WO2009016229A1 - Articulated pantograph device - Google Patents

Abstract

Articulated device with three degrees of freedom in translational movement having an active end (6) intended to interact with an external environment, a first pantograph (100) and a second pantograph (200) which are combined in series, the first pantograph (100) being acted upon directly at one of its ends (A1, B1) by a linear actuator (110), the second pantograph being acted upon at two of its ends (A2, B2, M2) by two actuators, the first (110), second (210) and third actuators each having a direction of travel (Y, X, Z) that is orthogonal to the other two directions of travel, the active end being supported by one end (M1) of the first pantograph in such a way that the relationship connecting the movement of the active end in each of the directions of the actuators and the movement of each of the actuators is invariable.

Description

 ARTICULATED PANTOGRAPHER DEVICE

DESCRIPTION

TECHNICAL FIELD AND PRIOR ART

The present invention relates to an articulated device, in particular an articulated arm offering three degrees of freedom in translation, which can be implemented in a haptic interface or a robot manipulator.

A haptic interface comprising three parallel pantographs connected at one end with a handle that can be manipulated by an operator is known from the document "A pantograph linkage Parallel Platform Master Hand Controller for Force-Reflection", G. L Long and C. Collins, pages 390 -395 in Proceedings of 1992 IEEE International Conference on Robotics and Automation, Nice, France - May 1992. The ends of the pantographs opposite to that bearing the handle are connected to a mechanical transmission. The interface described in this document is a six degrees of freedom interface, comprising three pantographs in parallel, whose ends are fixed to a frame. This interface (Generalized Master Controller in English terminology) is, by construction, well adapted to rotational movements, but does not allow to perform translations of large amplitude. In addition, nothing assures the homogeneity of the movements according to the different degrees of freedom from the control of the different actuators.

US 4,437,635 discloses a device for handling a tool, this device comprises an arm formed by two pantographs in parallel, a common end carries a tool and the other ends are integral with linear actuators in three orthogonal directions from space. The purpose of using the two parallelograms in parallel here is to keep the orientation of the tool constant. A first actuator moves one end of each pantograph, a second actuator moves the other end of the pantographs. The third actuator supports the second actuator, the inertia of displacement in this direction is then greater, and the friction is increased.

A robot comprising a single pantograph is also known from US 4 904 152, one of the three linear actuators also carrying one of the other two actuators.

It has been proposed, in particular to solve this problem, a parallel robot called "orthoglide" comprising three fixed linear actuators moving articulated arms connecting to a working end.

However, the relation connecting the linear movement of the actuator and that of the working interface is not invariable as a function of the position of the working interface. It is therefore an object of the present invention to provide an articulated device for manipulator or haptic interface with three degrees of freedom in translation, having an invariable linear relationship between the position of each actuator and that of the working interface, allowing to have a homogeneity of the behavior of the device in the three directions of the space. A second object of the invention is to provide an articulated device actuated from fixed actuators to minimize the moving masses.

The use of a simple pantograph deformable parallelogram seems interesting, but does not solve all these problems simultaneously, for a system with three degrees of freedom, as we will now explain in relation to Figures 1 to 4 representing devices of the state of the art.

In the remainder of the present application, a pantograph with deformable parallelogram shown in FIGS. 1 and 2 is defined as a four-bar mechanism (AD, DM, CB, BE) plane, the properties of which are well known. In particular, the segments CD, DE, EB and BC form a parallelogram (CD = BE, CB = DE) and the points A, B and M are aligned, so that the point M performs a linear trajectory according to the movements of A or B. By construction of the parallelogram, we have:

This report is named. The lengths of each bar are fixed. It is later assumed that k is greater than 1 (A and C are not merged). The external connection points (port) are points A, B and M.

When deforming the parallelogram by actuating the joints between the bars, the pantograph deforms in its plane, while checking the following geometrical relations between the moving points with respect to each other:

JD ^~ DM JD + ^~ DM, AC FROM AC + FROM

Since DE = CB we deduce _r - _{== r} - = k

AC + CB hence the relation AM = kAB of the pantograph between the moving points A, B and M.

The relative displacements of the points A, B and M are linked by the following relation: d ^~ M -d ^~ Ak {dB-dA) = Z

dM -ItJB - (I - k) dλ = 0 _(eq .i)

The displacements of two of the points among (A, B, M) define the displacement of the third. Considering M the point usually chosen at the exit, the displacements of the point M (dM) _SO are homothetic of those of the point B {dB) with a ratio equal to k. The displacements of the point M (dM) _SO nt also homothetic to those of the point A (dA) _w ith a ratio of 1-k. This ratio is negative since k is greater than 1, which results in a turnaround of the figure as shown. If we divide the equation (eq.l) by k we get:

1 - - → C \ - k} - ^• - -dM - dB - ± - - ¹ - JA = O kk

In this case, the movements of B are connected to those of M by the ratio 1 / k: this corresponds to the inverse or reducing mode.

We also note that if dB = dA = d then dM = d. Subsequently, to simplify the writing dM will be noted M.

Such a pantograph can be actuated from the point B, with the point A held fixed (see Figure 1), with a ratio of homothety between the relative displacements of the point B and the point M equal to k: it is the usual use of the pantograph as an enlarger. The pantograph can also be actuated from the point A, with the fixed point B, as shown in FIG. 2, with a homothetic ratio of 1-k between the relative displacements of the point A and the point M. The actuations from point A and point B can be combined to provide motion with three degrees of freedom.

We recall that the aim of the present invention is to provide a spatial mechanism with three degrees of freedom whose movements of the exit point M (M is chosen for the rest of the sequence) are linearly related to the movements of the entry points A and B and whose actuators are fixed, for example on a frame.

In order for one of the connection points of the pantograph to have three independent degrees of freedom in space, it suffices to apply to the set of the other two points movements in three directions independent of space. We will note ©, © and © these three directions, that is to say the direction of the three actuators.

It should be noted that it is not necessary to choose directions in space. They are interchangeable. Moreover, whatever the displacements of A and B in space the points A, B, C, D, E, M remain coplanar. But this plane can turn around the right AB without changing the position of M.

There are several possible ways to divide the three translational movements in well defined directions at points A and B. Note P (Φ) the displacement of the point P in the direction

©, resp. P (@) and P (®) following the directions © and (D.

