[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Continuous nonsingular terminal sliding mode control for systems with mismatched disturbances

This study addresses a fixed-time terminal sliding-mode control methodology for a class of second-order non-linear systems in the presence of matched uncertainties and perturbations. A newly defined non-singular terminal sliding surface is constructed and a guaranteed closed-loop convergence time independent of initial states is derived based on the phase plane analysis and Lyapunov tools. The simulation results of a single inverted pendulum in the end are included to show the effectiveness of the proposed methodology.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-cta.2014.0202

Non-singular fixed-time terminal sliding mode control of non-linear systems

Finite-time consensus for second-order multi-agent systems with disturbances by integral sliding mode

This paper considers actuator redundancy management for a class of overactuated nonlinear systems. Two tools for distributing the control effort among a redundant set of actuators are optimal control design and control allocation. In this paper, we investigate the relationship between these two design tools when the performance indexes are quadratic in the control input. We show that for a particular class of nonlinear systems, they give exactly the same design freedom in distributing the control effort among the actuators. Linear quadratic optimal control is contained as a special case. A benefit of using a separate control allocator is that actuator constraints can be considered, which is illustrated with a flight control example.

Resolving actuator redundancy: optimal control vs. control allocation

The attitude control of quadrotor unmanned aerial vehicle (UAV) is investigated. The aim of this paper is to develop a continuous multivariable attitude control law, which drives the attitude tracking errors of quadrotor UAV to zero in finite time. First, a multivariable super-twisting-like algorithm (STLA) is proposed for arbitrary order integrator systems subject to matched disturbances. A discontinuous integral term is incorporated in the control law in order to compensate the disturbances. A rigorous proof of the finite time stability of the close-loop system is derived by utilizing the Lyapunov method and the homogeneous technique. Then, the implementation of the developed method in an indoor quadrotor UAV is performed. The remarkable features of the developed algorithm includes the finite time convergence, the chattering suppression and the nominal performance recovery. Finally, the efficiency of the proposed method is illustrated by numerical simulations and experimental verification.

Multivariable Finite Time Attitude Control for Quadrotor UAV: Theory and Experimentation

The flight control problem of a flexible air-breathing hypersonic vehicle is presented in the presence of input constraint and aerodynamic uncertainty. A control-oriented model, where aerodynamic uncertainty and the strong couplings between the engine and flight dynamics are included, is derived to reduce the complexity of controller design. The flexible dynamics are viewed as perturbations of the model. They are not taken into consideration at the level of control design, the influence of which is evaluated through simulation. The control-oriented model is decomposed into velocity subsystem and altitude subsystem, which are controlled separately. Then robust adaptive controller is developed for the velocity subsystem, while the controller which combines dynamic surface control and radial basis function neural network is designed for the altitude subsystem. The unknown nonlinear function is approximated by the radial basis function neural network. Minimal-learning parameter technique is utilized to estimate the maximum norm of ideal weight vectors instead of their elements to reduce the computational burden. To handle input constraints, additional systems are constructed to analyze their impact, and the states of the additional systems are employed at the level of control design and stability analysis. Besides, “explosion of terms” problem in the traditional backstepping control is circumvented using a first-order filter at each step. By means of Lyapunov stability theory, it is proved theoretically that the designed control law can assure that tracking error converges to an arbitrarily small neighborhood around zero. Simulations are performed to demonstrate the effectiveness of the presented control scheme in coping with input constraint and aerodynamic uncertainty.

Robust adaptive dynamic surface control design for a flexible air-breathing hypersonic vehicle with input constraints and uncertainty

Optimal guidance for reentry vehicles based on indirect Legendre pseudospectral method

The real-time reentry trajectory and attitude coordination control for a reusable launch vehicle (RLV) is a very important and challenging problem. There are many aspects that make the research appealing, such as being able to autonomously replan a new trajectory onboard when the landing site is changed. In order to achieve the goal, an integrated guidance and control architecture is proposed in this paper. First, the offline reentry trajectory is designed based on adaptive Gauss pseudospectral method. Then, the obtained trajectory is used as the initial value guess for real-time reentry trajectory optimization. As a result, the pseudospectral-based optimal feedback reentry guidance is achieved via successive real-time optimal open-loop control which ensures that the guidance system has sufficient robustness for initial reentry perturbations. Furthermore, a multitime scale smooth second-order sliding-mode controller with disturbance observer is proposed to ensure the finite-time reentry attitude tracking despite the model parameter uncertainties and unknown external disturbances. Finally, two representative simulation tests are carried out to demonstrate the effectiveness of the proposed integrated guidance and control architecture for six-degree-of-freedom RLV.

Real-Time Trajectory and Attitude Coordination Control for Reusable Launch Vehicle in Reentry Phase

The finite-time attitude control of quadrotor unmanned aerial vehicles (UAVs) subject to external disturbances with unknown bound is investigated in this paper. First, an adaptive multivariable finite-time stabilizing control algorithm for second-order multivariable systems is developed based on the improved supertwisting and the equivalent control algorithms. Furthermore, the finite-time stability conditions are derived via the Lyapunov technique. The remarkable feature of the developed algorithm is to eliminate the overestimation of the control gains without loss of the sliding motion. Then, the proposed algorithm is applied for quadrotor UAVs to solve the finite-time attitude-tracking problem. Finally, a comparison of the proposed multivariable algorithm with its scalar counterpart is presented and validated both by simulation and experiment results.

Qun Zong

Papers

Multivariable Finite Time Attitude Control for Quadrotor UAV: Theory and Experimentation

Robust adaptive dynamic surface control design for a flexible air-breathing hypersonic vehicle with input constraints and uncertainty

Optimal guidance for reentry vehicles based on indirect Legendre pseudospectral method

Real-Time Trajectory and Attitude Coordination Control for Reusable Launch Vehicle in Reentry Phase

Adaptive Finite-Time Attitude Tracking of Quadrotors With Experiments and Comparisons