Patent Publication Number: US-8522905-B2

Title: Magnetic coupling mobile robot

Description:
FIELD OF THE INVENTION 
     The present invention relates to a mobile robot with magnetic coupling. 
     In some applications in the art, surfaces to be processed or treated in various ways, for example, to be welded together, may be inspected by a robot provided with wheels allowing the robot to move along the surface. The robot is fitted with probes able to inspect the surface by detecting, for example, the quality of the process carried out. 
     When the material of which the surface is made allows it, i.e. when it is ferromagnetic, the robot is coupled magnetically to the surface by means of permanent magnets. Thanks to this anchoring system, the robot can also climb vertically or even rotate through 360°. Therefore not only flat surfaces can be inspected, but also curved—for example cylindrical—surfaces. 
     BACKGROUND ART 
     Thus far, robots with magnetic coupling have been fitted with wheels which are made, at least externally, in contact with the surface, of permanent magnets or electromagnets. 
     Prior art solutions exhibit one notable disadvantage. Whilst being able to function, they require enormous power to drive the wheels in order to overcome the magnetic field which tends to immobilize the wheels. It is therefore difficult to achieve free-sliding movement along the surface being inspected. 
     Moving the robot requires a powerful electric motor and therefore the need of electrical wiring to a remote power source, making the robot heavy and cumbersome. 
     SUMMARY OF THE INVENTION 
     The Aim of this invention is to propose a mobile robot with magnetic coupling which is able to overcome, at least partially, the disadvantages described above of the prior art robots. 
     This aim is achieved by a robot in accordance with claim  1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and the advantages of the robot according to the present invention will appear more clearly from the following description of preferred non-limiting embodiments thereof, with reference to the attached drawings, in which: 
         FIG. 1  shows a perspective view of a robot according to the invention; 
         FIG. 2  shows a perspective view of the robot from below; 
         FIG. 3  shows an end view of the robot; 
         FIG. 4  shows an exploded view of a support with permanent magnets; 
         FIG. 5  shows an exploded view of a robot wheel with auxiliary magnets; 
         FIG. 5   a  shows the assembled wheel; 
         FIG. 6  shows an exploded view of another robot wheel; 
         FIG. 7  shows a perspective view of the robot frame according to one different embodiment; 
         FIG. 8  shows an enlarged perspective view of one of the two transverse axles supporting the frame shown in  FIG. 7  and enabling it to slide over a surface to be inspected; 
         FIG. 9  shows a partial cross-section of the transverse axle of  FIG. 8 ; 
         FIG. 9   a  shows a side view of the transverse axle; 
         FIG. 10  shows a view of the transverse axle tilted to the horizontal; 
         FIG. 11  shows an exploded view of a magnet support, according to a different embodiment; and 
         FIG. 12  shows the support of  FIG. 11  duly assembled. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the above figures, numeral reference  1  globally indicates a mobile robot with magnetic coupling according to the invention. 
     Robot  1  includes a frame  10  with wheels  12 ,  14  enabling the robot to slide over a resting surface  2  which is highly magnetically permeable, for example a ferromagnetic material. The robot  1  is in the form of a mobile carriage able to move over a surface, for example a piece of sheeting to be inspected. 
     In accordance with a preferred embodiment, the robot  1  is fitted with at least one driving wheel  12  enabling independent movement over the surface to which it is coupled magnetically. This does not exclude the possibility of the robot described below being moved manually along the resting surface. 
     In accordance with a preferred embodiment, at least one driving wheel  12  is powered by a motor reduction gear  16 . 
     Advantageously, the motor reduction gear  16  is powered electrically with continuous voltage of, for example, 12 V, supplied by a battery  18  fitted to the frame  10  of the robot  1 . Therefore, the robot does not need to be connected up to a power supply by electrical cable. 
     At least one wheel, for example a guided wheel  14 , is connected to a steering device  20 . 
     The robot  1  is therefore able to move forwards, backwards, to the right and left. 
     According to an advantageous embodiment, these movements are controlled by a remote control handset via a CPU  22  fitted to the robot frame. 
     In one possible embodiment, the robot is fitted with at least one permanent magnet  30  capable of magnetic interaction with the resting surface  2 , so as to couple the robot to said surface. 
     The permanent magnet  30  is fitted so as to graze the resting surface  2 . In other words, the magnet  30  is detached from the ferromagnetic surface  2 , but is kept at a pre-set distance, able to generate a magnetic force of attraction such as to enable the robot  1  to remain sturdily anchored to the resting surface  2 , whatever its direction or motion. 
     In order to maximize the density of the magnetic field acting on the resting surface  2  and therefore the force of attraction, the magnet  30  is fitted with one of its poles facing the resting surface  2 . In other words, the axis of the two poles of the magnet  30  is perpendicular to the surface  2 . 
     Clearly, the factors which determine the intensity of the magnetic field between the at least one magnet  30  and the resting surface  2 , i.e. the distance between the magnet and the surface, the type, shape and size of the magnet, will be chosen on the basis of the application, the travel of the magnet, the weight of the robot (plus any load such as a probe). 
