The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Fi...The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20℃ . At days 7, 13 and 18,the firmness of tomatoes coated with HPMC was significantly ( P ≤ 0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≤0.05) delay the changes in color of tomatoes stored at 20℃ . The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.展开更多
This study was conducted to investigate the genetic regularity of indexes related to freshness keeping and its molecular basis by acquiring 6 generations （P1, P2, F1, B1, B2 and F2） of an inbred line T3 with long fr...This study was conducted to investigate the genetic regularity of indexes related to freshness keeping and its molecular basis by acquiring 6 generations （P1, P2, F1, B1, B2 and F2） of an inbred line T3 with long freshness period × an inbred line T15 with short freshness period in sweet corn. The genetic analysis of the indexes was performed by major gene＋polygene mixed genetic model combined with the genetic analysis combining six generations.The results showed that the decreasing rate of the postharvest sugar content in the T3 was controlled by two pairs of additive-dominante-epistatic major genes＋additive-dominant polygenes; each segregating generation was affected by its major genes, the heritability of major genes and polygene in the B1 generation was 74.63% and 17.67%, respectively; the heritability of major gene and potygene in the B2 was 91.98% and 0,00%, respectively; and the heritability of major gene and polygene inthe F2 was 82.67%, and 12.93%, respectively.展开更多
Aquatic products are extremely perishable food commodities. Developing methods to keep the freshness of fish represents a major task of the fishery processing industry. Application of Lactic Acid Bacteria(LAB) as food...Aquatic products are extremely perishable food commodities. Developing methods to keep the freshness of fish represents a major task of the fishery processing industry. Application of Lactic Acid Bacteria(LAB) as food preservative is a novel approach. In the present study, the possibility of using lactic acid bacteria in freshness keeping of tilapia fillets as sashimi was examined. Fish fillets were dipped in Lactobacillus plantarum 1.19(obtained from China General Microbiological Culture Collection Center) suspension as LAB-treated group. Changes in K-value, APC, sensory properties and microbial flora were analyzed. Results showed that LAB treatment slowed the increase of K-value and APC in the earlier storage, and caused a smooth decrease in sensory score. Gram-negative bacteria dominated during refrigerated storage, with Pseudomonas and Aeromonas being relatively abundant. Lactobacillus plantarum 1.19 had no obvious inhibitory effect against these Gram-negatives. However, Lactobacillus plantarum 1.19 changed the composition of Gram-positive bacteria. No Micrococcus were detected and the proportion of Staphylococcus decreased in the spoiled LAB-treated samples. The period that tilapia fillets could be used as sashimi material extended from 24 h to 48 h after LAB treatment. The potential of using LAB in sashimi processing was confirmed.展开更多
Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of...Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of 3% sucrose ＋ 50 mg/L citric acid ＋ 600 mg/L vitamin C ＋ 20 mg/L 6-BA could effectively maintain the water balance of the cut flower, prolong the vase life of the cut flower to 16.4 d, and maximize the flower diameter and the crown height.展开更多
The cold storage period of purple cabbage packaged with the respirat ory cling film may last 150 days at 2℃by dipping the root with 200×iprodione. Normal temperature storage and quick-freezing storage(-18℃) are...The cold storage period of purple cabbage packaged with the respirat ory cling film may last 150 days at 2℃by dipping the root with 200×iprodione. Normal temperature storage and quick-freezing storage(-18℃) are not suitable for purple cabbage.展开更多
This paper addresses the lane-keeping control problem for autonomous ground vehicles subject to input saturation and uncertain system parameters.An enhanced adaptive terminal sliding mode based prescribed performance ...This paper addresses the lane-keeping control problem for autonomous ground vehicles subject to input saturation and uncertain system parameters.An enhanced adaptive terminal sliding mode based prescribed performance control scheme is proposed,which enables the lateral position error of the vehicle to be kept within the prescribed performance boundaries all the time.This is achieved by firstly introducing an improved performance function into the controller design such that the stringent initial condition requirements can be relaxed,which further allows the global prescribed performance control result,and then,developing a multivariable adaptive terminal sliding mode based controller such that both input saturation and parameter uncertainties are handled effectively,which further ensures the robust lane-keeping control.Finally,the proposed control strategy is validated through numerical simulations,demonstrating its effectiveness.展开更多
