Motor control in brief
- Field-oriented control (FOC) gives smooth torque, low noise and high efficiency for BLDC and PMSM motors, at the cost of a more demanding implementation than six-step commutation.
- Sensorless control removes the Hall or encoder cost but needs careful start-up and low-speed handling.
- Hardware matters as much as code: gate-driver selection, current sensing, dead time and layout decide whether the loop is stable.
- Protection is not optional: overcurrent, overvoltage, over-temperature and stall detection should be in hardware and firmware.
Control strategies compared
| Method | Strength | Limitation |
|---|---|---|
| Six-step (trapezoidal) | Simple, cheap, robust | Torque ripple and audible noise |
| Sensored FOC | Smooth torque from standstill | Needs encoder or Hall sensors |
| Sensorless FOC | No position sensor, high efficiency | Harder start-up and very low speed |
| Stepper microstepping | Open-loop positioning | Can lose steps without feedback |
What we design
- Three-phase inverter stages using MOSFET or GaN devices with suitable gate drivers.
- Shunt-based current sensing with correctly timed ADC sampling.
- Clarke and Park transforms, PI current and speed loops, and field weakening where required.
- Sensorless observers and start-up sequences.
- Brake, regeneration and bus-voltage handling.
- Communication: CAN, UART or Modbus for commands and diagnostics.
Tuning and validation
Loop tuning is done on the real motor and load, not only in simulation. We record current, speed and bus waveforms with an oscilloscope, test at stall, at maximum load and at supply extremes, and measure temperature rise. Layout and EMC are handled with our PCB design team, because switching edges and current loops dominate noise.
Typical applications
- Fans, pumps and compressors.
- Robotics joints and drive wheels, linking to our robotics engineering work.
- Light electric vehicles and drones.
- Industrial actuators and conveyors.
Sources and further reading
- STMicroelectronics — STM32 Motor Control SDK — Reference FOC implementation and tools.
- SimpleFOC — Open-source FOC learning resource and library.
- IPC — PCB design and assembly standards relevant to power-stage layout.
Last reviewed: October 2026. Regulations and product availability change; confirm current rules with the issuing authority before you commit to a design.