Objective: The purpose of this study is to understand the current situation of knowledge, attitude, and practice of self-management in young patients with type 2 diabetes mellitus (T2DM) and to explore the relationshi...Objective: The purpose of this study is to understand the current situation of knowledge, attitude, and practice of self-management in young patients with type 2 diabetes mellitus (T2DM) and to explore the relationship between general conditions (personal, social, and environment, clinical factors) and their knowledge, attitude, and practices (KAP) of diabetes self-management, This aims to provide patients with high-quality nursing care management and services, as well as to provide relevant recommendations for effective self-management. Methods: This study is a descriptive correlational study that used the purposive sampling method to investigate 359 patients with T2DM aged 18-25 years in four designated tertiary hospitals in Shandong Province. Results: Knowledge of self-management was correlated with sex, age, education level, occupation and work situation, monthly household income, medical payment method, family and friend support, frequency of diabetes health education, and diabetes complications. The attitude subscale was correlated with sex, age, education level, work situation, and family and friend support. The practice subscale was associated with age, education level, work situation, family and friend support, frequency of diabetes health education, and HbA1c values. Conclusion: Young adults aged 18-25 with T2DM have positive attitudes towards diabetes self-management, but there are still deficiencies in knowledge acquisition and behavioral practice. The KAP of self-management of diabetes is influenced by personal factors such as sex, age, and education level, and socio-environmental factors such as family income and family or friends’ social support. Additionally, clinical factors such as complications and HbA1c values significantly impacted the patient’s disease self-management ability.展开更多
A multiple antenna GPS system integrated with MEMS-based INS is proposed by data fusion. The system is applied to attitude determination due to its high accuracy, the high output rate, low latency, quick initializatio...A multiple antenna GPS system integrated with MEMS-based INS is proposed by data fusion. The system is applied to attitude determination due to its high accuracy, the high output rate, low latency, quick initialization, and good robustness and redundancy. The mathematical method for realizing the system is given. The system can provide attitude and other navigation information even without GPS measurement for a period of time. Experimental results show that, under the condition of 200 Hz, the attitude, the position, the velocity, the acceleration, and the angular rate can achieve 0. 08°/s, 1.5 m, 0. 1 m/s, 0. 12 m/s^2 and 0. 1°/s.展开更多
Global Positioning System (GPS) /Inertial Navigation System (INS) integrated system is continuously gaining research interests in many positioning and navigation fields. Kalman filtering-based integrated algorithm...Global Positioning System (GPS) /Inertial Navigation System (INS) integrated system is continuously gaining research interests in many positioning and navigation fields. Kalman filtering-based integrated algorithm has some drawbacks on stability, computation load, robustness, and system observability performances. Based on neural network technology, a new GPS/INS integration filtering algorithm is studied for an integration scheme of the attitude determination GPS/INS integrated navigation system. Through some theoretic analysis, this algorithm not only has good estimation performance, but also has better robustness to the system model and noise than the traditional Kalman algorithm. To assess the performance of the proposed integrated model more deeply, some simulation is done to compare with the traditional Kalman filter model. The results indicate that the proposed model provides a significant improvement in some performance, such as accuracy, stability, robustness, and so on.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
As an important sensor in the navigation systems,star sensors and the gyro play important roles in spacecraft attitude determination system.Complex environmental factors are the main sources of error in attitude deter...As an important sensor in the navigation systems,star sensors and the gyro play important roles in spacecraft attitude determination system.Complex environmental factors are the main sources of error in attitude determination.The error influence of different benchmarks and the disintegration mode between the star sensor and the gyro is analyzed in theory.The integrated design of the star sensor and the gyro on the same benchmark can effectively avoid the error influence and improves the spacecraft attitude determination accuracy.Simulation results indicate that when the stars sensor optical axis vectors overlap the reference coordinate axis of the gyro in the same benchmark,the attitude determination accuracy improves.展开更多
