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Basic functions 6.14 Position tracking

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Figure 6-11 Measuring gearbox

In order to determine the position at the motor/load, in addition to the position actual value of the absolute encoder, it is also necessary to have the number of overflows of the absolute encoder.

If the power supply of the control module must be powered-down, then the number of overflows must be saved in a non-volatile memory so that after powering-up the position of the load can be uniquely and clearly determined.

Example: Gear ratio 1:3 (motor revolutions p0433 to encoder revolutions p0432), absolute encoder can count 8 encoder revolutions (p0421 = 8).

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Figure 6-12 Drive with odd-numbered gears without position tracking

In this case, for each encoder overflow, there is a load-side offset of 1/3 of a load revolution, after 3 encoder overflows, the motor and load zero position coincide again. The position of the load can no longer be clearly reproduced after one encoder overflow.

If position tracking is activated via p0411.0 = 1, the gear ratio (p0433/p0432) is calculated with the encoder position actual value (r0483).

Drive Functions	209
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4