This paper presents a low-cost remote vision system for use in unmanned aircraft that provide a first person view （FPV） to vehicle operators in real-time. The system does not require a traditional electromechanical ...This paper presents a low-cost remote vision system for use in unmanned aircraft that provide a first person view （FPV） to vehicle operators in real-time. The system does not require a traditional electromechanical gimbal setup. Instead, the system uses a wide-angle （fisheye） lens and a video camera setup that is fixed on the vehicle and captures the full viewing area as seen from the cockpit in each video frame. Video is transmitted to a ground station wirelessly. On the ground, the pilot is outfitted with virtual reality goggles with integrated attitude and heading sensors. The received video is recertified and cropped by the ground station to provide the goggles with the appropriate view based on head orientation. Compared to traditional electromechanical setups, the presented system features reduced weight, reduced video lag, lower power consumption, and reduced drag on the airborne vehicle in addition to requiring only a unidirectional downlink. The video processing is preformed on the ground, further reducing computational resources and bandwidth requirements. These advantages, in conjunction with the advancement in miniature optical sensors and lenses, make the proposed approach a viable option for miniature remotely controlled vehicles. The system was successfully implemented and tested using an R/C airplane.展开更多
To satisfy the validation requirements of flight control law for advanced aircraft,a wind tunnel based virtual flight testing has been implemented in a low speed wind tunnel.A 3-degree-offreedom gimbal,ventrally insta...To satisfy the validation requirements of flight control law for advanced aircraft,a wind tunnel based virtual flight testing has been implemented in a low speed wind tunnel.A 3-degree-offreedom gimbal,ventrally installed in the model,was used in conjunction with an actively controlled dynamically similar model of aircraft,which was equipped with the inertial measurement unit,attitude and heading reference system,embedded computer and servo-actuators.The model,which could be rotated around its center of gravity freely by the aerodynamic moments,together with the flow field,operator and real time control system made up the closed-loop testing circuit.The model is statically unstable in longitudinal direction,and it can fly stably in wind tunnel with the function of control augmentation of the flight control laws.The experimental results indicate that the model responds well to the operator＇s instructions.The response of the model in the tests shows reasonable agreement with the simulation results.The difference of response of angle of attack is less than 0.5°.The effect of stability augmentation and attitude control law was validated in the test,meanwhile the feasibility of virtual flight test technique treated as preliminary evaluation tool for advanced flight vehicle configuration research was also verified.展开更多
Based on the singular value decomposition theory,this paper analyzed the mechanism of escaping/avoiding singularity using generalized and weighted singularity-robust steering laws for a spacecraft that uses single gim...Based on the singular value decomposition theory,this paper analyzed the mechanism of escaping/avoiding singularity using generalized and weighted singularity-robust steering laws for a spacecraft that uses single gimbal control moment gyros （SGCMGs） as the actuator for the attitude control system.The expression of output-torque error is given at the point of singularity,proving the incompatible relationship between the gimbal rate and the output-torque error.The method of establishing a balance between the gimbal rate and the output-torque error is discussed,and a new steering law is designed.Simulation results show that the proposed steering law can effectively drive SGCMGs to escape away from singularities.展开更多
This article presents a novel method to measure unbalanced moments in a two-axis gimbaled seeker commonly believed to seviously influence the tracking accuracy and stabilizing capability.This method enables individual...This article presents a novel method to measure unbalanced moments in a two-axis gimbaled seeker commonly believed to seviously influence the tracking accuracy and stabilizing capability.This method enables individual measurement of unbalanced moments,and judgment of the seeker's status-balanced or not.Furthermore,an instrument is designed based on this method and calibrated.The effectiveness of the proposed method is validated through a simulation.The experimental results show a satisfied level of accuracy the measurements have.This work forms a basis for the further development of a more stabilized gimbaled seeker with less induced vibration and consumed power.展开更多
Attitude control system is one of the most important subsystems in a spacecraft.As a key actuator,the control moment gyroscope(CMG)mainly determines the performance of attitude control system.Whereas,the control accur...Attitude control system is one of the most important subsystems in a spacecraft.As a key actuator,the control moment gyroscope(CMG)mainly determines the performance of attitude control system.Whereas,the control accuracy and output torque smoothness of the CMG depends more on its gimbal servo system.Considering the constraints of size,mass and power consumption for a small satellite,here,a mini-CMG is designed,in which the gimbal servo system is driven by an ultrasonic motor.The good performances of the CMG are obtained by both the ultrasonic motor and the rotary inductosyn.The direct drive of gimbal improves its dynamic performance,with the output bandwidth above 20 Hz.The angular and speed closed-loop control obtains the 0.02°/s gimbal rate,and the output torque resolution better than 2×10^(-3) N·m.The ultrasonic motor provides 1.0N·m self-lock torque during power-off,with 12arc-second position accuracy.展开更多
