Pipeline mandrel positioning control system

• US 6,354,123 B1
• Filed: 01/12/2000
• Issued: 03/12/2002
• Est. Priority Date: 04/28/1999
• Status: Expired due to Term

• Current Assignee: Crc-Evans Automatic Welding Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Crc-Evans Automatic Welding Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Madala, Sridhar, Rajagopalan, Shankar T.
• Primary Examiner(s): TOLAN, EDWARD THOMAS
• Application Number:
  US09/481,900
• Time in Patent Office: 790 Days
• Field of Search: 72/172, 72/201, 72/211, 72/310.1, 72/310.4, 72/310.5, 72/310.6, 723/69, 723/700.1, 405/154.1, 405/159, 405/160, 405/184.4, 340/825.69, 340/825.72, 340/853.3, 340/853.8, 340/854.1, 340/854.6, 340/855.5
• US Class Current: 72/31.01
• CPC Class Codes: F16L 55/48 Indicating the position of the pig or mole in the pipe or conduit

Abstract

A method and apparatus is provided for automated control and positioning of a mandrel within a pipe during bending operations. Position detection is accomplished by means of a low frequency electromagnetic signal transmission from a coil placed in close proximity parallel to the pipe outer surface. This signal is detected by a pair of orthogonal receiving coils mounted on the mandrel in close proximity to the pipe inner surface. The phases of the received signals with respect to the transmitted signal and the ratio of the amplitudes of the two received signals is used to estimate the relative position of the transmitter and the receivers. Control of the mandrel along with transmission of reference phase information is accomplished via a high frequency direct sequence spread spectrum radio link between a computer console outside the pipe mounted on the bender and a computer unit mounted inside the pipe on the mandrel.

Claims

1. An apparatus for controlling the position of a mandrel within a pipe comprising:

an exterior control unit including a low frequency signal generator;

a transmit coil, and a first radio frequency transceiver;

said transmit coil being positioned proximate to the outside surface of a wall of said pipe and having a longitudinal axis oriented parallel to the longitudinal axis of the pipe;

said signal generator being operably connected to said transmit coil to transmit low frequency electromagnetic signals through said wall;

said first radio frequency transceiver being a direct sequence spread spectrum radio frequency modem transmitting a radio frequency signal;

an interior control unit mounted on said mandrel and including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil having a longitudinal axis oriented parallel to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second receive coil having a longitudinal axis oriented perpendicular to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second radio frequency transceiver adapted to receive said radio frequency signal containing information regarding the phase of said low frequency signal; and

a digital signal processor adapted to compare the phase of signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver.

2. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 1, wherein said second radio frequency transceiver is a direct sequence spread spectrum radio frequency modem.

3. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 1, wherein said radio frequency signal has a frequency of about 2.4 GHz.

4. An apparatus for controlling the position of a mandrel within a pipe comprising:

an exterior control unit including a low frequency signal generator;

a transmit coil, and a first radio frequency transceiver;

said transmit coil being positioned proximate to the outside surface of a wall of said pipe and having a longitudinal axis oriented parallel to the longitudinal axis of the pipe;

said signal generator being operably connected to said transmit coil to transmit low frequency electromagnetic signals through said wall, said low frequency electromagnetic signals having a frequency within the range from about 21 Hz to about 24 Hz;

said first radio frequency transceiver transmitting a radio frequency signal;

an interior control unit mounted on said mandrel and including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil having a longitudinal axis oriented parallel to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second receive coil having a longitudinal axis oriented perpendicular to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second radio frequency transceiver adapted to receive said radio frequency signal containing information regarding the phase of said low frequency signal; and

a digital signal processor adapted to compare the phase of signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver.

5. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 4, wherein said low frequency electromagnetic signals have a frequency within the range from about 22 Hz to about 23 Hz.

6. An apparatus for controlling the position of a mandrel within a pipe comprising:

an exterior control unit including a low frequency signal generator;

a transmit coil, and a first radio frequency transceiver;

said transmit coil being positioned proximate to the outside surface of a wall of said pipe and having a longitudinal axis oriented parallel to the longitudinal axis of the pipe;

said signal generator being operably connected to said transmit coil to transmit low frequency electromagnetic signals through said wall;

said first radio frequency transceiver transmitting a radio frequency signal;

an interior control unit mounted on said mandrel and including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil having a longitudinal axis oriented parallel to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second receive coil having a longitudinal axis oriented perpendicular to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said first and second receive coils being mounted such that said second receive coil is longitudinally centered with respect to said first receive coil;

said second radio frequency transceiver adapted to receive said radio frequency signal containing information regarding the phase of said low frequency signal; and

a digital signal processor adapted to compare the phase of signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver.

