Position estimation method, position estimation device, and motor module for estimating position of rotor in motor

A motor module comprising:

• a motor that includes a rotor having a plurality of magnetic poles and a stator having a plurality of windings;
• a sensor device that includes N sensor elements arranged such that phases are shifted by an angle of 360 degrees/N, the N sensor elements being N sensors detecting magnetic fields formed by the plurality of magnetic poles and outputting an electrical signal having a magnitude in response to an intensity of each of the detected magnetic fields;
• a signal processing circuit;
• and
• a storage medium that stores learning data including a sequence of a plurality of measurement values which define a waveform characteristic of a first electrical signal output from the sensor device when the rotor is rotating,
• wherein the signal processing circuit executes:
• acquiring a sequence of a plurality of detection values which define a waveform characteristic of a second electrical signal output from the sensor device when the rotor starts rotating from a stopped state;
• and
• performing matching between an increase/decrease pattern of the sequence of the plurality of detection values and an increase/decrease pattern of the sequence of the plurality of measurement values to estimate a relationship between an initial rotation position of the rotor when the first electrical signal is output and an initial rotation position of the rotor when the second electrical signal is output,
• the signal processing circuit further executes:
• subdividing the first electrical signal output from the sensor device into a plurality of segments, and detecting each of the plurality of segments as a subdivision signal,
• associating rotation mechanical angles of the rotor corresponding to the respective segments with all the plurality of segments, and
• outputting a signal indicating a position estimation value of the rotor, the signal having a value that linearly increases in proportion to a rotation mechanical angle of the rotor from a reference position,
• where i is an integer that is equal to or larger than one,
• n is an integer that defines a current time,
• a number of the segment thus specified is i,
• a position of the rotor at a start point of the specified segment is Θoffset [i],
• a difference between a value of a subdivision signal at the start point of the segment and a current value of the subdivision signal is ΔX[n],
• the position estimation value of the rotor is Θ[n], and
• a proportionality factor is k[i],
• a relationship of Θ[n]=Θoffset [i]+k[i]×X[n] is established, and
• the signal indicating the position estimation value of the rotor has a digital value or an analog value which are proportional to Θ.