External field robust angle sensing with differential magnetic field

A magnetic angle sensor device, comprising:

• a shaft rotatable around a rotation axis;
• a magnetic arrangement coupled to the shaft, wherein the magnetic arrangement produces a magnetic field comprising a plurality of diametric magnetic fields arranged along the rotation axis, wherein each of the plurality of diametric magnetic fields has a different magnetic field gradient, and wherein the plurality of diametric magnetic fields include a field direction change such that at least a first one of the plurality of diametric magnetic fields has a first field direction and at least a second one of the plurality of diametric magnetic fields has a second field direction opposite to the first field direction;
• a first magnetic angle sensor provided in the magnetic field at a first location along the rotation axis and configured to generate a first signal that represents a first angle based on a first diametric magnetic field of the magnetic field;
• a second magnetic angle sensor provided in the magnetic field at a second location along the rotation axis and configured to generate a second signal that represents a second angle based on a second diametric magnetic field of the magnetic field;
• and
• a combining circuit configured to determine a combined rotation angle based on the first signal and on the second signal,
• wherein the magnetic arrangement is a quadrupole magnet arrangement that defines a cavity in which the magnetic field is produced, and the first magnetic angle sensor and the second magnetic angle sensor are arranged inside the cavity,
• wherein the magnetic arrangement includes a ring-magnet that defines the cavity, and
• wherein the magnetic arrangement includes a further ring-magnet interposed between and coupled to the ring-magnet and the shaft.

A magnetic angle sensor device, comprising:

• a shaft rotatable around a rotation axis;
• a magnetic arrangement coupled to the shaft, wherein the magnetic arrangement produces a magnetic field comprising a plurality of diametric magnetic fields arranged along the rotation axis, wherein each of the plurality of diametric magnetic fields has a different magnetic field gradient, and wherein the plurality of diametric magnetic fields include a field direction change such that at least a first one of the plurality of diametric magnetic fields has a first field direction and at least a second one of the plurality of diametric magnetic fields has a second field direction opposite to the first field direction;
• a first magnetic angle sensor provided in the magnetic field at a first location along the rotation axis and configured to generate a first signal that represents a first angle based on a first diametric magnetic field of the magnetic field;
• a second magnetic angle sensor provided in the magnetic field at a second location along the rotation axis and configured to generate a second signal that represents a second angle based on a second diametric magnetic field of the magnetic field;
• and
• a combining circuit configured to determine a combined rotation angle based on the first signal and on the second signal,
• wherein the magnetic arrangement is a quadrupole magnet arrangement that defines a cavity in which the magnetic field is produced, and the first magnetic angle sensor and the second magnetic angle sensor are arranged inside the cavity, and
• wherein the magnetic arrangement includes a cylinder magnet having a bore, defining the cavity, that partially extends along the rotation axis from a first end of the cylinder magnet towards a second end of the cylinder magnet.

A method for determining a combined rotation angle of a shaft, wherein the shaft is arranged to rotate about a rotation axis, and a magnetic arrangement, coupled to the shaft, produces a magnetic field comprising a plurality of diametric magnetic fields arranged along the rotation axis, wherein each of the plurality of diametric magnetic fields has a different magnetic field gradient, and wherein the plurality of diametric magnetic fields include a field direction change such that at least a first one of the plurality of diametric magnetic fields has a first field direction and at least a second one of the plurality of diametric magnetic fields has a second field direction opposite to the first field direction, the method comprising:

• generating, by a first magnetic angle sensor provided in the magnetic field at a first location along the rotation axis, a first signal that represents a first angle based on a first diametric magnetic field of the magnetic field;
• generating, by a second magnetic angle sensor provided in the magnetic field at a second location along the rotation axis, a second signal that represents a second angle based on a second diametric magnetic field of the magnetic field;
• and
• determining the combined rotation angle based on the first signal and the second signal,
• wherein the magnetic arrangement is a quadrupole magnet arrangement that defines a cavity in which the magnetic field is produced, and the first magnetic angle sensor and the second magnetic angle sensor are arranged inside the cavity,
• wherein the magnetic arrangement includes a ring-magnet that defines the cavity, and
• wherein the magnetic arrangement includes a disc-magnet interposed between and coupled to the ring-magnet and the shaft.