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This article describes the usage of the filter "HideAtAcceleration" for ignoring intervals of a signal for monitoring, in which an axis is accelerating.

The "HideAtAcceleration" signal filter observes the speed signal of an axis. If the filter detects that there is acceleration, the signal is replaced with a special code which, in

  • tolerance-range-based monitoring (breakage detection, tolerance ranges, generic monitoring)
  • free-form monitoring
  • feed control

causes the signal to be "hidden". Monitoring is therefore stopped briefly after acceleration phases.

Example: Thread cutting

The example below shows the effect of the filter on monitoring during thread cutting:

 

The top and bottom images show the torque curve (red) over a complete thread cutting cycle. In the top image, the hide feature is not used. In the bottom image, acceleration is hidden.

At the beginning (approximately 0.3 s) the spindle is brought to a desired speed. The motor output rises sharply for a short time. After approximately 1.5 s, the tool penetrates the workpiece. Between 1.5 s and 2.5 s, the motor output is therefore slightly increased. At approximately 2.5 s the thread is cut. The tool is now reversed, which causes the motor output to rise again sharply. The tool is then pulled out of the workpiece with reverse rotation.

Only the thread cutting time range, between approximately 1.5 s and 2.5 s, is actually relevant for monitoring the process. The time ranges in which the motor output rises sharply "irritate" the monitoring. The monitoring in the top image assumes that these strong signal peaks are part of the process and sets the limits accordingly high.

The monitoring in the bottom image is significantly more correct. Time ranges in which the tool was accelerated are hidden.

Parameterizing the signal filter

 

Function name

Description

Motor time constant [s]

Estimate of the time constant value, which describes the fade-out speed of the signal peaks to be filtered

Adapt the fading time to a signal height of

Target value, to which the signal heights should fall in accordance with the fade-out constant

Hide using a nominal-actual difference

Hiding is carried out based on a target/actual difference (instead of based on calculated acceleration)

Target/actual difference value [%]

For this option, the desired difference must be entered here. Provided the current difference is higher than the value entered, a time period for which the signal is to remain hidden is calculated based on the fade-out speed of the signal.

Hide using a calculated axis acceleration

Determines hiding based on a calculated acceleration (instead of a fixed difference)

Filter frequency for speed

Filter frequency for the speed signal (only active with hide at acceleration)

Difference between two speed values at which it will be hidden

Desired difference between the speed values for hiding (only active with hide at acceleration). Provided the current difference is higher than the value entered, a time period for which the signal is to remain hidden is calculated based on the fade-out speed of the signal.

Setup aid

Triggers comparison values, extends the log

Minimum time to hide when reaching the target speed after starting up from stop

Determines the minimum hide time

Signal processing

If this has been deactivated, options for signal processing (see Section 11.5.1) are displayed.

Input: Signal

Signal to be hidden

Input: Target speed

Signal for the target speed

Input: Actual speed

Signal for the actual speed

Output: Machine

Name of the signal in the "Machine" column

Output: Axis

Name of the signal in the "Axis" column

Output: Signal

Name of the signal in the "Signal" column

Output: Unit

Unit of the signal

 

The signal filter can detect the acceleration of an axis in two ways:

  • Recognition of axis acceleration based on the speed (target) signal

For this, as shown in the image above, the checkmark next to "Hide using a calculated axis acceleration" must be set. The signal filter now requires two input signals: The torque of an axis and its speed.

The speed signal is smoothed in the first step. The filter frequency for this smoothing can be adjusted. If a certain difference between two measured values occurs after smoothing, the filter assumes that the axis is being accelerated.

  • Recognition of axis acceleration based on the speed target signal and speed actual signal

For this, the checkmark next to "Hide using a nominal/actual difference" must be set. The signal filter now requires three input signals: The torque of an axis, its actual speed and its target speed.           

As soon as the actual speed deviates from the target speed by a configurable percentage value, the filter assumes that the axis is being accelerated.

When the filter detects acceleration, it considers the level of the current torque and sets it in relation to the specified motor time constant. The higher the motor time constant or motor current, the longer the signal is hidden.

The "HideAtAcceleration" signal filter is only visible if the internal "HideAtAccelerationX" setting is set to "true".