Method for detecting accelerations and rotation rates, and MEMS sensor
View Patent ↗The invention concerns a MEMS sensor and a method for detecting accelerations along, and rotation rates about, at least one, preferably two of three mutually perpendicular spatial axes x, y and z by means of a MEMS sensor ( 1 ), wherein at least one driving mass ( 6; 6.1, 6.2 ) and at least one sensor mass ( 5 ) are moveably arranged on a substrate ( 2 ) and the at least one driving mass ( 6; 6.1, 6.2 ) is moved relative to the at least one sensor mass ( 5 ) in oscillation at a driving frequency and when an external acceleration of the sensor occurs, driving mass/es ( 6; 6.1, 6.2 ) and sensor mass/es ( 5 ) are deflected at an acceleration frequency and, when an external rotation rate of the sensor ( 1 ) occurs, are deflected at a rotation rate frequency, and the acceleration frequency and rotation rate frequency are different. At the MEMS-sensor the driving mass/es ( 6; 6.1, 6.2 ) and sensor mass/es ( 5 ) are arranged on the substrate ( 2 ), and are balanced in the resting state by means of at least one of the anchors ( 3 ). In the driving mode the driving mass/es ( 6; 6.1, 6.2 ), when vibrating in oscillation about this at least one anchor ( 3 ), generate/s an imbalance of the driving mass/es ( 6; 6.1, 6.2 ) and the sensor mass/es ( 5 ) with respect to this at least one anchor ( 3 ), and the sensor elements detect deflections of the driving and sensor masses, due to torques and Coholis forces generated, with an acceleration frequency and/or a rotation rate frequency.
1. A micro-electro-mechanical-system (MEMS) sensor for detecting accelerations along and rotational movements about at least one of three mutually perpendicular spatial axes, x, y, and z, comprising:
a substrate arranged in an x-y plane;
at least one driving mass adapted to oscillate in a plane parallel to the substrate and driven in a linear motion along the x-axis;
at least one sensing mass connected to the least one driving mass via connecting springs, wherein the connecting springs bend to move the at least one sensing mass in a linear motion relative to the at least one driving mass during operation;
at least one anchor secured to the substrate and at least one anchor spring connected to the at least one driving mass or the at least one sensing mass;
sensing elements for sensing acceleration, rotation, or both of the MEMS sensor; and
drive elements for driving the at least one driving mass relative to the at least one sensing mass at a driving frequency,
wherein the at least one driving mass is adapted to generate an imbalance of the at least one driving mass and the at least one sensing mass with respect to the at least one anchor during operation.
2. A MEMS sensor as recited in claim 1 , wherein the at least one driving mass and the at least one sensing mass are adapted to deflect at an acceleration frequency that is equal to the driving frequency when the MEMS sensor is accelerated.
3. A MEMS sensor as recited in claim 1 , wherein the at least one driving mass and the at least one sensing mass are adapted to deflect at a rotation frequency that is double the driving frequency when the MEMS sensor is rotated.
4. A MEMS sensor as recited in claim 1 , wherein the at least one anchor spring is directly connected to the at least one driving mass and adapted to allow the at least one driving mass to move along the x-axis.
5. A MEMS sensor as recited in claim 4 , wherein the at least one anchor spring is adapted to allow at least one driving mass to rotate along the y- and z-axes.
6. A MEMS sensor as recited in claim 1 , wherein the at least one anchor is a central anchor.
7. A MEMS sensor as recited in claim 1 , wherein the connecting springs are adapted to move along the x-axis only, further comprising:
sensor springs connected to the at least one driving mass and the at least one sensing mass and adapted to allow the at least one sensing mass to move along y and z axes relative to the at least one driving mass.
8. A MEMS sensor as recited in claim 7 , wherein the at least one anchor spring is directly connected to the at least one sensing mass.
9. A MEMS sensor as recited in claim 8 , wherein the at least one driving mass includes first and second driving masses and the first driving mass is disposed outside the at least one sensing mass and the second driving mass is dispose inside the at least one sensing mass.
10. A MEMS sensor as recited in claim 9 , wherein the first one of the connecting springs is adapted to move along the x-axis and connected to the first driving mass and a second one of the connecting springs is adapted to move along the y-axis and connected to the second driving mass.
11. A MEMS sensor as recited in claim 8 , wherein a number of the at least one anchor spring is same as a number of the at least one anchor and wherein each of the at least one anchor spring is connected to a corresponding one of the at least one anchor.
12. A MEMS sensor as recited in claim 8 , wherein the at least one driving mass includes four driving masses disposed outside the sensing mass.
13. A MEMS sensor as recited in claim 12 , wherein the driving elements drive a first one of the four driving masses at a first driving frequency along the x-axis and a second one of the four driving masses at a second driving frequency along the y-axis.
14. A MEMS sensor as recited in claim 12 , wherein the at least one anchor is a central anchor.
15. A MEMS sensor as recited in claim 14 , wherein the at least one sensing mass is adapted to rotate and pivot about an axis passing through the central anchor.
16. A MEMS sensor as recited in claim 1 , wherein the sensing elements are adapted to measure a movement of the at least one driving mass.
17. A MEMS sensor as recited in claim 1 , wherein the sensing elements are adapted to measure a movement of the at least one sensing mass.
18. A MEMS sensor as recited in claim 1 , wherein the at least one anchor spring allows the sensing mass to rotate along the z-axis.
19. A MEMS sensor as recited in claim 1 , wherein the connecting springs cause the at least one driving mass rigidly coupled to the at least one sensing mass along the y- and t-axes.