[Objectives] This study was conducted to develop environmentally-friendly effective vase solutions for cut rose flowers convenient for ordinary household use. [Methods] The vase life, flowering stage, flower diameter ...[Objectives] This study was conducted to develop environmentally-friendly effective vase solutions for cut rose flowers convenient for ordinary household use. [Methods] The vase life, flowering stage, flower diameter variation, petal water content, and soluble protein and malondialdehyde contents were determined on cut rose flowers regularly during the vase period, to study the fresh-keeping effects of the vase solutions prepared from such three components as sugar, aspirin and Vc according to L9(33) orthogonal table design on cut rose flowers during the vase period. [Results] 20 g/L white granulated sugar+460 mg/L aspirin+50 mg/L Vc was the best combination in this study. [Conclusions] This study provides a reference for the research on the fresh-keeping vase solutions of household cut rose flowers.展开更多
In order to explore the fresh-keeping methods for zander fillet,we use vacuum packaging and partial freezing to process zander fillet,conduct a comparative analysis of sensory characteristics,percentage of water loss,...In order to explore the fresh-keeping methods for zander fillet,we use vacuum packaging and partial freezing to process zander fillet,conduct a comparative analysis of sensory characteristics,percentage of water loss,stiffness period,muscle stiffness,TVB-N and water activity during the storage,and assess the fresh-keeping effect of zander fillet under the conditions of vacuum packaging and partial freezing. The results show that zander can be dead after being placed into the 2℃ water for 30 min,and the stiffness period can be extended about 100 min compared with natural death; the percentage of water loss under the conditions of vacuum packaging before partial freezing is 2. 6% lower than under the conditions of partial freezing before vacuum packaging; after being stored at- 7℃ and- 4℃ for 15 d,TVB- N of fillet ≤15 mg /kg; TVB- N of fillet at- 7℃ is 25% lower than at- 4℃.展开更多
Rwanda secured access to one of the world’s most lucrative agricultural markets this month when it finalised a trade protocol allowing fresh avocado exports to China,a deal that could fundamentally alter the trajecto...Rwanda secured access to one of the world’s most lucrative agricultural markets this month when it finalised a trade protocol allowing fresh avocado exports to China,a deal that could fundamentally alter the trajectory of the country’s trade.展开更多
How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of...How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of this passage is to clarify the basic content of motivation,including the definition,classification,importance,etc.how the current situation is in senior high students’English learning motivation,what should be done to keep such motivation.In the following part,it will be read that the introduction,the chapter stating the content and classification of(L2)motivation,the chapter analyzing the necessity and state of L2 motivation at senor high,the chapter offering approach to keep that motivation,and the conclusion.All of them use the comparison,explanation and cites.展开更多
Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanne...Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanned aerial vehicles(multi-UAV) is proposed based on consensus, aiming at maintaining a specified geometric configuration. A formation control algorithm with guidance and corresponding flight controllers is given, managing position and attitude, respectively. In order to follow a three-dimensional predefined flight path, by introducing the tracking orders as reference states into the consensus, the formation control algorithm is designed, following the predefined flight path and maintaining geometric configuration simultaneously. The flight controllers are constructed by nonlinear dynamic inverse, including attitude design and velocity design. With the whole system composed of a nonlinear six-degree-of-freedom UAV model, the formation control algorithm and the flight controllers, the formation keeping strategy is closed loop and with full states. In simulation, three-dimensional formation flight demonstrates the feasibility and effectiveness of the proposed strategy.展开更多
The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynam...The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.展开更多
