Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.Howe...Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.However,two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect.Firstly,the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers.Secondly,the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately.These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation.Based on the digital signal sampling property,the square coefficients and cross-coupling coefficients of accelerometers are considered.Meanwhile,the asymmetry scale factors are considered in the I-F conversion unit.Thus,a nonlinear model of specific force measurement is established compared to the linear model.Based on the three-axis turntable,the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers.Considering the nonlinear combination,the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure.Besides,an efficient specific force calculation model is approximately derived to reduce the real-time computation cost.Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients.The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.展开更多
Astronaut's body mass is an essential factor of health monitoring in space.The latest mass measurement device for the International Space Station (ISS) has employed a linear acceleration method.The principle of th...Astronaut's body mass is an essential factor of health monitoring in space.The latest mass measurement device for the International Space Station (ISS) has employed a linear acceleration method.The principle of this method is that the device generates a constant pulling force,and the astronaut is accelerated on a parallelogram motion guide which rotates at a large radius to achieve a nearly linear trajectory.The acceleration is calculated by regression analysis of the displacement versus time trajectory and the body mass is calculated by using the formula m=F/a.However,in actual flight,the device is instable that the deviation between runs could be 6-7 kg.This paper considers the body non-rigidity as the major cause of error and instability and analyzes the effects of body non-rigidity from different aspects.Body non-rigidity makes the acceleration of the center of mass (C.M.) oscillate and fall behind the point where force is applied.Actual acceleration curves showed that the overall effect of body non-rigidity is an oscillation at about 7 Hz and a deviation of about 25%.To enhance body rigidity,better body restraints were introduced and a prototype based on linear acceleration method was built.Measurement experiment was carried out on ground on an air table.Three human subjects weighing 60-70 kg were measured.The average variance was 0.04 kg and the average measurement error was 0.4%.This study will provide reference for future development of China's own mass measurement device.展开更多
基金Project(61174002)supported by the National Natural Science Foundation of ChinaProject(200897)supported by the Foundation of National Excellent Doctoral Dissertation of PR China+1 种基金Project(NCET-10-0900)supported by the Program for New Century ExcellentTalents in University,ChinaProject(131061)supported by the Fok Ying Tung Education Foundation,China
文摘Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.However,two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect.Firstly,the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers.Secondly,the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately.These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation.Based on the digital signal sampling property,the square coefficients and cross-coupling coefficients of accelerometers are considered.Meanwhile,the asymmetry scale factors are considered in the I-F conversion unit.Thus,a nonlinear model of specific force measurement is established compared to the linear model.Based on the three-axis turntable,the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers.Considering the nonlinear combination,the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure.Besides,an efficient specific force calculation model is approximately derived to reduce the real-time computation cost.Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients.The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.
文摘Astronaut's body mass is an essential factor of health monitoring in space.The latest mass measurement device for the International Space Station (ISS) has employed a linear acceleration method.The principle of this method is that the device generates a constant pulling force,and the astronaut is accelerated on a parallelogram motion guide which rotates at a large radius to achieve a nearly linear trajectory.The acceleration is calculated by regression analysis of the displacement versus time trajectory and the body mass is calculated by using the formula m=F/a.However,in actual flight,the device is instable that the deviation between runs could be 6-7 kg.This paper considers the body non-rigidity as the major cause of error and instability and analyzes the effects of body non-rigidity from different aspects.Body non-rigidity makes the acceleration of the center of mass (C.M.) oscillate and fall behind the point where force is applied.Actual acceleration curves showed that the overall effect of body non-rigidity is an oscillation at about 7 Hz and a deviation of about 25%.To enhance body rigidity,better body restraints were introduced and a prototype based on linear acceleration method was built.Measurement experiment was carried out on ground on an air table.Three human subjects weighing 60-70 kg were measured.The average variance was 0.04 kg and the average measurement error was 0.4%.This study will provide reference for future development of China's own mass measurement device.
