WO1986000860A1

WO1986000860A1 - Inspection device

Info

Publication number: WO1986000860A1
Application number: PCT/SE1985/000293
Authority: WO
Inventors: Hans Lundberg
Original assignee: Lundberg, Ewa
Priority date: 1984-07-23
Filing date: 1985-07-23
Publication date: 1986-02-13
Also published as: SE8403826L; EP0188565A1; SE8403826D0

Abstract

An inspection robot (1) moving step by step for inspecting underwater parts of fixed or floating objects, for example ships' hulls, has members, such as suction discs (4), which are alternately releasably fixable on the surface of the object and rotatably mounted on the frame (3) of the robot (1), such that the frame for each step is pivoted a certain distance in one direction about the respective member as a result of a reaction force from a rotating member, preferably a cleaning tool (5), which is mounted on the frame and is adapted to act against the object, and also expose the surface to be inspected, to an inspection camera (13) mounted on the frame.

Description

INSPECTION DEVICE

Technical field

The present invention relates to a device for in¬ specting underwater parts of fixed or floating objects, for instance ships' hulls. State of the art

When the classification societies earlier inspected the bottoms of ships, the inspector either had to dive himself or could study a TV image from diver-operated TV cameras. Use has been made of a remote-controlled camera-supporting carriage which is retained against the surface to be inspected, by means of a vacuum-gene¬ rating propeller, and which is driven and guided by wheels. The drawback of this construction is its lack of accuracy because the wheels may slip and, especially in waters with rapid currents, the construction has difficulties in moving against or transversely of the direction of the currents. Besides, it is not capable in a suitable manner of preparing the surface to be inspected for the driving and guiding wheels and, above all, for the inspecting TV camera. Object of the invention

The object of the present invention is to provide an inspection device which overcomes at least part of the shortcomings indicated above. Disclosure of the invention

This object is achieved in that the unit for dis¬ placing the device comprises at least two members ro- tatably mounted on a frame and alternately releasably fixable on the object to allow alternate pivotal movement or turning of the frame on the object, and at least one means which is rotatable by means of a motor in alternating directions and fixed with its motor on the frame and which preferably forms a unit for cleaning the surface to be inspected. 2

Thus, the invention provides an inspection device referred to as inspection robot hereinbelow, which is capable of moving step by step on the object by means of members, for instance suction discs, electromagnets or the like, alternately fixed on the object and whose frame for each step is pivoted a certain distance in one direction as a result of the reaction force and the torque from one or more motor-driven rotary means, such as wheels, propellers or, preferably, cleaning units, such as brushes or scrapers, acting against the object and at the same time exposing the surface to be inspected, to an inspection unit, such as a TV camera. The following text primarily deals with the alternative using suction discs, and the rotary means is/are exem- plified primarily by a rotary cleaning brush which brings about such pivotal movement of the entire robot as will move the suction disc which is unengaged or not sucked to the object, a certain distance.

Thus, the pivotal movement of the robot is obtained by the brush rotating in the opposite direction and having its centre of rotation spaced the same distance from the centres of rotation of the two suction discs, which latter centres may also suitably be spaced from each other by said distance. If the brush is capable of cleaning a surface which is at least equally wide as required by a suction disc for ensuring a safe en¬ gagement against the object, one suction disc will always advance along a cleaned path irrespective of the ampli¬ tude of the angle of pivotment. During normal travel straight forwards, the in¬ spection robot for each step may pivot for instance through 60°, whereby the displacement in the main di¬ rection becomes equal to the selected distance between the centres of rotation of the two suction discs and between these centres and the centre of rotation of the rotary brush.

The energy, being e.g. electric or hydraulic and 3 controlled by a control unit, for instance a microcom¬ puter, or by an operator, may be supplied to the motor of the brush by a power supply cable by means of which e.g. information from a robot-navigating TV camera, an inspecting TV camera, optionally ultrasonic plate thickness measuring means, a potential metering reference electrode, etc, may also be transmitted to a suitable control and observation site above the water surface. In order that the inspection robot should move in the desired direction on the object and with the desired length of each step, it is essential that the operator or control unit (microcomputer) at each instant receive acceptable information about the angle of pivotment of the robot about the suction disc being fixed on the object. On vertical surfaces, this information may be obtained from an instrument measuring the angle between the vertical and a reference line on the robot, this also giving information on the direction of travel of the robot. Instruments of this type are previously known. On horizontal surfaces, e.g. the flat bottom of a vessel, one must however rely on "dead reckoning" to a greater extent, until the navigating or inspecting TV camera has recorded e.g. a weld joint which may be used as reference direction. In this case, the control unit only requires information about when a desired angle, set in the control unit (microcomputer), in relation to the active suction disc adhering to the object has been attained, whereupon the control unit emits a signal for switching suction discs adhering to the object, and the direction of rotation of the brush. To this end, each suction disc may for example be provided around its periphery with a number of equidistantly distributed detectable bodies, for instance magnets or pieces of soft iron, which upon passage of a sensor emit a pulse. The angle between the different pulse passages is de¬ termined by the number of detectable bodies.

