US3738110A

US3738110A - Device for driving a passive element according to a predetermined law of movement

Info

Publication number: US3738110A
Application number: US00198626A
Authority: US
Inventors: A Grosseau
Original assignee: Automobiles Citroen SA
Current assignee: Automobiles Citroen SA
Priority date: 1970-11-19
Filing date: 1971-11-15
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12
Also published as: IT938631B; GB1366511A; DE2155650A1; DE2155650C2; FR2114199A5

Abstract

The device comprises drive means adapted to move the passive element; programming means adapted to apply a theoretical law of movement to the passive element; detector means for the theoretical movement and detector means of the actual motion; comparator means adapted to deliver a signal depending on the separation existing between the theoretical and real movements detected by the said detector means; and means sensitive to said signal adapted to actuate the drive means so that the latter act in such a sense that the detected separation between the theoretical and real movements has a tendency to diminish. The detector means are grouped into a single apparatus having two mechanical members capable of moving, under the effect of linking means provided for this purpose, according to laws of movement reproducing the theoretical and real laws. The comparator means are directly sensitive to the separation between the respective positions of the two mechanical members and are composed of two parts respectively fixed rigidly on each of the mechanical members.

Description

lJnited States Patent 1 .[11] 3,738,11 Grosseau June 12, 1973 DEVICE FOR DRIVING A PASSIVE Primary ExaminerEdgar W. Geoghegan [75] Inventor: Albert Grosseau, Chaville, France [73] Assignee: S. A. Automobile Citroen, Paris,

France [22] Filed: Nov. 15, 1971 [21] Appl. No.: 198,626

[30] Foreign Application Priority Data Nov. 19, 1970 France 7041522 [52] US. Cl. 60/368, 60/446, 60/DlG. 2,

60/388, 60/390 [51] Int. CL. F15b 9/14, FlSb 9/17 [58] Field of Search 60/53 R, DIG. 2,

[56] References Cited UNITED STATES PATENTS 3,225,542 12/1965 Hansen et al. 60/53 R 3,542,274 11/1970 Miller 3,628,042 12/1971 Jacobus 3,628,330 12/197l Miller 60/52 VS ELEMENT ACCORDING TO A PREDETERMINED LAW OF MOVEMENT Att0rneyStevens, Davis, Miller & Mosher [57] ABSTRACT The device comprises drive means adapted to move the passive element; programming means adapted to apply a theoretical law of movement to the passive element; detector means for the theoretical movement and detector means of the actual motion; comparator means adapted to deliver a signal depending on the separation existing between the theoretical and real movements detected by the said detector means; and means sensitive to said signal adapted to actuate the drive means so that the latter act in such a sense that the detected separation between the theoretical and real movements has a tendency to diminish. The detector means are grouped into a single apparatus having two mechanical members capable of moving, under the effect of linking means provided for this purpose, according to laws of movement reproducing the theoretical and real laws. The comparator means are directly sensitive to the separation between the respective positions of the two mechanical members and are composed of two parts respectively fixed rigidly on each of the mechanical members.

10 Claims, 2 Drawing Figures PAIENIED m1 2m;

Q ACCORDING TO A PREDETERMINED LAW OF MOVEMENT The invention relates to a device for driving a passive element according to a predetermined law of movement, comprising:

drive means adapted to move the passive element;

programming means adapted to apply a theoretical law of movement to the passive element;

detector means for the theoretical movement and detector means for the real movement;

comparator means adapted to deliver a signal depending on the separation existing between the theoretical and real movements detected by the abovesaid detector means and means sensitive to the abovesaid signal adapted to control the drive means so that the latter act in a sense such that the separation detected between the theoretical and real movements tends to diminish.

The invention relates more particularly, because it is in this case that its application seems to have the most advantage, but not exclusively, to a device for driving a passive element of considerable mass, of the order of several tons, over a relatively large distance, of the order of several meters, in a fairly short time, of the order of several seconds.

It is a particular object of the invention to render the abovesaid device such that it responds better to the various exigences of practice better than hitherto and especially such that it communicates to the passive element accelerations less than a predetermined value, and that it ensures with precision, the arrest of the said passive element.

According to the invention, a device for driving a passive element, of the previously defined type, is characterized by the fact that, on one hand, the abovesaid detector means are grouped in a single apparatus having two mechanical members capable of moving, under the effect of connecting means provided for this purpose, according to laws of motion reproducing, to a given factor, respectively the theoretical'and real laws, and that, on the otherhand, the comparator means are directly sensitive to the separation between the respective positions of the two mechanical members and are composed of two parts fixed, rigidly, respectively on each of the said mechanical members.

