Control device and drive control method

A control device that performs drive control of a multiphase rotary machine, the control device comprising:

• current detection circuitry to detect a rotary machine current flowing through the rotary machine;
• drive voltage command calculation circuitry to generate a drive voltage command for driving the rotary machine based on the rotary machine current and an estimated value of a rotor position of the rotary machine;
• voltage application circuitry to apply a voltage to the rotary machine based on the drive voltage command generated;
• and
• position estimation circuitry to estimate the rotor position based on the rotary machine current, wherein
• the position estimation circuitry determines a type of a voltage vector output from the voltage application circuitry based on a gate signal of the voltage application circuitry, calculates a change amount of the rotator current for each type of the voltage vector determined, generates an AC signal having a DC component of zero and changing at a double angle of the rotor position based on a rotary machine current change amount that is a calculation result, and estimates the rotor position based on the AC signal.