GB2570101A

GB2570101A - Survey system and method

Info

Publication number: GB2570101A
Application number: GB1718926.7A
Authority: GB
Inventors: Prior-Jones Michael; Hole Christopher
Original assignee: TTP PLC
Current assignee: TTP PLC
Priority date: 2017-11-16
Filing date: 2017-11-16
Publication date: 2019-07-17
Also published as: GB201718926D0

Abstract

A system for surveying a pipe or duct network comprises: two moveable robots deployed within the pipe; a distance measurement device (i.e. laser, stadiometric, acoustic, ultrasonic RF or microwave rangefinder and/or a total station) for determining the distance between the robots; an angle measurement device (i.e. theodolite and/or total station) for determining the relative angle between the robots; a reference measurement device for referencing a determined position on a surface above the pipe network with respect to at least one of the robots; and means for controlling the robots and measurement devices to determine the position of the pipe or duct network in three dimensions. The robots may comprise a communications subsystem to communicate (i.e. wired, acoustic, optical, RF, mm-wave, microwave), which may be combined with the distance and/or angle measurement devices. At least one of the robots may be self-driving, propelled by airscrews, be capable of flying within the pipe and/or be propelled by wheels or tracks. The system may further comprise an imaging system, and/or sensor(s) and/or non-destructive test equipment for monitoring/assessing one or more characteristics of the pipe. One of the robots may comprise an immobilisation device (i.e. expanding collar, inflatable structure and/or magnetic attachment).

Description

Survey System and Method

The present invention comprises a system and method for surveying utility (such as water and gas) supply networks.

A need exists to locate utility pipe or duct networks in three dimensional space, representing depth as well as x-y position of those networks relative to a surface map or geographic database. For example, sections of gas pipe networks remain in use that were installed more than a century ago when geolocation was difficult and expectations of record keeping and accuracy were much lower. Mapping this network has always been a challenge but accurate network maps are increasingly important as urban centres become more congested, health and safety expectations increase, and the replacement program for aging assets gathers pace. Lack of accurate position data also increases the cost of network remediation and replacement because digs and road closures cannot be accurately planned until reliable position data can be gained from physical trench digging.

Many networks and utility suppliers have tried to address this challenge, in some cases with major development programs, but problems remain. For example, none have solved the problem of the rate at which errors build up as an in-pipe measurement device (often called a pig) moves through the network. In view of this prior art techniques still demand a substantial program of trench digging to accurately locate buried pipes.

According to the present invention there is provided:

The present invention provides a solution to the above error build up problem, thus enabling large sections of the network to be accurately surveyed from inside the pipe or duct without the need to dig. Further, the present invention addresses the technical challenges that have prevented the prior art from providing a cost effective solution. The present invention can further be arranged to incorporate sensors that can be configured to provide commercially useful information regarding the characteristics of the network as a whole or even section by section, for example by including sensors (e.g. visual, electromagnetic and ultrasound) to characterise the condition of the pipe or duct that provides commercially useful information.

Examples of the present invention will now be provided with reference to the accompanying drawings, in which:

Figure 1 is a side schematic side-view of a first example of the present invention positioned within a pipe;

Figure 2 is a schematic side-view of an example of the present invention within a pipe which has a sample pipe attached thereto; and

Figure 3 is a schematic side-view of a pipe with an incline showing a further schematic view of the device of the invention.

Figure 1 illustrates an example of the present invention, applying a pair of robotic vehicles to carry out the survey. One carries a survey station station (the “surveyor robot”) and the other a corner reflector (“the rodbearer robot”). The surveyor robot carries, in this example, a total station, which will be described in more detail below, and is arranged to determine the distance and angle of orientation between itself and the rodbearer robot in a manner that will be described below. However it will be appreciated that it may use devices other than a total station to determine distance, such as a laser rangefinder, stadiometric rangefinder, an acoustic or ultrasonic rangefinder, a radiofrequency, mm-wave, microwave or other rangefinder, or a combination thereof. The angle of orientation can also be determined using other devices, such as a theodolite.

