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FIELD ORIENTED CONTROL MOTOR DRIVER

INTRO

 

I’m currently working on the design and construction of a Field Oriented Control (FOC) Motor Driver for Brushless DC (BLDC) Motors aimed at the hobbyist robotics community. BLDC Motors are great for robotics applications as they have high torque density allowing them to be directly driven (no gearbox)and to have highly dynamic control. However currently hobbyists are unable to fully take advantage of these motors since none of the off-the-shelf drivers offer low speed operation and position control.  

GOALS

  • efficient and smooth high and low speed control

  • precise rotor position sensing,

  • easy to use for the hobby consumer

EFFICIENT AND SMOOTH HIGH AND LOW SPEED CONTROL

​Field Orientated Control is currently the most efficient way to drive BLDCs. It also provides smooth motion at low speeds and efficient operation at high speeds. Other commutation methods such as sinusoidal commutation and trapezoidal commutation can only provide one or the other. Sinusoidal is inefficient at high speeds and Trapezoidal causes torque ripple at low speeds.

To offer precise speed and position control the driver is integrated with a high resolution absolute angle encoder. The encoder is also going to be used to commutate the motor and will be included in our driver package.  This sensor solution was chosen because the mounting of the sensor is not dependant on the motor size. This gives the user more versatility.

To make the motor easy to use for the user the motor is controlled using a PWM signal which is common for drivers out in the market.  Speed and position information will be sent over SPI to the users microcontroller. The driver can also be used to power the microcontroller, a popular feature in other existing drivers.  There is also clear labelling on the driver PCB so that the user doesn’t have to keep referring to product documentation.

PRECISE ROTOR POSITION SENSING

EASY TO USE FOR HOBBYISTS

CURRENT PROGRESS

  • Research

  • Part selection

  • PCB design

  • PCB and parts ordered

  • Cable assemblies created

  • Components soldered

  • Encoder mount design

  • Firmware flow planning

FUTURE WORK

  • Firmware implementation

  • Testing

  • Demo

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