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Friction torque compensation

Compensation of friction components dependent on reference speed

It is advisable to compensate for higher friction torques, in order to minimize tracking error when reversing the speed of the axle. The drive controller enables compensation of friction components dependent on the reference speed "nref_FF". The speed controller can compensate for viscous friction components because of their lower change dynamism. The compensation can be effected step-by-step as a percentage of the rated motor torque by means of P 0386 CON_SCON_TFric. Below P 0387 CON_SCON_TFricZeroSpeed the compensation is reduced by way of an internal ramp.

Bild: Friction curve with high static friction

Parameters for representation of the curve:

No.	P. no.	rpm
	P 0387 CON_SCON_TFricSpeed (0)	5 rpm
	P 0387 CON_SCON_TFricSpeed (1)	35 rpm
	P 0387 CON_SCON_TFricSpeed (2)	200 rpm
	P 0386 CON_SCON_TFric (0)	20%
	P 0386 CON_SCON_TFric (1)	-10%
	P 0386 CON_SCON_TFric (2)	15%

Tabelle: Parameters for representation of the curve

Vorgehensweise: Friction torque compensation

• Execute a fast movement
• Friction torque compensation via P 0386(0), (1), (2) "Friction torque compensation, scaled to the motor rated torque"
• Standstill window via P 0387(0), (1), (2) "Friction torque compensation, speed limitation"
• Observe tracking error
  
  

Scope setting:

• Pre-control:
  Reference torque with pre-control mref_FF
  Actual torque mact or
  Reference current isqref_FF
  Actual current isq

• Tracking error
  MPRO_FG_UsrPosDiff