GPS-based attitude system is an important research field, since it is a valuable technique for the attitude determination of platforms. There exist two classes approaches for attitude determination using the GPS. The ...GPS-based attitude system is an important research field, since it is a valuable technique for the attitude determination of platforms. There exist two classes approaches for attitude determination using the GPS. The one determines attitude via baseline estimates in two frames, the other one solves for attitude by incorporating the attitude parameters directly into the GPS measurements. However, comparisons between these two classes approaches have been unexplored. First of all, two algorithms are introduced in detail which on behalf of these two kinds of approaches. Then we present numerical simulations demonstrating the performance of our algorithms and provide a comparison evaluating.展开更多
In this paper,the Global Positioning System(GPS)interferometer provides the preliminarily computed quaternions,which are then employed as the measurement of the extended Kalman filter(EKF)for the attitude determinatio...In this paper,the Global Positioning System(GPS)interferometer provides the preliminarily computed quaternions,which are then employed as the measurement of the extended Kalman filter(EKF)for the attitude determination system.The estimated quaternion elements from the EKF output with noticeably improved precision can be converted to the Euler angles for navigation applications.The aim of the study is twofold.Firstly,the GPS-based computed quaternion vector is utilized to avoid the singularity problem.Secondly,the quaternion estimator based on the EKF is adopted to improve the estimation accuracy.Determination of the unknown baseline vector between the antennas sits at the heart of GPS-based attitude determination.Although utilization of the carrier phase observables enables the relative positioning to achieve centimeter level accuracy,however,the quaternion elements derived from the GPS interferometer are inherently noisy.This is due to the fact that the baseline vectors estimated by the least-squares method are based on the raw double-differenced measurements.Construction of the transformation matrix is accessible according to the estimate of baseline vectors and thereafter the computed quaternion elements can be derived.Using the Euler angle method,the process becomes meaningless when the angles are at 90where the singularity problem occurs.A good alternative is the quaternion approach,which possesses advantages over the equivalent Euler angle based transformation since they apply to all attitudes.Simulation results on the attitude estimation performance based on the proposed method will be presented and compared to the conventional method.The results presented in this paper elucidate the superiority of proposed algorithm.展开更多
The Global Positioning System(GPS)offers the interferometer for attitude determination by processing the carrier phase observables.By using carrier phase observables,the relative positioning is obtained in centimeter ...The Global Positioning System(GPS)offers the interferometer for attitude determination by processing the carrier phase observables.By using carrier phase observables,the relative positioning is obtained in centimeter level.GPS interferometry has been firstly used in precise static relative positioning,and thereafter in kinematic positioning.The carrier phase differential GPS based on interferometer principles can solve for the antenna baseline vector,defined as the vector between the antenna designated master and one of the slave antennas,connected to a rigid body.Determining the unknown baseline vectors between the antennas sits at the heart of GPS-based attitude determination.The conventional solution of the baseline vectors based on least-squares approach is inherently noisy,which results in the noisy attitude solutions.In this article,the complementary Kalman filter(CKF)is employed for solving the baseline vector in the attitude determination mechanism to improve the performance,where the receiver-satellite double differenced observable was utilized as the measurement.By using the carrier phase observables,the relative positioning is obtained in centimeter level.Employing the CKF provides several advantages,such as accuracy improvement,reliability enhancement,and real-time assurance.Simulation results based on the conventional method where the least-squares approach is involved,and the proposed method where the CKF is involved are compared and discussed.展开更多
To address a problem of autonomous attitude determination algorithm using gravitational field and geomagnetic field observation, a new recursive optimization autonomous attitude estimation algorithm is proposed. The a...To address a problem of autonomous attitude determination algorithm using gravitational field and geomagnetic field observation, a new recursive optimization autonomous attitude estimation algorithm is proposed. The algorithm is based on unscented Kalman filter(UKF), and can synchronously provide the attitude rate information. The simulated results show that the measurement precision of the method could be increased by 2 times compared to that of the common methods.展开更多
