Sensorless motor assembly and method of controlling the same
AssigneeTechtronic Cordless GP
InventorsHai Ming Luo, Hai Bo Ma, Yong Sheng Gao
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Abstract
A method of controlling a sensorless motor (32). The method contains the steps of determining a current speed of the motor (32); selectively using a first method, a second method, or a third method to determine a position of a rotor of the motor (32), depending on the current speed of the motor (32); and transmitting a drive signal to the motor (32) based on the determined position of the rotor. A sensorless motor assembly is also disclosed. According to the method, multiple rotor position detection methods are provided to the sensorless motor (32) which cover a full speed range of the motor (32).
Claims16
A method of controlling a sensorless motor, the method comprising:
- a) determining a current speed of the motor;
- b) selectively using a first method, a second method, or a third method to determine a position of a rotor of the motor, depending on the current speed of the motor;
- and
- c) transmitting a drive signal to the motor based on the determined position of the rotor;
- wherein the first method is chosen in step b) if the motor is at zero speed, wherein the second method is chosen in step b) if the current speed of the motor is above zero but below a threshold, and wherein the third method is chosen in step b) if the current speed of the motor is above the threshold;
- and
- wherein in case of the first method, step b) further includes:
- d) sending a plurality of voltage pulses to multiple phases of the motor,
- e) in response, detecting a peak value in a total current of the motor, and
- f) determining the position of the rotor based on an occurrence time of the peak value.
A sensorless motor assembly, comprising
- a) a motor that comprises a stator and a rotor;
- b) a switching module adapted to connect the motor to a power supply;
- and
- c) a motor controller connected to the switching module;
- wherein the motor controller is adapted to determine a position of the rotor using a first method, a second method, or a third method, depending on a current speed of the rotor;
- wherein the motor controller is adapted to determine the position of the rotor using the first method if the motor is at zero speed;
- and
- wherein a current sensor is connected to the motor, and wherein in a case of the first method, the motor controller is configured to:
- d) control the switching module to send a plurality of voltage pulses to multiple phases of the motor,
- e) in response, read an electromotive force and a peak value in a total current of the motor from the current sensor, and
- f) determine the position of the rotor based on the peak value and the electromotive force.
Dependencies are inferred from the claim text.