In the case where the movement of the passive element is a translation movement, the two mechanical members of the apparatus constituting the comparator means are adapted to move in translation with respect to one another.

Advantageously, in the case which has just been considered, one of the mechanical members is constituted by. a'sleeve, whilst the other member is constituted by a rod adapted to slide in the sleeve, the comparator means being preferably constituted by a differential transformer of which the core is fast to one of the mechanical members, for example the rod, whilst the winding and the armature of the said transformer are rigidly fixed to the other member, for example the sleeve.

The invention consists, apart from the features de' scribed above, of certain other features which are preferably used at the same time and which will be more explicitly considered below with regard to a preferred embodiment of the invention. This will now be described in more detailed manner with reference to the accompanying drawings, but which are given purely by way of illustration and are in no way limiting.

In the drawings:

FIG. 1 is adiagram of the assembly of a device according to the invention; and

FIG. 2 shows in graphical manner the laws of theoretical and real movements.

Referring to FIG. 1, it is seen that the device for driving a passive element 1 according to a predetermined law of movement, comprises drive means 2, adapted to move the passive element; programming means 3, adapted to apply a law of theoretical movement; detector means 4 of the theoretical movement and detector means 5 of the real movement; comparator means 6 adapted to deliver a signal depending on the separation existing between the theoretical and real movements; and means 7 sensitive to the signal, adapted to control the drive means 2 so that the latter act on the movement of the passive element in a sense such that the separation detected between the theoretical and real movements tends to diminish.

The passive element has been shown diagrammatically in mixed lines and can be constituted by any load, for example a table for horizontal displacement. The passive element is connected by a link 8 to a projecting part 9, in the form of a rectangular parallelepiped, provided under a rack 10. Hydraulic jacks 11a, 1112 are provided to serve, for example the free end of their piston rod, as a stop to the portion projecting 9, at the end of the stroke of the load 1 and of the rack 10.

These jacks 11a, 11b could also serve as shock absorbers in the case where breakage of the rack 10 occurs betweenthe fixing zone of the load 1 to the rack and the zone where the latter is driven by the drive means '2.

These drive means 2 comprise the pinion 12 adapted to engage on the rack 10, and a hydraulic motor 13 driving the pinion 12 in rotation. The hydraulic motor 13 is supplied by a servo pump 14, in closed circuit. Safety valves 15 are provided between the two branches of the circuit extending between the servo pump and the motor, to avoid excess pressures in the said circuit. The servo pump 14 is driven by an electric motor 16.

The stroke volume of the servo pump 14 can be adjusted by the action of an actuating means 17 (diagrammatically shown) of this stroke volume. To a variation of the stroke volume of the pump 14, there corresponds a variation in the speed of the motor 13 and hence a variation in the speed of the load 1.

Programming means 3 comprise essentially a cam 18, of which the profile (not shown) is determined as a function of the theoretical law of movement. This cam 18 is mounted on an axle l9, perpendicular to the plane of the cam, rotated by a DC motor 20. The transmission of the rotary movement of the motor 20 to the axle is effected by means of a belt 21, driving a shaft 22 parallel to that of the motor 20. The movement is transmitted, by means of a brake-clutch assembly 23, from the shaft 22 to the input shaft 24 of a wheel and tangential screw reducer 25. The wheel of the reducer 25 is fixed 'on the axle 19, which is at right angles to the axle 22 of the engine 20 is ensured by a speed governing device (not shown) using a tachymetric generator 20a. The programming means 3 are arranged so that a half turn of the cam 18 corresponds to a forward" movement of the load 1, the following half turn of the cam 18 corresponding to the backward" movement of the said load.

Means are provided to arrest the rotation of the cam 18 between each to and fro movement. These means comprise a boss 27 provided on a sleeve coaxial with the axle 19, and contacts 28a, 28b, 29a, 29b grouped two by two, the two contact groups being diagrammatically opposite with respect to the center of the path of the boss 27.

These contacts are adapted to be actuated by the boss 27 when the cam 18 arrives in a position corresponding either to the end of a forward movement, or the end of a return movement. The arrest of the rotation of the cam 18 is effected by declutching the assembly 23 and progressive de-energization of the brake of the said assembly 23.

