Accelerometer Comprising a Mass and an Acceleration Sensitive Device Associated with the Mass - Patent application

Abstract

The present invention relates to an accelerometer comprising a support (2), a seismic mass (1) associated with an acceleration sensor having at least one acceleration sensitivity axis (A), the seismic mass (1) being subject to forces resulting from the acceleration to be measured and static forces (such as gravity or inertial forces), and an elastically deformable connecting device (3) connecting the seismic mass (1) to the support (2). The accelerometer also comprises a fixed stop system (5), a movable stop device (34) attached to or forming part of the elastically deformable connecting device (3), and a movement system (4) configured to move the movable stop device (34) relative to the fixed stop system (5) to elastically deform the elastically deformable connecting device (3) in order to apply a restoring force (FR) to the seismic mass (1).

Description

[Technical Field]

[0001] The present invention relates generally to accelerometers. More particularly, the present invention relates to miniaturized accelerometers that are sensitive to gravity or more generally to any static force. More particularly, the present invention is useful for microelectromechanical systems (MEMS) type accelerometers. [Background technology]

[0002] A MEMS-based accelerometer generally comprises a mass, called a seismic or inertial mass, associated with at least one acceleration-sensing element (acceleration sensor).

[0003] Gravity acting on the seismic mass causes an offset in the acceleration signal measured by the acceleration sensor, and if this offset is not compensated for, the acceleration sensor must have a wide measurement range. Furthermore, if an accelerometer uses multiple acceleration sensors to eliminate noise through differential measurement, the effect of gravity on the measurement signal will reduce the effectiveness of noise suppression.

[0004] In order to compensate for the effect of gravity on the mass and consequently on the measurements made by the acceleration sensor, it is known to mount the seismic mass 1 on a spring 3 connected to a support 2, as shown in Figure 1. The spring is arranged to exert a restoring force on the mass in order to compensate for the gravitational force experienced by the seismic mass.

[0005] This type of solution is described, for example, in patent FR2735580, where gravity compensation uses pre-stressed springs. The spring load (tensile or compressive) is obtained by depositing a layer of material on the spring. Such solutions cannot be dynamically changed to adapt to the orientation of the accelerometer. The accelerometer may be oriented perpendicular to or opposite to the direction of gravity, or horizontally.

[0006] Patent EP 0 886 146 proposes an accelerometer with a mechanical system for adjusting the compression of the spring connecting the mass to the support depending on the intended use of the accelerometer. However, once the adjustment of the spring is determined, the compensation obtained is fixed.

[0007] The gravity force acting on the mass can also be compensated for by applying a compressive force to the beam connecting the seismic mass to the support, causing the beam to deflect, as described in application WO 2015 / 185222. However, because this solution requires deflecting beams, the direction of gravity compensation is predetermined by the beam's deflection direction, resulting in only two states being allowed for each beam: no deflection and a compressed state corresponding to the beam's deflection in a predetermined direction. Therefore, if it is necessary to be able to compensate for the gravity force acting on the mass in one direction or the other depending on the sensor orientation, it is necessary to provide an assembly of two different beams with opposite deflection directions. Furthermore, in the solution of application WO 2015 / 185222, a deflected state of the beam requires the application of a large compressive force, since the direction of the compressive force is along the beam's rigid axis.

[0008] In addition to these mechanical compensation solutions, developments have led to the use of dynamic compensation by constant adjustment of external compensation forces of the electrostatic or magnetic type.

[0009] Patent US11401160 describes a voltage pulse that applies an electrostatic force to a seismic mass to compensate for the effects of gravity. However, such a method requires a closed-loop system and properly filtered voltages to maintain low noise levels, resulting in a significant increase in energy consumption.

[0010] The present invention aims to propose a new accelerometer that makes it possible to alleviate some or all of the problems mentioned above. In a particular aspect, the invention aims to improve the performance, and in particular the accuracy of the acceleration measured by the accelerometer. Summary of the Invention

[0011] To this end, the present invention is directed to an accelerometer comprising: ·Support; a seismic mass associated with an acceleration sensor having at least one acceleration sensitivity axis, the seismic mass being subject to forces induced by the acceleration to be measured and static forces such as gravitational or inertial forces; and · elastically deformable connecting devices, such as springs, connecting the seismic mass to its supports; The accelerometer is further characterized in that it includes: · a fixed stop system and a movable stop device fixed to or forming part of the elastically deformable connecting device; A movement system configured to move the movable stop device relative to the fixed stop system in a manner that elastically deforms the elastically deformable connecting device to apply a restoring force to the seismic mass.

[0012] Such an accelerometer architecture makes it possible to compensate for static forces, in particular the effects of gravity, that are experienced by the seismic mass with limited energy expenditure. Indeed, the invention makes it possible to apply a restoring force to the seismic mass that is adjustable by discrete values. The restoring force is adjusted by controlling the movement of the movable stop device relative to the fixed stop system, so that a predetermined value of force of movement towards the stop of the fixed stop system can be applied to the movable stop device. This predetermined value is greater than a predetermined minimum value necessary to reach the stop of the fixed stop system in order to bring the movable stop device into contact with said stop and maintain contact with said stop. There is no need to adjust the movement force applied to the movable stop device in order to hold it in its position relative to the fixed stop.

