Friction Compensation (Quadrant Error Compensation); General Information - Siemens SINUMERIK 840D sl Function Manual

Compensations (K3)

5.6 Friction compensation (quadrant error compensation)

5.6 Friction compensation (quadrant error compensation)
5.6.1

General information

Function
Friction occurs predominantly in the gearing and guideways. Static friction is especially
noticeable in the machine axes. Because it takes a greater force to initiate a movement
(breakaway) than to continue it, a greater following error occurs at the beginning of a
movement.
The same phenomenon occurs on a change of direction where static friction causes a jump
in frictional force. If, for example, one axis is accelerated from a negative to a positive
velocity, it sticks for a short time as the velocity passes through zero because of the
changing friction conditions. With interpolating axes, changing friction conditions can cause
contour errors.
Quadrant errors
This behavior is particularly apparent on circular contours on which one axis is moving at
maximum path velocity and the other is stationary at quadrant transitions. With the aid of
friction compensation these so-called "quadrant errors" can be almost completely eliminated.
General procedure
Measurements on machines have shown that contour errors caused by static friction can be
effectively compensated by the injection of an additional setpoint pulse with the correct sign
and amplitude.
Methods of friction compensation
One of two friction compensation methods can be selected on the SINUMERIK 840D
(MD32490 $MA_FRICT_COMP_MODE (friction compensation method)):
● Conventional friction compensation
With this type, the intensity of the compensation pulse can be set according to the
characteristic as a function of the acceleration. This characteristic must be determined and
parameterized during commissioning using the circularity test. The procedure for this is
relatively complicated and requires some experience.
● Quadrant error compensation with neural networks
To simplify commissioning, the compensation characteristic no longer has to be set manually
by the commissioning engineer but is determined automatically during a training phase and
then stored in the non-volatile user memory.
394
(MD32490 = 1)
(option for SINUMERIK 840D)
(MD32490 = 2)
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions