Robust Self Testing of a Motion Sensor System
First Claim
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1. A method for self testing a MEMS device comprising:
- providing the MEMS device having a first reciprocally movable MEMS body carrying a first movable electrode establishing a capacitance with a first fixed electrode and a second reciprocally movable MEMS body carrying a second movable electrode establishing a capacitance with a second fixed electrode, each MEMS body movable in response to an applied acceleration;
applying a self-test voltage such that one of the MEMS bodies is urged to move against the movement it would naturally follow in response to an applied physical acceleration and the other MEMS body is urged to move in sympathy with the movement it would naturally follow in response to the same applied physical acceleration; and
applying self-test signals to at least one of the first and second fixed electrodes and the first and second movable electrodes so as to produce a common mode output signal from at least one of the first and second movable electrodes and the first and second fixed electrodes in response to physical acceleration of the MEMS device and to produce a differential output signal from the at least one of the first and second movable electrodes and the first and second fixed electrodes in response to unnatural repositioning of the first and second movable electrodes.
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Abstract
A method for self-testing a dual-mass linear accelerometer in which a self-test voltage is applied to urge the two masses to move in opposite directions. Self-test signals are then applied to obtain a differential mode signal to detect masses repositioned in opposing directions. During testing, common disturbances to the two masses are rejected as common mode signals.
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Citations
23 Claims
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1. A method for self testing a MEMS device comprising:
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providing the MEMS device having a first reciprocally movable MEMS body carrying a first movable electrode establishing a capacitance with a first fixed electrode and a second reciprocally movable MEMS body carrying a second movable electrode establishing a capacitance with a second fixed electrode, each MEMS body movable in response to an applied acceleration; applying a self-test voltage such that one of the MEMS bodies is urged to move against the movement it would naturally follow in response to an applied physical acceleration and the other MEMS body is urged to move in sympathy with the movement it would naturally follow in response to the same applied physical acceleration; and applying self-test signals to at least one of the first and second fixed electrodes and the first and second movable electrodes so as to produce a common mode output signal from at least one of the first and second movable electrodes and the first and second fixed electrodes in response to physical acceleration of the MEMS device and to produce a differential output signal from the at least one of the first and second movable electrodes and the first and second fixed electrodes in response to unnatural repositioning of the first and second movable electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for self testing a MEMS device comprising:
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providing the MEMS device having a first reciprocally movable MEMS body carrying a first movable electrode establishing a capacitance with a first fixed electrode and a second reciprocally movable MEMS body carrying a second movable electrode establishing a capacitance with a second fixed electrode, both MEMS bodies movable along a single axis; applying a self-test voltage such that the first MEMS body and the second MEMS body are urged to move in opposite directions; and applying self-test signals to at least one of the electrodes so as to produce a common mode output signal from at least one of the electrodes in response to movement of the first and second movable electrodes in the same direction and to produce a differential output signal from the at least one electrodes in response to opposing repositioning of the first and second movable electrodes. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A self-testable MEMS device comprising:
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first and second MEMS masses configured for physical displacement within the MEMS device in response to acceleration of the MEMS device, each first MEMS mass having at least one first associated movable electrode configured for movement therewith and at least one first associated fixed electrode, and each second MEMS mass having at least one second associated movable electrode configured for movement therewith and at least one second associated fixed electrode, wherein pairs of the fixed and movable electrodes establish capacitances, each capacitance varying in relation to spacing between the respective fixed and movable electrodes; and a signal generator configured to; apply at least one self-test voltage to at least one of the electrodes, such that one of the MEMS masses is urged to move against the movement it would naturally follow in response to an applied physical acceleration and the other MEMS mass is urged to move in sympathy with the movement it would naturally follow in response to the same applied physical acceleration; and after applying the at least one self-test voltage, apply self-test signals to at least one of the electrodes so as to produce a common mode output signal from at least one of the electrodes in response to physical acceleration of the MEMS device and to produce a differential output signal from the at least one of the electrodes in response to unnatural repositioning of the first and second movable electrodes. - View Dependent Claims (21, 22, 23)
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Specification