Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement,including spectroscopy,metrology,precision distance measurement,sensing,as well as optical and microwav...Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement,including spectroscopy,metrology,precision distance measurement,sensing,as well as optical and microwave waveform synthesis,signal processing,and communications.Several techniques exist to generate optical frequency combs,such as mode-locked lasers,Kerr micro-resonators,and electro-optic modulation.Important characteristics of optical frequency combs include the number of comb lines,their spacing,spectral shape and/or flatness,and intensity noise.While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation,the latter provides increased flexibility in tuning the comb spacing.For some applications in optical communications and microwave photonics,a high degree of integration may be more desirable over a very large number of comb lines.In this paper,we review recent progress on integrated electro-optic frequency comb generators,including those based on indium phosphide,lithium niobate,and silicon photonics.展开更多
An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferom...An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide has been designed, which is capable of detecting seismic acceleration in high-accuracy seismic exploration. The Mach-Zehnder interferometer was successfully fabricated and a lighting test used to check its quality. The frequency response characteristic of the accelerometer was measured2 The accelerometer with a resonant frequency of 3549 Hz was demonstrated to show good linear frequency responding characteristics in the range of 100-3000 Hz. The accelerometer also shows good stability and consistency. Experimental results indicate that the outputs of the on- and cross-axis are 147 and 21.3 mV, respectively.展开更多
Novel thin films consisting of optical materials such as lithium niobate and barium titanate enable various high-performance integrated photonic devices.However,the nanofabrication of these devices requires high-quali...Novel thin films consisting of optical materials such as lithium niobate and barium titanate enable various high-performance integrated photonic devices.However,the nanofabrication of these devices requires high-quality etching of these thin films,necessitating the long-term development of the fabrication recipe and specialized equipment.Here we present a strong-confinement low-index-rib-loaded waveguide structure as the building block of various passive and active integrated photonic devices based on novel thin films.By optimizing this low-index-rib-loaded waveguide structure without etching the novel thin film,we can simultaneously realize strong optical power confinement in the thin film,low optical propagation loss,and strong electro-optic coupling for the fundamental transverse electric mode.Based on our low-index-rib-loaded waveguide structure,we designed and fabricated a thin film lithium niobate(TFLN)modulator,featuring a 3-dB modulation bandwidth over 110 GHz and a voltage-length product as low as 2.26 V·cm,which is comparable to those of the state-of-the-art etched TFLN modulators.By alleviating the etching of novel thin films,the proposed structure opens up new ways of fast proof-of-concept demonstration and even mass production of high-performance integrated electro-optic and nonlinear devices based on novel thin films.展开更多
We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded...We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.展开更多
In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system ...In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit （MIMU）. It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi- physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle （MAV）.展开更多
Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume...Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.展开更多
A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating...A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed.First,the numbers of diffraction orders are calculated.Then,structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode.Finally,we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm,crater of 451 nm by an FIB/SEM dual beam system.Based on the ANSYS simulation,a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of±1 G,corresponding to zeroth diffraction beam optical sensitivity 1%/mG.The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication.These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.展开更多