1) © in B, © and © in A then

M = k.B ()) + (l-k). (A ()) + A ()))

2) © in A, © and ® in B so M = (l-k) .A (©) + k. (B (©) + B (®))

3) ©, © and © in A then

M = (l-k). (A (Φ) + A ()) + A ()))

4) ©, © and © in B then

M = k. (B (Φ) + B (©) + B (®)) Cases 3) and 4) that consist of moving a single point in three independent directions with actuators connected directly to the base are not feasible simply.

For example, in Figure 3, we chose to apply a displacement along a single axis (axis ©) at point B and along two perpendicular axes (© and ©) at point A.

A displacement of amplitude 1 along the axis © of B produces a displacement of amplitude k along the axis © of M. An amplitude displacement 1 along the axis ((respectively the axis (D) of A produces a displacement of amplitude - (k-1) along the axis ((respectively, the axis (D) of M. Which will mean that the motion will be reversed between the actuator and the active end and M. In the standard configuration of a pantograph as shown in Figure 3 with an actuator along the axis © at point B and two actuators along the perpendicular axes © and © placed at point A, it remains to provide a means for the actuators © and © to be fixed, and that the displacements of the point M have the same ratio of homothety in the three directions ®, © and ®.

Similarly, in FIG. 4, we chose to apply a displacement along a single axis (axis)) at point A and following two perpendicular axes (et and (D) at point B.

A displacement of amplitude 1 along the axis © of A produces a displacement of amplitude - (k-1) along the axis © of M. A displacement of amplitude 1 along the axis © (respectively the axis ( D) of B produces a displacement of amplitude k along the axis © (respectively the axis (D) of M.

None of the cases illustrated in FIGS. 3 and 4 therefore makes it possible to distribute three degrees of freedom over two operating points of a single pantograph and to obtain a homogeneous displacement (with the same coefficient of proportionality) in the three directions.

In order to remedy the problem of inhomogeneity, it has been proposed actuators using different adapted reducers, to compensate for the difference in ratio between the movements applied in A and those in B, and to obtain homogeneous movements in three dimensions at the point M.

The object of the present invention is therefore to provide a three-dimensional device of freedom of movement offering a homogeneous movement in the three degrees of freedom and with low inertia. STATEMENT OF THE INVENTION

The previously stated goal is achieved by a device with three degrees of freedom in translation comprising at least two pantographs in series, the first pantograph carrying at one end an active member or working interface, the latter being movable in a first direction by a first actuator directly requesting the first pantograph, the second pantograph being directly connected to the first pantograph and biased directly in a second direction by a second actuator and in a third direction by a third actuator. In other words, the invention consists in moving a working end carried by a first pantograph connected directly to a linear actuator in a first direction, and transmitting the movements in the other two directions forming with the first direction three orthogonal directions by means of a second pantograph itself connected directly to a linear actuator in a second linear direction perpendicular to the first, the movement in the third direction being obtained by a third actuator.

The actuators are then fixed, for example on an external frame and mechanically independent, i.e. no actuator is carried by another actuator.

Moreover, it is possible to simply connect by a relation expressed by a linear function, the displacement of the active end to that of each actuator, as a function of the connection points of the pantographs with each other and of the homothety ratios. of each pantograph, this relation being invariable regardless of the position taken by the active end.

Such a structure makes it possible to minimize the size and the torque of each actuator, to use the same type of actuator for each direction and to reduce the total weight of the structure. In a particularly advantageous manner, the third actuator is a third pantograph connected directly to the second pantograph and biased directly in a third direction by a third actuator, which allows choosing the connection points between the pantographs and the homothetic ratios of each of the pantographs to link the displacement of the active end to that of each of the actuators by identical relations.

Under these conditions, an identical displacement of each of the actuators ©, © and © will cause an identical displacement of the active end in each of the directions Φ, © and (D.

Several combinations are thus possible, and are within the scope of the present invention.

The amplitude of the displacement of the active end of the articulated device according to the invention in the three independent directions of the three actuators depends on the homothetic ratio of each pantograph, the location of each actuator on each pantograph, ie according to the point the pantograph to which it is connected, and the articulation of the pantographs between them.

It is particularly desirable that the homothetic ratio be the same in the three independent directions. This is made possible by using a third pantograph as the third actuator. Indeed, with the aid of the first two pantographs in series, a first mechanism is made to independently actuate the two points of the first pantograph distinct from the active end in two directions with the same ratio of homothety and uses a third pantograph to make the third ratio of homothety equal to the ratios of homothety in the other two directions. If only two pantographs are used, and the homothety ratio is fixed in one direction, we can not make the homothetic ratios in the other two directions simultaneously equal to the first one. report, by fixing two actuators on the same pantograph, at two distinct points of the second pantograph.

The present invention therefore mainly relates to an articulated device with three degrees of freedom in translation comprising an active end intended to interact with an external environment, a first pantograph and a second pantograph associated in series, the first pantograph being solicited directly at the level of one of its ends by a linear actuator, the second pantograph being biased at two of its ends by two actuators, the first, second and third actuators each having a direction of displacement orthogonal to the other two directions of displacement, the end active being carried by one end of the first pantograph, so that the relationship linking the movement of the active end in each of the directions of the actuators and the displacement of each of the actuators is invariable. The third actuator may be a pantograph itself biased at one end by an actuator, said third actuator.

The third point of the second pantograph may be connected to the first point of the first pantograph which is not solicited directly by the first actuator, and the third point of the third pantograph may be connected to the first of the second pantograph which is not directly requested by the second actuator.

The pantographs advantageously have homothetic ratios which are linear or rational functions of each other, so that the displacement of the active end is proportional to the displacement of each of the actuators with a coefficient of proportionality equal in modulus in the three directions.

In an exemplary embodiment, the first pantograph having a homothety ratio equal to kl, the first actuator being connected directly to the second point of the first pantograph, and the second actuator being connected directly to the second point of the second pantograph, the second pantograph k has a homothetic ratio k2 equal to - so that

the linear functions connecting the displacement of the active end to that of each of the first and second actuators have the same coefficient of proportionality equal to kl in module.

The third pantograph can then be connected by its third point to the first point of the second pantograph, the third actuator being connected to the first point of the third pantograph, the second point being fixed, and the third pantograph can have a homothetic ratio k3 equal to (kl + 1) so that the linear functions connecting the displacement of the active end of the first pantograph to that of each of the first, second and third actuators have the same coefficient of proportionality equal to kl in module.

