Claims
- 1. A control system for controlling operation of a core drilling device, the core drilling device including a drive system to advance and retract a drill string carrying a drill bit, the control system comprising:a first sensor in communication with the core drilling device, the first sensor being operative to sense a weight on the drill bit during a pull-down mode of operation, and to generate a corresponding first signal; a second sensor in communication with the core drilling device, the second sensor being operative to sense the weight on the drill bit during a hold-back mode of operation, and to generate a corresponding second signal; and a controller in electrical communication with the respective sensors and with the drive system, the controller being programmed with a preselected maximum value for the weight on the drill bit, wherein the controller is responsive to one of the signals having a value above the respective maximum value to control the drive system to reduce the rate of penetration of the drill bit.
- 2. The control system of claim 1, wherein the first sensor comprises a pressure transducer.
- 3. The control system of claim 1, wherein the second sensor comprises a load cell.
- 4. The control system of claim 1, wherein the controller is responsive to the respective signals having values corresponding to a weight on bit below the maximum value to control the drive system to increase the rate of penetration of the drill bit.
- 5. The control system of claim 1, wherein the drive system includes a hydraulic circuit comprising one or more hydraulic motors connected to the drill string, the hydraulic circuit further including a servo valve, the controller being electrically connected for communication with the servo valve to control the drive system.
- 6. The control system of claim 1, wherein the controller comprises a programmable logic controller.
- 7. The control system of claim 1, further including a third sensor that is operative to sense the rate of penetration of the drill string and to generate a corresponding signal, and wherein the controller is responsive to receipt of signals from the respective sensors that each have a value below the respective maximum values to control the drive system to increase the rate of penetration.
- 8. The control system of claim 1 and further including an input device to allow an operator to input a weight-on-bit maximum value, and wherein the controller is electrically connected to the input device and is responsive to input of a new value to modify the maximum value.
- 9. A method of controlling weight on a drill bit, the drill bit being carried by a drill string and driven by a drilling device, the method comprising:providing first and second sensors for sensing the weight on the drill bit, wherein the first sensor is operative to sense the weight on bit during a pull-down mode of operation and to generate a corresponding first signal, and wherein the second sensor is operative to sense the weight on bit during a hold-back mode of operation and to generate a corresponding second signal; monitoring the first sensor during the pull-down mode; monitoring the second sensor during the hold-back mode; determining whether the sensed weight on bit exceeds a preselected maximum value for the weight on the drill bit; and reducing the rate of penetration of the drill string if the sensed weight exceeds the preselected maximum value.
- 10. The method of claim 9 and further including the steps of:providing a sensor that is operative to sense the rate of penetration of the drill string; determining whether the sensed rate of penetration is below a preselected threshold value for the rate of penetration; determining whether the weight on bit is below the preselected maximum value, if the sensed rate of penetration is below the preselected threshold value; and increasing the rate of penetration if the weight on bit is below the preselected maximum value.
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part application of U.S. Patent application Ser. No. 09/017,616, filed on Feb. 2, 1998, now abandoned, which is a continuation-in-part application of U.S. Patent application Ser. No. 08/567,184, filed on Dec. 12, 1995, and now U.S. Pat. No. 5,794,723, issued on Aug. 18, 1998.
US Referenced Citations (43)
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
09/017616 |
Feb 1998 |
US |
Child |
09/209821 |
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US |
Parent |
08/567184 |
Dec 1995 |
US |
Child |
09/017616 |
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US |