Method for controlling a microelectromechanical system

Abstract

The present invention relates to a method for controlling a microelectromechanical system by means of an electrical control signal alternating between a maximum voltage value (Vmax) and a minimum voltage value (Vmin), wherein during the transition from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), the value of the voltage of the electrical control signal decreases monotonically from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), the signal being: a first slope between a maximum voltage value (Vmax) and a first voltage threshold (Vend); a second slope between the first voltage threshold (Vend) and the second voltage threshold (Vstart), the second slope having an absolute value less than the first slope; and a third slope between a second voltage threshold (Vstart) and a minimum voltage value (Vmin), the third slope being higher in absolute value than the second slope.

Description

[Technical field]

[0001] The present invention relates to the field of microelectromechanical systems. [Background technology]

[0002] Microelectromechanical systems (or MEMS) are miniature systems manufactured by etching semiconductor materials. These microsystems contain mechanical parts with micrometer dimensions and use electricity as an energy source for operation.

[0003] French patent application FR 2 874 907 describes a drive device, for example formed by etching a chip of a semiconductor material such as silicon. The drive device comprises an actuator composed of a drive tooth capable of successively engaging with a gear wheel, a first element module capable of moving the drive tooth along a first axis (radial axis) and a second element module capable of moving the tooth along a second axis (tangential axis) relative to the gear wheel. The first and second element modules are electrostatic modules having a structure made of intermeshing combs.

[0004] The first element module and the second element module are controlled by phase-shifted, alternating addressing signals to move the drive tooth in a periodic motion having a hysteresis orbit. During this periodic motion, the drive tooth alternates between drive and disengagement phases. In each cycle, the drive tooth engages a tooth of the gear and rotates the gear one step. The cycle is repeated such that the drive tooth engages successive teeth of the gear, thereby driving the gear in a stepwise rotational motion.

[0005] During the drive phase, the drive teeth move in a first direction as a result of electrostatic forces generated by the interdigitated combs, while during the disengagement phase, the drive teeth move in a second direction opposite to the first direction as a result of elastic return forces generated by the suspensions of the interdigitated combs.

[0006] This type of drive device can be used to drive the gears of a timepiece mechanism instead of a conventional watch motor and generally has the advantage that it reduces the number of mechanical parts needed to rotate the gears.

[0007] One problem encountered with this type of drive device is that in each elementary movement (i.e. in the first or second direction), the actuator may be subject to bouncing or vibration. Bounce is generally manifested at the end of the stroke, when the moving part abuts against a fixed part of one of the modules. Vibration is also manifested at the end of the stroke, when the moving part returns to its equilibrium position as a result of the elastic return force.

[0008] However, these bounces and / or these residual vibrations are detrimental to the proper operation of the actuator for several reasons.

[0009] On the one hand, these bounces and / or the appearance of these vibrations cause an increase in the duration of stabilization of the elementary movements, limiting the frequencies at which the drive device can be controlled.

[0010] On the other hand, bouncing causes repeated impacts between mechanical parts, deteriorating the contact surfaces between these mechanical parts and, as a result, reducing the life span of the microelectromechanical system. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] French Patent Application Publication No. 2874907 Summary of the Invention [Problem to be solved by the invention]

[0012] One object of the present invention is to propose a solution for limiting the phenomenon of residual vibrations and / or bouncing in microelectromechanical systems. [Means for solving the problem]

[0013] This problem is solved within the scope of the present invention due to a method for controlling a microelectromechanical system, the microelectromechanical system comprising a support and an actuator, the actuator comprising: a fixed portion fixedly attached to the support; A movable part movably mounted relative to the support; and a suspension connecting the movable part to the support.

[0014] The control method includes the steps of applying an electrical control signal between the fixed part and the movable part, the control signal alternating between maximum and minimum voltage values ​​such that the movable part moves relative to the fixed part; in a first direction, movement of the movable part relative to the fixed part causes elastic deformation of the suspension as a result of electrostatic forces generated between the movable part and the fixed part when the electrical control signal transitions from a minimum voltage value to a maximum voltage value; In a second direction opposite to the first direction, the elastic restoring force opposes the electrostatic force when the electrical control signal transitions from a maximum voltage value to a minimum voltage value as a result of the elastic restoring force caused by the suspension being elastically deformed.

[0015] During the transition from the maximum voltage value to the minimum voltage value, the value of the voltage of the electrical control signal decreases monotonically from the maximum voltage value to the minimum voltage value, during which a first average slope between the maximum voltage value and the first threshold voltage value; a second average slope between the first threshold voltage value and the second threshold voltage value, the second average slope being less in absolute value than the first average slope; and a third average slope between the second threshold voltage value and the minimum voltage value, the third average slope being greater in absolute value than the second average slope.

[0016] The movable portion moves in a second direction opposite to the first direction relative to the fixed portion as a result of an elastic restoring force generated by the elastically deformed suspension when the electrical control signal transitions from the first threshold voltage value to the second threshold voltage value.

[0017] Thus, the particular shape of the electrical control signal, and more precisely the presence of the second average slope, allows damping of the movement of the movable part relative to the fixed part when the movable part moves in the second direction, which has the effect of damping bouncing and / or residual vibrations of the movable part relative to the fixed part.

[0018] At the same time, the presence of the first average slope and the third average slope having an absolute value greater than the second average slope allows the time required for the electrical control signal to transition from a maximum voltage value to a minimum voltage value to be minimized, and therefore the frequency at which the drive device can be controlled remains high.

[0019] The proposed method therefore makes it possible to limit the phenomena of vibration and / or bouncing while allowing the control of the actuator at high frequencies.

[0020] The method may also have the following features:

[0021] In one possible embodiment of the method, during the transition from the minimum voltage value to the maximum voltage value, the voltage value of the electrical control signal increases monotonically from the minimum voltage value to the maximum voltage value, during which: a fourth average slope between the minimum voltage value and the second threshold voltage value; and a fifth average slope between the second threshold voltage value and the first threshold voltage value, the fifth average slope being less in absolute value than the fourth average slope; and a sixth average slope between the first threshold voltage value and the maximum voltage value, the sixth average slope being greater in absolute value than the fifth average slope.

[0022] When the electrical control signal transitions from the second threshold voltage value to the first threshold voltage value, the movable portion moves in a first direction relative to the fixed portion as a result of an electrostatic force created between the movable portion and the fixed portion.

[0023] In one possible embodiment of the method, the actuator also comprises a frame fixedly attached to the support, and the first threshold voltage value is selected such that, when the electrical control signal has a voltage value greater than the first threshold voltage value, an electrostatic force generated between the movable part and the fixed part is sufficient to hold the movable part against the frame, and, when the electrical control signal has a voltage value less than the first threshold voltage value, an electrostatic force generated between the movable part and the fixed part is insufficient to hold the movable part against the frame.

[0024] In one possible embodiment of the method, the second threshold voltage value is selected such that when the electrical control signal has a voltage value smaller than the second threshold voltage value, the electrostatic force generated between the movable part and the fixed part is insufficient to move the movable part relative to the fixed part, and when the electrical control signal has a voltage value larger than the second threshold voltage value, the electrostatic force generated between the movable part and the fixed part is sufficient to move the movable part relative to the fixed part.

[0025] In one possible embodiment of the method, the electrical control signal applied between the fixed part and the movable part is periodic so as to cause a movement of the movable part alternately in a first direction as a result of an electrostatic force and in a second direction as a result of an elastic return force, In one possible embodiment of the method, the second average slope is selected such that the electrical control signal transitions from the first threshold voltage value to the second threshold voltage value in a time substantially equal to one natural free oscillation period of the movable part relative to the fixed part.

[0026] In one possible embodiment of the method, the second average slope is selected such that the electrical control signal passes from the first threshold voltage value to the second threshold voltage value within a time period comprised in the range of 0.7 to 1.3 times one natural free vibration period of the movable part relative to the fixed part.

[0027] The invention also relates to an electrical control signal for controlling a micro-electromechanical system, the electrical control signal alternately assuming a maximum voltage value and a minimum voltage value, and during the transition from the maximum voltage value to the minimum voltage value, the value of the voltage of the electrical control signal monotonically decreases from the maximum voltage value to the minimum voltage value, during which: a first average slope between the maximum voltage value and the first threshold voltage value; a second average slope between the first threshold voltage value and the second threshold voltage value, the second average slope being less in absolute value than the first average slope; and a third average slope between the second threshold voltage value and the minimum voltage value, the third average slope being greater in absolute value than the second average slope.

[0028] The electrical control signal may also have the following characteristics:

[0029] In one possible embodiment of the electrical control signal, during the transition from the minimum voltage value to the maximum voltage value, the voltage value of the electrical control signal increases monotonically from the minimum voltage value to the maximum voltage value, during which: a fourth average slope between the minimum voltage value and the second threshold voltage value; and a fifth average slope between the second threshold voltage value and the first threshold voltage value, the fifth average slope being less in absolute value than the fourth average slope; and a sixth average slope between the first threshold voltage value and the maximum voltage value, the sixth average slope being greater in absolute value than the fifth average slope.

[0030] In one possible embodiment of the electrical control signal, the electrical control signal is periodic.

[0031] The invention also relates to a control circuit for controlling a micro-electromechanical system, the control circuit being configured to generate an electrical control signal as defined above.

[0032] The device may also have the following characteristics:

[0033] In one possible embodiment of the device, the device comprises: A microelectromechanical system comprising a support and an actuator, the actuator comprising a fixed part fixedly attached to the support, a movable part movably attached relative to the support, and a suspension connecting the movable part to the support; a control circuit as defined above, the control circuit being connectable to an actuator for applying an electrical control signal between the fixed part and the movable part, wherein as a result of an electrostatic force generated between the movable part and the fixed part when the electrical control signal transitions from a minimum voltage value to a maximum voltage value, the movable part moves in a first direction relative to the fixed part, the movement of the movable part relative to the fixed part causing elastic deformation of the suspension, and when the electrical control signal transitions from a first threshold voltage value to a second threshold voltage value, as a result of an elastic return force generated by the elastically deformed suspension opposing the electrostatic force, the movable part moves in a second direction opposite to the first direction relative to the fixed part.

