Patent ID: 8531145

Claim:
A method for controlling a permanent magnet motor with at least one phase, a coil, a rotor, and a power transistor stage, the method comprising the steps of: controlling the powering of each motor phase using a pulse width modulation (PWM) current control method initiating an OFF state of the phase power transistors on a high level current threshold and initiating an ON state of the phase power transistors on a low level current threshold; determining for at least one phase, i) the time duration of the OFF state of a PWM period and ii) the time duration of the ON state for the same PWM period; calculating at least one of i) the phase back EMF (BEMF) voltage and ii) the phase inductance value for the at least one phase from the determined time durations of the OFF and ON states time durations and from the high and low level current threshold values of the at least one phase; determining at least one of i) the rotor position and ii) the rotor speed from at least one of i) the calculated BEMF voltage of the at least one phase and ii) the inductance value of the at least one phase; and controlling the powering of each motor phase as a function of at least one of i) the rotor position and ii) the rotor speed, wherein said calculating of at least one of i) the phase back EMF (BEMF) voltage and ii) the phase inductance value for the at least one phase is calculated by a mathematical formula depending on the four parameters including i) determined time duration of the OFF state of the at least one phase, ii) determined time duration of the ON state of the at least one phase, iii) high level current threshold of the at least one phase, and iv) low level threshold values of the at least one phase.