Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
  • B81B7/008—MEMS characterised by an electronic circuit specially adapted for controlling or driving the same
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
  • G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
  • G01C19/567—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using the phase shift of a vibration node or antinode
  • G01C19/5677—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using the phase shift of a vibration node or antinode of essentially two-dimensional [2D] vibrators, e.g. ring-shaped vibrators
  • G01C19/5684—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using the phase shift of a vibration node or antinode of essentially two-dimensional [2D] vibrators, e.g. ring-shaped vibrators the devices involving a micromechanical structure
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
  • G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Definitions

• the invention relates to sensors. More specifically but not exclusively it relates to sensors such as inertial sensors, for example accelerometers and gyroscopes, in which resonant frequency of a microelectromechanical system (MEMS) sensor must be matched with allied control electronics.
• MEMS microelectromechanical system
• Angular velocity sensors incorporating a MEMS sensor of a resonator ring type are known and such examples can be seen in, for example, GB2322196.
• a vibrating planar ring or hoop-like structure is disclosed.
• the ring-like structure is suspended in space by a suitable support mount for detecting turning rate, linear acceleration and angular acceleration.
• Turning rate is sensed by detecting vibrations coupled by Coriolis forces, whereas linear acceleration and angular acceleration are sensed by lateral, vertical and rocking movement of the entire ring or hoop-like structure within its mount.
• the MEMS resonator is driven into resonance by a suitable driver signal generated by control electronics.
• control electronics it is necessary for the frequency of the control electronics to be matched, with a suitable tolerance, to the resonant frequency of the MEMS resonator.
• an inertial sensor comprising an element having a resonant frequency, the element being driven to resonance by suitable driver means, the sensor further comprising electronic control means including an oscillator capable of oscillation at variable frequencies in which the sensor further comprises comparator means for comparing the frequency of the output of the element with the frequency of the oscillator and locking the frequency of the oscillator once a predetermined frequency is achieved.
• Figure 1 is a schematic drawing showing one form of circuit suitable for matching the frequency of an oscillator to the resonant frequency of a MEMS type ring sensor.
• a MEMS resonator 1 is driven by a suitable drive signal into resonance.
• the drive signal is generated by suitable drive means 2 under the control of suitable control electronics 3, including an oscillator.
• suitable control electronics 3 including an oscillator.
• the output signal of the MEMS resonator 1 is input in to a threshold detector 4 and to the control electronics 3.
• the control electronics 3 oscillator On application of power (or release of applied reset signal) to the system, the control electronics 3 oscillator is forced to a frequency that is always less than the MEMS resonator frequency (taking into account all the relevant tolerances of MEMS and control electronics). The control electronics 3 then forces the oscillator frequency to ramp at a suitable speed while monitoring the amplitude of the MEMS transducer signals. When the frequency of the MEMS resonance is reached an increase in the MEMS transducer signals is detected and the control electronics stops the ramp of the oscillator frequency and switches to PLL (phase lock loop) mode.
• PLL phase lock loop
• the frequency of the oscillator is now suitably close to the MEMS resonator frequency to allow the system to lock to the MEMS in a short period of time.
• the circuit detects the dc level after demodulation and looks for a certain threshold. When the threshold is reached the system latches to PLL mode. The PLL loop then pulls the system into the final correct resonant frequency.
• a peak detector may be used in place of the threshold detector but is not specifically required for the embodiment described above. Additionally, the point of detecting the pickoff signal due to reaching the resonant frequency can be implemented at various points (i.e. before the demod).
• the invention may be applied to any suitable form of sensor.
• it can be applied to any form of sensor where there is a requirement to lock to a resonant frequency using a PLL type loop.
• the diagram shown in Figure 1 is simplified for ease of disclosure.
• the comparator is a threshold detector. The level detected is after channel amplification and demodulation to a dc level.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Computer Hardware Design (AREA)
• Gyroscopes (AREA)
• Micromachines (AREA)
• Pressure Sensors (AREA)
• Oscillators With Electromechanical Resonators (AREA)
• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
• Measurement Of Resistance Or Impedance (AREA)

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Citations (2)

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• 2010
  • 2010-04-08 GB GBGB1005875.8A patent/GB201005875D0/en not_active Ceased
• 2011
  • 2011-04-05 JP JP2013503087A patent/JP2013527920A/ja active Pending
  • 2011-04-05 WO PCT/EP2011/055285 patent/WO2011124576A1/en not_active Ceased
  • 2011-04-05 KR KR1020127029198A patent/KR20130040877A/ko not_active Ceased
  • 2011-04-05 EP EP11711946.1A patent/EP2556334B1/en active Active
  • 2011-04-05 CN CN201180018073.8A patent/CN103097860B/zh active Active
  • 2011-04-05 US US13/639,703 patent/US9162875B2/en active Active

Patent Citations (2)

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