7. An apparatus for controlling the position of a mandrel within a pipe comprising:

an exterior control unit including a low frequency signal generator;

a transmit coil, and a first radio frequency transceiver;

said transmit coil being positioned proximate to the outside surface of a wall of said pipe and having a longitudinal axis oriented parallel to the longitudinal axis of the pipe;

said signal generator being operably connected to said transmit coil to transmit low frequency electromagnetic signals through said wall;

said first radio frequency transceiver transmitting a radio frequency signal;

an interior control unit mounted on said mandrel and including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil having a longitudinal axis oriented parallel to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second receive coil having a longitudinal axis oriented perpendicular to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second radio frequency transceiver adapted to receive said radio frequency signal containing information regarding the phase of said low frequency signal;

said interior control unit being adapted to maintain a replica of said low frequency signal transmitted by said exterior control unit, said replica being continuously adjusted to match the timing of said low frequency signal using information received from said exterior control unit by said second radio frequency transceiver; and

a digital signal processor adapted to compare the phase of signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver.

8. An apparatus for controlling the position of a mandrel within a pipe comprising:

an exterior control unit including a low frequency signal generator;

a transmit coil, and a first radio frequency transceiver;

said transmit coil being positioned proximate to the outside surface of a wall of said pipe and having a longitudinal axis oriented parallel to the longitudinal axis of the pipe;

said signal generator being operably connected to said transmit coil to transmit low frequency electromagnetic signals through said wall;

said first radio frequency transceiver transmitting a radio frequency signal;

an interior control unit mounted on said mandrel and including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil having a longitudinal axis oriented parallel to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second receive coil having a longitudinal axis oriented perpendicular to the longitudinal axis of the pipe, said coil being adapted to receive said low frequency electromagnetic signals passing through said wall;

said second radio frequency transceiver adapted to receive said radio frequency signal containing information regarding the phase of said low frequency signal; and

a digital signal processor adapted to compare the phase of signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver;

wherein said radio frequency signal transmitted by said first radio frequency transceiver includes a plurality of command data packets, said interior control unit is adapted to receive said command data packets and to transmit an answering radio frequency signal including a corresponding response data packet after receiving each of said command data packets, and said exterior control unit is adapted to receive said answering radio frequency signal.

9. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 8, wherein said command data packets includes information regarding the phase of said low frequency signal.

10. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 8, wherein said exterior control unit is adapted to calculate a round-trip transmission time for each of said command data packets by first recording a send time when one of said command data packets is transmitted, then recording a receipt time when a response data package corresponding to said one of said command data packets is received by said exterior control unit, and then determining the time difference between said send time and said receipt time, said time difference being said round-trip transmission time.

11. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 10, wherein said exterior control unit is adapted to maintain a running average round-trip time, said running average round-trip time being calculated by taking the arithmetic average of a predetermined number of the most recent of said round-trip transmission times.

12. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 11, wherein said predetermined number of the most recent of said round-trip transmission times used for calculating said running average round-trip time is 100.

13. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 11, wherein time base information regarding the phase of said low frequency signal is pre-adjusted by an amount equal to 0.5 times the running average round-trip time before being transmitted by said exterior control unit over said radio frequency signal.

14. An apparatus for controlling the position of a mandrel within a pipe comprising:

a first control unit including a transmit coil and a first radio frequency transceiver;

said transmit coil being positionable proximate to one of an inside surface and an outside surface of a wall of said pipe and being adapted to transmit low frequency signals through said wall;

said first radio frequency transceiver being adapted to transmit radio signals containing information regarding the phase of said low frequency signal;

a second control unit including a first receive coil, a second receive coil and a second radio frequency transceiver;

said first receive coil being positionable proximate to an other of said inside surface and said outside surface of said wall of said pipe, having a first orientation with respect to the longitudinal axis of said pipe, and being adapted to receive said low frequency signals passing through said wall;

said second receive coil being positionable proximate to said other of said inside surface and said outside surface of said wall of said pipe, having a second orientation with respect to the longitudinal axis of said pipe, and being adapted to receive said low frequency signals passing through said wall;

said second radio frequency transceiver being adapted to receive said radio signals containing information regarding the phase of said low frequency signals; and

a digital signal processor adapted to compare the phase of low frequency signals received by said first and said second receive coils to a time base containing information regarding the phase of said low frequency signal received from said first radio frequency transceiver.

15. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 14, wherein said digital signal processor is further adapted to compare the amplitude of said signal received by one of said first and second receive coils to the amplitude of the signal received by another of said first and second receive coils.

16. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 14, wherein said second control unit is adapted to maintain a replica of said low frequency signal transmitted by said first control unit, said replica being continuously adjusted to match the timing of said low frequency signal using information received from said first control unit by said second radio frequency transceiver.

17. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 14, wherein said radio signal transmitted by said first radio frequency transceiver includes a plurality of command data packets, said second control unit is adapted to receive said command data packets and to transmit an answering radio signal including a corresponding response data packet after receiving each of said command data packets, and said first control unit is adapted to receive said answering radio signal.

18. An apparatus for controlling the position of a mandrel within a pipe in accordance with claim 17, wherein said first control unit is adapted to calculate a round-trip transmission time for each of said command data packets by first recording a send time when one of said command data packets is transmitted, then recording a receipt time when a response data package corresponding to said one of said command data packets is received by said first control unit, and then determining the time difference between said send time and said receipt time, said time difference being said round-trip transmission time, and said first control unit is further adapted to use said round-trip transmission time to adjust time base information regarding the phase of said low frequency signal before transmitting said time base information over said radio signal.

19. A method for determining the position of an apparatus within a pipe, said method comprising the steps of:

transmitting a low frequency electromagnetic signal from a transmit coil which is operably connected to a first control unit, said transmit coil being located at a known position outside said pipe;

transmitting a radio frequency signal from a first transceiver which is operably connected to said first control unit, said first transceiver being located outside said pipe;

receiving said low frequency electromagnetic signal with first and second receive coils which are mounted at known positions, respectively, on said apparatus within said pipe and operably connected to a second control unit;

receiving said radio frequency signal with a second transceiver which is mounted on said apparatus within said pipe and operably connected to said second control unit; and

using a digital signal processor to compare the phase of the low frequency signals received by said first and second receive coils to a time base containing information regarding the phase of said low frequency signal, said information regarding the phase of the low frequency signal being transmitted from said first transceiver to said second transceiver on said radio frequency signal.

20. A method for determining the position of an apparatus within a pipe in accordance with claim 19, further comprising the step of maintaining in said second control unit a replica of said low frequency signal transmitted by said transmit coil, said replica being continuously adjusted to match the timing of said low frequency signal transmitted by said transmit coil using information received by said second transceiver from said first transceiver on said radio frequency signal.

21. A method for determining the position of an apparatus within a pipe in accordance with claim 19, wherein said radio frequency signal transmitted by said first transceiver includes a plurality of command data packets produced by said first control unit, said command data packets including information regarding the phase of said low frequency signal.

22. A method for determining the position of an apparatus within a pipe in accordance with claim 21, further comprising the steps of:

receiving in said second control unit said command data packets transmitted by said first transceiver;

producing in said second control unit, for each of said command data packets received by said second control unit, a corresponding response data packet;

transmitting an answering radio frequency signal from said second transceiver, said answering radio frequency signal including said corresponding response data packets;

receiving said answering radio frequency signal with said first transceiver; and

receiving in said first control unit said response data packets corresponding to said command data packets previously produced.

23. A method for determining the position of an apparatus within a pipe in accordance with claim 22, further comprising the step of calculating a round-trip transmission time for each of said command data packets by first recording a send time when one of said command data packets is produced by said first control unit, then recording a receipt time when a response data package corresponding to said one of said command data packets is received by said first control unit, and then determining the time difference between said send time and said receipt time, said time difference being said round-trip transmission time.

24. A method for determining the position of an apparatus within a pipe in accordance with claim 23, further comprising the step of pre-adjusting said information regarding the phase of said low frequency signal included in command data packets to be transmitted using information regarding round-trip times for previously transmitted command data packets.

25. A method for controlling the position of an apparatus within a pipe, said method comprising the steps of:

determining a current position of said apparatus within said pipe by transmitting a low frequency electromagnetic signal from a transmit coil which is operably connected to a first control unit, said transmit coil being located at a known position outside said pipe, transmitting a radio frequency signal from a first transceiver which is operably connected to said first control unit, said first transceiver being located outside said pipe, receiving said low frequency electromagnetic signal with first and second receive coils which are mounted at known positions, respectively, on said apparatus within said pipe and operably connected to a second control unit, receiving said radio frequency signal with a second transceiver which is mounted on said apparatus within said pipe and operably connected to said second control unit, and using a digital signal processor to compare the phase of the low frequency signals received by said first and second receive coils to a time base containing information regarding the phase of said low frequency signal, said information regarding the phase of the low frequency signal being transmitted from said first transceiver to said second transceiver on said radio frequency signal;

determining a desired position of said apparatus within said pipe;

determining a position error between said current position and said desired position;

using a control algorithm to calculate a control input needed to reduce said position error; and

moving said apparatus in response to said control input.

26. A method for controlling the position of an apparatus within a pipe in accordance with claim 25, wherein said control algorithm is proportional-integral-derivative control algorithm.