JVL MIS17 Series, User Manual

Page: 107 / 367

JVL Industri Elektronik A/S - User Manual - Integrated Stepper Motors MIS17x, 23x, 34x, 43x 107
5.3 Closed loop operation
The relationship between the current control rate and velocity is illustrated on the figure.
The decrement rate is inverse proportional to the velocity because the motor is much
more sensitive to variations in the running current at high speeds. It gives a more stable
motor behaviour if the current is decreased slower at high speeds.
The increase rate must always be fast enough to detect the worst case where the motor
is blocked at 3000 RPM.
The start value and the slope can be modified with the registers CUR_SCALE_INC,
CUR_SCALE_DEC and CUR_SCALE_FACTOR.
The default values are already optimised to give the best overall performance on all ve-
locities, some other values could be better for at specific velocity.
How to calculate how the registers affect the timing at a specific velocity (RPM):
The increment timing is independent of velocity:
Timing for the default factory settings:
The current is regulated in 2048 steps from 0-100 %.
This means that it will take T
INC
* 2048 =113 ms for the current to increase from 0 to
100 % - at all velocities.
It will take T
DEC_0
* 2048 = 227 ms for the current to decrease from 100 % to 0 % at
0 RPM and T
DEC_3000
* 2048 = 2,3 s at 3000 RPM.
Only MISxxx--- H2/H4 ---