Alternatively, the third pantograph is connected by its third point to the first point of the second pantograph, the third actuator being connected to the second point of the third pantograph, the first point of the third pantograph being fixed, and the third pantograph can have a report of homothety k3 equal to kl so that the linear functions connecting the displacement of the active end of the first pantograph to that of each of the first, second and third actuators have the same coefficient of proportionality equal to kl in module.

In another embodiment, the first pantograph having a homothetic ratio equal to k1, the first actuator being connected directly to the second point of the first pantograph, and the second actuator being connected directly to the first point of the second pantograph, the second

pantograph has a homothetic ratio of k2 equal to - ^ - ^ - - so that

the linear functions connecting the displacement of the active end of the first pantograph to that of each of the first and second actuators have the same coefficient of proportionality equal to kl in module.

The third pantograph can be connected by its second point to the second point of the second pantograph, the third actuator being connected to the third point of the third pantograph, the first point A3 of the third pantograph being fixed, the third pantograph advantageously

a homothetic ratio k3 equal to - ^ - ^ - - so that the functions

K linear connecting the displacement of the active end of the first pantograph to that of each of the first, second and third actuators have the same coefficient of proportionality equal to kl in module.

In the case where the third pantograph is connected by its second point to the second point of the second pantograph, the third actuator being connected to the first point of the third pantograph, the third point of the third pantograph being fixed, the third pantograph has

advantageously a homothety ratio k3 equal to - - so that

that the linear functions connecting the displacement of the active end (Ml) to that of each of the first, second and third actuators have the same coefficient of proportionality equal to kl in module.

In another example, the first pantograph has a homothety ratio equal to kl, the first actuator being directly connected to the first point, and the second actuator being connected directly to the first point of the second pantograph, and the second pantograph having a ratio of homothety

equal to - ^ - ^J - - so that the linear functions connecting the

K displacement of the active end of the first pantograph to that of each of the first and second actuators have the same coefficient of proportionality equal to (k _ι -1) in module. The third pantograph can be connected by its second point to the second point of the second pantograph, the third actuator being connected to the third point of the third pantograph, the first point being fixed, the third pantograph advantageously has a homothetic ratio k3 equal to

- - so that the linear functions connecting the displacement of

(* i - l) the active end of the first pantograph to that of each of the first, second and third actuators have the same coefficient of proportionality equal to (^ ₁ -1) in module.

The third pantograph can be connected by its second point to the second point B2 of the second pantograph, the third actuator being connected to the first point of the third pantograph, the third point being fixed, the third pantograph has in another example a homothetic report k3 equal

(2I ₁ - I) so that the linear functions connecting the displacement of

(* l) the active end of the first pantograph to that of each of the first, second and third actuators have the same coefficient of proportionality equal to (k _ι -1) in module.

In an exemplary embodiment, the second and third pantographs are arranged next to each other, the first pantograph extending away from the second and third pantographs. The connection connecting the first and the second pantograph can be performed by means of a gimbal.

At least one of the first, second and third linear actuators may be of the pulley type, having a first and a second pulley of parallel axes around which is wound an endless flexible transmission member and a moving integral carriage of said transmission element, said carriage being connected to the at least one pantograph, the rotation in one direction of rotation or in another of the pulleys, causing the linear displacement of the carriage in the direction connecting the two pulleys.

The pulley actuator may include a guide rail extending between the two pulleys and on which a sole of the carriage is slidably mounted.

The present invention also relates to a robot manipulator comprising at least one articulated device according to the present invention.

The present invention also relates to a haptic interface comprising at least one articulated device according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the following description and the accompanying drawings, in which: FIG. 1 is a block diagram illustrating the conventional use of a deformable parallelogram pantograph as a drawing enlarger,

FIG. 2 is a block diagram illustrating the inverted operation of a deformable parallelogram pantograph, the fixed point of the parallelogram being different from that of the parallelogram of FIG. 1,

FIG. 3 is a block diagram illustrating the inhomogeneity of the movements of a pantograph with three degrees of freedom when an actuator is directly connected to one point of the pantograph and the two other actuators are directly connected to another point of the pantograph. FIG. 4 is a block diagram illustrating the inhomogeneity of the movements of a pantograph with three degrees of freedom, in which the points directly connected to an actuator and to two actuators are reversed relative to the pantograph of FIG. 3; FIG. 5 is a block diagram of a first embodiment of an articulated device according to the present invention comprising two pantographs,

FIG. 6 is a block diagram of a first example of a second embodiment of an articulated device according to the invention, the articulated device comprising three pantographs in series,

FIG. 7 is a block diagram of a second example of the second embodiment of an articulated device according to the invention,

FIG. 8 is a schematic diagram of a third exemplary embodiment of an articulated device with three pantographs according to the invention,

FIG. 9 is a perspective view of an articulated device according to the third embodiment of the present invention seen substantially from the front, where the three actuators are fixed on an external frame,

FIG. 10 is a perspective view of a device similar to that of FIG. 9 according to a second substantially opposite angle of view seen from behind,

FIG. 11 schematically illustrates a part of a device according to a second embodiment of the invention, using a cardan-type link, FIG. 12 is a table summarizing the various possible configurations between three pantographs of the device according to FIG. invention, and the associated homothety ratios,

FIG. 13 is a schematic representation of an exemplary linear actuator that can be used in the articulated device according to the invention; - Figure 14 is a schematic front view of a bidirectional positioner particularly suitable for articulated pantograph device;

FIG. 15 is a perspective view of an articulated pantograph device with the positioner of FIG. 13 and that of FIG. 14. DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

We will now describe in detail several embodiments of the invention in connection with Figures 5-11.

Throughout the following description we will designate by first, second and third points, the three aligned points of a pantograph not worn by the same bar, the second point being arranged axially between the first and the second point.

For example in Figure 5, the first point of the pantograph is the point Al, the second point is the point Bl and the third point the point Ml. In this case, Ml will also be designated the active end of the device since it is this end that will interact with the external environment.

The designation of a multi-pantograph mechanism will be done by the enumeration of the connection points of the pantographs between them.

