Abstract:
A device for deploying and aiming structural elements designed to be placed in Earth includes at least one locking/unlocking device making it possible to deactivate the first coupling mode and to activate a second coupling mode allowing a portion of the device to be aimed at a target. The device uses: a plurality of structural elements linked together by articulations, the assembly forming an articulated arm linked to a payload via a root section; the articulations having at least one pivoting connection making it possible to have two consecutive structural elements pivot relative to one another; a motor making it possible to activate at least one pivoting connection of an articulation; and a system for coupling the articulations making it possible to link the pivoting of all of the structural elements comprising a first coupling mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to foreign French patent application No. FR 0906177, filed on Dec. 18, 2009, the disclosure of which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to the field of articulated devices designed to be placed on a payload placed in Earth orbit. More particularly, the invention relates to the field of satellites comprising structures to be deployed such as solar generators. Finally the invention relates to devices having two life phases in which the first phase comprises the deployment of structural elements in space and in which the second life phase comprises the aiming of these elements at a target during the flight in orbit. 
     BACKGROUND 
     Currently, when satellites are placed in orbit around the Earth, they require a phase for the deployment of the structural elements carrying solar generators or antennas depending on the mission. This phase is particularly critical because the success of the mission depends on it. 
     The structural elements assembly is a structure which forms an articulated arm. Notably, amongst these structural elements there are yokes and/or solar panels and/or antennas. These elements are joined together by articulations from the root section to the end of the articulated arm. 
     In order to obtain a fully deployed posture of the structural elements and to minimize on the one hand the distribution of the motive force on the structural elements and on the other hand the kinematic interferences between the elements, it is often necessary to use a coupling system making it possible to coordinate and articulate the deployment of the structural elements in a uniform manner. 
     The initially-folded structure is deployed according to a movement sequence and at a determined speed. All the angles between two consecutive structural elements are opened according to a determined law by the coupling mechanism. 
     A known coupling system uses pulleys positioned on each of the articulations and cables connecting the pulleys making it possible to transfer the forces between the structural elements at the time of deployment. 
     In order to activate the first articulation which comprises a first pulley, a motor is usually situated at the root section, that is to say at the first articulation which joins together the payload of the satellite and the first structural element. 
     At the time of deployment, certain structures have, in addition to the coupling system, a system for locking the articulations together. The locking system makes it possible to immobilize the articulations and hence the couplings linked to the articulations for the rest of the mission of the satellite which will no longer need to deploy or retract these structural elements. The locking makes it possible to pass from a first life phase of the satellite corresponding to placement in orbit and deployment of its structural elements to a second life phase corresponding to the mission itself, in which the structural elements will have a specific mobility. 
     Once the structure is deployed, it may be necessary, throughout the lifetime of the satellite, to aim the structural elements at a target. In this second life phase, the deployment of the structure being completed, it is necessary, depending on the mission, to aim the structure in a direction of a target. For example, this may be the sun, if the structure comprises solar generators such as solar panels, or else a geographic region on the planet in the case of an antenna or else a precise point in space as required. 
     In order to protect the deployment phase, it is usually separated from the phase corresponding to the mission. Currently, the drive means used in each life phase are partitioned for security reasons. Notably, the motor which is used to articulate the structural elements for aiming at a target is different from the motor which is used to deploy the structure. The drive means are different depending on the life phase because the mechanisms of articulations with and without coupling of the two phases are different. 
     Usually, the pivoting connection of the root section is fixed after the deployment; it is said to be locked. In the prior art, there is at the root section of the payload, a pivoting connection making it possible to orient the whole of the deployed structure, the structure comprising all the attached structural elements when they are locked together. 
     One drawback of the solutions of the prior art is the space requirement and the weight of a second motor for aiming the deployed structure at a target. 
     A second drawback is that the locking system immobilizes the coupling of the articulations and locks the structure, the pulley mechanism making it possible to deploy the structural elements then no longer being used. The second motor then activates the articulations of the structure in order to cause all or some of it to pivot. This solution means that it is necessary to couple the locked coupling system with another system making it possible to rotate a portion of the structure so as to make it pivot towards a target. 
     One object of the invention is to alleviate the aforementioned drawbacks. 
