The heat transfer features around the elliptic cylinder of axis ratio 4∶1 in crossflow were investigated experimentally within a wide range of Reynolds number. By means of heat-mass transfer analogy and the naphthale...The heat transfer features around the elliptic cylinder of axis ratio 4∶1 in crossflow were investigated experimentally within a wide range of Reynolds number. By means of heat-mass transfer analogy and the naphthalene sublimation technique, the local heat transfer distribution and the mean heat transfer coefficient are clarified. The result shows that the mean heat transfer coefficient is higher than that of a circular cylinder in most Reynolds number range regarded, and this superiority turns to be more significant with the increase of flow speed. Moreover, the effect of axis ratio on mean heat transfer coefficient was investigated tentatively. The oil-lampblack technique was employed to enable visualization of the flow pattern around the cylinder and on the cylinder wall.展开更多
For input saturated Hammerstein systems, the two-step predictive control strategy is adopted. The first step calculates the desired intermediate variable applying unconstrained linear modal and predictive control. The...For input saturated Hammerstein systems, the two-step predictive control strategy is adopted. The first step calculates the desired intermediate variable applying unconstrained linear modal and predictive control. The second step obtains the real-time control action by solving algebraic equation and desaturation. The case of immeasurable state is considered where the observer gain matrix is solved by Sylvester equation. The sufficient closed-loop stability condition is given and the designing and tuning algorithm for the domain of attraction is proposed. The theoretical results are validated by an example.展开更多
The problem of robustifying linear quadratic regulators （LQRs） for a class of uncertain affine nonlinear systems is considered. First, the exact linearization technique is used to transform an uncertain nonlinear sy...The problem of robustifying linear quadratic regulators （LQRs） for a class of uncertain affine nonlinear systems is considered. First, the exact linearization technique is used to transform an uncertain nonlinear system into a linear one and an optimal LQR is designed for the corresponding nominal system. Then, based on the integral sliding mode, a design approach to robustifying the optimal regulator is studied. As a result, the system exhibits global robustness to uncertainties and the ideal sliding mode dynamics is the same as that of the optimal LQR for the nominal system. A global robust optimal sliding mode control （GROSMC） is realized. Finally, a numerical simulation is demonstrated to show the effectiveness and superiority of the proposed algorithm compared with the conventional optimal LQR.展开更多
Optimal deterministic disturbances rejection control problem for singularly perturbed linear systems is considered. By using the slow-fast decomposition theory of singular perturbation, the existent and unique conditi...Optimal deterministic disturbances rejection control problem for singularly perturbed linear systems is considered. By using the slow-fast decomposition theory of singular perturbation, the existent and unique conditions of the feedforward and feedback composite control （FFCC） laws for both infinite-time and finite-time are proposed, and the design approaches are given. A disturbance observer is introduced to make the FFCC laws realizable physically. Simulation results indicate that the FFCC laws are robust with respect to external disturbances.展开更多
文摘The heat transfer features around the elliptic cylinder of axis ratio 4∶1 in crossflow were investigated experimentally within a wide range of Reynolds number. By means of heat-mass transfer analogy and the naphthalene sublimation technique, the local heat transfer distribution and the mean heat transfer coefficient are clarified. The result shows that the mean heat transfer coefficient is higher than that of a circular cylinder in most Reynolds number range regarded, and this superiority turns to be more significant with the increase of flow speed. Moreover, the effect of axis ratio on mean heat transfer coefficient was investigated tentatively. The oil-lampblack technique was employed to enable visualization of the flow pattern around the cylinder and on the cylinder wall.
文摘For input saturated Hammerstein systems, the two-step predictive control strategy is adopted. The first step calculates the desired intermediate variable applying unconstrained linear modal and predictive control. The second step obtains the real-time control action by solving algebraic equation and desaturation. The case of immeasurable state is considered where the observer gain matrix is solved by Sylvester equation. The sufficient closed-loop stability condition is given and the designing and tuning algorithm for the domain of attraction is proposed. The theoretical results are validated by an example.
基金supported by the Doctoral Foundation of Qingdao University of Science and Technology(0022330).
文摘The problem of robustifying linear quadratic regulators （LQRs） for a class of uncertain affine nonlinear systems is considered. First, the exact linearization technique is used to transform an uncertain nonlinear system into a linear one and an optimal LQR is designed for the corresponding nominal system. Then, based on the integral sliding mode, a design approach to robustifying the optimal regulator is studied. As a result, the system exhibits global robustness to uncertainties and the ideal sliding mode dynamics is the same as that of the optimal LQR for the nominal system. A global robust optimal sliding mode control （GROSMC） is realized. Finally, a numerical simulation is demonstrated to show the effectiveness and superiority of the proposed algorithm compared with the conventional optimal LQR.
基金This project was supported by the National Natural Science Foundation of China (60574023), the Natural Science Foundation of Shandong Province (Z2005G01), and the Natural Science Foundation of Qingdao City (05-1-JC-94).
文摘Optimal deterministic disturbances rejection control problem for singularly perturbed linear systems is considered. By using the slow-fast decomposition theory of singular perturbation, the existent and unique conditions of the feedforward and feedback composite control （FFCC） laws for both infinite-time and finite-time are proposed, and the design approaches are given. A disturbance observer is introduced to make the FFCC laws realizable physically. Simulation results indicate that the FFCC laws are robust with respect to external disturbances.
