Abstract:
A gas pipe explorer formed of a plurality of connecting elements, and an articulation element between the connected elements. The connected elements include drive capabilities, and the articulation element allows the connected elements to traverse gas pipes of arbitrary shapes and sizes. A sensor may sends the characteristics of the gas pipe, and the communication element may send back those sends characteristics. The communication can be wired, over a tether connecting the device to a remote end. Alternatively, the connection can be wireless, driven by either a generator or a battery.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the U.S. Provisional Application No. 60/192,705, filed Mar. 28, 2000. 
    
    
     STATEMENT AS TO FEDERALLY-SPONSORED RESEARCH 
     The invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (U.S.C. 202) in which the contractor has elected to retain title. 
    
    
     BACKGROUND 
     The United States has approximately one million kilometers of natural gas distribution pipelines, and also has an uncountable amount of other kinds of pipelines. These networks have been aging, and this aging may cause a great concern to the industries. Much of the network of pipelines is formed of iron and steel pipe which is now considered to be technologically obsolete. 
     It may be desirable to assess the state of various pipes in the network. A failed pipeline may cause an outage, which may be very costly since the utility may be responsible for re-lighting all of the pilot lights which are caused by the outage. In addition, a failed pipeline may cause disruptive urban excavation. 
     Leaks and reductions of pipe wall thickness, may be mostly the result of chemical reactions between iron in the pipe and chemicals in the soil and groundwater. A magnetic flux leakage sensor may be used for determining the average wall thickness of an iron or steel pipe. 
     SUMMARY 
     The present application teaches an intelligent robotic gas pipe explorer. The device may include operating instruments and sensors that may detect leaks, wall thinning, corrosion, and other difficulties in the pipe. 
     In an embodiment, the explorer may be operated wirelessly in an operating pipeline. Information from the exploration is relayed through wireless communications that rely on the waveguide characteristics of the pipeline. For example, this information may be transmitted at GHz frequencies. This system may also use shape reconfigurability to enhance its mobility and to overcome traversal problems such as pipe narrowing, pieces of extending welds, and the like. The device may use an imaging camera for visual inspection. The device may extract power from the flowing gas using a power-generating turbine. 
     Another embodiment uses a wired device, connected and powered by a tether. The wired device may also communicate over that wired line. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects will now be described in detail with reference to the accompanying drawings, wherein: 
     FIG. 1 shows a first embodiment, using a wireless element; 
     FIG. 2 shows a front on view of a second embodiment in an extended state; 
     FIG. 3 shows a single motor in the stowed state; 
     FIG. 4 shows a top view showing the arrangement of motors; and 
     FIG. 5 shows the motors used for articulation. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a first embodiment of the gas pipe explorer vehicle. A majority of the gas distribution pipelines are in the form of 4 and 6-inch diameter pipes. These may be tributaries off of main pipes which may be as large as 48 inches in diameter. In addition, the process of welding the tributaries to the mains may leave extensions, e.g. extensions of one inch or even more. 
     The gas pipe explorer is formed of multiple elements which are connected together with connections like a railroad train in a way that allows each device to move independent of the other. The device includes an articulated snake-like robot  100  formed of three connected sections  105 ,  110 ,  115 , as shown, although there may be more elements, or only two sections. Each wheel on each element of the explorer may have its own motor, as shown in FIG. 1 which shows motors  300 ,  301 ,  302 ,  303 ,  304  and  305 . Alternatively, only some of the wheels need to be driven, with others of the wheels being passive. 
     One of the elements of the train is the power generator  105 . The gas flow rate through a four inch pipe is typically 10 meters per second at 4 bar (60 pounds per square inch) of pressure. This can provide sufficient locomotive power to drive the motors. Power-generating turbine  105  may include a permanent magnet motor, which is back driven to be used as a generator. An impeller  106 , which can be radially or axially flow driven, drives a stator  107  that cuts through the field produced by magnet  108 , to extract power from the flow of gas. This power-generating element may be used by itself, or in combination with battery power, to drive all of the driven elements including the motors and the sensors. 
     The vehicle is preferably at least two meters long when extended, to allow its insertion into a four-inch pipe such as  120  that emanates from centerline of a 48 inch pipe. The vehicle allows its head to be lifted 24 inches off the ground and extended into the tributary pipe. 
     The body of the device extends between the motors. The body between motors includes first and second telescoping tubes  130 ,  131 . Each of the tubes  130 ,  131  can be individually telescoped and retracted to cause the device to move into any desired way. For example, the tube  131  may be extended to force the front part  115  to rise to the position of the tributary pipe  120 . However, in order to allow the device to negotiate turns properly, the maximum length of the device in its collapsed position should be less then 4 sqrt(R0{circumflex over ( )}{circumflex over (2)}+R1*(R0−R2)−R2{circumflex over ( )}{circumflex over (2)}), where R0 is the inside radius of the pipe, R1 is the inside radius of the smallest turn in the pipe, and R2 is the outside radius of the telescoping tube. 
     The device may also include inflatable bladders  140  which can be inflated to exert force against side walls of the pipe. Each bladder may be affixed to each of the telescoping tube segments. The bladders can be alternately inflated and deflated, and the telescoping may be extended or retracted. This operation can allow the device to move using an inchworm-like operation. Multiple bladders, on each side of the telescoping segments, can allow positioning of the device within any desired location on the pipe cross-section. In addition, the tube axis may be angled with respect to the pipe axis. This may be important in mobility control. 
     Up to eight bladders may be affixed to each section. Up to four bladders may be affixed to the pipes  130 ,  131 . Control of these bladders may enable intelligent behavior for negotiation of various obstacles. The bladders may also be deflated to reduce the overall diameter, to allow, for example, traversing one-inch obstructions within a four-inch pipe. This may be important, since side pipes may leave obstructions. 
     An alternative embodiment is shown in FIG.  2 . In this alternative embodiment, a snake like robot is formed. The device is formed of a plurality of motor/wheel assemblies, which are spring loaded, and formed along a triangular frame. FIG. 2 shows the basic device. The triangular frame  200  is formed of three-dimensional pieces extending in a substantially triangular shape. A first wheel/motor assembly  210  is located at a first corner  212 . A second corner  214  has a second wheel/motor assembly  220 . The wheel/motor assemblies are shown in their fully extended positions in FIG.  2 . The may rotate by cam action in the direction of arrow  222  into a stowed position. In this stowed position, the wheel/motor assembly fits within the confines of the triangular frame as shown in FIG.  3 . Note that the wheel/motor assembly  210  has rotated in the direction of arrow  222 , into its stowed position. In FIG. 3, the frame in this stowed position may fit within a one-inch pipe. 
     The connections to the wheel/motor assemblies are offset from one another as shown in FIG.  4 . The assembly  210  and assembly  220  are in different locations so that the stowed device has a minimum size. The sensor  404 , which may be a camera and/or any device which can detect the condition of the pipes, may be in the front of the device. FIG. 4 shows the motors extended or deployed to fit into wider pipes. Moreover, the frame  200  may be formed of a spring material to allow the device to contort into different shapes. 
     The motor may be a coreless DC motor available from micromo.com. The preferred motor may be 12 mm in outer diameter. In this embodiment, the wheels may be spaced approximately 7 centimeters apart, providing a total of approximately 30 powered wheels. Each of the motors  100  dissipates a maximum of 0.3 watts. Thirty wheels can hence be configured with a total power dissipation of approximately 10 watts or less. When deployed, the device can operate within a pipe between 4 and 48 inches. When stowed, the device can operate in a pipe as small as one inch. 
     This embodiment may be articulated by flexing the frame  200 . The flat frame is divided into sections shown as  400 ,  402  etc. Each of these sections may be commanded to bend into a circular arc using the motors. For example, the frame may be commanded to bend into the right or left, up or down, or into any combination of the same. Each length, of approximately one-half meter, may be so actuated. Three motors in a cluster, such as  210 ,  220 ,  410 , may be used to push or pull on the frame wires by a screw drive. 
     FIG. 5 shows an arrangement to carry this out. In the FIG. 5 arrangement, smaller motors are used for frame articulation. The motors  500 ,  502 ,  504  may be 8 mm Micromo motors. Four sets of these actuators in may allow complex shapes including the classic threat produce of a cobra snake, with a front, horizontal orientation, a mid vertical orientation, and a rear horizontal orientation. This orientation may be used to enter feeder pipes from inside a larger pipe. Other elements along the length may also be used. 
     Power may be supplied by a fine wire tether. The minimum mass tether to deliver power to the robot with a wasted power W lost in the resistance of the tether, over a two wire umbilical 
     with length L. has an optimal copper radius are given by 
     