This paper researches the attitude determination of a body based on GPScarrier phase measurement, and the algorithms used is the mean field annealing neuralnetwork(MFANN), which has the advantages of high accuracy and...This paper researches the attitude determination of a body based on GPScarrier phase measurement, and the algorithms used is the mean field annealing neuralnetwork(MFANN), which has the advantages of high accuracy and rapidity. The MFANN approach is acombination of the competitive Hopfield neural network and the stochastic simulated annealingtechnique, which is efficacious in resolving the optimal attitude determination. Firstly, thefundamental principle of GPS attitude determination is described, then a test platform of attitudedetermination is set up, and the MFANN algorithm is verified to resolve integer ambiguity andazimuth angles. Lastly, the experimental example is presented by means of MFANN, and it shows thatthis method is effective.展开更多
This paper discusses the design and implementation of a low cost multi-sensor integrated attitude determination system for small unmanned aerial vehicles( UAVs),which uses strapdown inertial navigation system( SINS) b...This paper discusses the design and implementation of a low cost multi-sensor integrated attitude determination system for small unmanned aerial vehicles( UAVs),which uses strapdown inertial navigation system( SINS) based on micro electromechanical system( MEMS) inertial sensors,commercial GPS receiver,and 3-axis magnetometer.MEMS-SINS initial attitude determination cannot be well performed for the reason that the MEMS inertial sensors biases are time-varying and poor repeatability,therefore in this paper the magnetometer and inclinometer are used to assist the MEMS-SINS initial attitude determination and MEMS inertial sensors field calibration.Furthermore,the attitude determination algorithms are presented to estimate the full attitude during GPS signal outage and non-accelerating situation.Additionally,the attitude information estimation results are compared with the reference of the non-magnetic marble platform and 3-axis turntable.Then the attitude estimation precision satisfies the requirement of attitude measurement for small UAVs during GPS signal outage and availability.Finally,the small UAV autonomous flight test results show that the low cost and real-time attitude determination system can yield continuous,reliable and effective attitude information for small UAVs.展开更多
In this paper,the estimator-based Global Positioning System(GPS)attitude and angular velocity determination is presented.Outputs of the attitude estimator include the attitude angles and attitude rates or body angular...In this paper,the estimator-based Global Positioning System(GPS)attitude and angular velocity determination is presented.Outputs of the attitude estimator include the attitude angles and attitude rates or body angular velocities,depending on the design of estimator.Traditionally as a position,velocity and time sensor,the GPS also offers a free attitude-determination interferometer.GPS research and applications to the field of attitude determination using carrier phase or Doppler measurement has been extensively conducted.The rawattitude solution using the interferometry technique based on the least-squares approach is inherently noisy.The estimator such as the Kalman filter(KF)or extended Kalman filter(EKF)can be incorporated into the GPS interferometer,potentially providing several advantages,such as accuracy improvement,reliability enhancement,and real-time characteristics.Three estimator-based approaches are investigated for performance comparison,including(1)KF with measurement involving attitude angles only;(2)EKF with measurements based on attitude angles only;(3)EKF with measurements involving both attitude angles and body angular rates.The assistance from body mounted gyroscopes,if available,can be utilized as the measurements for further performance improvement,especially useful for the case of signal-challenged environment,such as the GPS outages.Modeling of the dynamic process involving the body angular rates and derivation of the related algorithm will be presented.Simulation results for various estimator-based approaches are conducted;performance comparison is presented for the case of GPS outages.展开更多
With the development of GPS carrier wave phase technology, it becomes possible that the height accuracy of centimeter level is got by GPS RTK technology. Vessel attitudes are very important parameters in marine survey...With the development of GPS carrier wave phase technology, it becomes possible that the height accuracy of centimeter level is got by GPS RTK technology. Vessel attitudes are very important parameters in marine survey. In this paper, they were determined by 4 GPS receivers. At the same time, the arithmetic and procedure of vessel attitude determining were given. Based on an experiment, some useful conclusions were obtained and the corresponding methods were put forward to improve the accuracy.展开更多