[0013] This solution can be used effectively for any orientation between the accelerometer's axis of sensitivity and the direction of a static force such as gravity, because the movable stop device can be pulled in one direction or the other or left stationary. The fixed stop system and moving system also allow multiple movable stop devices to move in different directions.

[0014] In known prior art solutions in which electrostatic compensation can be used to cancel offsets in the measurement signal due to gravity, it is often necessary to perform closed-loop adjustment of the applied electrostatic force, which increases energy consumption.The solution according to the invention, thanks to a system of mechanical stops formed by cooperation between a movable stop device and a fixed stop system, makes it possible to use electrostatic forces to compensate for the effects of static forces on the seismic mass without the drawback of high energy consumption.

[0015] In one embodiment of the present invention, the movement system comprises an electrode system that generates electrostatic forces to move the movable stop device relative to the fixed stop device in various configurations, thereby loading the elastically deformable connecting device in various configurations and resulting in various values ​​and directions of forces on the seismic mass, so that the resulting restoring force can be adjusted depending on the static forces to be compensated for that are experienced by the seismic mass.

[0016] The present invention makes it possible to enjoy the advantages of compensating for the effects of static forces experienced by a seismic mass by applying an electrostatic force to the connection device between the seismic mass and the support, since the electrostatic force is adjustable and reversible with limited signal noise and without the drawbacks of the high electrical energy consumption that adjustment of this electrostatic force requires.

[0017] The accelerometer may also have one or more of the following features, in any technically possible combination:

[0018] In one embodiment, the movable stop device is conductive and the movement system comprises an electrode system comprising at least one electrode, preferably at least two electrodes, and a control unit configured to apply a voltage to said at least one electrode to exert an electrostatic force on the movable stop device and move it until it contacts the fixed stop system.

[0019] In one embodiment, the control unit is configured to control the electrode system to apply a predetermined voltage to the at least one electrode to generate an electrostatic force on the movable stop device that is greater than the minimum force required to hold the movable stop device in contact with the fixed stop system.

[0020] In one embodiment, the electrode system includes first and second electrodes on opposite sides of the elastically deformable connecting device, the fixed stop system includes two stoppers on opposite sides of the elastically deformable connecting device, and a predetermined voltage value to the first electrode causes the movable stop device to move until it contacts the first stopper of the fixed stop system, and a predetermined voltage value to the second electrode causes the movable stop device of the elastically deformable connecting device to move until it contacts the second stopper of the fixed stop system.

[0021] In one embodiment, the accelerometer comprises a control unit, and the combination of the elastically deformable connection device, the movable stop device, the moving system and the fixed stop system forms a connection assembly, and the accelerometer comprises a plurality of connection assemblies, and movement of the movable stop device of a connection device contacting the stop system of one connection assembly is controllable by the control unit independently of movement of the movable stop device of another connection assembly.

[0022] In one embodiment, the control unit is configured to control the connection assembly in a manner that applies a restoring force to the seismic mass via the elastically deformable connection device, the restoring force being different from a restoring force applied to the seismic mass by another connection assembly.

[0023] In one embodiment, the elastically deformable connection device of at least one connection assembly has at least one physical characteristic, such as length and / or stiffness, that differs from a corresponding physical characteristic of an elastically deformable connection device of another connection assembly of the accelerometer.

[0024] In one embodiment, the accelerometer is a microelectromechanical system.

[0025] In one embodiment, the fixed stop system is shared in whole or in part with the electrode system.

[0026] In one embodiment, the fixed stop system is integrally formed with the support.

[0027] In one embodiment, the elastically deformable connecting device is integrally formed with the support.

[0028] In one embodiment, the accelerometer comprises a control unit for controlling the movement system, the control unit being configured to enable selective control of the position of the movable stop device from a set of discrete positions, preferably for each connection assembly in the case where the accelerometer comprises multiple connection assemblies.

[0029] In one embodiment, the set of discrete positions of the movable stop device includes the following positions: a rest position of the elastically deformable connecting device corresponding to the absence of control of the movement of the movable stop device by the control unit; a first tension position in which the movable stop device contacts the fixed stop system and the elastically deformable connecting device is under elastic tension, exerting a first restoring force on the seismic mass; and Preferably, a second tension position in which the movable stop device contacts the fixed stop system and the elastically deformable connecting device is under elastic tension and applies a second restoring force to the seismic mass, the second restoring force being different from the first restoring force.

