Velocity feedforward control

Configuration

To apply speed feedforward control, first configure speed feedforward control in P-AXIS-00223 and the output of the speed feedforward control value as an additive command value:

vorsteuer.vorsteuerung   0x101  #0x001: Activation velocity                                 feedforward
                                #0x100: Output as additive                                 velocity command value

Configure the additive speed command value in the cyclic process data.

Notice

notice

If the output of speed feedforward control is activated as an additive speed command value and no additive speed command value is configured in the cyclical process data, an error message P-ERR-70350 is output.

Speed scaling

Now only speed scaling needs to be parameterised. The parameters P-AXIS-00205, P-AXIS-00206 and P-AXIS-00207 are used for this.

In the parameter P-AXIS-00205 enter the speed which is set for the axis taking into consideration all the transmission elements (e.g. gear ratio and spindle pitch) if a value of P-AXIS-00206 is output to the speed interface.

Enter the time base used at the speed interface in the parameter P-AXIS-00207.

Example

example

Velocity feedforward control

A SERCOS drive which has a spindle pitch of 10 mm/rev and a default scaling for speed data (10-4 rpm), results in a translatory axis speed of 10 mm/min (10,000 * 10-4 rpm * 10 mm/rev) when the value 10,000 is output as the speed command value at the drive.

Therefore set the following values for the parameters P-AXIS-00205, P-AXIS-00206 and P-AXIS-00207:

antr.v_time_base         0      #Timebase per Minute
antr.v_reso_num      10000      #Outputvalue to drive
antr.v_reso_denom    10000      #Resulting axis velocity in                                  um/v_time_base

If in addition a gear with a gear ratio of i=3 (nMotor/nLast) is considered, the translatory speed of the axis is reduced to 3.333 mm/min (10,000 * 10-4 rpm / i * 10 mm/rev) for the same output value. This results in the following values for P-AXIS-00206 and P-AXIS-00207:

antr.v_time_base         0      #Timebase per Minute
antr.v_reso_num      10000      #Outputvalue to drive
antr.v_reso_denom     3333      #Resulting axis velocity in                                 um/v_time_base

In addition the output of the speed feedforward control value can be delayed in relation to the set position. This delay can be set by the parameter P-AXIS-00389.

Notice

notice

The maximum delay time that can be set is one position controller cycle. If a longer delay time is parameterised, the error message P-ERR-70349 is output and the delay time is set to 0.

The resulting parameter set is:

vorsteuer.vorsteuerung   0x101  #0x001: Activation velocity                                 feedforward
                                #0x100: Output as additive                                 velocity command value
vorsteuer.velocity_delay_time   150   # Delay velocity
                                      feedforward against
                                      position
                                      # command value in us
antr.v_time_base         0      #Timebase per Minute
antr.v_reso_num      10000      #Outputvalue to drive
antr.v_reso_denom     3333      #Resulting axis velocity in                                 um/v_time_base