Force or pressure feedback control for seismic vibrators

• US 4,519,053 A
• Filed: 10/01/1984
• Issued: 05/21/1985
• Est. Priority Date: 11/27/1981
• Status: Expired due to Term

• Current Assignee: Input/Output Incorporated
• Original Assignee: Texas Instruments, Inc.
• Inventors: Bedenbender, John W.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US06/655,999
• Time in Patent Office: 232 Days
• Field of Search: 367/190, 181/106, 181/113, 181/114, 181/119, 181/120, 181/121, 181/401, 73/663, 73/665
• US Class Current: 367/190
• CPC Class Codes: G01V 1/04 Details
• CPC Class Codes: G01V 1/155 using reciprocating masses
• CPC Class Codes: Y10S 181/401 Earth

Abstract

A seismic vibrator source having an hydraulic vibrator coupled to vibrate a ground pad is provided with one or more force transducers such as, for example, load cells, strain gauges, or piezoelectric elements for measuring the force applied to the earth. Signals indicative of the pressure force are applied to a controller for the hydraulic vibrator to adjust control signals to prevent decoupling of the ground pad from the earth during ground seismic operations.

Claims

1. A seismic vibrator source having a reaction mass comprising:

(a) a vibrator means for imparting acoustic energy into the earth, including a baseplate structure for contacting the earth connected to the reaction mass;

(b) a drive means for vibrating the vibrator means;

(c) a force measuring transducer means integral with said vibrator means and operative responsive to the vibrator means to produce electrical signals directly representative of the force applied to the earth, the force including the weight of the reaction mass and the weight of the baseplate structure mass, to thereby accurately represent a decoupling condition for controlling the drive means; and

(d) comparator means for comparing the electrical signals representative of the force with a predetermined representative value for maintaining the force at that corresponding to that of the predetermined representative value.

2. A seismic vibrator source according to claim 1 wherein said transducer means comprises at least one load cell measuring the force applied to the earth.

3. A seismic vibrator source according to claim 1 wherein said transducer means comprises a plurality of piezoelectric transducers.

4. A seismic vibrator source comprising:

(a) a ground pad for imparting acoustic energy into the earth;

(b) a hydraulic vibrator means including a support frame connected to the ground pad, a mass, a cylinder supporting said mass in the support frame, a piston dividing the cylinder into an upper chamber and a lower chamber, and a piston rod interconnecting the piston to the ground pad;

(c) a hydraulic drive means operatively coupled to the hydraulic vibrator for reciprocating the cylinder-supported mass to vibrate the ground pad, said hydraulic drive means including a servo valve for regulating fluid into the cylinder of the hydraulic vibrator means;

(d) a force measuring transducer means integral with said vibrator means and operatively responsive to the seismic source action for producing electrical signals directly representative of the force applied to the earth, the force including the weight of the reaction mass, the weight of the ground pad mass and the weight of the support frame to thereby accurately represent a decoupling condition for controlling the drive means; and

(e) controller means including a pilot signal source and a comparator for comparing the transducer means output with the output of the pilot signal source for producing a signal for controlling the hydraulic means to maintain the force applied to the earth at a value corresponding to the output of the pilot signal source.