A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis...A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics, parameters and working points of the system. The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller. The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance, strong robustness and satisfactory adaptability to various system parameters. According to the results, system can successfully gain high accuracy and fast response signal. Also, the mathematical model of system is also testified by the experimental results.展开更多
This paper proposes a continuous control set model predictive control(CCS-MPC)algorithm of a modular multilevel matrix converter(M3C)for low-frequency AC transmission(LFAC),via which the offshore wind farm(OWF)is inte...This paper proposes a continuous control set model predictive control(CCS-MPC)algorithm of a modular multilevel matrix converter(M3C)for low-frequency AC transmission(LFAC),via which the offshore wind farm(OWF)is integrated.The M3C is operated with a 16.7 Hz frequency at the OWF side and a 50 Hz frequency at the onshore grid side.The balance of the capacitor voltages and the regulation of circulating currents in the M3C are performed using the proposed CCSMPC algorithm,which is based on the online solution of a cost function with constraints.Simulation and experimental work(with a 5 kW M3C prototype)are provided,showing the performance of the LFAC system to operate with symmetrical and asymmetrical voltage dips,active and reactive power steps,and optimal limitation of currents and voltages using constraints.Unlike previous publications,the predictive control system in this paper allows seamless operation under balanced and unbalanced conditions,for instance,during asymmetrical voltage dips.展开更多
To handle input and output time delays that commonly exist in many networked control systems(NCSs), a new robust continuous sliding mode control(CSMC) scheme is proposed for the output tracking in uncertain single inp...To handle input and output time delays that commonly exist in many networked control systems(NCSs), a new robust continuous sliding mode control(CSMC) scheme is proposed for the output tracking in uncertain single input-single-output(SISO) networked control systems. This scheme consists of three consecutive steps. First, although the network-induced delay in those systems can be effectively handled by using Pade approximation(PA), the unmatched disturbance cames out as another difficulty in the control design. Second, to actively estimate this unmatched disturbance, a generalized proportional integral observer(GPIO) technique is utilized based on only one measured state. Third, by constructing a new sliding manifold with the aid of the estimated unmatched disturbance and states, a GPIO-based CSMC is synthesized, which is employed to cope with not only matched and unmatched disturbances, but also networkinduced delays. The stability of the entire closed-loop system under the proposed GPIO-based CSMC is detailedly analyzed.The promising tracking efficiency and feasibility of the proposed control methodology are verified through simulations and experiments on Quanser's servo module for motion control under various test conditions.展开更多
On the basis of the theory of continuous compaction technology, we put forward the vibratory compaction value （VCV） index measured by a roller compactor, in order to evaluate the quality of continuously compacted su...On the basis of the theory of continuous compaction technology, we put forward the vibratory compaction value （VCV） index measured by a roller compactor, in order to evaluate the quality of continuously compacted subgrade. The relationships between the VCV index and the currently used indexes K30, Evd, Ev1 and Ev2, were explored by analyzing the experimental data collected from two test sections on the Beijing - Shanghai High-Speed Railway. The result shows that the VCV index has a linear relationship with the currently used indexes.展开更多
Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dy...Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.展开更多
The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circu...The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.展开更多
We study a new class of two-player,zero-sum,deterministic differential games where each player uses both continuous and impulse controls in an infinite horizon with discounted payoff.We assume that the form and cost o...We study a new class of two-player,zero-sum,deterministic differential games where each player uses both continuous and impulse controls in an infinite horizon with discounted payoff.We assume that the form and cost of impulses depend on nonlinear functions and the state of the system,respectively.We use Bellman's dynamic programming principle(DPP)and viscosity solutions approach to show,for this class of games,the existence and uniqueness of a solution for the associated Hamilton-Jacobi-Bellman-Isaacs(HJBI)partial differential equations(PDEs).We then,under Isaacs'condition,deduce that the lower and upper value functions coincide,and we give a computational procedure with a numerical test for the game.展开更多
