FR2764008A1 - Electro-hydrostatic servo-actuator on movable suspended platform, for aircraft/heavy vehicle simulators and dynamic test bed use - Google Patents

Abstract

The device on the platform (3) includes: - an hydraulically powered actuator (6); - an hydrostatic feed circuit (20,21); - a rotating device (13) for bi-directional control (14) of the fluid feed from the hydraulic actuator (6). The triple effect actuator (6) has three separated chambers (10,11,12) each having a section (S0,S1,S2). The first `equalising' section (S0) is submitted to a equalising pressure (P0) formed in a equalising chamber (10), created by the hydro-pneumatic equaliser means (27,28,29,s). The active sections (S1 and S2) with sensibly equal surfaces receive differential pressures (P1,P2) created by the rotating means (13,14) of the bi- directional control. The hydrostatic feed circuit (20,21) includes a fluid feed device (15) which feeds fluid from the equalising chamber (10).

Description

Mobile platform electrohydrostatic servo actuator
suspended
The present invention relates to an electrohydrostatic servo actuator of a suspended mobile platform, intended more particularly, but not exclusively, to a movement system for training in piloting aircraft and driving vehicles such as trucks, tanks, as well for mobile dynamic testing platform.

 It is known, on the one hand, that the booths of current simulators are mounted on a platform animated by servo actuators generally arranged according to a so-called hexapod kinematics, described by French patent No. 1511683 of January 1967 of the Franklin Institute, which allows movements to be restored according to the six degrees of freedom, trying to reproduce the dynamic atmosphere felt by the pilot / driver.

Flight / driving simulators must realistically reproduce the dynamic atmosphere on the ground. The pilots / drivers should only feel the accelerations which are caused by the modification of the balance of the plane / vehicle, either voluntarily (stimuli on a command), or involuntarily (turbulence, vibration, shock, etc).

Nevertheless, it appears that the training of a student pilot / driver does not require to reproduce the values of displacement / acceleration actually observed.

Experience also shows that certain parts of the human body are rather sensitive to variations in acceleration.

To restore the dynamic environment, it is also necessary to ensure proprioceptive coherence (bodily sensations). If this is not observed, the quality of the training is degraded, which can lead to simulation illness.

 It is known, on the other hand, that cabin movement systems with, for example, six hydraulic or electric servo actuators known to those skilled in the art are expensive, due to the multiplicity of these, if one wishes to respect the quality criteria of accelerometric restitution, so that the training is beneficial.

Problem
The problem posed is to have cost-effective optimized servo actuators so that the mobile platform system for, for example, flight simulator driving / driving cabin movement is inexpensive to acquire and use.

State of the art
It is known that linear hydraulic servo actuators with a double-acting power cylinder of the single rod type, therefore with asymmetrical active sections, incorporate servovalves and require a hydraulic power unit meeting specific design criteria and, by definition, oversized, low efficiency. , and consequently very expensive.

A double-acting power cylinder of the double rod type does not require an asymmetrical servovalve, but has a large center distance between ball joints which penalizes the kinematic deflections of the mobile platform.

It is known that electromechanical servo actuators have better efficiency, but require a kinematics of transformation of the rotational movement of the electric motor / servo motor for movement into movement, that is to say tilting by lever arm requiring very many pivots and / or mechanical articulations. , see in this the French patent Alet n "2639746 of November 1988, either by screw-nut system whose smoothness of operation and reliability is not comparable to a hydraulic cylinder of power with hydrostatic bearing (s) .

A hybrid technology is described by French patent ne2739428, which shows, in a hydraulic differential cylinder for static load balancing with reduced dry friction, the complex association of an electric motor / servomotor driving a hydrostatic screw-nut system, requiring a high pressure rotary seal and an axial force recovery stop due to the hydrostatic bottom effect acting on the end of the screw and in addition, creating a parasitic torque in addition to the useful axial force. In addition, the supply of fluid under high pressure to the so-called hydrostatic screw-nut makes this type of actuator extremely expensive.

Indeed, the actuation amplitude necessary to recreate the acceleration and deceleration phases of return to neutral called in English washout, and the changes in attitude of the training cabin, is a first criterion of race sizing useful for the servo actuators of the mobile platform system of the cabin movement, particularly penalizing for the electromechanical screw-nut system of considerable length because limited by the critical speed and the buckling.