[0030] Also proposed is a method for at least partially compensating for static forces, such as gravity, experienced by the seismic mass of any of the aforementioned accelerometer embodiments, the method comprising moving the movable stop device relative to the fixed stop system such that the elastically deformable connection device is under elastic tension and exerts a restoring force on the seismic mass that at least partially compensates for said static forces experienced by the seismic mass. [Brief explanation of the drawings]

[0031] Other characteristics and advantages of the present invention will become more apparent from the following description, which is given purely by way of example and is not limiting of the invention, and which is to be read with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of one embodiment of an accelerometer known from the prior art. [Figure 2] FIG. 2 is a schematic diagram of an accelerometer according to an embodiment of the present invention in a configuration that compensates for the gravitational forces experienced by a seismic mass with the aid of an electrode system that generates an electrostatic force that moves a movable stop relative to a fixed stop. [Figure 2A] FIG. 2A is a theoretical schematic diagram illustrating various possible positions of an elastically deformable connecting device, in particular three possible positions of a movable stop device between stop elements of a fixed stop system of an accelerometer according to one embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram of the accelerometer of FIG. 2 without an electrostatic force applied to the elastically deformable connecting device. [Figure 3A] FIG. 3A is a schematic diagram of the accelerometer of FIG. 2 in an operational mode in which an electrostatic force is applied to each upper resiliently deformable connection device in one direction and an electrostatic force is applied to each lower resiliently deformable connection device in an opposite direction. [Figure 3B] FIG. 3B is a schematic diagram of the accelerometer of FIG. 2 in an operational mode in which a co-directional electrostatic force is applied to each elastically deformable connecting device in a direction that compensates for the gravitational force experienced by the seismic mass. [Figure 4]FIG. 4 is a schematic diagram of an accelerometer according to another embodiment of the invention, comprising a plurality of, e.g., four, elastically deformable connection devices connecting the seismic mass to a support on one side of the seismic mass, and a plurality of, e.g., four, other elastically deformable connection devices connecting the seismic mass to a support on the other side of the seismic mass. [Figure 4A] 4A is a schematic diagram of the accelerometer of FIG. 4 in an operating mode in which, on each side of the seismic mass, electrostatic forces in the same direction are applied to some of the elastically deformable connecting devices in a direction that compensates for the gravitational force experienced by the seismic mass, and electrostatic forces are applied to other elastically deformable connecting devices in the same direction as the gravitational force experienced by the seismic mass (taking into account the gravitational force projected onto the sensitivity axis of the sensor). [Figure 5] FIG. 5 is a schematic diagram of an accelerometer according to another embodiment of the invention, comprising a plurality of, e.g., four, elastically deformable connection devices connecting the seismic mass to a support on one side of the seismic mass and a plurality of, e.g., four other elastically deformable connection devices connecting the seismic mass to a support on the other side of the seismic mass, some of the elastically deformable connection devices on each side having a different length than other elastically deformable connection devices located on the same side of the seismic mass. [Figure 6] FIG. 6 is a schematic diagram of an accelerometer according to another embodiment of the present invention, in which an elastically deformable connecting device comprises a lever mechanism that allows a movable stop device to move relative to a fixed stop system. [Figure 7] FIG. 7 is a partial view of an accelerometer according to one embodiment of the present invention, without showing the electrode system and fixed stop system with which the movable stop device is adapted to cooperate. [Figure 7A] FIG. 7A is a detailed view of area VII of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0032] The inventive concepts are described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, sizes and relative sizes of elements may be exaggerated for clarity. Like numbers refer to like elements in all drawings. However, the inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments disclosed herein. Rather, these embodiments are proposed so that this description will be thorough and complete, and will convey the scope of the inventive concepts to those skilled in the art.

[0033] References throughout this specification to "one embodiment" mean that the functionality, structure, or particular feature described with reference to one embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" in various places throughout the specification do not necessarily refer to the same embodiment. Furthermore, the functionality, structure, or particular features may be combined in any suitable manner in one or more embodiments.

[0034] Referring to the drawings, an accelerometer is shown that includes a support 2 and a seismic mass 1. The seismic mass 1 comprises a mass with an associated acceleration sensor (not shown), i.e., a device that is sensitive to acceleration in a given direction. The acceleration sensor therefore allows measurement of the acceleration it experiences along its sensitivity axis. The sensitivity axis of the sensor is denoted As. In various embodiments of the invention, the acceleration sensitive device may or may not be fixed to the mass. The acceleration sensitive device may not have a mechanical connection to the mass. For example, in the case of optical, capacitive or tunneling measurements, acceleration can be measured without physical contact with the moving mass.

[0035] The seismic mass 1 may be subjected to acceleration-induced forces that are measured with the aid of acceleration-sensitive devices.

[0036] The seismic mass 1 is connected to the support 2 by an elastically deformable connecting device 3, such as a spring. In certain embodiments, the elastically deformable property is reflected in the fact that the connecting device 3 can flex and / or stretch when subjected to a load.

[0037] The connecting device 3 can be made of various materials, for example the same material as the support 2. In certain embodiments, the connecting device 3 has an elongated shape.