[0034] In one possible embodiment of the device, the movable portion moves in a first direction relative to the fixed portion as a result of an electrostatic force generated between the movable portion and the fixed portion when the electrical control signal transitions from the second threshold voltage value to the first threshold voltage value.

[0035] In one possible embodiment of the device, the actuator also comprises a frame fixedly attached to the support, and the first threshold voltage value is selected such that, when the electrical control signal has a voltage value greater than the first threshold voltage value, the electrostatic force generated between the movable part and the fixed part is sufficient to hold the movable part against the frame, and such that, when the electrical control signal has a voltage value less than the first threshold voltage value, the electrostatic force generated between the movable part and the fixed part is insufficient to hold the movable part against the frame.

[0036] In one possible embodiment of the device, the second threshold voltage value is selected such that when the electrical control signal has a voltage value less than the second threshold voltage value, the electrostatic force generated between the movable part and the fixed part is insufficient to move the movable part relative to the fixed part, and when the electrical control signal has a voltage value greater than the second threshold voltage value, the electrostatic force generated between the movable part and the fixed part is sufficient to move the movable part relative to the fixed part.

[0037] In one possible embodiment of the device, the second average slope is selected such that the electrical control signal transitions from the first threshold voltage value to the second threshold voltage value in a time substantially equal to one natural free oscillation period of the movable part relative to the fixed part.

[0038] In one possible embodiment of the device, the second average slope is selected such that the electrical control signal transitions from the first threshold voltage value to the second threshold voltage value within a time period comprised in the range of 0.7 to 1.3 times one natural free oscillation period of the movable part relative to the fixed part.

[0039] In one possible embodiment of the device, the microelectromechanical system comprises a gear that can be driven in rotation by an actuator relative to a support about an axis of rotation.

[0040] Other characteristics and advantages will also become apparent from the following description, which is purely illustrative and not limiting and which must be read with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0041] [Figure 1] 1 is a side view diagram that illustrates a schematic representation of a microelectromechanical system according to one possible embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic top view of a microelectromechanical system. [Diagram 3]3 is a detailed view of the microelectromechanical system of FIG. 2 showing a drive module, a stopper, and a portion of a latch mechanism for positioning the stopper. [Figure 4] FIG. 3 is a detailed view of the microelectromechanical system of FIG. 2 showing a portion of the disengagement module. [Diagram 5] FIG. 3 is a detailed view of the microelectromechanical system of FIG. 2 showing a portion of the indexing module. [Figure 6] FIG. 3 is a detailed view of the micro-electro-mechanical system of FIG. 2 showing the drive teeth and the index teeth. [Figure 7] 11A-11D are diagrams illustrating the steps of initialization of the latch mechanism. [Figure 8] 11A-11D are diagrams illustrating the steps of initialization of the latch mechanism. [Figure 9] 11A-11D are diagrams illustrating the steps of initialization of the latch mechanism. [Figure 10] 11A-11D are diagrams illustrating the steps of initialization of the latch mechanism. [Figure 11] FIG. 13 is a schematic diagram of the drive module prior to initialization of the latch mechanism; [Figure 12] FIG. 13 illustrates a schematic diagram of the drive module after initialization of the latch mechanism. [Figure 13] FIG. 13A is a schematic diagram illustrating different force strengths acting on a drive tine when a movable drive portion moves in a first direction relative to a fixed drive portion for a first flexible beam width; [Figure 14] 11A-11C are schematic diagrams illustrating the strength of the elastic return force acting on the drive tooth when the movable drive part moves relative to the fixed drive part in a second direction opposite to the first direction relative to the first flexible beam width. [Figure 15] 11A-11C are schematic diagrams illustrating different force strengths acting on a drive tooth when a movable drive portion moves in a first direction relative to a fixed drive portion with a second flexible beam width. [Figure 16] 13A-13C are schematic diagrams illustrating the strength of the elastic return force acting on the drive tooth when the movable drive part moves relative to the fixed drive part in a second direction opposite to the first direction with respect to the second flexible beam width. [Figure 17] FIG. 13 is a detailed view of the shape of the intermeshing comb fingers. [Figure 18] FIG. 2 shows a schematic diagram of a first periodic movement of the drive teeth that enables the gear to be driven in a first rotational direction. [Figure 19] FIG. 13 shows a schematic representation of a second periodic movement of the drive teeth that allows the gear to be driven in a second rotational direction opposite to the first rotational direction. [Figure 20] FIG. 2 is a schematic diagram of a microelectromechanical system according to one possible embodiment of the invention before initialization of the latch mechanism. [Figure 21] FIG. 2 is a schematic diagram of a microelectromechanical system according to one possible embodiment of the invention after initialization of the latch mechanism. [Figure 22] FIG. 10 is a schematic diagram illustrating an electrical control signal for a drive module, an electrical control signal for an engagement module, and an electrical control signal for an index module, each having a square wave shape. [Diagram 23] FIG. 13 illustrates in greater detail the electrical control signals of the drive module, the engagement module, and the index module over a period of time. [Figure 24] 24A-24C are schematic diagrams illustrating the motion of the drive module, engagement module, and index module obtained when the actuators are controlled by the electrical control signals of FIGS. 22 and 23. [Diagram 25] FIG. 4 shows a schematic diagram of the movement of the drive module as a function of the value of the voltage of the drive module's electrical control signal; [Figure 26] FIG. 13 is a diagram illustrating the movement of an engagement module as a function of the value of the voltage of the electrical control signal of the engagement module. [Figure 27] FIG. 13 shows a schematic diagram of the movement of an indexing module as a function of the value of the voltage of the indexing module's electrical control signal; [Figure 28] 13A-13C are schematic diagrams illustrating electrical control signals for a drive module, an engagement module, and an index module, according to one possible embodiment of the present invention. [Figure 29]FIG. 15 shows a schematic representation of the movement of the drive module obtained when the actuator is controlled with the electrical control signals of FIG. 14. [Diagram 30] 15A-15C are schematic diagrams illustrating the movement of the engagement module obtained when the actuator is controlled with the electrical control signal of FIG. 14. [Diagram 31] 13A-13C are schematic diagrams illustrating electrical control signals of a drive module and an engagement module according to another possible embodiment of the present invention. [Diagram 32] FIG. 1 illustrates a schematic diagram of a control circuit for controlling a micro-electro-mechanical system. [Diagram 33] FIG. 33 shows diagrammatically an attenuation circuit forming part of the control circuit of FIG. 32; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] 1 to 6, the microelectromechanical system 10 shown is obtained by an etching method in a substrate 1 of semiconductor material, for example silicon.

[0043] The substrate 1 used is, for example, of the "silicon-on-insulator" (SOI) type. This substrate 1 comprises a thick lower layer of silicon (first layer 2), an intermediate layer of silicon oxide (second layer 3) and an upper layer of silicon (third layer 4) having a smaller thickness than the lower layer. The upper layer 4 of the substrate 1 has been etched to form a set of mechanical parts 5, while the lower layer 2 of the substrate 1 has not been etched and constitutes a support 6 for the mechanical parts 5. A part of the intermediate layer of silicon oxide 3 acts as a sacrificial layer and has been removed to allow the mobile mechanical part to be detached from the support 6, while another part of the sacrificial layer remains and allows the mechanical part to be attached to the support 6. Furthermore, the part of the sacrificial layer that remains acts as an electrical insulator between the mechanical parts 5 and the support 6 and thus between the different mechanical parts 5.

[0044] 1 to 6 comprises a support 6 and a mechanical part 5 having a micro-dimension. The mechanical part 5 is arranged above a surface of the support 6.

[0045] More precisely, in the example shown in Figures 1 to 6, the microelectromechanical system 10 comprises an actuator 11 and a wheel 12. The actuator 11 is formed in the upper layer 4 of the substrate 1. The wheel 12 may also be formed in the upper layer 4 of the substrate 1 or may be an insert formed independently.

[0046] The actuator 11 is configured to drive the wheel 12 to rotate relative to the support 6 about an axis of rotation.

[0047] The actuator 11 shown in FIGS. 2 to 4 includes a frame 100 and three element modules 200, 300 and 400. The frame 10 ...a.

[0048] The frame 100 is fixed relative to the support 6 .

[0049] The three basic modules include a drive module 200 , an engagement module 300 , and an indexing module 400 .

[0050] The wheel 12 is a gear wheel, i.e. it has a series of teeth on its circumference. Each tooth extends along a radial axis relative to the axis of rotation of the wheel. The gear wheel 12 may have a diameter comprised between 2,000 and 10,000 μm. The gear wheel 12 may, for example, have between 200 and 1,000 teeth.

[0051] The drive module 200 comprises a fixed drive portion 210 and a movable drive portion 220 .

[0052] The fixed drive part 210 is fixedly attached to the support 6. The fixed drive part 210 comprises a first carrier 214 and a plurality of fixed combs 211 extending vertically from the first carrier 214. Each fixed comb 211 comprises a shank 212 and a finger 213 extending vertically from the shank 212.

[0053] The movable drive portion 220 comprises a second carrier 224 and a plurality of movable combs 221 extending vertically from the second carrier 224. Each movable comb 221 comprises a shank 222 and a finger 223 extending vertically from the shank 222.

[0054] The actuator 11 also comprises a first suspension 230 connecting the movable drive part 220 to the frame 100. The first suspension 230 comprises two flexible beams 231 extending parallel to the shank 222 of the movable comb 221. The flexible beams 231 connect the second carrier 224 to the frame 100.

[0055] The movable combs 221 are arranged alternately between the fixed combs 211. That is, the movable combs 221 are arranged alternately with the fixed combs 211. Moreover, the movable combs 221 and the fixed combs 211 are arranged in pairs, each pair including a fixed comb 211 and an associated movable comb 221. More precisely, the fingers 213 of each fixed comb 211 of a pair extend with their free ends towards the fingers 223 of the associated movable comb 221 of the same pair. Similarly, the fingers 223 of the movable comb 221 of a pair extend with their free ends towards the fingers 213 of the fixed comb 211 of the same pair. Moreover, the fingers 213 of the fixed comb 211 and the fingers 223 of the movable comb 221 extend parallel to the tangential axis.

