Microelectromechanical structure with enhanced rejection of acceleration noise

Abstract

An integrated MEMS structure includes a driving assembly anchored to a substrate and actuated with a driving movement. A pair of sensing masses suspended above the substrate and coupled to the driving assembly via elastic elements is fixed in the driving movement and performs a movement along a first direction of detection, in response to an external stress. A coupling assembly couples the pair of sensing masses mechanically to couple the vibration modes. The coupling assembly is formed by a rigid element, which connects the sensing masses and has a point of constraint in an intermediate position between the sensing masses, and elastic coupling elements for coupling the rigid element to the sensing masses to present a first stiffness to a movement in phase-opposition and a second stiffness, greater than the first, to a movement in phase, of the sensing masses along the direction of detection.

1 . An angular velocity sensor comprising:
 a substrate;   four substantially planar masses disposed substantially in a plane parallel to and above the substrate, the four substantially planar masses move in phase opposition; wherein in phase opposition the four substantially planar masses move in the plane simultaneously away or simultaneously towards a point; and   a X-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses; a Y-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses; a Z-axis capacitive sensor including a moveable electrode attached to the at least one of the four substantially planar masses and a fixed electrode substantially parallel to the moveable electrode and in the plane; wherein the X-axis capacitive sensor, Y-axis capacitive sensor, and Z-axis capacitive sensor sense angular velocity of the angular velocity sensor about three different input axes of the angular velocity sensor.   
     
     
         2 . The angular velocity sensor of  claim 1  includes a driving assembly, wherein the driving assembly drives the four substantially planar masses in phase opposition. 
     
     
         3 . The angular velocity sensor of  claim 2 , wherein the point is a center of mass of the four substantially planar masses. 
     
     
         4 . The angular velocity sensor of  claim 3 , wherein the center of mass of the four substantially planar masses does not substantially move when the four substantially planar masses are moving in an in phase opposition operation. 
     
     
         5 . The angular velocity sensor of  claim 2 , which includes a capacitive sensor for sensing the motion of at least one planar mass in phase opposition; wherein the driving assembly drives the four substantially planar masses as a single-drive system having a single drive mode, in which only a single drive circuit is used to control the driving assembly. 
     
     
         6 . The angular velocity sensor of  claim 2 , wherein the driving assembly comprises a plurality of driving electrodes. 
     
     
         7 . The angular velocity sensor of  claim 1 , wherein the angular velocity sensor includes four coupling elements which couple the four substantially planar masses such that each mass is flexibly coupled to two of the other substantially planar masses via two of the four coupling elements. 
     
     
         8 . The angular velocity sensor of  claim 7 , wherein the four coupling elements cause the four substantially planar masses to move in phase opposition. 
     
     
         9 . The angular velocity sensor of  claim 1 , further comprising a frame parallel to the plane and flexibly coupled to the four substantially planar masses, wherein the four substantially planar masses are situated outside of the frame and are substantially coplanar within the plane. 
     
     
         10 . The angular velocity sensor of  claim 1  wherein in phase opposition is a resonant mode in which the four substantially planar masses are moved at a resonant frequency. 
     
     
         11 . The angular velocity sensor of  claim 1 , which includes a capacitive sensor for sensing the motion of at least one planar mass in phase opposition. 
     
     
         12 . The angular velocity sensor of  claim 1  wherein at least one of the four substantially planar masses is flexibly coupled to the substrate through associated anchorage elements. 
     
     
         13 . The angular velocity sensor of  claim 12 , wherein the associated anchorage elements further comprises:
 a driving mass suspended to the substrate via an elastic anchorage element; and   an elastic coupling element flexibly coupling the at least one of the four substantially planar masses to the driving mass.   
     
     
         14 . The angular velocity sensor of  claim 13  includes a plurality of driving electrodes; wherein the plurality of driving electrodes includes an electrode on the driving mass and an electrode fixed to the substrate. 
     
     
         15 . The angular velocity sensor of  claim 13 , wherein the elastic anchorage element is substantially compliant to motion in phase opposition. 
     