The detector means 4 of the theoretical movement and the detector means of the real movement are grouped into a single apparatus 30-having two

mechanical members

31, 32 capable of moving under the effect of linking

means

33 or 38, 39 according to laws of movement reproducing, to a given factor, the abovesaid theoretical and real laws respectively.

The mechanical member 31 is constituted by a cylindrical rod provided, at one end, with a roller 33 adapted to roll against the cam 18. The roller 33 constitutes the linking means between the member 31 and the abovesaid cam 18. The abovesaid roller reproduces directly the law of movement introduced by the cam 18. It can therefore be said that the factor by which the roller 33 intervenes in the theoretical law of movement is equal to unity. The member 31 is provided, in addition, on its outer wall, with a boss 34 of which the utility will appear later.

The mechanical member 32 is constituted by a sleeve surrounding a part of the rod 31. The latter is adapted to slide in the sleeve 32. Balls 35 are provided between the rod 31 and the sleeve 32 to reduce friction between these two members on their relative displacement. The sleeve 32 can slide in the direction of its axis, which direction is vertical and at right angles to the axis 19 of rotation of the cam 18. A spring 36 connects the sleeve 32 to the rod 31 and has the purpose of compensating partially the weight of the said rod 31 on movements of the latter effected in the direction of the axis of the sleeve 32. Two contacts 37a and 37b, provided in the sleeve 32 and separated along the axis of the latter, are arranged so as to be actuable by the boss 34 when the relative displacement of the

members

31 and 32 exceeds a predetermined value. When one of these contacts is actuated by the said boss 34, a declutching is produced in the assembly 23 and the cam 18 cannot be rotated.

The linking means, acting on the sleeve 32 to communicate to the latter a law of movement deducted, by a given factor, from the law of real movement, comprise a finger 38 borne by the sleeve 32 and projecting radially on the outer surface of the latter, and a screw 39, adapted to cooperate with the finger 38 coupled to the pinion 12. The displacements of the sleeve 32 are hence proportional to those of the load 1, and, as generally the amplitude of the movements of the load 1 can reach several meters, the ratio of the real displacement of the load 1 to the displacements of the sleeve 32 is greater than 1.

Comparator means 6 are directly sensitive to the separation between the positions of the

abovesaid members

31 and 32. These comparator means 6 are composed of two

parts

6a, 6b, fixed rigidly, respectively, on each of the said

members

31, 32. Preferably, comparator means 6 are constituted by a differential transformer, the parts 6a of the means 6 being constituted by the core of the differential transformer, whilst the part 6b is constituted by the winding and the armature of the said transformer. The core 6a is borne by a support 40 oriented parallel to the large dimension of the rod 31 and rigidly fixed to the latter. The support 40 passes through an opening 41 provided for its passage in one closed end of the sleeve 32.

The primary of the differential transformer is supplied by a source 42 delivering, under constant voltage, DC current, which is transformed into AC current by a modulator 43. The secondary circuit of the differential transformer is at mid-point and connected to a demodulator 44 giving at its output a continuous signal of which the amplitude depends and, preferably, is proportional to the separation between the position of the core and the resting position of the latter. The signal emerging from the differential transformer is amplified by a preamplifier 45 and an amplifier 46. The latter are supplied with DC current by a rectifier 47 itself supplied with AC current. A regulating potentiometer 48 is provided to enable, from a source of DC voltage 49, establishment of an adjustable reference level for the signals being applied to the input of the amplifier 46. A second potentiometer 50, of which the position is controlled by control 17 of the stroke volume of the pump 14, is also provided to deliver to the input of the amplifier 46 a reaction signal which is taken from the signal emerging from the preamplifier 45.

Means 7, sensitive to the amplified signal emerging from the amplifier 46, are essentially constituted by a servo valve 51 of which the winding 51a is subject to a signal issuing from the amplifier 46. The winding 51a controls the movements of a plunger 5 lb.

The servo valve 51 itself controls, from a source of liquid under pressure 52, the movements of the piston 53a of a double acting jack 53. There has only been shown the passages for supply of this jack 53. The piston 53a controls the movements of the control means 17 of the stroke volume of the servo pump 14.

Contacts 54a, 54b may be provided for decelerating the end of a forward movement or of a return movement of the rack 10 and, for example, in the case where the device is used in a cycle of operations, to permit the following operations.

