  This paper proposes a method for direct torque control of Brushless DC (BLDC)
motors. Evaluating the trapezium of back-EMF is needed, and is done via a
sliding mode observer employing just one measurement of stator current. The
effect of the proposed estimation algorithm is reducing the impact of switching
noise and consequently eliminating the required filter. Furthermore, to
overcome the uncertainties related to BLDC motors, Recursive Least Square (RLS)
is regarded as a real-time estimator of inertia and viscous damping
coefficients of the BLDC motor. By substituting the estimated load torque in
mechanical dynamic equations, the rotor speed can be calculated. Also, to
increase the robustness and decrease the rise time of the system, Modified
Model Reference Adaptive System (MMRAS) is applied in order to design a new
speed controller. Simulation results confirm the validity of this recommended
method.
