One embodiment of the present invention is a method for acquiring a value of back electromotive force of an electric motor which includes: (a) applying a first current as input to the electric motor and measuring a first voltage across the electric motor; (b) applying a second current as input to the electric motor and measuring a second voltage across the electric motor; (c) determining a resistance of the electric motor using the first and second voltages and the first and second currents; (d) applying a third current to the electric motor and measuring a third voltage across the electric motor; and (e) determining a value of the back electromotive force using: (i) the third current, the third voltage, the first current, the first voltage, and the resistance; or (ii) the third current, the third voltage, the second current, the second voltage, and the resistance.