[0056] The axis perpendicular to the radius of the wheel 12 that passes through the location where the actuator 11 interacts with the wheel 12 is called the "tangential axis."

[0057] The drive module 200 also includes contact pads 215 formed on the fixed drive portion 210. The contact pads 215 are connectable to control circuitry for applying electrical control signals to the fixed drive portion 210. The contact pads 215 may be formed by depositing a metal layer on the fixed drive portion 210.

[0058] The actuator 11 also includes one or more contact pads 115 formed on the frame 100. The contact pads 115 may be connected to ground. The contact pads 115 may be formed by depositing one or more metal layers on the frame 100.

[0059] The actuator 11 also comprises a drive tooth 116 and a drive beam 117 that connects the drive tooth 116 to a movable drive portion 220 of the drive module 200 .

[0060] The drive teeth 116 are capable of engaging teeth 121 of the gear 12 to drive the gear 12 in rotation. The drive beam 117 extends along an axis tangential to the gear 12.

[0061] Applying a non-zero voltage between the fixed drive part 210 and the movable drive part 220 via the electrical contact pads 115, 215 creates an electrostatic force that attracts the movable combs 221 towards the fixed combs 211. More precisely, each of a set of movable combs 221 is attracted towards the same set of fixed combs 211. The electrostatic force created between the combs 211, 221 causes the movable drive part 220 to move in a first direction (arrow A) parallel to the tangential axis relative to the fixed drive part 210.

[0062] Movement of the movable drive part 220 in a first direction relative to the fixed drive part 210 causes elastic deformation of the first suspension 230. The elastic deformation of the suspension 230 involves bending of the flexible beam 231 connecting the movable drive part 220 to the frame 100. Due to this elastic deformation, the first suspension 230 exerts an elastic restoring force that tends to counter the electrostatic force. This elastic restoring force increases with the amplitude of the elastic deformation experienced by the first suspension 230.

[0063] When the tension on the fixed drive part 210 and the movable drive part 220 is reduced or eliminated, the electrostatic force becomes smaller than or equal to the elastic return force. The elastic return force exerted by the first suspension 230 causes the movable drive part 220 to move in a second direction (arrow B) opposite to the first direction parallel to the tangential axis relative to the fixed drive part 210. More precisely, each of the pair of movable combs 221 moves away from the fixed comb 211 of the same pair.

[0064] When the drive tooth 116 is connected to the movable drive portion 220 via the drive beam 117, the drive module 200 can cause the drive tooth 116 to move continuously parallel to the tangential axis in a first direction (arrow A) and then in a second direction (arrow B).

[0065] The engagement module 300 includes a fixed engagement portion 310 and a movable engagement portion 320 .

[0066] The fixed engagement part 310 is fixedly attached to the support 6. The fixed engagement part 310 comprises a third carrier 314 and a plurality of fixed combs 311 extending perpendicularly from the third carrier 314. Each fixed comb 311 comprises a shank 312 and a finger 313 extending perpendicularly from the shank 312.

[0067] The movable engagement portion 320 includes a fourth carrier 324 and a plurality of movable combs 321 extending vertically from the fourth carrier 324. Each movable comb 321 includes a shank 322 and a finger 323 extending vertically from the shank 322.

[0068] The fixed comb 311 and the movable comb 321 of the engagement module 300 are oriented perpendicular to the fixed comb 211 and the movable comb 221 of the engagement module 200 .

[0069] The actuator 11 also comprises a second suspension 330 connecting the movable engagement portion 320 to the frame 100. The second suspension 330 comprises two flexible beams 331 extending parallel to the shank 322 of the movable comb 321. The flexible beams 331 connect the fourth carrier 324 to the frame 100.

[0070] The movable combs 321 are arranged alternately between the fixed combs 311. Moreover, the movable combs 321 and the fixed combs 311 are arranged in pairs, each pair including a fixed comb 311 and an associated movable comb 321. More precisely, the fingers 313 of each fixed comb 311 of a pair extend with their free ends towards the fingers 323 of the associated movable comb 321. Similarly, the fingers 323 of the movable comb 321 extend with their free ends towards the fingers 313 of the fixed comb 311. Moreover, the fingers 313 of the fixed comb 311 and the fingers 323 of the movable comb 321 extend parallel to the radial axis.

[0071] The axis parallel to the radius of the wheel 12 that passes through the location where the actuator 11 interacts with the wheel 12 is referred to as the "radial axis."

[0072] The engagement module 300 also includes contact pads 315 formed on the fixed engagement portion 310. The contact pads 315 can be connected to a source of electrical potential for applying electrical control signals to the fixed engagement portion 310.

[0073] The actuator 11 also includes an engagement beam 118 that connects the drive tooth 116 to a moveable engagement portion 320 of the engagement module 300 .

[0074] The engagement beam 118 extends along a radial axis relative to the gear 12 .

[0075] When a non-zero voltage is applied between the fixed engagement portion 310 and the movable engagement portion 320 via the electrical contact pads 115, 315, an electrostatic force is generated that attracts the movable comb 321 towards the fixed comb 311. More precisely, each of a set of movable combs 321 is attracted towards the same set of fixed combs 311. The resulting electrostatic force causes the movable engagement portion 320 to move in a third direction (arrow C) parallel to the radial axis relative to the fixed engagement portion 310.

[0076] Movement of the movable engagement portion 320 relative to the fixed engagement portion 310 in the third direction causes elastic deformation of the second suspension 330. The elastic deformation of the suspension 330 involves bending of a flexible beam 331 connecting the movable engagement portion 320 to the frame 100. Due to this elastic deformation, the second suspension 330 exerts an elastic restoring force that tends to counter the electrostatic force. This elastic restoring force increases with the amplitude of the elastic deformation.

[0077] When the tension between the fixed engagement portion 310 and the movable engagement portion 320 is reduced or reduced to zero, the electrostatic force is less than the elastic return force or reduced to zero. The elastic return force generated by the second suspension 330 causes the movable engagement portion 320 to move relative to the fixed engagement portion 310 in a fourth direction (arrow D) opposite to the third direction parallel to the radial axis.

[0078] Thus, when the drive tooth 116 is connected to the movable engagement portion 320 via the engagement beam 118, the drive tooth 116 can be moved continuously in a third direction (arrow C) and a fourth direction (arrow D) parallel to the radial axis by the engagement module 300.

[0079] Each of the drive beam 117 and engagement beam 118 has sufficient flexibility to transfer the tangential motion generated by the drive module 200 and the radial motion generated by the engagement module 300, respectively, to the drive tooth 116, while allowing decoupling of these two motions. Thus, the two motions (tangential and radial) can be controlled independently of each other.

[0080] The indexing module 400 includes a fixed indexing portion 410 and a movable indexing portion 420 .

[0081] The fixed indexing portion 410 is fixedly mounted on the support. The fixed indexing portion 410 comprises a fifth carrier 414 and a plurality of fixed combs 411 extending perpendicularly from the fifth carrier 414. Each fixed comb 411 comprises a shank 412 and a finger 413 extending perpendicularly from the shank 412.

[0082] The movable indexing portion 420 includes a sixth carrier 424 and a plurality of movable combs 421 extending perpendicularly from the sixth carrier 424. Each movable comb 421 includes a shank 422 and fingers 423 extending perpendicularly from the shank 422.

[0083] The actuator 11 also comprises a third suspension 430 connecting the movable index portion 420 to the frame 100. The third suspension 430 comprises two flexible beams 431 extending parallel to the shanks 422 of the combs 421. The flexible beams 431 connect the transverse beams 424 to the frame 100.

[0084] The movable combs 421 are arranged alternately between the fixed combs 411. Moreover, the movable combs 421 and the fixed combs 411 are arranged in pairs, each pair including a fixed comb 411 and an associated movable comb 421. More precisely, the fingers 413 of each fixed comb 411 of a pair extend with their free ends towards the fingers 423 of the associated movable comb 421. Similarly, the fingers 423 of the movable comb 421 extend with their free ends towards the fingers 413 of the fixed comb 411. Moreover, the fingers 413 of the fixed comb 411 and the fingers 423 of the movable comb 421 extend parallel to the radial axis.

[0085] The actuator 11 also comprises an indexing tooth 120. In the example shown in Figure 3, the indexing tooth 120 comprises two protrusions 126 and a recess 127 provided between the two protrusions 126. When the indexing tooth 120 engages with a tooth 121 of the gear 12, the recess 127 receives the tooth 121 of the gear 12 within the recess 127, which has the effect of preventing the wheel 12 from rotating.

[0086] The actuator 11 also includes an index beam 128 that connects the index tooth 120 to a moveable index portion 420 of the index module 400 .

[0087] The indexing beam 128 extends along a radial axis relative to the gear 12 .

[0088] Application of a non-zero voltage between the fixed index portion 410 and the movable index portion 420 via electrical contact pads 415 and 115 creates an electrostatic force that attracts the movable comb 421 towards the fixed comb 411. More precisely, each of a set of movable combs 421 is attracted towards the same set of fixed combs 411. The resulting electrostatic force causes the movable index portion 420 to move in a third direction (arrow C) parallel to the radial axis relative to the fixed index portion 410.

[0089] Movement of the movable index portion 420 relative to the fixed index portion 410 in a third direction causes an elastic deformation of the third suspension 430. The elastic deformation of the suspension 430 involves bending of a flexible beam 431 connecting the movable index portion 420 to the frame 100. This elastic deformation causes the third suspension 430 to exert an elastic restoring force that tends to counter the electrostatic force. This elastic restoring force increases with the amplitude of the elastic deformation.

