WO2021244843A1

WO2021244843A1 - Force sensor for cable actuator

Info

Publication number: WO2021244843A1
Application number: PCT/EP2021/063067
Authority: WO
Inventors: Philippe Garrec
Original assignee: Commissariat A L`Energie Atomique Et Aux Energies Alternatives
Priority date: 2020-06-02
Filing date: 2021-05-18
Publication date: 2021-12-09
Also published as: FR3110947A1; FR3110947B1

Abstract

Disclosed is a cable actuator (100) comprising: - a frame (10); - a screw (2) rotatably mounted on the frame (10) and extending along a first axis (Ox); - a nut (4) cooperating with the screw (2); - means for determining (93) a force applied to the output (22.4) of the cable actuator (100) as a function of an angular displacement (α) of the nut (4).

Description

Force sensor for cable actuator

FIELD OF THE INVENTION

The invention relates to a force sensor for a cable actuator comprising a screw / nut assembly, the nut of which is movable in translation and coupled by a cable to an element to be moved. The invention relates more particularly to force sensors for a cable actuator, the cable of which performs an anti-rotation function of the nut with respect to the screw. BACKGROUND OF THE INVENTION

Cable actuators are known comprising a screw mounted on a frame and a nut cooperating with the screw. The nut is associated with anti-rotation means so that a relative rotation of the screw and of the nut causes an axial displacement of the nut. One or more cables associated with the nut are connected to an output of the actuator which can be rotary (when the cables are connected to pulleys) or linear (when the cables are connected directly to the load to be handled). The force sensors for such actuators are generally mounted directly on the output of the actuator and prove to be bulky, expensive and / or imprecise. In addition, these force sensors being directly coupled to the segments of the articulated arm, they withstand shocks and vibrations originating from the segments and the loads which they support. To avoid too great a fragility, they must therefore be oversized, which increases their volume and decreases their sensitivity. Thus, the force control of cable actuators, which have interesting characteristics in particular in terms of compactness, is difficult or expensive, which restricts their distribution.

It is known from document WO2019 / 029976 an actuator with cable of the aforementioned type comprising a cable arranged to exert forces opposing rotation of the nut by the screw.

OBJECT OF THE INVENTION The object of the invention is to improve the precision and the manufacturing and / or maintenance costs of a cable actuator.

BRIEF DESCRIPTION OF THE INVENTION For this purpose, there is provided a cable actuator comprising a frame, a screw rotatably mounted on the frame and extending along a first axis, a nut cooperating with the screw, a first cable coupled to it. 'nut and operatively connected to an output of the actuator, a second cable coupled to the nut and operatively connected to an output of the actuator, a motor arranged to drive the screw in rotation. The first cable is arranged to exert forces opposing a rotational drive of the nut by the screw to constitute anti-rotation means so that a rotation of the screw or the nut under the action of the motor causes a displacement of the nut on the screw. The actuator according to the invention comprises means of determining an angular displacement of the nut around the first axis relative to the frame, means of determining a force applied to the output of the actuator as a function of the angular displacement of the nut. 'nut around the first axis. The means for determining angular displacement comprise a carriage mounted to translate in a direction substantially parallel to the first axis and which comprises a first and a second cable return.

A third cable return and a fourth cable return are connected to the frame. One of the first referrals from cable, second cable return is mounted movably relative to the carriage or one of the third cable return or fourth cable return is mounted movable relative to the frame. The actuator also comprises a third cable which comprises a first strand whose first end is coupled to the nut and a second strand whose second end is coupled to the nut, the third cable cooperating with the first cable return. , the second cable return, the third cable return and the fourth cable return. One of the first cable returns or second cable return is a cable return instrumented to measure its displacement relative to the carriage, or one of the third cable returns or fourth cable return is a cable instrumented to measure its displacement relative to the chassis.

An actuator is thus obtained in which the measurement of the force applied to the output is carried out using a simple device based on position measuring means which are generally more reliable means than known force sensors. The actuator according to the invention also benefits from the amplification factor that the pitch of the screw causes on the displacement of the nut subjected to the load applied to the output of the actuator. The actuator is little disturbed by the light environment when it includes a rotary encoder.

Advantageously, the return of the instrumented cable comprises a linear sensor, preferably a contactless sensor.

