Linear position sensor having coaxial or parallel primary and secondary windings

• US 5,210,490 A
• Filed: 07/29/1991
• Issued: 05/11/1993
• Est. Priority Date: 01/11/1989
• Status: Expired due to Term

• Current Assignee: Uusi LLC (Nartron Corporation)
• Original Assignee: Nartron Corporation
• Inventors: Munch, Carl A., Cooper, Stephen R. W., Rymut, Michael J.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US07/737,389
• Time in Patent Office: 652 Days
• Field of Search: 324/207.11, 324/207.15, 324/207.16, 324/207.17, 324/207.22, 324/207.24, 324/207.12, 324/207.13, 324/207.25, 324/207.13, 340/870.31, 340/870.32, 340/870.33, 340/870.34, 340/870.35, 340/870.36, 336/30, 336/45, 336/73, 336/77, 336/84 R, 336/130, 336/132, 336/133, 336/136
• US Class Current: 324/207.17
• CPC Class Codes: B60G 17/01933 Velocity, e.g. relative velocity-displacement sensors
• CPC Class Codes: B60G 2204/111 on pneumatic springs
• CPC Class Codes: B60G 2204/112 on dampers, e.g. fluid dampers
• CPC Class Codes: B60G 2400/202 Piston speed; Relative velocity between vehicle body and wheel
• CPC Class Codes: B60G 2400/25 Stroke; Height; Displacement
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2401/17 Magnetic/Electromagnetic
• CPC Class Codes: G01D 5/2046 by a movable ferromagnetic element, e.g. a core
• CPC Class Codes: G01D 5/2053 by a movable non-ferromagnetic conductive element

Abstract

A position sensing device including two spaced conductive coils constituting a primary and secondary winding of a transformer. A coupling member is mounted to a moveable object such as an automobile steering mechanism and moves relative the primary and secondary windings. This movement adjusts or alters the transformer coupling between the primary and the secondary and produces a variable output signal which can be correlated through use of appropriate circuitry to the position of the moveable member. Two alternate designs are disclosed. In a first design, the transformer primary and secondary are disposed side-by-side and the coupling member slips over the primary and secondary for relative linear movement. In a second design, the primary and secondary are disposed one within the other and the coupling member fits within a gap between the primary and secondary. A control system for multiple position sensors includes circuitry for activating multiple sensors as well as monitoring return signals from multiple signals. Such a control system can interface other computers within the vehicle such as body control and engine control computers.

Claims

1. Position sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member coupled to a first of said moveable members and including a first multi-turn conductor would about a field producing member axis and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member fixed with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a cylindrical shielding member connected to a second of the moveable members for movement with the second moveable member and positioned generally co-axial with one member of the field producing and field responsive members to overlap a portion of said one member that varies with the relative position of the moveable members to alter the response of the field responsive member as the moveable members move relative to each other and thereby change the signal at the output of the field responsive member;

d) exciter means coupled to the input for energizing the field producing member; and

e) circuit means coupled to the output from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.

2. The apparatus of claim 1 wherein said first and second multi-turn conductors are etched onto the field producing and field responsive members respectively.

3. The apparatus of claim 1 wherein said first and second multi-turn conductors are scribed onto the field producing and field responsive members respectively.

4. The apparatus of claim 1 wherein said first and second multi-turn conductors are deposited onto the field producing and field responsive members respectively.

5. The apparatus of claim 1 wherein said field responsive members are oval in cross section.

6. The apparatus of claim 1 wherein said field responsive members are polygonal in cross section.

7. The apparatus of claim 1 further comprising a cylindrical case that at least partially encloses the field producing, field responsive and shielding members.

8. The apparatus of claim 7 wherein the cylindrical case is electrically conductive to increase coupling between the field producing and field responsive members, said apparatus producing a signal on the secondary that increases as the shielding member is withdrawn and decreases as the shielding member is inserted into the cylindrical case.

9. The apparatus of claim 8 wherein the cylindrical case is highly magnetically permeable to provide shielding from the effects of magnetic field sources.

10. The apparatus of claim 7 wherein the case supports a shorted electric coil having a controlled turn density along its length and further wherein the case is constructed from a material having a low magnetic permeability.

11. Position sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member coupled to a first of said moveable members and including a first multi-turn conductor wound about a field producing member axis and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member fixed with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a core member connected to a second of the moveable members for movement with the second moveable member;

said core member mounted for movement within one of said field producing and field responsive members to alter the response of the field responsive member as the moveable members move relative to each other and thereby change the signal at the output of the field responsive member;

d) exciter means coupled to the input for energizing the field producing member; and

e) circuit means coupled to the output from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.

12. Movement sensing apparatus for monitoring a relative position and velocity between two relatively moveable members comprising:

a) an elongated field producing member coupled to a first of said moveable members and including a first multi-turn conductor wound about a field producing member axis having a first controlled turn density, and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member fixed with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis having a second controlled turn density, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a coupling member connected to a second of the moveable members for movement with the second moveable member and positioned relative the field producing and field responsive members to alter the response of the field responsive member as the moveable members move relative to each other and thereby change the signal at the output of the field responsive member;

d) exciter means coupled to the input for energizing the field producing member; and

e) circuit means coupled to the output from the field responsive member to correlate changes in the output signal with relative position and velocity of the moveable members, wherein the velocity is obtained by differentiating a position signal output.

13. The apparatus of claim 12 wherein said coupling member comprises a conductive cylinder with semicircular cross-section.