This paper initially reviews types of deep space navigation methods. Then, it studies the use of pulsars as one of sources emitting electromagnetic waves in navigation;hence more details regarding the pulsar physics a...This paper initially reviews types of deep space navigation methods. Then, it studies the use of pulsars as one of sources emitting electromagnetic waves in navigation;hence more details regarding the pulsar physics and the history of navigation using pulsars are presented. The various methods of navigation (including radio method), their advantages and disadvantages—in comparison with navigation using pulsars in spacecraft—are discussed. Then, the equations necessary for calculating position and velocity of a spacecraft (such as the arrival time of pulse from pulsar to the receiver) are introduced, and the methods of calculating position and velocity are dealt with. Finally, two algorithms are presented for positioning, and one for velocity. Attitude determination follows the same simple methods presented in various articles.展开更多
Hybrid maize farmers have to face diverse kinds of climate, biological, price and financial risks. Farmers' risk perceptions and risk attitudes are essential elements influencing farm operations and management decisi...Hybrid maize farmers have to face diverse kinds of climate, biological, price and financial risks. Farmers' risk perceptions and risk attitudes are essential elements influencing farm operations and management decisions. However, this important issue has been overlooked in the contemporary studies and therefore there is a dearth of literature on this important issue. The present research is therefore, an attempt to fill this gap. This study aims to quantify hybrid maize farmers' perceptions of disastrous risks, their attitudes towards risk and to explore the impacts of various farm and farm household factors on farmers' risk attitudes and risk perceptions. The present study is conducted in four hybrid maize growing districts of Punjab Province, Pakistan, using cross-sectional data of 400 hybrid maize farmers. Risk matrix and equally likely certainty equivalent (ELCE) method are used to rank farmers' perceptions of four catastrophic risk sources including climate, biological, price and financial risks and to investigate farmers' risk aversion attitudes, respectively. Furthermore, probit regression is used to analyze the determinants affecting farmers' risk attitudes and risk perceptions. The results of the study showed that majority of farmers are risk averse in nature and perceive price, biological and climate to be potential sources of risks to their farm enterprise. In addition, analysis divulges that distance from farm to main market, off-farm income, location dummies for Sahiwal and Okara, age, maize farming experience, access to extension agent, significantly (either negatively or positively) influence farmers' risk attitudes and risk perceptions. The study delivers valuable insights for farmers, agricultural insurance sector, extension services researchers and agricultural policy makers about the local understanding of risks to hybrid maize crop in developing countries, like Pakistan, and have implications for research on farmers' adaptation to exposed risks.展开更多
A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiv...A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiving antennas, a signal processing circuit and an algorithm. The whole system is relatively simple, the cost and weight, as well as power consumption, are very low.展开更多
The purpose of this study was to identify the existing rice breeding programs in Myanmar and to determine researchers' attitudes on hybrid rice research mid its determinmlts. A sample consists of 56 researchers who a...The purpose of this study was to identify the existing rice breeding programs in Myanmar and to determine researchers' attitudes on hybrid rice research mid its determinmlts. A sample consists of 56 researchers who are working in Department of Agricultural Research, Department of Agriculture and Yezin Agricultural University, and involving varietal development of hybrid rice. The research instruments were a questionnaire used by 4 points Likert scale of strongly agree, agree, less agree and not agree to measure on researchers' attitudes towards 14 determinants of varietal development of hybrid rice production. The study revealed that the average age of the researchers was 46.5 years ranged from 25 to 60 years. The majority of researchers were 51-60 years old (41.1%). The working experience of researchers ranged from 5 to 36 years and the metal of their experience was 20 years. The educational level was Ph.D. (35.7%), M.Agr.Sc. (26.8%), and B.Agr.Sc. (37.5%). Majority of researchers were female (76.8%) and 58.9% were rice breeders. Moreover, 48.2% of researchers obtained the hybrid rice technology from breeding training and the researchers who believed in their current breeding works were 51.8%. Among 33 rice breeders, 72.7% of the rice breeders applied only convention breeding method. In addition, researchers' opinions on farmer's perception of hybrid rice technology, 60.7% of the researchers agreed on inferior