Another kinematic criterion of the mobile platform is the useful stroke related to the minimum center distance of the linear actuator.

Static charge is a penalizing operating parameter in terms of servo performance.

The state of the art for so-called static load balancing is described in various patents: -SANDERS-US patent nO 4021019, of May 1977, -BOVY / Warnan-patent français nO 2654716 of november 1989, -BOVY-french patent No. 2669381 of November 1990, -LACROIX-French patent No. 2739428 of November 1995.

The technique uses a hydropneumatic accumulator whose preset inflation pressure is exerted on differential sections of a hydraulic cylinder piston with a single asymmetric rod to counterbalance the average so-called static load supported by the rod.

Purpose of the invention
The object of the invention is to propose a new electrohydrostatic servo actuator for a suspended mobile platform which avoids the aforementioned drawbacks and makes it possible: - to balance an average load (F) known as the static load created by the suspended masses formed by a mobile platform supporting a payload such as for example a flight simulator / driving vehicle cabin subjected to gravity.

The electrohydrostatic servo actuator for a mobile platform according to the invention is a bidirectional hydrostatic control comprising: -a hydraulic power actuator, -a hydropneumatic load balancing means (F) called static.

-a hydrostatic supply circuit with a distribution means, -a bidirectional hydrostatic control means for supplying fluid to said hydraulic power actuator, characterized in that the hydraulic power actuator is triple-acting with three separate chambers each having a section (So, Si, S2), the first section (So) of the balancing chamber being subjected to a pressure (Po) created by said hydropneumatic load balancing means (F) said to be static, the sections active (S1 and S2) of substantially equal surfaces receiving the differential pressures created by said rotary bidirectional hydrostatic control means, and in that, in addition, the hydrostatic supply circuit comprises a distribution means supplied with fluid from the balancing chamber.

According to an advantageous embodiment, the hydraulic power actuator has three separate hydraulic chambers arranged in tandem in a hollow body and whose active sections (S1,
S2) are of equal area.

According to another very advantageous embodiment, the hydraulic power actuator is of the type with three separate hydraulic chambers, two of which are coaxial with one another around a hollow rod of the actuator.

According to another advantageous embodiment, an internal section chamber (So, S1) is delimited by a hollow rod and a plunger.

Preferably, said bidirectional hydrostatic control rotary means is of the positive displacement hydraulic pump type, driven by an electric servomotor.

According to an advantageous embodiment, said rotary bidirectional hydrostatic control means is of the hydraulic servo pump type with variable positive displacement, driven by an electric motor at constant speed.

Preferably, a so-called booster pressure distribution means (Pg) supplies a hydrostatic circuit connecting the two chambers (S1, S2) of the hydraulic power actuator to the rotary bidirectional hydrostatic control means.

Advantageously, the so-called booster pressure (Pg) of the hydrostatic circuit of the power cylinder is a fraction of the pressure (Po) which is exerted on the section (So) of static load balancing and can supply the two chambers (S1 ) and (S2) through a fluid distribution means.

Preferably, said distribution means comprises non-return valves allowing the booster of the hydrostatic circuit.

Advantageously, said distribution means comprises electrically controlled valves.

Preferably, the hydraulic power actuator with balancing section (So), the bidirectional hydrostatic control means supplying the hydraulic actuator of the triple effect type with two substantially equal active sections (S1,
S2), the fluid distribution means of the hydrostatic circuit, can form a single assembly adjacent to the actuator.

Thus advantageously, according to the invention, the mobile platform system suspended at n degree (s) of freedom, particularly for training simulator, comprises n servo actuator (s) not requiring a hydraulic power plant common to the servo actuators.

Preferably, said hydropneumatic means for balancing the so-called static load (F) creating the balancing pressure which can be controlled, is common to all the n servo actuators of the mobile platform suspended at n degree (s) of freedom.

Description
The present invention will be better understood in the light of the detailed description of an embodiment, taken as a nonlimiting example, and illustrated by the appended drawings, in which: the same reference number always identifies a homologous element whatever the embodiment.

The embodiments or variants of the invention although described in particular forms may be subject to modifications within the reach of the skilled person without departing from the scope and spirit of the invention .

- Figure 1 shows a linear servo actuator power cylinder type double acting double rod active equal piston sections.

- Figure 2 shows an embodiment of the invention.

- Figure 3 shows an embodiment of part of the invention relating to a distribution means.