At least one, if not both, of the robots incorporates an immobilisation device which can ensure that the robot is secured within the pipe or duct before a measurement is taken, and which can then be disabled when the robot is required to move. The immobilisation device may be a collar that can expand to fit the pipe or duct and retract for forward motion. Alternatively the immobilisation device may be an inflatable structure that can expand to fit the pipe or duct and then be deflated and retracted when the robotic vehicle is required to move. Alternatively, in the case of some metallic pipes, the immobilisation device may be a magnetic device which can be deactivated or retracted when the robotic device is required to move.

At least one of the robots will usually incorporate a mechanism to ensure that the theodolite, total station or other angle-measuring subsystem is level before a measurement is taken.

The robots incorporate a communications subsystem allowing each to communicate with the other. The communications subsystem can be wired; optical; radio-frequency, mm-wave, microwave or acoustic. The communications subsystem may be combined with either the range-determining components, angle-determining components, or both.

The robots are self-driving and can use one of a number of techniques for propulsion dependent upon the network to be surveyed. Airscrews can be employed, and the robots may be capable of flying within the pipe or duct if required. Alternatively the robots are propelled by wheels or tracks.

The present invention provides a compact, automated survey system which deploys at least two robots that co-operate to maintain accuracy over large distances, sufficient to map very large networks. The linear nature of pipes and ducts can make accuracy of measurement degrade more rapidly but with the present invention accuracy can be maintained over length scales of several kilometres and, using the presence of existing access points for siphons and gas sampling in the network (which can be located using GPS), can ensure that accuracy can be validated as the survey progresses. This is shown in figure 2 and is described further below.

The present invention achieves an accurate survey within a pipe or duct by applying known principles of land surveying in a novel and inventive way. The basic principles of land surveying go back many centuries, with many of the optical techniques having been developed in the 18th century. However, more recent technology developments, such as miniature digital cameras, diode lasers and micro orientation sensors are employed in the invention in combination with those techniques to provide a system employing those surveying techniques within a pipe or duct network. The system can then also, when needed, reference to control points on the surface to improve accuracy of the survey data.

When carrying out surveys surveyors traditionally used a theodolite, which is a telescope mounted so that it can turn both horizontally and vertically. A target point is sighted in the crosshairs of the telescope, and then the horizontal and vertical angles can be read out. Since measuring angles between sighting points is very much easier and more accurate than measuring distance with a measuring rod or trundle wheel, surveyors would usually establish a measured “baseline” distance between two theodolite points and then do the rest of the surveying entirely by measuring angles.

Modern electronics and optics makes it possible to combine the theodolite with a laser rangefinder, so that a single instrument can measure both range and bearing to a target point. This is called often called a total station. The total station works in partnership with a corner reflector (usually a prism) mounted on a ranging rod held at the point of interest. It measures both the range and angles to the reflector automatically. “Robotic” total stations contain motors to move the optics, and can therefore be operated by a single surveyor by remote control: the surveyor places the rod, presses a button on the remote, and the total station records the range and bearing to the rod position and stores it. A map is then generated automatically. Such systems are designed to be operated in locations where access to the site to be surveyed by a surveyor is straightforward and location of the total station and optics can be achieved easily.

The present invention adapts a robotic total station to conduct a survey in a manner analogous to a “traverse survey” used when surveying a predominantly linear feature like a coastline, road or railway line. The invention has particular utility, for example, when applied to enable surveying of the pipe or ductgas mains from inside. Measuring distances and angles along the pipe or duct allows the position of the pipework to be determined in three dimensions.

The first part of any survey is to determine the position of control points, these are points whose positions are known very accurately, and the rest of the survey is carried out relative to their position. Existing survey-grade GPS techniques can be used to establish the position of pre-existing siphon or gas sampling points on the surface. In the present embodiment, these positions are then referred down to the surveyor robot as shown in figure 2. Assuming that the sampling point has line-of-sight access to the core of the pipe or duct, the surveyor robot can then measure a corner reflector on the surface to obtain the depth and angle from the control point on the surface, as shown in Figure 2.