In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave co...In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave compensation system,the lifting pipe simulator,the buffer simulator and the water pool.The tests ofmining ship motion simulator show that it is able to perform under the predetermined attitude path smoothly and can meet the requirements of themining ship motions.The heave compensation effect is more than 60% under random wave and the goal is set to be 50%.The model test results indicate that this heave compensation system is effective and feasible.展开更多
Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dy...Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.展开更多
In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is proposed.Then a rapid sing...In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is proposed.Then a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary,and quickly escape elliptic singularities.Finally,simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.展开更多
An improved constrained(IC)steering law for single gimbal control moment gyros(SGCMGs)with deformed pyramid configuration(DPC)is proposed,First of all,the original system with five pyramid configuration(FPC)whose two ...An improved constrained(IC)steering law for single gimbal control moment gyros(SGCMGs)with deformed pyramid configuration(DPC)is proposed,First of all,the original system with five pyramid configuration(FPC)whose two adjacent gyros are in failure state is reconfigured as a degraded system with DPC.Then,the singular angular momentum hypersurfaces of the original and the degraded systems are plotted via the singular angular momentum equa-tion of SGCMGs.Based on singular surfaces,the differences between FPC and DPC in singularity and momentum envelope are obtained directly,which provide an important reference for steering law design of DPC.Finally,an IC steering law is designed and applied to DPC.The simulation results demonstrate that the IC steering law has advantages in simplicity of calculation,avoidance of singularity and exactness of output torque,which endow the degraded system with fine controllability in a restricted workspace.展开更多
The steering laws of single gimbal control moment gyros （SGCMGs） are analyzed and compared in this paper for a spacecraft attitude control system based on singular value decomposition （SVD） theory. The mechanism o...The steering laws of single gimbal control moment gyros （SGCMGs） are analyzed and compared in this paper for a spacecraft attitude control system based on singular value decomposition （SVD） theory. The mechanism of steering laws escaping singularity, especially how the steering laws affect singularity of gimbal configuration and the output torque error, is studied using SVD theory. Performance of various steering laws are analyzed and compared quantitatively by simulation. The obtained results can be used as a reference for designers.展开更多
The application of the guided missile seeker is to provide stability to the sensor’s line of sight toward a target by isolating it from the missile motion and vibration.The main objective of this paper is not only to...The application of the guided missile seeker is to provide stability to the sensor’s line of sight toward a target by isolating it from the missile motion and vibration.The main objective of this paper is not only to present the physical modeling of two axes gimbal system but also to improve its performance through using fuzzy logic controlling approach.The paper is started by deriving the mathematical model for gimbals motion using Newton’s second law,followed by designing the mechanical parts of model using SOLIDWORKS and converted to xml file to connect dc motors and sensors using MATLAB/SimMechanics.Then,a Mamdani-type fuzzy and a Proportional-Integral-Derivative(PID)controllers were designed using MATLAB software.The performance of both controllers was evaluated and tested for different types of input shapes.The simulation results showed that self-tuning fuzzy controller provides better performance,since no overshoot,small steady-state error and small settling time compared to PID controller.展开更多
Ensuring food security has become a global challenge owing to climate change and population growth.High-throughput phenotyping can effectively drive crop genetic enhancement,which can potentially solve food crisis.Phe...Ensuring food security has become a global challenge owing to climate change and population growth.High-throughput phenotyping can effectively drive crop genetic enhancement,which can potentially solve food crisis.Phenotyping robot is an essential part of crop ground phenotyping information monitoring,although there are challenges such as the inability to adjust the fixed track width,poor load capacity of the detection robotic arm,and inability to fuse information in real-time.This study reports a phenotyping robot with a gantry-style chassis featuring an adjustable wheeltrack(1400-1600 mm)to adapt to different row spacing arrangements and reduced damage,and function effectively in both dry field and paddy field environments.A six-degree-of-freedom sensor gimbal with high payload capacity is also developed to enable precise height(1016-2096 mm)and angle ad-justments.Additionally,this study introduces an enhanced method for data acquisition from multiple imaging sensors through registration and fusion using Zhang's calibration and feature point extraction algorithm,calcu-lating a homography matrix for high-throughput data collection at fixed positions and heights.The experimental validation results demonstrate that the RMSE of the registration algorithm does not exceed 3 pixels.The gimbal data strongly correlated with that of a handheld instrument data(r^(2)>0.90).The robot is practical,reliable,and fully functional,offering a solid theoretical foundation and equipment support for high-throughput phenotyping.展开更多
