Acceleration sensor having spring force compensation

• US 10,168,351 B2
• Filed: 01/27/2016
• Issued: 01/01/2019
• Est. Priority Date: 01/29/2015
• Status: Active Grant

• Current Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Inventors: Koenig, Stefan, Leinfelder, Peter
• Primary Examiner(s): Kwok, Helen C
• Application Number:
  US15/547,312
• Publication Number:
  US 20180024160A1
• Time in Patent Office: 1,070 Days
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 2203/051 Translation according to an axis parallel to the substrate
• CPC Class Codes: B81B 3/0054 For holding or placing an element in a given position
• CPC Class Codes: B81B 3/0059 Constitution or structural means for controlling the movement not provided for in groups B81B3/0037 - B81B3/0056
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/0862 being provided with particular means being integrated into a MEMS accelerometer structure for providing particular additional functionalities to those of a spring mass system
• CPC Class Codes: G01P 2015/0882 for providing damping of vibrations

Abstract

The invention relates to an acceleration sensor (100) having a sensor material (120) which is mounted by means of spring elements (130) so as to be movable along a movement axis (x) over a substrate (110), first trim electrodes (140) which are connected to the sensor material (120), and second trim electrodes (150) which are connected to the substrate (110) and are associated with the first trim electrodes (140). When the sensor material is deflected along the movement axis, a spring force acting on the sensor material (120) is generated by the spring elements (130), and when the sensor material (120) is deflected, an electrostatic force acting on the sensor material (120), which counteracts the spring force, is generated by application of an electrical trim voltage between the first trim electrodes (140) and the second trim elements (150).

Claims

1. An acceleration sensor comprising:

a sensor material which is mounted by means of spring elements so as to be movable along a movement axis (x) over a substrate

first trim electrodes which are connected to the sensor material, the first trim electrodes including comb electrodes comprised of electrode fingers and a region from which the electrode fingers extend; and

second trim electrodes formed as electrode plates and which are connected to the substrate and are associated with the first trim electrodes, wherein

when the sensor material is deflected along the movement axis (x), a spring force acting on the sensor material is generated by the spring elements;

when the sensor material is deflected, an electrostatic force acting on the sensor material, which counteracts the spring force, is generated by application of an electrical trim voltage between the first trim electrodes and the second trim electrodes,

wherein a side of the region from which the electrode fingers extend forms plate capacitors with the associated second trim electrodes where the plate capacitors generate the electrostatic force.

2. The acceleration sensor according to claim 1 comprising:

sensor electrodes which are connected to the sensor material; and

detection electrodes which are connected to the substrate and are associated with the sensor electrodes, wherein

a deflection of the sensor material along the movement axis (x) can be determined through a change of an electrical detection voltage between or of an electrical charge on the sensor electrodes and the associated detection electrodes.

3. The acceleration sensor according to claim 2, wherein

a part of the sensor electrodes is formed as the first trim electrodes;

and wherein

the trim voltage between the sensor electrodes formed as the first trim electrodes and the second trim electrodes dampens the deflection of the sensor material.

4. The acceleration sensor according to claim 1, wherein

the first trim electrodes are arranged symmetrically to a plane of symmetry perpendicular to the movement axis (x) on the sensor material;

and wherein

the second trim electrodes are arranged symmetrically to the axis of symmetry perpendicular to the movement axis (x) on the substrate.

5. The acceleration sensor according to claim 1, wherein

the electrostatic force generated by the first trim electrodes and the second trim electrodes is equal to the spring force generated by the spring elements.

6. The acceleration sensor according claim 1, wherein

a part of the first trim electrodes is formed as electrode plates;

and wherein

the first trim electrodes, which are formed as electrode plates, and the associated second trim electrodes form plate capacitors.

7. The acceleration sensor according to claim 2, wherein

the sensor material, through setting of the detection voltage, is kept in a neutral position in which the acceleration required for further deflection is independent of the trim voltage.

8. The acceleration sensor according to claim 7, wherein

a computing unit determines, from a neutral position, a deviation of a first position of the sensor material in which no spring force acts on the sensor material, from a second position of the sensor material in which no force generated by the sensor electrodes and the detection electrodes acts on the sensor material.

9. The acceleration sensor according to claim 7, wherein

a computing unit, based on changes of a neutral position and changes of the trim voltage required to cancel the spring force, checks the acceleration sensor for errors.

10. The acceleration sensor according to claim 1, wherein the acceleration sensor is a micro-electro-mechanical system.