In order to measure three-axis intersection error, two crosshair targets were fixed in the inner axis frame of a three-axis turntable. Also a theodolite was used to point its telescope to the targets and to measure th...In order to measure three-axis intersection error, two crosshair targets were fixed in the inner axis frame of a three-axis turntable. Also a theodolite was used to point its telescope to the targets and to measure the horizontal angles when three axes were on equi-spaced angle positions. The calculation equations of the axis intersection were deduced from the mounting position of the theodolite, positions of two targets, angular positions of three axes, and the measured horizontal angles with the theodolite. Finally, a practical measurement is carried out on a horizontal three-axis turntable and error analysis is conducted.展开更多
In order to meet tracking performance index of three-axis hydraulic simulator, based on classical quantitative feedback theory （QFT）, an improved QFT technique is used to synthesize controller of low gain and bandwi...In order to meet tracking performance index of three-axis hydraulic simulator, based on classical quantitative feedback theory （QFT）, an improved QFT technique is used to synthesize controller of low gain and bandwidth. By choosing a special nominal plant, the improved method assigns relative magnitude and phase tracking error between system uncertainty and nominal control plant. Relative tracking error induced by system uncertainty is transformed into sensitivity problem and relative tracking error induced by nominal plant forms into a region on Nichols chart. The two constraints further form into a combined bound which is fit for magnitude and phase loop shaping. Because of leaving out pre-filter of classical QFT controller structure, tracking performance is enhanced greatly. Furthermore, a cascaded two-loop control strategy is proposed to heighten control effect. The improved technique＇s efficacy is validated by simulation and experiment results.展开更多
The dynamic errors of gyros are the important error sources of a strapdown inertial navigation system. In order to identify the dynamic error model coefficients accurately, the static error model coefficients which la...The dynamic errors of gyros are the important error sources of a strapdown inertial navigation system. In order to identify the dynamic error model coefficients accurately, the static error model coefficients which lay a foundation for compensating while identifying the dynamic error model are identified in the gravity acceleration fields by using angular position function of the three-axis turntable. The angular acceleration and angular velocity are excited on the input, output and spin axis of the gyros when the outer axis and the middle axis of a three-axis turntable are in the uniform angular velocity state simultaneously, while the inner axis of the turntable is in different static angular positions. 8 groups of data are sampled when the inner axis is in 8 different angular positions. These data are the function of the middle axis positions and the inner axis positions. For these data, harmonic analysis method is applied two times versus the middle axis positions and inner axis positions respectively so that the dynamic error model coefficients are finally identified through the least square method. In the meantime the optimal angular velocity of the outer axis and the middle axis are selected by computing the determination value of the information matrix.展开更多
This paper presents a new nine⁃degree⁃of⁃freedom parallel mechanism,which can be applied as a flight simulator.The mechanism is composed by Stewart turntable and another three⁃axis turntable.The Stewart platform can r...This paper presents a new nine⁃degree⁃of⁃freedom parallel mechanism,which can be applied as a flight simulator.The mechanism is composed by Stewart turntable and another three⁃axis turntable.The Stewart platform can realize six⁃degree⁃of⁃freedom movement in space,but the working space is limited.After the three⁃axis turntable is installed,the rotation space can be increased to simulate more realistic flight conditions.This paper analyzes the new flight simulator from kinematics and dynamics aspects.In addition,the flight simulator is simulated and analyzed based on the MATLAB/Simulink simulation system.The results obtained from the numerical simulations is planned to be used for the practical manufacturing and applications of the new platform.展开更多
以实际应用为背景,针对当前对三轴转台的需求,设计了虚拟三轴转台,并结合相关软件、硬件进行实现。在Adams和Matlab/Simulink软件中分别构建了三轴转台的运动学模型和控制模型,并通过联合仿真技术实现了模型的联合运动。在此基础上,基于...以实际应用为背景,针对当前对三轴转台的需求,设计了虚拟三轴转台,并结合相关软件、硬件进行实现。在Adams和Matlab/Simulink软件中分别构建了三轴转台的运动学模型和控制模型,并通过联合仿真技术实现了模型的联合运动。在此基础上,基于Simulink RTW和x PC Real-time Target实时仿真平台,配合ARINC429信号仿真板卡和信号调理装置,实现了虚拟三轴转台系统设计,得到虚拟三轴转台的运动特性。展开更多
This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stif...This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.展开更多
Purpose–The three-axis simulator relies on the air film between the air bearing and the bearing seat to achieve weightlessness and the frictionless motion condition,which is essential for simulating the micro-disturb...Purpose–The three-axis simulator relies on the air film between the air bearing and the bearing seat to achieve weightlessness and the frictionless motion condition,which is essential for simulating the micro-disturbance torque of a satellite in outer space.However,at the beginning of the experiment,the disturbance torque caused by the misalignment between the center of gravity of the simulator and the center of rotation of the bearing is the most important factor restricting the use of the space three-axis simulator.In order to solve this problem,it is necessary to set the balance adjustment system on the simulator to compensate the disturbance torque caused by the eccentricity.The paper aims to discuss these issues.Design/methodology/approach–In this paper,a study of L1 adaptive automatic balancing control method for micro satellite with motor without other actuators is proposed.L1 adaptive control algorithm adds the low-pass filter to the control law,which in a certain sense to reduce the high-frequency signal and speed up the response time of the controlled system.At the same time,by estimating the adaptive parameter uncertainty in object,the output error of the state predictor and the controlled object can be stabilized under Lyapunov condition,and the robustness of the system is also improved.The automatic balancing method of PID is also studied in this paper.Findings–Through this automatic balancing mechanism,the gravity disturbance torque can be effectively reduced down to 10−6 Nm,and the automatic balancing time can be controlled within 7 s.Originality/value–This paper introduces an automatic balancing mechanism.The experimental results show that the mechanism can greatly improve the convergence speed while guaranteeing the control accuracy,and ensuring the feasibility of the large angle maneuver of spacecraft three-axis simulator.展开更多
文摘In order to measure three-axis intersection error, two crosshair targets were fixed in the inner axis frame of a three-axis turntable. Also a theodolite was used to point its telescope to the targets and to measure the horizontal angles when three axes were on equi-spaced angle positions. The calculation equations of the axis intersection were deduced from the mounting position of the theodolite, positions of two targets, angular positions of three axes, and the measured horizontal angles with the theodolite. Finally, a practical measurement is carried out on a horizontal three-axis turntable and error analysis is conducted.