During five-axis machining of impeller, the excessive local interference avoidance leads to inconsistency of cutter posture, low quality of machined surface and increase of processing time. Therefore, in order to impr...During five-axis machining of impeller, the excessive local interference avoidance leads to inconsistency of cutter posture, low quality of machined surface and increase of processing time. Therefore, in order to improve the efficiency of five-axis machining of impellers, it is necessary to minimize the cutter posture changes and create a continuous tool path while avoiding interference. By using an MC-space algorithm for interference avoidance, an MB-spline algorithm for continuous control was intended to create a five-axis machining tool path with excellent surface quality and economic feasibility. A five-axis cutting experiment was performed to verify the effectiveness of the continuity control. The result shows that the surface shape with continuous method is greatly improved, and the surface roughness is generally favorable. Consequently, the effectiveness of the suggested method is verified by identifying the improvement of efficiency of five-axis machining of an impeller in aspects of surface quality and machining time.展开更多
There are significant effects of process parameters on internal qualities of bloom, and these process parameters are as follows. position and reduction amount, reduction distribution, reduction rate, and so on. Develo...There are significant effects of process parameters on internal qualities of bloom, and these process parameters are as follows. position and reduction amount, reduction distribution, reduction rate, and so on. Developing a control model is the key to apply soft reduction technology successfully. As the research object, 360 mm ×450 mm bloom caster in PISCO （Panzhihua Iron and Steel Co. ） has been studied, and the research method for control model of dynamic soft reduction has been proposed. On the basis of solidification and heat transfer model, the position of soft reduction and reduction distribution of each frame are determined according to the bloom temperature distribution and solid fraction in bloom center calculated. Production practice shows that the ratio of center porosity which is less than or equal to 1.0, increased to 97.27%, ratio of central segregation which is less than or equal to 0.5, increased to 80.91%, and ratio of central carbon segregation index which is more than or equal to 1.10, decreased to 4% with the applying model of dynamic soft reduction.展开更多
In order to solve the problem of weak power performance of vehicle equipped with continuously variable transmission(CVT) system working under transient operating conditions, a new CVT equipped with planetary gear mech...In order to solve the problem of weak power performance of vehicle equipped with continuously variable transmission(CVT) system working under transient operating conditions, a new CVT equipped with planetary gear mechanism and flywheel was researched, a design method of transmission parameter optimization was proposed, and the comprehensive matching control strategy was established for the new transmission system. Fuzzy controllers for throttle opening and CVT speed ratio were designed, and power performance and fuel economy of both vehicles respectively equipped with conventional CVT system and new transmission system wrere compared and analyzed by simulation. The results show that power performance and fuel economy of the vehicle equipped with new transmission system are better than that equipped with conventional CVT, thus the rationality of the parameter design method and control algorithm are verified.展开更多
Kinetic impact is an effective approach for studying and defending against asteroids.Impact missions have focused on asteroids with diameters larger than 100 m,whereas smaller missions have not been explored.Terminal ...Kinetic impact is an effective approach for studying and defending against asteroids.Impact missions have focused on asteroids with diameters larger than 100 m,whereas smaller missions have not been explored.Terminal guidance and control algorithms for small asteroids have received limited attention.China plans to conduct its first asteroid defense demonstration mission around 2025 on a 30-m-diameter asteroid.This paper presents the guidance and control algorithms for the terminal phase of this mission.The guidance formulas for impact missions are derived in this study using predictive and proportional guidance laws.Three maneuver criteria are proposed to determine the optimal timing for orbit correction,considering fuel consumption,impact accuracy,and computational cost.A continuous thrust control strategy was introduced to achieve incremental changes in velocity based on the relative motion of the impactor and target.The performance of the guidance and control algorithms was evaluated using Monte Carlo simulation,which demonstrated their effectiveness in handling uncertainties and achieving a high success rate.The results indicate that the proposed algorithm can be applied to future impact missions targeting small asteroids.展开更多
