Apparatus for estimating rotor position of brushless motors and system and method for controlling start-up of brushless motors

A start-up control system for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and carries out start-up control on the brushless motor, the control system comprising:

• a current detecting means for directly or indirectly detecting wiring current which is current passed through the coils;
• a voltage supplying means capable of supplying voltage to the coils so that magnetic flux is produced in each of a plurality of directions perpendicular to the direction of rotation of the rotor;
• a power source voltage detecting means for detecting the voltage of a power source used for the voltage supply;
• a voltage supply controlling means which controls the voltage supplying means so that magnetic flux is produced in sequence in predetermined directions among the directions and, when a predetermined voltage supply time has passed, terminates the supply of voltage by the voltage supplying means;
• a current correcting means which corrects wiring current detected at the current detecting means based on power source voltage detected at the power source voltage detecting means and preset reference voltage in each direction in which magnetic flux is produced under control of the voltage supply controlling means;
• a rotor position estimating means which compares wiring currents corrected by the current correcting means to identify a direction in which the peak amplitude value of wiring current is maximized and estimates the stop position of the rotor based on the identified direction;
• and
• a motor start-up controlling means which determines a direction of magnetic flux for causing commutation in the rotor from among the directions based on the stop position of the rotor estimated at the rotor position estimating means, and controls the voltage supplying means so as to produce magnetic flux in that direction and starts the brushless motor.

A start-up control method for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and is used to carry out start-up control on the brushless motor, the control method comprising:

• first step of detecting the voltage of a power source for supplying voltage to the coils;
• second step of supplying voltage to the coils so that magnetic flux is produced in predetermined directions among a plurality of directions perpendicular to the direction of rotation of the rotor;
• third step of detecting wiring current which is current passed through the coils;
• fourth step of, when a voltage supply time has passed, terminating the supply of the voltage;
• fifth step of correcting the wiring current based on power source voltage detected at the first step and predetermined reference voltage;
• sixth step of repeating the steps including the first step to the fifth step in all the predetermined directions;
• seventh step of comparing wiring currents corrected at the fifth step to identify a direction in which the peak amplitude value of wiring current is maximized from among the predetermined directions and estimating the stop position of the rotor based on the identified direction;
• and
• eighth step of determining a direction of magnetic flux for causing commutation in the rotor from among the directions based on the estimated stop position of the rotor, and controlling the voltage supplying means so as to produce magnetic flux in that direction and starting the brushless motor.

An apparatus for estimating rotor position for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and estimates the stop position of the rotor, the estimating apparatus comprising:

• a current detecting means for directly or indirectly detecting wiring current which is current passed through the coils;
• a voltage supplying means capable of supplying voltage to the coils so that magnetic flux is produced in each of a plurality of directions perpendicular to the direction of rotation of the rotor;
• a power source voltage detecting means for detecting the voltage of a power source used for the voltage supply in each of the predetermined directions;
• a voltage supply controlling means which controls the voltage supplying means so that magnetic flux is produced in sequence in predetermined directions among the directions and, when the wiring current detected at the current detecting means exceeds a predetermined threshold value, terminates the supply of voltage by the voltage supplying means;
• a supply period acquiring means which acquires a period equivalent value equivalent to a voltage supply period in each direction in which magnetic flux is produced under control of the voltage supply controlling means;
• a period value correcting means which corrects a period equivalent value acquired at the supply period acquiring means based on power source voltage detected at the power source voltage detecting means and predetermined reference voltage;
• and
• a rotor position estimating means which compares period equivalent values corrected by the period value correcting means to identify a direction in which the voltage supply period is minimized and estimates the stop position of the rotor based on the identified direction.

A start-up control system for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and carries out start-up control on the brushless motor, the control system comprising:

• a current detecting means for directly or indirectly detecting wiring current which is current passed through the coils;
• a voltage supplying means capable of supplying voltage to the coils so that magnetic flux is produced in each of a plurality of directions perpendicular to the direction of rotation of the rotor;
• a power source voltage detecting means for detecting the voltage of a power source used for the voltage supply;
• a voltage supply controlling means which controls the voltage supplying means so that magnetic flux is produced in sequence in predetermined directions among the directions and, when the wiring current detected at the current detecting means exceeds a predetermined threshold value, terminates the supply of voltage by the voltage supplying means;
• a supply period acquiring means which acquires a period equivalent value equivalent to a voltage supply period in each direction in which magnetic flux is produced under control of the voltage supply controlling means;
• a period value correcting means which corrects a period equivalent value acquired at the supply period acquiring means based on power source voltage detected at the power source voltage detecting means and predetermined reference voltage;
• a rotor position estimating means which compares period equivalent values corrected by the period value correcting means to identify a direction in which the voltage supply period is minimized and estimates the stop position of the rotor based on the identified direction;
• and
• a motor start-up controlling means which determines a direction of magnetic flux for causing commutation in the rotor from among the directions based on the stop position of the rotor estimated at the rotor position estimating means, and controls the voltage supplying means so as to produce magnetic flux in that direction and starts the brushless motor.

A start-up control method for brushless motors which includes a brushless motor having a stator with coils wound thereon and a rotor rotatably supported relative to the stator and is used to carry out start-up control on the brushless motor, the control method comprising:

• first step of detecting the voltage of a power source for supplying voltage to the coils;
• second step of supplying voltage to the coils so that magnetic flux is produced in predetermined directions among a plurality of directions perpendicular to the direction of rotation of the rotor and starting counting at the same time;
• third step of determining that wiring current which is current passed through the coils has exceeded a predetermined threshold value;
• fourth step of, when the wiring current is determined to have exceeded the predetermined threshold value, terminating the supply of the voltage and terminating counting;
• fifth step of correcting a count corresponding to the voltage supply period based on power source voltage detected at the first step and predetermined reference voltage;
• sixth step of repeating the steps including the first step to the fifth step in all the predetermined directions;
• seventh step of comparing counts corrected at the fifth step to identify a direction in which the count is minimized from among the predetermined directions and estimating the stop position of a rotor based on the identified direction;
• and
• eighth step of determining a direction of magnetic flux for causing commutation in the rotor from among the directions based on the estimated stop position of the rotor, and controlling the voltage supplying means so as to produce magnetic flux in that direction and starting the brushless motor.