For a change of course of the robot, the control unit (microcomputer) is supplied with an instruction (e.g. an instruction programmed in advance) to demand, for a change of the direction of the course, a larger number of pulses or, alternatively, a smaller amount of pulses in the opposite direction of rotation before initiating switching of suction discs and change of the direction of rotation of the brush. The arrangement may be such that the operator, on a control panel in the control unit, first pushes a button indicating the direction of change of the course and thereafter digitally the desired change of course. It is then obvious to design the control unit so that it can order the robot to "walk" a predetermined distance (a preselected number of steps) in the direction set and, if required, to make a stop for a closer study of interesting details. The expert may of course supply a microcomputer in advance with a sequential directive and make it store all executed manoeuvres as documan-tation. Accompanying drawings The invention will be described in greater detail hereinbelow with reference to the accompanying drawings which show a presently particularly preferred embodiment. Fig. 1 schematically illustrates the inspection robot from above, and Fig. 2 schematically illustrates the robot from the side, turned upside down with respect to Fig. 1. Fig. 3 is an example of a sequence of movement which the robot can perform. Preferred embodiment

The inspection robot generally designated 1 is connected by means of a power supply cable 2 to a control unit (not shown) disposed above the water surface and accessible to an operator, e.g. on the vessel of which the parts located under the water surface should be inspected. The control unit may be an e.g. programmable microcomputer.

The inspection robot 1 is carried on a flat frame 3 in which two suction cups or discs 4 are articulated. The centres of rotation of the discs are designated V and H-, respectively. The motor for a motor-driven circular brush 5 rotatable in both directions is fixedly mounted on the frame 3 such that the brush will be located on the same side of the frame as the suction discs. The centre of rotation of the brush is designated B. V, H and B are located in the corners of an equilateral triangle or adjacent thereto.

Between the two suct'ion discs 4, there is provided a water pump 6 which by hoses 7, is adapted alternatingly to suck water from the left suction disc 4 fixed to the object, and to eject the water in the right disc being released, and vice versa. Such suction discs are known per se. The motor of the pump 6, like the motor 8 for the rotary brush 5, may be driven pneumatically, hydraulical- ly or electrically. Hydraulics being preferred for various reasons, the continued description will be concerned with that alternative. The direction of the hydraulic flow through the two motors 6, 8 is determined by an electrically operated directional valve 9 which, by an electric lead in the power supply cable 2, is operably connected to the control unit. The bearings of the suction discs 4 are hollow for said pump-generated flows of water and spherical to enable the discs 4 to adjust themselves against any inclined surface, for instance when climbing on a pipe. Around the periphery of each suction disc 4, there is provided a given number of evenly distributed soft iron bodies 10 or small bar magnets. In a shielded po¬ sition on the frame, there are sensing forks 11 which transmit a pulse to the control unit upon each passage of the soft iron bodies 10 on the adhering suction disc 14. In this manner, the "angle of pivotment" of each step is determined.

By its rotational movement, the cleaning brush 5 produces a torque on and, by simultaneously engaging the ship's hull, a reaction force against the frame 3, resulting in a pivotal movement of the robot, about the suction disc 4 presently sucked to the object, in a direction opposite to the direction of rotation of the brush.

When the right-hand suction disc 4 is fixed to the object, the brush 5 is rotated to the left, whereby the entire robot 1 will pivot to the right with the right-hand suction disc 4 as centre of rotation. If the pivotal movement is 60°, the left-hand suction disc 4 will come to the position which the brush 5 occupied when starting to walk to the right.

After sensing the angular change corresponding to one step, the control unit switches the directional valve 9 and the direction of rotation of the brush 5, such that the same pivotal movement of the robot is performed in the opposite direction.

