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6.5. Speed
PROFIdrive telegrams 82 and 83 as well as manufacturer-specific telegrams 100 and 860 provide the speed
value and the absolute position value.
It is possible to use a filter (calculation of average value) for the calculation of the speed value. For the
configuration of the filter both parameters “Speed Update Period” and “Speed Filter Depth” are used. In
chapters
“6.5.2 Speed Update Period” and “6.5.3 Speed Filter Depth” details can be found.
When a gear factor is used the following has to be considered for the calculation of the speed value:
- The gear factor is not taken into account in the speed value.
- The speed value refers to the drive side.
6.5.1. Speed Measuring Unit
The measuring unit for the speed value is defined by
parameter “Velocity Measuring Unit” of the encoder
parameters.
The following scaling options are possible:
rpm
revolutions per minute
steps/10ms
number of steps (in the configured singleturn resolution) per 10 ms
steps/100ms
number of steps (in the configured singleturn resolution) per 100 ms
steps/1000ms
number of steps (in the configured singleturn resolution) per second
For each scaling option the measured value is provided as a
„signed integer“. Positive values indicate the
direction of rotation with rising position values. Which rotational direction is assigned
“positive” depends on
the CW/CCW parameter setting.
6.5.2. Speed Update Period
The time window for the update of the speed value is defined by
parameter “Velocity Update Period [ms]” of
the encoder parameters.
A short speed update period entails a more dynamic speed output, whereas an extended update period
ensures more stable values. The optimum speed update period depends on the requirements of the
application.
The update period can be configured within a range from 1 ms to 255 ms.
The update time of the speed value shall be an integer multiple of the PROFINET bus cycle time.
Additionally it must be pointed out that the update time of the speed value shall not be smaller than the
PROFINET bus cycle time. An update time of the speed value of for example 1 ms at a PROFINET bus cycle
time of 2 ms would not be accepted.
6.5.3. Speed Filter Depth
The filter depth is defined by
parameter “Velocity Filter Depth (Update Periods)” of the encoder parameters.
A shallow filter depth entails a more dynamic speed output, whereas a higher filter depth ensures more
stable values. The optimum speed filter depth in interaction with the configured speed update time depends
on the requirements of the application.
The filter depth is configurable within the range from 1 to 255.
