US 20040020084 A1
The invention concerns a method for automatically moving on the ground a tool mounted at the end of an articulated arm. It consists in bringing the tool (7, 17, 27) onto a first point of the surface and in calculating the co-ordinates of said point; in bringing the tool onto a second point enabling to set a first axis of co-ordinates of the working plan and to determine the furthermost point to be reached on said axis; in bringing the tool onto a third point close to the second co-ordinate axis and enabling to define the position of the frame of reference of the working plan, then in a fourth point delimiting the zone plane inside which the work will be performed and in defining a working plan for the tool capable of being superimposed with the working surface so as to enable it to cover, by discontinuous or continuous movements, the entire working surface.
1. A method for automatically moving over an area of ground, a tool that is mounted at the end of an articulated arm, characterized in that it consists in defining and calculating a surface known as the working surface from several successive touchings of the tool onto the ground, then in moving the tool (7, 17, 27) over the working surface.
2. The method as claimed in
3. The method as claimed in
4. The method as claimed in one of claims 2 and 3, characterized in that it consists in defining a working pattern in which the points reached later by the tool (7, 17, 27) are arranged in two perpendicular directions in a sequence such that a step characteristic of the shape of the head of the tool in one direction is followed by a step characteristic of the size of the head of the tool in said direction.
5. The method as claimed in one of
6. The method as claimed in
7. The method as claimed in one of claims 5 and 6, characterized in that during the work on a surface, the computer (10) stores in memory the various points reached by the tool, and any points of the surface which might not have been reached, so as to work on them later.
8. A device for automatically moving over an area of ground, a tool mounted at the end of an articulated arm, for implementing the method as claimed in one of
9. The device as claimed in
 The subject of the present invention is a method for automatically displacing, over an area of ground, a tool mounted at the end of an articulated arm, and to a device for implementing it.
 The articulated arm equipped with the tool may, for example, be the arm of a motorized shovel, mounted to pivot about a vertical axis on the chassis of the vehicle.
 When an operator needs, using a tool mounted at the end of such an arm, to work on a very precise area of ground, he runs into difficulties in that he manually commands the displacement of the tool, and is situated a significant distance, of the order of 5 to 6 m, away from the tool and does not always have an accurate view of the area in which the tool is working. It is therefore not easy, particularly taking account of the play in the articulation of the various elements of the arm, to displace the tool over the surface that is to be worked in such a way as to leave no region of the ground unworked.
 It is important for work on an area of ground to be very systematic in certain applications, such as the search for antipersonnel mines that may be buried in the ground. Making the ground safe entails leaving no surface unreached by the detection tool.
 The object of the invention is to provide a method which allows the working of the ground to be made systematic, so as to avoid leaving unworked areas.
 To this end, the method for automatically moving over an area of ground, a tool that is mounted at the end of an articulated arm, to which it relates, consists in defining and calculating a surface known as the working surface from several successive touchings of the tool onto the ground, then in moving the tool over the working surface.
 Furthermore, this method consists, after defining the working surface, in defining a working pattern for the tool that can be superposed with the working surface so as to allow it, through discontinuous or continuous displacements, to cover the entire working surface.
 According to one embodiment, this method is characterized in that it consists in bringing the tool onto a first point of the surface and in calculating the coordinates of this point which is considered to be the point of origin of the working pattern, in bringing the tool to a second point to orient a first axis of coordinates of the working pattern and to determine the furthest point to be reached along this axis, in bringing the tool to a third point near the second axis of coordinates to define the position of the frame of reference of the working pattern, then to a fourth point delimiting the region of the plane within which the work will be carried out.
 According to another feature, this method consists in defining a working pattern in which the points reached later by the tool are arranged in two perpendicular directions in a sequence such that a step characteristic of the shape of the head of the tool in one direction is followed by a step characteristic of the size of the head of the tool in said direction.
 Advantageously, the method according to the invention consists in controlling the various movements and displacements of the tool using a computer. This allows the operator's task to be made easier and allows him to reach regions which are not always directly in his sight.
 In practice, this method consists in supplying the computer with the coordinates of the four points, from which the computer defines a process of displacement of the tool over the entire working surface and controls the members which displace it.
 However, the operator may, at any time, interrupt the operating and displacement cycle of the tool to control it manually.
