US6005395A — Method and apparatus for sensing piston position

Claim 1

Independent Claim 120 words

A method of determining the position of a piston moveable within a cylinder housing, the cylinder housing enclosing a cavity filled with a fluid, comprising the steps of: generating real-time electromagnetic (EM) bursts; launching the real-time EM bursts towards the piston through the fluid within the cavity in the cylinder housing; detecting real-time reflections of the EM bursts from the piston; generating an equivalent-time timing signal representative of the time between launching the EM bursts and detecting the reflections, the timing signal being of a slower time scale than that of the real-time EM bursts and reflections; and converting at least the equivalent-time timing signal into a position signal representative of the position of the piston within the cylinder housing.

Claim 2

Independent Claim 120 words

A method of determining the position of a piston moveable within a cylinder housing, the cylinder housing enclosing a cavity filled with a fluid, comprising the steps of: generating real-time electromagnetic (EM) bursts; launching the real-time EM bursts towards the piston through the fluid within the cavity in the cylinder housing; detecting real-time reflections of the EM bursts from the piston; generating an equivalent-time timing signal representative of the time between launching the EM bursts and detecting the reflections, the timing signal being of a slower time scale than that of the real-time EM bursts and reflections; and converting at least the equivalent-time timing signal into a position signal representative of the position of the piston within the cylinder housing.

Claim 3

Dependent Claim 12 words

The method of claim 1, wherein the EM bursts include ultra-wideband pulses.

Claim 4

Dependent Claim 16 words

The method of claim 1, wherein the EM bursts include pulses having a carrier frequency component.

Claim 5

Dependent Claim 56 words

The method of claim 1, wherein the cylinder housing includes a first end, a second end and a side wall between the first and the second ends, and the steps of launching the EM bursts and detecting the reflections are performed by a transmitter and a receiver coupled to the first end of the cylinder housing.

Claim 6

Dependent Claim 19 words

The method of claim 1, further comprising the steps of integrating and filtering the reflections of the EM bursts.

Claim 7

Dependent Claim 45 words

The method of claim 1, further comprising the step of generating a compensation signal responsive to a parameter of the fluid within the cavity in the cylinder housing, and the converting step includes converting at least the timing and compensation signals into the position signal.

Claim 8

Dependent Claim 18 words

The method of claim 6, wherein the compensation signal is responsive to the dielectric constant of the fluid.

Claim 9

Dependent Claim 36 words

The method of claim 7, wherein the step of generating a compensation signal includes applying an excitation signal at varying frequencies to a body having a cavity filled with the fluid and determining the resonance frequency.

Claim 10

Dependent Claim 29 words

The method of claim 7, wherein the step of generating a compensation signal includes measuring the capacitance of a pair of conductors having a layer of the fluid therebetween.

Claim 11

Dependent Claim 29 words

The method of claim 7, wherein the step of generating a compensation signal includes measuring the electrical impedance discontinuity between an end of a compensation dipstick and the fluid.

Claim 12

Independent Claim 173 words

An apparatus for determining the position of a piston moveable within a cylinder housing, the cylinder housing enclosing a cavity filled with a fluid, comprising: a generator for generating real-time EM bursts; a transmitter coupled to the generator and to the cylinder housing, the transmitter configured to launch the real-time EM bursts towards the piston through the fluid within the cavity in the cylinder housing; a receiver coupled to the cylinder housing and configured to detect real-time reflections after the EM bursts are reflected by the piston towards the receiver; a timing circuit configured to generate an equivalent-time timing signal representative of the time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel from the piston to the receiver, the timing signal being of a slower time scale than that of the EM bursts and reflections; and a conversion circuit configured to convert at least the equivalent-time timing signal into a position signal representative of the position of the piston within the cylinder housing.

Claim 13

Independent Claim 173 words

An apparatus for determining the position of a piston moveable within a cylinder housing, the cylinder housing enclosing a cavity filled with a fluid, comprising: a generator for generating real-time EM bursts; a transmitter coupled to the generator and to the cylinder housing, the transmitter configured to launch the real-time EM bursts towards the piston through the fluid within the cavity in the cylinder housing; a receiver coupled to the cylinder housing and configured to detect real-time reflections after the EM bursts are reflected by the piston towards the receiver; a timing circuit configured to generate an equivalent-time timing signal representative of the time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel from the piston to the receiver, the timing signal being of a slower time scale than that of the EM bursts and reflections; and a conversion circuit configured to convert at least the equivalent-time timing signal into a position signal representative of the position of the piston within the cylinder housing.

Claim 14

Dependent Claim 12 words

The apparatus of claim 11, wherein the EM bursts include ultra-wideband pulses.

Claim 15

Dependent Claim 16 words

The apparatus of claim 11, wherein the EM bursts include pulses having a carrier frequency component.

Claim 16

Dependent Claim 43 words

The apparatus of claim 11, wherein the cylinder housing includes a first end, a second end and a side wall between the first and the second ends, and the transmitter and the receiver are coupled to the first end of the cylinder housing.

Claim 17

Dependent Claim 45 words

The apparatus of claim 11, further comprising: an antenna assembly electrically coupled to the transmitter and the receiver, the antenna assembly configured to focus the EM bursts, to launch the EM bursts with the transmitter, and to detect the reflected EM bursts with the receiver.

