Controller for permanent magnet synchronous motor, image forming apparatus, and control method

An image forming apparatus comprising:

• a permanent magnet synchronous motor having a rotor using a permanent magnet, the rotor rotating by a rotating magnetic field caused by a current flowing through a winding;
• a controller configured to control the permanent magnet synchronous motor;
• and
• a printer unit configured to form an image onto paper while feeding the paper by using a rotating member of which rotation is driven by the permanent magnet synchronous motor;
• wherein
• the controller includes
• a drive portion configured to apply a current to the winding to drive the rotor,
• a current detector configured to detect the current flowing through the winding,
• an estimating portion configured to determine an estimated value of a rotational speed of the rotor and an estimated value of a position of magnetic poles of the rotor based on a value of the current detected by the current detector and a parameter value indicating an interlinkage magnetic flux caused by the permanent magnet across the winding,
• a control unit configured to control the drive portion to cause the rotating magnetic field based on the estimated value of the rotational speed and the estimated value of the position of the magnetic poles, and
• a correction portion configured to correct the parameter value indicating the interlinkage magnetic flux based on correction information, the correction information being determined based on a temperature of the winding and a relationship between the temperature of the winding and a temperature of the permanent magnet, and
• the estimating portion uses the parameter value corrected by the correction portion to determine the estimated value of the rotational speed and the estimated value of the position of the magnetic poles.

A method for controlling a permanent magnet synchronous motor having a rotor using a permanent magnet, the rotor rotating by a rotating magnetic field caused by a current flowing through a winding, the method comprising:

• detecting the current flowing through the winding;
• correcting a parameter value indicating an interlinkage magnetic flux caused by the permanent magnet across the winding based on correction information, the correction information being determined based on a temperature of the winding and a relationship between the temperature of the winding and a temperature of the permanent magnet;
• estimating a rotational speed of the rotor and a position of magnetic poles of the rotor based on a value of the current detected and the parameter value corrected;
• and
• rotating the rotor by causing, as the rotating magnetic field, a magnetic field based on the rotational speed and the position of the magnetic poles.