[0038] In the embodiments of the invention described below, the seismic mass 1 is connected to the support 2 by a number of elastically deformable connecting devices 3. The description of one elastically deformable connecting device 3 also applies to the other elastically deformable connecting devices 3, if present, unless specific property differences between the elastically deformable connecting devices 3 are indicated.

[0039] The support 2 is a reference structure that is fixed to or forms all or part of the housing or chassis of the accelerometer.

[0040] The seismic mass 1, and therefore the acceleration sensor, is also sensitive to static forces, in particular gravity Fg, which may be a constant inertial force, such as a constant centrifugal force.

[0041] In one preferred embodiment of the present invention, the accelerometer is a micro-electromechanical system (MEMS).

[0042] The acceleration sensitive device is configured to measure acceleration and may use a variety of technologies, such as capacitive, piezoelectric, piezoresistive, optical, tunneling, or other techniques.

[0043] In the remainder of the following description, the static force considered is gravity Fg, the effect of which on the seismic mass 1 must be compensated for, but the invention and the following description also apply to situations where the static force is a force other than gravity, such as a constant inertial force. If the sensitivity axis As of the accelerometer is vertical, the accelerometer is subjected to gravity. If the accelerometer is positioned so that the sensitivity axis As is tilted, the accelerometer is subjected to a force corresponding to the projection of gravity onto the axis As.

[0044] The elastically deformable connecting device 3 comprises a movable stop device 34 which is fixed to or forms part of the elastically deformable connecting device 3. The movable stop device 34 can thus be located between the part 32 of the elastically deformable connecting device 3 connected to the support 2 and the part 31 of the elastically deformable connecting device 3 connected to the mass 1.

[0045] The movable stop device 34 is movable by the movement system 4 so as to contact the fixed stop system 5 in such a manner as to deform the elastically deformable connection device 3 to counteract the force Fg exerted on the seismic mass 1 by gravity.

[0046] The movement system 4 allows the movable stop device 34 to move into contact with the fixed stop system 5 and to maintain this contact in order to maintain said position as long as the movement is controlled by the control unit 100, as will be explained below.

[0047] The stop system 5 is fixed relative to the support 2 to which the elastically deformable connecting device 3 is connected. The stop system 5 may be made of the same material as the support 2 or may be made integral with the support 2. In one embodiment of the present invention, the support 2, the connecting device 3 and the stop system 5 may be manufactured by etching a silicon block.

[0048] It is preferable that the elastically deformable connecting device 3 is movable laterally relative to the longitudinal direction of the elastically deformable connecting device 3 when the elastically deformable connecting device 3 is in an undeformed state and in the absence of gravity.

[0049] The accelerometer comprises a moving system 4 configured such that the elastically deformable connecting device 3 can move into contact with the fixed stop system 5 via the movable stop device 34. When the elastically deformable connecting device 3 moves until it comes into contact with the fixed stop system 5, a restoring force F is exerted on the seismic mass 1 by the elastically deformable connecting device 3. R is given.

[0050] The fixed stop system 5 preferably comprises a number of stopper elements 5A, 5B at different positions relative to the support 2.

[0051] The direction, orientation and / or value of the restoring force can be defined as a function of the position of the stopper elements 5A, 5B of the fixed stop system 5 to which the movable stop device 34 is moved until it comes into contact.

[0052] If the axis As of the sensor is arranged vertically, the restoring force F exerted by the elastically deformable connecting device 3 on the seismic mass 1 is R can be directed either opposite to the gravity force experienced by the seismic mass 1 or in the same direction as said gravity force.

[0053] When the movable stop device 34 comes into contact with the fixed stop device 5, the elastically deformable connecting device 3 is under elastic tension. In particular, in the example shown in the figures, the (or each) spring forming the elastically deformable connecting device 3 is an elongated spring. <Movement System>

[0054] The movement system 4 allows the movement of the elastically deformable connecting device 3 in order to at least partially compensate for the gravitational forces, in particular those experienced by the seismic mass.

[0055] In various embodiments of the present invention, as shown in Figures 2 to 7A, the elastically deformable connecting device 3 is moved by applying an electrostatic force Fe to a movable stop device 34 of the elastically deformable connecting device 3. The movable stop device 34 is electrically conductive. The movable stop device 34 can be fixed to the elastically deformable connecting device 3 or form part of said elastically deformable connecting device 3.

[0056] In an alternative embodiment, movement of the elastically deformable connecting device 3 can be performed by application of a magnetic force or via piezoelectric stress to the movable stop device 34 of the elastically deformable connecting device 3 .

[0057] Alternatively and / or in combination, the elastically deformable connecting device 3 may be moved mechanically by a pivot mechanism associated with a counterweight, as shown for example in FIG.

[0058] In one embodiment of the present invention, as particularly shown in Figure 2, the movement system 4 includes an electrode system 40 and a control unit 100. The control unit 100 is configured to apply a voltage generated or supplied from an energy source, such as a battery included in the accelerometer, to at least one electrode of the electrode system in order to apply an electrostatic force Fe to the elastically deformable connecting device 3.