This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers ...This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers which has the advantages of strong function, high flexibility and reliability, It satisfies the requirements for efficient performance,light weight, small volume,and low consumption of power for micro satellite.展开更多
Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to ...Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to the infantry squad organization and is used to realize multiple mobile robots to keep formations. Simulations verify the validity of the approach to keep formation, which combines the behavior-based method and formation feedback. The effects of formation feedback on the performance of the system are analyzed.展开更多
In this paper, with parametric uncertainties such as the mass of vehicle, the inertia of vehicle about vertical axis, and the tire cornering stiffness, we deal with the vehicle lateral control problem in intelligent v...In this paper, with parametric uncertainties such as the mass of vehicle, the inertia of vehicle about vertical axis, and the tire cornering stiffness, we deal with the vehicle lateral control problem in intelligent vehicle systems. Based on the dynamical model of vehicle, by applying Lyapunov function method, the control problem for lane keeping in the presence of parametric uncertainty is studied, the direct adaptive algorithm to compensate for parametric variations is proposed and the terminal sliding mode variable structure control laws are designed with look-ahead references systems. The stability of the system is investigated from the zero dynamics analysis. Simulation results show that convergence rates of the lateral displacement error, yaw angle error and slid angle are fast.展开更多
In real-world scenarios,the uncertainty of measurements cannot be handled efficiently by traditional model predictive control(MPC).A stochastic MPC(SMPC)method for handling the uncertainty of states in autonomous driv...In real-world scenarios,the uncertainty of measurements cannot be handled efficiently by traditional model predictive control(MPC).A stochastic MPC(SMPC)method for handling the uncertainty of states in autonomous driving lane-keeping scenarios is presented in this paper.A probabilistic system is constructed by considering the variance of states.The probabilistic problem is then transformed into a solvable deterministic optimization problem in two steps.First,the cost function is separated into mean and variance components.The mean component is calculated online,whereas the variance component can be calculated offline.Second,Cantelli’s inequality is adopted for the deterministic reformulation of constraints.Consequently,the original probabilistic problem is transformed into a quadratic programming problem.To validate the feasibility and effectiveness of the proposed control method,we compared the SMPC controller with a traditional MPC controller in a lane-keeping scenario.The results demonstrate that the SMPC controller is more effective overall and produces smaller steady-state distance errors.展开更多
Regarding the lane keeping system,path tracking accuracy and lateral stability at high speeds need to be taken into account especially for commercial vehicles due to the characteristics of larger mass,longer wheelbase...Regarding the lane keeping system,path tracking accuracy and lateral stability at high speeds need to be taken into account especially for commercial vehicles due to the characteristics of larger mass,longer wheelbase and higher mass center.To improve the performance mentioned above comprehensively,the control strategy based on improved artificial potential field(APF)algorithm is proposed.In the paper,time to lane crossing(TLC)is introduced into the potential field function to enhance the accuracy of path tracking,meanwhile the vehicle dynamics parameters including yaw rate and lateral acceleration are chosen as the repulsive force field source.The lane keeping controller based on improved APF algorithm is designed and the stability of the control system is proved based on Lyapunov theory.In addition,adaptive inertial weight particle swarm optimization algorithm(AIWPSO)is applied to optimize the gain of each potential field function.The co-simulation results indicate that the comprehensive evaluation index respecting lane tracking accuracy and lateral stability is reduced remarkably.Finally,the proposed control strategy is verified by the HiL test.It provides a beneficial reference for dynamics control of commercial vehicles and enriches the theoretical development and practical application of artificial potential field method in the field of intelligent driving.展开更多