High performance electro-optic modulator,as the key device of integrated ultra-wideband optical systems,have be-come the focus of research.Meanwhile,the organic-based hybrid electro-optic modulators,which make full us...High performance electro-optic modulator,as the key device of integrated ultra-wideband optical systems,have be-come the focus of research.Meanwhile,the organic-based hybrid electro-optic modulators,which make full use of the advant-ages of organic electro-optic(OEO)materials(e.g.high electro-optic coefficient,fast response speed,high bandwidth,easy pro-cessing/integration and low cost)have attracted considerable attention.In this paper,we introduce a series of high-perform-ance OEO materials that exhibit good properties in electro-optic activity and thermal stability.In addition,the recent progress of organic-based hybrid electro-optic devices is reviewed,including photonic crystal-organic hybrid(PCOH),silicon-organic hy-brid(SOH)and plasmonic-organic hybrid(POH)modulators.A high-performance integrated optical platform based on OEO ma-terials is a promising solution for growing high speeds and low power consumption in compact sizes.展开更多
In order to realize a high accuracy seismic exploration in the high electro-magnetic field and to improve oil producibility and recovery efficiency,a three-component photoelastic waveguide accelerometer is designed. B...In order to realize a high accuracy seismic exploration in the high electro-magnetic field and to improve oil producibility and recovery efficiency,a three-component photoelastic waveguide accelerometer is designed. Based on the photoelastic effect,the Mach-Zehnder integrated optical interferometer is designed to measure the three-orthogonal components of acceleration and the combined three-component simple harmonic vibrator is designed to reduce the cross-talk among the acceleration components. According to the variation of LiNbO3 waveguide phase under the action of the applied acceleration,the cross-axise sensitivity and transverse sensitivity ratio(TSR) were analysed. The results reveal that the accelerometer has wide band and good linearity. It can satisfy the sensor requirements of high accuracy seismic exploration. The main design parameters of the geophone system are:phase sensitivity:1.86×10-4 Rad·m-1·s-2,natural frequency:3 500 Hz,and the transverse sensitivity ratio:0.11%.展开更多
The integrated strap-down inertial nav igation system/olelestial navigation system(SINS/CNS)i an important autonomous navigation method with efective concealment and high predision.Both accelerometer biss and star ens...The integrated strap-down inertial nav igation system/olelestial navigation system(SINS/CNS)i an important autonomous navigation method with efective concealment and high predision.Both accelerometer biss and star ensor installation error ame important factors that aflect the performanoe of this mavigation system,which needl to be calibratexd and compensatedl.A new acelerometer bias and star sensor installation error joint calibration method for the SINS/CNS integrated navigation system i propoeed.In this newly propoeed method,the installation error of star sensor is augmented to the state vector,and the star vector,nadir angle,horkzontal poeition error and velbcity error ame ueed a8 measurementa to calbrate the two errors mentioned above.Simulations show that both accelerometer bias and star sensor installation enror an be calibratedl efectively.展开更多
An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to com...An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to compose three Wheatstone bridges that are sensitive to the only given orientation. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, crossaxis-coupling degree, and linearity are presented. The sensitivity of X, Y and Z were 5.49 mV/g, 5.12 mV/g and 4.82 mV/g, respectively; the nonlinearity of X, Y and Z were 0.01%, 0.04% and 0.01%, respectively; the crossaxis-coupling factor of X axis to Y axis and Z axis are 0.119% and 2.26%; the cross-axis-coupling factor of Y axis to X axis and Z axis are 0.157% and 4.12%; the cross-axis-coupling factor of Z axis to X axis and Y axis are 0.511% and 0.938%. The measured performance indexes attain accurate vector-detection in practical applications, and even at a navigation level. In conclusion, the accelerometer is a highly integrated sensor.展开更多
研究基于PI滤波估计加速度漂移的X射线脉冲星敏感器与加表组合导航算法。因长时间惯导误差积累导致发散,X射线脉冲星敏感器不能实时定位,且不能确定速度,提出利用X射线脉冲星敏感器脉冲到达时间(Time of arrival,TOA)作为观测量,与惯导...研究基于PI滤波估计加速度漂移的X射线脉冲星敏感器与加表组合导航算法。因长时间惯导误差积累导致发散,X射线脉冲星敏感器不能实时定位,且不能确定速度,提出利用X射线脉冲星敏感器脉冲到达时间(Time of arrival,TOA)作为观测量,与惯导推算的航天器位置在脉冲星指向上的投影估计位置误差,基于PI滤波估计加速度漂移,修正惯导误差,通过组合导航连续确定位置/速度。仿真表明,基于X射线脉冲星敏感器相位ϕ与加表组合天文导航算法能有效估计加速度漂移,并给出较高精度的位置/速度。展开更多
基金This research was supported in part by the Natural Sciences and Engineering Research Council of Canada and the Fonds du Québec–Nature et Technologies.