[0059] In one embodiment of the present invention, as particularly shown by way of example in Figures 2 to 6, the electrode system comprises first and second electrodes on opposite sides of the elastically deformable connecting device 3, and the fixed stop system 5 comprises two stoppers 5A, 5B on opposite sides of the elastically deformable connecting device 3.

[0060] In one embodiment of the present invention, each electrode of the electrode system is referred to as activatable / deactivatable, in the sense that a predetermined voltage can or cannot be applied to said electrode via said control unit 100. If the second electrode 4B is deactivated (i.e., not receiving a voltage by the control unit 100), activation of the first electrode 4A (i.e., application of a predetermined voltage to said electrode by the control unit 100) therefore moves the movable stopper 34 of the elastically deformable connecting device 3 until it contacts the fixed stopper 5A. Activation of the second electrode 4B (first electrode 4A is deactivated) therefore moves the movable stopper 34 of the elastically deformable connecting device 3 until it contacts the fixed stopper 5B.

[0061] Similarly, fixed stops 5A and 5B can be used as electrodes to attract the movable stopper. To prevent excessive leakage current between the movable and fixed stops when mechanical contact is made between them, an insulator can be provided on or around one or more of the fixed or movable stops where the contact area between the stops is smaller.

[0062] The electrode system 40 is controlled to apply an electrostatic force Fe in a predetermined direction and orientation to the movable stop device 34, causing the elastically deformable connection device 3 to move relative to a portion of the stop system 5, thereby imparting tension / elastic deformation to the elastically deformable connection device 3.

[0063] The control unit 100 controls the electrode system 40 to apply a voltage to the or each electrode of the electrode system, thereby enabling the generation of an electrostatic moving force on the movable stop device 34 associated with the electrode system 40 towards a part of the fixed stop system 5, which is greater than the minimum force required to place the movable stop device 34 in contact with said part of the fixed stop system 5. The application of a constant voltage adapted (i.e. sufficient) to move the elastically deformable connecting device 3 until it comes into contact with the fixed stop system 5 means that it is not necessary to provide a loop system for regulating the voltage applied to the electrodes.

[0064] In one embodiment of the present invention, the applied predetermined voltage is said to be sufficient, meaning that in the absence of the fixed stop system 5, the distance that the movable stop device 34 of the elastically deformable connecting device 3 is displaced from its rest position, defined as the position of the movable stop device 34 in the absence of a voltage applied to the electrode system and in the absence of static forces experienced by the seismic mass due to the application of said voltage, exceeds the distance that the application of said voltage to the electrode system would cause the movable stop device 34 to come into contact with (and therefore be fixed to) the fixed stop system 5.

[0065] Alternatively, a smaller force can be applied sinusoidally at the resonant frequency of the system formed by the elastically deformable connecting device 3 and the corresponding movable stop device. Indeed, in a vacuum environment, vibrations lead to increasingly larger movements of the movable stop device 34, and if this movement brings the movable stop device 34 into contact with the fixed stop device, the space between the electrode and the elastically deformable connecting device 3 decreases, resulting in a larger electrostatic force for a given voltage. The electrostatic force applied when the movable stop device 34 is in contact with the fixed stop system 5 must be greater than the restoring force on the elastically deformable connecting device 3 and the movable stop device 34 as a whole, in order to allow the movable stop device 34 to remain in contact with the fixed stop system 5 when the mass is further accelerated.

[0066] Such a combination of the electrode system 40 with the movable stop device 34 and the fixed stop system 5 connected to the elastically deformable connecting device 3 makes it possible to apply a restoring force to the seismic mass 1 that is adjustable by discrete values, using electrostatic forces to pull the movable stop device 34 against the fixed stop system 5. This generates an adjustable restoring force (depending on the activated electrodes) in the mass 1 that makes it possible to compensate for gravity.

[0067] The movable stop device 34 is mechanically stopped by the fixed stop system 5. The overall noise of the accelerometer is not affected by the noise of electrostatic forces.

[0068] Therefore, depending on the direction and orientation of the electrostatic pull, the restoring force can compensate for the static forces experienced by the mass, which may have various values ​​and directions or orientations. In particular, the restoring force can compensate for the gravitational force experienced by the mass and the accelerometer when the sensitive axis is oriented vertically. If the accelerometer is oriented so that the sensitive axis of the sensor is oriented horizontally, no overall restoring force is provided.

[0069] As shown more particularly in FIGS. 2 to 6, the electrostatic force that can be generated by the electrode system is preferably reversible, and the resulting restoring force F applied to the mass 1 is R is reversible and can be changed subsequently if the orientation of the accelerometer relative to gravity is changed. <Connection Assembly>

[0070] In various embodiments of the invention shown in Figures 2 to 6 and described in detail below, the accelerometer may comprise a number of assemblies, called connection assemblies, each consisting of an elastically deformable connection device 3, an associated movable stop device 34, a fixed stop system 5 and a translation system 4. The connection assemblies may have common parts.