     SUMMARY OF THE INVENTION 
     One object of the invention is to share the drive means in the two life phases. In particular, the invention proposes to define two modes of motor function of the coupling for each of the life phases. The invention comprises a locking/unlocking system making it possible to pass from a first coupling mode comprising a first law of articulation of the structure for the deployment to a second coupling mode comprising a second law of articulation of the structure for the aiming of the structure. 
     Advantageously, the device for deploying and aiming structural elements designed to be placed in Earth orbit comprises:
         a plurality of structural elements linked together by articulations, the assembly forming an articulated arm linked to a payload via a root section;
           the articulations comprising at least one pivoting connection making it possible to have two consecutive structural elements pivot relative to one another,   the root section comprising a pivoting connection making it possible to have the first structural element pivot relative to the payload;   
           a locking/unlocking system comprising at least one locking device placed on an articulation making it possible to lock at least one pivoting connection;   a coupling system comprising a first coupling mode allowing each of the structural elements to pivot according to a predefined law of rotation.   at least one motor making it possible to activate the coupling system, the said motor being positioned on an articulation, called a driving articulation.       

     Advantageously, the locking system makes it possible to deactivate the first coupling mode and to activate a second coupling mode, the second coupling mode making it possible to retain the unlocking of a pivoting connection of at least one articulation, called the aiming articulation, the rotation of the motor causing the rotation of the aiming articulation. 
     Advantageously, the coupling system comprises:
         a plurality of pulleys linked by cables, one pulley of which is activated by the motor, called the driving pulley and;   means for attaching the pulleys to the structural elements, each of the articulations comprising at least two pulleys one of which is attached to an upstream structural element, called the upstream pulley, and the other is attached to a downstream structural element, called the downstream pulley, the root section comprising a pulley attached to the first structural element.       

     Advantageously, the locking/unlocking system comprises at least one device for locking/unlocking a coupling pulley relative to the articulation. 
     Advantageously, the articulation comprising the motor, and all the articulations situated between the articulation comprising the motor and the aiming articulation comprise a device for locking/unlocking a pulley, the aiming articulation comprising a device for locking/unlocking a pulley only on the downstream pulley. 
     Advantageously, all the articulations have a device for locking/unlocking a pivoting connection of an articulation except the aiming articulation. 
     Advantageously, the engagement of the second coupling mode causes:
         a plurality of pivoting connections to be locked;   the pulleys of each articulation included between the articulation comprising the motor, called the driving articulation, and the aiming articulation to be unlocked;   the upstream pulley of the aiming articulation to be kept locked;   the downstream pulley of the aiming articulation to be unlocked;   the pivoting connection of the aiming articulation to be kept unlocked.       

     Advantageously, the engagement of the second coupling mode simultaneously causes:
         the pivoting connection of the driving articulation to be locked;   the driving pulley to be unlocked relative to the articulation.       

     Advantageously, the device for locking/unlocking a pivoting connection of an articulation comprises at least one ratchet and a return spigot. 
     Advantageously, the device for locking the pivoting connection of the driving articulation comprises at least one ratchet, a return spigot and a retaining arm. 
     Advantageously, the device for locking the pivoting connection of the aiming articulation comprises a locking finger making it possible to release the pulley at a determined angle. 
     Advantageously, the structural elements comprise yokes and solar generators. 
     Advantageously, the motor and the driving pulley are placed at the root section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will appear with the aid of the following description made with respect to the appended drawings which represent: 
         FIG. 1 : a coupling system; 
         FIG. 2 : an articulated structure deployed according to the device of the invention; 
         FIGS. 3A ,  3 B,  3 C,  3 D: the structure according to the device of the invention in its life phase of aiming according to various locking modes; 
         FIG. 4 : a device for locking/unlocking the articulations and for coupling motor functions of the invention; 
         FIG. 5 : a first 3D view of an articulation at the root section of a satellite arm according to the invention; 
         FIG. 6 : a second 3D view of an articulation at the root section of a satellite arm according to the invention; 
         FIG. 7 : a 3D view of an aiming articulation of a satellite arm according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “structure” in the rest of the description means an articulated arm comprising a plurality of structural elements comprising yokes, solar generators, articulations, a locking/unlocking system and a coupling system. 