     
         16 . The angular velocity sensor of  claim 13  wherein, the elastic coupling element is substantially stiff to translation in phase opposition. 
     
     
         17 . The angular velocity sensor of  claim 1 , further comprising a frame parallel to the plane and flexibly coupled to the four substantially planar masses, wherein the four substantially planar masses are situated inside of the frame and are substantially coplanar within the plane. 
     
     
         18 . An angular velocity sensor comprising:
 a substrate;   four substantially planar masses disposed substantially in a plane parallel to and above the substrate, the four substantially planar masses move in phase opposition; wherein in phase opposition the four substantially planar masses move in the plane simultaneously away or simultaneously towards a center of mass of the four substantially planar masses; wherein the center of mass of the four substantially planar masses does not substantially move when the four substantially planar masses are moving in phase opposition;   a X-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses; a Y-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses; a Z-axis capacitive sensor including a moveable electrode attached to the at least one of the four substantially planar masses and a fixed electrode substantially parallel to the moveable electrode and in the plane;   a driving assembly that drives the four substantially planar masses in phase opposition;   four coupling elements which couple the four masses such that each mass is flexibly coupled to two of the other masses via two of the four coupling elements; wherein the four coupling elements cause the four masses to move in phase opposition; and   a frame parallel to the plane and flexibly coupled to the four substantially planar masses, the four substantially planar masses surrounding an outside of the frame within the plane; wherein at least one of the four substantially planar masses is flexibly coupled to the substrate through an associated anchorage; wherein the associated anchorage further comprises a driving mass suspended to the substrate via an elastic anchorage element; and an elastic coupling element flexibly coupling the at least one of the four substantially planar masses to the driving mass; wherein the driving assembly includes an electrode coupled to the driving mass and an electrode fixed to the substrate; wherein the elastic anchorage element is substantially compliant to motion in phase opposition; wherein the elastic coupling element is substantially stiff to translation in phase opposition.   
     
     
         19 . The angular velocity sensor of  claim 18 , wherein in phase opposition is a resonant mode in which the four substantially planar masses are moved at a resonant frequency. 
     
     
         20 . The angular velocity sensor of  claim 18 , wherein the driving assembly drives the four substantially planar masses as a single-drive system having a single drive mode, in which only a single drive circuit is used to control the driving assembly. 
     
     
         21 . A method for utilizing an angular velocity sensor comprising:
 moving four substantially planar masses disposed substantially in a plane parallel to in phase opposition to each other; wherein in phase opposition the four substantially planar masses move in the plane simultaneously away or simultaneously towards a point;   providing a X-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses;   providing a Y-axis capacitive sensor including an electrode formed on the substrate and a portion of at least one of the four substantially planar masses; and   providing a Z-axis capacitive sensor including a moveable electrode attached to the at least one of the four substantially planar masses and a fixed electrode substantially parallel to the moveable electrode and in the plane; wherein the X-axis capacitive sensor, Y-axis capacitive sensor, and Z-axis capacitive sensor sense angular velocity of the angular velocity sensor about three different input axes of the angular velocity sensor.   
     
     
         22 . An angular velocity sensor comprising:
 (a) a substrate;   (b) four substantially planar masses disposed substantially in a plane parallel to and above the substrate, the four substantially planar masses being suspended so as to move in the plane simultaneously away or simultaneously towards a point;   (c) an X-axis capacitive sensor including:
 (1) an electrode formed on the substrate and 
 (2) a portion of at least one of the four substantially planar masses; 
   (d) a Y-axis capacitive sensor including:
 (1) an electrode formed on the substrate and 
 (2) a portion of at least one of the four substantially planar masses; 
   (e) a Z-axis capacitive sensor including:
 (1) a moveable electrode attached to the at least one of the four substantially planar masses and 
 (2) a fixed electrode substantially parallel to the moveable electrode and in the plane; 
   (f) wherein the X-axis capacitive sensor, the Y-axis capacitive sensor, and the Z-axis capacitive sensor sense angular velocity of the angular velocity sensor about three different input axes of the angular velocity sensor.