Angle determinating method using encoder signal with noise suppression, adjusting method for output signal of encoder and absolute encoder

A method of correcting an outputted signal by an encoder, the method comprising:

• generating a first angle data based on a rotation of a bipolar magnet and a second angle data based on a rotation of the multipolar magnet;
• determining a first waveform signal based on the first angle data and a second waveform signal based on the second angle data;
• converting the first waveform signal into a third waveform signal having a cycle similar to the second waveform signal;
• determining a difference between the second waveform signal and the third waveform signal;
• converting the difference based on a period of the first waveform signal to determine a phase difference;
• and
• correcting the first waveform signal based on the phase difference.

An absolute encoder comprising:

• a first magnetic sensor outputting first angle data based on a rotation of a bipolar magnet located at a rotation axis;
• a second magnetic sensor outputting second angle data based on a rotation of a multipolar magnet located at the rotation axis;
• a converter converting output signals of the first magnetic sensor and the second magnetic sensor into digital signals;
• a storage device comprising a table with angle result values and absolute angles;
• and
• a signal processing circuit configured to:
• determine a first waveform signal based on the first angle data and a second waveform signal based on the second angle data;
• convert the first waveform signal into a third waveform signal having a cycle similar to the second waveform signal;
• calculate an angle result value as a function of the second angle data and a reference value determined based on a difference between the second waveform signal and the third waveform signal;
• and
• calculate an absolute angle using the calculated angle result value and the table.

A method of correcting a number of rotations by an encoder, the method comprising:

• generating a first angle data based on a rotation of a bipolar magnet and a second angle data based on a rotation of a multipolar magnet;
• calculating a first number of rotations of the multipolar magnet based on the first angle data and a number of poles of the multipolar magnet;
• converting the second angle data into a fourth angle data using the first number of rotations;
• and
• calculating an error value obtained by subtracting the second angle data from the fourth angle data, and correcting the first number of rotations to a second number of rotations of the multipolar magnet based on a range of the error value.

A method of correcting a number of rotations by an encoder, the method comprising:

• generating a first angle data based on a rotation of a first magnet and a second angle data based on a rotation of a second magnet;
• subtracting the second angle data from the first angle data to obtain an intermediate value;
• calculating a number of rotations of the first magnet based on the intermediate value and a rotation ratio of the second magnet with respect to one rotation of the first magnet;
• converting the first angle data into a fifth angle data using the number of rotations of the first magnet and the rotation ratio of the second magnet;
• and
• calculating an error value by subtracting the intermediate value from the fifth angle data, and correcting the number of rotations of the first magnet based on a range of the error value.