- Figure 4 shows a variant of the distribution means.

- Figure 5 is a typical response graph of such a servo actuator.

- Figure 6 shows another embodiment of the triple effect actuator part.

The operation of the mobile platform servo actuator 3 of the invention is explained below.

Beforehand, according to FIG. 1, it is known to those skilled in the art that different kinematics make it possible to connect with degrees of freedom adapted to the required application, the articulated ends 4, 5 of the servoactuator 1, object of the invention, on the one hand, for example, at its base fixed to the ground 2 and on the other hand to the mobile platform 3, thus allowing angular and linear deflections of the mobile platform, an example of which is described by French patent n01511683.

We will not describe the control loop, which can be of the position / acceleration type allowing the servo actuator, object of the invention, to produce an output Y, from an input setpoint X, for example according to FIG. 4, as being part of the known state of the art.

Fig. 5 shows an acceleration response graph of a simulator cabin motion actuator. Setpoint
X developed by the steering / vehicle control computer, for example, of acceleration applied to the input of the servo controlling the servo actuator, generates an acceleration response of the servo actuator, taking into account its closed loop transfer function, at its rod end 7 leading to travel a certain stroke Y. The travel traveled depends on the deceleration threshold allowed said washout, for example, in this case equal to 1 m / s2 (0.1 g), so that the servo actuator can return to neutral position, without the driver / driver being able to feel this deceleration: this well-known device avoids arriving at the end of travel stop and allows the servo actuator to put itself in neutral position to produce a new interactive replica controlled by the computer. flight / piloting of the simulator.

The double-acting type linear hydraulic servo actuator (also called servo), shown in fig. 1 with a double rod of section So, comprises a body 6 with two hydraulic chambers 11 and 12, in which a movable member consists of a cylinder rod 7 and a piston 8 receiving on its active sections S1 and S2 the respective pressures P1 and P2 created by a servovalve 9, well known to those skilled in the art, controlled by an input signal i which is an image of the servo error. A hydrostatic force resulting from the forces acting differently on the sections S1 and S2 of the piston 8 of the rod 7, makes it possible to move the jack rod in the jack body against the supported load, resulting from the
average load F, called static, and
-dynamic load due to accelerated inertia.

Hydrostatic bearings 6a are generally provided to reduce friction between the rod 7 and the linear actuator body 6. Only a dynamic seal is provided at the rod outlet.

Complementary protection means 16 are generally provided against on the one hand, the fluid overpressure in the hydraulic chambers 11 and 12 and on the other hand, against impacts at the end of the actuator stroke such as, for example, hydraulic shock absorbers intrinsically safe.

The input setpoint X applied to a servo can be a position, speed, acceleration / force setpoint or a combination of these calculated by the flight control / driving computer of the simulator to recreate the dynamic atmosphere desired for the application considered. A servovalve control signal intensity i corresponds to a flow of fluid sent to one of the chambers 11 or 12 and extracted from the other chamber 12 or 11 of the power cylinder 6, thus controlling the speed of movement of the cylinder rod 7.

The invention is a new bidirectional hydrostatic control, optimized for its application.

According to fig. 2,4,6, the electrohydrostatic servo actuator 1 for mobile platform 3, in accordance with the invention comprises: a hydraulic power actuator 6 said to have triple effect comprising three separate chambers 10, 11, 12 each having a section , S1, S2, respectively:
-a section So receives a pressure PO called balancing
creating an average static load balancing effort F
which is exerted on the end of the rod 7 of the jack 6,
-two active sections S1 and S2 delimited by the piston 8
and the rod 7 being subjected to differential pressures P1
and P2, as already explained above, to modify
the dynamic balance of the rod 7 transmitting the force to
the platform by the articulation 5, -a hydrostatic circuit (20, 21) of supply with a distribution means 15 supplied with fluid from the chamber 10, -a rotary means 13 of bidirectional hydrostatic control 14 which generates a flow of fluid sent to one of the chambers 11 or 12 and extracts a flow rate from the other chamber 12 or 11, and creates the differential pressures P1 and P2 acting on the active sections 11 and 12 to move the piston rod 7 8 in the power hydraulic cylinder body 6.

a hydropneumatic balancing means 27 of static charge F creates the pressure PO prevailing in the chamber 10 having the cross section
So. This pressure PO can be controlled by regulation means 28 and / or filtered supply 29.

