Method and apparatus for sensing piston position
First Claim
1. A method of determining the positions of a piston moveable within a cylinder housing, the cylinder housing including a first end, a second end, and a side wall between the first and the second ends, the cylinder housing containing a fluid therein, comprising the steps of:
- generating electromagnetic (EM) bursts;
launching the EM bursts from a launcher coupled to the side wall at the first end of the cylinder housing, the EM bursts being launched along the side wall towards the piston, whereby the cylinder housing acts as a transmission guide for the EM bursts;
detecting reflections of the EM bursts traveling back along the side wall of the cylinder housing from the piston, the reflections due to an impedance discontinuity between the piston and the fluid;
generating a timing signal representative of the time between launching the EM bursts and detecting the reflections; and
converting at least the timing signal into a position signal representative of the position of the piston within the cylinder housing.
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Accused Products
Abstract
A system for determining the position of a piston moveable within a cylinder, or of an implement or joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter/receiver unit. The EM bursts are launched by the transmitter along a transmission guide from an end of the cylinder housing towards the piston. The transmission guide can be a dipstick mounted within the cylinder housing or the cylinder housing itself. The dipstick or cylinder housing is in electrical communication with the piston such that a surface of the piston represents an electrical impedance discontinuity which causes the EM bursts to be reflected back to the receiver. The time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel back to the receiver is determined and converted into a position signal representing the piston'"'"'s position. A compensation signal can be used to compensate the position signal for variations in a parameter of the fluid within the cylinder such as dielectric constant caused by factors such as temperature, contamination and fluid type. The compensation circuit can include a pulse level analyzer, resonance circuit, capacitance circuit, compensation dipstick, or second transmitter/receiver circuit configured to measure the piston'"'"'s position from the opposite end of the cylinder.
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Citations
25 Claims
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1. A method of determining the positions of a piston moveable within a cylinder housing, the cylinder housing including a first end, a second end, and a side wall between the first and the second ends, the cylinder housing containing a fluid therein, comprising the steps of:
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generating electromagnetic (EM) bursts; launching the EM bursts from a launcher coupled to the side wall at the first end of the cylinder housing, the EM bursts being launched along the side wall towards the piston, whereby the cylinder housing acts as a transmission guide for the EM bursts; detecting reflections of the EM bursts traveling back along the side wall of the cylinder housing from the piston, the reflections due to an impedance discontinuity between the piston and the fluid; generating a timing signal representative of the time between launching the EM bursts and detecting the reflections; and converting at least the timing signal into a position signal representative of the position of the piston within the cylinder housing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for determining the positions of a piston moveable within a cylinder housing, the cylinder housing including a first end, a second end, and a side wall between the first and the second ends, the cylinder housing containing a fluid therein, comprising:
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a generator for generating EM bursts; a transmitter coupled to the generator and to the side wall at the first end of the cylinder housing, the transmitter configured to launch the EM bursts towards the piston along the side wall, whereby the cylinder housing acts as a transmission guide for the EM bursts; a receiver coupled to the side wall at the first end of the cylinder housing and configured to detect reflections after the EM bursts are reflected by the piston to travel back towards the receiver along the side wall of the cylinder housing, the reflections due to an impedance discontinuity between the piston and the fluid; a timing circuit configured to generate a 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; 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 housing. - View Dependent Claims (15, 16, 17, 18, 20, 21, 22, 23, 24, 25)
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19. The apparatus of claim 19, 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.
Specification