For example, M1-A1M2-A2M3-A3 designates a three-pantograph mechanism, whose exit point at the first pantograph is the third point Ml, connected by its first point Al to the third point M2 of a second pantograph, even connected by its first point A2 to the third point M3 of a third pantograph, actuated by its first point A3. In Figure 5, we can see a first embodiment of the present invention wherein the articulated device comprises two pantographs 100 and 200 connected in series.

According to the nomenclature described above, this device can be designated M1-A1M2-A2-B2, which means that the device comprises two pantographs 100, 200, the first pantograph 100 homothety report kl whose exit point at Pantograph 1 level is the third point Ml, connected by its first point Al to the third point M2 of the second pantograph 200 of homothetic report k2, itself connected by its first A2 and second B2 points to actuators. The actuators are linear actuators each having a direction of displacement orthogonal to the directions of the other two actuators.

The movements of the points are designated by the letter of the point.

We can write :

M1 = k1B1 + (1-k1) A1 or M1 = k1B1 + (1-k1) M2. When the actuator B1 is actuated, the ratio of homothety is kl. M2 = k2B2 + (l-k2) A2, whence M1 = k1B1 + (l-k1) (k2B2 + (l-k2) A2).

When the actuator B2 is actuated, the ratio of homothety is (l-kl) k2.

When the actuator at A2 is moved, the homothetic ratio of the combination of the pantographs 100 and 200 is: (l-kl) (l-k2).

The actuators are fixed, for example on an external frame and mechanically independent.

With this configuration, it is therefore possible to simply connect in a relation expressed by a linear or rational function, the displacement of the active end M1 to that of each actuator, as a function of the connection points of the pantographs with each other. and ratios of homothety of each pantograph, this relation being invariable whatever the position taken by the active end.

According to a second embodiment, the articulated device comprises three pantographs 100, 200, 300 connected in series.

According to a first category of exemplary embodiments of the invention, the first pantograph comprises a first actuator in a direction © fixed directly to the second point Bi and this first pantograph has a homothetic ratio equal to ki, the second pantograph is connected at first point Ai of the first pantograph. This category of multi-pantographs is designated according to the nomenclature established above of the type: Mi-Ai ...

By symmetry, it is also conceivable a second category of embodiments of the invention, wherein the first pantograph comprises a first actuator directly attached to the point Ai and has a homothetic ratio equal to - (ki-1), and where the second pantograph is connected to the second point Bi of the first pantograph. This category of multi-pantograph is designated according to the nomenclature established above of the type: Mi-Bi ...

We will in the following examples limit ourselves to the first category of examples (Mi-Ai ...), although other embodiments of the invention can be deduced easily, by symmetry, for the category of multi- pantographs type Mi-Bi ...

According to an exemplary embodiment of the invention, illustrated in FIG. 6, the multi-pantograph is of the Mi-AiM ₂ -A ₂ M ₃ -A _{3 type} , the second homothetic ratio pantograph 200 is connected to the first point. Ai of the first pantograph 100 by the third point M ₂ and comprises an actuator in a direction © directly connected to the second point B ₂ . The third pantograph 300 of report K3 is connected to the first point A2 of the second pantograph 200 by its third point M3. The second point B3 of the third pantograph 300 is fixed. This device with three pantographs corresponds to the device with two pantographs of FIG. 5, in which the third actuator A2 has been replaced by a third pantograph 300 connected directly to an actuator in A3.

The relationships established for the device of Figure 5 apply. On the other hand, the homothetic ratio of the combination of the three pantographs 100, 200, 300 when the third actuator is actuated is now equal to (l-kl) (l-k2) (l-k3).

We choose the homothety ratio k ₂ equal to (ki) / (ki-1) so that the linear functions connecting the displacement of the end active M1 to that of each of the first and second actuators have the same coefficient of proportionality equal to ki in module: Indeed k _2. (ki-1) = ki.

According to FIG. 6, the third point M ₃ of the third pantograph is connected to the first point A ₂ of the second pantograph, and the third actuator in a direction est is connected to the first point A ₃ of the third pantograph, the second point B ₃ of the _third third pantograph being fixed. We then choose the homothety ratio k ₃ equal to (ki + 1), so that:

FIG. 7 illustrates a second exemplary embodiment of an articulated device with three pantographs according to the invention, of the Mi-AiM ₂ -A ₂ M ₃ -B _{3 type} . The first two pantographs and their respective actuators are positioned as in the example of Figure 6, with the third point M ₃ of the third pantograph connected to the first point A ₂ of the second pantograph, but the third actuator in a direction © is connected to the second point B ₃ of the third pantograph, the first point A ₃ of the third pantograph being fixed. In this case, one also chooses the ratio of homothety of the second pantograph k ₂ equal to (ki) / (ki-1); on the other hand, one chooses a ratio of homothétie of the third pantograph k ₃ equal to (ki), so that:

(l-ki). (lk ₂ ). (k ₃ ) = ki.

FIG. 8 illustrates a third exemplary embodiment of a triple pantograph according to the invention, of the Mi-AiM ₂ -B ₂ B ₃ -M _{3 type.} The first two pantographs are hinged together as in FIG. 5, but the second actuator is directly connected to the first point A ₂ of the second pantograph. We choose here the homothety ratio k ₂ equal to (2.ki-1) / (ki-1) so that the linear functions connecting the displacement of the active end to that of each of the first and second actuators have the same proportionality coefficient equal to ki in module:

In a particularly advantageous manner, according to this embodiment, the second point B ₃ of the third pantograph is connected to the point B ₂ of the second pantograph, and the third actuator is attached to the third point M ₃ of the third pantograph, the first point A ₃ of the third pantograph being fixed. We then choose the homothety ratio k ₃ equal to (2k _r l) / (ki), so that:

(l-ki). (k ₂ ). (l / k ₃ ) = ki.

According to a variant of this embodiment of an articulated device with three pantographs according to the invention, of the Mi-AiM ₂ -B ₂ B ₃ -A _{3 type} , the configuration of the first two pantographs is identical to that of the third embodiment of FIG. realization, and the third pantograph is also connected by its second point B ₃ to the second point B ₂ of the second pantograph, but the third actuator is attached to the first point A ₃ of the third pantograph, the third point M ₃ of the third pantograph being fixed. We then choose the homothety ratio k ₃ equal to (2ki-1) / (ki-1), so that:

By symmetry, to this first category of described embodiments, it is also possible to conceive a second category of exemplary embodiments of the invention, where the first pantograph comprises a first actuator fixed directly to the point Ai and has a ratio of homothety equal to - (k _r 1), and where the second pantograph is connected to the second point Bi of the first pantograph. This category of multi-pantograph is designated according to the nomenclature established above of the type: Mi-Bi ...

