Arrangement, method and sensor for measuring an absolute angular position using a multi-pole magnet

A method for determining an angular position of a rotor with respect to a stator, comprising:

• providing a system that includes
• the rotor rotatable around a rotation axis;
• the stator having a fixed position with respect to the rotation axis;
• a magnetic source mounted on the rotor for creating a magnetic field, the magnetic source being a multi-pole magnet having a number of magnetic poles for generating a periodically repetitive magnetic field pattern with respect to the rotation axis, the number of magnetic poles being at least four;
• a sensor mounted on the stator and comprising a plurality of sensor elements for measuring at least one magnetic field component of the magnetic field and for providing a measurement signal indicative of the at least one magnetic field component, the number of sensor elements being twice the number of magnetic poles of the multi-pole magnet, the sensor being located centered around the rotation axis and being located in a plane perpendicular to the rotation axis at a first distance from the magnetic source;
• wherein
• the sensor elements are located on a circle at a second distance from the rotation axis and are oriented for detecting the at least one magnetic field component;
• and
• the plurality of sensor elements are partitioned in at least a first group and a second group and a third group and a fourth group, the elements within each group being located at equidistant angular positions on the circle,
• the angular distance between an element of the first group and an element of the second group being equal to 180° divided by the number of magnetic poles of the magnetic source,
• the angular distance between an element of the third group and an element of the first group being equal to 360° divided by the number of magnet poles of the magnetic source, and
• the angular distance between an element of the fourth group and an element of the first group being equal to 540° divided by the number of magnet poles of the magnetic source;
• calculating a first sum or a first average of the signals provided by the first group of sensor elements;
• calculating a second sum or second average of the signals provided by the second group of elements;
• calculating a third sum or third average of the signals provided by the sensor elements of the third group of elements;
• calculating a fourth sum or fourth average of the signals provided by the sensor elements of the fourth group of elements;
• and
• determining the angular position of the rotor based on one or more numbers selected from the group consisting of the first sum, the first average, the second sum, the second average, the third sum, the third average, the fourth sum and the fourth average.

An integrated sensor circuit for measuring an angular position of a rotor with respect to a stator, the rotor being rotatable around a rotation axis and a magnetic source being mounted on the rotor for creating a magnetic field, the magnetic source being a multi-pole magnet having a number of magnetic poles for generating a periodically repetitive magnetic field pattern with respect to the rotation axis, the number of magnetic poles being at least four;

• the stator having a fixed position with respect to the rotation axis, the integrated sensor circuit being mountable to the stator in a vicinity of the multi-pole magnet and in line with the rotation axis in a plane perpendicular to the rotation axis at a first distance from the magnetic source, the integrated sensor circuit comprising:
• a plurality of sensor elements, the number of sensor elements being twice the number of magnetic poles of the multi-pole magnet, each of the sensor elements being adapted for measuring at least one magnetic field component of the magnetic field and for respectively providing a measurement signal indicative of the strength of the at least one magnetic field component at a respective location of each of the sensor elements,
• the sensor elements being located on a circle at a distance from the rotation axis, and being oriented for detecting the at least one magnetic field component;
• the plurality of sensor elements being partitioned in a first group and a second group and a third group and a fourth group, the elements within each group being located at equidistant angular positions on the circle,
• the angular distance between an element of the first group and an element of the second group being equal to 180° divided by the number of magnet poles of the magnetic source,
• the angular distance between an element of the third group and an element of the first group being equal to 360° divided by the number of magnet poles of the magnetic source, and
• the angular distance between an element of the fourth group and an element of the first group being equal to 540° divided by the number of magnet poles of the magnetic source;
• a calculator that determines the angular position of the rotor from the provided signals;
• wherein:
• the calculator are adapted to
• calculate a first sum or first average of the signals provided by the elements of the first group, and
• calculate a second sum or second average of the signals provided by the elements of the second group, and
• calculate a third sum or third average of the signals provided by the elements of the third group, and
• calculate a fourth sum or fourth average of the signals provided by the elements of the fourth group, and
• determine the angular position of the rotor based on one or more number selected from the group consisting of the first sum, first average, the second sum and the second average, the third sum, the third average, the fourth sum and the fourth average.