Method of driving MEMS sensor with balanced four-phase comb drive
First Claim
1. A method of vibrating a proof mass in a microelectromechanical sensor at a desired motor frequency wherein the proof mass is flexibly supported above a substrate with first, second, third and fourth moveable electrodes connected to the proof mass and adjacent to first, second, third and fourth fixed electrodes connected to the substrate, respectively, the method comprising the steps of:
- applying to the first and third fixed electrodes first and third periodic driveforms that operate to periodically pull the proof mass in one direction;
applying to the second and fourth fixed electrodes second and fourth periodic driveforms that operate to periodically pull the proof mass in the opposite direction; and
phasing the first, second, third and fourth periodic driveforms relative to one another to cause the first and third periodic driveforms to pull the proof mass in the one direction during one period of periodic proof mass movement and to cause the second and fourth periodic driveforms to pull the proof mass in the opposite direction in a subsequent period of periodic proof mass movement.
2 Assignments
0 Petitions
Accused Products
Abstract
Disclosed is a microelectromechanical sensor (10) with an element (40) that is driven into oscillations with drive forms (φ1, φ2, φ3, φ4) through the use of arms (50), comb-drives (55A, 55B, 55C, and 55D) and corresponding comb-fingers (51, 61) and wherein a sense signal is transduced with capacitive sense electrodes (26, 26). The driveforms (φ1, φ2, φ3, φ4) are provided in four-phases and are applied in pairs (φ1, φ3 and φ2, φ4) that are 180 degrees out of phase with respect to one another such that the driveforms are substantially self-canceling with regard to any driveform energy that feeds through any parasitic capacitance (99) that connects the comb-drives (55A, 55B, 55C, and 55D) to the capacitive sense electrodes (26, 26).
52 Citations
17 Claims
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1. A method of vibrating a proof mass in a microelectromechanical sensor at a desired motor frequency wherein the proof mass is flexibly supported above a substrate with first, second, third and fourth moveable electrodes connected to the proof mass and adjacent to first, second, third and fourth fixed electrodes connected to the substrate, respectively, the method comprising the steps of:
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applying to the first and third fixed electrodes first and third periodic driveforms that operate to periodically pull the proof mass in one direction;
applying to the second and fourth fixed electrodes second and fourth periodic driveforms that operate to periodically pull the proof mass in the opposite direction; and
phasing the first, second, third and fourth periodic driveforms relative to one another to cause the first and third periodic driveforms to pull the proof mass in the one direction during one period of periodic proof mass movement and to cause the second and fourth periodic driveforms to pull the proof mass in the opposite direction in a subsequent period of periodic proof mass movement. - View Dependent Claims (2, 3, 4, 5)
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6. A method of vibrating a proof mass in a microelectromechanical sensor at a desired motor frequency wherein the proof mass is flexibly supported above a substrate with first, second, third and fourth moveable electrodes connected to the proof mass and adjacent to first, second, third and fourth fixed electrodes connected to the substrate, respectively, the method comprising the steps of:
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applying to the first and third fixed electrodes first and third periodic driveforms that periodically pull the proof mass in the one direction, the first and third periodic driveforms being 180 degrees out of phase with respect to one another; and
applying to the second and fourth fixed electrodes second and fourth periodic driveforms that periodically pull the proof mass in the opposite direction, the second and fourth periodic driveforms being 180 degrees out of phase with respect to one another. - View Dependent Claims (7)
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8. A method of driving a proof mass at a desired motor frequency wherein the proof mass is flexibly supported above a substrate in a microelectromechanical sensor, the method comprising the steps of:
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providing a first movable electrode that is connected to the proof mass and a first fixed electrode for pulling the proof mass in one direction when a voltage differential exists between the first movable electrode and the first fixed electrode; and
providing a second movable electrode that is connected to the proof mass and a second fixed electrode for pulling the proof mass in an opposite direction when a voltage differential exists between the second movable electrode and the second fixed electrode. providing a third movable electrode that is connected to the proof mass and a third fixed electrode for helping the first fixed and moveable electrodes pull the proof mass in said one direction when a voltage differential exists between the third movable electrode and the third fixed electrode;
providing a fourth movable electrode that is connected to the proof mass and a fourth fixed electrode for helping the second fixed and movable electrodes pull the proof mass in said opposite direction when a voltage differential exists between the third movable electrode and the third fixed electrode;
applying to the first fixed electrode a first periodic driveform at a one-half motor frequency that operates to periodically pull the proof mass in the one direction; and
applying to the second fixed electrode a second periodic driveform at the half motor frequency that operates to periodically pull the proof mass in the opposite direction, applying to the third fixed electrode a third periodic driveform at a one-half motor frequency that operates to periodically pull the proof mass in the one direction; and
applying to the fourth fixed electrode a fourth periodic driveform at a one-half motor frequency that operates to periodically pull the proof mass in the opposite direction, wherein the first and third periodic driveforms are 180 degrees out of phase with respect to one another, wherein the second and fourth periodic drives are 180 degrees out of phase with respect to one another, and wherein the first and second periodic drive forms are substantially ninety degrees out of phase with respect to one another and the third and fourth periodic drive forms are substantially ninety degrees out of phase with respect to one another such that the proof mass is repetitively and alternately pulled back and forth by the first and second periodic driveforms and by the third and fourth periodic driveforms at the motor frequency. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of generating drive waveforms for excitation of an oscillating mass driven by electrostatic actuation comprising the steps of:
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detecting a periodic motion of the oscillating mass with sense electrodes;
producing a periodic waveform that is coherent in phase with the periodic motion of the oscillating mass and with a period of even multiple of the periodic motion of the oscillating mass;
generating four orthogonal waveforms with phases of 0°
, 90°
, 180°
, and 270°
, and whose edges are coincident with a peak amplitude of the oscillating mass; and
summing the orthogonal waveforms together to form a four-phase set of drive signals that produce torque over the entire sensor motor duty cycle.
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Specification