     In the rest of the description, the system that comprises a plurality of locking/unlocking devices positioned at the articulations of the articulated arms is called the locking/unlocking system. 
       FIG. 1  represents a coupling system  100  between three structural elements  1 ,  2 ,  3  connected two by two by articulations  4 ,  5 . Each articulation  4 ,  5  comprises a pivoting connection making it possible to have two structural elements pivot relative to one another. Moreover, the articulations  4 ,  5  each comprise a pulley. A cable  8  is wound round each of the two pulleys of each articulation  4 ,  5 . 
     Under the impulsion of a motive force rotating the first pulley, the cable drives the second pulley of the articulation  5 . 
     During the structure-deployment phase, the coupling system  100  allows, under the impulsion of the motive force, a coordinated deployment of the structural elements. The deployment takes place until the structural elements are positioned on the same axis. 
     The first pulley of the articulation  4  is secured to the pivoting connection of the structural element of this same articulation; the rotation of the first pulley rotates the structural element  2  relative to the structural element  1 . 
     The second pulley is secured to the pivoting connection of the articulation  5  of the structural element  3 . The rotation of the second pulley rotates the structural element  3  relative to the structural element  2 . 
     The absolute value of the angle α between the structural element  2  and the structural element  1  in the anticlockwise direction is equal to the absolute value of the angle between the structural element  2  and the structural element  3  in the anticlockwise direction. 
     The cable  8  operates the pivoting connection of the articulation  5  and causes the structural element  3  to pivot at an identical angle α. 
     The system of coupling by pulleys and by cable reverses the directions of the angles of two consecutive articulations. In the rest of the description this coupling is called the first coupling mode. It corresponds to the coupling of the angles connected together between the various structural elements to deploy the structure. It is used in a first life phase of the satellite which corresponds to the deployment of its arms. 
     The coupling system  100  of  FIG. 1  requires a locking device between the pivoting connection of the articulation  4  of the structural element  1  and the pulley of this same articulation. 
     When the deployment is complete, a second life phase then begins; it involves the aiming phase which corresponds to another operating mode of the device of the invention. A second coupling mode is then initiated as soon as the locking/unlocking system is engaged after the deployment. 
     The locking/unlocking device actuates so as to release the pivoting connection of the articulation  4  of the structural element  1  and the pulley of the same articulation. As a result, the pulley does not operate the pivoting connection. The unlocking of the pulley relative to the pivoting connection causes a locking of the pivoting connection connecting the structural element  1  and the structural element  2  which are then fixed relative to one another and the pulley is free. 
     The rotation of the pulley of the articulation  4  then operates the pulley of the articulation  5 . If the pulley of the articulation  5  is connected to the pivoting connection of the articulation  5 , the structural element  3  is rotated about the pivoting connection of the articulation  5 . 
     The first life phase between the structural elements is stopped by the locking/unlocking system which breaks the coupling principle of the first phase. The latter locking/unlocking system begins a second life phase which makes it possible to have a structural element  3  pivot about the articulation  5 , the rotation being engaged by means of the same motive force as that of the deployment applied to the pivoting connection of the articulation  4 . 
     In this case, the device of the invention with an activatable locking/unlocking system makes it possible to pass from a first life phase of deployment to a second life phase of aiming by using the same motive force during a deployment, the same structural elements and the same coupling elements. 
       FIG. 2  represents a device for deploying and aiming structural elements of a satellite according to the invention. 
     In one embodiment, so as to share the motor for the various life phases, the device of the invention comprises one of the locking/unlocking devices positioned at the articulations of the arm. On the one hand there are locking/unlocking devices for the pulleys and on the other hand locking/unlocking devices for the pivoting connections making it possible to deploy the whole structure in a first life phase and to aim all or some of the deployed structure in a second life phase which corresponds to the mission of the satellite. 
     In the first life phase, the structure is initially retracted. It is deployed under the impulsion of the second motor and of the coupling system  100  in its first mode. The pulley  22  is initially secured to the satellite fixed portion. The motor is secured to one side of the pulley  22  and secured to the structural element  26  for the other side. The motor has the same rotation axis  221  as the pivoting connection  31 . The motor rotates the structural element  26 . 
