Determining an initial position of a rotor of a permanent magnet synchronous machine

A method comprising:

• generating a motor driver voltage signal comprising at least a first portion, a second portion, and a third portion, wherein the first portion has a first non-zero voltage during a first temporal duration, the second portion has a second non-zero voltage during a second temporal duration, and the third portion has a substantially zero voltage during a third temporal duration;
• the first portion has a first polarity and the second portion has a second polarity that is opposite to the first polarity;
• and the first temporal duration and the second temporal duration are different;
• applying the motor driver voltage signal to a synchronous machine;
• measuring an induced current in the motor after applying the motor driver voltage signal to the synchronous machine;
• determining a d-axis current component and a q-axis current component based on the measured induced current;
• and
• determining the initial angular position of the rotor based on the d-axis current component and/or the q-axis current component.

A system for determining an initial angular position of a rotor of a synchronous machine, the system comprising:

• a motor driver module configured to provide a motor driver voltage signal to the synchronous machine, the motor driver voltage signal being sufficient to induce an electrical current in the synchronous machine;
• and
• a rotor position determination module configured to:
• receive an indication of the current induced in the machine and to determine the initial position of the rotor based on the indication of the current induced in the machine, wherein the indication of the current induced in the synchronous machine comprises an indication of a current drawn by each of three phases of the synchronous machine, and the rotor position determining module comprises:
• a transformation module configured to convert the indication into a d-axis current component and a q-axis current component, the d-axis current component and the q-axis current component being associated with a rotating rectangular coordinate system defined by a d-axis and a q-axis;
• a regulator module configured to compare the q-axis current component to a reference and to determine a first estimate of a rotational angle of the rotor;
• a comparator module configured to compare the d-axis current component to a prior d-axis current component and to determine a direction of rotation of the rotor based on the comparison;
• and
• a position determination module configured to estimate the position of the rotor based on the first estimate of the rotational angle of the rotor and the direction of rotation of the rotor, and
• wherein
• the motor driver voltage signal comprises at least a first portion, a second portion, and a third portion,
• the first portion has a first non-zero voltage during a first temporal duration, the second portion has a second non-zero voltage during a second temporal duration, and the third portion has a substantially zero voltage during a third temporal duration,
• the first portion has a first polarity and the second portion has a second polarity that is opposite to the first polarity, and
• the first temporal duration and the second temporal duration are different.