Technical manual
SMCI35
Overview
1 Overview
Introduction
The stepper motor control SMCI35 is an extremely compact and cost-effective
constant current power output stage with integrated Closed-Loop current control.
Due to the great capacity and functions available, it offers designers and developers a
rapid and simple method of resolving numerous drive requirements with less
programming effort.
It is used for controlling standard stepper motors (including with attached encoders) or
motors with integrated encoders or brakes.
SMCI35 functions
The stepper motor control SMCI35 contains the following functions:
•Microstep 1/1 – 1/64 Final output stage (0.014° step resolution)
•Closed-Loop current control (sinusoidal commutation via the encoder)
•Powerful DSP microprocessor for flexible I/O
•Sequence programs with NanoJ
•Rotation monitoring for optional encoder
•Easy programming with the NanoPro Windows software
Closed-Loop current control (sinusoidal commutation via the encoder):
In contrast to conventional stepper motor controls where only the motor is actuated or
the position adjusted via the encoder, sinusoidal commutation controls the stator
magnetic field as in a servomotor via the rotary encoder. 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.
•Very good step angle accuracy and synchronization, even in open-loop operation.
•Three-phase stepper motors and BLDC motors can be controlled as well.
Issue: V 1.1 - 05.03.2010 5