According to an exemplary embodiment of an articulated device with three pantographs according to the invention, of the Mi-BiM ₂ -B ₂ B ₃ -M _{3 type,} the first two pantographs are articulated to each other by a connection between the second point Bi of the first pantograph, and the third point M ₂ of the second pantograph, and the second actuator is directly connected to the first point A ₂ of the second pantograph. We choose here the homothety ratio k ₂ equal to (2.ki-1) / (ki) so that the linear functions connecting the displacement of the active end to that of each of the first and second actuators have the same coefficient of proportionality equal to k _r l in module:

In a particularly advantageous manner, according to this exemplary embodiment, the second point B ₃ of the third pantograph is connected to the second point B ₂ of the second pantograph, and the third actuator is attached to the third point M ₃ of the third pantograph, the first point A ₃ third pantograph being fixed. We then choose the homothety ratio k ₃ equal to (2.k _r l) / (k _r l), so that:

(ki). (k ₂ ). (k ₃ ) = (k _r 1).

According to a variant of the embodiment described above of a triple pantograph according to the invention, the type Mi-BiM ₂ _B ₂ B ₃ -A _{3 /} the first two pantographs are hinged together and actuated in a similar manner the second point B ₃ of the third pantograph is connected to the second point B ₂ of the second pantograph, and the third actuator is attached to the first point A ₃ of the third pantograph, the third point M ₃ of the third pantograph being fixed. We then choose the homothety ratio k ₃ equal to (2.k _r l) / (ki), so that:

(ki). (k ₂ ). (l / k ₃ ) = (ki-1).

The different possible configurations, that is to say not leading to values of negative k, or less than 1 in absolute value, are summarized in the table of FIG. 12. We will now describe in more detail the third example embodiment of the invention.

In Figures 9 to 11, we can see an embodiment of the device according to the third embodiment of the present invention, comprising an articulated member 2 mounted on a frame. The articulated limb 2 has an end 6, called thereafter active end. This can, in the case of a robot manipulator, carry a tool, for example a clamp, or, in the case of a haptic interface, for example carry a handle to control a robot manipulator, for example the type of the invention. The arm comprises three pantographs 100, 200, 300 with deformable parallelograms which will be described successively.

The first pantograph 100 comprises a first pair of arms 102, 104 parallel to each other and a second pair of arms 106, 108 parallel to each other. The arm 102 is rotatably mounted by a first end 102.1 on a first end 106.1 of the arm 106, the arm 104 is rotatably mounted by a first end 104.1 on the arm 106 between the end 106.1 connected to the arm 102 and a end 106.2 free of the arm 106 and forming the active end 6. The arm 108 is, in turn, rotatably mounted by a first end 108.1 on a second end 104.2 of the arm 104, and by a second end 108.2, on the arm 102 between the first end 102.1 and a second end 102.2.

The articulation between the arm 102 and the arm 106 is marked Di.

The articulation between the arm 102 and the arm 108 is marked Ci. The articulation between the arm 104 and the arm 108 is marked Bi.

The articulation between the arm 104 and the arm 106 is marked Ei.

The active end 6 is marked Mi.

The device according to the present invention also comprises a linear actuator 110 connected to the joint Bi. The linear actuator 110 is intended to move the articulation Bi in the first direction Y.

The linear actuator 110 may be of the pulley type. It can also be, for example rack or worm type.

The first pantograph 100 and the second pantograph 200 are connected at one end 102.2 of the arm 102 and one end 202.2 of an arm 202 in the example shown by a ball joint 8 providing a great freedom of movement between the two pantographs 100, 200. The articulation between the first 100 and the second 200 pantographs is marked Ai.

The first pantograph 100 makes it possible to perform a homothety of center B1 and of ratio ki, the mathematical expression of which is as follows:

A ₁ M ₁ = U ₁ A ₁ B _1.

From where by differentiating:

ΔM ^ - ΔΔ ^ = Ic ₁ (ΔB ^ - Δ Ai)

That is to say that any displacement applied to the point Bi, when Ai is fixed, causes a displacement at the point Mi of the same direction and amplitude proportional to the displacement value of the point Bi, the proportionality coefficient being equal to ki: the ratio of homothety between Bi and Mi.

While any displacement applied to the point Ai, when Bi is fixed, causes a displacement at the point Mi of opposite direction and of amplitude proportional to the value of the displacement of the point Ai, the coefficient of proportionality then being 1-ki: the ratio of homothety between Ai and Mi.

That is to say that any displacement of a distance y in Bi in the direction Y, caused by the first actuator 110 moves the point Mi by a distance ki.y cf (equation I) in the direction Y.

The second pantograph 200 comprises a first pair of arms 202, 204 parallel to each other and a second pair of arms 206, 208 parallel to each other. The arm 202 is rotatably mounted by a first end 202.1 on a first end 206.1 of the arm 206, the arm 204 is rotatably mounted by a first end 204.1 on the arm 206 between the end 206.1 connected to the arm 202 and a other end 206.2 of the arm 206. The arm 208 is, in turn, rotatably mounted by a first end 208.1 on a second end 204.2 of the arm 204 and a second end 208.2 on the arm 202 between the first end 202.1 and a second end 202.2 connected to the end 102.2 of the arm 102 of the first pantograph 100. The articulation between the arm 202 and the arm 206 is marked D ₂ .

The articulation between the arm 202 and the arm 208 is marked E ₂ .

The articulation between the arm 204 and the arm 208 is marked B ₂ .

The articulation between the arm 204 and the arm 206 is marked C ₂ . A second linear actuator 210 is provided at the end 206.2 of the arm 202, the articulation between the arm 206 and the linear actuator is designated A ₂ .

The second actuator 210 ensures a displacement of the articulation A ₂ in a direction X orthogonal to the direction Y of the first actuator 110. The actuator 210 may be of the same type as the first actuator 110, it may be identical or not.

The homothety ratio k ₂ of the second pantograph 200 of center B ₂ is defined as follows:

A ₂ M ₂ = k ₂ .A ₂ B _2.

