Technical Manual
PD4-N5918
Overview
6 Issue: V 1.4
Closed-Loop current control (sinusoidal commutation via the encoder):
In contrast to conventional stepper motor positioning controls where only the motor is
actuated or the position adjusted via the encoder, sinusoidal commutation controls the
stator magnetic field via the rotary encoder as in a servomotor. The stepper motor acts
in this operating mode as nothing more than a high pole servomotor, i.e. the classic
stepper motor noises and resonances vanish. As the current is controlled, the motor
can no longer lose any steps up to its maximum torque.
If the controller recognizes that the rotor is falling behind the stator field due to
overload, adjustments are made with optimal field angle and increased current. In the
opposite case, i.e. if the rotor is running forward due to the torque, the current is
automatically reduced so that current consumption and heat development in the motor
and controller are much lower compared to normal controlled operation.
With dspDrive®, the motor current is controlled directly by a digital signal processor.
Unlike conventional ICs, which resolve the winding current measurement and the
target current value with only 6 or 8 bit, the new dspDrive®performs the entire control
with a resolution of 12 bit. The parameters of the PI current controller can be adjusted
to the motor and by the user as a function of the rpm.
This has the following application advantages:
•Very smooth, low-resonance operation with a sinusoidal current in the windings,
even at low speeds.
•Very good step angle accuracy and synchronization, even in open-loop operation.
The integrated programming language NanoJ, based on the Java standard, means
complete application programs can be realized on the drivers that can be executed
independently without a higher-order controller.
The programs can be created, compiled directly and written to the controller with the
free NanoJEasy editor.
NanoJ is only supported by the RS485 firmware.
More detailed information can be found in the separate programming manual.