Preferably, the active sections S1, S2 are of substantially equal surfaces.

A characteristic of the invention is that the fact of balancing the average static load F supported by the servo actuator makes it possible to minimize the power necessary for actuating the supported load and subsequently, the dimensioning of the rotary means 13 for hydrostatic control 14 supplying in hydraulic fluid the active chambers 11 and 12 of the hydraulic power actuator 6: the power absorbed by the motor / servomotor member of the hydrostatic control is thus reduced to the minimum.

According to fiv. 1, the hydraulic power actuator 6 has three separate hydraulic chambers 10, 11, 12 each having a respective surface section So, S1, S2 arranged in tandem in a hollow body called a cylinder 6.

According to fig. 2,4,6, the hydraulic power actuator 6 has three hydraulic chambers 10,11,12 two of which 11 and 12 are coaxial with each other around a hollow rod 7b.

Advantageously, the internal section chamber (So, S1) is delimited by a hollow rod 7b and a plunger (6b).

Fig.6 shows another embodiment where the static load balancing chamber 10 F is internal to the hollow rod 7b of the hydraulic power actuator 6.

The actuator 6 can be a movable body and a fixed rod 7a or b, without going beyond the scope and the spirit of the invention.

Preferably, said rotary hydrostatic control means 13 is of the positive displacement hydraulic pump type, driven by an electric servomotor M, of the direct current type with or, preferably, brushless of the synchronous / asynchronous type self-piloted in flow and current. i,.

According to another embodiment, said rotary hydrostatic control means 13 is of the type with hydraulic servo pump with variable positive displacement, driven by an electric motor.
M, for example, at constant speed.

It is understood that a characteristic characteristic specific to the hydrostatic control revealed is that the hydraulic pump can operate as a hydraulic motor in certain transient phases of load deceleration, phases which then become motive thus restoring energy to the electric motor / servomotor M d 'training.

Figs. 2, 3 show a hydrostatic circuit 20,21 connecting the two chambers 11 and 12 of the hydraulic power actuator 6 to the rotary means 13 of bidirectional hydrostatic control.

The hydrostatic supply circuit (20, 21) comprises a distribution means 15 supplied with fluid from the chamber 10. The distribution means 15 comprises a regulation means 17, 22 which makes it possible to supply under a so-called low pressure booster pressure Pg the hydrostatic circuit 20, 21. A characteristic of the invention is to use the balancing pressure PO of static charge F prevailing in the chamber 10 as generating pressure allowing the filling and the booster of the hydrostatic circuit, and also ensuring cooling of the hydraulic fluid during operation of the servo actuator 1.

According to another characteristic of the invention, the servomotor / motor M can be cooled by a circulation of hydraulic fluid delivered by the distribution means 15.

Advantageously, the adapted booster pressure Pg of the hydrostatic circuit of the hydraulic power actuator 6 is a fraction of the pressure PO which is exerted on the section So of static load balancing and can supply the two chambers S1 and S2 at through distribution means 18, 19 and regulation 17 and 22 for controlling the flow of hydraulic fluid.

A protection means 16 of the hydrostatic circuit 20, 21 can also be provided in addition to the distribution means 15.

According to fig.3, said distribution means 15 includes non-return valves 18, 19
Advantageously, according to FIG. 4, said distribution means comprises valves 23, 24 electrically controlled by an electronic controller 25 for controlling an electric servomotor or servo pump.

Another characteristic of the invention is that the electrical control of the amplifiers 23a, 23b of the valves 23, 24 controlled by the electronic controller 25 according to the direction of rotation of the drive servomotor of the hydrostatic means 13 of bidirectional hydrostatic control 14, allows control around the supply flow rate around the chambers 11, 12 in order to further improve the stability, the linearity and can also allow the bypass of the hydraulic power actuator, for example for cooling and / or in case of breakdown.

Advantageously, the rotary means 13 for bidirectional hydrostatic control by servomotor M, the distribution means 15, 16 of the hydrostatic circuit 20, 21, form a single assembly 100 which can be adjacent, or integrated into the power actuator 6 with triple effect .

Thus, the mobile platform system 3 comprising one or more actuators 1 according to the invention does not require a hydraulic power unit common to the n electro-hydraulic servo actuators of the prior art.