 According to another feature of the invention, during the work on a surface, the computer stores in memory the various points reached by the tool, and any points of the surface which might not have been reaached, so as to work on them later.
 According to another possibility, the operator can select a working area which is reached directly and automatically independently of the performing of the working pattern commanded by the computer.
 A device for implementing this method comprises a carrier vehicle, on the chassis of which a turret is mounted to pivot about a vertical axis, this turret being equipped with an arm consisting of several elements articulated about horizontal axes and at the end of which a tool is mounted, the turret comprising an angular sensor determining the angle it makes with the chassis and each element of the arm comprising an angular sensor supplying its inclination with respect to the horizontal.
 In a frame of reference attached to the chassis, two axes of which are situated in a horizontal plane, it is possible to calculate the coordinates of the end point of the tool with knowledge, on the one hand, of the distances between the articulation axes of the various elements of the arm and, on the other hand, of the angle that each element makes with respect to the horizontal. The angle formed by the main direction of the tool with respect to the ground is chosen by the operator, according to the terrain, and maintained throughout the phase of work. When this is the case, it is possible to calculate the angles of the turret with respect to the chassis and of the articulated elements with respect to the horizontal, with knowledge of the coordinates of the end point of the tool. Thus, calculated angular values correspond to each of the points in the space that can be reached by the end of the tool.
 According to another feature, this device comprises a computer equipped with a program for controlling the displacement of the tool to cover the surface that is to be made safe, this computer receiving the values supplied by the various angular sensors and delivering at output electrical signals that control electrical directional control valves hydraulically powering the motor that turns the turret and the various rams that actuate the elements of the arm until the angular values are equal to the calculated values.
 In any event, the invention will be clearly understood with the aid of the description which follows, with reference to the appended diagrammatic drawing which, by way of nonlimiting examples, depicts several embodiments of a device for implementing this method for working an area of ground:
FIG. 1 is a perspective view of a device intended to make an area of ground safe;
FIG. 2 is a view thereof from above;
FIG. 3 is a view of a diagram for controlling the tool;
FIG. 4 is a view of a diagram of the displacement of the tool over the ground;
FIG. 5 is a view of a second tool, consisting of a one-footed vibrating device;
FIG. 6 is a view of a diagram of the displacement of this tool over the ground;
FIG. 7 is a view of the end of the arm of a device, equipped with a metal detector;
FIG. 8 is a view of a diagram of the displacement of this metal detector with respect to the ground.
FIG. 1 depicts a carrier vehicle 2 comprising a chassis 3 mounted on wheels and able to be stabilized horizontally by stabilizing rams 4. Mounted on the chassis 3 is a turret 5 which can pivot about a vertical axis A. The turret comprising an angular sensor C1 which makes it possible to determine the angle formed by the turret with respect to the chassis. Articulated about a horizontal axis A2 to the turret is an arm 6 consisting of three elements 6 a, 6 b and 6 c, the element 6 b being articulated to the element 6 a about a horizontal axis A3 and the element 6 c being articulated to the end of the element 6 b about an axis A4. The elements 6 a, 6 b and 6 c are equipped respectively with angular sensors C2, C3 and C4 to determine the angle that each element makes with the horizontal.
 Fixed to the end of the element 6 c is the tool 7 which comprises parallel rods 8 each equipped, at its lower end, with a foot 9 for resting on the ground. The tool 7 is also equipped with a device for vibrating the rods 8 and the feet 9, which device is known per se and not depicted.
 In a frame of reference attached to the chassis, two of the axes, X and Y, of which are placed in a horizontal plane, it is possible to calculate the coordinates of the end point of the tool with knowledge, on the one hand, of the lengths of the various elements 6 a, 6 b, 6 c and of the angles at the axes A1, A2, A3 and A4. In the embodiment depicted in the drawing, the vertical axis corresponding to the axis of rotation of the turret is defined by the reference Z.
 As shown in FIG. 3, the device according to the invention is equipped with a computer 10 receiving the signals representing the angular values of the sensors C1, C2, C3 and C4. At output, the computer delivers electrical signals controlling electrical directional control valves E1, E2, E3 and E4 powering the motor 12 that turns the turret 5, and rams 13, 14 and 15 that drive the respective elements 6 a, 6 b and 6 c, respectively.
