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Writer's pictureRotem Segev

Medical grade BLDC motor controller and driver

Updated: May 9, 2023

This board encompasses a BLDC driver from STMicroelectronics (52V, 1.4 A RMS), Cortex M4 CPU and capability for Hall Sensor and incremental encoder commutation and feedback. The board's logic and communications interface (RS485) is fully isolated to allow seamless and noise free installations in sensitive, demanding environments. The board is featured in a very well known Medical company's main machines.


Features

BLDC motor driver and controller

Compact size (30X70 mm)

Field Oriented Control (FOC)

Simple and easy to use user interface to control the motor

Position and speed control with current limit

8V to 52V Operating Supply Voltage

1.4A Output Current/3A Peak Current

Writing scripts for automated motor control

Integration with C++/ Python (dedicated library)


Functional Diagram


Control Methods

Position, current and speed control loops (3 control loops running simultaneously)

Current loop update time: 10uS

Dedicated configurable PID and low pass filter parameters for position, speed and current (Q and D components)

Full Field Oriented Control (FOC) algorithm (sinusoidal and space vector PWM) produces incomparably smooth operation and high degree of torque, velocity, and position control.


Communications interfaces

1 X RS485 port (Modbus RTU or any other customizable protocol – customer specific)


Monitoring functions

Position, speed and current transmitted continuously

Errors (over current, position error, encoder error, over temperature


Field Oriented Control

Field oriented control algorithm’s main task is to take user defined voltage uq and, by continuously reading the position of the motor rotor angle, calculate the appropriate phase voltages ua, ub and uc.



FOC algorithm calculates the phase voltages which create the magnetic field in the motor’s stator which are exactly 90 degrees “behind” the magnetic field of the permanent magnets of the rotor, creating a pushing effect. Here is a very nice animation of what happens inside of the motor when running simplified version of the the FOC called six-step modulation.





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