Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness t...Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.展开更多
The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loo...The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.展开更多
This paper considers the torque control problem for robots with flexible joints driven by electrical actuators. It is shown that the achievable closed-loop tracking bandwidth using PI torque controllers may be limited...This paper considers the torque control problem for robots with flexible joints driven by electrical actuators. It is shown that the achievable closed-loop tracking bandwidth using PI torque controllers may be limited due to transmission zeros introduced by the load dynamics. This limitation is overcome by using positive feedback from the load motion in unison with PI torque controllers. The positive feedback is given in terms of load velocity, acceleration and jerk. Stability conditions for designing decentralized PI torque controllers are derived in terms of Routh-Hurwitz criteria. Disturbance rejection properties of the closed system are characterized and an analysis is carried out investigating the use of approximate positive feedback by omitting acceleration and/or jerk signals. The results of this paper are illustrated for a two DoF （degrees of freedom） system. Experimental results for a one DoF system are also included.展开更多
基金National Science Fund for Distinguished Young Scholars (50825502)
文摘Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.
基金National Natural Science Foundation of China(No.51079107)Fundamental Research Funds for the Central Universities(No.5082022)
文摘The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.
基金supported by the AMARSI(Adaptive Modular Architecture for Rich Motor Skills,FP7-ICT-248311)Walk-Man(FP7-ICT-611832)European projects
文摘This paper considers the torque control problem for robots with flexible joints driven by electrical actuators. It is shown that the achievable closed-loop tracking bandwidth using PI torque controllers may be limited due to transmission zeros introduced by the load dynamics. This limitation is overcome by using positive feedback from the load motion in unison with PI torque controllers. The positive feedback is given in terms of load velocity, acceleration and jerk. Stability conditions for designing decentralized PI torque controllers are derived in terms of Routh-Hurwitz criteria. Disturbance rejection properties of the closed system are characterized and an analysis is carried out investigating the use of approximate positive feedback by omitting acceleration and/or jerk signals. The results of this paper are illustrated for a two DoF （degrees of freedom） system. Experimental results for a one DoF system are also included.
