Multiphase synchronous motor controller with angle tracking

A controller for a multiphase synchronous motor with a rotor and a plurality of phases for receiving a plurality of motor vectors, the controller comprising a controller circuit configured to, for a motor flux vector:

• set a first phase of the motor to a floating state in which the first phase is electrically floating;
• set a voltage across a second phase of the motor for a first period;
• receive first voltage samples associated with the first phase in the first period;
• set the voltage across the second phase of the motor for a second period, in which the first period and the second period are periods of one or more pulse width modulation cycles, in which a polarity of the voltage across the second phase in the second period is opposite to a polarity of the voltage across the second phase in the first period;
• receive second voltage samples associated with the first phase in the second period;
• determine a position of the rotor based on the first and second voltage samples,
• wherein
• the controller circuit further comprises a digital sampling filter synchronized with a bipolar pulse width modulated (PWM) signal associated with PWM states associated with the first and second voltage samples, and
• the digital sampling filter is configured to compensate for mutual capacitance effects and provide the rotor position in accordance with a mutual inductance between the first and second phases;
• and
• on initialization of the motor
• obtain first and second voltage samples for three consecutive motor vectors of the plurality of motor vectors before said determining the position of the rotor,
• determine a direction of travel of the rotor by comparing an angular velocity of the rotor with a predetermined threshold, and
• apply a 180 degree correction to the position of the rotor if the determined direction of travel opposes an expected direction of travel.