文摘Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement,including spectroscopy,metrology,precision distance measurement,sensing,as well as optical and microwave waveform synthesis,signal processing,and communications.Several techniques exist to generate optical frequency combs,such as mode-locked lasers,Kerr micro-resonators,and electro-optic modulation.Important characteristics of optical frequency combs include the number of comb lines,their spacing,spectral shape and/or flatness,and intensity noise.While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation,the latter provides increased flexibility in tuning the comb spacing.For some applications in optical communications and microwave photonics,a high degree of integration may be more desirable over a very large number of comb lines.In this paper,we review recent progress on integrated electro-optic frequency comb generators,including those based on indium phosphide,lithium niobate,and silicon photonics.
基金supported by the National Natural Science Foundation of China (No. 40774067)the Applied Basic Research Program of Sichuan Province, China (No. 07JY029-135)
文摘An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide has been designed, which is capable of detecting seismic acceleration in high-accuracy seismic exploration. The Mach-Zehnder interferometer was successfully fabricated and a lighting test used to check its quality. The frequency response characteristic of the accelerometer was measured2 The accelerometer with a resonant frequency of 3549 Hz was demonstrated to show good linear frequency responding characteristics in the range of 100-3000 Hz. The accelerometer also shows good stability and consistency. Experimental results indicate that the outputs of the on- and cross-axis are 147 and 21.3 mV, respectively.
基金financial supports from National Key Research and Development Program of China (2021YFA1401000)National Natural Science Foundation of China (62435009)+2 种基金Beijing Municipal Natural Science Foundation (Z220008)Zhuhai Industry University Research Collaboration Project (ZH-2201700121010)supported by the Center of High Performance Computing,Tsinghua University
文摘Novel thin films consisting of optical materials such as lithium niobate and barium titanate enable various high-performance integrated photonic devices.However,the nanofabrication of these devices requires high-quality etching of these thin films,necessitating the long-term development of the fabrication recipe and specialized equipment.Here we present a strong-confinement low-index-rib-loaded waveguide structure as the building block of various passive and active integrated photonic devices based on novel thin films.By optimizing this low-index-rib-loaded waveguide structure without etching the novel thin film,we can simultaneously realize strong optical power confinement in the thin film,low optical propagation loss,and strong electro-optic coupling for the fundamental transverse electric mode.Based on our low-index-rib-loaded waveguide structure,we designed and fabricated a thin film lithium niobate(TFLN)modulator,featuring a 3-dB modulation bandwidth over 110 GHz and a voltage-length product as low as 2.26 V·cm,which is comparable to those of the state-of-the-art etched TFLN modulators.By alleviating the etching of novel thin films,the proposed structure opens up new ways of fast proof-of-concept demonstration and even mass production of high-performance integrated electro-optic and nonlinear devices based on novel thin films.
文摘We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.
基金the Astronautic Technology Foundation (HTZC0405)
文摘In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit （MIMU）. It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi- physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle （MAV）.
基金supports from National Natural Science Foundation of China(No.62004166)Fundamental Research Funds for the Central Universities(No.31020190QD027)+2 种基金Natural Science Basic Research Program of Shaanxi(Program No.2020JQ-199)China National Postdoctoral Program for Innovative Talents(No.BX20200279)Key Research and Development Program of Shaanxi Province(2020GXLH-Z-027,2020ZDLGY04-08).
文摘Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.
基金Supported by the National Natural Science Foundation of China under Grant No 60908016.
文摘A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed.First,the numbers of diffraction orders are calculated.Then,structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode.Finally,we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm,crater of 451 nm by an FIB/SEM dual beam system.Based on the ANSYS simulation,a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of±1 G,corresponding to zeroth diffraction beam optical sensitivity 1%/mG.The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication.These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.
基金the National Natural Science Foundation of China(No.62175267)the Beijing Municipal Natural Science Foundation(No.4192061)+1 种基金the Fundamental Research Funds for the Central Universities(2020MDJC13)the Beijing Talents Foundation(2018000021223ZK45)for the financial support.