     The motor  21  is secured to the pulley  22  except for the reduction gears. 
     When the motor  21  is running, it makes it possible to rotate the pulley  22  relative to the structural body  26 . Since the pulley  22  is secured to the portion attached to the satellite  1 , the body  26  is deployed about the axis  221 . 
     The rotation of the pulley  22  relative to the structural element  26  causes, with the aid of the cable  223 , the rotation of the pulley  23  which itself rotates the structural element  27  securely connected to the pulley  23 . 
     The rotation of the structural element  26  securely connected to the pulley  23 ′ causes the rotation of the pulley  23 . The rotation of the pulley  23 ′ drives the cable  234  which itself drives the pulley  24  securely connected to the structural element  28 . The structure  28  is therefore rotated under the impulsion of the rotation of the pulley  24 . The rotation of the pulley  24 ′ then rotates under the impulsion of the rotation of the structure  28  and in turn rotates by means of the cable  245  the pulley  25  which is securely connected to the structural element  29  which pivots about the axis  251 . 
     The structural elements  26 ,  27 ,  28  and  29 , each being secured to a pulley, are deployed by action of the motor in a uniform manner under the stress of the coupling system  100 . 
     Each of the structural elements pivots about the axis of the articulation that separates it from the previous or next structural element. 
     The structural element  26  pivots about the axis  221 , the structural element  27  pivots about the axis  231 , the structural element  28  pivots about the axis  241  and the structural element  29  pivots about the axis  251 . 
     The absolute values of the angles of rotation  220 ,  230 ,  240  and  250  are equal by virtue of the coupling mechanism in its first mode provided by the pulleys and the cables and the motive force. On the other hand, the angles are in opposite directions in twos. The angle  220  is backwards, the angle  230  is anticlockwise, the angle  240  is clockwise and finally the angle  250  is anticlockwise. 
     When the deployment is complete, the first life phase is complete. Once the structural elements are deployed, they are in the same axis. The angles between each structural element is 180° in the example of  FIG. 2 . 
     The invention comprises locking/unlocking devices at the articulations making it possible to lock a portion of the articulations when the deployment is complete, thus closing the first life phase of the satellite. The second motor is also used for the second life phase. 
     In each articulation, the pulley and the pivoting connection can be independently locked or unlocked. One embodiment of the invention makes it possible to link the locking of a pulley in rotation to the unlocking of a pivoting connection. 
     Several variant embodiments are possible depending on the mission and depending on which portion of the structure it is desired to cause to pivot towards a target. 
     This involves configuring the locking/unlocking system so that one articulation unlocks its pivoting connection which will be operated by the force of the second motor. The locking/unlocking system therefore allows a second coupling mode in which a rotation of the pulley allows the rotation of a predefined pivoting connection. 
     The second motor  21  makes it possible to pivot the structure comprising a plurality of structural elements about an axis  221 , or about an axis  231  or else about an axis  241  when it is necessary to orient a portion of the structure  200  and in particular the solar generators  28  and  29  towards a designated target. The invention makes it possible to have a locking/unlocking system making it possible to pivot a portion, situated at the end of the structure, not necessarily at the root section  300  but at an articulation distant from the payload. This configuration makes it possible for example to get away from the shadow of the satellite which could cover the solar generators. Another example makes it possible to limit the specific inertia variations associated with the aiming of the solar generators. 
       FIGS. 3A ,  3 B,  3 C and  3 D represent various possible aiming configurations depending on the configuration of the locking/unlocking system. 
       FIG. 3A  represents the structure when it is fully deployed; it is then ready to begin its second life phase. 
       FIG. 3B  represents the structure when it aims at a target; the pivoting occurs between the first and the second yoke. 
       FIG. 3C  represents the structure when it aims at a target; the pivoting occurs between the second yoke and the first solar generator. 
       FIG. 3D  represents the structure when it points at a target; the pivoting occurs at the root section  300  between the payload of the satellite and the first yoke. 
     The locking/unlocking system may comprise several application modes depending on the variant embodiments and depending on the position of the locking/unlocking devices at the articulations. 