The effective or resultant direction of travel will then of course lie between the two turning positions. If the diameter of the brush 5 exceeds the diameter of the suction discs, the robot can pivot to an unlimited extent without any suction disc entering into a non- brushed area. The control unit is so designed as to permit ob¬ taining a change of course by requesting a larger pivotal movement of the robot in the desired direction before ordering the robot to turn, or a pivotal movement through a smaller angle in the opposite direction. in the case where the reaction moment from the rotary brush 5 is not capable of sufficiently rapidly pivoting the robot forwards in a step, it is possible to incline the brush 5 slightly, so that its edge remote from the suction discs 4 is pressing slightly harder against the object.

In the illustrated preferred embodiment now de¬ scribed, the robot 1 is navigated by means of a TV ca- mera 12 which is oriented in the direction of travel, and performs the inspection by means of a TV camera 13 which is disposed just astern of the suction discs 4. The inspection camera 13 may be replaced by a video equipment, a potentiometer or an ultrasonic meter, as described above, according to the purpose of the in¬ spection.

The navigation camera 12 and the inspection camera 13 are mounted on either end of a beam 14 which inter- mediate its ends is fixed at the upper end of a post

15 rotatably mounted on the frame 3. The post 15 extends at right angles to the surface to be inspected and is suitably disposed far astern where the movements trans¬ versally of the direction of travel are not as rapid. The post 15 with the associated beam 14 and the cameras 12, 13 is balanced hydrostatically and hydrodynamically and should theoretically be able to maintain its direction close to the direction of travel.

The navigation camera 12 is of course directed forwards in the direction of the beam 14, and the in¬ spection camera 13 at the rear end of the beam is directed straight inwards towards the surface, for instance the shell plating of a vessel.

In order to correct any misorientation which may occur for several reasons, fixed dampers can be arranged or allowed to pivot inwards such that every time the robot 1 commences a new step (change of direction) they can remind the camera-supporting beam 14 of the correct orientation. The pivotal movements of the inspection robot 1, water currents etc. should affect as little as possible the orientation of the camera-supporting beam 14 in the direction of travel. The above-mentioned hydrodynamic stabilization and dampening is however difficult to ensure with currents of varying angles of incidence.

To solve this problem, it is possible to make the part of the beam 14 supporting the navigation camera 12 telescopic and hollow. If this part of the beam is shorten¬ ed, the moveable part will become "windward", i.e. will tend to be oriented against the current, and if it is extended excessively, the device will become "leeward". Means sensing changes of direction, for instance a simplified type of a directional gyro of an aircraft (indicating changes of course), may then serve to sense any tendency of deviation from the desired orientation, whereupon a signal is emitted such that e.g. a hydraulic cylinder changes the beam length so as to obtain the desired balance and dampening.

As an alternative, the beam 14 may be maintained in the direction of travel mechanically or electrically. For example, the movements of the suction discs 4 and the beam 14 may be synchronized, for instance by means of toothed wheels and chains, links etc.

The microcomputer is ordered to cause the robot 1 to move a certain number .of steps in a certain direction, . . . whereupon a resting position can be programmed, in which the brush 5 should be stopped in order not to wear out the paint covering the hull, or normally a change of course. Naturally, the memory of the microcomputer may receive a sequence of orders simultaneously. Another memory may then be used for storing and subsequently documenting all operational steps.

Fig. 3 schematically illustrates from below the pattern of movement of the brush 5 and of the suction discs 4, the centres of the successive turning positions of the brush 5 being designated Bl B10. The centre of rotation of the left suction disc 4 is designated

VS and the centre of rotation of the right suction disc HS, followed by numbers of position which, if underlined, indicate that the point of rotation in question, imme¬ diately before turning, is fixed. Consequently, the inspection robot 1, e.g. in phase 5, will pivot about the point VS_5 (coinciding with the point, VS4, to which the left suction disc 4 is moved in phase 4, and the point, B3, where the brush 5 has switched its direction of rotation and movement in phase 3) , and the centres of rotation of the robot 1 are located in the three positions "5" immediately before a change of course and change of the centres of pivotment of the robot.

In the next phase, 6, the robot pivots about HS6, VS assuming the turning position, B5, VS6, VS which the brush has just left, and the brush moves to position B6. In phase 7, VS is locked (in VS7) , and HS is released and accompanies the robot to HS7 while the brush 5 moves up to B7.