[0090] When the tension between the fixed index portion 410 and the movable index portion 420 is reduced or eliminated, the electrostatic force becomes less than or equal to the elastic return force. As a result of the elastic return force generated by the third suspension, the movable index portion 420 moves away from the fixed index portion 410 in a fourth direction (arrow D) opposite the third direction parallel to the radial axis.

[0091] When the index tooth 120 is connected to the movable index portion 420 via the index beam 128, the index tooth 120 is thus moved continuously in the third and fourth directions by the index module, parallel to the radial axis.

[0092] It is therefore possible to move the indexing teeth 120 alternately in a radial direction relative to the wheel 12 .

[0093] By appropriately controlling the drive module 200 and the engagement module 300 with phase-shifted periodic electrical control signals, it is possible to move the drive tooth 116 with a hysteretic first periodic motion (movement shown in FIG. 18) or a hysteretic second periodic motion (movement shown in FIG. 19) that is inverted relative to the hysteretic first periodic motion.

[0094] As the drive teeth 116 move in a first periodic motion within the hysteresis, the drive teeth 116 mesh with successive teeth 121 of the gear 12, driving the gear 12 in a stepped rotational motion in a first rotational direction.

[0095] As the teeth move in a second periodic motion within the hysteresis, the drive teeth 116 mesh with successive teeth 121 of the gear 12, driving the gear 12 in a stepped rotational motion in a second rotational direction opposite the first rotational direction.

[0096] In parallel, the indexing module 400 is controlled by an electrical control signal that is opposite in phase to the electrical control signal applied to the engagement module 300 .

[0097] Thus, when the drive teeth 116 are disengaged from the teeth 121 of the wheel 12, the index teeth 120 are engaged with the teeth 121 of the wheel 12. Conversely, when the drive teeth 116 are engaged with the teeth 121 of the wheel 12, the index teeth 120 are disengaged from the teeth 121 of the wheel 12.

[0098] The indexing teeth 120 therefore prevent premature rotation of the wheel 12 while the drive teeth 116 are disengaged from the teeth 121 of the wheel 12 (during the disengagement phase), while the indexing teeth 120 do not form an obstacle to the rotation of the wheel 121 caused by the drive teeth 116 (during the drive phase).

[0099] The actuator 11 also comprises a stopper 240 making it possible to limit the movement of the movable drive part 220 of the drive module 200 in a second direction (arrow B).

[0100] The actuator 11 also includes a latch mechanism 500 for positioning the abutment 240 against the support at a predetermined position.

[0101] In FIG. 3, the abutment 240 and the latch mechanism 500 are shown as they are obtained immediately after manufacturing of the micro-electro-mechanical system 10, ie, prior to latching of the latch mechanism 500 and prior to operating the micro-electro-mechanical system.

[0102] In this view, the latch mechanism 500 is in an unlatched configuration.

[0103] Furthermore, as can be seen from this figure, in this configuration the fingers 223 of the movable comb 221 of the drive module 200 are not engaged between the fingers 213 of the fixed comb 211 of the drive module 200 .

[0104] The latch mechanism 500 comprises a tappet 510 and a resilient leg 511 extending along a tangential axis from the tappet 510. In the example shown in FIG.

[0105] Each resilient leg 511 has a free end with a first snap-locking lug 512 disposed at the free end.

[0106] The latch mechanism 500 also comprises a flexible beam 520 that connects the tappet 510 to the frame 100. In the example shown in Figure 2, the latch mechanism 500 comprises two flexible beams 520. The flexible beams 520 extend parallel to each other along a radial axis.

[0107] The stopper 240 is fixed to the tappet 510. In other words, the stopper 240 is fixed relative to the tappet 510. More precisely, in the example shown in Figure 3, the stopper 240 and the tappet 510 are formed in a single, unique piece of material.

[0108] Furthermore, the frame 100 comprises second snap-lock lugs 112. In the example shown in FIG.

[0109] 7-10 show schematic steps for latching the latch mechanism 500, allowing the latch mechanism 500 to move from an unlatched configuration (as shown in FIG. 7) to a latched configuration (as shown in FIG. 10).

[0110] As shown in FIG. 7, a non-zero voltage is applied between the fixed drive portion 210 and the movable drive portion 220 of the drive module 200 via the electrical contact pads 115, 215.

[0111] The applied voltage creates an electrostatic force that has the effect of moving the movable drive portion 220 of the drive module 200 relative to the fixed drive portion 210 in a first direction (arrow A) parallel to the tangential axis.

[0112] As shown in FIG. 8, during its movement the movable drive part 220 pushes against the tappet 510, which has the effect of moving the tappet 510 and also the stopper 240 in a first direction (arrow A).

[0113] This also has the effect of pressing the first snap-lock lug 512 against the second snap-lock lug 112 .

[0114] Due to their shape, the first snap-lock lug 512 slides over the second snap-lock lug 112 by causing bending of the resilient legs 511. In the example shown in Figure 8, the resilient legs 511 bend towards each other.

[0115] As shown in FIG. 9, bending of the resilient legs 511 causes the first snap-lock lug 512 to be pushed past the second snap-lock lug 112 .

[0116] When the first snap-lock lug 512 passes over the second snap-lock lug 112, the resilient legs 511 tend to return to their original shape. In the example shown in Figure 9, the resilient legs 511 are separated from each other. The separation of the resilient legs 511 has the effect of engaging the first snap-lock lug 512 with the second snap-lock lug 112.

[0117] 10, the voltage applied between the fixed drive part 210 and the movable drive part 220 of the drive module 200 is then removed. The electrostatic force disappears.

[0118] As a result of the elastic return force exerted by the first suspension 230, the movable driving part 220 of the drive module 200 moves relative to the fixed driving part 210 of the drive module 200 in a second direction (arrow B) parallel to the tangential axis. The movable driving part 220 of the drive module 200 moves in the second direction relative to the fixed driving part 210 until the movable driving part 220 of the drive module 200 abuts against a stopper 240.

[0119] However, the stopper 240 is retained by the first snap-lock lug 512 and the second snap-lock lug 112, preventing the tappet 510 from returning to its initial position.

[0120] When the latch mechanism 500 is in the latched configuration, the stopper 240 is positioned to prevent movement of the first movable drive part 220 in the second direction to a rest position where the stopper 240 prevents the elastic force generated by the first suspension from being zero.

[0121] In other words, the stopper 240 is positioned to hold the first suspension 230 in a permanently elastically deformed state. The position of the stopper 240 determines the minimum value of the elastic return force exerted by the first suspension 230.

[0122] Due to the presence of the stopper 240, the elastic restoring force exerted by the first suspension 230 cannot be made smaller than this minimum value.

[0123] FIG. 11 shows a schematic of the drive module 200 prior to latching by the latch mechanism 500.

[0124] As shown in this figure, the fingers 223 of the movable comb 221 are not engaged between the fingers 213 of the fixed comb 211 .

[0125] Furthermore, the first suspension 230 is in a rest position, i.e. the flexible beam 231 of the first suspension 230 is not deformed, and therefore the elastic restoring force exerted by the first suspension 230 is zero.

[0126] FIG. 12 shows a schematic of the drive module 200 after the latch mechanism 500 has been latched.

[0127] As shown in this figure, the fingers 223 of the movable comb 221 are partially engaged in the spaces provided between the fingers 213 of the fixed comb 211 .

[0128] The stopper 240 prevents the movable drive part 220 from returning to its rest position, so that the flexible beam 231 is held in an elastically deformed state. Therefore, the elastic restoring force exerted by the first suspension 230 is not zero.

[0129] FIG. 13 is a schematic diagram illustrating different force strengths acting on the drive tooth 116 when the movable drive part 220 moves in a first direction (in the direction of arrow A) relative to the fixed drive part 210.

[0130] The forces acting on the drive tooth 116 are an electrostatic force due to a voltage applied between the fixed part 210 and the movable drive part 220 and an elastic restoring force due to the deformation of the first suspension 230 .

[0131] The elastic restoring force opposes the electrostatic force, so the strength of the driving force acting on the drive tooth 116 is the difference between the strength of the electrostatic force and the strength of the elastic restoring force.

[0132] The grey area of ​​the diagram in FIG. 13 illustrates the drive force exerted on the drive tooth 116 for a first stiffness value of the first suspension 230 (beam width: 33 μm) in a first rotational direction (direction of arrow A).

[0133] As can be seen from this figure, the strength of the electrostatic force remains relatively constant during movement of the movable drive part 220 relative to the fixed drive part 210.

[0134] On the other hand, the magnitude of the elastic restoring force increases as the movable driving part 220 moves in the first direction.

[0135] The increase in the strength of the elastic restoring force depends on the stiffness of the first suspension 230. By way of comparison, this figure shows the variation in strength of the elastic restoring force for a first stiffness value of the first suspension 230 (beam width=33 μm) and the variation in strength of the elastic restoring force for a second stiffness value of the first suspension 230 (beam width=15 μm).

[0136] Moreover, if the movement of the movable drive part 220 is zero, the strength of the elastic return force is not zero. Indeed, in this position, the first suspension 230 is deformed due to the presence of the stopper 240.

[0137] FIG. 14 is a diagram illustrating the strength of the elastic return force acting on the drive tooth 116 when the movable drive part 220 moves relative to the fixed drive part 210 in a second direction (in the direction of arrow B) opposite to the first direction.

[0138] As can be seen from this figure, no electrostatic forces act on the moving parts.

[0139] The movable drive part 220 moves in the second direction relative to the fixed drive part 210 solely due to the elastic return force.

[0140] The magnitude of the elastic restoring force decreases as the movable drive part 220 moves in the second direction. However, due to the presence of the stopper 240, the strength of the elastic restoring force does not become zero. The strength of the elastic restoring force remains greater than a non-zero minimum value.

[0141] As shown in this figure, the decrease in the strength of the elastic restoring force depends on the stiffness of the first suspension 230. Thus, this figure shows the variation in the strength of the elastic restoring force for a first stiffness value of the first suspension (beam width=33 μm).