     In a first variant embodiment, as shown in  FIG. 3C , a locking/unlocking device unlocks the pulley with the articulation of the root section  300  while locking its pivoting connection. The motor remains secured to the pulley and separates from the pivoting connection with the structural element  26 . The motor no longer rotates the structural element  26 , which is now fixed, but only the pulley  22  (see  FIG. 2 ). 
     As best shown in  FIG. 2 , the motor  21  operates the pulley  22 . By pivoting, the pulley  22  actuates the cable  223  around the pulley  23  which itself starts to rotate. 
     At the second articulation  232 , there are two pulleys:
         a first pulley  23  at a first end of the articulation  232  connected to the pulley  22  via the cable  223  and;   a second pulley  23 ′ situated at the other end of the articulation  232 .       

     In this first variant of this first mode, a locking/unlocking device makes it possible to lock the articulation  232  while unlocking the pulleys  23  and  23 ′ of the articulation. In this case, following the deployment, the connection between the element  26  and the element  27  is a fixed connection. There is therefore no more pivoting of this articulation. 
     The rotation of the pulley  23  rotates the pulley  23 ′ about the axis  231 . The cable  234  in turn rotates the pulley  24  which is unlocked from the pulley  24 ′. The pulley  24 ′ is connected to the pivoting connection of the structural element  28 . 
     The two solar generators  28 ,  29  are secured together following the deployment of the structure, the pivoting connection connecting the structural elements  28  and  29  being locked. 
     The structural element  28  is therefore engaged in rotation about the axis  241 . The structure then consisting of the two solar generators  28  and  29  and the pulley  25  pivots under the action of the motor. 
     As shown in  FIG. 3B , a second variant of this first mode is to activate a locking/unlocking device which makes it possible, at the end of the deployment life phase, to unlock the pulley  23 ′ of the articulation  232  without locking the articulation. In this variant, the rotation of the motor  21  will therefore have the effect of turning only the articulation  232  about its axis  231  by means of the pulley  22 , the coupling  223  and the pulley  23 . Following the deployment, the elements  27 ,  28  and  29  are fixedly connected by the locking/unlocking device which has removed the pivoting connections between the structural elements. 
     As shown in  FIG. 3D , a third variant is not engaging the unlocking at the root section  300  between the pivoting connection of the structural element  26  and the motor. This makes it possible to actuate the pivoting of the structure simply by acting on the motor, the structural elements  26 ,  27 ,  28  and  29  being in this instance connected via connections that are fixed together. The structure then pivots about the axis  221  and corresponds to the situation in  FIG. 3D . 
     In a fourth variant embodiment, the device, once deployed, makes it possible to activate the locking of the articulation  232  and  233  and to unlock the pulleys  23 ,  23 ′,  24  and  24 ′. In this case, following the deployment, the connection between the element  26  and the element  27  is fixed and the connection between the elements  27  and  28  is fixed. There is therefore no longer any pivoting of these articulations. 
     The rotation of the motor  21  rotates the pulley  22  which rotates the pulley  23  via the coupling  223 . 
     The rotation of the pulley  23  rotates the pulley  23 ′ about the axis  231 . The cable  234  in turn rotates the pulley  24  rotates the pulley  24 ′. The rotation of the pulley  24 ′ operates the cable  245  which in turn operates the pulley  25 . The pulley  25 , in this variant, is secured to the pivoting connection belonging to the structural element  29 . 
     In consequence, the panel  29  is rotated under the impulsion of the motor. 
     The two solar generators  28 ,  29  are then no longer in the same plane. This situation is not used very much operationally, but the invention allows all the possible configurations depending on the configuration of the locking/unlocking devices of the pulleys and of the pivoting connections. 
     The structural element  29  is therefore engaged in rotation about the axis  251 . The structure, then consisting of a single solar generator  29 , pivots under the action of the motor. 
     Other combinations of these variants are also possible according to the same operating principle of locking/unlocking. 
       FIG. 4  represents in detail the mechanism of the second coupling and locking mode according to the invention. 
     The pulley  22  in rotation driven by the driving means  21  makes it possible to pivot the pulley  23 . 
     Several variants expressed in  FIGS. 3A ,  3 B,  3 C and  3 D of the invention make it possible to aim the structure along a preferred axis. 