High-precision lane keeping is essential for the future autonomous driving.However,due to the imbalanced and inaccurate datasets collected by human drivers,current end-to-end driving models have poor lane keeping the ...High-precision lane keeping is essential for the future autonomous driving.However,due to the imbalanced and inaccurate datasets collected by human drivers,current end-to-end driving models have poor lane keeping the effect.To improve the precision of lane keeping,this study presents a novel multi-state model-based end-to-end lane keeping method.First,three driving states will be defined:going straight,turning right and turning left.Second,the finite-state machine(FSM)table as well as three kinds of training datasets will be generated based on the three driving states.Instead of collecting the dataset by human drivers,the accurate dataset will be collected by the high-performance path following controller.Third,three sets of parameters based on 3DCNN-LSTM model will be trained for going straight,turning left and turning right,which will be combined with FSM table to form a multi-state model.This study evaluates the multi-state model by testing it on five tracks and recording the lane keeping error.The result shows the multi-state model-based end-to-end method performs the higher precision of lane keeping than the traditional single end-to-end model.展开更多
In this paper, 3D track-keeping control method for autonomous underwater vehicle (AUV) with and without the influence of ocean current is investigated. Because the system to be controlled is highly nonlinear and stron...In this paper, 3D track-keeping control method for autonomous underwater vehicle (AUV) with and without the influence of ocean current is investigated. Because the system to be controlled is highly nonlinear and strong coupled, an approach is used to divide it into two subsystems. One is to control the heading and the track error on the horizontal plane. The other is to control the pitch and the track error on the vertical plane. The results of computer simulation show that the autopilot works properly, it can capture the current waypoint and turns to track the next path automatically.展开更多
文摘The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20℃ for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20℃ . At days 7, 13 and 18,the firmness of tomatoes coated with HPMC was significantly ( P ≤ 0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≤0.05) delay the changes in color of tomatoes stored at 20℃ . The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.
文摘This study was conducted to investigate the genetic regularity of indexes related to freshness keeping and its molecular basis by acquiring 6 generations （P1, P2, F1, B1, B2 and F2） of an inbred line T3 with long freshness period × an inbred line T15 with short freshness period in sweet corn. The genetic analysis of the indexes was performed by major gene＋polygene mixed genetic model combined with the genetic analysis combining six generations.The results showed that the decreasing rate of the postharvest sugar content in the T3 was controlled by two pairs of additive-dominante-epistatic major genes＋additive-dominant polygenes; each segregating generation was affected by its major genes, the heritability of major genes and polygene in the B1 generation was 74.63% and 17.67%, respectively; the heritability of major gene and potygene in the B2 was 91.98% and 0,00%, respectively; and the heritability of major gene and polygene inthe F2 was 82.67%, and 12.93%, respectively.
基金supported by the National Natural Science Foundation of China(No.31301587)Key Laboratory of Aquatic Product Processing,Ministry of Agriculture,China
文摘Aquatic products are extremely perishable food commodities. Developing methods to keep the freshness of fish represents a major task of the fishery processing industry. Application of Lactic Acid Bacteria(LAB) as food preservative is a novel approach. In the present study, the possibility of using lactic acid bacteria in freshness keeping of tilapia fillets as sashimi was examined. Fish fillets were dipped in Lactobacillus plantarum 1.19(obtained from China General Microbiological Culture Collection Center) suspension as LAB-treated group. Changes in K-value, APC, sensory properties and microbial flora were analyzed. Results showed that LAB treatment slowed the increase of K-value and APC in the earlier storage, and caused a smooth decrease in sensory score. Gram-negative bacteria dominated during refrigerated storage, with Pseudomonas and Aeromonas being relatively abundant. Lactobacillus plantarum 1.19 had no obvious inhibitory effect against these Gram-negatives. However, Lactobacillus plantarum 1.19 changed the composition of Gram-positive bacteria. No Micrococcus were detected and the proportion of Staphylococcus decreased in the spoiled LAB-treated samples. The period that tilapia fillets could be used as sashimi material extended from 24 h to 48 h after LAB treatment. The potential of using LAB in sashimi processing was confirmed.
