Vibratory gyroscope
A sensing device comprising a micromechanical gyroscope, the gyroscope comprising an improved sensing device with a micromechanical gyroscope, where the resonance frequency of the first mechanical resonator and the resonance frequency of the second mechanical resonator are adjusted to essentially coincide. The device comprises a feed-back loop connected to the second mechanical resonator, the quality factor of the combination of the feed-back loop and the second mechanical resonator being less than 10. More accurate sensing is achieved without essentially adding complexity to the sensor device configuration.
1. A sensing device comprising a micromechanical gyroscope, the gyroscope comprising:
a first mechanical resonator for drive mode vibration;
a second mechanical resonator coupled to the first mechanical resonator for sense mode vibration corresponding to an angular velocity, wherein a resonance frequency of the first mechanical resonator and a resonance frequency of the second mechanical resonator are initially set to essentially coincide; and
a damping feed-back loop connected to the second mechanical resonator for damping the sense mode vibration of the second mechanical resonator, the damping feed-back loop comprising a signal processing filter that has a resonant frequency characteristic that coincides with the resonance frequency of the second mechanical resonator, wherein a sign of the signal processing filter is selected such that a phase shift of the damping feed-back loop is either 0 or −π, and an electrical Q value, which is an electrical quality factor, of the signal processing filter is in a range between 3 to 10.
2. A sensing device according to claim 1 , wherein the initial frequency separation between the resonance frequency of the first mechanical resonator and the resonance frequency of the second mechanical resonator is in the range of 0 to 0.05.
3. A sensing device according to claim 1 , wherein the resonance frequencies of the first and second mechanical resonators are designed to behave similarly over changes in environment.
4. A sensing device according to claim 1 , wherein the second mechanical resonator comprises a first transducer and a second transducer, wherein the first transducer and the second transducer are area modulated type of capacitive or electric transducers.
5. A sensing device according to claim 4 , wherein deviation of the resonant frequency characteristic from the resonance frequency of the first mechanical resonator is less than 50%.
6. A sensing device according to claim 1 , wherein the second mechanical resonator comprises a first transducer and a second transducer, wherein the first transducer and the second transducer are piezoelectric transducers.
7. A sensing device according to claim 1 , wherein a loop gain of the damping feed-back loop for frequencies below the resonant frequency of the first mechanical resonator is in the range 0.1 to 0.3.
8. A method of manufacturing a sensing device comprising a micromechanical gyroscope, the gyroscope comprising a first mechanical resonator for drive mode vibration and a second mechanical resonator coupled to the first mechanical resonator for sense mode vibration corresponding to an angular velocity, the method comprising:
initially setting a resonance frequency of the first mechanical resonator and a resonance frequency of the second mechanical resonator to essentially coincide; and
connecting a damping feed-back loop to the second mechanical resonator, the damping feed-back loop comprising a signal processing filter that has a resonant frequency characteristic at the resonance frequency of the second mechanical resonator, wherein a sign of the signal processing filter is selected such that a phase shift of the damping feed-back loop is either 0 or −π, and an electrical Q value, which is an electrical quality factor, of the signal processing filter is in a range between 3 to 10.