grain quality and 73.2% of researchers strongly agreed on not stable market. This study found out more thin1 half of the researchers strongly agreed on 10 out of 14 determinmlts such as poor infrastructure, low human resource development, parental problem, insufficient experience, limit germplasm resource, limit research facilities, no incentive for breeders, weak public-private partnership, fewer quality breeders and not enough research fund. Moreover, half of the researchers agreed on 3 determinants likely need special technical training, need international assistance and climate change challenges. Finally, development of hybrid rice research in Mymlmar, there will be needed international assistmlce, and upgraded to hybrid rice research center from currently hybrid rice research section and need integrated hybrid rice policy supported by government.展开更多
文摘Objective: The purpose of this study is to understand the current situation of knowledge, attitude, and practice of self-management in young patients with type 2 diabetes mellitus (T2DM) and to explore the relationship between general conditions (personal, social, and environment, clinical factors) and their knowledge, attitude, and practices (KAP) of diabetes self-management, This aims to provide patients with high-quality nursing care management and services, as well as to provide relevant recommendations for effective self-management. Methods: This study is a descriptive correlational study that used the purposive sampling method to investigate 359 patients with T2DM aged 18-25 years in four designated tertiary hospitals in Shandong Province. Results: Knowledge of self-management was correlated with sex, age, education level, occupation and work situation, monthly household income, medical payment method, family and friend support, frequency of diabetes health education, and diabetes complications. The attitude subscale was correlated with sex, age, education level, work situation, and family and friend support. The practice subscale was associated with age, education level, work situation, family and friend support, frequency of diabetes health education, and HbA1c values. Conclusion: Young adults aged 18-25 with T2DM have positive attitudes towards diabetes self-management, but there are still deficiencies in knowledge acquisition and behavioral practice. The KAP of self-management of diabetes is influenced by personal factors such as sex, age, and education level, and socio-environmental factors such as family income and family or friends’ social support. Additionally, clinical factors such as complications and HbA1c values significantly impacted the patient’s disease self-management ability.
文摘A multiple antenna GPS system integrated with MEMS-based INS is proposed by data fusion. The system is applied to attitude determination due to its high accuracy, the high output rate, low latency, quick initialization, and good robustness and redundancy. The mathematical method for realizing the system is given. The system can provide attitude and other navigation information even without GPS measurement for a period of time. Experimental results show that, under the condition of 200 Hz, the attitude, the position, the velocity, the acceleration, and the angular rate can achieve 0. 08°/s, 1.5 m, 0. 1 m/s, 0. 12 m/s^2 and 0. 1°/s.
基金National Natural Science Foundation of China (10402034)
文摘Global Positioning System (GPS) /Inertial Navigation System (INS) integrated system is continuously gaining research interests in many positioning and navigation fields. Kalman filtering-based integrated algorithm has some drawbacks on stability, computation load, robustness, and system observability performances. Based on neural network technology, a new GPS/INS integration filtering algorithm is studied for an integration scheme of the attitude determination GPS/INS integrated navigation system. Through some theoretic analysis, this algorithm not only has good estimation performance, but also has better robustness to the system model and noise than the traditional Kalman algorithm. To assess the performance of the proposed integrated model more deeply, some simulation is done to compare with the traditional Kalman filter model. The results indicate that the proposed model provides a significant improvement in some performance, such as accuracy, stability, robustness, and so on.
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).
文摘As an important sensor in the navigation systems,star sensors and the gyro play important roles in spacecraft attitude determination system.Complex environmental factors are the main sources of error in attitude determination.The error influence of different benchmarks and the disintegration mode between the star sensor and the gyro is analyzed in theory.The integrated design of the star sensor and the gyro on the same benchmark can effectively avoid the error influence and improves the spacecraft attitude determination accuracy.Simulation results indicate that when the stars sensor optical axis vectors overlap the reference coordinate axis of the gyro in the same benchmark,the attitude determination accuracy improves.