Recent advancements have shown that control strategies using Deep Reinforcement Learning(DRL)can significantly improve the management of HVAC control and energy systems in buildings,leading to significant energy savin...Recent advancements have shown that control strategies using Deep Reinforcement Learning(DRL)can significantly improve the management of HVAC control and energy systems in buildings,leading to significant energy savings and better comfort.Unlike conventional rule-based controllers,they demand considerable time and data to develop effective policies.Transfer learning using pre-trained models can help address this issue.In this work,we use imitation learning(IL)as a method of pre-training and reinforcement learning(RL)for fine-tuning.However,HVAC systems can vary depending on the location,building size,structure,construction materials and weather conditions.The diversity in HVAC control systems across different buildings complicates the use of IL and RL.Neural network weights trained on the source building cannot be directly transferred to the target building because of differences in input features and the number of control equipment.To overcome this problem,we propose a novel padding method to ensure that both the source and target buildings share the same state space dimensionality.Thus,the trained neural network weights are transferable,and only the output layer must be adjusted to fit the dimensionality of the target action space.Additionally,we evaluate the performance of an existing padding technique for comparison.Our experiments show that the novel padding technique outperforms zero padding by 1.37%and training from scratch by 4.59%on average.展开更多
Aircraft steering instability during the taxiing process sometimes occurs resulting from the unstable bifurcation phenomena of the nonlinear steering dynamic system,which may lead to severe accidents.In this study,the...Aircraft steering instability during the taxiing process sometimes occurs resulting from the unstable bifurcation phenomena of the nonlinear steering dynamic system,which may lead to severe accidents.In this study,the control parameter design of an aircraft nose wheel steering control system based on the control continuation method is proposed to reduce the number of unstable bifurcation points and enlarge the system stable region area in a certain parameter domain.Thus,the aircraft turning performance can be improved greatly.First,a nonlinear aircraft rollout dynamic model is constructed,and the aircraft ground steering bifurcation characteristics are obtained under the open-loop steering control system.Then,the bifurcation performances under three closed-loop nose wheel steering controllers based on the feedback control method are compared,and the control parameter of the quadratic nonlinear controller with a better bifurcation control effect is selected as a second bifurcation parameter to analyze the directional system stability via two-parameter bifurcation analysis.Further,the influence of a crosswind on the aircraft ground steering bifurcation performance is studied for various control parameter values.Then,the control effects of a traditional proportional-integral-derivative(PID)nose wheel steering control law and the designed feedback controller are compared and analyzed.Finally,a semi-physical experiment of the aircraft nose wheel steering system is carried out,and different control parameter values are selected for test verification,which can further verify the control effect of the designed nonlinear feedback controller.The results indicate that the feedback control method is unable to vary the system bifurcation types,but appropriate control parameter design can effectively shrink the system instability region and even eliminate the unstable Hopf bifurcation points under some specific working conditions,improving the aircraft ground turning stability remarkably from the perspective of the global parameter region.展开更多
Energy efficiency stands as an essential factor when implementing deep reinforcement learning(DRL)policies for robotic control systems.Standard algorithms,including Deep Deterministic Policy Gradient(DDPG),primarily o...Energy efficiency stands as an essential factor when implementing deep reinforcement learning(DRL)policies for robotic control systems.Standard algorithms,including Deep Deterministic Policy Gradient(DDPG),primarily optimize task rewards but at the cost of excessively high energy consumption,making them impractical for real-world robotic systems.To address this limitation,we propose Physics-Informed DDPG(PI-DDPG),which integrates physics-based energy penalties to develop energy-efficient yet high-performing control policies.The proposed method introduces adaptive physics-informed constraints through a dynamic weighting factor(λ),enabling policies that balance reward maximization with energy savings.Our motivation is to overcome the impracticality of rewardonly optimization by designing controllers that achieve competitive performance while substantially reducing energy consumption.PI-DDPG was evaluated in nine MuJoCo continuous control environments,where it demonstrated significant improvements in energy efficiency without compromising stability or performance.Experimental results confirm that PI-DDPG substantially reduces energy consumption compared to standard DDPG,while maintaining competitive task performance.For instance,energy costs decreased from 5542.98 to 3119.02 in HalfCheetah-v4 and from1909.13 to 1586.75 in Ant-v4,with stable performance in Hopper-v4(205.95 vs.130.82)and InvertedPendulum-v4(322.97 vs.311.29).Although DDPG sometimes yields higher rewards,such as in HalfCheetah-v4(5695.37 vs.4894.59),it requires significantly greater energy expenditure.These results highlight PI-DDPG as a promising energy-conscious alternative for robotic control.展开更多