[0071] The connection assembly is in various positions relative to the mass 1 or support 2 so as to be able to generate the required resultant restoring force in terms of direction, orientation and value as a function of the orientation, direction and value of the static force, particularly gravity, to be compensated for.

[0072] As particularly shown by Figures 3A and 4A, in one embodiment of the present invention, movement of the movable stop device 34 of the connection device 3 into contact with the fixed stop system 5 of the connection assembly can be controlled by the control unit 100 separately from the rest of the connection assembly in a manner that adjusts the resulting compensation force applied to the mass. <Control unit>

[0073] The control unit 100 makes it possible to control the movement system 4 so as to be able to move the movable stopper 34 until it comes into contact with the fixed stop system 5 .

[0074] As shown schematically in FIG. 2A , the control unit 100 is configured for selective control of the position of the movable stop device 34 through a set of discrete positions including a rest position and one or more positions defined by one or more stoppers of the fixed stop system 5.

[0075] In one embodiment of the present invention, the discrete positions that the movable stop device 34 can assume include: a rest position corresponding to the absence of control of the movement of the movable stop device 34 by the control unit 100; the rest position corresponds to the absence of application of a voltage to the electrode system associated with the movable stop device 34 or the application of a zero potential difference between the electrode system and the movable stop device 34, which is reflected in the absence of application of a moving force (electrostatic force) to the movable stop device 34 and therefore the absence of application of an auxiliary restoring force to the seismic mass due to the movement of the movable stop device 34; a first position, in which the elastically deformable connecting device 3 is elastically tensioned, causing the elastically deformable connecting device 3 to exert a first restoring force on the seismic mass 1; the first position corresponds to a position obtained by applying a voltage to the electrode system, generating a unidirectional electrostatic force on the movable stop device 34, thereby exerting a corresponding first restoring force on the seismic mass 1.

[0076] The discrete positions that the movable stop device 34 can take preferably include a second position in which the elastically deformable connecting device 3 is elastically tensioned, causing the elastically deformable connecting device 3 to exert a second restoring force on the seismic mass 1; the second position corresponds to a position obtained by applying a voltage to the electrode system, causing the movable stop device 34 to generate an electrostatic force in the opposite direction (relative to the direction corresponding to the first position), thereby exerting a corresponding second restoring force on the seismic mass 1 in a direction opposite to the first restoring force.

[0077] The various discrete positions that the movable stop device 34 can assume depend on the configuration of the fixed stop system 5 .

[0078] The control unit 100 is then configured to allow selective control of the discrete positions of the movable stop devices 34 of each connection assembly. Thus, by controlling the position of each movable stop device 34 independently of one another, it is possible to obtain one of the discrete positions available for the corresponding movable stop device 34, imparting (local) restoring forces to the seismic mass 1, some of which may have different properties (orientation, value, direction), and to obtain an overall restoring force imparted to the seismic mass 1 by all the movable stop devices 34, adjustable depending on the selected combination of positions of the movable stop devices 34.

[0079] In FIG. 2A, the various positions that the movable stop device 34 can assume are shown superimposed on the same schematic diagram, but are of course selectively taken.

[0080] The above description, in particular the description with reference to Figure 2A of the simplified case of a connection assembly formed by a fixed stop system 5, an elastically deformable connection device 3, a movable stop device 34 and a movement system 4 (not shown), is also applicable to situations in which the accelerometer comprises multiple connection assemblies at different positions relative to the mass, as is particularly shown schematically in Figures 2 and 3 to 6.

[0081] Thus, the control unit 100 can be configured to control the connection assemblies in such a way that, depending on the configuration of the stoppers and connection assemblies of the fixed stop system through which the movable stop device moves, it applies to the seismic mass 1 a restoring force whose direction, orientation and / or value differs from that of a restoring force applied by another connection assembly via the elastically deformable connection device 3.

[0082] The difference between the two restoring forces may be a difference in the direction of movement of the movable stop device relative to the stoppers of the fixed stop system and / or a difference in value depending on the configuration of the connection assembly, for example the stiffness of the elastically deformable connection device 3 (which depends on its length, width, height and the Young's modulus of the material used) and / or the distance between the movable stop device 34 and the fixed stop device 5 (considered in the rest position) (in particular the distance between the movable stop device 34 and the stoppers 5A, 5B of the fixed stop device 5).

[0083] Thus, control of the connection assembly by the control unit 100 makes it possible to obtain various discrete values ​​of the overall restoring force resulting from the position of the movable stop device 34 controlled by the control unit.

[0084] This design of the accelerometer allows for adaptation of the overall restoring force applied to the mass as a function of the orientation of the accelerometer. In particular, the accelerometer (more specifically, the sensitive axis of the acceleration sensor) can be positioned vertically downward or upward, horizontally, or at an angle. If the accelerometer is inclined relative to the direction of the static force to be compensated for, the direction of the static force to be compensated for is vertical, for example, in the case of gravity. In this case, the value of the static force to be compensated for corresponds to the value of the static force projected onto the sensitive axis As.