[0142] The grey area of ​​the diagram in FIG. 14 illustrates the drive force exerted on the drive tooth 116 for a first stiffness value of the first suspension 230 (beam width: 33 μm) in the second rotational direction (direction of arrow B).

[0143] FIG. 15 is a schematic diagram illustrating different force strengths acting on the drive tooth 116 when the movable drive part 220 moves in a first direction relative to the fixed drive part 210.

[0144] The forces acting on the drive tooth 116 are an electrostatic force caused by tension between the fixed drive part 210 and the movable drive part 220, and an elastic return force due to deformation of the first suspension 230. The elastic return force opposes the electrostatic force.

[0145] This figure shows the change in strength of the elastic restoring force relative to the second stiffness value of the first suspension 230 (beam width=15 μm).

[0146] The grey area in the diagram of Fig. 15 shows the variation in the strength of the drive force exerted on the drive tooth 116 in the first direction (direction of arrow A) for a second stiffness value (beam width: 15 μm) of the first suspension 230. This second stiffness value, which is smaller than the first stiffness value, results in a larger grey zone (compare the areas of the grey areas in Fig. 13 and Fig. 15) and therefore also a larger strength of the drive force in the first direction.

[0147] FIG. 16 is a schematic diagram illustrating the strength of the elastic return force acting on the drive tooth 116 when the movable drive part 220 moves relative to the fixed drive part 210 in a second direction opposite to the first direction for a second stiffness value of the first suspension 230.

[0148] As can be seen from this figure, no electrostatic forces act on the movable drive part 220.

[0149] The movable drive part 220 moves in the second direction relative to the fixed part 210 solely due to the elastic return force.

[0150] The magnitude of the elastic return force decreases as the movable drive portion 220 moves in the second direction.

[0151] However, the strength of the elastic restoring force does not become zero due to the presence of the stopper 240. The strength of the elastic restoring force remains greater than a non-zero minimum value.

[0152] This figure shows the change in strength of the elastic restoring force relative to the second stiffness value of the first suspension 240 (beam width=15 μm).

[0153] The grey area of ​​the diagram in Figure 16 shows the driving force exerted on the drive tooth 116 for a second stiffness value (beam width: 15 μm) of the first suspension 230 in the second rotational direction (direction of arrow B). As a comparison, the driving force in the second direction for the first stiffness value is also displayed in the same diagram.

[0154] 13 to 16 show that as the stiffness of the first suspension increases, the driving force that serves to drive the gear 12 in the first rotational direction decreases rapidly.

[0155] Thus, depending on the intended application, the stiffness of the first suspension 230 may be adjusted to promote better effectiveness of rotational driving of the gear 12 in a first rotational direction or better effectiveness of rotational driving of the gear 12 in a second rotational direction.

[0156] FIG. 17 is a detailed view of the shape of the fingers 213 of the fixed comb 211 and the shape of the fingers 223 of the movable comb 221 of the drive module 200.

[0157] The etching techniques used to etch microelectromechanical systems during production require a minimum spacing between the fixed and moving parts of each microsystem.

[0158] For example, in microelectromechanical systems such as those shown in Figures 1-6, a minimum spacing must be provided between the fingers of the fixed and movable combs.

[0159] The minimum interval Gu depends on the etching depth. For example, in the case of etching performed by deep reactive ion etching (DRIE) to a depth of 200 μm, the minimum interval Gu can be about 4 to 6 μm.

[0160] Prior to latching of the latch mechanism 500, the fingers 223 of the movable comb 221 are not engaged with the fingers 213 of the fixed comb 211. The fingers 223 of the movable comb 221 are spaced apart from the nearest fingers 213 of the fixed comb 211 by a first spacing G1.

[0161] The spacing G1 between the fingers 213 of the fixed comb 211 and the fingers 223 of the movable comb 221 is greater than the minimum spacing Gu. The "spacing" between two fingers is defined as the shortest distance separating the two fingers.

[0162] After the latch mechanism 500 is latched, the fingers 223 of the movable comb 221 are engaged between the fingers 213 of the fixed comb 211 .

[0163] Thus, the fingers 223 of the movable comb 221 are spaced apart from the nearest fingers 213 of the fixed comb 211 by a second spacing G2 and a third spacing G3, which are smaller than the first spacing G1. More precisely, the fingers 223 of the movable comb 221 are spaced apart from the fingers 213 of the fixed comb 211 located on one side of the fingers 223 of the movable comb 221 by a second spacing G2 and from the other fingers 213 of the fixed comb 211 located on the other side of the fingers 223 of the movable comb 221 by a third spacing G3. The spacings G2 and G3 between the fingers 213 and 223 of the fixed comb 211 and the fingers 223 of the movable comb 221 may be less than the minimum spacing Gu. The spacing G2 and / or the spacing G3 may be comprised between 0.1 and 5 μm, preferably between 1 and 3 μm. For example, the spacing G2 may be equal to 3 μm and the spacing G3 may be equal to 4 μm.

[0164] In particular, the ratio of the thickness of the fingers 213, 223 (i.e. the etching depth of the upper layer of silicon) to the spacing between the fingers 213 of the fixed comb 211 and the fingers 223 of the movable comb 221 can be comprised between 50 and 400, preferably between 70 and 150.

[0165] Because the electrostatic force generated by the drive module 200 is inversely proportional to the spacing between the fingers 213 of the fixed comb 211 and the fingers 223 of the movable comb 221, this has the effect of increasing the drive force generated by the drive module 200 while eliminating the spacing constraints imposed by the etching technique used.

[0166] The second spacing G2 may be different from the third spacing G3 to take into account the fact that during movement of the movable drive part 220 relative to the fixed drive part 210, the movement of the fingers 223 of the movable comb 221 is neither perfectly linear nor perfectly parallel to the fingers 213 of the fixed comb 211.

[0167] 20 and 21 show diagrammatically a microelectromechanical system 10 according to another possible embodiment of the invention.

[0168] This alternative embodiment differs from the embodiment shown in Figures 1 to 6 in that the drive module 200 is symmetrical about an axis of symmetry parallel to the tangential axis.

[0169] As with the embodiment of FIGS. 1-6, the drive module 200 includes a fixed drive portion 210 and a movable drive portion 220 .

[0170] The fixed drive part 210 is fixedly attached to the support 6 .

[0171] In this embodiment, the fixed drive portion 210 comprises two first carriers 214, with a first series of fixed combs 211 extending vertically from one of the first carriers 214 and a second series of fixed combs 211 extending vertically from the other of the first carriers 214.

[0172] The movable drive portion 220 comprises a second carrier 224 and a plurality of movable combs 221 extending perpendicularly from the second carrier 224 .

[0173] In this embodiment, the movable combs 221 include a first set of movable combs extending from a first side of the second carrier 224 and a second set of movable combs extending from a second side of the second carrier 224 opposite the first side. Thus, the movable combs 221 extend symmetrically on both sides of the second carrier 224.

[0174] Similarly, the fixed combs 211 of the first series of fixed combs extend from a first side of the second carrier 224, and the fixed combs 211 of the second series of fixed combs extend from a second side of the second carrier 224 opposite the first side. Thus, the fixed combs 211 extend symmetrically on both sides of the second carrier 224.

[0175] The actuator 11 also comprises a first suspension 230 connecting the movable drive part 220 to the frame 100. The first suspension 230 comprises four flexible beams 231 extending parallel to the shank 222 of the movable comb 221. The flexible beams 231 connect the second carrier 224 to the frame 100. The four flexible beams 231 include two flexible beams extending from a first side of the second carrier 224 and two other flexible beams extending from a second side of the second carrier 224. The first suspension 230 is therefore symmetrical with respect to an axis of symmetry parallel to the tangential axis.

[0176] The movable combs 221 are alternately arranged between the fixed combs 211. That is, the movable combs 221 are alternately located with the fixed combs 211. Moreover, the movable combs 221 and the fixed combs 211 are arranged in pairs, each pair including a fixed comb 211 and an associated movable comb 221. More precisely, the fingers 213 of each fixed comb 211 of a pair extend with their free ends towards the fingers 223 of the associated movable comb 221 of the same pair. Similarly, the fingers 223 of the movable comb 221 of a pair extend with their free ends towards the fingers 213 of the fixed comb 211 of the same pair. Moreover, the fingers 213 of the fixed comb 211 and the fingers 223 of the fixed comb 221 extend parallel to the tangential axis.

[0177] FIG. 20 shows a schematic of the drive module 200 prior to latching by the latch mechanism 500.

[0178] As shown in this figure, the fingers 223 of the movable comb 221 are not engaged between the fingers 213 of the fixed comb 211 .

[0179] Furthermore, the first suspension 230 is in a rest position, i.e. the flexible beam 231 of the first suspension 230 is not deformed, and therefore the elastic restoring force exerted by the first suspension 230 is zero.

[0180] FIG. 21 shows a schematic of the drive module 200 after the latch mechanism 500 has been latched.

[0181] As shown in this figure, the fingers 223 of the movable comb 221 are partially engaged in the spaces provided between the fingers 213 of the fixed comb 211 .

[0182] The stopper 240 prevents the movable drive part 220 from returning to its rest position, so that the flexible beam 231 is held in an elastically deformed state. Therefore, the elastic restoring force exerted by the first suspension 230 is not zero.

[0183] One advantage of this embodiment is that due to the symmetrical configuration of the first suspension 230, while the movable drive part 220 moves relative to the fixed drive part 210, the movement of the fingers 223 of the movable comb 221 is completely linear and parallel to the fingers 213 of the fixed comb 211.

[0184] In other words, the second carrier 224 is constrained to move along a tangential axis and cannot move along a radial axis.

[0185] Therefore, the spacing G2, G3 between the fingers 213, 223 of the fixed comb 211 and the movable comb 221 can be further reduced. Also, the second spacing G2 and the third spacing G3 can be equal. The spacings G2 and G3 (shown in FIG. 17) can be less than 1 μm.

[0186] This allows the electrostatic force generated by the drive module 200 to be greater.

