Velocity feedforward control

Configuration

In order to apply velocity feedforward control, first configure velocity feedforward control in P-AXIS-00223 and the output of the velocity 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 velocity command value in the cyclic process data.

Notice

notice

If the output of velocity feedforward control is activated as an additive command value and no additive velocity command value is configured in the cyclic process data, the error message ID 70350 is output.

Velocity scaling

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

The velocity that is set for the axis and includes all the transfer elements (e.g. gear ratio and spindle pitch) is entered in the parameter P-AXIS-00205 if a value of P-AXIS-00206 is output to the speed interface.

The timebase used at the velocity interface is entered 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      #Output value to drive
antr.v_reso_denom    10000      #Resulting axis velocity in                                  um/v_time_base

If a gear with a gear ratio of i=3 (nMotor/nLoad) is also included, 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 position command value. 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 ID 70349 is output and the delay time is set to 0.

The resulting parameter set is therefore:

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

In addition, configure the additive velocity command value in the cyclic process data of the drive.

antr.sercos.at[0].ident_nr           37

antr.sercos.mdt[0].ident_len   4

antr.sercos.mdt[0].nc_ref      S_0_0037