Thus any displacement of amplitude 1 in the direction X of the articulation A ₂ causes a displacement in Ai (= M ₂ ) of an amplitude - (k ₂ -l) in the direction X.

The displacement of the point Mi in the direction X is then of amplitude (M-Mk ₂ -I).

Advantageously, it is possible to obtain the same linear relationship between the linear displacements 110 and 210 in the directions Y and X respectively by correctly choosing the ratio between the values of

Indeed choosing: k ₂ = (2.Ic ₁ -I) Ak ₁ -1) We obtain a displacement of M equal to:

Ic ₁ X (II) The relation linking the distance y _M traversed by M in the direction Y and the displacement of the actuator 110 along Y is identical to that connecting the distance x _M traveled by M in the direction X and the displacement of the actuator 210 according to X Thus the controls of the two actuators 110, 210 can be identical. In addition each actuator can be fixed on a frame, without having to cause the movement of the other actuator.

The third pantograph 300 comprises a first pair of arms 302, 304 parallel to each other and a second pair of arms 306, 308 parallel to each other. The arm 302 is rotatably mounted by a first end 302.1 on a first end 306.1 of the arm 306, the arm 304 is rotatably mounted by a first end 304.1 on the arm 306 between the end 306.1 connected to the arm 302 and an arm 306. end 306.2 of the arm 306 connected to the end 206.2 of the arm 202 of the second pantograph 200. The arm 308 is rotatably mounted by a first end 308.1 on a second end 304.2 of the arm 304 and a second end 308.2 on the arm 302 between the first end 302.1 and a second end 302.2.

The articulation between the arm 302 and the arm 306 is marked D ₃ .

The articulation between the arm 302 and the arm 308 is marked E ₃ . The articulation between the arm 304 and the arm 308 is marked B ₃ .

The articulation between the arm 304 and the arm 306 is marked C ₃ .

In the example shown, the second 200 and the third 300 pantographs are arranged substantially parallel to each other. The arm 306 is rotatably mounted on the frame of the device substantially facing the movable articulation A ₂ and fixed relative to the articulation A ₂ .

According to the present invention, the hinge B ₃ is disposed vis-à-vis the joint B ₂ and integral in motion thereof. The device comprises a third linear actuator 310 of Z direction, orthogonal to the first Y and second X directions of the first 110 and second 210 actuators, connected to the end 302.2 of the arm 302, the connection being marked M ₃ . The third actuator 310 then provides a displacement along the Z axis, vertical in the example shown.

The homothety ratio k ₃ of the third pantograph 300 of center B2 is defined as follows:

A ₃ M ₃ = Ic ₃ A ₃ B ₃ .

According to the invention, the articulation M ₃ is moved, the articulation B ₃ being mobile and the articulation A ₃ being fixed.

Thus any displacement of amplitude z in the direction Z of

the articulation M ₃ causes a displacement in B ₃ of an amplitude - xz in the k ₃ direction Z.

The displacement of point Ai is then in the direction Z k of amplitude - xz. k ₃

The displacement of the point M is then in the direction Z k of amplitude - - (Jt ₁ - I) X z. k ₃

Grâce à la présente invention, on obtient donc une relation linéaire invariable, les rapports ki, k₂ et k₃ étant constants par construction, entre le déplacement des actionneurs et le déplacement de M quelque soit la position dans l'espace et dans toutes les directions. II y a alors une homogénéité du comportement du dispositif en tout point atteignable par Ml.By choosing k ₃ = (2.ki-1) / (k ₁ ), for displacement of the actuator 310 of amplitude 1 in the direction Z, a displacement of Ml equal to:

Thanks to the present invention, an invariable linear relationship is thus obtained, the ratios k ₁ , k ₂ and k ₃ being constant by construction, between the displacement of the actuators and the displacement of M whatever the position in space and in all directions. There is then a homogeneity of the behavior of the device at all points reachable by Ml.

Advantageously, it is thus possible to obtain identical linear relationships between the displacement of each linear actuator 110, 210, 310 and the point M in the X, Y and Z directions, which make it possible to define all the directions of the space.

This simplifies the control of the actuators. The same actuators can be used for the three directions, which simplifies the implementation, and reduces the cost of the device. The same control law can be used for the three directions, without the need for calibration for each axis. In the application to a haptic interface connected to the end of the arm, not only the displacements are of the same amplitude in the three directions, but the speed and acceleration characteristics are also homogeneous in all directions, which improves the haptic feedback for the user. In Figure 11, we can see an alternative embodiment of the device according to the present invention, for which the third pantograph 300 has not been shown for the sake of clarity. The connection between the first pantograph 100 and the second pantograph 200 is achieved by means of a universal joint 10. This is made possible by the fact that this connection is not intended to transmit a torque, but only to transmit a force.

This cardan makes it possible to ensure a large travel and is of simpler realization than a ball joint allowing an equivalent displacement.

In the example shown, the universal joint 10 comprises a fork 12 mounted rotatably at the end of the arm 102 of the first pantograph 100 and a second fork 14 rotatably mounted on the arm 202 of the second pantograph 200.

This embodiment allows the occurrence of a self-alignment phenomenon to ensure the function of a ball joint with, in addition, a movement of at least one half-solid angle, which increases the working space .

It is understood that a device whose pantographs are associated in a different way from that shown in Figures 5 to 9, is not beyond the scope of the present invention. Indeed, it could be expected that the first actuator 110 acts at Ai and the second pantograph 200 is associated with the first at Bi. In this case the relations between the different homothetic ratios would be modified if it is desired to have identical relations for each of the actuators (see table represented in FIG. 12, the references ©, © and © associated with the actuators, indicate the direction linear of each).

The device according to the present invention makes it possible to realize a robot manipulator or haptic interface whose relations between the actuators and the active end are linear and invariable regardless of the position of the end Mi. In a particularly advantageous manner, these relationships can in in addition to being made all identical, ie having the same coefficient of proportionality.

According to a particular example of the embodiment described in FIGS. 8-11, the triple pantograph used is of the Mi-AiM ₂ -B ₂ B ₃ -M _{3 type} . We choose a first pantograph with a value ki = 2. We then choose the second pantograph, with k ₂ = 3 and the third pantograph such that k ₂ = 3/2. This gives a pantograph with three degrees of freedom, the actuators are fixed and independent of each other, and the movements of the active end (Mi) are homogeneous in all three directions over the entire working space. In Figure 13, we can see an embodiment of a linear actuator that can be implemented in a device of the present invention.