A new attitude control method for solar sails is proposed using a single-axis gimbal mechanism and three-axis reaction wheels.The gimbal angle is varied to change the geometrical relationship between the force due to ...A new attitude control method for solar sails is proposed using a single-axis gimbal mechanism and three-axis reaction wheels.The gimbal angle is varied to change the geometrical relationship between the force due to solar radiation pressure(SRP)and the center of mass of the spacecraft,such that the disturbance torque is minimized during attitude maintenance for orbit control.Attitude maneuver and maintenance are performed by the reaction wheels based on the quaternion feedback control method.Even if angular momentum accumulates on the reaction wheels due to modelling error,it can also be unloaded by using the gimbal to produce suitable torque due to SRP.In this study,we analyzed the attitude motion under the reaction wheel control by linearizing the equations of motion around the equilibrium point.Further,we newly derived the propellent-free unloading method based on the analytical formulation.Finally,we constructed the integrated attitude–orbit control method,and its validity was verified in integrated attitude–orbit control simulations.展开更多
Autonomous underwater vehicles are at present being used for scientific,commercial and military submerged applications.In this paper,a system has been proposed which can be used underwater as remotely operated underwa...Autonomous underwater vehicles are at present being used for scientific,commercial and military submerged applications.In this paper,a system has been proposed which can be used underwater as remotely operated underwater vehicle for submerged survey for different purposes.These systems require self-sufficient direction and control frameworks so as to perform submerged assignments.Displaying,framework identification and control of these vehicles are as yet real dynamic zones of innovative work.This theory is worried about the plan and improvement of an Autonomous Underwater Vehicle(AUV)specifically proposed for passage into global submerged vehicle rivalries.The theory comprises of two stages;the first includes the plan and development of the vehicle while the subsequent stage is worried about the demonstrating and framework identification of the vehicle,just as the reproduction of a control system.The structure and advancement of the vehicle comprised of actualizing a mechanical and electrical framework,just as the reconciliation of subsystems.The framework identification of the vehicle parameters comprised of utilizing locally available sensors to perform static and dynamic tests.Least squares estimation was utilized to gauge the parameters from the pre-researched data obtained.展开更多
文摘This paper presents a low-cost remote vision system for use in unmanned aircraft that provide a first person view （FPV） to vehicle operators in real-time. The system does not require a traditional electromechanical gimbal setup. Instead, the system uses a wide-angle （fisheye） lens and a video camera setup that is fixed on the vehicle and captures the full viewing area as seen from the cockpit in each video frame. Video is transmitted to a ground station wirelessly. On the ground, the pilot is outfitted with virtual reality goggles with integrated attitude and heading sensors. The received video is recertified and cropped by the ground station to provide the goggles with the appropriate view based on head orientation. Compared to traditional electromechanical setups, the presented system features reduced weight, reduced video lag, lower power consumption, and reduced drag on the airborne vehicle in addition to requiring only a unidirectional downlink. The video processing is preformed on the ground, further reducing computational resources and bandwidth requirements. These advantages, in conjunction with the advancement in miniature optical sensors and lenses, make the proposed approach a viable option for miniature remotely controlled vehicles. The system was successfully implemented and tested using an R/C airplane.
基金supported by the National Key Basic Research Program of China(No.2015CB755800)
文摘To satisfy the validation requirements of flight control law for advanced aircraft,a wind tunnel based virtual flight testing has been implemented in a low speed wind tunnel.A 3-degree-offreedom gimbal,ventrally installed in the model,was used in conjunction with an actively controlled dynamically similar model of aircraft,which was equipped with the inertial measurement unit,attitude and heading reference system,embedded computer and servo-actuators.The model,which could be rotated around its center of gravity freely by the aerodynamic moments,together with the flow field,operator and real time control system made up the closed-loop testing circuit.The model is statically unstable in longitudinal direction,and it can fly stably in wind tunnel with the function of control augmentation of the flight control laws.The experimental results indicate that the model responds well to the operator＇s instructions.The response of the model in the tests shows reasonable agreement with the simulation results.The difference of response of angle of attack is less than 0.5°.The effect of stability augmentation and attitude control law was validated in the test,meanwhile the feasibility of virtual flight test technique treated as preliminary evaluation tool for advanced flight vehicle configuration research was also verified.
