Every motor requires some
sort of current sensing if you
want to control it efficiently.
Position sensing can add
precision, but it's often a
balance between cost and
necessity, depending on
the application."
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
industrial robots. However, BLDC motors are more
complex to control than their brushed counterparts.
Control of a BLDC motor typically involves electronic
commutation, in which the motor's windings are
switched in a specific sequence based on the rotor's
position. The most prevalent types of control are
block commutation and FOC/vector control.
Sensor-based control is essential for precise and
reliable torque, velocity, and position control. There
is a variety of position sensors (encoders) that can
be used depending on the application requirements.
The resolution of the encoder, the quality of the
current measurement, and the implementation of the
controller structure define the quality of the motor
control. A sensor-based system is mandatory for
position control systems as it is in robotics.
Sensorless control is particularly challenging at
low speeds, at which the back EMF is too weak to
provide accurate feedback. This shortcoming makes
low-speed control difficult in sensorless systems,
especially in high-torque applications. For
example, in industrial robots or drones,
BLDC motors must operate across
various speeds and torques. Therefore,
Derrick Hartmann
Senior Manager, System Architecture,
Analog Devices
9
14 Experts Discuss Motor Control in Modern Applications