文摘Using sucrose, citric acid and vitamin C as the basic liquid, different concentrations of 6-BA and B9 preservatives were added, and the carnation variety ＇ Master＇ was treated. The results showed that the formula of 3% sucrose ＋ 50 mg/L citric acid ＋ 600 mg/L vitamin C ＋ 20 mg/L 6-BA could effectively maintain the water balance of the cut flower, prolong the vase life of the cut flower to 16.4 d, and maximize the flower diameter and the crown height.
文摘The cold storage period of purple cabbage packaged with the respirat ory cling film may last 150 days at 2℃by dipping the root with 200×iprodione. Normal temperature storage and quick-freezing storage(-18℃) are not suitable for purple cabbage.
基金supported in part by the National Key Research and Development Program of China under Grant 2023YFA1011803in part by Natural Science Foundation of Chongqing,China under Grant CSTB2023NSCQ-MSX0588+2 种基金in part by the Fundamental Research Funds for the Central Universities,China under Grant 2023CDJKYJH047in part by the National Natural Science Foundation of China under Grant 62273064,Grant 61991400,Grant 61991403,Grant 61933012,Grant 62250710167,Grant 62203078in part by Innovation Support Program for International Students Returning to China under Grant cx2022016.
文摘This paper addresses the lane-keeping control problem for autonomous ground vehicles subject to input saturation and uncertain system parameters.An enhanced adaptive terminal sliding mode based prescribed performance control scheme is proposed,which enables the lateral position error of the vehicle to be kept within the prescribed performance boundaries all the time.This is achieved by firstly introducing an improved performance function into the controller design such that the stringent initial condition requirements can be relaxed,which further allows the global prescribed performance control result,and then,developing a multivariable adaptive terminal sliding mode based controller such that both input saturation and parameter uncertainties are handled effectively,which further ensures the robust lane-keeping control.Finally,the proposed control strategy is validated through numerical simulations,demonstrating its effectiveness.
文摘[Objectives] This study was conducted to develop environmentally-friendly effective vase solutions for cut rose flowers convenient for ordinary household use. [Methods] The vase life, flowering stage, flower diameter variation, petal water content, and soluble protein and malondialdehyde contents were determined on cut rose flowers regularly during the vase period, to study the fresh-keeping effects of the vase solutions prepared from such three components as sugar, aspirin and Vc according to L9(33) orthogonal table design on cut rose flowers during the vase period. [Results] 20 g/L white granulated sugar+460 mg/L aspirin+50 mg/L Vc was the best combination in this study. [Conclusions] This study provides a reference for the research on the fresh-keeping vase solutions of household cut rose flowers.
基金Supported by Key Science and Technology Project in Hainan Province(090110)
文摘In order to explore the fresh-keeping methods for zander fillet,we use vacuum packaging and partial freezing to process zander fillet,conduct a comparative analysis of sensory characteristics,percentage of water loss,stiffness period,muscle stiffness,TVB-N and water activity during the storage,and assess the fresh-keeping effect of zander fillet under the conditions of vacuum packaging and partial freezing. The results show that zander can be dead after being placed into the 2℃ water for 30 min,and the stiffness period can be extended about 100 min compared with natural death; the percentage of water loss under the conditions of vacuum packaging before partial freezing is 2. 6% lower than under the conditions of partial freezing before vacuum packaging; after being stored at- 7℃ and- 4℃ for 15 d,TVB- N of fillet ≤15 mg /kg; TVB- N of fillet at- 7℃ is 25% lower than at- 4℃.
文摘Rwanda secured access to one of the world’s most lucrative agricultural markets this month when it finalised a trade protocol allowing fresh avocado exports to China,a deal that could fundamentally alter the trajectory of the country’s trade.
文摘How will we keep the motivation during the second language as long as we can,which confuses us,though what the L2 motivation is and how it is developed have been discussed by the psychologists,educators,etc.The aim of this passage is to clarify the basic content of motivation,including the definition,classification,importance,etc.how the current situation is in senior high students’English learning motivation,what should be done to keep such motivation.In the following part,it will be read that the introduction,the chapter stating the content and classification of(L2)motivation,the chapter analyzing the necessity and state of L2 motivation at senor high,the chapter offering approach to keep that motivation,and the conclusion.All of them use the comparison,explanation and cites.