[0187] FIG. 22 illustrates generally example electrical control signals for a drive module, example electrical control signals for an engagement module, and example electrical control signals for an index module.

[0188] In Fig. 22, each electrical control signal is a voltage electrical control signal. Thus, the diagram of Fig. 22 shows the variation in voltage of each electrical control signal as a function of time. Each electrical control signal is periodic and has a substantially square wave shape.

[0189] For example, the electrical control signal of the drive module alternates between a minimum voltage value (eg, Vmin=0) and a maximum voltage value (eg, Vmax=110 volts).

[0190] The diagram of FIG. 23 shows more precisely the variation in voltage of each electrical control signal as a function of time during one period.

[0191] FIG. 24 illustrates generally the movement of the movable drive portion 220 of the drive module 200 over time, the movement of the movable engagement portion 320 of the engagement module 300 over time, and the movement of the movable portion 420 of the indexing module 400 over time.

[0192] These movements were obtained when the actuator 11 was controlled with electrical control signals identical to those shown in FIGS.

[0193] 24 shows that the movable drive part 220 of the drive module 200 bounces. These bounces essentially occur when the movable drive part 220 reaches the end of its stroke. More precisely, these bounces are visible when the movable drive part 220 contacts the stopper 240 during the elemental movement in the second direction (arrow B), i.e. when the movable drive part 220 returns to its initial position as a result of the elastic return force caused by the elastically deformed first suspension 230.

[0194] FIG. 24 also illustrates that the movable engagement portion 320 of the engagement module 300 and the movable index portion 420 of the index module 400 are also subject to residual vibrations.

[0195] These bounces or these residual vibrations are detrimental to the proper operation of the actuator 11 .

[0196] On the one hand, it is necessary to wait for these bounces or these vibrations to be sufficiently damped before commanding a reverse movement of the moving part, which limits the frequency at which the actuator can be controlled.

[0197] On the other hand, bouncing can create repeated impacts between mechanical parts, causing premature wear of the contacting surfaces and shortening the life of the microelectromechanical system.

[0198] FIG. 25 is a diagram illustrating generally the movement of the movable drive part 220 of the drive module 200 as a function of the value of the voltage of the electrical control signal applied between the movable drive part 220 and the fixed drive part 210. As shown in FIG.

[0199] This figure more particularly shows the amplitude of movement of the movable drive part 220 relative to the fixed drive part 210 as the value of the voltage of the electrical control signal applied to the drive module 200 increases progressively linearly over time.

[0200] 25, when the value of the voltage of the electrical control signal is below the threshold voltage value Vdebut, the movable driving part 220 does not move relative to the fixed driving part 210. In fact, the electrostatic force generated between the movable driving part 220 and the fixed driving part 210 is insufficient to overcome the elastic return force generated by the first suspension 230 and is therefore insufficient to move the movable driving part 220 relative to the fixed driving part 210. In other words, the first suspension 230 is subjected to an elastic prestress which the electrostatic force must overcome to be able to move the movable driving part 220 relative to the fixed driving part 210.

[0201] When the value of the voltage of the electrical control signal is comprised between the threshold voltage value Vdebut and the threshold voltage value Vfin, the movable drive part 220 moves relative to the fixed drive part 210. Indeed, the electrostatic force generated between the movable drive part 220 and the fixed drive part 210 causes a movement of the movable drive part 220 relative to the fixed drive part 210. The amplitude of the movement of the movable drive part 220 relative to the fixed drive part 210 increases continuously depending on the value of the voltage of the electrical control signal.

[0202] If the value of the voltage of the control signal is greater than the voltage Vfin, the movable drive part 220 will not move relative to the fixed drive part 210. In fact, the movable drive part abuts against the frame 100. Therefore, the increase in the electrostatic force will not cause further movement of the movable drive part 220 relative to the fixed drive part 210.

[0203] FIG. 26 is a diagram illustrating generally the movement of the movable engagement portion 320 of the engagement module 300 as a function of the value of the voltage of the electrical control signal applied to the engagement module 300. As shown in FIG.

[0204] For the drive module 200, a threshold voltage value Vdebut can be determined at which the electrostatic force generated between the movable engagement portion 320 and the fixed engagement portion 310 is insufficient to move the movable engagement portion 320 relative to the fixed engagement portion 310.

[0205] For the engagement module 300, when the value of the voltage of the electrical control signal is less than the threshold voltage value Vdebut, the movable engagement portion 320 does not move relative to the fixed engagement portion 310. In fact, since the fingers 323 of the movable comb 321 are not engaged with the fingers 313 of the fixed comb 311, the electrostatic force generated between the fixed comb 311 and the movable comb 321 is very small.

[0206] It is also possible to determine the threshold voltage value Vfin at which the movable engagement portion 320 abuts the frame 100.

[0207] When the voltage of the control signal is comprised between the threshold voltage value Vdebut and the threshold voltage value Vfin, the movable engagement portion 320 moves relative to the fixed engagement portion 310. The amplitude of the movement of the movable engagement portion 320 relative to the fixed engagement portion 310 increases continuously depending on the value of the voltage of the electrical control signal.

[0208] FIG. 27 is a schematic diagram illustrating the movement of the movable index portion 420 of the index module 400 as a function of the value of the voltage of the electrical control signal applied to the index module 400.

[0209] With respect to the engagement module 300, it is possible to determine a threshold voltage value Vdebut below which the electrostatic force generated between the movable index portion 420 and the fixed index portion 410 is insufficient to cause movement of the movable index portion 420 relative to the fixed index portion 410.

[0210] It is also possible to determine the threshold voltage value Vfin at which the movable index portion 420 abuts the frame 100.

[0211] When the voltage of the control signal is comprised between the threshold voltage value Vdebut and the threshold voltage value Vfin, the movable index portion 420 moves relative to the fixed index portion 410. The amplitude of the movement of the movable index portion 420 relative to the fixed index portion 410 increases continuously with the value of the voltage of the electrical control signal.

[0212] FIG. 28 is a schematic diagram illustrating electrical control signals for the drive module 200, the engagement module 300, and the indexing module 400, according to one possible embodiment of the present invention.

[0213] As shown in this figure, the electrical control signal of the drive module 200 alternates between a minimum voltage value (eg, Vmin=0) and a maximum voltage value (eg, Vmax=110 volts).

[0214] During the transition from the maximum voltage value Vmax to the minimum voltage value Vmin, the voltage value of the electrical control signal decreases monotonically from the maximum voltage value Vmax to the minimum voltage value Vmin.

[0215] In addition, during this decrease, the electrical control signal a first average gradient between the maximum voltage value Vmax and the threshold voltage value Vfin defined for the drive module (in this example, Vfin≈0.83×Vmax); a second average gradient between the threshold voltage value Vfin and the threshold voltage value Vdebut that is smaller in absolute value than the first average gradient (in this example, Vdebut ≈ 0.41 × Vmax); and a third average gradient between the threshold voltage value Vdebut and the minimum voltage value Vmin defined for the drive module, the third average gradient having an absolute value greater than the second average gradient (in this example, Vmin=0).

[0216] The first average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tmax, Tfin] that the value of the electrical control signal transitions from a value Vmax to a value Vfin. In other words, the first average slope is equal to (Vfin-Vmax) / (Tfin-Tmax), where (Tfin-Tmax) is the time it takes for the electrical control signal to transition from a value Vmax to a value Vfin.

[0217] The second average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tfin, Tdebut] that the value of the electrical control signal transitions from the value Vfin to the value Vdebut. In other words, the second average slope is equal to (Vdebut-Vfin) / (Tdebut-Tfin), where (Tdebut-Tfin) is the time it takes for the electrical control signal to transition from the value Vfin to the value Vdebut.

[0218] The third average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tdebut, Tmin] that the value of the electrical control signal transitions from the value Vdebut to the value Vmin. In other words, the third average slope is equal to (Vmin-Vdebut) / (Tmin-Tdebut), where (Tmin-Tdebut) is the time it takes for the electrical control signal to transition from the value Vdebut to the value Vmin.

[0219] 28, the electrical control signal is linear over each of the periods [Tmax, Tfin], [Tfin, Tdebut], and [Tdebut, Tmin]. In this case, the first average slope is equal to the instantaneous slope of the signal that is constant over the period [Tmax, Tfin], the second average slope is equal to the instantaneous slope of the signal that is constant over the period [Tfin, Tdebut], and the third average slope is equal to the instantaneous slope of the signal that is constant over the period [Tdebut, Tmin].

[0220] However, other forms of electrical control signal are of course possible, for example forms in which the electrical control signal is not linear over each period.

[0221] In FIG. 28, several possible values ​​of the second average slope are shown.

[0222] As shown in FIG. 28, the electrical control signals of the engagement module 300 and the indexing module 400 have configurations similar to those of the electrical control signals of the drive module 200 .

[0223] As shown in this figure, the electrical control signals of the engagement module 300 (respectively, the indexing module 400) alternate between a minimum voltage value (eg, Vmin=0) and a maximum voltage value (eg, Vmax=110 volts).

[0224] During the transition from the maximum voltage value to the minimum voltage value, the voltage value of the electrical control signal decreases monotonically from the maximum voltage value Vmax to the minimum voltage value Vmin.

[0225] In addition, during this decrease, the electrical control signal a first average gradient between the maximum voltage value and the threshold voltage value Vfin defined for the engagement module 300 (respectively the indexing module 400) (in this example, Vfin≈0.91×Vmax); a second average gradient between the threshold voltage value Vfin and the threshold voltage value Vdebut that is smaller in absolute value than the first average gradient (in this example, Vdebut ≈ 0.27 × Vmax); and a third average gradient between the threshold voltage value Vdebut defined for the engagement module 300 (respectively the indexing module 400) and a minimum voltage value Vmin (in this example Vmin=0) that is greater in absolute value than the second average gradient.

[0226] In FIG. 28, several possible values ​​of the second average slope are shown.

[0227] FIG. 29 is a diagram illustrating diagrammatically the amplitude of movement of the movable drive part 220 relative to the fixed drive part 210 over time obtained when the drive module 200 is controlled by the electrical control signals of FIG.

