Seismic vibrator control system
AssigneeExxon Production Research Company
InventorJoseph F. Mifsud
Life of this patent
Estimating the term…
Abstract
This invention is a control system for a hydraulic vibrator that permits the injection into the ground of seismic signals having pseudo-random code patterns or other broad band signals. Feedback for controlling vibrator operation is taken from the coupling plate. At low frequencies, the feedback is proportional to coupling plate position and at higher frequencies, the feedback is proportional to the coupling plate velocity.
Claims31
An improved apparatus for controlling the operation of seismic vibrator, said vibrator including a coupling plate, the movement of which is responsive to an electrical input signal, the improvement comprising a feedback loop which includes:
- means for generating an electrical feedback signal which includes a transducer coupled to said coupling plate, said feedback signal having an amplitude which varies instantaneously with coupling plate motion;
- summing means having said electrical input signal connected to a first input terminal thereto and said feedback signal having an amplitude which varies instantaneously with coupling plate motion connected to a second input terminal thereto;
- and
- phase compensator means connected in series circuit relation within said feedback loop.
An improved apparatus for controlling the operation of a seismic vibrator, said vibrator comprising hydraulic actuator means including a piston and cylinder, a coupling plate connected to the lower end of said piston, and electrohydraulic means including a slave spool for generating a reciprocating movement of said piston responsive to an electrical input signal, the improvement comprising a feedback loop which includes
- means for generating an electrical feedback signal which includes a transducer coupled to said coupling plate, said feedback signal having an amplitude which varies instantaneously with coupling plate motion;
- summing means having said electrical input signal connected to a first input terminal thereto and said feedback signal having an amplitude which varies instantaneously with coupling plate motion connected to a second input terminal thereto;
- and
- phase compensator means in series circuit relation within said feedback loop.
An improved apparatus for controlling the operation of a seismic vibrator, said vibrator comprising hydraulic actuator means including a piston and cylinder, a coupling plate connected to the lower end of said piston, and electrohydraulic means including a slave spool for generating reciprocating movement of said piston responsive to an electrical input signal, the improvement comprising a feedback loop which includes:
- means for generating a first electrical feedback signal having an amplitude proportional to the velocity of said coupling plate over a first frequency range, said first frequency range having a lower limit not lower than the minimum frequency at which a velocity feedback signal is of sufficient amplitude to control the vibrator operation;
- means for generating a second electrical feedback signal having an amplitude proportional to the displacement of said coupling plate over a second frequency range, said second frequency range having an upper limit equal to about the lower limit of said first frequency range;
- summing means having said first and second electrical feedback signals and said electrical input signal connected to input terminals thereof;
- and
- phase compensator means connected in series circuit relation within said feedback loop.
In a method for injecting a seismic disturbance into the earth by means of a vibrator which includes a coupling plate the motion of which is responsive to an electrical input signal and at least one feedback loop is utilized to control coupling plate motion, the improvement comprising:
- generating an electrical feedback signal from a transducer coupled to said coupling plate having an amplitude which varies instantaneously with coupling plate motion;
- summing said electrical feedback signal having an amplitude proportional to coupling plate motion with said electrical input signal to generate a drive signal for said vibrator;
- and
- phase shifting said drive signal to compensate for phase shift within said vibrator.
In a method for controlling the operation of a hydraulic vibrator comprising a hydraulic actuator means including a piston and cylinder, a coupling plate connected to the lower end of said piston, and electrohydraulic means including a slave spool for generating motion of said piston responsive to an electrical input signal, wherein at least one feedback signal is utilized to control coupling plate motion, the improvement comprising:
- generating an electrical feedback signal from a transducer coupled to said coupling plate having an amplitude which varies instantaneously with coupling plate motion;
- summing said electrical feedback signal having an amplitude which varies instantaneously with coupling plate motion with said electrical input signal to generate a drive signal for said vibrator, and
- phase shifting said drive signal to compensate for phase shift within said vibrator.
In a method for controlling the operation of a hydraulic vibrator comprising a hydraulic actuator means including a piston and cylinder, a coupling plate connected to the lower end of said piston, an electrohydraulic means including a slave spool for generating motion of said piston responsive to an electrical input signal, wherein at least one feedback loop is utilized to control coupling plate motion, the improvement comprising:
- generating an electrical feedback signal having an amplitude proportional to the velocity of said coupling plate over a first frequency range having a lower limit not lower than the minimum frequency at which said velocity feedback signal has sufficient amplitude for controlling the vibrator;
- generating an electrical feedback signal having an amplitude proportional to the displacement of said coupling plate over a second frequency range having an upper limit at about the frequency to the lower limit of said first frequency range;
- summing said electrical feedback signal having an amplitude proportional to the velocity of said coupling plate and said electrical feedback signal having an amplitude proportional to the displacement of said coupling plate with said electrical input signal to generate a drive signal for said vibrator;
- and
- phase shifting said drive signal to compensate for phase shift within said vibrator.
Dependencies are inferred from the claim text.