Abstract: An angular velocity sensor or gyroscope has a ring and a primary drive transducer arranged to cause the ring to oscillate in a primary mode substantially at the resonant frequency of the primary mode of the ring. A primary control loop receives primary pick-off signals from the primary pick-off transducer and provides primary drive signals to the primary drive transducer so as to maintain resonant oscillation of the ring. The primary control loop includes a demodulator arranged to determine the amplitude of the fundamental frequency of the primary pick-off signals and a demodulator arranged to determine the amplitude of the second harmonic frequency of the primary pick-off signals and a drive signal generator arranged to produce the primary drive signals with an amplitude that is dependent on a ratio of the amplitude of the second harmonic frequency of the primary pick-off signal over the amplitude of the fundamental frequency of the primary pick-off signal as derived by a divider.

Abstract: A gyroscope structure 41 includes ring structure 42 supported from a central hub 43 by eight compliant support legs 44a to 44h. Primary drive transducers 45a and 45b and secondary drive transducers 46a and 46b are all located around and in spaced relationship with the external periphery of the ring structure 42 to create capacitive gaps and primary pick-off transducers 47a and 47b and secondary pick-off transducers 48a and 48b are all located around and in spaced relationship with the internal periphery of the ring structure 42 to create capacitive gaps. The gyroscope structure 41 includes sixteen capacitor plates 49a to 49p in spaced relationship to the ring structure 42 to create capacitive gaps. Two groups of capacitive plates 49a to 49d and 49i to 49l are all located around the internal periphery of the ring structure 42 and two groups of capacitor plates 49e to 49h and 49m to 49p are all located around the external periphery of the ring structure 42.

Abstract: A gyroscope structure 41 includes ring structure 42 supported from a central hub 43 by eight compliant support legs 44a to 44h. Primary drive transducers 45a and 45b and secondary drive transducers 46a and 46b are all located around and in spaced relationship with the external periphery of the ring structure 42 to create capacitive gaps and primary pick-off transducers 47a and 47b and secondary pick-off transducers 48a and 48b are all located around and in spaced relationship with the internal periphery of the ring structure 42 to create capacitive gaps. The gyroscope structure 41 includes sixteen capacitor plates 49a to 49p in spaced relationship to the ring structure 42 to create capacitive gaps. Two groups of capacitive plates 49a to 49d and 49i to 49l are all located around the internal periphery of the ring structure 42 and two groups of capacitor plates 49e to 49h and 49m to 49p are all located around the external periphery of the ring structure 42.

Abstract: An angular velocity sensor or gyroscope has a ring and a primary drive transducer arranged to cause the ring to oscillate in a primary mode substantially at the resonant frequency of the primary mode of the ring. A primary control loop receives primary pick-off signals from the primary pick-off transducer and provides primary drive signals to the primary drive transducer so as to maintain resonant oscillation of the ring. The primary control loop includes a demodulator arranged to determine the amplitude of the fundamental frequency of the primary pick-off signals and a demodulator arranged to determine the amplitude of the second harmonic frequency of the primary pick-off signals and a drive signal generator arranged to produce the primary drive signals 116 with amplitude that is dependent on a ratio of the amplitude of the second harmonic frequency of the primary pick-off signal over the amplitude of the fundamental frequency of the primary pick-off signal as derived by a divider.

Abstract: A method for reducing bias error in a Vibrating Structure Gyroscope having a vibrating structure, a primary drive for putting the vibrating structure into carrier mode resonance, a primary pick-off device for sensing carrier mode motion, a secondary pick-off for sensing response mode vibration of the vibrating structure in response to applied rotation rate, a secondary drive for applying a force to control the response mode motion, closed loop primary control loops for maintaining a fixed amplitude of motion at the primary pick-off device, for maintaining the drive frequency at the resonance maximum, and secondary control loops for maintaining a null at the secondary pick-off device.

Abstract: Bias error is reduced in a vibrating structure sensor having primary and secondary pick-offs separated by a fixed angular amount (45°) with respect to the vibrating structure by summing a proportion of the primary pick-off output signal into the secondary pick-off output signal or subtracting a proportion of the primary pick-off output signal from the secondary pick-off output signal effectively to reduce or increase the angular separation of the secondary pick-off from the primary driver by an amount sufficient to set the rate output signal from the vibrating structure to zero and thereby minimize bias error.

Abstract: A vibration damper assembly for a ring resonator of a vibrating structure gyroscope has a female portion attachable to a body of the gyroscope so as to have limited resiliency with respect to the body in a direction substantially perpendicular to the body. A male portion is fixedly attachable at one end to a resonator of the gyroscope, projectable into the female portion and fixedly attachable at its other end in and to the female portion. The assembly permits damping of vibratory movement of the resonator in a direction substantially perpendicular thereto whilst retaining stiffness and freedom to vibrate for the resonator in the plane thereof.

Abstract: A vibrating structure gyroscope has a vibratory resonator having a substantially ring or hoop-like shape structure, an electromagnetic drive for causing the resonator to vibrate, a support structure including a plurality of flexible support beams for supporting the resonator whilst allowing it to vibrate and an electromagnetic sensor for sensing movement of the resonator. The support beams and resonator are made from silicon and the electromagnetic drive and sensor include metal tracks which extend externally along each support beam onto and along respective segments of an outer substantially planar surface of the ring-like resonator. The resonator is substantially planar and means is produced a magnetic field substantially perpendicular to the plane of the resonator.

Abstract: A rate sensor for sensing applied rate on at least two axes is provided. A vibrating structure is vibrated in a Cos 2.theta. carrier mode at a Cos 2.theta. carrier mode frequency such that rotation about one or the other of the two axes will generate a Coriolis force sufficient to cause a rocking motion and rocking mode vibration of the vibrating structure about the same axis out of the plane of the vibrating structure at the Cos 2.theta. carrier mode frequency. The vibrating structure has a substantially planar, substantially ring or hoop-like form that is shaped and dimensioned to match the frequencies of the Cos 2.theta. carrier mode and the rocking mode vibration in the vibrating structure to give a resonant amplification of the rocking motion. The rocking mode vibration is proportional to the applied rate. The rocking mode vibration is detected to determine the applied rate.