Angular rate sensor and method of improving output characteristic thereof
AssigneeDenso Corporation
InventorTakehiro Watarai
Life of this patent
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Abstract
A method of improving an output characteristic of an angular rate sensor including, for example, a fork oscillator and an improved structure of an angular rate sensor are provided. The improvement of the output characteristic is achieved by adjusting a physical structure of the oscillator to minimize unwanted vibrations of the oscillator or noises of a sensor output. The adjustment of the physical structure is achieved by trimming away an edge portion of the oscillator or a supporter for supporting the oscillator on a base.
Claims37
A method of adjusting an oscillation characteristic of an oscillator of an angular rate sensor, the oscillator having a given length and being shaped to have a plurality of longitudinal edges, the oscillator being excited by input of an excitation signal to oscillate in a first direction perpendicular to the length of the oscillator and, when the angular rate sensor undergoes an angular rate during excitation of the oscillator, oscillating in a second direction perpendicular to the length of the oscillator to provide an output indicative of the angular rate, comprising the steps of:
- applying to the oscillator an ac voltage having a resonant frequency, at which the oscillator resonates in the first direction, to oscillate the oscillator;
- monitoring an output signal of the oscillator during oscillation of the oscillator by application of the ac voltage;
- and
- adjusting the oscillation characteristic of the oscillator so as to decrease an amplitude of the monitored output signal of the oscillator to minimize undesired oscillations of the oscillator in the second direction when excited by the input of the excitation signal.
A method of adjusting an output characteristic of an angular rate sensor which includes a first oscillator having a given length, shaped to have a plurality of longitudinal edges, excitation means responsive to input of an excitation signal for exciting the first oscillator to oscillate in an excitation-axis direction perpendicular to a longitudinal center line of the first oscillator, and a second oscillator having a given length, shaped to have a plurality of longitudinal edges having pickup means for picking up oscillations of the second oscillator in a pickup-axis direction perpendicular to a longitudinal center line of the second oscillator, comprising the steps of:
- applying an ac voltage having a resonant frequency, at which the first oscillator resonates in the excitation-axis direction, to the excitation means to oscillate the oscillating portion of the first oscillator;
- monitoring an output of the pickup means during oscillation of the first oscillator by application of the ac voltage;
- and
- adjusting oscillation characteristics of the first and second oscillators so as to decrease an amplitude of the monitored output of the pickup means to minimize undesired oscillations of the second oscillator in the pickup-axis direction produced during oscillation of the first oscillator by the excitation means.
An angular rate sensor for determining an angular rate of rotation when the angular rate sensor experiences the rotation about a given axis, comprising:
- an oscillator made of a piezoelectric element including at least one pair of arms and a connecting portion connecting ends of the arms;
- a drive electrode formed on an outer wall of said oscillator, said drive electrode being responsive to input of an excitation signal to oscillate the arms of said oscillator in a first direction perpendicular to length of said oscillator;
- a pickup electrode formed on the outer wall of said oscillator, said pickup electrode electrically picking up oscillations of the arms in a second direction different form the first direction which indicate the angular rate acting on the angular rate sensor;
- and
- an uneven portion formed on a portion of said oscillator near a connection of the connecting portion and the arms for adjusting an oscillation characteristic of said oscillator.
A method of adjusting an oscillation characteristic of an oscillator of an angular rate sensor, the oscillator being made of a piezoelectric element shaped to have a plurality of longitudinal edges, including at least one pair of arms and a connecting portion connecting ends of the arms, the oscillator having disposed thereon an excitation electrode and a pickup electrode, the arms being excited by input of an excitation signal through the excitation electrode to oscillate in a first direction perpendicular to length of the arms and, when the angular rate sensor undergoes an angular rate during excitation of the arms, oscillating in a second direction different from the first direction to provide an output signal indicative of the angular rate through the pickup electrode, comprising the steps of:
- applying an ac voltage to the excitation electrode to oscillate the arms in the first direction;
- monitoring an output signal of the oscillator through the pickup electrode during oscillation of the arms by application of the ac voltage;
- and
- forming an uneven portion on a portion of said oscillator near a connection of the connecting portion and the arms so as to decrease an amplitude of the monitored output signal of the oscillator to minimize undesired oscillations of the oscillator in the second direction when excited by the input of the excitation signal.
An angular rate sensor for determining an angular rate of rotation when the angular rate sensor experiences the rotation about a given axis, comprising:
- an oscillator made of a piezoelectric element including at least one pair of arms and a connecting portion connecting ends of the arms, the arms being excited by input of an excitation signal to oscillate at a first frequency in a first direction perpendicular to length of the arms and, when the angular rate sensor undergoes an angular rate during excitation of the arms, oscillating at a second frequency in a second direction different from the first direction to provide a signal indicative of the angular rate;
- and
- a supporting member mounted on a base to hold a node portion of said oscillator, said supporting member having a narrower portion which is so shaped that a frequency difference between the first and second frequencies lies within a preselected range.
A manufacturing method of an angular rate sensor comprising the steps of:
- a preparing an oscillator made of a piezoelectric element, including at least one pair of arms and a connecting portion connecting ends of the arms, the arms being excited by input of an excitation signal to oscillate at a first frequency in a first direction perpendicular to length of the arms and, when the angular rate sensor undergoes an angular rate during excitation of the arms, oscillating at a second frequency in a second direction different from the first direction to provide an output signal indicative of the angular rate:
- installing said oscillator on a base through a supporting member, the supporting member having a narrower portion;
- applying an ac voltage to said oscillator to oscillate the arms in the first direction;
- monitoring an output signal from the oscillator during oscillation of the arms by application of the ac voltage to determine a frequency difference between the first and second frequencies;
- and
- changing torsional rigidity of the narrower portion of said supporting member so that the frequency difference determined in said monitoring step lies within a preselected range.
A method of adjusting an oscillation characteristic of an oscillator of an angular rate sensor, the oscillator being made of a piezoelectric element, including at least one pair of arms and a connecting portion connecting ends of the arms, the arms being excited by input of an excitation signal to oscillate at a first frequency in a first direction perpendicular to length of the arms and, when the angular rate sensor undergoes an angular rate during excitation of the oscillator, oscillating at a second frequency in a second direction different from the first direction to produce an output signal indicative of the angular rate, comprising the steps of:
- applying an ac voltage to the oscillator to oscillate the arms in the first direction;
- monitoring an output signal from the oscillator during oscillation of the arms by application of the ac voltage to determine a frequency difference between the first and second frequencies;
- and
- changing torsional rigidity of the narrower portion of said supporting member so that the frequency difference determined in said monitoring step lies within a preselected range.
Dependencies are inferred from the claim text.