Yang Lingyu

A multivariable adaptive reconfigurable control method applied to the wing damaged aircraft

Focusing on the abrupt parameter variation of the aircraft dynamic characteristics brought by the wing damage, a multivariable adaptive reconfigurable control method has been studied. First the nonlinear 6DOF model of structural damaged aircraft is presented. The linearization process and the coupling between the longitudinal and lateral dynamics are studied, and the damaged aircraft dynamic model is denoted as a linear form with uncertain variations. And then the Multivariable Model Reference Adaptive Control (M-MRAC) method is introduced to compensate the abrupt variations in the state matrix, control matrix and the constant uncertainty. Finally NASA Generic Transport Model (GTM) is taken as an example and a typical case of left wing tip with 15% damage is considered. Three-channel attitude simulations are presented through comparing with PID control method. The results illustrate that the impact due to the parameter variations are significantly reduced, and the output tracks the desired trajectories rapidly and stably under uncertain damage.

Linear parameter-varying attitude controller design for a reusable launch vehicle during reentry

Considering the perturbation within a wide range of flight parameter (such as height, mach), and the strong uncertainty of aerodynamic and atmospheric parameter, a LPV(Linear Parameter-Varying) control method is studied for a RLV(Reusable Launch Vehicle) during reentry, which can make the controller designed envelope-oriented and obtain the self-scheduled ability. A standard LPV controller design process is given first, and the problem of LPV controllers large data volume is studied especially, for it will perform an exponential growth with the increase of order and number of LPV vertex models. Then the longitudinal/lateral controller separate design method based on coupling analysis and the LPV vertex models construct method based on model characteristics analysis are introduced, to decrease the data volume and make the LPV controller more applicable. At last, a LPV controller is designed for some RLV during reentry using the methods introduced above, and the 6-degree nonlinear simulation results demonstrate that the methods can reduce the data volume remarkably, while guarantee the controllers adaptability, tracking performance and robustness good enough.

A robust non-iterative method for similarity transform estimation

A non-iterative and robust method—direct outliers remove (DOR) is proposed, which efficiently estimates the similarity transform based on a data set containing both correct and incorrect correspondences. Unlike hypothesize-and-test methods such as Random Sample Consensus algorithm and its variants, DOR removes mismatches by exploring all the correspondences only once, using two invariant features of similarity transform. One is the angles between two vectors and the other is the length ratios of corresponding vectors. Given two images related by similarity transform, experiments demonstrate that all the mismatches introduced in matching stage could be detected and removed. Without losing computational accuracy, DOR is faster compared with several hypothesize-and-test algorithms, especially when the percentage of correct correspondence is relatively low.

The Nonlinear Iterative Closed Loop Configuration of Control Allocation for Aircraft with Multiple Control Effectors

The linear description and the inaccurate efficiency coefficients bring on the error of control allocation. The iterative closed loop configuration for control allocation was put forward and the nonlinear iterative method was introduced in the control allocation process. The convergence of this configuration was analyzed and simulated. The computational time was not increased and the method can solve the nonlinear control allocation problem. Results show that the iterative closed loop configuration can decrease the allocation error and enhance the robust of control allocation result to the efficiency coefficients.

Off-line self-scheduled robust predictive tracking control of linear parameter-varying systems

This paper presents a novel robust model predictive control (RMPC) method for a class of plants with fast time-varying parameters, strong uncertainty, and large operating envelope, which means the states of the plants vary widely. First, a linear parameter-varying model is built to describe model uncertainty and the large envelope. The model is of polytopic form augmented with integrals of tracking errors; the uncertainty of the model vertices is considered. Second, a set of RMPC controllers are designed for each polytope vertex sharing the same asymptotic stable invariant set. During the design, an additional stability constraint should be satisfied. With the additional constraint, global robust stability can be proven with Lyapunov theory. Lastly, a sample application of Rockwell Space Shuttles attitude controller is provided. Simulation results reveal that the tracking error of off-line self-scheduled RMPC controller is smaller than the RMPC controller, and it also shows a convergence trend, while the RMPC controllers does not.

Steady maneuver envelope evaluation for aircraft with control surface failures

A critical prerequisite of researches in the field of fault-tolerant flight control and planning is flight envelope evaluation. In order to be in compliance with path planning or trajectory generation under abnormal conditions, steady maneuver envelope is defined and evaluated. This envelope provides a complete set of equilibrium flight states under a given set of control and state limits awkward. We propose a numerical procedure using continuation technique to directly compute the boundary of the envelope, instead of trimming every flight on a grid of state and maneuver parameter points. The advantage of this approach is that it eliminates the time spent in the calculation of disequilibrium points and thus save the overall cost of evaluation. We present its application to several situations involving stuck aileron and rudder in this paper. In comparison with nominal condition, the size of the envelope decreases and the shape changes, owing to the saturation of corresponding key control variables. The open-loop stable region also shrinks as a consequence.