sensorless control is often used in cost-critical systems where medium
to ultra-high velocity motor control is needed, e.g., in blower applications.
Typically, sensorless BLDC control does not allow for positioning and is
therefore used for speed control up to very high velocities.
Ensuring smooth, reliable, precise, and responsive control requires
significant expertise and advanced algorithms that can be implemented
in a dedicated chip set or a (32-bit) microcontroller.
Stepper Motors
Stepper motors are known for their ability to provide precise control,
particularly at low speeds. These motors are widely used in applications
requiring accurate positioning, such as semiconductor-handling robots,
3D printers, and surveillance cameras. Unlike traditional brushed DC or
AC motors, stepper motors can operate in an open-loop system, meaning
they do not require position or velocity feedback to maintain control.
Further, their high torque, their ability to maintain position, and their
high position resolution often enable them to work without any gearing.
This architecture makes them cost-effective and easier to integrate into
certain systems.
However, the challenge with stepper motors lies in their torque curve.
While stepper motors deliver high torque at low speeds, their torque
rapidly diminishes as speed increases due to the feedback voltage (EMF).
This feature limits their effectiveness in applications requiring both high
C h a p t e r 1 | M o t o r T y p e s a n d T h e i r C o n t r o l C h a l l e n g e s
Daniel Zaleski
Product Applications Manager,
Analog Devices
For phase or inline motor
control shunt-based current
sensing, you have to be very
robust against the PWM
(pulse width modulation)
stepping of the motor. The
amplifier has to be very
robust to reject the
common-mode step and just
amplify the differential
voltage, which is representative
of the current."
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14 Experts Discuss Motor Control in Modern Applications