文摘GPS-based attitude system is an important research field, since it is a valuable technique for the attitude determination of platforms. There exist two classes approaches for attitude determination using the GPS. The one determines attitude via baseline estimates in two frames, the other one solves for attitude by incorporating the attitude parameters directly into the GPS measurements. However, comparisons between these two classes approaches have been unexplored. First of all, two algorithms are introduced in detail which on behalf of these two kinds of approaches. Then we present numerical simulations demonstrating the performance of our algorithms and provide a comparison evaluating.
基金the Ministry of Science and Technology of the Republic of China[Grant No.MOST 108-2221-E-019-013].
文摘In this paper,the Global Positioning System(GPS)interferometer provides the preliminarily computed quaternions,which are then employed as the measurement of the extended Kalman filter(EKF)for the attitude determination system.The estimated quaternion elements from the EKF output with noticeably improved precision can be converted to the Euler angles for navigation applications.The aim of the study is twofold.Firstly,the GPS-based computed quaternion vector is utilized to avoid the singularity problem.Secondly,the quaternion estimator based on the EKF is adopted to improve the estimation accuracy.Determination of the unknown baseline vector between the antennas sits at the heart of GPS-based attitude determination.Although utilization of the carrier phase observables enables the relative positioning to achieve centimeter level accuracy,however,the quaternion elements derived from the GPS interferometer are inherently noisy.This is due to the fact that the baseline vectors estimated by the least-squares method are based on the raw double-differenced measurements.Construction of the transformation matrix is accessible according to the estimate of baseline vectors and thereafter the computed quaternion elements can be derived.Using the Euler angle method,the process becomes meaningless when the angles are at 90where the singularity problem occurs.A good alternative is the quaternion approach,which possesses advantages over the equivalent Euler angle based transformation since they apply to all attitudes.Simulation results on the attitude estimation performance based on the proposed method will be presented and compared to the conventional method.The results presented in this paper elucidate the superiority of proposed algorithm.
基金This work has been partially supported by the Ministry of Science and Technology of the Republic of China[Grant Number:MOST 108-2221-E-019-013].
文摘The Global Positioning System(GPS)offers the interferometer for attitude determination by processing the carrier phase observables.By using carrier phase observables,the relative positioning is obtained in centimeter level.GPS interferometry has been firstly used in precise static relative positioning,and thereafter in kinematic positioning.The carrier phase differential GPS based on interferometer principles can solve for the antenna baseline vector,defined as the vector between the antenna designated master and one of the slave antennas,connected to a rigid body.Determining the unknown baseline vectors between the antennas sits at the heart of GPS-based attitude determination.The conventional solution of the baseline vectors based on least-squares approach is inherently noisy,which results in the noisy attitude solutions.In this article,the complementary Kalman filter(CKF)is employed for solving the baseline vector in the attitude determination mechanism to improve the performance,where the receiver-satellite double differenced observable was utilized as the measurement.By using the carrier phase observables,the relative positioning is obtained in centimeter level.Employing the CKF provides several advantages,such as accuracy improvement,reliability enhancement,and real-time assurance.Simulation results based on the conventional method where the least-squares approach is involved,and the proposed method where the CKF is involved are compared and discussed.
文摘To address a problem of autonomous attitude determination algorithm using gravitational field and geomagnetic field observation, a new recursive optimization autonomous attitude estimation algorithm is proposed. The algorithm is based on unscented Kalman filter(UKF), and can synchronously provide the attitude rate information. The simulated results show that the measurement precision of the method could be increased by 2 times compared to that of the common methods.