14. The apparatus of claim 12 wherein said coupling member comprises a conductive spring.

15. Sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member coupled to a first of said moveable members and including a first multi-turn conductor wound about a field producing member axis and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member fixed with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a coupling member connected to a second of the moveable members for movement with the second moveable member and positioned relative the field producing and field responsive members to alter the response of the field responsive member as the moveable members move relative to each other and thereby change the signal at the output of the field responsive member; and

d) a control module spaced from the elongated field producing and field responsive members and electrically coupled to the field producing and field responsive members by cabling;

said control module including;

i) exciter means coupled via said cabling to the input for energizing the field producing member; and

ii) circuit means coupled via said cabling to the output from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.

16. The apparatus of claim 15 wherein the exciter means and circuit means form part of an application specific integrated circuit.

17. The sensing apparatus of claim 15 additionally comprising an accelerometer for monitoring acceleration of one of the two relatively moveable members and wherein the control module comprises means for energizing the accelerometer and monitoring acceleration signals from the accelerometer.

18. A control system for monitoring relative positions between pairs of relatively moveable members comprising:

a) a plurality of position sensors with each including;

i) an elongated field producing member coupled to a first of moveable member of a given pair and including a first multi-turn conductor wound about a field producing member axis having a first controlled turn density, and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

ii) an elongated field responsive member fixed with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis having a second controlled turn density, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

iii) a coupling member connected to a second of the moveable members for movement with the second moveable member and positioned relative the field producing and field responsive members to alter the response of the field responsive member as the moveable members move relative to each other and thereby change the signal at the output of the field responsive member; and

b) control circuitry including exciter means coupleable to the input of each position sensor for energizing the field producing member and monitoring means coupleable to the output from the field responsive member of each position sensor to correlate changes in the output signal with relative movement of the pairs of moveable members.

19. The control system of claim 18 wherein the control circuitry comprises:

a) a microprocessor having a control algorithm for activating the elongated field producing member of the plurality of position sensors;

b) multiplexor means for coupling electric signals to and from the position sensors; and

c) interface means for routing signals indicative of said relative positions to other circuitry.

20. Position sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member with a first core coupled to a first of said moveable members and including a first multi-turn conductor wound about the first core situated along a member axis having an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member with a second core coupled to a first of said moveable members and including a second multi-turn conductor wound about the second core situated along a second member axis, said elongated field responsive member oriented in a side by side, generally parallel orientation to the enlongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a conductive member coupled to a second moveable member which slides over one or both the field producing and field responsive members during motion of the second moveable member with respect to the first moveable member to alter the response of the field responsive member as a result of relative motion between the moving members;

d) exciter means coupled to the input for energizing the field producing member; and

e) circuit means coupled to the input from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.

21. The apparatus of claim 20 wherein said coupling member comprises a conductive compressible bellows.

22. The apparatus of claim 20 wherein said coupling member comprises a conductive spring.

23. Position sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member including a core coupled to a first of said moveable members and further including a first multi-turn conductor wound about said core coupled to a second of said moveable members and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member coupled to the second of said moveable members for movement with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) exciter means coupled to the input for energizing the field producing member; and

d) circuit means coupled to the output from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.

24. The apparatus of claim 23 further including a coupling member for movement with the core and connected to said first moveable member that surrounds at least one of said first and second multi-turn conductors.

25. A position sensor, comprising:

a) a primary winding having a first core and a conductor wound around said first core including a multiplicity of turns spaced along at least a portion of a length of said first core;

b) a secondary winding having a second core and a second conductor wound around said second core including a multiplicity of turns space along at least a portion of a length of said second core;

c) said secondary winding positioned in a spaced, generally co-axial transformer coupling relationship with the primary winding with both said primary and secondary windings attached to a first of two relatively positioned members; and

d) coupling means moveable with a second of said two relatively positioned members to overlie at least one of the primary and secondary windings and vary the transformer coupling between said windings as the two relatively positioned members move with respect to each other;

e) said primary and secondary windings having controlled turn densities along both their length to provide an output signal from the secondary winding that is functionally dependent on the relative position of the two relatively positioned members and said first and second cores comprise magnetic material, the content of magnetic material within each core varying along a length of each winding.

26. The sensor of claim 25 wherein the first and second cores have controlled diameter to adjust the content of magnetic material along their length.

27. The sensor of claim 25 wherein the coupling means comprises a ring-shaped permanent magnet and:

a) wherein the flux linkage between the permanent magnet and the secondary winding increases linearly with the position of the magnet along the secondary winding;

b) wherein the product of the a.c. flux linkage from the primary winding to the coupler, and the coupler to the secondary winding, increases linearly with the position of the magnet along the seconding winding; and

c) said sensor additionally including circuitry for monitoring an output from the secondary winding and low pass filtering this output to obtain a velocity dependent signal and high pass filtering followed by amplitude demodulation to obtain a position dependent signal.

28. Position sensing apparatus for monitoring a relative position between two relatively moveable members comprising:

a) an elongated field producing member including a core coupled to a first of said moveable members and further including a first multi-turn conductor wound about and coupled to said core and an input for energizing the first multi-turn conductor to produce an electromagnetic field in the vicinity of the elongated field producing member;

b) an elongated field responsive member coupled to the second of said moveable members for movement with respect to the elongated field producing member including a second multi-turn conductor wound about a field responsive member axis, said elongated field responsive member oriented in side by side, generally parallel orientation to the elongated field producing member along a length of the elongated field producing member, and having an output for providing an output signal in response to the electromagnetic field produced by the field producing member;

c) a coupling member for movement with the core and coupled with said first moveable member, said coupling member surrounding at least one of said first and second multi-turn conductors;

d) exciter means coupled to the input for energizing the field producing member; and

d) circuit means coupled to the output from the field responsive member to correlate changes in the output signal with relative movement of the moveable members.