Sense coil for inductive rotational-position sensing, and related devices, systems, and methods

A rotational-position sensor, comprising:

• a sense coil defining a continuous path for electrical current to flow between a first location and a second location, the continuous path comprising:
• a first sense coil portion defined by a generally clockwise path for the electrical current to flow around an axis of rotation for a target;
• a second sense coil portion defined by a generally counter-clockwise path for the electrical current to flow around the axis of rotation;
• the first sense coil portion and the second sense coil portion together defining at least a first lobe and a second lobe, the second lobe adjacent and meeting with the first lobe at an inter-lobe region;
• the inter-lobe region having a radial-direction-reversal region at which one of the first sense coil portion or the second sense coil portion defined as one of the generally clockwise path or the generally counter-clockwise path changes from being a generally outward path along a portion of the first lobe for the electrical current to flow away from the axis of rotation to a generally inward path along a portion of the second lobe for the electrical current to flow toward the axis of rotation in the same one of the generally clockwise path or the generally counter-clockwise path;
• an oscillator coil arranged around the sense coil, wherein when an excitation signal is carried by the oscillator coil, a magnetic coupling is formed between a sense signal carried at the sense coil and the excitation signal;
• the target arranged to rotate about the axis of rotation perpendicular to a plane of the sense coil and to influence a degree of magnetic coupling between the excitation signal and the sense signal, wherein the sense signal is modulated by a change in the degree of magnetic coupling responsive to the rotation of the target to generate a modulated sense signal;
• and
• an integrated circuit to generate an output signal responsive to the modulated sense signal,
• wherein respective geometries of the first sense coil portion and the second sense coil portion are such that the output signal is characterized by a waveform that, in response to a full rotation of the target in a clockwise direction, generally decreases, plateaus and then generally increases, and in response to a full rotation of the target in a counter-clockwise direction, generally decreases, plateaus, and then generally increases.

A method comprising:

• exciting an oscillatory coil with an oscillating signal;
• and
• receiving a signal induced at a sense coil which defines a continuous path for electrical current to flow between a first location and a second location, the continuous path comprising:
• a first path portion defined as a generally clockwise path for the electrical current to flow around a geometric center of the continuous path;
• a second path portion defined as a generally counter-clockwise path for the electrical current to flow around the geometric center;
• the first path portion and the second path portion together defining at least a first lobe and a second lobe, the second lobe adjacent and meeting with the first lobe at an inter-lobe region;
• and
• the inter-lobe region having a radial-direction-reversal region at which one of the first path portion or the second path portion defined as one of the generally clockwise path or the generally counter-clockwise path changes from being a generally outward path along a portion of the first lobe for the electrical current to flow away from the geometric center to being a generally inward path along a portion of the second lobe for the electrical current to flow toward the geometric center in the same one of the generally clockwise path or the generally counter-clockwise path,
• the signal exhibiting modulation responsive to a rotation of a target relative to the sense coil, the signal exhibiting a 180°-phase change responsive to the target rotating over the radial-direction-reversal region of the sense coil.

A rotational-position sensor comprising:

• a first sense coil defining a first continuous path around an axis, the first continuous path including four respective lobes;
• a second sense coil defining a second continuous path around the axis, the second continuous path including four respective lobes;
• respective ones of the first continuous path and the second continuous path for electrical current to flow between a first location and a second location, the respective ones of the first continuous path and the second continuous path comprising:
• a first path portion defined as a generally clockwise path for the electrical current to flow around the axis;
• a second path portion defined as a generally counter-clockwise path for the electrical current to flow around the axis;
• the first path portion and the second path portion together defining at least a first lobe and a second lobe, the second lobe adjacent and meeting with the first lobe at an inter-lobe region;
• and
• the inter-lobe region having a radial-direction-reversal region at which one of the first path portion or the second path portion changes from being a generally outward path along a portion of the first lobe for the electrical current to flow away from the axis to being a generally inward path along a portion of the second lobe for the electrical current to flow toward the axis in the same one of the generally clockwise path or the generally counter-clockwise path;
• and
• a target to rotate around the axis, the target to cover all but half of a lobe of the four lobes of the first sense coil and all but half of a lobe of the four lobes of the second sense coil.

An apparatus comprising:

• a rotational-position sensor to sense a signal that exhibits amplitude modulation as a target rotates around an axis of rotation above a sense coil;
• the sense coil defining a continuous path for electrical current to flow between a first location and a second location, the continuous path comprising:
• a first path portion defined as a generally clockwise path for the electrical current to flow around the axis;
• a second path portion defined as a generally counter-clockwise path for the electrical current to flow around the axis;
• the first path portion and the second path portion together defining at least a first lobe and a second lobe, the second lobe adjacent and meeting with the first lobe at an inter-lobe region;
• and
• the inter-lobe region having a radial-direction-reversal region at which one of the first path portion or the second path portion changes from a generally outward path along a portion of the first lobe for the electrical current to flow away from the axis to a generally inward path along a portion of the second lobe for the electrical current to flow toward the axis in the same one of the generally clockwise path or the generally counter-clockwise path,
• the amplitude modulation comprising two sinusoidal cycles per target rotation, the amplitude modulation exhibiting a 180°-phase shift responsive to the target rotating over the radial-direction-reversal region of the sense coil.