基金supported by the National Natural Science Foundation of China (10872029)the Excellent Young Scholars Research Fund of the Beijing Institute of Technology (2007YS0202)
文摘Based on the singular value decomposition theory,this paper analyzed the mechanism of escaping/avoiding singularity using generalized and weighted singularity-robust steering laws for a spacecraft that uses single gimbal control moment gyros （SGCMGs） as the actuator for the attitude control system.The expression of output-torque error is given at the point of singularity,proving the incompatible relationship between the gimbal rate and the output-torque error.The method of establishing a balance between the gimbal rate and the output-torque error is discussed,and a new steering law is designed.Simulation results show that the proposed steering law can effectively drive SGCMGs to escape away from singularities.
文摘This article presents a novel method to measure unbalanced moments in a two-axis gimbaled seeker commonly believed to seviously influence the tracking accuracy and stabilizing capability.This method enables individual measurement of unbalanced moments,and judgment of the seeker's status-balanced or not.Furthermore,an instrument is designed based on this method and calibrated.The effectiveness of the proposed method is validated through a simulation.The experimental results show a satisfied level of accuracy the measurements have.This work forms a basis for the further development of a more stabilized gimbaled seeker with less induced vibration and consumed power.
基金supported by the National Natural Science Foundation of China(No.51575260)the Fundamental Research Funds for the Central Universities(No.NJ20160001)
文摘Attitude control system is one of the most important subsystems in a spacecraft.As a key actuator,the control moment gyroscope(CMG)mainly determines the performance of attitude control system.Whereas,the control accuracy and output torque smoothness of the CMG depends more on its gimbal servo system.Considering the constraints of size,mass and power consumption for a small satellite,here,a mini-CMG is designed,in which the gimbal servo system is driven by an ultrasonic motor.The good performances of the CMG are obtained by both the ultrasonic motor and the rotary inductosyn.The direct drive of gimbal improves its dynamic performance,with the output bandwidth above 20 Hz.The angular and speed closed-loop control obtains the 0.02°/s gimbal rate,and the output torque resolution better than 2×10^(-3) N·m.The ultrasonic motor provides 1.0N·m self-lock torque during power-off,with 12arc-second position accuracy.
基金Project(50675226) supported by the National Natural Science Foundation of China Project(DYXM-115-04-02-01) supported by the Eleventh Five-Year Plan of China
文摘In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave compensation system,the lifting pipe simulator,the buffer simulator and the water pool.The tests ofmining ship motion simulator show that it is able to perform under the predetermined attitude path smoothly and can meet the requirements of themining ship motions.The heave compensation effect is more than 60% under random wave and the goal is set to be 50%.The model test results indicate that this heave compensation system is effective and feasible.
文摘Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.
基金funded under the National Natural Science Foundation of China(No.61873312)。
文摘In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is proposed.Then a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary,and quickly escape elliptic singularities.Finally,simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.
基金supported by the National Natural Science Foundation of China(10372011)
文摘An improved constrained(IC)steering law for single gimbal control moment gyros(SGCMGs)with deformed pyramid configuration(DPC)is proposed,First of all,the original system with five pyramid configuration(FPC)whose two adjacent gyros are in failure state is reconfigured as a degraded system with DPC.Then,the singular angular momentum hypersurfaces of the original and the degraded systems are plotted via the singular angular momentum equa-tion of SGCMGs.Based on singular surfaces,the differences between FPC and DPC in singularity and momentum envelope are obtained directly,which provide an important reference for steering law design of DPC.Finally,an IC steering law is designed and applied to DPC.The simulation results demonstrate that the IC steering law has advantages in simplicity of calculation,avoidance of singularity and exactness of output torque,which endow the degraded system with fine controllability in a restricted workspace.
基金the National Natural Science Foundation of China(No.10502006)the ExcellentScholars Fund of Beijing(No.20071D1600300398)the Excellent Young Scholars Research Fundof Beijing Institute of Technology(No.2007YS0202)
文摘The steering laws of single gimbal control moment gyros （SGCMGs） are analyzed and compared in this paper for a spacecraft attitude control system based on singular value decomposition （SVD） theory. The mechanism of steering laws escaping singularity, especially how the steering laws affect singularity of gimbal configuration and the output torque error, is studied using SVD theory. Performance of various steering laws are analyzed and compared quantitatively by simulation. The obtained results can be used as a reference for designers.