     One particular embodiment of the invention makes it possible to lock the pivoting connection  31  and  31 ′ following the deployment phase of the structure. The locking of the connection  31 ,  31 ′ secures the payload of the satellite  30  to the structural element  26 . The pivoting connection  31 ,  31 ′ is therefore a fixed connection. 
     The motor  21  then drives only the pulley  22 . 
     The invention makes it possible simultaneously to lock the pivoting connection  31 ,  31 ′ while unlocking the pulley  22  with respect to the articulation by a locking/unlocking device  50 . The pulley  22  pivots without causing the pivoting connection of the articulation to pivot. 
     Since the structural element  26  is then fixed relative to the payload  30 , the pulley  23 ′ must be released from the structural element  26  in order to allow the rotation about the axis  231  without driving the coupling  234 . This function is performed by the locking/unlocking device  51 . 
     In this situation, the cable  223  drives the pulley  23  secured to the articulation and to the pivoting connection  32 . The structural element  27  then pivots about the axis  231 . This configuration makes it possible to articulate the structure comprising the elements  27  and following after the articulation  32 ,  32 ′. 
     In this embodiment, the structure therefore pivots about the axis  231   
     The following articulations, notably the articulation  33 ,  33 ′ are locked in this embodiment. This configuration makes it possible to orient the structure so as to aim it at a desired target. 
     In another embodiment, a locking/unlocking device can be activated at the articulations  32  and  32  which then form a fixed connection. In this case, by keeping the locking configuration of the articulation at the root section  300 , the invention makes it possible to pivot the structure at the articulation  33 ,  33 . The unlocking of the pulley  22  at the root section  300  causes the unlocking of the pivoting connection  33 ,  33 ′. 
     In one embodiment, a locking/unlocking device can be produced from a cam and a locking finger. 
     One advantage of the invention is that it allows the use of a single motor and of a single coupling for the life phase corresponding to the deployment and the life phase corresponding to the aiming of the structure. 
     One advantage of this solution is that it minimizes the costs, lightens the device of the invention and more particularly the satellite. 
     One advantage is also the simplicity of application and the possibility of configuring the locking/unlocking system with respect to the mission of the satellite. 
     Finally another advantage is the robustness of the system; by sharing the driving means, the risks of failures are reduced. 
       FIG. 5  represents a 3D view of an articulation at the root section  300  of a deployable arm of a satellite according to the invention. 
     A root section  300  is used to make the connection with the satellite. A first locking device  53  at a first portion of the root section  300  makes it possible to create a fixed connection with the satellite portion  30 . A second portion of the root section  300  is situated on the other side of the articulation, on the same side as the pulley  22  which drives the cables  223 . 
     In the example of  FIG. 5 , the second portion of the root section  300  comprises a locking/unlocking system  50  that can be actuated from a retaining arm  54  which fits into the central portion  400  of the pulley  22 . The locking/unlocking system  50  allows the locking of the articulation and the unlocking of the pulley  22  after the first life phase. 
     The retaining arm  54  of the pulley  22  is secured to the spindle of a ratchet  61  (see  FIG. 6 ) for locking the articulation, the latter not being shown in  FIG. 5 . 
     When the ratchet  61  (see  FIG. 6 ) locks the articulation by turning on its spindle, it makes it possible to rotate the retaining arm  54  of the pulley. Consequently, it makes it possible to release the pulley  22  from the articulation. 
       FIG. 6  represents another 3D view of the same articulation of  FIG. 5 . The locking/unlocking system  50  comprises a locking finger  65  and a ratchet  61 . 
     In this view, the fixed portion  30  of the satellite is situated underneath in  FIG. 6 . 
     When the ratchet  61  turns about its spindle, it places itself in opposition to the movement of a return spigot  64  of the movable portion of the articulation. The ratchet  61  makes it possible therefore to lock the articulation and by turning, it simultaneously releases the pulley  22 . 
     One advantage is that the locking of the articulation and the unlocking of the pulley take place simultaneously. 
       FIG. 7  represents the articulation  232  which joins two structural elements to the arm of the satellite. This articulation is also called an aiming articulation. The locking/unlocking system  51  makes it possible to unlock the pulley relative to the articulation. This configuration allows the structural portion  27  to be aimed from the coupling  234  (as shown in  FIG. 4 ).