According to a preferred embodiment, the first strand of cable and the second cable strand extend on either side of a plane comprising the first axis.

The parasitic torques are reduced when the actuator comprises a first raceway which cooperates with at least one wheel integral with the carriage.

Other characteristics and advantages of the invention will emerge on reading the following description of particular non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made to the appended figures, among which:

[Fig. 1] Figure 1 is a schematic perspective view of a first embodiment of a cable jack according to the invention; [Fig. 2] FIG. 2 is a schematic sectional view along a plane III-II of the embodiment of FIG.

1;

[Fig. 3] Figure 3 is a schematic perspective view of a second embodiment of the invention; [Fig. 4] Figure 4 is a schematic perspective view of a third embodiment of the invention; [Fig. 5] FIG. 5 is a schematic sectional view along a plane VI-VI of the embodiment of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. 1, and according to a first embodiment of the FIG. invention, the actuator of the invention, generally designated 100, comprises a frame 10, here a portion of the right cylinder comprising a base 12 at the center of which a bearing 13 accommodates a screw 2 to rotate about a first axis Ox horizontal. Screw 2 is a p2 pitch ball screw which is rotated by an electric motor 3 comprising a first rotary encoder 3.1. A nut 4 cooperates with the screw 2 and comprises a first eyelet 5 projecting radially from the nut 4. A first cable 6 extends parallel to the first axis Ox and comprises a first section 6.1 held at its first end 6.2 in the first eyelet 5 by a first crimp 7.1. The second end 6.3 of the first section 6.1 of the first cable 6 is crimped on a first pulley 14 integral with a first shaft 16 rotatably mounted on the frame 10 along an axis perpendicular to the first axis Ox. The first cable 6 also comprises a second section 6.4 of first cable 6 extending parallel to the first axis Ox on either side of a plane P orthogonal to the first axis Ox comprising the first eyelet 5 and which is held in its first end 6.5 in the first eyelet 5 by the first crimp 7.1. The second end 6.6 of the second section 6.4 of the first cable 6 is crimped on a second pulley 15 integral with a second shaft 17 mounted to rotate on the frame 10 along an axis perpendicular to the first axis Ox.

The nut 4 comprises a second eyelet 8 projecting radially from the nut 4 so as to be diametrically opposed to the first eyelet 5. A second cable 9 extends parallel to the first axis Ox and comprises a first section 9.1 of second cable 9 maintained at its first end 9.2 in the second eyelet 8 by a second crimp 7.2. The second end 9.3 of the first section 9.1 of the second cable 9 is connected to a third pulley 18 integral with the first shaft 16 rotatably mounted on the frame 10 along an axis perpendicular to the first axis Ox.

The second cable 9 also includes a second section 9.4 extending parallel to the first axis Ox on either side of a plane P orthogonal to the first axis Ox comprising the second eyelet 8 and which is held at its first end 9.5 in the second eyelet 8 by the second crimp 7.2. The second end 9.6 of the second section 9.4 of the second cable 9 is crimped on a fourth pulley 19 integral with the second shaft 17 mounted to rotate on the frame 10 along an axis perpendicular to the first axis Ox. The first cables 6 and second cable 9 are each preloaded at a precharging voltage t6.9 equal to half of the total precharging voltage to, for example by acting on the distance separating the first shaft 16 and the second. shaft 17. The actuator 100 also comprises a fifth pulley 20 and a sixth pulley 21 respectively integral in rotation with the first shaft 16 and the second shaft 17. A third cable 22 extends between the fifth pulley 20 and the sixth pulley 21 and comprises a first end 22.1 crimped on the fifth pulley 20 and a second end 22.2 crimped on the sixth pulley 21.

A support 22.3 is crimped onto the third cable 22 to constitute an output 22.4 of the actuator 100 intended to be connected to a load 101 to be moved. The motor 3 and its encoder 3.1 are connected to a control unit 90 comprising a unit 91 for determining the position of the nut 4, a comparator 92, a computer 93, a memory 94 and a display 95. A control handle 96 is also connected to the control unit 90.

The first cable 6 and the second cable 9 being stretched, they exert forces opposing a drive in rotation of the nut 4 by the screw 2 during a rotation of the motor 3 in both directions of movement of the nut 4 relative to the screw 2. They then perform - in addition to their function of transmitting displacement forces from the nut 4 to the load 101 - an anti-rotation function such that a rotation of the screw 2 under the action of the motor 3 causes a displacement of the The nut 4 relative to the screw 2. The cable actuator 100 of the invention allows movement of the load 101 in two opposite directions.