基金Taif University Researchers Supporting Project number(TURSP-2020/260),Taif University,Taif,Saudi Arabia.
文摘The application of the guided missile seeker is to provide stability to the sensor’s line of sight toward a target by isolating it from the missile motion and vibration.The main objective of this paper is not only to present the physical modeling of two axes gimbal system but also to improve its performance through using fuzzy logic controlling approach.The paper is started by deriving the mathematical model for gimbals motion using Newton’s second law,followed by designing the mechanical parts of model using SOLIDWORKS and converted to xml file to connect dc motors and sensors using MATLAB/SimMechanics.Then,a Mamdani-type fuzzy and a Proportional-Integral-Derivative(PID)controllers were designed using MATLAB software.The performance of both controllers was evaluated and tested for different types of input shapes.The simulation results showed that self-tuning fuzzy controller provides better performance,since no overshoot,small steady-state error and small settling time compared to PID controller.
基金The work was supported by the National Key Research and Development Program of China(Grant No.2021YFD2000101).
文摘Ensuring food security has become a global challenge owing to climate change and population growth.High-throughput phenotyping can effectively drive crop genetic enhancement,which can potentially solve food crisis.Phenotyping robot is an essential part of crop ground phenotyping information monitoring,although there are challenges such as the inability to adjust the fixed track width,poor load capacity of the detection robotic arm,and inability to fuse information in real-time.This study reports a phenotyping robot with a gantry-style chassis featuring an adjustable wheeltrack(1400-1600 mm)to adapt to different row spacing arrangements and reduced damage,and function effectively in both dry field and paddy field environments.A six-degree-of-freedom sensor gimbal with high payload capacity is also developed to enable precise height(1016-2096 mm)and angle ad-justments.Additionally,this study introduces an enhanced method for data acquisition from multiple imaging sensors through registration and fusion using Zhang's calibration and feature point extraction algorithm,calcu-lating a homography matrix for high-throughput data collection at fixed positions and heights.The experimental validation results demonstrate that the RMSE of the registration algorithm does not exceed 3 pixels.The gimbal data strongly correlated with that of a handheld instrument data(r^(2)>0.90).The robot is practical,reliable,and fully functional,offering a solid theoretical foundation and equipment support for high-throughput phenotyping.
基金supported by the Japan Society for the Promotion of Science,KAKENHI Grant Numbers JP21K14345 and JP21H04588.
文摘A new attitude control method for solar sails is proposed using a single-axis gimbal mechanism and three-axis reaction wheels.The gimbal angle is varied to change the geometrical relationship between the force due to solar radiation pressure(SRP)and the center of mass of the spacecraft,such that the disturbance torque is minimized during attitude maintenance for orbit control.Attitude maneuver and maintenance are performed by the reaction wheels based on the quaternion feedback control method.Even if angular momentum accumulates on the reaction wheels due to modelling error,it can also be unloaded by using the gimbal to produce suitable torque due to SRP.In this study,we analyzed the attitude motion under the reaction wheel control by linearizing the equations of motion around the equilibrium point.Further,we newly derived the propellent-free unloading method based on the analytical formulation.Finally,we constructed the integrated attitude–orbit control method,and its validity was verified in integrated attitude–orbit control simulations.
文摘Autonomous underwater vehicles are at present being used for scientific,commercial and military submerged applications.In this paper,a system has been proposed which can be used underwater as remotely operated underwater vehicle for submerged survey for different purposes.These systems require self-sufficient direction and control frameworks so as to perform submerged assignments.Displaying,framework identification and control of these vehicles are as yet real dynamic zones of innovative work.This theory is worried about the plan and improvement of an Autonomous Underwater Vehicle(AUV)specifically proposed for passage into global submerged vehicle rivalries.The theory comprises of two stages;the first includes the plan and development of the vehicle while the subsequent stage is worried about the demonstrating and framework identification of the vehicle,just as the reproduction of a control system.The structure and advancement of the vehicle comprised of actualizing a mechanical and electrical framework,just as the reconciliation of subsystems.The framework identification of the vehicle parameters comprised of utilizing locally available sensors to perform static and dynamic tests.Least squares estimation was utilized to gauge the parameters from the pre-researched data obtained.
