Sensor system and method for calibrating a sensor system

• US 8,833,135 B2
• Filed: 08/03/2011
• Issued: 09/16/2014
• Est. Priority Date: 08/12/2010
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Franke, Axel, Hattass, Mirko, Buhmann, Alexander, Keck, Marian
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): Mercado, Alexander
• Application Number:
  US13/197,084
• Publication Number:
  US 20120036915A1
• Time in Patent Office: 1,140 Days
• Field of Search: 73/13.7, 73/13.8, 738/623.81, 738/625.2, 738/626.21, 738/626.22, 738/626.8, 734/88, 735/140.1, 735/143.2, 735/143.5, 735/143.8
• US Class Current: 73/1.38
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A sensor system having a substrate and a mass which is movably suspended relative to the substrate is described, the sensor system including detection arrangement for detecting a deflection of the seismic mass relative to the substrate along a deflection direction, the detection arrangement including a first measuring electrode affixed to the substrate and a second measuring electrode affixed to the substrate, and a first overlap, which is perpendicular to the deflection direction, between the first measuring electrode and the seismic mass along the deflection direction is greater than a second overlap, which is perpendicular to the deflection direction, between the second measuring electrode and the seismic mass.

Claims

1. A sensor system, comprising:

a substrate,

a seismic mass movably suspended relative to the substrate; and

a detection arrangement to detect a deflection of the seismic mass relative to the substrate along a deflection direction, the detection arrangement including a first measuring electrode affixed to the substrate and a second measuring electrode affixed to the substrate, wherein a first overlap between the first measuring electrode and the seismic mass is larger than a second overlap between the second measuring electrode and the seismic mass, wherein an evaluation unit is configured to calibrate the sensor system as a function of a calibration factor that corresponds to;

a first capacitance between the first measuring electrode and the seismic mass,

a second capacitance between the second measuring electrode and the seismic mass, and

an overlap difference between the first overlap and the second overlap wherein the calibration factor also corresponds to a ratio between a voltage difference and the overlap difference of the first measuring electrode and the second measuring electrode relative to the seismic mass.

2. The sensor system as recited in claim 1, wherein the first overlap includes a partial covering of the seismic mass by the first measuring electrode perpendicular to the deflection direction, and the second overlap includes a partial covering of the seismic mass by the second measuring electrode perpendicular to the deflection direction, the first overlap along the deflection direction being larger than the second overlap.

3. The sensor system as recited in claim 1, wherein the seismic mass includes a first counter-electrode which is assigned to the first measuring electrode and a second counter-electrode which is assigned to the second measuring electrode in such a way that the first overlap is provided between the first measuring electrode and the first counter-electrode and the second overlap is provided between the second measuring electrode and the second counter-electrode.

4. The sensor system as recited in claim 1, wherein one of:

i) a length of the first measuring electrode along the deflection direction is not equal to a length of the second measuring electrode along the deflection direction, or ii) the length of the first measuring electrode along the deflection direction is largely equal to the length of the second measuring electrode along the deflection direction, the second measuring electrode being situated in such a way that it is offset in relation to the first measuring electrode along the deflection direction.

5. The sensor system as recited in claim 3, wherein at least one of:

i) the detection arrangement includes a further first measuring electrode which is largely structurally equivalent to the first measuring electrode and which is electrically conductively connected to the first measuring electrode and is situated perpendicularly to the deflection direction relative to the first counter-electrode in a manner which is largely mirror-symmetrical to the first measuring electrode, and ii) the detection arrangement includes a further second measuring electrode which is designed to be largely structurally equivalent to the second measuring electrode and which is electrically conductively connected to the second measuring electrode and is situated perpendicularly to the deflection direction relative to the second counter-electrode in a manner which is largely mirror-symmetrical to the second measuring electrode.

6. The sensor system as recited in claim 1, wherein the evaluation unit includes a capacitance-voltage converter.

7. The sensor system as recited in claim 1, wherein the sensor system is at least one of a micromechanical acceleration sensor and a micromechanical yaw sensor.

8. A method for calibrating a sensor system, the sensor system including a substrate, a mass movably suspended relative to the substrate, and a detection arrangement to detect a deflection of the seismic mass relative to the substrate along a deflection direction, the detection arrangement including a first measuring electrode affixed to the substrate and a second measuring electrode affixed to the substrate, wherein a first overlap between the first measuring electrode and the seismic mass is larger than a second overlap between the second measuring electrode and the seismic mass, the method comprising:

measuring a first electrical capacitance between the first measuring electrode and the seismic mass in a first method step;

measuring a second electrical capacitance between the second measuring electrode and the seismic mass in a second method step;

ascertaining a calibration factor for the sensor system in a third method step as a function of the first and second electrical capacitances and also as a function of an overlap difference between the first overlap and the second overlap.

9. The method as recited in claim 8, wherein a first voltage is ascertained as a function of the first electrical capacitance in the first method step with the aid of an evaluation unit and a second voltage is ascertained as a function of the second electrical capacitance in the second method step using the evaluation unit, the calibration factor being ascertained in the third method step as a function of the overlap difference and also as a function of the voltage difference between the first and second voltages.

10. The method as recited in claim 8, wherein the overlap difference between the first overlap and the second overlap along the deflection direction is ascertained in the third method step, and the seismic mass is deflected relative to the substrate along the deflection direction in a fourth method step, the third method step being carried out at least one of:

i) at a time prior to, and ii) during the first and second method steps.

11. The method as recited in claim 10, wherein the sensor system and the evaluation unit are calibrated as a function of the calibration factor in a fifth method step.