Linear position sensor using a coaxial resonant cavity
AssigneeCaterpillar Inc.
InventorsAli A. Bitar, Charles W. Bowman, Denny E. Morgan
Life of this patent
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Abstract
An apparatus (102) is for detecting the linear extension (position), velocity and acceleration of a hydraulic cylinder (108). The hydraulic cylinder (108) defines a variable length coaxial resonant cavity (112). Under the control of a controller (228), an RF transmitting section (114) and an RF receiving section (116) are used to determine the resonant frequency of the cavity. The resonant frequency of the cavity (112) is determined by comparing a received signal with a threshold and detecting slope intercept conditions.
Claims6
A method for detecting a linear position of a piston (104) and a piston rod (106) being movable within a housing (110) of a hydraulic cylinder (108), including the steps of:
- producing an electromagnetic signal having a frequency varying between minimum and maximum values;
- delivering said electromagnetic signal into said hydraulic cylinder (108);
- receiving electromagnetic wave signals from said hydraulic cylinder (108);
- detecting a first positive slope intercept condition;
- tracking the frequency of said first positive slope intercept condition and responsively producing a first frequency signal;
- detecting a first negative slope intercept condition;
- tracking the frequency of said first negative slope intercept condition and responsively producing a second frequency signal;
- detecting a second positive slope intercept condition;
- tracking the frequency of said second positive slope intercept condition and responsively producing a third frequency signal;
- detecting a second negative signal slope intercept condition;
- tracking the frequency of said second negative slope intercept condition and responsively producing a fourth frequency signal;
- receiving said frequency signals and responsively determining the position, velocity and acceleration of said piston and piston rod (104,106).
An apparatus (102) for detecting a linear position, a linear velocity, and a linear acceleration of a piston (104) and a piston rod (106) being movable within a housing (110) of a hydraulic cylinder (108), comprising:
- means (14) for producing an electromagnetic signal and delivering said electromagnetic signal into hydraulic cylinder (108), said electromagnetic signal having a frequency varying between predetermined minimum and maximum values;
- means (116) for sensing an electromagnetic wave signal within said hydraulic cylinder (108), detecting first and second positive slope intercept conditions and first and second negative slope conditions of said electromagnetic wave signal and producing first and third and second and fourth frequency signals in response to the frequency of said electromagnetic signal corresponding to said first and second positive slope conditions and said first and second negative slope conditions, respectively;
- and
- means (118) for receiving said first, second, third, and fourth frequency signals and responsively determining the position, velocity, and acceleration of said piston (104) and piston rod (106).
Dependencies are inferred from the claim text.