As can be seen in FIG. 1, a first raceway - here a first square steel rail 25 - integral with the frame 10 extends in a direction substantially parallel to the axis Ox. A carriage 30 comprises a frame 31 on which are rotatably mounted a first roller 32 and a second roller 33. The first roller 32 and the second roller 33 co-operate in rolling motion with the rail 25. The carriage 30 comprises a first return wheel. cable - here in the form of a seventh pulley 34, rotatably mounted on the frame 31 - and a second cable deflection - here in the form of an eighth pulley 35, rotatably mounted on the frame 31. L The actuator 100 also comprises a third cable return - here in the form of a ninth pulley 36, mounted for rotation around a third shaft 36.1. The third axis 36.1 is integral with a yoke 37 mounted to float relative to the frame 10. A fourth cable return here in the form of a tenth pulley 38 is mounted to rotate around a fifth shaft 38.1 integral with the frame 10. A third cable 40 comprises a first strand 41 whose first end 41.1 is coupled to the nut 4 and a second strand 42, the second end 42.1 of which is also coupled to the nut 4. The third cable 40 extends from the first end 41.1 to engage with the seventh pulley 34. The third cable 40 then extends substantially parallel to the first axis Ox to wind on the ninth pulley 36 around which the third cable 40 is engaged to extend substantially parallel to the first axis Ox to join the tenth pulley 38. After a revolution of about one hundred and four - twenty degrees around the tenth pulley 38, the third cable 40 engages on the eighth pulley 35 before joining the nut 4 to which the second end 42.1 of the third cable 40 is coupled. The first end 41.1 and the second end 42.1 of the third cable 40 are, here, coupled to the periphery of the nut 4 (see FIG. 2).

As visible in Figures 1 and 2, the first strand 41 and the second strand 42 extend on the same side of a plane comprising the first axis Ox and parallel to the first shaft 16 and to the second shaft 17.

The seventh pulley 34, the eighth pulley 35, the ninth pulley 36 and the tenth pulley 38 constitute a first third cable return 40, a second third cable 40, a third third cable 40 and a third cable return, respectively. fourth return of third cable 40.

The actuator 100 also comprises a first drum 50 mounted to rotate around a sixth shaft 51 of a second rotary encoder 52 integral with the frame 10. The first end 53.1 of a rope 53 is fixed to the yoke 37. The rope 53 makes a full revolution on the second drum 50 and is connected at its second end 53.2 to the first end 60 of a tension spring 61. The second end 62 of the tension spring 61 is connected to the frame 10. Thus, the ninth pulley 36 is kept floating with respect to the frame 10 thanks to the combined pulls of the third cable 40 and of the rope 53.

The third cable 40 is preloaded by the traction of the spring 61 which transmits its traction to the yoke 37 by the rope 53. Although the traction of the spring 61 produces a disturbing torque on the nut 4, this can be neglected by look at the torque generated by the load 101 when a low force spring 61 is chosen and all the pulleys are mounted so as to reduce friction, for example on ball bearings. The yoke 37 is kept in balance by the pulling of the spring 61. Advantageously, a yoke 37 / pulley 36 assembly will be chosen which is sufficiently light not to cause a noticeable deflection of the rope 53. Alternatively, or in a complementary manner, a carriage can be provided. 30 rolling with low friction on the rail 25. Thus, a rotation of the nut around the axis Ox simultaneously displaces the ends 41.1 and 42.1 of the cable 40 by the same value which causes a translation of the yoke 37. supporting the axis 36.1 of the pulley 36. The displacement of the yoke 37 is converted into a rotation, by the drum 50. The rotation of the drum 50 is measured by the encoder 52.

On the other hand, the linear displacement of the nut 4 causes the displacement of the carriage 30 and the circulation of the cable 40 on the seventh pulley 34, eighth pulley 35, ninth pulley 36 and tenth pulley 38 does not cause any movement. the axis 36.1 of the pulley 36 and the encoder 52 then records no movement.

A processing module 26 connected to the second encoder 52 converts the rotation of the second encoder 52 into a rotation of the nut 4 about the axis Ox.