 In practice, the operator displaces the tool until he makes the end point of the tool coincide with a point he has chosen on the surface of the ground that is it to be worked. Using the angular values measured in this position, the coordinates of the point are calculated in the origin frame of reference of the machine and stored in memory. This operation is carried out four times in succession. The first point thus determined is the point of origin of the working pattern. The second point orients the first axis of coordinates of the working pattern and determines the maximum point to be reached along this axis. The third point determined, and close to the second axis of coordinates, makes it possible to define the position of the frame of reference of the working pattern, and the fourth point delimits the area of the plane within which the making-safe work will be performed.
 It is understandable that all the coordinates of the points of the working pattern are known and therefore that all the points of the pattern situated inside the determined working region can be reached in succession by the tool.
 By way of example, the computer will, from software using parameters such as the number of feet, the size of the feet in two rectangular directions and the space in between two feet, control a working pattern.
 In the example depicted schematically in FIG. 4, the feet are square and there are six of them. The six feet are placed in a corner of the working surface by a command from the computer. This is the position centered on the point 0. Once the feet have been vibrated, they are displaced along the X-axis by a first step P1 corresponding to half the dimension of one foot. The feet occupy the position, defined in chain line, and the feet are centered on the point 1. In this second position, the feet cover the spaces which were delimited between the feet, in the position 0, which spaces were oriented parallel to the Y-axis. All the feet are then displaced by a step P2, still along the X-axis, by a value equal to 2.5 times the size of all of the feet in the X-direction. The feet are centered on the point 2. After vibrating, they are displaced by the value of the first step P1, that is to say half the size of one foot, to bring them into position 3 and so on along the X-axis. The same procedure is followed along the Y-axis, it thus being possible for the entire surface to be covered, without leaving any region unexplored, by successive displacements with two different step sizes.
 This displacement is preferably automated and controlled by the computer, as mentioned earlier. The computer stores in memory those regions which have been reached by the tool, and possibly regions which might not have been reached, particularly as a result of the displacement of the tool perhaps not being perfectly linear in both directions, given the rotation of the turret. In order to obtain perfect linearity of the displacement of the tool in both directions it would be possible to envision the tool having an additional degree of freedom, allowing it to rotate about a vertical axis about the element 6 c, in order to keep it perfectly parallel to itself as the turret turns on the chassis.
FIG. 5 depicts a second device, of which only the end of the arm is depicted in the drawing, and which differs from the previous device in the form of the tool. In this second device, the same elements are denoted by the same references as previously. In this device, the tool 17, also intended for making the ground safe, comprises one foot 19 mounted at the end of a bar 18. This foot 19, having been rested on the ground, can be set in vibration in a way known per se. FIG. 6 shows the working pattern for the tool on the ground. In this case also, the computer defines, in the two directions X and Y, points on which the tool must come to rest in succession as it is displaced over the ground. Given that there is only one foot, in this instance, the step with which the foot is displaced both in the X and Y directions, corresponds to a length shorter than the dimension of the foot in the direction considered. It may be noted that, in FIG. 6, a slight pivoting of the foot is depicted to take account of the rotation of the turret on which the arm is mounted. However, the computer modifies the angular position of the arm so that in spite of the pivoting of the turret, the points defined by the working pattern remain aligned.
FIG. 7 depicts a device in which the same elements are denoted by the same references as previously. In this device, a tool 27 is equipped with a metal detector 29 borne by a bar 28. As shown in the drawing, the lower end of the bar 28 protrudes from the metal detector to allow it to rest on the ground, particularly to delimit the working plane.
 As shown in FIG. 8, for determining the working pattern, the surface taking into consideration is the square 30 inscribed inside the circular detector 29. The displacement of the detector occurs with a step, in either one of the two directions X or Y, which is shorter than the dimension of the side of the square 30, so that there is a region of overlap between one position and the next. While the detector can be displaced stepwise, it is also possible to perform continuous displacement, especially if the metal detector does not rest on the ground but follows the surface thereof from a distance.
 As is evident from the foregoing, the invention provides a vast improvement to the existing art by allowing automation of the area of ground using a tool, making the working of this entire area systematic.
 As goes without saying, the tool could be other than those described above, without thereby departing from the scope of the invention.