The actuator 400 comprises a first 402 and a second pulley 404 of the same diameter disposed at a distance from one another, the axes of rotation of the pulleys being parallel.

A belt 406 is wrapped around the pulleys 402, 404 and is driven by them.

The actuator also comprises a carriage 408 integral in motion of the belt 406 and is able to move between the two pulleys 402, 404 in an axial direction W.

Advantageously, guide means 410 of the carriage 408 in the direction W are provided. They are formed, in the example shown, by a rail 410 extending between the two pulleys 402, 404 of axis parallel to the axis W, and on which a sole 409 of the carriage 408 slides, the sole 409 is provided of a form for receiving the rail 410. For this the carriage 408 comprises for example a passage 412 of dimensions adjusted to those of the rail 410.

Thus the displacement of the carriage is equal to the product of the radius of the pulleys by their angle of rotation, the direction of movement of the carriage depending on the direction of rotation of the pulleys.

Applied to the device of Figures 1 and 2, the carriage can be attached to the arm 206 of the second pantograph by the Al joint.

An actuator could be provided with pulleys of different diameter, it should in this case pulleys rotating at different speeds. The actuator 400 can also be used for the actuators 110 and 310.

In Figure 14, we can see an embodiment of a bidirectional positioner 512 particularly suitable for actuating an articulated pantograph device. The positioner 512 comprises two pulleys 516, 518 of parallel axes, the pulley centers 516, 518 being aligned in a first direction X1. These axes are orthogonal to the direction Xl. Each pulley 516, 518 is rotatably mounted on a frame 520. The positioner 512 also comprises a belt 20 wound around the pulleys 516, 518. It will be understood that the belt 520 forming transmission means may also be formed, for example by a chain.

These pulleys are able to be rotated by external means, for example by one or more motors or manually, to move the belt 520. They will be called driving pulleys thereafter.

The positioner 512 also comprises a carriage 522 comprising four return pulleys 524.1 to 524.4 in the example shown, mounted free to rotate on the carriage and around which the belt 520 travels, a rod 526 of longitudinal axis Z1 mounted to move in translation according to its axis Z1 on the carriage 522, a first end 526.1 is provided with a pulley 528 rotatably mounted on the rod 526, and a second longitudinal end 526.2 is connected to the point F.

The end F of the rod forms the active end of the positioner intended to be connected to a member to move. The carriage 522 has in the example shown substantially in the shape of a rectangular parallelepiped whose mediators are parallel to the axes Xl and Zl. The pulleys 524.1 to 524.4 are mounted at the four corners of the carriage 522.

The belt 520 has a first end 520.1 fixed to the rod 526 at its second longitudinal end 526.2 and a second end 520.2 also fixed to the second longitudinal end 526.2 of the rod 526.

The belt follows the following path: it is fixed by its end 520.1 to the second end 526.2 of the rod 526, runs along the axis Z1 to the deflection pulley 524.1, then travels along the axis X1 to the drive pulley 516, wraps around it to start in the opposite direction in the direction of the axis Xl to to the pulley 524.2. The belt 520 then bifurcates at a right angle and travels to the pulley 528 mounted on the rod 526, starts in the opposite direction and travels to the pulley 524.3, where it forks at right angles and travels along the Xl axis up to the drive pulley 518 on which it winds to start in the opposite direction along the axis Xl. It then wraps around the pulley 524.4, forks at right angles, travels along the axis Z1 to the second end 526.2 of the rod 526 to which it is attached.

The belt 520 then substantially forms a cross. According to the direction and angle of rotation of the driving pulleys 516, 518, the point H moves along the axis X1 only, along the axis Z1 only or in an intermediate direction. The drive pulleys 516, 518 are rotatably mounted on a chassis comprising a post 530 extending between the two pulleys. The amount advantageously forms a guide rail for the carriage 522, as is particularly visible in FIG. 14.

Advantageously also, the rod 526 is slidably mounted in a groove of the carriage, the groove being of axis Z1, thereby forming a guide rail for the rod 526.

The displacement of the point H along the axis X1 can be written as: Tx (H) = - (R516α516 + R518α518) / 2 (I) TZ (H) = - (R16α516 - R18α518) / 2 (II) R516, R518 being respectively the spokes of the driving pulleys 516, 518,

A516, α518 being respectively the rotation angles of the pulleys 516, 518. The masses of the actuators do not intervene in the inertia of the system because they are fixed.

In a particularly advantageous manner, it is expected that the pulleys 516, 518 have the same radius R ', thus the relations (I) and (II) can be written:

TxI (H) = - R '(α516 + α518) / 2 (I)

TZ1 (H) = - R '(α516 - α518) / 2 (II)

This makes it possible to simplify the control of the positioner and to homogenize the relations between angles and displacement in the two directions of movement.

Indeed, in this particular embodiment, a displacement of H along the axis X1 only is obtained by rotating the two drive pulleys 516, 518 in the same direction and at an angle of the same amplitude. A displacement along the Zl axis only is obtained by rotating the two drive pulleys 516, 518 in opposite directions and at an angle of the same amplitude.

In the example shown, the axes X1 and Z1 are orthogonal, but one could provide axes oriented in any way. The bidirectional positioner of FIG. 14 is particularly suitable for actuating the deformable parallelogram pantograph device. FIG. 15 shows a pantograph device actuated by a positioner according to FIG. 13 and a positioner according to FIG. 14.