Claim 18

Dependent Claim 117 words

The apparatus of Claim 11, further comprising: a directional sampler circuit having a first real-time port for receiving the EM bursts from the generator, a second real-time port coupled to the first port for sending the EM bursts to the transmitter and for receiving the reflections, a third port coupled to the first port and isolated from the second port for providing an equivalent-time representation of the EM bursts, and a fourth port coupled to the second port and isolated from the first port for providing an equivalent-time representation of the reflections, wherein the equivalent-time representations of the EM bursts from the third port and the reflections from the fourth port are applied to the timing circuit.

Claim 19

Dependent Claim 51 words

The apparatus of claim 16, wherein the timing circuit includes a first comparator circuit coupled to the third port, a second comparator circuit coupled to the fourth port, and a set-reset flip-flop circuit set by the equivalent-time representation of the EM bursts and reset by the equivalent-time representation of the reflections.

Claim 20

Dependent Claim 49 words

The apparatus of claim 11, further comprising a compensation circuit configured to generate a compensation signal responsive to a parameter of the fluid within the cavity in the cylinder housing, wherein the conversion circuit is configured to convert at least the timing and compensation signals into the position signal.

Claim 21

Dependent Claim 18 words

The apparatus of claim 18, wherein the compensation signal is responsive to the dielectric constant of the fluid.

Claim 22

Dependent Claim 35 words

The apparatus of claim 19, wherein the compensation circuit is configured to apply an excitation signal at varying frequencies to a body having a cavity filled with the fluid and to determine the resonance frequency.

Claim 23

Dependent Claim 21 words

The apparatus of claim 19, wherein the compensation circuit includes a pair of conductors having a layer of the fluid therebetween.

Claim 24

Dependent Claim 87 words

The apparatus of claim 19, wherein the compensation circuit includes: a compensation dipstick; a second generator coupled to the compensation dipstick and configured to generate second EM bursts; a second transmitter coupled to the second generator and to the cylinder housing, the second transmitter configured to launch the second EM bursts along the compensation dipstick towards the piston; and a second receiver coupled to the cylinder housing and configured to detect second reflections after the second EM bursts are reflected by the piston towards the second receiver.

Claim 25

Dependent Claim 194 words

An electrohydraulic control system for controlling the position of an implement, the implement having at least one joint which is moved by extending or retracting at least one cylinder coupled to the joint, comprising: an input device configured to generate command signals representative of a commanded position of the implement; a source of pressurized hydraulic fluid; a valve assembly coupled between the cylinder and the source, the valve assembly configured to control the flow of hydraulic fluid between the cylinder and the source in response to control signals; a micropower impulse radar (MIR) sensor system coupled to the cylinder and configured to sense movement of the cylinder and to generate a position signal representative of the position of the implement, the MIR sensor system being configured to sense the movement using time domain reflectometry based on real-time signals traveling through the hydraulic fluid within a cavity of the cylinder; and a control circuit coupled to the input device, the valve assembly, and the MIR sensor system, the control circuit configured to generate the control signals based upon the command signals and the position signal and to apply the control signals to the valve assembly.

Claim 26

Dependent Claim 194 words

An electrohydraulic control system for controlling the position of an implement, the implement having at least one joint which is moved by extending or retracting at least one cylinder coupled to the joint, comprising: an input device configured to generate command signals representative of a commanded position of the implement; a source of pressurized hydraulic fluid; a valve assembly coupled between the cylinder and the source, the valve assembly configured to control the flow of hydraulic fluid between the cylinder and the source in response to control signals; a micropower impulse radar (MIR) sensor system coupled to the cylinder and configured to sense movement of the cylinder and to generate a position signal representative of the position of the implement, the MIR sensor system being configured to sense the movement using time domain reflectometry based on real-time signals traveling through the hydraulic fluid within a cavity of the cylinder; and a control circuit coupled to the input device, the valve assembly, and the MIR sensor system, the control circuit configured to generate the control signals based upon the command signals and the position signal and to apply the control signals to the valve assembly.

Claim 27

Dependent Claim 18 words

The system of claim 23, wherein the implement includes an agricultural header mounted to an agricultural harvesting vehicle.

Claim 28

Dependent Claim 124 words

The system of claim 23, wherein the MIR sensor system includes: a generator for generating EM bursts; a transmitter coupled to the generator, the transmitter configured to launch EM bursts through a cavity in the cylinder filled with a fluid; a receiver configured to detect reflections after the EM bursts are reflected by a piston in the cylinder towards the receiver; a timing circuit configured to generate a time signal representative of the time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel from the piston to the receiver; and a conversion circuit configured to convert at least the timing signal into a position signal representative of the position of the piston within the cylinder.

Claim 29

Dependent Claim 45 words

The system of claim 25, further comprising: an antenna assembly electrically coupled to the transmitter and the receiver, the antenna assembly configured to focus the EM bursts, to launch the EM bursts with the transmitter, and to detect the reflected EM bursts with the receiver.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2002-12-20	2003-06-21	2003-12-21	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2006-12-20	2007-06-21	2007-12-21	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2010-12-20	2011-06-21	2011-12-21	$7700.00	Window Closed / Lapsed

Method and apparatus for sensing piston position

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