In FIG. 2, the curve in solid line T represents the lower movement of the member 31 controlled by the cam 18. This is the law of theoretical movement, to a given factor, which has been considered up to the present. The space e is borne as ordinates, whilst the time t is shown as abscissae. The curve R traced in interrupted line represents the law of movement of the corresponding member 32, to the same given factor as for the theoretical movement, for the law of real movement of the passive element 1.

This being the case, the operation of the device according to the invention is as follows.

The assembly is ready to function when the various electrical and electronic devices are under voltage and the hydraulic devices are supplied with fluid. The cam 18 being stopped in a corresponding position, theoretically, to one end of a forward or return movement of the passive element 1, the regulating potentiometer 48 is actuated so that the delivery rate of the servo pump 14 is nil when the passive element 1 and the rack occupy a real position corresponding to the theoretical position applied by the cam.

It will be seen in fact that the core 6a of the differential transformer 6b can occupy, when the passive element 1 is at the end of a forward or return stroke and when the cam 18 is stopped in the position corresponding to this end of a stroke, a position for which the voltage at the output of the differential transformer is not completely nil. The potentiometer 48 enables correction of this separation due, for example, to manufacturing tolerances.

The rotary movement of the cam 18 is then actuated by putting the motor 20 into action and the assembly 23 and roller 33 are moved in a direction at right angles to the axis 19 of rotation of the cam 18, according to the law of movement T shown in FIG. 2.

The rod 31 follows the movement of the roller 33. The core 6a of the differential transformer is moved therefore from the position that it occupies at'rest and for which, after adjustment of the potentiometer 48, the delivery rate of the turbo pump 14 was nil. This displacement of the core 6a, with respect to the winding 6b, generates a signal at the output of the differential transformer 6 which, after preamplification and amplification, energizes the winding 51a of the electrovalve 51. The core 51b of the latter is moved in a direction such that the jack 53, supplied with fluid by the opening of the electrovalve 51, actuates an increase in the flow rate of the pump 14.

The hydraulic motor 13 is then supplied with fluid under pressure and, through a pinion 12 and the rack 10, drives the load 1.

The pinion l2 drives also the screw 39 which controls a displacement of the sleeve 32 in a direction such that the relative displacement of the core 6a with respect to winding 6b diminishes. For example, if the core 6a is displaced upwardly in FIG. 1, the sleeve 32 is displaced also upwardly.

By reason of the reaction introduced by the potentiometer 50 at the input of the amplifier 46, to a signal of given amplitude emerging from the preamplifier and provided from a given voltage at the output of the differential transformer 6, there corresponds a position of the piston 53a and a predetermined value of the flow rate of the pump 14; until this value of flow rate is achieved, the reaction introduced by the potentiometer allows a signal to persist of amplitude which is not nil at the input of the amplifier 46, which keeps the electrovalve 51 open. The latter closes at the moment when the desired value is reached and when the reaction of the potentiometer 50 annuls the signal emerging from the preamplifier 45. The flow rate of the pump 14 is governed by the signal emerging from the preamplifier 45.

When the roller 33 and the rod 31 move at a constant speed, which corresponds in FIG. 2 to the rectilinear portion of the curve T, the sleeve 32 is moved at the same speed, but the separation between the sleeve 32 and the rod 31 will have varied from the value d shown in FIG. 2, for there exists at the output of the differential'transformer 6, a signal of amplitude corresponding to the suitable flow rate of the pump 14.

In a transient period, that is to say when the roller 33 undergoes an acceleration or a deceleration, which corresponds in FIG. 2 to the incurved portions of the curve T, the signal at the output of the differential transformer 6 increases or decreases; there results also an increase or decrease in the stroke volume of the pump 14 and, consequently, an acceleration or deceleration of the load 1.

When the cam 18 and the roller 33 stop, the signal emerging from the differential transformer 6 diminishes progressively as a result of the reduction of the relative separation between the winding 6b and the core 6a. The flow rate of the servo pump 14 also dimin ishes regularly and is annuled when the winding 6b has retaken up, with respect to the core 6b, the position which it occupied initially.

As a result of which, there is obtained a device for driving the passive element 1 which responds well to the purpose which it was designed for by enabling, on one hand, stopping with precision of the passive element and, on the other hand, making it follow a law of movement with accelerations less than a given value, for example less than the acceleration due to gravity.

The employment of a hydraulic motor 13 is advantageous by reason of the low inertia of such a motor. The control of the flow rate of the fluid supplying the motor has a better action when it is effected by the servo pump 14. However, this control could be effected directly by a servo valve, especially of small power.

