Example Code
Products and Environment
This section reflects the products and operating system used to create the example.To download NI software, including the products shown below, visit ni.com/downloads.
- Brushless Servo Motor
Hardware
Code and Documents
Attachment
Description
This piece of code represents the simplest method for controlling a brushless DC (BLDC) motor, 6-phase (also called trapezoidal) control. The algorithm uses feedback from hall sensors to dictate which FETs or IGBTs should be energized in the motor control bridge. The following diagram shows the hardware setup that accompanies this code.
The Compact RIO system reads the hall sensors from phases A, B and C and actuates a single high-side FET and a single low-side FET to make the motor spin either clockwise or counter-clockwise. Actuating the 7th FET with a PWM signal provides speed control by setting an effective bus level voltage. The code generates a 9-bit PWM signal (a magnitude of 0-511), resulting in a carrier frequency of just over 78kHz.
The following pictures show the code itself. The top loop in the code generates the FET signals based on the hall sensor input and the commanded bus voltage. The bottom loop generates the PWM for the bus-level FET.
The following picture show the hardware used to test this control algorithm (a custom-made motor drive bridge and a Maxon brushless DC motor).
More compliated control algorithms can be found at the following links:
sinusoidal control - https://forums.ni.com/t5/Example-Code/Look-up-Table-for-Sinusoidal-V-f-Control-of-a-Brushless-DC-Mot...
field-oriented control - https://forums.ni.com/t5/Example-Code/Field-Oriented-Controller-FOC-Space-Vector-Controller-for-a/ta...
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.