Claims

1. Articulated device with three degrees of freedom in translation comprising an active end (6) intended to interact with an external environment, a first pantograph (100) and a second pantograph (200) associated in series, the first pantograph (100) being biased directly at one of its ends (Al, Bl) by a linear actuator (110), the second pantograph (200) being biased at two of its ends (A2, B2, M2) by two actuators, the first (110), second (210) and third actuators each having a direction of displacement (Y, X, Z) orthogonal to the other two directions of movement, the active end being carried by an end (M1) of the first pantograph, so that the relationship linking the displacement of the active end in each of the directions of the actuators and the displacement of each of the actuators is invariable. 2. Device according to claim 1, wherein the third actuator is a pantograph (300) itself biased at one end by an actuator (310), said third actuator. 3. articulated device according to claim 2, wherein the third point (M2) of the second pantograph is connected to the first point (Al, Bl) of the first pantograph which is not solicited directly by the first actuator (110), and in wherein the third point (M3, B3) of the third pantograph is connected to the first (A2, B2) of the second pantograph which is not biased directly by the second actuator (210). 4. The articulated device according to claim 2 or 3, in which the pantographs (100, 200, 300) have homothety ratios (k1, k2, k3) respectively, these homothetic ratios being linear functions or each other, so that the displacement of the active end (M1) is proportional to the displacement of each of the actuators with a coefficient of proportionality equal in modulus in the three directions (Y, X, Z). Articulated device according to claim 4, wherein the first pantograph (100) has a homothetic ratio equal to kl, the first actuator (110) being directly connected to the second point (B1) of the first pantograph, and the second actuator (210) being connected directly to the second point (B2) of the second pantograph, and wherein the second pantograph (200) k has a homothety ratio k2 equal to ^ι - - so that the functions (* i - l) linear connecting the movement of the active end (Ml) to that of each of the first and second actuators (110, 210) have the same coefficient of proportionality equal to kl in module. Articulated device according to claim 5, wherein the third pantograph (300) is connected by its third point (M3) to the first point (A2) of the second pantograph, the third actuator (310) being connected to the first point (A3). of the third pantograph, the second point (B3) being fixed, and wherein the third pantograph (300) has a homothetic ratio k3 equal to (kl + 1) so that the linear functions connecting the displacement of the active end (M1) of the first pantograph to that of each of the first, second and third actuators (110, 210, 310) have the same coefficient of proportionality equal to kl in modulus. The articulated device according to claim 5, wherein the third pantograph (300) is connected by its third point (M3) to the first point (A2) of the second pantograph, the third actuator (310) being connected to the second point (B3) of the third pantograph, the first point (A3) of the third pantograph being fixed, and wherein the third pantograph (300) has a homothetic ratio k3 equal to k1 so that the linear functions connecting the moving the active end (M1) of the first pantograph to that of each of the first, second and third actuators (110, 210, 310) have the same coefficient of proportionality equal to kl in modulus. 8. Articulated device according to claim 4, wherein the first pantograph (100) has a homothety ratio equal to kl, the first actuator (110) being connected directly to the second point (B1) of the first pantograph, and the second actuator (210) being directly connected to the first point (A2) of the second pantograph, and wherein the second pantograph (200) has a homothety ratio k2 equal to - ^ - 1 - - so that the functions (* i - l) linear connecting the displacement of the active end (Ml) of the first pantograph to that of each of the first and second actuators (110, 210) have the same proportionality coefficient equal to kl in module. Articulated device according to claim 8, wherein the third pantograph (300) is connected by its second point (B3) to the second point (B2) of the second pantograph, the third actuator (310) being connected to the third point (M3). of the third pantograph, the first point A3 of the third pantograph being fixed, and wherein the third pantograph (300) has a homothety ratio k3 equal to - ^ - 1 - - so that the functions K linear connecting the movement of the active end (Ml) of the first pantograph to that of each of the first, second and third actuators (110, 210,310) have the same coefficient of proportionality equal to kl in module. Articulated device according to claim 8, wherein the third pantograph (300) is connected by its second point (B3) to the second point (B2) of the second pantograph, the third actuator (310) being connected to the first point (A3). of the third pantograph, the third point (M3) of the third pantograph being fixed, and in which the third pantograph (300) has a homothety ratio k3 equal to - - so that the functions (* i - l) linear connecting the displacement of the active end (Ml) to that of each of the first, second and third actuators (110, 210,310) have the same coefficient of proportionality equal to kl in module. Articulated device according to claim 4, wherein the first pantograph (100) has a homothety ratio equal to kl, the first actuator (110) being directly connected to the first point (Al), and the second actuator (210). being connected directly to the first point (A2) of the second pantograph, and wherein the second pantograph (200) has a relationship of homothety k2 equal to ^ - - - - so that the linear functions K connecting the displacement of the active end (Ml) of the first pantograph to that of each of the first and second actuators (110, 210) have the same coefficient of proportionality equal to (^ ₁ - 1) in module. Articulated device according to claim 9, wherein the third pantograph (300) is connected by its second point (B3) to the second point (B2) of the second pantograph, the third actuator (310) being connected to the third point (M3). of the third pantograph, the first point (A3) being fixed, and wherein the third pantograph (300) has a homothety ratio k3 equal (2I ₁ - I) so that the linear functions connecting the displacement of (* i - 1) the active end (Ml) of the first pantograph to that of each of the first, second and third actuators (110 210 310) have the same coefficient of proportionality (k _ι -1) module. The articulated device according to claim 9, wherein the third pantograph (300) is connected by its second point (B3) to the second point B2 of the second pantograph, the third actuator (310) being connected to the first point (A3) of the third pantograph, the third point (M3) being fixed, and wherein the third pantograph (300) has a homothety ratio k3 equal to - - so that the linear functions connecting the displacement of (* l) the active end (Ml) of the first pantograph to that of each of the first, second and third actuators (110,210,310) have the same coefficient of proportionality equal to (k _ι -1) in module. Articulated device according to claim 12 or 13, wherein the second (200) and the third pantograph (300) are arranged next to each other, the first pantograph (100) extending away from the second (200) and third (300) pantographs. 15. Articulated device according to one of claims 1 to 14, wherein the connection connecting the first (100) and the second (200) pantograph is performed by means of a cardan. The articulated device according to any of claims 1 to 15, wherein at least one of the first (100), second (200) and third (300) linear actuators is of the pulley type, having a first ( 402) and a second (404) pulley of parallel axes around which is wound an endless flexible transmission member (406) and a carriage (408) integral in motion with said transmission element, said carriage (408) being connected to the at least one pantograph (100, 200, 300), rotating in one direction of rotation or in another of the pulleys (402 , 404), causing the carriage (408) to move linearly in the direction connecting the two pulleys (402, 404). The articulated device according to claim 16, wherein the pulley actuator comprises a guide rail (410) extending between the two pulleys (402, 404) and on which a flange (409) of the carriage (408) is sliding mounted. 18. Remote manipulator robot comprising at least one articulated device according to any one of the preceding claims. 19. A haptic interface comprising at least one articulated device according to any one of claims 1 to 17.