文摘This paper researches the attitude determination of a body based on GPScarrier phase measurement, and the algorithms used is the mean field annealing neuralnetwork(MFANN), which has the advantages of high accuracy and rapidity. The MFANN approach is acombination of the competitive Hopfield neural network and the stochastic simulated annealingtechnique, which is efficacious in resolving the optimal attitude determination. Firstly, thefundamental principle of GPS attitude determination is described, then a test platform of attitudedetermination is set up, and the MFANN algorithm is verified to resolve integer ambiguity andazimuth angles. Lastly, the experimental example is presented by means of MFANN, and it shows thatthis method is effective.
基金Sponsored by the China Postdoctoral Science Foundation(Grant No.2013M540857)the Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-14-019A1)
文摘This paper discusses the design and implementation of a low cost multi-sensor integrated attitude determination system for small unmanned aerial vehicles( UAVs),which uses strapdown inertial navigation system( SINS) based on micro electromechanical system( MEMS) inertial sensors,commercial GPS receiver,and 3-axis magnetometer.MEMS-SINS initial attitude determination cannot be well performed for the reason that the MEMS inertial sensors biases are time-varying and poor repeatability,therefore in this paper the magnetometer and inclinometer are used to assist the MEMS-SINS initial attitude determination and MEMS inertial sensors field calibration.Furthermore,the attitude determination algorithms are presented to estimate the full attitude during GPS signal outage and non-accelerating situation.Additionally,the attitude information estimation results are compared with the reference of the non-magnetic marble platform and 3-axis turntable.Then the attitude estimation precision satisfies the requirement of attitude measurement for small UAVs during GPS signal outage and availability.Finally,the small UAV autonomous flight test results show that the low cost and real-time attitude determination system can yield continuous,reliable and effective attitude information for small UAVs.
基金This work has been partially supported by the Ministry of Science and Technology,Taiwan[Grant Numbers MOST 109-2221-E-019-010 and MOST 110-2221-E-019-042].
文摘In this paper,the estimator-based Global Positioning System(GPS)attitude and angular velocity determination is presented.Outputs of the attitude estimator include the attitude angles and attitude rates or body angular velocities,depending on the design of estimator.Traditionally as a position,velocity and time sensor,the GPS also offers a free attitude-determination interferometer.GPS research and applications to the field of attitude determination using carrier phase or Doppler measurement has been extensively conducted.The rawattitude solution using the interferometry technique based on the least-squares approach is inherently noisy.The estimator such as the Kalman filter(KF)or extended Kalman filter(EKF)can be incorporated into the GPS interferometer,potentially providing several advantages,such as accuracy improvement,reliability enhancement,and real-time characteristics.Three estimator-based approaches are investigated for performance comparison,including(1)KF with measurement involving attitude angles only;(2)EKF with measurements based on attitude angles only;(3)EKF with measurements involving both attitude angles and body angular rates.The assistance from body mounted gyroscopes,if available,can be utilized as the measurements for further performance improvement,especially useful for the case of signal-challenged environment,such as the GPS outages.Modeling of the dynamic process involving the body angular rates and derivation of the related algorithm will be presented.Simulation results for various estimator-based approaches are conducted;performance comparison is presented for the case of GPS outages.
文摘With the development of GPS carrier wave phase technology, it becomes possible that the height accuracy of centimeter level is got by GPS RTK technology. Vessel attitudes are very important parameters in marine survey. In this paper, they were determined by 4 GPS receivers. At the same time, the arithmetic and procedure of vessel attitude determining were given. Based on an experiment, some useful conclusions were obtained and the corresponding methods were put forward to improve the accuracy.
文摘This paper initially reviews types of deep space navigation methods. Then, it studies the use of pulsars as one of sources emitting electromagnetic waves in navigation;hence more details regarding the pulsar physics and the history of navigation using pulsars are presented. The various methods of navigation (including radio method), their advantages and disadvantages—in comparison with navigation using pulsars in spacecraft—are discussed. Then, the equations necessary for calculating position and velocity of a spacecraft (such as the arrival time of pulse from pulsar to the receiver) are introduced, and the methods of calculating position and velocity are dealt with. Finally, two algorithms are presented for positioning, and one for velocity. Attitude determination follows the same simple methods presented in various articles.
