Electric power steering apparatus

An electric power steering apparatus that driving-controls a three-phase brushless motor which applies an assist torque to a steering mechanism of a vehicle by using a current command value calculated based on at least a steering torque, and vector-controls said three-phase brushless motor by using dq-axes command values that are converted from said current command value via an inverter, comprising:

• a three-phase disturbance observer to compensate respective phase disturbance voltages, which include a dead time of said inverter, for 3-phase voltage command values,
• wherein said 3-phase disturbance observer includes phase observer sections comprising a motor model, an inverse motor model and a low pass filter for each of three phases, and
• wherein said phase observer sections comprise:
• a first subtracting section to subtract a disturbance estimation voltage from a phase voltage that is converted into three phases;
• a gain section to multiply a subtraction value from said first subtracting section by a gain;
• said motor model to input a phase voltage that adds a disturbance element to an output of said gain section, and to output a phase current;
• said inverse motor model to input said phase current;
• said low pass filter to input said subtraction value;
• and
• a second subtracting section to subtract an output of said low pass filter from an output of said inverse motor model, and to output said disturbance estimation voltage.

An electric power steering apparatus that driving-controls a three-phase brushless motor which applies an assist torque to a steering mechanism of a vehicle by using a current command value calculated based on at least a steering torque, and vector-controls said three-phase brushless motor by using dq-axes command values that are converted from said current command value via an inverter, comprising:

• a three-phase disturbance observer to compensate respective phase disturbance voltages, which include a dead time of said inverter, for three-phase voltage command values,
• wherein said three-phase disturbance observer comprises:
• phase observer sections comprising a motor model;
• an inverse motor model and a low pass filter for two phases among said three phases;
• and
• an other-phase observer section, for an other phase among said three phases, comprising a motor model for an inverted phase voltage obtained by adding two phase voltages among said three phases and by inverting a sign of an added phase voltage.