Machine learning apparatus and method for learning correction value in motor current control, correction value computation apparatus including machine learning apparatus and motor driving apparatus

A motor driving apparatus, comprising:

• a correction value computation apparatus for current control in the motor driving apparatus, the correction value computation apparatus comprising:
• a machine learning apparatus that learns correction values associated with the current control based on a current command and a current feedback value in the motor driving apparatus for a three-phase AC motor, the machine learning apparatus comprising:
• a state observation unit that observes a state variable including at least one of data regarding an error between a rotor position command to the three-phase AC motor and a rotor actual position of the three-phase AC motor, data regarding temperature in the motor driving apparatus, data regarding temperature of the three-phase AC motor, and data regarding a voltage of the motor driving apparatus;
• and
• a learning unit that learns a current feedback offset correction value used for correcting an offset amount included in the current feedback value, an inter-current-feedback-phase unbalance correction value used for correcting an unbalance between phases in the current feedback value, and a current command correction value for a dead zone used for correcting a current command in order to compensate a decreased amount of current due to a switching dead zone by which switching elements of upper and lower arms in the same phase of an inverter for motor power supply provided in the motor driving apparatus are not simultaneously turned on, in accordance with a training data set defined by the state variable;
• and
• a decision-making unit which decides the current feedback offset correction value, the inter-current-feedback-phase unbalance correction value, and the current command correction value for a dead zone, on the basis of a result of learning by the learning unit in accordance with the training data set in response to an input of the state variable;
• the motor driving apparatus further comprising:
• a rectifier which rectifies input AC voltage input from an AC power supply side, and outputs DC voltage to the DC link side;
• the inverter for motor power supply which is connected to the rectifier through the DC link, and converts the DC voltage on the DC link side into AC voltage by ON/OFF driving of an internal switching element to output the AC voltage to the three-phase AC motor side;
• a current detection unit which detects current flowing into the three-phase AC motor from the inverter for motor power supply to output the current as the current feedback value;
• a current feedback offset correction unit which corrects the offset amount included in the current feedback value using the current feedback offset correction value;
• an inter-current-feedback-phase unbalance correction unit which corrects the unbalance between phases in the current feedback value using the inter-current-feedback-phase unbalance correction value;
• a current command correction unit for a dead zone which corrects the current command so as to compensate a decreased amount of current due to a switching dead zone by which switching elements of upper and lower arms in the same phase of the inverter for motor power supply are not simultaneously turned on, by using the current command correction value for a dead zone;
• a position detection unit which detects the rotor actual position of the three-phase AC motor;
• an error measuring unit which measures the error between the rotor position command to the three-phase AC motor and the rotor actual position;
• a motor-driving-apparatus temperature measuring unit which measures the temperature in the motor driving apparatus;
• a motor temperature measuring unit which measures the temperature of the three-phase AC motor;
• a current control unit which controls a switching operation of the switching elements of the inverter for motor power supply so that the current command is equal to the current feedback value;
• and
• a voltage detection unit which detects at least one of the input AC voltage input into the motor driving apparatus, the DC link voltage between the rectifier and the inverter for motor power supply, and the control voltage used to drive a control device including the current control unit provided in the motor driving apparatus.

A motor driving method with current control based on a current command and a current feedback value in a motor driving apparatus for a three-phase AC motor, the motor driving method comprising:

• observing a state variable including at least one of data regarding an error between a rotor position command to the three-phase AC motor and a rotor actual position of the three-phase AC motor, data regarding temperature in the motor driving apparatus, data regarding temperature of the three-phase AC motor, and data regarding a voltage of the motor driving apparatus;
• learning a current feedback offset correction value used for correcting an offset amount included in the current feedback value, an inter-current-feedback-phase unbalance correction value used for correcting an unbalance between phases in the current feedback value, and a current command correction value for a dead zone used for correcting a current command in order to compensate a decreased amount of current due to a switching dead zone by which switching elements of upper and lower arms in the same phase of an inverter for motor power supply provided in the motor driving apparatus are not simultaneously turned on, in accordance with a training data set defined by the state variable;
• deciding the current command correction value for a dead zone, on the basis of a result of learning by the learning unit in accordance with the training data set in response to an input of the state variable;
• correcting the current command for the three-phase AC motor by using the current command correction value for a dead zone to generate a corrected current command;
• and
• controlling driving of the three-phase AC motor based on the corrected current command.