.
  8. If the two values have the same sign, the axis is reacting with a lower speed than that expected by the feed forward. In this case, the reference speed should be reduced. If the arithmetic signs are opposed, the axis is moving faster than expected by the feed forward. In that case, the reference speed should be increased.
  9. If the controller output is significantly less than 10% of the total output, the maximum manual speed can be increased in steps up to about 50% of the maximum speed. The test movements should be continued using the <F1> and <F4> keys.
  10. If the feed forward is well adjusted, the controller output should represent less than 1% of the total output. Poor mechanical conditions, however, often do not permit such accurate adjustment.

Drive parameter: Drift compensation

This adjustment is only possible if the drive has an analog tab.

If the set values are provided in analog form, there can often be a voltage difference between the controller and the power section. This can be the result of a real voltage drop. However the cause is nearly always that the zero adjustment of the two sides is not the same. In this case, when the position control is switched off, the axis will slowly leave its position: it drifts. Active position control will stop it not far from the set position. Nevertheless there is then a certain amount of following error.

It is possible in this case to compensate for the offset by means of a constant speed offset. However the DAC resolution of a few mV has a negative effect here.

As an alternative, some controllers offer a facility for automatic offset correction.

The drive parameter: output limiting

It is necessary in some cases to limit the control level output given with a drive to the power section. You will find appropriate input facilities on the drive's global tab. You should, however, only make these adjustments at the end of the axis commissioning. Until that time, the values of –1.0 and +1.0 should be entered for the minimum and maximum limits. Otherwise, the measurements described here will be affected.