Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-pa...Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.展开更多
To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary t...To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.展开更多
This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint cont...This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint controller using the fully actuated systems(FAs)approach to enable UUVs to asymptotically track target signals.Firstly,a novel error constraint fully actuated systems(ECFAs)approach is proposed by incorporating the tracking error dependent normalized function and barrier function along with time-varying scaling.Secondly,in order to deal with the model uncertainties of the UUVs,adaptive radial basis function neural networks(RBFNNs)is combined with the ECFAs approach.Then,a positive time-varying integral function is introduced to completely eliminate the effect of the residual effect caused by unknown dead-zone inputs,and it is proved that the trajectory tracking error converges to zero asymptotically based on the Lyapunov functions.Finally,the simulation results demonstrate the effectiveness of the designed adaptive controller.展开更多
In this paper,the prescribed error trajectory control is proposed for second-order fully actuated systems.At first,by taking advantage of the full-actuation property,an intermediate control law is designed such that t...In this paper,the prescribed error trajectory control is proposed for second-order fully actuated systems.At first,by taking advantage of the full-actuation property,an intermediate control law is designed such that the intermediate closed-loop system is in a very simple form.Then,by utilizing the initial conditions of system states and the prescribed error performance function,the intermediate control law is developed to force the tracking error of the system on the proposed sliding mode surface from the beginning.The overall control law is obtained by combining the aforementioned steps.It is revealed that under the designed control law,the tracking error of the closed-loop system converges to zero along the prescribed error trajectory.Finally,an example is provided to validate the effectiveness of the presented approach.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51575087,51205041)Science Fund for Creative Research Groups(Grant No.51321004)+1 种基金Basic Research Foundation of Key Laboratory of Liaoning Educational Committee,China(Grant No.LZ2014003)Research Project of Ministry of Education of China(Grant No.113018A)
文摘Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.
基金co-supported by the National Natural Scienc Foundation of China (No. 61172182)
文摘To control missile＇s miss distance as well as terminal impact angle, by involving the timeto-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory.An extended trajectory shaping guidance（ETSG） law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile＇s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.
基金supported in part by the National Natural Science Foundation of China under Grant Nos.62273297,62103353,61825304,and 6182500417in part by the Innovative Research Groups of the Natural Science Foundation of Hebei Province under Grant No.E2020203174+2 种基金in part by Hebei Innovation Capability Improvement Plan Project under Grant No.22567619Hin part by Youth Top Talent Project of Hebei Province under Grant No.HY2024050021in part by Post-graduate Innovation Fund Project of Hebei Province under Grant No.CXZZSS2023042。
文摘This paper focuses on the trajectory tracking control problem of unmanned underwater vehicles(UUVs)with unknown dead-zone inputs.The primary objective is to design an adaptive trajectory tracking error constraint controller using the fully actuated systems(FAs)approach to enable UUVs to asymptotically track target signals.Firstly,a novel error constraint fully actuated systems(ECFAs)approach is proposed by incorporating the tracking error dependent normalized function and barrier function along with time-varying scaling.Secondly,in order to deal with the model uncertainties of the UUVs,adaptive radial basis function neural networks(RBFNNs)is combined with the ECFAs approach.Then,a positive time-varying integral function is introduced to completely eliminate the effect of the residual effect caused by unknown dead-zone inputs,and it is proved that the trajectory tracking error converges to zero asymptotically based on the Lyapunov functions.Finally,the simulation results demonstrate the effectiveness of the designed adaptive controller.
基金This paper was supported by the Science Center Program of the National Natural Science Foundation of China under Grant No.62188101the Joint Funds of the National Natural Science Foundation of China under Grant No.U2013203.
文摘In this paper,the prescribed error trajectory control is proposed for second-order fully actuated systems.At first,by taking advantage of the full-actuation property,an intermediate control law is designed such that the intermediate closed-loop system is in a very simple form.Then,by utilizing the initial conditions of system states and the prescribed error performance function,the intermediate control law is developed to force the tracking error of the system on the proposed sliding mode surface from the beginning.The overall control law is obtained by combining the aforementioned steps.It is revealed that under the designed control law,the tracking error of the closed-loop system converges to zero along the prescribed error trajectory.Finally,an example is provided to validate the effectiveness of the presented approach.