The online-monitoring methods for insulation performance of current transformers of 330-750 kV substation are analyzed and compared.The effectiveness and availability of each method are discussed.Main features,advanta...The online-monitoring methods for insulation performance of current transformers of 330-750 kV substation are analyzed and compared.The effectiveness and availability of each method are discussed.Main features,advantages and disadvantages of each method and its corresponding standard are also described.展开更多
This paper addresses the attitude tracking control problem of a rigid spacecraft in the presence of the modeling uncertainty,external disturbance,and saturated control input by designing two robust att计ude tracking c...This paper addresses the attitude tracking control problem of a rigid spacecraft in the presence of the modeling uncertainty,external disturbance,and saturated control input by designing two robust att计ude tracking controllers.The basic controller is formulated using an integral sliding mode surface which is continuous and provides an asymptotic convergence rate for the closed-loop system.In this case,only the external disturbance with the prior information is considered.Then,to provide a finite time convergence rate and further improve the robustness of the control system under the unknown system uncertainty containing both the modeling uncertainty and external disturbance,a novel integral terminal sliding mode surface(ITSMS)is designed and associated w计h the continuous adaptive control method.Besides,a command filter is utilized to deal with the immeasurability problem within the proposed ITSMS and an auxiliary system to counteract the input saturation problem.Digital simulations are presented to verify the effectiveness of the proposed controllers.展开更多
In this paper,several equivalent forms of the well-known Brockett's second example system are firstly presented.The stabilization of the system is then treated in the fully actuated system approach.A simple contin...In this paper,several equivalent forms of the well-known Brockett's second example system are firstly presented.The stabilization of the system is then treated in the fully actuated system approach.A simple continuous time-invariant sub-stabilizing controller is designed,and the corresponding region of attraction is characterized.As a result,all trajectories of the system starting from the characterized region of attraction are driven exponentially to the origin.Since the region of attraction is very large,the designed sub-stabilizing controller can be directly useful in many practical situations.In cases where the initial values are indeed needed to be chosen out of the region of attraction,extremely simple pre-controllers can be designed,which drive the system trajectories into the designed region of attraction.A simulation of the designed control system is carried out to show the effect of the proposed approach.展开更多
基金This project is supported by National Natural Science Foundation of China (No.50675075).
文摘A novel pressure and vacuum continuous control system, which adopts a hybrid pump as pressure and vacuum source, is presented. The mathematical model of the system is developed. The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics, parameters and working points of the system. The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller. The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance, strong robustness and satisfactory adaptability to various system parameters. According to the results, system can successfully gain high accuracy and fast response signal. Also, the mathematical model of system is also testified by the experimental results.
基金supported by ANID BECAS/DOCTORADO NACIONAL 21230608supported by the Projects Fondecyt Nr.1221392,Anillo grant ATE230035,and Basal project FB0008(AC3E)supported by Fondecyt Nr.1230596 and Fondequip EQM200234.
文摘This paper proposes a continuous control set model predictive control(CCS-MPC)algorithm of a modular multilevel matrix converter(M3C)for low-frequency AC transmission(LFAC),via which the offshore wind farm(OWF)is integrated.The M3C is operated with a 16.7 Hz frequency at the OWF side and a 50 Hz frequency at the onshore grid side.The balance of the capacitor voltages and the regulation of circulating currents in the M3C are performed using the proposed CCSMPC algorithm,which is based on the online solution of a cost function with constraints.Simulation and experimental work(with a 5 kW M3C prototype)are provided,showing the performance of the LFAC system to operate with symmetrical and asymmetrical voltage dips,active and reactive power steps,and optimal limitation of currents and voltages using constraints.Unlike previous publications,the predictive control system in this paper allows seamless operation under balanced and unbalanced conditions,for instance,during asymmetrical voltage dips.