Assuming now that the operator wishes to carry out a 120 turn to the right, performed in phase 8, where the pivotment of the inspection robot 1 becomes 180°, so that the brush 5 moves half a turn about the centre of rotation HSS3, performing a cleaning operation of its entire path of movement, so as to offer at any point a prepared surface to the left-hand suction disc 4 which, in the illustrated instance, arrives in position VS8 where, at the beginning of phase 9, it is fixed and forces the rotationally pivoted brush to move on to B9.

The hatched portions in Fig. 3 define the surface cleaned by the brush 5.

In the illustrated example, the inspeciton robot 1 moves from one section of the surface to another, as appears from Fig. 3, on a straight course, always with pivotal movements of 60 . The length of each step in the direction of travel then becomes equal to the side of the equilateral triangle defined by the centre of rotation B of the brush and the centres of rotation V and H of the suction discs.

The required "road width" freely available and relatively free from obstacles (for instance anodes) substantially corresponds to the double brush diameter, slightly more than 90% of the "roadway" being cleaned. Only in the case of a very close turn, a relatively small isolated spot may escape brushing, which is however of no practical consequence.

The invention should of course not be considered restricted to the embodiment illustrated in the drawing and described above but may, as indicated above, be modified in many different ways within the spirit and scope of the patent protection as claimed. Thus, there may be provided more than two suction discs 4 and more than one brush 5. These members may be combined in dif¬ ferent groups and/or units together yielding the desired function. When the driving rotary means consists of a cleaning unit, the brush 5 may be replaced by a series of sea-acorn scapers or consist of a combination of brush and scraper. Such cleaning units may, as mentioned above, be replaced by propellers, wheels etc. for pivoting the frame. However, the pivotal movement of the frame about the members 4 may also be achieved by turning directly at the members, for instance by means of gear rings mounted on the members and meshing with toothed wheels rotatable by means of a motor.

Claims

1. A device for inspecting underwater parts of fixed or floating objects, for instance ships'hulls, said device having a frame (3^") with a frame-displacing unit comprising at least two members (4) alternately releasably fixable on said object, and with an inspection unit (13) for inspecting the path on the surface along which the frame is displaced by means of the frame-dis¬ placing unit, c h a r a c t e r i s e d in that said members (4) are rotatably mounted on the frame at a distance from each other to allow pivotal movement of the frame in one direction about one of said members and, alternately, pivotal movement of the frame in the opposite direction about the other of said members, and that the frame-displacing unit further comprises at least one motor-driven means (5) which together with its motor (8) is mounted on the frame at a distance from the members (4) and is rotatable in opposite di¬ rections and adapted by its torque and by forces produced by its rotation, to bring about said pivotal movement of the frame, and that the device further comprises means (2, 9, 10, 11) which are adapted, in dependence upon the extension of said path, to bring about alternate fixing of said members and a corresponding alternate change of the direction of rotation of said motor-driven means.

2. Device as claimed in claim 1, c h a r a c t e r ¬ i s e d in that the means (5) is a cleaning brush or scraper.

3. Device as claimed in claim 1 or 2, c h a r a c - t e r i s e d in that said members (4) consist of suction discs (4), magnets or the like.

4. Device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said members (4) and said means (5) are disposed each at one corner of an equilateral triangle.

5._.Device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the inspection unit comprises recording means (13) disposed just astern of said members (4).

6. Device as claimed in claim 5, c h a r a c t e r ¬ i s e d in that the recording means is a camera (13), video recorder, potentiometer, ultrasonic meter or the like.

7. Device as claimed in any one of the preceding claims, c h a r a c t e r i s e d by a navigation unit (12) for navigating the device (1) in the desired di¬ rection of travel.

8. Device as claimed in claim 7, c h a r a c t e r - i s e d in that the navigation unit consists of a camera

(12) or the like oriented in the direction of travel.

9. Device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the inspection and navigation units (12, 13) are mounted at either end of a beam (14) which intermediate its ends is fixed on a post (15) rotatably mounted on the frame (3) and, irrespective of the pivotal position of the device (1), maintaining the inspection and navigation units in the direction of travel.

10. Device as claimed in any one of claims 7-9, c h a r a c t e r i s e d in that the navigation unit (12) is mounted telescopically displaceable on one end of the beam (14).