The module 26 is connected to the control unit 90. In operation, a user acts on the handle 96 to control a displacement of the load 101. The unit 90 then controls a rotation of the motor 3. Under the effect of the motor 3, the rotation of the screw 2 causes an identical rotation of the nut 4 due to the contact friction between the screw 2 and the nut 4. This rotation puts in tension the first cable 6 and the second cable 9 which then come to exert forces opposing a rotational drive of the 'nut 4 by screw 2. The first cable 6 and the second cable 9 then perform - in addition to their function of transmitting displacement forces to the load 101 - an anti-rotation function so that a rotation of the screw 2 under the action of the motor 3 causes a linear displacement of the nut 4 relative to the screw 2. In a given position of the nut 4, in the presence of the load 101, the torque applied to the nut 4 increases according to the value of the load 101 which causes the nut to rotate 4 around the axis Ox to a position of equilibrium with the return torque generated by the first strand 41 and the second strand 42. The module 26 transmits the value of the estimate of the translation of the yoke 37- which corresponds to a displacement of the pulley 36 and therefore to a rotation of the nut 4 around the axis Ox- to the computer 93. The unit 91 then determines the angle of rotation of the nut 4 around the axis Ox from the reading of the encoder 52 and from a calculation model taking into account the radius of the drum 50 and the position of the ends. 41.1 and 42.1 of the first strand 41 and of the second strand 42 on the nut 4.

The computer 93 then determines a force applied to the support 22.3 by the load 101 as a function of the value α of the angular displacement of the nut 4 around the axis Ox.

Such a determination can in particular be made by solving the following nut balancing equation 27: [Math 1]

in which :

- C corresponds to the torque applied to the first pulley 14,

- R corresponds to the radius of the first pulley 14,

- E corresponds to the distance between the points of tangency of the first cable 6 to the first pulley 14 and the second pulley 15,

- α corresponds to the angle of rotation of the nut 4 around the axis Ox relative to the frame 10,

- ρ corresponds to the anchoring radius of the first cable 6 with respect to the axis of the nut 4 (or screw),

- d corresponds to the distance from the center of the nut 4 to the point of tangency of the first cable 6 on the first pulley 14. - corresponds to the reduced pitch of the screw 2-nut 4 system, that is to say p2 / 2n;

- k ₁ corresponds to the stiffness of the shortest strand of the first cable 6 between that separating the nut 4 from the first pulley 14 and that separating the nut 4 from the second pulley 15;

- k ₂ corresponds to the stiffness of the longest second cable strand 9 between the one separating the nut 4 from the first pulley 14 and that separating the nut 4 from the second pulley 15; t ₀ corresponds to the total preload tension distributed over the first and second cables 6 and 9.

The approximations leading to this equation or allowing its resolution (limited developments for example) may depend on the linear position of nut 4 on screw 2.

A cable actuator 100 is thus obtained, the second encoder 52 of which makes it possible to estimate the tensions in the first cable 6 and the second cable 9 and thus to deduce therefrom a force exerted on the output 22.4 of the actuator 100.

The actuator 100 according to the first embodiment of the invention also makes it possible to check the preload of the cables. Indeed, the balancing equation above shows the total preload to distributed over the first cable 6 and second cable 9 and it is thus possible to evaluate this preload t ₀ using the method following.

According to a first step, the nut is brought to a predetermined position relative to the frame, here at the second end 2.2 of the screw 2.

According to a second step, the support 22.3 is immobilized by bringing it into abutment against a relatively fixed element. to the frame 10.

According to a third step, the motor 3 is controlled so that it applies a _{predetermined torque C p} to the screw 2. The torque Cp is, here, applied by controlling the application of a _{known supply current I p} to the motor. 3, the value of the torque applied by the motor 3 to the screw 2 is determined using the characteristic relating the input current and the output torque of the motor 3. According to a fourth step, the module 26 transmits the value of the estimate of the distance D _23-24 to the computer 93 which converts it into an effective angular position of the nut 4 around the axis Ox.

According to a fifth step, the comparator 92 compares the effective position of the nut 4 relative to the frame 10 with the predetermined position of the nut 4 relative to the frame 10 in order to obtain a value δ _ang4 of the deviation of the angular position of nut 4.