[0085] In Figure 3 an embodiment of the accelerometer is represented, shown in a simplified manner, in a configuration in which the movable stop device 34 is in a rest position corresponding to the absence of an electrostatic force applied to the corresponding elastically deformable connecting device 3, i.e. the absence of an electrostatic force applied to the movable stop device 34.

[0086] 3A, the accelerometer is configured such that the acceleration sensor is horizontally positioned, i.e., the axis A s is horizontal. Thus, in the horizontal position of the accelerometer, the unit 100 can be configured to control the movement system 40 such that the movable stop devices 34 are pulled in opposite directions to maintain a zero overall restoring force on the seismic mass.

[0087] Depending on the configuration of the accelerometer, some or all of the movable stop devices 34 may remain in a stationary position.

[0088] 3B, the accelerometer is configured such that the acceleration sensor is vertically oriented, i.e., the axis A is vertical. Therefore, in the vertical position of the accelerometer, the unit 100 can be configured to control the electrode system 40 so that the movable stop device 34 is pulled in the same direction as and opposite to the gravity force acting on the seismic mass, so that the movable stop device 34 contacts the fixed stop 5A.

[0089] In one embodiment, the accelerometer includes at least three connection assemblies, allowing for multiple restoring force values ​​to be provided depending on the position occupied by the movable stop device 34 relative to each of the connection assemblies.

[0090] In one embodiment of the invention, two opposite sides of the seismic mass 1 are provided with at least three connection assemblies, for example four assemblies as in the example of FIG.

[0091] As shown in FIG. 4A , for an accelerometer orientation in which the accelerometer has a sensitivity axis As inclined with respect to gravity g and only the value of the projection of gravity g in the direction of axis As needs to be compensated, the control unit 100 can be configured to obtain an overall restoring force on the seismic mass 1 that compensates for gravity by commanding, on each side of the seismic mass 1, movement of some of the movable stop devices 34, for example the three highest movable stop devices 34, relative to stopper 5A of the fixed stop system 5, and movement of some other movable stop devices 34, for example the lowest movable stop device 34, relative to stopper 5B of the fixed stop system 5.

[0092] The control unit 100 may, for example, take the form of a microprocessor and a data memory in which software instructions executable by said microprocessor are stored, or may take the form of a microcontroller.

[0093] In other words, the functions and steps described can be implemented in the form of software or hardware (e.g., programmable gate arrays). In particular, the functions and steps performed by the control unit can be implemented by an instruction set or software implemented in a processor or controller for controlling the movement system of the or each elastically deformable connection device, or for controlling a processing unit for measuring acceleration, or by dedicated electronic components or programmable logic gate array (FPGA) or application specific integrated circuit (ASIC) type components. A combination of software and electronics is also possible.

[0094] A control or processing unit is therefore an electronic unit and / or software. When it is specified that said unit is configured to perform a certain operation, it means that the unit comprises instructions and corresponding execution means that enable the unit to perform said operation and / or that the unit comprises corresponding electronic components. Specific Embodiments

[0095] The elastically deformable connecting devices 3 of a connection assembly can have at least one physical characteristic, such as stiffness in the case of a spring, that differs from that of the elastically deformable connecting devices 3 of another connection assembly. If the elastically deformable connecting devices 3 are springs, one or more springs can have different technical characteristics from one spring to another in a manner that results in different values ​​of local restoring forces resulting from the loading of those springs. Such a configuration allows for even finer adjustment of the overall restoring force applied to the mobile mass.

[0096] Spring restoring force F R is K * x, where K is the stiffness of the spring and x is the movement of the movable stopper 34 from its rest position until it contacts the stopper of the fixed stop system 5.

[0097] Therefore, in some embodiments of the present invention, the restoring force F of each springR can be adjusted by changing the design dimensions of the spring (thickness / length / width / curvature of the spring...) or by adjusting the distance between the movable stop 34 and the stop of the fixed stop system 5 or by changing the material used for the spring. Figure 5 shows an example with springs of different lengths on each side of the mass, where the local restoring force F exerted on the seismic mass by the longer springs R ' is the restoring force F exerted on the seismic mass by the shorter spring R This indicates that the

[0098] In another embodiment of the solution, as shown for example in Figure 6, the movement system 4 can comprise a lever system configured to allow the movable stop device 34 to be moved relative to the stopper 5A or 5B of the fixed stop system 5. The lever system is configured so that, for each assembly connecting the mass 1 to the support 2, a counterweight 46 (e.g. of small weight compared to the seismic mass) fixed to a lever 36 which is itself connected to the movable stop device 34, is used to release the movement of the counterweight due to gravity, thereby causing the lever 36 to rotate about the pivot axis A36 to move the movable stop device 34 relative to the fixed stopper of the fixed stop system 5.

[0099] The invention is not limited to the embodiments shown in the drawings.

[0100] Furthermore, the term "comprises" does not exclude other elements or steps. Moreover, features or steps described with reference to one of the above-disclosed embodiments may also be used in combination with other features or steps of other above-disclosed embodiments.