[0228] Depending on the second average slope selected for the electrical control signal applied to the drive module 200 (i.e., depending on the time it takes for the control signal to transition from the voltage value Vfin to the voltage value Vdebut), the bouncing of the moving part 220 is damped more or less.

[0229] It is possible to determine the optimum value of the second average slope (or the optimum value of the time it takes for the control signal to pass from the voltage value Vfin to the voltage value Vdebut), i.e. the value of the second average slope that makes it possible to obtain the best damping of these bounces.

[0230] In the example shown in Fig. 29, the time it takes for the control signal to transition from the voltage value Vfin to the voltage value Vdebut is 0.42 ms, which allows for the best damping of the bounce. This time is substantially equal to one natural free vibration period of the movable drive part 220 relative to the fixed drive part 210. For example, this time is in the range of 0.7 to 1.3 times the natural free vibration period of the movable drive part 220 relative to the fixed drive part 210.

[0231] Similarly, FIG. 30 is a diagram illustrating, over time, the amplitude of movement of the movable engagement portion 320 of the engagement module 300 relative to the fixed engagement portion 310 obtained when the engagement module 300 is controlled with the electrical control signal of FIG.

[0232] In this example, the time it takes for the control signal to transition from the voltage value Vfin to the voltage value Vdebut is 0.56 ms, which allows for the best damping of the vibrations, and is substantially equal to one natural free vibration period of the movable engagement part 320 relative to the fixed engagement part 310.

[0233] FIG. 31 is a schematic diagram illustrating electrical control signals for a drive module and an engagement module, according to another possible embodiment of the present invention.

[0234] In this embodiment, similar to the previous embodiment, the control signal alternates between a minimum voltage value Vmin and a maximum voltage value Vmax.

[0235] However, in this embodiment, during the transition from the minimum voltage value to the maximum voltage value, the voltage value of the electrical control signal increases monotonically from the minimum voltage value to the maximum voltage value.

[0236] In addition, the voltage value of the electrical control signal is a fourth average gradient between the minimum voltage value Vmin and the threshold voltage value Vdebut; a fifth average gradient between the threshold voltage value Vdebut and the threshold voltage value Vfin, the fifth average gradient having an absolute value smaller than that of the fourth average gradient; and a sixth average gradient between the threshold voltage value Vfin and the maximum voltage value Vmax, the sixth average gradient having an absolute value greater than the fifth average gradient.

[0237] The fourth average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tmin, Tdebut] that the value of the electrical control signal transitions from the value Vmin to the value Vdebut. In other words, the fourth average slope is equal to (Vdebut-Vmin) / (Tdebut-Tmin), where (Tdebut-Tmin) is the time it takes for the electrical control signal to transition from the value Vmin to the value Vdebut.

[0238] The fifth average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tdebut, Tfin] that the value of the electrical control signal transitions from the value Vdebut to the value Vfin. In other words, the fifth average slope is equal to (Vfin-Vdebut) / (Tfin-Tdebut), where (Tfin-Tdebut) is the time it takes for the electrical control signal to transition from the value Vdebut to the value Vfin.

[0239] The sixth average slope is defined as the average of the instantaneous slopes of the electrical control signal over the time period [Tfin, Tmax] that the value of the electrical control signal transitions from a value Vfin to a value Vmax. In other words, the sixth average slope is equal to (Vmax-Vfin) / (Tmax-Tfin), where (Tmax-Tfin) is the time it takes for the electrical control signal to transition from a value Vfin to a value Vmax.

[0240] In the example shown in Figure 31, the electrical control signal is linear over each period [Tmin, Tdebut], [Tdebut, Tfin], and [Tfin, Tmax]. In this case, the fourth average slope is equal to the instantaneous slope of the signal that is constant over the period [Tmin, Tdebut], the fifth average slope is equal to the instantaneous slope of the signal that is constant over the period [Tdebut, Tfin], and the sixth average slope is equal to the instantaneous slope of the signal that is constant over the period [Tfin, Tmax].

[0241] However, other forms of electrical control signal are of course possible, for example forms in which the electrical control signal is not linear over each period.

[0242] FIG. 32 illustrates diagrammatically a control circuit 13 suitable for controlling the actuator 11 of the micro-electro-mechanical system 10.

[0243] In this example, the control circuit 13 An attenuation circuit 131; a power supply circuit 132 including a charge pump converter and a voltage regulator, the power supply circuit 132 being configured to generate a high voltage power supply signal; a commutation circuit 133 including a high voltage switch configured to selectively connect the actuator 11 to the power supply circuit 132 output and the damping circuit 131; a start-up circuit 134 configured to control the damping circuit; A voltage level shift circuit 135; and a low voltage digital microprocessor 136.

[0244] The damping circuit 131, the power supply circuit 132, the commutation circuit 133, the starting circuit 134 and the voltage level shifting circuit 135 may be components of the same ASIC circuit.

[0245] Digital processor 136 (also called a "low-voltage digital core") is a low-voltage programmable digital processor configured to control different circuits of the ASIC circuit.

[0246] The power supply circuit 132 is configured to generate a high voltage power supply signal, for example, with a maximum voltage of 125 volts, possibly regulated between two values ​​less than the maximum voltage, and characterized by a variable rise time of less than 1 ms depending on the operating frequency of the charge pump.

[0247] A charge pump is an analog circuit including a capacitor that makes it possible to amplify the voltage of the electrical control signal applied to the input of the commutation circuit 133 (the charge pump is also called a "voltage multiplier"). This analog circuit makes it possible to go from an input voltage of, for example, 1.5 to 3 volts of a conventional battery (button cell) to an output voltage of more than 100 volts, which is necessary to supply the modules 200, 300 and 400 of the actuator 11.

[0248] The switches of the commutation circuit 133 are configured to allow commutation between the high voltage terminal (110 volts) required for the voltage boost of the electrical control signal applied to the actuator 11 and the damping circuit 131. These switches comprise, for example, one or more MOSFET power transistors capable of withstanding high voltages.

[0249] The start-up circuit 134 (also referred to as “VDD bootstrap”) is configured to control the MOSFET transistors of the attenuation circuit 131. The start-up circuit 134 is an analog circuit that allows the low-voltage digital control signals generated by the digital processor 136 to be adapted, converted and injected into the gates of the MOSFET transistors of the attenuation circuit 131.

[0250] The voltage level shifter circuit 135 (also referred to as a “high voltage level shifter”) is an analog circuit configured to convert the low voltage digital control signals generated by the digital processor 136 into high voltage control signals that are applied to the gates of the MOSFET transistors of the commutation circuit 133.

[0251] FIG. 33 shows diagrammatically an attenuation circuit 131 which forms part of the control circuit 13 of FIG.

[0252] In this figure, the actuator 11 is assimilated to a capacitor. In fact, the drive module 200, the engagement module 300, and the index module each comprise a moving part and a fixed part. The moving part and the fixed part can be assimilated to the plates of a capacitor.

[0253] 33, only the drive module 200 is shown. However, the schematic of the damping circuit 131 is identical for all three modules.

[0254] The attenuation circuit 131 comprises a diode D1, a resistor R1 and a MOSFET transistor Q1, which are electrically connected in a parallel assembly between the commutation circuit 133 and ground.

[0255] The MOSFET transistor Q1 is controlled by a start-up circuit 134. The start-up circuit 134 is connected to the gate of the transistor and configured to control the transistor to selectively block the transistor or to activate the transistor.

[0256] When MOSFET transistor Q1 is turned off, no current flows through the transistor (drain-to-source).

[0257] When the MOSFET transistor Q1 is activated, current is allowed to pass through the transistor.

[0258] The operation of the control circuit 13 is as follows.

[0259] MOSFET transistor Q1 is initially cut off.

[0260] When the voltage of the high-voltage power supply signal transitions from a minimum voltage value (Vmin) to a maximum voltage value (Vmax), the commutation module 133 is in a first configuration in which the commutation module 133 connects the actuator 11 to the output of the power supply circuit 132. Thus, the actuator 11 is supplied by the high-voltage power supply signal generated by the power supply circuit 132.

[0261] When the voltage of the high-voltage power supply signal transitions from a maximum voltage value (Vmax) to a minimum voltage value (Vmin), the commutation circuit 133 transitions to a second configuration in which the commutation module 133 connects the actuator 11 to the damping circuit 131 .

[0262] Thus, when the commutation circuit 133 is in the second configuration, the drive module 200 discharges through the damping circuit 131 .

[0263] The discharging of the drive module 200 occurs in three successive phases.

[0264] Initially, the voltage between the fixed driving part 210 and the movable driving part 220 is equal to a maximum voltage value Vmax. During the discharge of the driving module 200, the voltage between the fixed driving part 210 and the movable driving part 220 decreases.

[0265] As long as the voltage between the fixed drive part 210 and the movable drive part 220 is greater than the threshold voltage value Vfin (first phase), the discharge current of the actuator 11 passes through the diode D1. The voltage at the terminals of the drive module 200 drops sharply from the maximum voltage value Vmax to the threshold voltage value Vfin. The variation of the voltage at the terminals of the drive module 200 from the maximum voltage value Vmax to the threshold voltage value Vfin has a first gradient. In this example, the first average gradient is quasi-vertical. In other words, the first average gradient is less than -1 V / μs. The time it takes for the electrical control signal to move from the maximum voltage value Vmax to the threshold voltage value Vfin (Tfin-Tmax) is less than 50 μs, or even less than 10 μs.

[0266] When the voltage between the fixed drive part 210 and the movable drive part 220 falls below the threshold voltage value Vfin (second phase), the diode D1 does not pass. The discharge current of the actuator 11 passes through the resistor R1. The voltage between the fixed drive part 210 and the movable drive part 220 drops from the threshold voltage value Vfin to the threshold voltage value Vdebut. The variation of the voltage at the terminals of the drive module 200 has a second average slope that depends on the value of the resistor R1. The second average slope has a smaller absolute value than the first average slope. In other words, the voltage between the fixed drive part 210 and the movable drive part 220 drops more slowly than in the first phase. The resistor R1 serves to damp the movement of the movable drive part 220 relative to the fixed drive part 210.