According to a sixth step, the computer 93 determines the value of the total preload to distributed over the first cable 6 and second cable 9 as a function of the value δ _ang4 of the deviation of the angular position of the nut 4.

The determined value of the preload top allows to check that it conforms to a reference value t _0ref The elements identical or similar to those previously described will bear a numerical reference identical to this one in the following description of the other two embodiments of the invention.

According to a second embodiment shown in FIG. 3, the rope 53 comprises a reflector 70 - here a white metal sheet - which extends in a substantially plane. parallel to the Oz axis. A laser transmitter / receiver 71 integral with the frame 10 is connected to a processing module 72 connected to the laser transmitter / receiver 71 measures the travel time of a laser beam emitted by the transmitter / receiver 71 and reflects by reflector 70 and converts this travel time into an estimate of the distance D _70-71 separating the emitter / receiver 71 and the reflector 70. The module 72 is connected to the unit 90 whose computer 93 converts the distance D _70-71 in a displacement α of the axis 36.1 of the pulley 36.

The determination of the force on the output 22.4 of the actuator 100 is done in the same way as for the first embodiment of the invention described above. According to a third embodiment shown in FIG. 4, the first strand 41 and the second strand 42 extend on either side of a plane P1 comprising the first axis Ox and which is parallel to the first shaft 16 and to the second shaft. 17. The carriage 30 comprises a third roller 39 which cooperates in rolling motion with a second square rail 28. A tenth pulley 70 positioned at one end of the second rail 28 returns the third cable 40 from the eighth pulley 35 to the tenth pulley 38.

Of course, the invention is not limited to what has just been described, but encompasses any variant coming within the scope of the invention defined by the claims.

Specifically,

- although here, the frame is cylindrical in shape, the invention also applies to other shapes of frame such as for example a plate, a square tube, any shape whatsoever; - although here the axis of rotation of the screw extends horizontally, the invention also applies to other orientations of the axis of rotation of the screw such as for example a vertical orientation, at forty -five degrees or any;

- Although here the cable actuator comprises two cables connected to the nut, the invention also applies to an actuator whose nut is connected to a single cable or to more than two cables; - although here the output of the cable actuator is connected to a cable to provide a translational movement, the invention also applies to an output integral in rotation with one of the shafts of the actuator to provide rotational movement; although here the user acts on a handle to control the actuator, the invention also applies to other control means such as, for example, a switch or a voice command;

- although here the determination of the force exerted by the actuator has been described when the actuator is stabilized in a given position, the invention also applies to a dynamic measurement of the force during the movement. the actuator;

- although here the method of determining the preload of the cables has been described in connection with the first embodiment of the actuator, the method of determining the preload of the cables also applies to the other embodiments of the invention;

- although here the output of the actuator is immobilized when the nut is at the second end of the screw, the invention also applies to other predetermined positions of the nut (or the outlet) relative to the frame;

- Although here the actuator comprises a ball screw, the invention also applies to other types of screw such as for example a single threaded screw, or a roller screw;

- although here the reflector is a white metal sheet, the invention also applies to other types of reflectors such as for example a mirror, a polished sheet, a simple sheet or any element whose surface provides sufficient reflection a wave to allow the measurement of its travel time;

- although here the actuator comprises a laser beam distance sensor, the invention also applies to other types of contactless linear sensor such as, for example, other types of sensors comprising a transmitter. / wave receiver such as an ultrasound emitter / receiver, visible or infrared light emitter / receiver, incremental directly attached to the pulleys; - although here the first cable is hitched to the nut by crimping to an eye integral with the nut, the invention also applies to other means of hitching a cable to the nut such as for example a ring welded to the nut, a crimp in a hole made in the nut, dead turns in a hole, an attachment to an intermediate support;

although here the cables extend parallel to the first axis, the invention also applies to other configurations of cables in which the cable can adopt any orientation with respect to the first axis;

- although here all the actuator cables are precharged, the invention also applies to a single precharging cable, no precharging cable or only a fraction of the precharged cables;

- although here the screw is mounted in a bearing, the invention also applies to other means of rotationally mounting the screw on the frame such as for example a bronze bush, a needle bearing, with balls or tapered rollers;

- although here the method of measuring a preload has been described with reference to the first embodiment of the invention, such a method is clearly applicable to any variant coming within the scope of the invention as defined by the claims;