In addition, the value of the static load supported F calculated, for example, from the pressures PO, P1, P2 measured prevailing in one or more chambers 10, 11, 12 of n actuators, the balancing pressure of said static load F can be calculated to control a regulating means 28 electrically controlled by an elaborate signal s. This signal s can be the image of the average load F to be supported in a position measured by the rod position sensor Y of the servo actuator (s) 1.

Preferably, said hydropneumatic means 27 for balancing the load F is common to all the n servo actuators of the suspended mobile platform 3, with n degrees of freedom.

Claims (1)

 Claims Rev n01: electrohydrostatic servo actuator, for mobile platform (3) comprising: -a hydraulic power actuator (6), a hydropneumatic means (27) of load balancing (F) called static, -a hydrostatic circuit (20, 21 ) supply, a rotary means 13 for bidirectional hydrostatic control (14) for supplying fluid to said hydraulic power actuator (6), characterized in that the hydraulic power actuator (6) is triple-acting comprising three separate chambers (10, 11, 12) each having a section (So, S1, S2), the first so-called balancing section (So) being subjected to a balancing pressure (PO) prevailing in a balancing chamber ( 10), created by said hydropneumatic balancing means (27, 28, 29, s), the active sections (S1 and S2) of substantially equal surfaces receiving the differential pressures (P1, P2) created by said rotary means (13, 14) bidirectional hydrostatic control and that the hydrostatic supply circuit (20, 21) comprises a distribution means (15) supplied with fluid from the balancing chamber (10). Rev. n02: electrohydrostatic servo actuator for a mobile platform according to the preceding claims, characterized in that the hydraulic power actuator (6) has three separate hydraulic chambers (10, 11, 12) arranged in tandem in a hollow body (6) of the actuator and whose active sections (S1, S2) are of equal area. Rev. n03: electrohydrostatic servo actuator for mobile platform according to claim n0l, characterized in that the hydraulic power actuator (6) has three separate hydraulic chambers (10, 11, 12), two of which are arranged coaxially with respect to the 'other around a hollow rod (7b) of the actuator (6). Rev. n04: electrohydrostatic servo actuator for mobile platform according to claims n "l and 3, characterized in that an internal chamber (10, 11) of section (So, S1) is delimited by a hollow rod (7b) and a plunger ( 6b). Rev. n05: electrohydrostatic servo actuator for mobile platform according to any one of claims n01 to 4, characterized in that said rotary means (13) of bidirectional hydrostatic control (14) is of the positive displacement hydraulic pump type driven by an electric servomotor (M). Rev. n06: electrohydrostatic servo actuator for mobile platform according to any one of claims n01 to 4, characterized in that, said rotary means (13) of bidirectional hydrostatic control (14) is of the type with hydraulic servo pump with variable positive displacement driven by a electric motor (M). Rev. n07: electrohydrostatic servo actuator for mobile platform according to any one of the preceding claims, characterized in that, the hydrostatic supply circuit (20, 21) connecting the two chambers (11, 12) of hydraulic actuator (6) of power by rotary means (13) of bidirectional hydrostatic control, comprises means for distributing fluid (15, 16) under pressure (Pg) which is a fraction of the pressure (PO) which is exerted on the section (So) d 'balancing. Rev. n08: electrohydrostatic servo actuator for mobile platform according to claim n "7, characterized in that, said means for distributing (15, 16) pressurized fluid called booster (Pg) comprises valves (18, 19; 23, 24) electrically controlled (25, 23a, 23b). Rev. n09: electrohydrostatic servo actuator, for mobile platform according to any one of the preceding claims, characterized in that, the hydraulic power actuator 6, the rotary means (13) of bidirectional hydrostatic control (14) supplying the hydraulic actuator ( 6) of the triple effect type, the fluid distribution means (15, 16; 17, 18, 19, 22; 17, 23, 24, 22) of the hydrostatic circuit 20, 21, can form a single assembly (100) adjacent to the actuator (6) Rev. nQ 10: mobile suspended platform system (3), particularly for simulator for driving an aircraft or driving a vehicle, characterized in that it comprises at least one electrohydrostatic servo actuator according to any one of claims n "l to 9, and in that the hydropneumatic means (27) of load balancing (F) called static, is common to all the servo actuators, and in that, in addition, the necessary balancing pressure (PO ) can be controlled by a regulation means (28, 29, s) to balance the average load (F) called static supported by the mobile platform (3).