[0267] When the voltage between the fixed driving part 210 and the movable driving part 220 falls below the threshold voltage value Vdebut (third phase), the MOSFET transistor Q1 is activated. This causes the discharge current of the actuator 11 to pass through the MOSFET transistor Q1. The voltage at the terminals of the driving module 200 drops sharply from the threshold voltage value Vdebut to a minimum voltage value Vmin. The variation of the voltage at the terminals of the driving module 200 has a third average slope. In this example, the third slope is quasi-vertical. In other words, the third average slope is less than -1 V / μs. The time it takes for the electrical control signal to move from the maximum voltage value Vdebut to the threshold voltage value Vmin (Tmin-Tdebut) is less than 50 μs, or even less than 10 μs. The third slope has an absolute value greater than the second slope.

[0268] In practice, the starting circuit 134 controls the MOSFET transistor Q1 such that during the first phase and during the second phase the transistor is blocked and during the third phase the MOSFET transistor Q1 is activated. For this purpose, the starting circuit 134 generates an electrical control signal having a period suitable for alternately blocking and activating the MOSFET transistor Q1 in synchronization with the high voltage power supply signal generated by the power supply circuit 132. The synchronization of the two signals is obtained in that the power supply circuit 132 and the starting circuit 134 are controlled by a digital processor 136.

Claims

1. A method for controlling a microelectromechanical system (10) comprising a support (6) and an actuator (11), comprising the steps of: The actuator (11) a fixed part (210, 310, 410) fixedly attached to said support (6); a movable part (220, 320, 420) movably attached to said support (6); a suspension (230, 330, 430) connecting said movable part (220, 320, 420) to said support (6), The method comprises: applying an electrical control signal between said fixed part (210, 310, 410) and said movable part (220, 320, 420), said electrical control signal alternating between a maximum voltage value (Vmax) and a minimum voltage value (Vmin); as a result of an electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) when the electrical control signal transitions from the minimum voltage value (Vmin) to the maximum voltage value (Vmax), the movable part (220, 320, 420) moves in a first direction relative to the fixed part (210, 310, 410), the movement of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410) causing an elastic deformation of the suspension (230, 330, 430); During the transition from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), the value of the voltage of the electrical control signal monotonically decreases from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), during which: a first average slope between the maximum voltage value (Vmax) and a first threshold voltage value (Vfin); a second average slope between the first threshold voltage value (Vfin) and the second threshold voltage value (Vdebut), the second average slope being smaller in absolute value than the first average slope; a third average gradient between the second threshold voltage value (Vdebut) and the minimum voltage value (Vmin), the third average gradient being greater in absolute value than the second average gradient; in succession, When the electrical control signal transitions from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut), an elastic restoring force generated by the elastically deformed suspension (230, 330, 430) opposes the electrostatic force, causing the movable part (220, 320, 420) to move in a second direction opposite to the first direction relative to the fixed part (210, 310, 410). method.

2. During the transition from the minimum voltage value (Vmin) to the maximum voltage value (Vmax), the voltage value of the electrical control signal increases monotonically from the minimum voltage value (Vmin) to the maximum voltage value (Vmax), during which: a fourth average slope between the minimum voltage value (Vmin) and the second threshold voltage value (Vdebut); a fifth average slope between the second threshold voltage value (Vdebut) and the first threshold voltage value (Vfin), the fifth average slope being smaller in absolute value than the fourth average slope; a sixth average gradient between the first threshold voltage value (Vfin) and the maximum voltage value (Vmax), the sixth average gradient being greater in absolute value than the fifth average gradient; Consecutively as a result of the electrostatic force generated between the movable portion (220, 320, 420) and the fixed portion (210, 310, 410) when the electrical control signal transitions from the second threshold voltage value (Vdebut) to the first threshold voltage value (Vfin), the movable portion (220, 320, 420) moves in the first direction relative to the fixed portion (210, 310, 410). The method of claim 1.

3. The actuator (11) also comprises a frame (100) fixedly attached to the support (6), The first threshold voltage value (Vfin) is when the electrical control signal assumes a voltage value greater than the first threshold voltage value (Vfin), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is selected to be sufficient to hold the movable part (220, 320, 420) against the frame (100), selected such that, when the electrical control signal assumes a voltage value less than the first threshold voltage value (Vfin), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is insufficient to hold the movable part (220, 320, 420) against the frame (100), The method of claim 1.

4. The second threshold voltage value (Vdebut) is when the electrical control signal assumes a voltage value less than the second threshold voltage value (Vdebut), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is selected to be insufficient to move the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); When the electrical control signal assumes a voltage value greater than the second threshold voltage value (Vdebut), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is selected to be sufficient to move the movable part (220, 320, 420) relative to the fixed part (210, 310, 410). The method of claim 1.

5. the electrical control signal applied between the fixed part (210, 310, 410) and the movable part (220, 320, 420) is periodic so as to cause the movable part (220, 320, 420) to move alternately in a first direction as a result of the electrostatic force and in a second direction as a result of the elastic return force; The method of claim 1.

6. the second average slope is selected such that the electrical control signal transitions from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut) in a time substantially equal to one natural period of free oscillation of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); The method of claim 1.

7. the second average slope is selected such that the electrical control signal transitions from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut) within a time period comprised between 0.7 and 1.3 times one natural period of free vibration of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); The method of claim 1.

8. 1. An electrical control signal for controlling a micro-electro-mechanical system, the electrical control signal alternating between a maximum voltage value (Vmax) and a minimum voltage value (Vmin), and during a transition from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), a value of a voltage of the electrical control signal monotonically decreases from the maximum voltage value (Vmax) to the minimum voltage value (Vmin), during which: a first average slope between the maximum voltage value (Vmax) and a first threshold voltage value (Vfin); a second average slope between the first threshold voltage value (Vfin) and the second threshold voltage value (Vdebut), the second average slope being smaller in absolute value than the first average slope; a third average slope between the second threshold voltage value (Vdebut) and the minimum voltage value (Vmin) that is greater in absolute value than the second average slope; Electrical control signals.

9. During the transition from the minimum voltage value (Vmin) to the maximum voltage value (Vmax), the voltage value of the electrical control signal increases monotonically from the minimum voltage value (Vmin) to the maximum voltage value (Vmax), during which a fourth average slope between the minimum voltage value (Vmin) and the second threshold voltage value (Vdebut); a fifth average slope between the second threshold voltage value (Vdebut) and the first threshold voltage value (Vfin), the fifth average slope being smaller in absolute value than the fourth average slope; a sixth average gradient between the first threshold voltage value (Vfin) and the maximum voltage value (Vmax) that is greater in absolute value than the fifth average gradient; 9. The electrical control signal of claim 8.

10. The electrical control signal of claim 8 , wherein the electrical control signal is periodic.

11. A control circuit (13) for controlling a micro-electromechanical system, the control circuit (13) being configured to generate an electrical control signal according to any one of claims 8 to 10.

12. A device, comprising: A microelectromechanical system (10) comprising a support (6) and an actuator (11), the actuator (11) comprising a fixed part (210, 310, 410) fixedly attached to the support (6), a movable part (220, 320, 420) movably attached with respect to the support (6), and a suspension (230, 330, 430) connecting the movable part (220, 320, 420) to the support (6); 12. A control circuit (13) according to claim 11, comprising: a control circuit (13) connectable to the actuator (11) for applying an electrical control signal between the fixed part (210, 310, 410) and the movable part (220, 320, 420), wherein the movable part (220, 320, 420) moves relative to the fixed part (210, 310, 410) as a result of an electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) when the electrical control signal passes from the minimum voltage value (Vmin) to the maximum voltage value (Vmax). a first direction, the movement of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410) causing elastic deformation of the suspension (230, 330, 430), and when the electrical control signal transitions from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut), an elastic restoring force generated by the elastically deformed suspension (230, 330, 430) opposes the electrostatic force, resulting in the movable part (220, 320, 420) moving in a second direction opposite to the first direction relative to the fixed part (210, 310, 410); device.

13. as a result of the electrostatic force generated between the movable portion (220, 320, 420) and the fixed portion (210, 310, 410) when the electrical control signal transitions from the second threshold voltage value (Vdebut) to the first threshold voltage value (Vfin), the movable portion (220, 320, 420) moves in the first direction relative to the fixed portion (210, 310, 410). The device of claim 12.

14. The actuator (11) also comprises a frame (100) fixedly attached to the support (6), The first threshold voltage value (Vfin) is when the control signal assumes a voltage value greater than the first threshold voltage value (Vfin), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is selected to be sufficient to hold the movable part (220, 320, 420) against the frame (100); selected such that when the control signal assumes a voltage value less than the first threshold voltage value (Vfin), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is insufficient to hold the movable part (220, 320, 420) against the frame (100); The device of claim 12.

15. The second threshold voltage value (Vdebut) is when the electrical control signal assumes a voltage value less than the second threshold voltage value (Vdebut), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is selected to be insufficient to move the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); selected such that, when the electrical control signal assumes a voltage value greater than the second threshold voltage value (Vdebut), the electrostatic force generated between the movable part (220, 320, 420) and the fixed part (210, 310, 410) is sufficient to move the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); The device of claim 12.

16. The second average slope is the electrical control signal is selected to transition from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut) within a time period substantially equal to one natural period of free vibration of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); The device of claim 12.

17. The second average slope is the electrical control signal is selected to transition from the first threshold voltage value (Vfin) to the second threshold voltage value (Vdebut) within a time period comprised within a range of 0.7 to 1.3 times one natural period of free vibration of the movable part (220, 320, 420) relative to the fixed part (210, 310, 410); The device of claim 12.

18. 13. The device according to claim 12, wherein the microelectromechanical system (10) comprises a gear (12) that can be driven in rotation by the actuator (11) relative to the support (6) about an axis of rotation.

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