基金Project(61473229)supported by the National Natural Science Foundation of ChinaProjects(310832163403,310832161012)supported by the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University,ChinaProject(CXY1512-3)supported by the Xi'an Science and Technology Plan,China
文摘Consensus is an emerging technique using neighbor-to-neighbor interaction to generate steering commands for cooperative control of multiple vehicles. A three-dimensional formation keeping strategy for multiple unmanned aerial vehicles(multi-UAV) is proposed based on consensus, aiming at maintaining a specified geometric configuration. A formation control algorithm with guidance and corresponding flight controllers is given, managing position and attitude, respectively. In order to follow a three-dimensional predefined flight path, by introducing the tracking orders as reference states into the consensus, the formation control algorithm is designed, following the predefined flight path and maintaining geometric configuration simultaneously. The flight controllers are constructed by nonlinear dynamic inverse, including attitude design and velocity design. With the whole system composed of a nonlinear six-degree-of-freedom UAV model, the formation control algorithm and the flight controllers, the formation keeping strategy is closed loop and with full states. In simulation, three-dimensional formation flight demonstrates the feasibility and effectiveness of the proposed strategy.
基金supported by Hunan Provincial Innovation Foundation for Postgraduate(Grant No. CX2011B005)National University of Defense Technology Innovation Foundation for Postgraduate, China(GranNo. B110105)
文摘The stratosphere airship provides a unique and promising platform for earth observation. Researches on the project design and control scheme for earth observation platforms are still rarely documented. Nonlinear dynamics, model uncertainties, and external disturbances contribute to the difficulty in maneuvering the stratosphere airship. A key technical challenge for the earth observation platform is station keeping, or the ability to remain fixed over a geo-location. This paper investigates the conceptual design, modeling and station-keeping attitude control of the near-space earth observation platform. A conceptual design of the earth observation platform is presented. The dynamics model of the platform is derived from the Newton-Euler formulation, and the station-keeping control system of the platform is formulated. The station-keeping attitude control approach for the platform is proposed. The multi-input multi-output nonlinear control system is decoupled into three single-input single-output linear subsystems via feedback linearization, the attitude controller design is carried out on the new linear systems using terminal sliding mode control, and the global stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the designed control system is simulated by using the variable step Runge-Kutta integrator. Simulation results show that the control system tracks the commanded attitude with an error of zero, which verify the effectiveness and robustness of the designed control system in the presence of parametric uncertainties. The near-space earth observation platform has several advantages over satellites, such as high resolution, fast to deploy, and convenient to retrieve, and the proposed control scheme provides an effective approach for station-keeping attitude control of the earth observation platform.
文摘This paper presents the design of hardware and software of the house keeping system for a certain micro satellite. The system uses micro electronic technique, large scale integrated circuits, processors and computers which has the advantages of strong function, high flexibility and reliability, It satisfies the requirements for efficient performance,light weight, small volume,and low consumption of power for micro satellite.
文摘Approaches to the study of formation keeping for multiple mobile robots are analyzed and a behavior-based robot model is built in this paper. And, a kind of coordination architecture is presented, which is similar to the infantry squad organization and is used to realize multiple mobile robots to keep formations. Simulations verify the validity of the approach to keep formation, which combines the behavior-based method and formation feedback. The effects of formation feedback on the performance of the system are analyzed.
基金Sponsored by the National Natural Science Foundation of China(Grant No.10772152)
文摘In this paper, with parametric uncertainties such as the mass of vehicle, the inertia of vehicle about vertical axis, and the tire cornering stiffness, we deal with the vehicle lateral control problem in intelligent vehicle systems. Based on the dynamical model of vehicle, by applying Lyapunov function method, the control problem for lane keeping in the presence of parametric uncertainty is studied, the direct adaptive algorithm to compensate for parametric variations is proposed and the terminal sliding mode variable structure control laws are designed with look-ahead references systems. The stability of the system is investigated from the zero dynamics analysis. Simulation results show that convergence rates of the lateral displacement error, yaw angle error and slid angle are fast.