- Although here the rollers cooperate with a square rail, the invention also applies to other types of translational guide means such as for example a shoe, a lubricated bush, a finger in a slot;

- although here the actuator comprises pulleys to make the cable returns, the invention also applies to other types of cable return such as for example a shaft mounted for rotation, a metal eyelet or synthetic, a fixed shaft made of a bronze or PTFE-type friction-limiting material;

- Although here the rope is connected to one end of a tension spring, the invention also applies to other cable return means such as for example a spiral spring incorporated in the drum;

- although here the actuator comprises a rope connected to an instrumented drum, the invention also applies to other means for measuring the displacement of the third pulley, such as for example a wheel / worm assembly or a wheel / rack assembly;

- although here the ninth pulley is provided with a sensor measuring its displacement relative to the frame, the invention also applies to other installations of the sensor, such as for example a sensor measuring the displacement of the frame. tenth pulley, of the seventh, eighth or ninth pulley;

- although here the third pulley is mounted floating relative to the frame, the invention also applies to other means of movable connection of the third pulley to the frame such as for example a sliding connection by carriage, a magnetic levitation, or a clevis mounted to pivot relative to the frame.

Claims

1. Cable actuator (100) comprising:

- a frame (10);

- a screw (2) rotatably mounted on the frame (10) and extending along a first axis (Ox);

- a nut (4) cooperating with the screw (2);

- a first cable (6) coupled to the nut (4) and functionally connected to an output (16, 17, 22.4) of the actuator (100);

- a second cable (9) coupled to the nut (4) and functionally connected to the output (22.4) of the actuator (100);

- a motor (3) arranged to drive the screw in rotation

(2); characterized in that the first cable (6) is arranged to exert forces opposing a rotational drive of the nut (4) by the screw (2) to constitute anti-rotation means so that a rotation of the screw (2) under the action of the motor (3) causes a displacement of the nut (4) on the screw (2), and that

- the cable actuator (100) also includes:

- means of determining (30, 37, 52, 70, 71) an angular displacement (a) of the nut (4) around the first axis (Ox) relative to the frame (10),

; and

- means for determining (93) a force applied to the output (22.4) of the cable actuator (100) as a function of the angular displacement (a) of the nut (4) around the first axis (Ox), in which means for determining (30, 37, 52, 70, 71) the angular displacement (a) of the nut (4) comprises: - a carriage (30) mounted to translate in a direction substantially parallel to the first axis (Ox) and which comprises a first cable return (34) and a second cable return (35), - a third cable return ( 36) connected to the frame and a fourth cable return (38) connected to the frame (10), one of the first cable return (34), second cable return (35) is movably mounted relative to the carriage (30) or one of the third cable return (36) or fourth cable return (37) is movably mounted relative to the frame (10); the actuator also comprises a third cable (40) which comprises a first strand (41) whose first end (41.1) is coupled to the nut (4) and a second strand (42) whose second end (42.1) ) is coupled to the nut (4), the third cable (40) cooperates with the first cable return (34), the second cable return (35), the third cable return (36) and the fourth cable return (38); one of the first cable return (34) or second cable return (35) is a cable return instrumented to measure its displacement relative to the carriage (30), or one of the third cable return (36 ) or fourth cable return (38) is a cable return instrumented so as to measure its displacement relative to the frame (10)

2. Cable actuator (100) according to claim 1, wherein the instrumented cable return comprises a rotary encoder (52).

3. Cable actuator (100) according to any preceding claim, wherein the instrumented cable return comprises a linear sensor (70, 71).

Cable actuator (100) according to claim 3, wherein the linear sensor (70, 71) is a non-contact sensor.

5. Cable actuator (100) according to any preceding claim, wherein the first cable strand (41) and the second cable strand (42) extend on either side of a plane comprising the first axis (Ox).

6. Cable actuator (100) according to claim 1, wherein the actuator comprises a first raceway (25) which cooperates with at least one wheel (32, 33) integral with the carriage (30).

7. Cable actuator (100) according to any one of the preceding claims, wherein the first cable return (34) and / or the second cable return (35) and / or the third cable return (36) and / or the fourth cable return (38) comprises a pulley.

8. Cable actuator (100) according to any preceding claim, wherein the first strand (41) and the second strand (42) extend on either side of a plane (PI) comprising the first axis (Ox).