Inductive movement sensor
A measuring technique, useful in diverse applications such as in joysticks and power tools, wherein an interfering member is positioned so that upon movement e.g. by a user a magnetic field, established by a solenoid coil, is altered and a change in a measured inductance of the coil is related to the position, or the extent of movement of the interfering member, relative to the coil.
1 . A method of measuring movement of a component relative to a structure wherein the structure comprises an inductor with a core and the component includes an interfering member linked to a lever or trigger mechanism, said lever or trigger mechanism being rotationally movable to a limited extent about a rotational axis and wherein the interfering member is at least partially positioned inside the core of the inductor at a zero position, and is rotationally moveable about said rotational axis while remaining inside said core in response to a user press applied to said lever or trigger mechanism, and wherein the method includes the steps of using the interfering member to interfere with the magnetic field of said inductor by moving the interfering member into the core of said inductor, measuring a change in the inductance of the inductor in response to said movement and relating the change in the measured inductance to said movement relative to the inductor, or to the position of the interfering member inside the core of the inductor.
2 . The method of claim 1 wherein the inductor is a solenoid-type inductor and comprises a plurality of windings which extend around a core with a longitudinal axis and wherein the interfering member is movable in the core along said longitudinal axis.
3 . The method of claim 1 wherein the inductor comprises a flat coil formed on at least one side of a printed circuit board and lies in a plane, and wherein the interfering member is movable relative to the coil in a direction which is perpendicular or substantially perpendicular to said plane.
4 . The method of claim 1 applied in a joystick or thumb stick device.
5 . The method of claim 1 wherein said structure further comprises a capacitance measurement circuit which determines if there is contact between a user and the lever or trigger mechanism and a device which uses information pertaining to such contact for calibration purposes.
6 . The method of claim 1 wherein the inductor comprises a solenoid-type conductor with a first and second part, said first and second part being separated by a gap extending along a longitudinal direction, and wherein the inductor further comprises a plurality of windings which extend around a longitudinal core and wherein the interfering member is movable into the core at said gap in a direction which is transverse to the longitudinal axis of the core.
7 . The method of claim 6 wherein the interfering member is selected from the following: an interfering member of irregular cross section, an interfering member with a plurality of stepped formations; and an interfering member comprising a plurality of spaced apart components.
8 . The method of claim 1 wherein the inductance is measured using a charge transfer measurement process and wherein the method includes the step of shorting one end of the inductor to ground during each charging phase of the charge transfer measurement process.
9 . The method of claim 1 , wherein the interfering member is a metal member or a ferrite member.
10 . An inductive sensor for measuring movement of a component relative to a structure, wherein said structure comprises an inductor with a core, and wherein said component comprises an interfering member that is coupled to a lever or trigger mechanism, said lever or trigger mechanism being rotationally movable to a limited extent about a rotational axis and wherein the interfering member is at least partially positioned inside the core of the inductor at a zero position, and is rotationally moveable about said rotational axis while remaining inside said core of said inductor in response to a user press applied to said lever or trigger mechanism, wherein the interfering member is used to interfere with the magnetic field of said inductor when the interfering member moves into the core of said inductor, and wherein a change in the inductance of the inductor is measured in response to said movement to relate the change in the measured inductance to said movement relative to the inductor, or to relate the change in the measured inductance to the position of the interfering member inside the core of the inductor.
11 . The inductive sensor of claim 10 , wherein the interfering member is a metal member or a ferrite member.
12 . The inductive sensor of claim 10 wherein the inductor is a solenoid-type inductor and comprises a plurality of windings which extend around a core with a longitudinal axis and wherein the interfering member is movable in the core along said longitudinal axis.
13 . The inductive sensor of claim 10 wherein the inductor comprises a flat coil formed on at least one side of a printed circuit board and lies in a plane, and wherein the interfering member is movable relative to the coil in a direction which is perpendicular or substantially perpendicular to said plane.
14 . The inductive sensor of claim 10 wherein said sensor is used in a joystick or thumb stick device.
15 . The inductive sensor of claim 10 wherein said structure further comprises a capacitance measurement circuit which determines if there is contact between a user and the lever or trigger mechanism and a device which uses information pertaining to such contact for calibration purposes.
16 . The inductive sensor of claim 10 wherein the inductor comprises a solenoid-type conductor with a first and second part, said first and second part being separated by a gap extending along a longitudinal direction, and wherein the inductor further comprises a plurality of windings which extend around a longitudinal core and wherein the interfering member is movable into the core at said gap in a direction which is transverse to the longitudinal axis of the core.
17 . The inductive sensor of claim 16 wherein the interfering member is selected from the following: an interfering member of irregular cross section, an interfering member with a plurality of stepped formations; and an interfering member comprising a plurality of spaced apart components.
18 . The inductive sensor of claim 10 wherein the inductance is measured using a charge transfer measurement process and wherein one end of the inductor is shorted to ground during each charging phase of the charge transfer measurement process.