Claims

1. ・Support (2); a seismic mass (1) associated with an acceleration sensor having at least one acceleration sensitivity axis (As), said seismic mass being subject to forces induced by the acceleration to be measured and to static forces such as gravitational or inertial forces; and - an elastically deformable connecting device (3), such as a spring, connecting the seismic mass (1) to the support (2); 1. An accelerometer comprising: The accelerometer further comprises: a fixed stop system (5) and a movable stop device (34) fixed to or forming part of said elastically deformable connecting device (3); The elastically deformable connecting device (3) is elastically deformed to apply a restoring force (F Ｒ a movement system (4) configured to move the movable stop device (34) relative to the fixed stop system (5) in a manner that adds 1. An accelerometer comprising:

2. 2. The accelerometer of claim 1, wherein the movable stop device is electrically conductive and the movement system comprises an electrode system having at least one electrode, preferably at least two electrodes, and a control unit configured to apply a voltage to the at least one electrode to exert an electrostatic force on the movable stop device, causing it to move until it comes into contact with the fixed stop system.

3. 3. The accelerometer of claim 2, wherein the control unit (100) is configured to control the electrode system (40) to apply a predetermined voltage to the at least one electrode to generate an electrostatic force on the movable stop device (34) that is greater than a minimum force required to hold the movable stop device (34) in contact with the fixed stop system (5).

4. 4. The accelerometer according to claim 2 or 3, wherein the electrode system (40) comprises first and second electrodes (4A, 4B) on opposite sides of the elastically deformable connecting device (3), and the fixed stop system (5) comprises two stoppers (5A, 5B) on opposite sides of the elastically deformable connecting device (3), and wherein a voltage of a predetermined value to a first electrode (4A) causes the movable stop device (34) to move until it contacts the first stopper (5A) of the fixed stop system (5), and a voltage of a predetermined value to the second electrode (4B) causes the movable stop device (34) of the elastically deformable connecting device (3) to move until it contacts the second stopper (5B) of the fixed stop system (5).

5. the accelerometer comprises a control unit (100), and the combination of the elastically deformable connection device (3), the movable stop device (34), the moving system (4) and the fixed stop system (5) forms a connection assembly, the accelerometer comprises a plurality of connection assemblies; 5. The accelerometer of claim 1, wherein the movement of the movable stop device (34) of the connection device (3) in contact with the stop system (5) of one connection assembly is controllable by the control unit (100) independently of the movement of the movable stop device (34) of another connection assembly.

6. 6. The accelerometer of claim 5, wherein the control unit (100) is configured to control the connection assembly (3) in a manner that applies a restoring force to the seismic mass (1) via the elastically deformable connection device (3), the restoring force being different from the restoring force applied to the seismic mass (1) by another connection assembly.

7. 7. The accelerometer of claim 6, wherein the elastically deformable connection devices (3) of at least one connection assembly have at least one physical characteristic, such as length and / or stiffness, that differs from the corresponding physical characteristic of the elastically deformable connection devices (3) of another connection assembly of the accelerometer.

8. The accelerometer of any one of claims 1 to 7, wherein the accelerometer is a micro-electro-mechanical system.

9. An accelerometer according to any one of claims 1 to 8 in combination with an accelerometer according to claim 2, wherein the fixed stop system (5) is wholly or partly shared with the electrode system (40).

10. Accelerometer according to any one of the preceding claims, wherein the fixed stop system (5) is formed integrally with the support (2).

11. The accelerometer according to any one of the preceding claims, wherein the elastically deformable connecting device (3) is formed integrally with the support (2).

12. 12. The accelerometer of any one of claims 1 to 11, wherein the accelerometer comprises a control unit (100) for controlling the movement system (4), the control unit (100) being configured to enable selective control of the position of the movable stop device (34) from a set of discrete positions, preferably for each connection assembly in case the accelerometer comprises multiple connection assemblies.

13. The set of discrete positions of the movable stop device (34) includes the following positions: the rest position of the elastically deformable connecting device (3) corresponding to the absence of control of the movement of the movable stop device (34) by the control unit (100); a first tension position in which the movable stop device (34) is in contact with the fixed stop system (5) and the elastically deformable connection device (3) is under elastic tension, exerting a first restoring force on the seismic mass (1); and a second tension position, preferably in which the mobile stop device (34) is in contact with the fixed stop system (5) and the elastically deformable connection device (3) is under elastic tension and exerts a second restoring force on the seismic mass (1), the second restoring force being different from the first restoring force; An accelerometer according to any one of the preceding claims.

14. A method for at least partial compensation of static forces, such as gravity, experienced by the seismic mass (1) of an accelerometer according to any one of claims 1 to 13, comprising: The elastically deformable connecting device (3) is under elastic tension and exerts a restoring force (F) which at least partially compensates for the static forces experienced by the seismic mass (1). Ｒ moving the movable stop device (34) relative to the fixed stop system (5) so as to apply a force of 100 MPa to the seismic mass (1).

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