基金supported in part by the Australian Research Council Discovery Project(DP190101557)
文摘To handle input and output time delays that commonly exist in many networked control systems(NCSs), a new robust continuous sliding mode control(CSMC) scheme is proposed for the output tracking in uncertain single input-single-output(SISO) networked control systems. This scheme consists of three consecutive steps. First, although the network-induced delay in those systems can be effectively handled by using Pade approximation(PA), the unmatched disturbance cames out as another difficulty in the control design. Second, to actively estimate this unmatched disturbance, a generalized proportional integral observer(GPIO) technique is utilized based on only one measured state. Third, by constructing a new sliding manifold with the aid of the estimated unmatched disturbance and states, a GPIO-based CSMC is synthesized, which is employed to cope with not only matched and unmatched disturbances, but also networkinduced delays. The stability of the entire closed-loop system under the proposed GPIO-based CSMC is detailedly analyzed.The promising tracking efficiency and feasibility of the proposed control methodology are verified through simulations and experiments on Quanser's servo module for motion control under various test conditions.
基金The Scientific and Technology Researchand Development Program of Ministry of Railway of China(No.2008G005-A)the Fundamental Research Funds forthe Central Universities (No.SWJTU09BR042)
文摘On the basis of the theory of continuous compaction technology, we put forward the vibratory compaction value （VCV） index measured by a roller compactor, in order to evaluate the quality of continuously compacted subgrade. The relationships between the VCV index and the currently used indexes K30, Evd, Ev1 and Ev2, were explored by analyzing the experimental data collected from two test sections on the Beijing - Shanghai High-Speed Railway. The result shows that the VCV index has a linear relationship with the currently used indexes.
基金Key Science-Technology Foundation of Hunan Province, China (No. 05GK2007).
文摘Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.
文摘The full bridge zero voltage zero current switching （ FB-ZVZCS ） , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.
基金supported by the National Center for Scientific and Technical Research CNRST,Rabat,Morocco[grant number 17 UIZ 19].
文摘We study a new class of two-player,zero-sum,deterministic differential games where each player uses both continuous and impulse controls in an infinite horizon with discounted payoff.We assume that the form and cost of impulses depend on nonlinear functions and the state of the system,respectively.We use Bellman's dynamic programming principle(DPP)and viscosity solutions approach to show,for this class of games,the existence and uniqueness of a solution for the associated Hamilton-Jacobi-Bellman-Isaacs(HJBI)partial differential equations(PDEs).We then,under Isaacs'condition,deduce that the lower and upper value functions coincide,and we give a computational procedure with a numerical test for the game.
基金Work supported by the Second Stage of Brain Korea 21 ProjectsProject(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE) of Korea
文摘During five-axis machining of impeller, the excessive local interference avoidance leads to inconsistency of cutter posture, low quality of machined surface and increase of processing time. Therefore, in order to improve the efficiency of five-axis machining of impellers, it is necessary to minimize the cutter posture changes and create a continuous tool path while avoiding interference. By using an MC-space algorithm for interference avoidance, an MB-spline algorithm for continuous control was intended to create a five-axis machining tool path with excellent surface quality and economic feasibility. A five-axis cutting experiment was performed to verify the effectiveness of the continuity control. The result shows that the surface shape with continuous method is greatly improved, and the surface roughness is generally favorable. Consequently, the effectiveness of the suggested method is verified by identifying the improvement of efficiency of five-axis machining of an impeller in aspects of surface quality and machining time.
文摘There are significant effects of process parameters on internal qualities of bloom, and these process parameters are as follows. position and reduction amount, reduction distribution, reduction rate, and so on. Developing a control model is the key to apply soft reduction technology successfully. As the research object, 360 mm ×450 mm bloom caster in PISCO （Panzhihua Iron and Steel Co. ） has been studied, and the research method for control model of dynamic soft reduction has been proposed. On the basis of solidification and heat transfer model, the position of soft reduction and reduction distribution of each frame are determined according to the bloom temperature distribution and solid fraction in bloom center calculated. Production practice shows that the ratio of center porosity which is less than or equal to 1.0, increased to 97.27%, ratio of central segregation which is less than or equal to 0.5, increased to 80.91%, and ratio of central carbon segregation index which is more than or equal to 1.10, decreased to 4% with the applying model of dynamic soft reduction.