       
         R=[ p 2σ( P+W ) 2   L/( 2 πp 1 v   2   W )] 1/4    
       
     
     where copper has a mass density of p1 (8950 kg/m 3 ), the insulation has a mass density of P2 (for Teflon, this being 1450 kg/M 3 ), σ is the resistivity of copper (1.7×10 −8  ohm-m) and v is the dielectric strength of the insulation. This value is very conservatively 10 6  volts/m for Teflon; it is actually about 10 times more than this; however abrasion of the insulation should be accommodated. Note that the gas pipe atmosphere is not explosive since there is no oxygen, so arcing is not catastrophic but could comprise the mission of the vehicle. For these values of the constants and with P=10 watts, L=10 km, and W=200 watts, we get R 1 =176 microns or a 33 gauge wire. The copper in this tether would have a mass of about 4.5 kg. 
     The tether is stored in small canisters as part of each wheel assembly. As each canister is exhausted from the rear of the vehicle, the tether slidse through a hole in the front and pull out from the next canister forward. In this manner, the tether weight can be distributed over the length of the vehicle and the vehicle range increased in a modular way by decreasing the number of wheel assemblies. 
     Communications may be provided by modulating the current in the power tether using commercially available powerline modulation technologies. 
     Although only a few embodiments have been disclosed in detail above, other modifications are possible.