Permanent Magnet Brushless DC (PMBLDC) motor has been used extensively to achieve better energy efficiency and control performance. PMBLDC motors are electronically controlled via various control techniques.

There are two motor control approaches:

1. Stationary Regulator Control, operates on the actual phase currents
   • Square Wave Control
   • Sine Wave (Halbach) Control
2. Synchronous Regulator Control, operates on the rotatory direct and quadrature axis (d-q axis)
   • Field-oriented control (FOC)
   • Direct Torque Control (DTC)

Square Wave and Sine Wave Control

Phase back-emf and current

• Preferred control method for motors with trapezoid back-emf
• Generally, hall sensors are used to sense position
• The switching happens based on the zero-crossing of back-emf

• Preferred control method for motors with sinusoidal back-emf
• Generally, encoders are used to sense the position
• Continuous switching depending on absolute position

Two Stationary Regulator Control Methods Comparison