Robust gain-scheduled missile autopilot design based on multifrequency extended state observers

This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performance was attributed to multiple disturbances and uncertainties and the presence of hidden coupling terms,giving rise to a miss distance of greater than 20 m.To address these issues,the missile dynamics are decomposed into the angular rate dynamics as fast and the acceleration dynamics as slow subsystem using the singular perturbation theory to analyze a multi-time-scale property.Multifrequency extended state observers are then incorporated into the gain scheduling technique to attenuate disturbances,thus enhancing the control performance significantly.In the proposed engineering/practical design framework for missile autopilot,simple,conventional,and explicit tuning rules are provided.And the proposed control scheme can achieve input-to-state stability across the entire flight envelope under unknown but bounded disturbances.The advantages of the method over existing benchmark approaches are shown through nonlinear numerical simulations.This is supported by evidence from a new flight test result with a miss distance of only 2 m.

MULTI-CONTROLLER STRUCTURE OF SUPERMANEUVERABLE AIRCRAFT

This paper proposes a method of using multi controllers to control supermaneuverable aircraft. A nonlinear dynamic inversion controller is used for supermaneuver. A gain scheduled controller is used for routine maneuver. A switch algorithm is designed to switch the controllers. The flight envelopes of the controllers are different but have a common area in which the controllers are switched from one to the other. In the common area, some special boundaries are selected to decide switch conditions. The controllers all use vector thrust for lower velocity maneuver control. Unlike the variation structure theory to use a single boundary, this paper uses two boundaries for switching between the two controllers. One boundary is used for switching from dynamic inversion to gain scheduling, while the other is used for switching from gain scheduling to dynamic inversion. This can effectively avoid the system vibration caused by switching repeatedly at a single boundary. The method is very easy for engineering. It can reduce the risk of design of the supermaneuverable aircraft.

Motion stability and control of supercavitating vehicle with variable cavitation number

Cavitation number and speed are capable of variation during the motion of supercavitating vehicle underwater,for example,under the condition of accelerated motion stage and external disturbance.The dynamic model and control challenge associated with the longitudinal motion of supercavitating vehicle with variable cavitation number and speed have been explored.Based on the principle of cavity expansion independence the properties of cavity and the influence on planning force of body were researched.Calculation formula of efficiency of the fin was presented.Nonlinear dynamics model of variable cavitation number and speed supercavitating vehicle was established.Stabilities of the open-loop systems of different situations were analyzed.The simulations results of open-loop systems show that it is necessary to design a control method to control a supercavitating vehicle.A gain schedule controller with guaranteed H∞ performance was designed to stabilize the dive-plane dynamics of supercavitating vehicle under changing conditions.

基于参数依赖的直升机LPV鲁棒变增益控制

针对直升机飞行状态量在全飞行包线内动态变化的问题,设计了一种鲁棒变增益控制方法。在直升机非线性模型的基础上,研究了直升机前飞状态下的纵向线性参数变化(LPV)模型,并引入参考输入,将已建立的模型增广为仿射参数依赖LPV模型;运用鲁棒变增益仿射参数依赖Lyapunov函数的方法对该模型进行控制律设计,并验证了其稳定性;最后通过数值仿真验证了所设计控制器的实时性与鲁棒性。研究结果表明,该方法有效降低了单一Lyapunov函数所带来的保守性,可以用于直升机LPV模型的鲁棒控制与状态量跟踪。

Limit protection design in turbofan engine acceleration control based on scheduling command governor

A new limit protection method based on Scheduling Command Governor(SCG) is proposed for imposing multiple constraints on a turbofan engine during acceleration process. A Gain Scheduling Controller(GSC) is designed for the transient state control and its stability proof is developed using Linear Matrix Inequalities(LMIs). The SCG is an add-on control scheme which manages engine limits effectively based on reference trajectory optimization. Unlike the traditional min–max architecture with switching logic, the SCG method utilizes the Linear Parameter Varying(LPV) closed-loop model to form a prediction of future constraint violation and per instant solves a constraint-admissible reference within an approximate Maximal Output Admissible Set(MOAS).The influence of the variation of engine dynamic characteristics and equilibrium points during transient state control is handled by the design of contractive sets. Simulation results on a turbofan engine component-level model show the applicability and effectiveness of the SCG method. Compared to the traditional min–max method, the SCG method has less conservativeness. In addition,the design of contractive sets makes conservativeness tunable.