Various safety devices (not shown) can be provided such as a time delay device making possible increase in pressure of the source 52 only after the electronic apparatus has been placed under voltage or such as a device sensitive to the pressure of the liquid'in the stop jacks 11a and 11b, adapted to stop the cam 18 if the abovesaid pressure is too small.

To establish ideas, there is given below some numerical values relative to a particular embodiment of the device according to the invention.

Total mass of the passive element: 5,000 kilograms.

Stoke of the passive element: 3.8 meters Time taken by the passive element to effect its stroke:

2.5 seconds.

Stopping precision: more or less 1 millimeter.

During the stroke of the passive element, on the acceleration phase, the latter has an average value of the order of 3 m/s (3 meters per second, per second),

The maximum speed reached by the passive element is 2.435 m/s (2.435 meters per second).

In the course of the deceleration phase, the latter reaches a value on the order of 4.5 m/s (4.5 meters per second per second).

It is noted that the acceleration and deceleration are less than the acceleration due to gravity in absolute value.

Passive resistances (due especially to friction) are of the order of 5,00 Newtons or 500 daN.

The minimal distance for stopping at maximal speed is on the order of 0.5 m (0.5 meters).

As is self-evident and as emerges already from the foregoing, the invention is in no way limited to those of its methods of application, nor to those of its methods of production of its various parts, which have been more especially indicated; it encompasses, on the contrary, all variations.

I claim:

1. Device for driving a passive element according to a predetermined law of movement, comprising:

drive means adapted to move the passive element;

detector means for the theoretical movement and detector means of the actual motion;

comparator means adapted to deliver a signal depending on the separation existing between the theoretical and real movements detected by said detector means; and means sensitive to said signal adapted to actuate the drive means so that the latter act in such a sense that the detected separation between the theoretical and real movements has a tendency to diminish,

said detector means being grouped into a single apparatus having two mechanical members capable of moving, under the effect of linking means provided for this purpose, according to laws of movement reproducing, to a given factor, respectively said theoretical and real laws,

and the comparator means being directly sensitive to the separation between the respective positions of the two mechanical members and being composed of two parts respectively fixed rigidly on each of said mechanical members.

2. Device according to claim 1, for driving a passive element in translation, wherein the two mechanical members are adapted to move in translation with respect to one another.

3. Device according to claim 2, wherein one of the mechanical members is constituted by a sleeve while the other member is constituted by a rod adapted to slide in the sleeve.

4. Device according to claim 2, wherein the comparator means are constituted by a differential transformer having a core fast to one of the mechanical members and a winding fast to the other mechanical member.

5. Device according to claim 2, wherein the programming means are constituted by a cam bearing directly on one of the mechanical members whilst the other mechanical member is moved by gear reduction means driven by drive means adapted to move the passive element.

6. Device according to claim 3, wherein the programming means are constituted by a cam bearing directly on one of the mechanical members whilst the other mechanical member is moved by gear reduction means driven by drive means adapted to move the passive element, and the gear reduction means comprise a screw, rotated by said drive means, adapted to drive in translation, in a direction parallel to its axis, by a finger provided on the sleeve.

7. Device according to claim 1, wherein the drive means adapted to move said element comprise a hydraulic motor supplied by a servo pump of which the delivery rate is governed by the value of the signal delivered by the comparator means.

8. Device according to claim 1, comprising safety means adapted to come into effect when the relative separation between the mechanical members reaches a predetermined value.

9. Device according to claim 2, wherein the drive means comprise a rack and pinion driving the rack, the latter being mechanically connected to the passive element.

10. Device according to claim 2, comprising hydraulic jacks adapted to serve as a stop, at the end of the stroke, for the passive element.

Claims

1. Device for driving a passive element according to a predetermined law of movement, comprising: drive means adapted to move the passive element; programming means adapted to apply a theoretical law of movement to the passive element; detector means for the theoretical movement and detector means of the actual motion; comparator means adapted to deliver a signal depending on the separation existing between the theoretical and real movements detected by said detector means; and means sensitive to said signal adapted to actuate the drive means so that the latter act in such a sense that the detected separation between the theoretical and real movements has a tendency to diminish, said detector means being grouped into a single apparatus having two mechanical members capable of moving, under the effect of linking means provided for this purpose, according to laws of movement reproducing, to a given factor, respectively said theoretical and real laws, and the comparator means being directly sensitive to the separation between the respective positions of the two mechanical members and being composed of two parts respectively fixed rigidly on each of said mechanical members.