ABB ACS 800 Series, Firmware Manual

Page: 91 / 340

Program features
91
Actual position configuration based on a motor encoder signal
Position
The Position function calculates the actual position of the hook. The Shaft synchro
function uses the hook position when synchronising the Master and Follower drives.
In addition, the position is used in anti-sway controlled trolley drives and long travel
drives. The position is based on the encoder on the motor shaft. To enable the
position calculation, you must define the factor that scales the encoder pulse to
actual position units. See the following example.
The actual position value 02.21 POS ACT PPU is saved in the memory after the
power is switched off/on in the RMIO board.
Example
If the hoist drive operates at 40 000 mm/min corresponding to the motor speed of
1500 rpm, and the encoder parameter
50.01 PULSE NR ppr is set to 2048,
parameter 78.04 POS SCALE value equals to ((1500*2048) / 40 000) = 76.8 pulses/
mm. The POS SCALE in pulses/mm can be calculated by multiplying the motor
speed with the PPR and then dividing with the corresponding linear speed. The
linear speed can be calculated using the equation shown in section
Calculating the
linear rope speed on page 103 . If the motor speed is 500 rpm, which corresponds to
linear speed of 13333.33 mm/min, then the POS SCALE would be ((500 * 2048) /
13333.33) = 76.8 pulses/mm. The Shaft synchro function uses the actual position in
the Master and Follower drives. That is why you should use the same measurement
unit for the scaling factor in both drives, that is, mm.
If the parameters (gearbox ratio, diameter) used for calculating the linear speed are
not available, the position scale can be calculated by the following procedure.
1. Set the encoder PPR in parameter 50.01 PULSE NR.
2. Monitor the shaft position signal 02.22 SHAFT POS, mark the rope with a marker
and note the shaft position signal 02.22 SHAFT POS.
3. Start the drive and stop it after a few mm travel of the rope.
4. Check the shaft position signal 02.22 and the corresponding travel in mm.
Suppose the initial value in shaft position 02.22 was zero, after stopping it shows
2000, and this motion has resulted in the rope travel of 20 mm, then the position
scale would be (2000 / 20) = 100 P/mm.
Note : The value range of actual position 02.21 POS ACT PPU is -8388608 to
+8388608, but when the value is used in the fieldbus for data transfer, it is truncated
to -32767 to +32767.