Mingzhe Hou

On-line optimal autonomous reentry guidance based on improved Gauss pseudospectral method

The on-line optimal autonomous reentry guidance of the hypersonic vehicle is proposed based on the improved Gauss pseudospectral method (IGPM). The autonomous reentry guidance requires the hypersonic vehicle can generate the optimal trajectory for the latest flight mission on line and track the new trajectory well under the uncertainty. These two problems are simplified into a nonlinear optimal control problem with nonlinear constraints. The IGPM is introduced to solve the above two problems. The trajectory has to change according to the flight mission and therefore the new optimal trajectory can be obtained by IGPM within about 10 s. The optimal feedback guidance law is used to track the reference trajectory to handle the uncertainty. In order to deal with the CPU time delay, which comes from optimizing the new trajectory, the new on-line optimal autonomous reentry guidance is depicted. Finally, the numerical simulation shows that the proposed autonomous guidance can generate optimal trajectory for the new flight mission and have a high tracking accuracy.

Global finite time stabilization of pure-feedback systems with input dead-zone nonlinearity

Abstract This paper is concerned with finite-time stabilization of a class of pure-feedback systems with dead-zone input. A systematic design procedure is established to derive the finite-time controller. Firstly, to circumvent the difficulties arising from the nonaffine properties, through a change of coordinates and incorporating mean value theorem, a system transformation technique is introduced to convert the original nonaffine system into an affine one. Then, based on the strengthened finite-time Lyapunov stability theorem as well as utilizing the bounds of dead-zone parameters, the finite-time stabilizer is explicitly constructed via backstepping design approach. It is proven that the designed controller can ensure all the states of the closed-loop system converge to zero in a finite time and maintain at zero afterwards. The proposed design framework is also extended to finite-time stabilization of uncertain pure-feedback systems and finite-time tracking control of pure-feedback systems. The effectiveness of the theoretical results are finally demonstrated by a numerical example and a realistic example.

Finite-time H∞ filtering for non-linear stochastic systems

This paper describes the robust H∞ filtering analysis and the synthesis of general non-linear stochastic systems with finite settling time. We assume that the system dynamic is modelled by Itô-type stochastic differential equations of which the state and the measurement are corrupted by state-dependent noises and exogenous disturbances. A sufficient condition for non-linear stochastic systems to have the finite-time H∞ performance with gain less than or equal to a prescribed positive number is established in terms of a certain Hamilton–Jacobi inequality. Based on this result, the existence of a finite-time H∞ filter is given for the general non-linear stochastic system by a second-order non-linear partial differential inequality, and the filter can be obtained by solving this inequality. The effectiveness of the obtained result is illustrated by a numerical example.

Adaptive control of uncertain pure-feedback nonlinear systems

ABSTRACT An adaptive control approach is proposed to solve the globally asymptotic state stabilisation problem for uncertain pure-feedback nonlinear systems which can be transformed into the pseudo-affine form. The pseudo-affine pure-feedback nonlinear system under consideration is with nonlinearly parameterised uncertainties and possibly unknown control coefficients. Based on the parameter separation technique, a novel backstepping controller is designed by adopting the adaptive high gain idea. The proposed control approach could avoid the drawbacks of the approximation-based approaches since no estimators are needed to estimate the virtual and the actual controllers. In addition, it could guarantee globally asymptotic state stabilisation even though there exist nonlinearly parameterised uncertainties in the considered system while comparing to the existing approximation-free approaches. A numerical and a realistic examples are employed to demonstrate the effectiveness of the proposed control method.

Full states coupling design of integrated guidance and control with input saturations

In this paper, adaptive block backstepping control has been investigated for the integrated missile guidance and autopilot with input constraints. The integrated guidance and control model for full states coupling design satisfies the so-called block low-triangular structure. Adaptive block backstepping control methodology is proposed for the MIMO time-varying nonlinear system with input saturation constraints. Considering the effect of the actuator constraint, a smooth function and a Nussbaum type function are introduced for convenience of controller design. The proposed control scheme guarantees the desired interception performance and the stability of the missile dynamics. The 6-DOF simulations have shown the feasibility of the proposed scheme.

To reduce initial control magnitude in backstepping: A continuous predictive approach

In this paper, a novel backstepping control algorithm is proposed by adopting the nonlinear continuous predictive approach. An optimization performance index containing the weighted tracking error and control input is introduced to obtain the actual control law. By adjusting the weighting matrix, the control magnitude in the initial stage can be reduced. In addition, when the weighting matrix imposing on input vector vanishes, the control law just coincides with the traditional backstepping control law. The proposed approach is further applied to the control of aircrafts. The simulation results show the effectiveness and advantage of our method.