Classifications

• • 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 present invention relates, in general, to technology for electrical feedback control for improving the sensor performance of typical gyroscopes, and, more particularly, to a system for implementing force rebalance control using an automatic gain control loop suitable for the design of small-sized and low power systems, such as Micro- Electro-Mechanical System (MEMS) gyroscopes.
• MEMS Micro- Electro-Mechanical System
• a gyroscope is a measurement sensor for measuring angular velocity, which is an inertial physical quantity existing in a rotating coordinate system, and representative examples thereof include a mechanical gyroscope and an optical gyroscope for detecting the difference between the traveling paths of light in a tachometer.
• micro-gyroscopes using MEMS technology are currently being manufactured, and various application fields for use of the micro-gyroscopes have been proposed.
• vehicle fields such as vehicle attitude control, rollover detection, vehicle navigation, accident recording, collision avoidance, load leveling, and suspension control
• consumer electronics fields such as computer input devices, game controllers, virtual reality input tools, sports utility sensors, camcorders, and household robots
• industrial electronics fields such as self-controlled traveling, guide robots, oil hydraulic equipment, and attitude control
• small-sized flying object system fields such as aerial electronics, antenna direction angle control, unmanned aerial vehicles, and light aircraft automatic landing devices.
• a rate-grade or tactical-grade gyroscope for angular velocity measurement used in typical control has been manufactured in the form of a micro-gyroscope using a semiconductor manufacturing process.
• a gyroscope having a micro-gyroscope form has characteristics such as small size, low power consumption, and mass production due to the manufacturing process thereof.
• a vibratory gyroscope is characterized in that it employs a scheme for detecting
• the gyroscope can calculate the magnitude of an input angular velocity proportional to the Coriolis force by detecting a displacement signal induced by the Coriolis force.
• FIG. 1 is a diagram showing an example of the operating principles of a typical gyroscope.
• a mass body 10 vibrates according to dynamics in an X axis direction, causes Coriolis force, which is twice the angular velocity of the mass body, depending on an input angular velocity applied along a Z axis, and detects a displacement signal along a Y-axis, thus calculating the input angular velocity.
• the vibration amplitudes of driving displacement and detection displacement are determined using the modulus of elasticity of a driving axis spring 30 and a sensing axis spring 40, which support the mass body between the mass body and the framework 20 of the gyroscope.
• an open-loop detection method is disadvantageous in that the dynamic range of a sensor may be limited, non- linearity between input and output may be amplified, and bandwidth is greatly limited in an environment such as a vacuum, in which high frequency selectivity is required, but such a disadvantage can be overcome by applying a closed-loop type force rebalance control method of maintaining the displacement signal of a sensor in a uniformly balanced state.
• an object of the present invention is to provide a system and method for performing the force rebalance feedback control of a vibratory gyroscope by utilizing an automatic gain control loop that controls the velocity signal of a mass body.
• the present invention provides a force rebalance control system using an automatic gain control loop, comprising a gyroscope for detecting a displacement signal of a mass body corresponding to an input angular velocity, and adjusting a displacement of the mass body; a charge amplifier for converting the displacement signal detected by the gyroscope into a voltage signal, and outputting the voltage signal; a differentiator for outputting a velocity signal of the mass body on a basis of the displacement signal, output from the charge amplifier as the voltage signal; a unity gain reference frequency output unit for outputting a sine wave signal having a phase, frequency, and unity gain identical to those of the velocity signal output from the differentiator; a reference value input unit for generating a reference signal required to induce vibration of a sensing axis having uniform intensity regardless of the angular velocity applied to the gyroscope; a controller for outputting a control signal, required for the gyroscope to vibrate with a predetermined
• the gyroscope may comprise a sensing axis output unit for detecting the displacement signal of the mass body corresponding to the input angular velocity; and a sensing axis driving unit for adjusting the displacement of the mass body.
• the unity gain reference frequency output unit may comprise a gain unit for amplifying an input signal by a high gain factor; a limiter for outputting a square wave signal having a same phase as the input signal; and a band pass filter having a center frequency corresponding to a resonant frequency of the gyroscope.
• the force balance control system may further comprise a rectifier for half- wave rectifying the velocity signal output from the differentiator; and a low pass filter for outputting a signal half- wave rectified by the rectifier as an envelope signal.