基金the Science and Technology Commission of Shanghai Municipality(No.19511103503)。
文摘In real-world scenarios,the uncertainty of measurements cannot be handled efficiently by traditional model predictive control(MPC).A stochastic MPC(SMPC)method for handling the uncertainty of states in autonomous driving lane-keeping scenarios is presented in this paper.A probabilistic system is constructed by considering the variance of states.The probabilistic problem is then transformed into a solvable deterministic optimization problem in two steps.First,the cost function is separated into mean and variance components.The mean component is calculated online,whereas the variance component can be calculated offline.Second,Cantelli’s inequality is adopted for the deterministic reformulation of constraints.Consequently,the original probabilistic problem is transformed into a quadratic programming problem.To validate the feasibility and effectiveness of the proposed control method,we compared the SMPC controller with a traditional MPC controller in a lane-keeping scenario.The results demonstrate that the SMPC controller is more effective overall and produces smaller steady-state distance errors.
基金Supported by National Natural Science Foundation of China(Grant Nos.51605199,U20A20333,52225212)Six Talent Peak Funding Projects in Jiangsu Province of China(Grant No.2019-GDZB-084)Key Science and Technology Support Program in Taizhou City of China(Grant No.TG202307).
文摘Regarding the lane keeping system,path tracking accuracy and lateral stability at high speeds need to be taken into account especially for commercial vehicles due to the characteristics of larger mass,longer wheelbase and higher mass center.To improve the performance mentioned above comprehensively,the control strategy based on improved artificial potential field(APF)algorithm is proposed.In the paper,time to lane crossing(TLC)is introduced into the potential field function to enhance the accuracy of path tracking,meanwhile the vehicle dynamics parameters including yaw rate and lateral acceleration are chosen as the repulsive force field source.The lane keeping controller based on improved APF algorithm is designed and the stability of the control system is proved based on Lyapunov theory.In addition,adaptive inertial weight particle swarm optimization algorithm(AIWPSO)is applied to optimize the gain of each potential field function.The co-simulation results indicate that the comprehensive evaluation index respecting lane tracking accuracy and lateral stability is reduced remarkably.Finally,the proposed control strategy is verified by the HiL test.It provides a beneficial reference for dynamics control of commercial vehicles and enriches the theoretical development and practical application of artificial potential field method in the field of intelligent driving.
基金National Natural Science Foundation of China(U1764264/61873165).
文摘High-precision lane keeping is essential for the future autonomous driving.However,due to the imbalanced and inaccurate datasets collected by human drivers,current end-to-end driving models have poor lane keeping the effect.To improve the precision of lane keeping,this study presents a novel multi-state model-based end-to-end lane keeping method.First,three driving states will be defined:going straight,turning right and turning left.Second,the finite-state machine(FSM)table as well as three kinds of training datasets will be generated based on the three driving states.Instead of collecting the dataset by human drivers,the accurate dataset will be collected by the high-performance path following controller.Third,three sets of parameters based on 3DCNN-LSTM model will be trained for going straight,turning left and turning right,which will be combined with FSM table to form a multi-state model.This study evaluates the multi-state model by testing it on five tracks and recording the lane keeping error.The result shows the multi-state model-based end-to-end method performs the higher precision of lane keeping than the traditional single end-to-end model.
文摘In this paper, 3D track-keeping control method for autonomous underwater vehicle (AUV) with and without the influence of ocean current is investigated. Because the system to be controlled is highly nonlinear and strong coupled, an approach is used to divide it into two subsystems. One is to control the heading and the track error on the horizontal plane. The other is to control the pitch and the track error on the vertical plane. The results of computer simulation show that the autopilot works properly, it can capture the current waypoint and turns to track the next path automatically.