基金financially supported by the National Natural Science Foundation of China (NSFC,71473100NSFC-CGIAR,71461010701)
文摘Hybrid maize farmers have to face diverse kinds of climate, biological, price and financial risks. Farmers' risk perceptions and risk attitudes are essential elements influencing farm operations and management decisions. However, this important issue has been overlooked in the contemporary studies and therefore there is a dearth of literature on this important issue. The present research is therefore, an attempt to fill this gap. This study aims to quantify hybrid maize farmers' perceptions of disastrous risks, their attitudes towards risk and to explore the impacts of various farm and farm household factors on farmers' risk attitudes and risk perceptions. The present study is conducted in four hybrid maize growing districts of Punjab Province, Pakistan, using cross-sectional data of 400 hybrid maize farmers. Risk matrix and equally likely certainty equivalent (ELCE) method are used to rank farmers' perceptions of four catastrophic risk sources including climate, biological, price and financial risks and to investigate farmers' risk aversion attitudes, respectively. Furthermore, probit regression is used to analyze the determinants affecting farmers' risk attitudes and risk perceptions. The results of the study showed that majority of farmers are risk averse in nature and perceive price, biological and climate to be potential sources of risks to their farm enterprise. In addition, analysis divulges that distance from farm to main market, off-farm income, location dummies for Sahiwal and Okara, age, maize farming experience, access to extension agent, significantly (either negatively or positively) influence farmers' risk attitudes and risk perceptions. The study delivers valuable insights for farmers, agricultural insurance sector, extension services researchers and agricultural policy makers about the local understanding of risks to hybrid maize crop in developing countries, like Pakistan, and have implications for research on farmers' adaptation to exposed risks.
基金Supported by the National Aeronautics and Space Administration(NASA),Goddard Space Flight Center,USA,under Contract AN13709
文摘A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiving antennas, a signal processing circuit and an algorithm. The whole system is relatively simple, the cost and weight, as well as power consumption, are very low.
文摘The purpose of this study was to identify the existing rice breeding programs in Myanmar and to determine researchers' attitudes on hybrid rice research mid its determinmlts. A sample consists of 56 researchers who are working in Department of Agricultural Research, Department of Agriculture and Yezin Agricultural University, and involving varietal development of hybrid rice. The research instruments were a questionnaire used by 4 points Likert scale of strongly agree, agree, less agree and not agree to measure on researchers' attitudes towards 14 determinants of varietal development of hybrid rice production. The study revealed that the average age of the researchers was 46.5 years ranged from 25 to 60 years. The majority of researchers were 51-60 years old (41.1%). The working experience of researchers ranged from 5 to 36 years and the metal of their experience was 20 years. The educational level was Ph.D. (35.7%), M.Agr.Sc. (26.8%), and B.Agr.Sc. (37.5%). Majority of researchers were female (76.8%) and 58.9% were rice breeders. Moreover, 48.2% of researchers obtained the hybrid rice technology from breeding training and the researchers who believed in their current breeding works were 51.8%. Among 33 rice breeders, 72.7% of the rice breeders applied only convention breeding method. In addition, researchers' opinions on farmer's perception of hybrid rice technology, 60.7% of the researchers agreed on inferior grain quality and 73.2% of researchers strongly agreed on not stable market. This study found out more thin1 half of the researchers strongly agreed on 10 out of 14 determinmlts such as poor infrastructure, low human resource development, parental problem, insufficient experience, limit germplasm resource, limit research facilities, no incentive for breeders, weak public-private partnership, fewer quality breeders and not enough research fund. Moreover, half of the researchers agreed on 3 determinants likely need special technical training, need international assistance and climate change challenges. Finally, development of hybrid rice research in Mymlmar, there will be needed international assistmlce, and upgraded to hybrid rice research center from currently hybrid rice research section and need integrated hybrid rice policy supported by government.