The rodbearer robot moves ahead of the surveyor robot. The surveyor robot will secure itself in position and take the range and bearing to the rodbearer. It will then command the rodbearer to move forwards and continuously measure range and bearing until either the rodbearer reaches a bend in the pipe or reaches the range of the rangefinder. In the case of reaching a bend, the surveyor will track the corner reflector on the roadbearer and will observe it starting to move out of sight. At this point the surveyor will command the rodbearer to stop, and then move towards the rodbearer, stopping when the two robots are almost touching. This is shown in figure 3. The process will then repeat.

The robots can carry additional sensors as they travel along the main. An example is an imaging system (one or more cameras) to take pictures of the inside of the main and reference them to the recorded positions from the survey. Subject to space and power constraints, other types of inspection or nondestructive test equipment can also be carried on the robots.

Claims

1. A system for surveying a pipe or duct network, the system comprising:

two moveable robots arranged to be deployed within the pipe or duct network in use;

a distance measurement device for determining the distance between the robots in use;

an angle measurement device for determining the relative angle between the two robots in two dimensions in use;

a reference measurement device for referencing a determined position on a surface above the pipe or duct network with respect to at least one of the robots in use; and means for controlling the robots and the distance, angle and reference measurement devices so as to determine the position of the pipe or duct network in three dimensions.

2. The system of claim 1 wherein the distance measurement and angle measurement devices are mounted on one of the robots and a reference marker for use with the distance measurement and angle measurement devices is mounted on the other of the robots.

3. The system of claim 1 or claim 2, wherein the distance measurement device comprises at least one of: a laser rangefinder; a stadiometric rangefinder; an acoustic or ultrasonic rangefinder; a radiofrequency or microwave rangefinder; and a total station.

4. The system of claim 1, 2 or 3, wherein the angle measurement device comprises at least one of a theodolite and a total station.

5. The system of any preceding claim, wherein at least one of the robots comprises an immobilisation device which is arranged to secure said robot within the pipe or duct before a measurement is taken in use, and which is arranged to be be disabled when the robot is required to move.

6. The system of claim 5, wherein the immobilisation device is a collar that can expand to fit the pipe or duct and retract for forward motion.

7. The system of claim 5, wherein the immobilisation device is one of: an inflatable structure that can expand to fit the pipe or duct in use and then be deflated and retracted when the robot is required to move; or a magnetic attachment device that can be de-energised or retracted from the pipe wall when the robot is required to move.

8. The system of any preceding claim, wherein at least one of the robots comprises a mechanism to ensure that the angle measurement device is level before a measurement is taken in use.

9. The system of any preceding claim, wherein the robots comprise a communications subsystem allowing each robot to communicate with the other.

10. The system of claim 9, wherein the communications subsystem is at least one of a: wired; acoustic; optical; radio-frequency; mm-wave or microwave system.

11. The system of claim 9 or 10, wherein the communications subsystem is combined with either the distance determining device, angle determining device, or both.

12. The system of any preceding claim, wherein at least one of the robots is self-driving.

13. The system of claim 12, wherein at least one of the robots is propelled by one or more airscrews.

14. The system of claim 12, wherein at least one of the robots is capable of flying within the pipe or duct.

15. The system of claim 12, wherein at least one of the robots is propelled by wheels or tracks.

16. The system of any preceding claim, further comprising means for determining for determining the range and bearing between at least one of the robots and a fixed point of known location within the pipe or duct network.

17. The system of any preceding claim, further comprising one or more of an imaging system, a sensor or inspection equipment for monitoring one or more characteristics of the pipe or duct, or nondestructive test equipment for assessing one or more characteristic of the pipe or duct

18. A method of surveying a pipe or duct network, the method comprising the steps of:

placing the system of any preceding claim within the pipe or duct network;

moving a first one of the robots with respect to the other; measuring the relative distance and angles between the robots; when the first robot either reaches the range limit of the distance measurement device, or reaches the line-of-sight limit of the angle measurement device: stopping the moving robot and measuring the relative distance and angles between the robots, moving the second robot until it is adjacent to the first robot, determining again the relative distance and angles between the robots, and then starting further movement of the first robot; wherein the above steps are repeated until a desired amount of the pipe or duct network has been surveyed.