文摘In order to meet tracking performance index of three-axis hydraulic simulator, based on classical quantitative feedback theory （QFT）, an improved QFT technique is used to synthesize controller of low gain and bandwidth. By choosing a special nominal plant, the improved method assigns relative magnitude and phase tracking error between system uncertainty and nominal control plant. Relative tracking error induced by system uncertainty is transformed into sensitivity problem and relative tracking error induced by nominal plant forms into a region on Nichols chart. The two constraints further form into a combined bound which is fit for magnitude and phase loop shaping. Because of leaving out pre-filter of classical QFT controller structure, tracking performance is enhanced greatly. Furthermore, a cascaded two-loop control strategy is proposed to heighten control effect. The improved technique＇s efficacy is validated by simulation and experiment results.
文摘The dynamic errors of gyros are the important error sources of a strapdown inertial navigation system. In order to identify the dynamic error model coefficients accurately, the static error model coefficients which lay a foundation for compensating while identifying the dynamic error model are identified in the gravity acceleration fields by using angular position function of the three-axis turntable. The angular acceleration and angular velocity are excited on the input, output and spin axis of the gyros when the outer axis and the middle axis of a three-axis turntable are in the uniform angular velocity state simultaneously, while the inner axis of the turntable is in different static angular positions. 8 groups of data are sampled when the inner axis is in 8 different angular positions. These data are the function of the middle axis positions and the inner axis positions. For these data, harmonic analysis method is applied two times versus the middle axis positions and inner axis positions respectively so that the dynamic error model coefficients are finally identified through the least square method. In the meantime the optimal angular velocity of the outer axis and the middle axis are selected by computing the determination value of the information matrix.
文摘This paper presents a new nine⁃degree⁃of⁃freedom parallel mechanism,which can be applied as a flight simulator.The mechanism is composed by Stewart turntable and another three⁃axis turntable.The Stewart platform can realize six⁃degree⁃of⁃freedom movement in space,but the working space is limited.After the three⁃axis turntable is installed,the rotation space can be increased to simulate more realistic flight conditions.This paper analyzes the new flight simulator from kinematics and dynamics aspects.In addition,the flight simulator is simulated and analyzed based on the MATLAB/Simulink simulation system.The results obtained from the numerical simulations is planned to be used for the practical manufacturing and applications of the new platform.
文摘以实际应用为背景,针对当前对三轴转台的需求,设计了虚拟三轴转台,并结合相关软件、硬件进行实现。在Adams和Matlab/Simulink软件中分别构建了三轴转台的运动学模型和控制模型,并通过联合仿真技术实现了模型的联合运动。在此基础上,基于Simulink RTW和x PC Real-time Target实时仿真平台,配合ARINC429信号仿真板卡和信号调理装置,实现了虚拟三轴转台系统设计,得到虚拟三轴转台的运动特性。
文摘This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.
基金This work was partially supported by the National Natural Science Foundation of China(Nos 61673208,61374115)the National Key Research and Development Plan(No.2016YFB0500901).
文摘Purpose–The three-axis simulator relies on the air film between the air bearing and the bearing seat to achieve weightlessness and the frictionless motion condition,which is essential for simulating the micro-disturbance torque of a satellite in outer space.However,at the beginning of the experiment,the disturbance torque caused by the misalignment between the center of gravity of the simulator and the center of rotation of the bearing is the most important factor restricting the use of the space three-axis simulator.In order to solve this problem,it is necessary to set the balance adjustment system on the simulator to compensate the disturbance torque caused by the eccentricity.The paper aims to discuss these issues.Design/methodology/approach–In this paper,a study of L1 adaptive automatic balancing control method for micro satellite with motor without other actuators is proposed.L1 adaptive control algorithm adds the low-pass filter to the control law,which in a certain sense to reduce the high-frequency signal and speed up the response time of the controlled system.At the same time,by estimating the adaptive parameter uncertainty in object,the output error of the state predictor and the controlled object can be stabilized under Lyapunov condition,and the robustness of the system is also improved.The automatic balancing method of PID is also studied in this paper.Findings–Through this automatic balancing mechanism,the gravity disturbance torque can be effectively reduced down to 10−6 Nm,and the automatic balancing time can be controlled within 7 s.Originality/value–This paper introduces an automatic balancing mechanism.The experimental results show that the mechanism can greatly improve the convergence speed while guaranteeing the control accuracy,and ensuring the feasibility of the large angle maneuver of spacecraft three-axis simulator.
