초록 ▼

Disclosed is a microelectromechanical sensor (10) with an element (40) that is driven into oscillations with drive forms (&phgr;1, &phgr;2, &phgr;3, &phgr;4) through the use of arms (50), comb-drives (55A,55B,55C, and55D) and corresponding comb-fingers (51, 61) and wherein a sense signal is transduc

Disclosed is a microelectromechanical sensor (10) with an element (40) that is driven into oscillations with drive forms (&phgr;1, &phgr;2, &phgr;3, &phgr;4) through the use of arms (50), comb-drives (55A,55B,55C, and55D) and corresponding comb-fingers (51, 61) and wherein a sense signal is transduced with capacitive sense electrodes (26, 26). The driveforms (&phgr;1, &phgr;2, &phgr;3, &phgr;4) are provided in four-phases and are applied in pairs (&phgr;1, &phgr;3and &phgr;2, &phgr;4) that are180degrees 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, and55D) to the capacitive sense electrodes (26, 26).

대표청구항 ▼

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 fi

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. The method of claim 1 wherein the first, second, third and fourth periodic driveforms are successively ninety degrees out of phase with respect to one another. 3. The method of claim 1 wherein the first and third periodic driveforms are 180 degrees out of phase with respect to one another and wherein the second and fourth periodic driveforms are 180 degrees out of phase with respect to one another such that an equal and opposite voltage differential is always applied at any one time, providing for cancelation of applied voltage and minimize feedthrough to sensors located elsewhere in the microelectromechanical sensor. 4. The method of claim 1 wherein there are multiple sets of first, second, third and fourth fixed and moveable electrodes in the microelectromechanical sensor and further comprising the step of simultaneously applying the first, second, third and fourth periodic drive forms to the respectively numbered fixed electrodes of each set, increasing the amplitude of movement given a particular operating voltage and operating environment. 5. The method of claim 1 further comprising the steps of:detecting the movement of the oscillating proof mass; and maintaining phase coherence between the oscillating proof mass and the driveforms based on the detected movement. 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: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. 7. The method of claim 6 wherein the first, second, third and fourth periodic driveforms are ninety degrees out of phase with respect to one another such that the proof mass is repetitively pulled back and forth by the first and third second periodic driveforms one the one hand, and by the second and fourth periodic driveforms on the other hand, collectively providing a desired amplitude of movement at a given motor frequency, supply voltage, and operating environment. 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: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 pe riodic 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. 9. The method of claim 8 wherein the first and second periodic driveforms are sinuosoidal approximations. 10. The method of claim 8 wherein the sinusoidal approximations are stepped approximations of a sinusoid. 11. The method of claim 8 wherein the first and second periodic driveforms are sinuosoids. 12. The method of claim 8 wherein the first and second periodic driveforms are sawtooth waves. 13. The method of claim 8 wherein the microelectromechanical sensor is a rotational rate sensor. 14. The method of claim 13 wherein the proof mass is a ring that is driven to oscillate in a plane about a central axis. 15. The method of claim 8 wherein the first and second fixed electrodes are connected to the substrate. 16. The method of claim 15 wherein the third and fourth fixed electrodes are connected to the substrate. 17. A method of generating drive waveforms for excitation of an oscillating mass driven by electrostatic actuation comprising the steps of: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.