JVL MIS17 Series, User Manual

Page: 98 / 367

98 JVL Industri Elektronik A/S - User Manual - Integrated Stepper Motors MIS17x, 23x, 34x, 43x
5.3 Closed loop operation
5.3.1 Introduction to closed loop operation.
When running a stepper motor under normal operating conditions the load torque will
cause a small displacement of the rotor from its nominal position, but normally such dis-
placements do not lead to a loss of synchronization.
However, synchronization will be lost if the load exceeds the available motor torque.
This can cause the motor to stall with a position loss which must be corrected afterwards
– for example with the Auto correction function (see also Auto Correction , page 94) or by
monitoring the position externally with an encoder.
The MISxxH2xx (only available from serial numbers 173000) and MISxxH4xx have the
ability to run in closed loop and therefore always tracks the rotor displacement in real
time. The control algorithm aligns the commutation angle and motor current when need-
ed. This avoids that the motor is stalling and runs the motor at a lower current when pos-
sible with the advantage that the overall system efficiency is much better.
The closed loop offers 2 ways of operation
1. Closed loop with constant current. The current is maximum all the time regardless
which load is applied to the motor.
2. Closed loop with dynamic current control. The current is adjusted real time to match
the actual load. The advantage is that the motor runs more efficient (less heat) and
the audible noise when running is much less.
Note: When "closed loop" is enabled, then the InPosition flag changes its behaviour so
that it will act as the "InTargetPosition" bit, which means that it will tell if the en-
coder position and P_SOLL are within the "in position window".
Only MISxxx--- H2/H4 ---