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National Instruments Corporation
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Sinusoidal Commutation for
Brushless Servo Motion Control
Sinusoidal commutation allows you to use less expensive servo motor
drives with NI motion controllers that support this feature.
Phase Initialization
When the system is first powered on, the controller must determine the
initial commutation phase. NI motion controllers support several methods
of phase initialization, including Hall effect sensors, shake and wake, and
direct set.
Hall Effect Sensors
The controller can use Hall effect sensors to estimate the commutation
phase based on the state of the sensors. After a Hall effect state transition
occurs, the controller recalculates the phase angle based on the transition
location. To obtain maximum torque at the beginning of the move, perform
a move that is 1/6th of the magnetic cycle after system initialization. Refer
to the hardware documentation for Hall effect sensor types and connection
schemes.
Shake and Wake
“Shake and wake” is an initialization method where the motion controller
outputs a specified voltage for a specified duration. This drives the system
to the zero-degree phase position and allows you to establish the position
as a baseline for all other phase positions.
During this process, the motor moves to the zero-degree position with high
torque. Ensure the system is away from any limits before performing shake
and wake initialization.
If the system has load or is moving against gravity, increase the shake and
wake voltage. If there is significant jitter as the axis approaches zero,
increase the duration.