• the controller may comprise an integral unit for performing an integration operation on the difference value between the envelope signal, output from the low pass filter, and the reference signal, generated by the reference value input unit; a proportional gain unit for multiplying a gain value by the difference value; and an integral gain unit for multiplying a gain value by the result of integration output from the integral unit.
• the present invention provides a force rebalance control method using an automatic gain control loop, comprising a first step of detecting a fine displacement of a sensing axis provided in a gyroscope; a second step of generating a velocity signal of a mass body on a basis of a displacement signal corresponding to the detected fine displacement; a third step of generating a sine wave signal having a phase, frequency, and unity gain identical to those of the velocity signal, and a control signal required for the gyroscope to vibrate with a predetermined amplitude; a fourth step of performing a multiplication operation on the sine wave signal and the control signal, thus generating an amplitude-modulated signal; and a fifth step of applying the amplitude-modulated signal to the gyroscope so as to maintain the displacement of the mass body at a uniform value.
• the first to fifth steps may be repeated when an angular velocity is input to the gyroscope after the fifth step.
• the force rebalance control method may further comprise the step of adjusting a resonant frequency to cause the sensing axis and a driving axis of the gyroscope to have a same resonant frequency when the sensing axis and the driving axis of the gyroscope do not have the same resonant frequency before the first step.
• the third step of generating the control signal comprises a first sub-step of detecting a high frequency envelope signal from the velocity signal; a second sub-step of generating a reference signal required to induce vibration of the sensing axis having uniform intensity regardless of the angular velocity applied to the gyroscope; and a third sub-step of generating a control signal required for the gyroscope to vibrate with a predetermined amplitude using both the envelope signal, detected at the first sub- step, and the reference signal.
• a conventional digital circuit which is complicated and sensitive to noise, can be implemented using a simple analog circuit, so that the present invention can be extended and applied to general-purpose vibratory gyroscopes or various sensor fields, such as those of an inertial sensor, a pressure sensor, and a temperature sensor, as well as micro-gyroscopes.
• a force rebalance control system using an automatic gain control loop according to the present invention is applied to various sensors, thus improving performance, such as the dynamic range, bandwidth, and linearity of the sensors.
• FIG. 1 is a diagram showing an example of the operating principles of a typical gyroscope
• FIG. 2 is a diagram showing the construction of a force rebalance control system using an automatic gain control loop according to the present invention
• FIG. 3 is a diagram showing the detailed construction of a unity gain reference frequency output unit according to the present invention.
• FIG. 4 is a diagram showing the detailed construction of a controller according to the present invention.
• FIG. 5 is a flowchart showing the operation of a force rebalance control system using an automatic gain control loop and the force rebalance control method according to the present invention
• FIG. 6 is a graph showing an input angular velocity versus control signal in a force rebalance control system using an automatic gain control loop according to the present invention
• FIG. 7 is a graph showing an input angular velocity versus angular velocity in a force rebalance control system using an automatic gain control loop according to the present invention.
• FIG. 8 is a graph showing the input signal and the output signal of angular velocity using a gyroscope applied to a force rebalance control system using an automatic gain control loop according to the present invention.
• FIG. 2 is a diagram conceptually showing a force rebalance control system 100
• the force rebalance system 100 includes a gyroscope 110, a charge amplifier 120, a differentiator 130, a unity gain reference frequency output unit 140, a rectifier 150, a low pass filter 160, a reference value input unit 170, a controller 180, and a multiplier 190.
• the gyroscope 110 includes a sensing axis output unit 111 for detecting the displacement signal of a mass body corresponding to an input angular velocity, and a sensing axis driving unit 112 for adjusting the displacement signal of the mass body on the basis of a gyroscope control signal calculated by the multiplier.
• the charge amplifier 120 functions to output the displacement signal, detected by the sensing axis output unit 111 as a voltage signal.
• the charge amplifier 120 is connected to the sensing axis output unit 111 and is configured to convert variation in the amount of charge corresponding to variation in the capacitance between the mass body and the electrode of the sensing axis output unit into a voltage signal and to output the voltage signal. Therefore, the voltage signal output from the charge amplifier 120 is detected as a function of the displacement signal proportional to the input angular velocity.
• the differentiator 130 functions to output the velocity signal of the mass body by differentiating the displacement signal, output from the charge amplifier 120, as the voltage signal.