     In a particularly advantageous embodiment, at least one magnet  30  is fitted onto a support  32  which is allowed to oscillate freely so that the magnet is always oriented in the position of minimum distance from the resting surface, that is in the position of maximum field density. 
     Preferably, magnets  30  are fitted close to the points of contact between the robot  1  and the resting surface, i.e. close to the wheels  12 ,  14 . 
     In the illustrated embodiment, the robot is fitted with a couple of driving wheels  12  and a couple of guided wheels  14 . 
     In accordance with a preferred embodiment, the robot  1  is fitted with four supports  32 , for example comprising essentially parallelepiped blocks, each carrying several magnets  30 . Each magnet is, for example, disc or tablet shaped, and has surfaces parallel to the resting surface of the robot. The blocks  32  are advantageously fitted to the rotating shafts  13 ,  15  of the wheels  12 ,  14 . Each block  32  is fitted with ball bearings  34  to enable free rotation around the shaft to which it is fitted. The ball bearings  34  are fitted to the support  32 , for example by seeger  35 . 
     In one embodiment, each magnet  30  is fixed or glued to a pillar  36 , cylindrical in form for example, seated in a housing  36  inside the support  32  and held into place by a pin  37 , for example. 
     In one embodiment, the magnets  30  are parallel to each other, for example aligned parallel to the shaft  13 . 
     In one embodiment, the permanent magnets  30  are in neodymium. 
     According to an advantageous embodiment, further permanent magnets  40 , henceforth called supplementary magnets, are fitted into the casing  42  of at least one couple of coaxial wheels, preferably the driving wheels  12 . 
     In one embodiment, these supplementary magnets  40  comprise small cylinders which, when fitted into a wheel, turn the relevant axis parallel to the wheels axis. In a possible embodiment, the wheels  12  include a central cylindrical casing  42 , for example in aluminium, where, around a hole for the rotating shaft  13 , a crown-shaped series of cylindrical housings  43  is created which are fitted with cylindrical magnets  40 . 
     The central casing  42  is fitted between a couple of side disks  44  made of ferromagnetic material with a milled outer surface  44  for contact with the surface  2 . Advantageously, the disks  44  are fixed to the central casing  42  by means of the magnetic field generated by the supplementary magnets  40 . 
     Around the rotating surface  42 ′ of the central casing  42  of the wheel  12  an anti-slip fascia  45 , made of rubber or similar type of material, is fitted. 
     The function of the supplementary magnets  40  is to generate a magnetic field interacting with the resting surface  2  of ferromagnetic material, in order to ensure that the fascia  45  always adheres to resting surface  2 , preferably by exerting optimum pressure on it. In this way the wheels do not slip on the support surface, in particular the driving wheels, even when the surface  2  is damp, for example to facilitate ultra-sound measurements. 
     Advantageously, the fascia  45  is kept in position by two side discs  44 , clamping from opposite sides of the wheel. 
     Clearly, given its position on the wheels, the crown of supplementary magnets  40  acts on the resting surface  2  one magnet at a time, the one closest to the surface as the wheel rotates. This advantageously produces the desired effect of increasing the adherence of the robot to the surface, by preventing the slippage of the wheels, without preventing their proper rotation once they have made contact with the ferromagnetic surface. 
     In terms of the structure of the wheels, the central casing  42  of the driving wheels  12  and/or the casing  50  of the guide wheels  14  has a multi-faceted rolling surface, i.e. a polygonal shape able to improve the anti-slip effect still further. 
     On the casing  50  of the guide wheels  14 , for example, a tooled tyre  51  can be fitted. 
     In accordance with the embodiment illustrated in  FIGS. 7-10  and with the invention, the robot has a frame  100  with longitudinal axle  101  connecting two transverse axles  102  for the purposes of sliding along the ferromagnetic surface to be inspected. The longitudinal axle  101  has an articulated joint  104  enabling the two transverse axles  102  to rotate independently of the longitudinal axle. This enables the robot to move along uneven or rough surfaces, for example along weld lines to be checked, without losing adherence, as shown in  FIG. 10 . 
     In accordance with a preferred embodiment, near each wheel  107  of the robot, each axle  102  is fitted with a permanent magnet  106 . The wheel  107  may advantageously include supplementary magnets and/or may be fitted with a tyre and/or multi-faceted rolling surface, as described above in relation to  FIGS. 5 and 6 . 
     Every wheel  107  is fitted to the end of a rotating shaft  108 , for example by means of a clamping pin  109 . A support flange  110  for at least a ball bearing  112  extends axially and inwardly from the wheel  107 . On the bearing  112  an oscillating support  114  is fitted for at least one permanent magnet  106  coupling the robot to the resting surface. 
     This support  114  has a cavity underneath where the permanent magnet  106  is fitted, for example, by pressure, with one of the two opposing poles facing the ferromagnetic surface. In accordance with one embodiment, this magnet  106  is rectangular, longer and wider than thick, and with the largest surfaces parallel to the ferromagnetic surface. The face of the permanent magnet facing the sliding surface is kept at such a height that it grazes said surface without being in actual contact. 