基金Project(2011BA3019)supported by the Chongqing Natural Science Foundation,China
文摘In order to solve the problem of weak power performance of vehicle equipped with continuously variable transmission(CVT) system working under transient operating conditions, a new CVT equipped with planetary gear mechanism and flywheel was researched, a design method of transmission parameter optimization was proposed, and the comprehensive matching control strategy was established for the new transmission system. Fuzzy controllers for throttle opening and CVT speed ratio were designed, and power performance and fuel economy of both vehicles respectively equipped with conventional CVT system and new transmission system wrere compared and analyzed by simulation. The results show that power performance and fuel economy of the vehicle equipped with new transmission system are better than that equipped with conventional CVT, thus the rationality of the parameter design method and control algorithm are verified.
文摘Kinetic impact is an effective approach for studying and defending against asteroids.Impact missions have focused on asteroids with diameters larger than 100 m,whereas smaller missions have not been explored.Terminal guidance and control algorithms for small asteroids have received limited attention.China plans to conduct its first asteroid defense demonstration mission around 2025 on a 30-m-diameter asteroid.This paper presents the guidance and control algorithms for the terminal phase of this mission.The guidance formulas for impact missions are derived in this study using predictive and proportional guidance laws.Three maneuver criteria are proposed to determine the optimal timing for orbit correction,considering fuel consumption,impact accuracy,and computational cost.A continuous thrust control strategy was introduced to achieve incremental changes in velocity based on the relative motion of the impactor and target.The performance of the guidance and control algorithms was evaluated using Monte Carlo simulation,which demonstrated their effectiveness in handling uncertainties and achieving a high success rate.The results indicate that the proposed algorithm can be applied to future impact missions targeting small asteroids.
基金financial support of TaighdeÉireann-Research Ireland under Grant No.18/CRT/6223.
文摘Recent advancements have shown that control strategies using Deep Reinforcement Learning(DRL)can significantly improve the management of HVAC control and energy systems in buildings,leading to significant energy savings and better comfort.Unlike conventional rule-based controllers,they demand considerable time and data to develop effective policies.Transfer learning using pre-trained models can help address this issue.In this work,we use imitation learning(IL)as a method of pre-training and reinforcement learning(RL)for fine-tuning.However,HVAC systems can vary depending on the location,building size,structure,construction materials and weather conditions.The diversity in HVAC control systems across different buildings complicates the use of IL and RL.Neural network weights trained on the source building cannot be directly transferred to the target building because of differences in input features and the number of control equipment.To overcome this problem,we propose a novel padding method to ensure that both the source and target buildings share the same state space dimensionality.Thus,the trained neural network weights are transferable,and only the output layer must be adjusted to fit the dimensionality of the target action space.Additionally,we evaluate the performance of an existing padding technique for comparison.Our experiments show that the novel padding technique outperforms zero padding by 1.37%and training from scratch by 4.59%on average.
基金supported by the National Natural Science Foundation of China(Grant Nos.52375102,52275114)the Spring Sunshine Program initiated by the Ministry of Education of China(Grant No.HZKY20220126)+3 种基金the China Postdoctoral Science Foundation Funded Project(Grant No.2021M691565)the Fundamental Research Funds for the Central Universities(Grant Nos.NS2023005,NJ2024003)the Aeronautical Science Foundation of China(Grant No.202000410520002)the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Aircraft steering instability during the taxiing process sometimes occurs resulting from the unstable bifurcation phenomena of the nonlinear steering dynamic system,which may lead to severe accidents.In this study,the control parameter design of an aircraft nose wheel steering control system based on the control continuation method is proposed to reduce the number of unstable bifurcation points and enlarge the system stable region area in a certain parameter domain.Thus,the aircraft turning performance can be improved greatly.First,a nonlinear aircraft rollout dynamic model is constructed,and the aircraft ground steering bifurcation characteristics are obtained under the open-loop steering control system.Then,the bifurcation performances under three closed-loop nose wheel steering controllers based on the feedback control method are compared,and the control parameter of the quadratic nonlinear controller with a better bifurcation control effect is selected as a second bifurcation parameter to analyze the directional system stability via two-parameter bifurcation analysis.Further,the influence of a crosswind on the aircraft ground steering bifurcation performance is studied for various control parameter values.Then,the control effects of a traditional proportional-integral-derivative(PID)nose wheel steering control law and the designed feedback controller are compared and analyzed.Finally,a semi-physical experiment of the aircraft nose wheel steering system is carried out,and different control parameter values are selected for test verification,which can further verify the control effect of the designed nonlinear feedback controller.The results indicate that the feedback control method is unable to vary the system bifurcation types,but appropriate control parameter design can effectively shrink the system instability region and even eliminate the unstable Hopf bifurcation points under some specific working conditions,improving the aircraft ground turning stability remarkably from the perspective of the global parameter region.