文摘High performance electro-optic modulator,as the key device of integrated ultra-wideband optical systems,have be-come the focus of research.Meanwhile,the organic-based hybrid electro-optic modulators,which make full use of the advant-ages of organic electro-optic(OEO)materials(e.g.high electro-optic coefficient,fast response speed,high bandwidth,easy pro-cessing/integration and low cost)have attracted considerable attention.In this paper,we introduce a series of high-perform-ance OEO materials that exhibit good properties in electro-optic activity and thermal stability.In addition,the recent progress of organic-based hybrid electro-optic devices is reviewed,including photonic crystal-organic hybrid(PCOH),silicon-organic hy-brid(SOH)and plasmonic-organic hybrid(POH)modulators.A high-performance integrated optical platform based on OEO ma-terials is a promising solution for growing high speeds and low power consumption in compact sizes.
基金The National Natural Science Foundation of China(40774067)The Program of International Cooperation and Exchange in National Natural Science Foundation of China(40811240167)The Program of the Key Science and Technology of Sichuan(07JY029-135)
文摘In order to realize a high accuracy seismic exploration in the high electro-magnetic field and to improve oil producibility and recovery efficiency,a three-component photoelastic waveguide accelerometer is designed. Based on the photoelastic effect,the Mach-Zehnder integrated optical interferometer is designed to measure the three-orthogonal components of acceleration and the combined three-component simple harmonic vibrator is designed to reduce the cross-talk among the acceleration components. According to the variation of LiNbO3 waveguide phase under the action of the applied acceleration,the cross-axise sensitivity and transverse sensitivity ratio(TSR) were analysed. The results reveal that the accelerometer has wide band and good linearity. It can satisfy the sensor requirements of high accuracy seismic exploration. The main design parameters of the geophone system are:phase sensitivity:1.86×10-4 Rad·m-1·s-2,natural frequency:3 500 Hz,and the transverse sensitivity ratio:0.11%.
文摘The integrated strap-down inertial nav igation system/olelestial navigation system(SINS/CNS)i an important autonomous navigation method with efective concealment and high predision.Both accelerometer biss and star ensor installation error ame important factors that aflect the performanoe of this mavigation system,which needl to be calibratexd and compensatedl.A new acelerometer bias and star sensor installation error joint calibration method for the SINS/CNS integrated navigation system i propoeed.In this newly propoeed method,the installation error of star sensor is augmented to the state vector,and the star vector,nadir angle,horkzontal poeition error and velbcity error ame ueed a8 measurementa to calbrate the two errors mentioned above.Simulations show that both accelerometer bias and star sensor installation enror an be calibratedl efectively.
基金supported by the National Science and Technology Cooperation Program of China(No.61011140351)
文摘An integrated MEMS accelerometer has been designed and fabricated. The device, which is based on the piezoresistive effect, accomplishes the detection of three components of acceleration by using piezoresistors to compose three Wheatstone bridges that are sensitive to the only given orientation. The fabrication of the accelerometer is described, and the theory behind its operation developed. Experimental results on sensitivity, crossaxis-coupling degree, and linearity are presented. The sensitivity of X, Y and Z were 5.49 mV/g, 5.12 mV/g and 4.82 mV/g, respectively; the nonlinearity of X, Y and Z were 0.01%, 0.04% and 0.01%, respectively; the crossaxis-coupling factor of X axis to Y axis and Z axis are 0.119% and 2.26%; the cross-axis-coupling factor of Y axis to X axis and Z axis are 0.157% and 4.12%; the cross-axis-coupling factor of Z axis to X axis and Y axis are 0.511% and 0.938%. The measured performance indexes attain accurate vector-detection in practical applications, and even at a navigation level. In conclusion, the accelerometer is a highly integrated sensor.
文摘研究基于PI滤波估计加速度漂移的X射线脉冲星敏感器与加表组合导航算法。因长时间惯导误差积累导致发散,X射线脉冲星敏感器不能实时定位,且不能确定速度,提出利用X射线脉冲星敏感器脉冲到达时间(Time of arrival,TOA)作为观测量,与惯导推算的航天器位置在脉冲星指向上的投影估计位置误差,基于PI滤波估计加速度漂移,修正惯导误差,通过组合导航连续确定位置/速度。仿真表明,基于X射线脉冲星敏感器相位ϕ与加表组合天文导航算法能有效估计加速度漂移,并给出较高精度的位置/速度。