     In accordance with a particularly advantageous embodiment, the support  114  for the magnet  106  is in contact with the sliding surface via a roller  116 , or preferable two rollers, for example made with ball bearings. Clearly, through this double support given by wheel  107  and rollers  116 , the magnet is enabled to be as close to the ferromagnetic surface as possible, without the risk of making contact. 
     In other words, the rollers  116  act, together with the wheel, as spacers guaranteeing a slight distance between the magnet and the ferromagnetic surface. 
     For the transverse axles  102  to rotate about the longitudinal axle of the frame whilst at the same guaranteeing that the wheels and rollers adhere to the sliding surface, the shaft  108  must be capable of tilting in relation to the wheels  107  and the oscillating support  114  of the magnet. 
     For this purpose, in accordance with a particularly advantageous embodiment, the axial housing  120  for the rotating shaft  108  which crosses the flange  110  of the bearing support has a conical shape, widening towards the inside, allowing the shaft  108  to tilt in relation to the flange axis. 
     In accordance with one embodiment, the support  114  of the magnet has an axial portion  114 ′ extending towards the inside, beyond the bearing, so as to house a magnet  106  which is longer than the bearing width. A slot-shaped aperture  122  provided in said axial portion  114 ′ receives the rotating shaft  108  allowing the shaft to oscillate in relation to the support. 
     In accordance with one embodiment, the end  108 ′ of the rotating shaft to which the wheel  107  is fitted has a rounded outer surface, for example ogival, so it can oscillate inside the axial hole of the wheel  107 . 
     Advantageously, the wheel  107 , flange  110  and support  114  of the magnet are clamped together along the axis by an outer washer  124 , attached to the wheel  107  and screwed tight to the end of the rotating shaft  108  and an inner washer  125 , around the rotating shaft and pressed against the magnet support, for example by a spring  126 . 
     Therefore, the wheel, flange with bearing and magnet support are pack-assembled in order to make a single wheel unit with the magnet in position hovering over the sliding surface. 
       FIGS. 11 and 12  show another embodiment of an oscillating support  150  for at least one magnet  152 . This embodiment is particularly suitable for applications with small diameter pipes, for example diameters of less than meter, where the robot must be compact. A single oscillating support  150 , in this embodiment, is fitted centrally to at least one of the two rotating shafts of the wheels. 
     The support  150  includes a prism-shaped casing  154 , with a face turned to the sliding surface in which there is a housing  156  for at least one permanent magnet  152 , arranged, as described before, with one pole turned to the ferromagnetic surface to be inspected. Preferably, the magnet  152  is rectangular or bar-shaped and fitted horizontally, for example, pressed into the housing  156 . 
     Contact between the support  150  and sliding surface is by means of lateral rollers  158 , for example two for each end of the support, preferably fixed to the appendices outlining the housing  156  of the magnet. These rollers  158  act as spacers similarly to the description above for the support element  114 . 
     To provide oscillation, the support  150  is fitted to the rotating shaft by means of a couple of bearings  160 , seated in respective housings  162  clamped to the support casing, for example, by a seeger  163 . 
     In accordance with an advantageous embodiment, the bearings  160  are of the oscillating type, in order to allow the rotating shaft, in this case too, to oscillate, albeit less than in the previous example with the dual oscillating support for each transverse axle. 
     The robot according to the invention is particularly suitable for carrying a probe for the purposes of carrying out the non-destructive testing of weld lines and the seal of metal plating, for example carbon steel. In particular, the robot  1  is designed for applications involving cylindrical sheeting (for example tanks of great length or large diameter) made by calendaring and welding flat sheeting. It should be noted that, for ultra-sound probes to work to best effect, these metal sheets need to be damp. 
     The robot is hooked up to the sheeting to be inspected via a permanent magnetic field generated by magnets at some distance from the sheeting and hence without impeding the rotation of the wheels, as occurs in prior art robots. Therefore a powerful motor is not required. A small motor reduction gear is sufficient, powered by a 12 V battery. 
     The disposition of the magnets  30 ,  40 ,  106 ,  152  allows the robot to climb vertically with its load, and to rotate through 180° without losing adherence, even on a damp and slippery surface. 
     Since the robot, according to this invention, does not require power cables for its movement, data from the probes can advantageously be transmitted in wireless mode. Therefore, the robot  1  is completely free-standing, compact and easy to handle. 
     According to this invention, largely due to the reduced weight of the motor, the robot has an overall weight (including the power battery) of less than 15 Kg, well below the regulatory maximum for weights to be lifted by operators (30 kg for men, 20 kg for women). 
     The proposed robot is therefore very simple and easy to use and transport. 
     A person skilled in the art may, according to specific needs, modify, adapt or replace some elements with others of similar or identical function, without departing from the scope of the claims below. Each of the features described for a particular embodiment can be incorporated irrespective of the other forms of embodiment described.