文摘Energy efficiency stands as an essential factor when implementing deep reinforcement learning(DRL)policies for robotic control systems.Standard algorithms,including Deep Deterministic Policy Gradient(DDPG),primarily optimize task rewards but at the cost of excessively high energy consumption,making them impractical for real-world robotic systems.To address this limitation,we propose Physics-Informed DDPG(PI-DDPG),which integrates physics-based energy penalties to develop energy-efficient yet high-performing control policies.The proposed method introduces adaptive physics-informed constraints through a dynamic weighting factor(λ),enabling policies that balance reward maximization with energy savings.Our motivation is to overcome the impracticality of rewardonly optimization by designing controllers that achieve competitive performance while substantially reducing energy consumption.PI-DDPG was evaluated in nine MuJoCo continuous control environments,where it demonstrated significant improvements in energy efficiency without compromising stability or performance.Experimental results confirm that PI-DDPG substantially reduces energy consumption compared to standard DDPG,while maintaining competitive task performance.For instance,energy costs decreased from 5542.98 to 3119.02 in HalfCheetah-v4 and from1909.13 to 1586.75 in Ant-v4,with stable performance in Hopper-v4(205.95 vs.130.82)and InvertedPendulum-v4(322.97 vs.311.29).Although DDPG sometimes yields higher rewards,such as in HalfCheetah-v4(5695.37 vs.4894.59),it requires significantly greater energy expenditure.These results highlight PI-DDPG as a promising energy-conscious alternative for robotic control.
基金Science and Technology Projects of Gansu Electric Power Company(No.52274514005W)
文摘The online-monitoring methods for insulation performance of current transformers of 330-750 kV substation are analyzed and compared.The effectiveness and availability of each method are discussed.Main features,advantages and disadvantages of each method and its corresponding standard are also described.
基金supported by the National Natural Science Foundation of China under Grant No.61174037
文摘This paper addresses the attitude tracking control problem of a rigid spacecraft in the presence of the modeling uncertainty,external disturbance,and saturated control input by designing two robust att计ude tracking controllers.The basic controller is formulated using an integral sliding mode surface which is continuous and provides an asymptotic convergence rate for the closed-loop system.In this case,only the external disturbance with the prior information is considered.Then,to provide a finite time convergence rate and further improve the robustness of the control system under the unknown system uncertainty containing both the modeling uncertainty and external disturbance,a novel integral terminal sliding mode surface(ITSMS)is designed and associated w计h the continuous adaptive control method.Besides,a command filter is utilized to deal with the immeasurability problem within the proposed ITSMS and an auxiliary system to counteract the input saturation problem.Digital simulations are presented to verify the effectiveness of the proposed controllers.
基金partially supported by Shenzhen Key Laboratory of Control Theory and Intelligent Systems under Grant No.ZDSYS20220330161800001the Science Center Program of the National Natural Science Foundation of China under Grant No.62188101the Major Program of National Natural Science Foundation of China under Grant Nos.61690210 and 61690212。
文摘In this paper,several equivalent forms of the well-known Brockett's second example system are firstly presented.The stabilization of the system is then treated in the fully actuated system approach.A simple continuous time-invariant sub-stabilizing controller is designed,and the corresponding region of attraction is characterized.As a result,all trajectories of the system starting from the characterized region of attraction are driven exponentially to the origin.Since the region of attraction is very large,the designed sub-stabilizing controller can be directly useful in many practical situations.In cases where the initial values are indeed needed to be chosen out of the region of attraction,extremely simple pre-controllers can be designed,which drive the system trajectories into the designed region of attraction.A simulation of the designed control system is carried out to show the effect of the proposed approach.