• the velocity signal of the mass body, output from the differ- entiator 130 is applied to two independent feedback loops, that is, the unity gain reference frequency output unit 140 and the rectifier 150.
• the unity gain reference frequency output unit 140 functions to output a sine wave signal having a frequency, a phase and a unity gain identical to those of the velocity signal output from the differentiator 130.
• the unity gain reference output unit includes a gain unit 141 implemented with an amplifier, which uses an Operational Amplifier (OP- Amp), and configured to amplify an input signal by a high gain factor, a limiter 142 for outputting a square wave signal having the same phase as the input signal, and a band pass filter 143, having a center frequency corresponding to the resonant frequency of the gyroscope.
• OP- Amp Operational Amplifier
• the unity gain reference frequency output unit 140 can also generate a square wave having the same resonant frequency as the velocity signal of the mass body, having a relatively low Signal to Noise Ratio (SNR).
• the limiter 142 is set to a comparator that exploits an OP- Amp having a suitable slew rate, but is not limited to this comparator, and can be variously set to a Schmitt trigger or the like according to the intensity of a noise signal.
• the rectifier 150 functions to half- wave rectify the velocity signal output from the differentiator 130
• the low pass filter 160 functions to output the signal, half- wave rectified by the rectifier 150, as an envelope signal.
• the reference value input unit 170 functions to generate a reference signal for inducing the vibration of a sensing axis having uniform intensity, regardless of the angular velocity applied to the gyroscope.
• the controller 180 functions to output a control signal, required for the gyroscope to vibrate with a predetermined amplitude, using both the envelope signal output from the low pass filter 160 and the reference signal generated by the reference value input unit 170.
• FIG. 4 is a diagram conceptually showing the controller 180.
• the controller 180 includes an integral unit 181 for performing an integration operation on the difference value between the envelope signal, output from the low pass filter 160, and the reference signal, generated by the reference value input unit 170, and a proportional gain unit 182 and an integral gain unit 183 for multiplying respective gain values by the difference value and the result of integration.
• the multiplier 190 performs a multiplication operation on the sine wave signal, output from the unity gain reference frequency output unit 140, and the control signal, output from the controller 180, and applies the resulting voltage signal to the sensing axis driving unit 111 of the gyroscope 110.
• the voltage signal applied to the sensing axis driving unit is used to perform force rebalance feedback control to maintain the vibration amplitude of the mass body, varying with Coriolis force, at a uniform value.
• FIG. 2 is a diagram conceptually showing a force rebalance control system 100
• the force rebalance system 100 includes a gyroscope 110, a charge amplifier 120, a differentiator 130, a unity gain reference frequency output unit 140, a rectifier 150, a low pass filter 160, a reference value input unit 170, a controller 180, and a multiplier 190.
• the gyroscope 110 includes a sensing axis output unit 111 for detecting the displacement signal of a mass body corresponding to an input angular velocity, and a sensing axis driving unit 112 for adjusting the displacement signal of the mass body on the basis of a gyroscope control signal calculated by the multiplier.
• the charge amplifier 120 functions to output the displacement signal, detected by the sensing axis output unit 111 as a voltage signal.
• the charge amplifier 120 is connected to the sensing axis output unit 111 and is configured to convert variation in the amount of charge corresponding to variation in the capacitance between the mass body and the electrode of the sensing axis output unit into a voltage signal and to output the voltage signal. Therefore, the voltage signal output from the charge amplifier 120 is detected as a function of the displacement signal proportional to the input angular velocity.
• the differentiator 130 functions to output the velocity signal of the mass body by differentiating the displacement signal, output from the charge amplifier 120, as the voltage signal.
• the velocity signal of the mass body, output from the differentiator 130 is applied to two independent feedback loops, that is, the unity gain reference frequency output unit 140 and the rectifier 150.
• the unity gain reference frequency output unit 140 functions to output a sine wave signal having a frequency, a phase and a unity gain identical to those of the velocity signal output from the differentiator 130.
• the unity gain reference output unit includes a gain unit 141 implemented with an amplifier, which uses an Operational Amplifier (OP- Amp), and configured to amplify an input signal by a high gain factor, a limiter 142 for outputting a square wave signal having the same phase as the input signal, and a band pass filter 143, having a center frequency corresponding to the resonant frequency of the gyroscope.
