Friction Compensation (Quadrant Error Compensation); General Function Description; Supplementary Conditions; Friction Compensation With A Constant Compensation Value - Siemens SINUMERIK 808D Function Manual

Parameters
In order to achieve a correctly set speed feedforward control, the equivalent time constant of the speed control loop must be
determined exactly and entered as machine data MD32810 EQUIV_SPEEDCTRL_TIME (equivalent time constant of the
closed speed control loop) during commissioning.
11.5

Friction compensation (quadrant error compensation)

11.5.1

General function description

In addition to the mass inertia and the machining forces, the frictional forces in the gearing and guideways of the machine
influence the behavior of a machine axis. During the acceleration of an axis from standstill, especially the transition from
static friction to the significantly smaller sliding friction has a negative affect with regard to the contour accuracy.
The sudden change in the friction force results in a briefly increased following error. With interpolating axes (path axes), this
results in significant contour violations. For circles, the contour violations occur especially at the quadrant transitions due to
the standstill of one of the involved axis at the direction reversal.
Therefore, an additional setpoint pulse is injected as a compensation value for this friction or quadrant error compensation
when the axis accelerates from standstill, i.e. at the transition from static to sliding friction. In this way, contour violations can
be almost completely avoided at the quadrant transitions of circular contours.
Acceleration-dependent friction compensation
In most cases, a compensation value independent of the axial acceleration with constant amplitude is sufficient for the
quadrant error compensation. However, if the compensation value is dependent on the acceleration, an adaptation
characteristic can be activated via the "friction compensation with adaptation" in order to model this behavior.
Circularity test
The easiest way to commission the friction compensation is with the circularity test. A circle is traversed and the circular
contour generated on the machine based on the actual position values of the involved machine axes and the deviations to
the programmed ideal circular contour, especially at the quadrant transitions, displayed in graphical form.
11.5.2

Supplementary conditions

Note
Switch off setpoint-related compensations
The following compensations affect the position setpoint and must be switched off before the measurement of the axes
involved in the circularity test:
Direction-dependent leadscrew error compensation:
MD32710 $MA_CEC_ENABLE[ <axis> ] = 0
11.5.3

Friction compensation with a constant compensation value

11.5.3.1

Function activation

Enable
The general enabling of the friction compensation is via:
MD32490 $MA_FRICT_COMP_MODE[ <axis> ] = 1
Activation
The activation of the friction compensation with constant compensation value is via:
● MD32500 FRICT_COMP_ENABLE[ <axis> ] = 1 (friction compensation ON)
● MD32510 $MA_FRICT_COMP_ADAPT_ENABLE[ <axis> ] = 0 (adaptation OFF)
Parameters
The following parameters are calculated for friction compensation with constant compensation value:
● MD32520 $MA_FRICT_COMP_CONST_MAX (maximum compensation value)
For friction compensation with constant compensation value, the parameterized value is injected as compensation value.
● MD32540 $MA_FRICT_COMP_TIME (friction compensation time constant)
The compensation value is injected via a DT1 filter. The compensation value decays according to the parameterized time
constants.
Function Manual
01/2017
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