• OP- Amp Operational Amplifier
• the unity gain reference frequency output unit 140 can also generate a square wave having the same resonant frequency as the velocity signal of the mass body, having a relatively low Signal to Noise Ratio (SNR).
• the limiter 142 is set to a comparator that exploits an OP- Amp having a suitable slew rate, but is not limited to this comparator, and can be variously set to a Schmitt trigger or the like according to the intensity of a noise signal.
• the rectifier 150 functions to half- wave rectify the velocity signal output from the differentiator 130
• the low pass filter 160 functions to output the signal, half- wave rectified by the rectifier 150, as an envelope signal.
• the reference value input unit 170 functions to generate a reference signal for inducing the vibration of a sensing axis having uniform intensity, regardless of the angular velocity applied to the gyroscope.
• the controller 180 functions to output a control signal, required for the gyroscope to vibrate with a predetermined amplitude, using both the envelope signal output from the low pass filter 160 and the reference signal generated by the reference value input unit 170.
• FIG. 4 is a diagram conceptually showing the controller 180.
• the controller 180 includes an integral unit 181 for performing an integration operation on the difference value between the envelope signal, output from the low pass filter 160, and the reference signal, generated by the reference value input unit 170, and a proportional gain unit 182 and an integral gain unit 183 for multiplying respective gain values by the difference value and the result of integration.
• the voltage value, obtained by multiplying a proportional gain by the difference between the envelope signal output from the low pass filter 160 and the reference signal, generated by the reference value input unit 170, is added to the voltage value, obtained by multiplying an integral gain by the result of integration.
• the multiplier 190 performs a multiplication operation on the sine wave signal, output from the unity gain reference frequency output unit 140, and the control signal, output from the controller 180, and applies the resulting voltage signal to the sensing axis driving unit 111 of the gyroscope 110.
• the voltage signal applied to the sensing axis driving unit is used to perform force rebalance feedback control to maintain the vibration amplitude of the mass body, varying with Coriolis force, at a uniform value.
• the velocity signal of the mass body is generated on the basis of the displacement signal corresponding to the detected fine displacement at step S30.
• This velocity signal is a differential signal obtained by differentiating the displacement signal.
• step S40 of generating a sine wave signal, having a phase, a frequency and a unity gain identical to those of the velocity signal, and the steps S51, S52 and S53 of generating the control signal, required for the gyroscope to vibrate with predetermined amplitude, are performed.
• a high frequency envelope signal is detected from the velocity signal at step S51. Further, a reference signal for inducing the vibration of the sensing axis, having uniform intensity, regardless of the angular velocity applied to the gyroscope, is generated simultaneously with the detection of the envelope signal at step S52.
• control signal required for the gyroscope to vibrate with uniform amplitude, is generated using both the detected envelope signal and the reference signal at step S53.
• the voltage signal applied to the sensing axis driving unit in this way is used to perform force rebalance feedback control for maintaining the vibration amplitude of the mass body, which varies with the Coriolis force at a uniform value.
• FIG. 6 is a graph showing an input angular velocity versus control signal
• FIG. 7 is a graph showing an input angular velocity versus angular velocity signal
• FIG. 8 is a graph showing the input signal and output signal of angular velocity using a gyroscope applied to the force rebalance control system according to the present invention, in which "a” denotes an input sinusoidal angular velocity signal of about lOOdeg/sec at IHz, and "a”' denotes an output signal corresponding to the input signal and shows that the same waveform is output even for the input angular velocity, without causing distortion.
• the present invention can be extended and applied to general- purpose vibratory gyroscopes or various sensors, such as those of an inertial sensor, a pressure sensor, and a temperature sensor, and can be utilized in various industrial fields in which sensors are used because the performance of sensors, such as the dynamic range, bandwidth, and linearity thereof, can be improved.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Gyroscopes (AREA)
• Control Of Amplification And Gain Control (AREA)

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• 2008
  • 2008-01-25 WO PCT/KR2008/000471 patent/WO2009093769A2/en not_active Ceased
  • 2008-01-25 EP EP08712196.8A patent/EP2235476A4/de not_active Withdrawn
  • 2008-01-25 JP JP2010508284A patent/JP2010534823A/ja active Pending

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