Near Space Interceptor Research Articles

Nonlinear Model Predictive Control for Near-Space Interceptor Based on Finite Time Disturbance Observer

This paper proposes a novel nonlinear model predictive control design method based on the finite time disturbance observer (FTDO) and dynamic control allocation (DCA) algorithm for the near-space interceptor (NSI). First, the FTDO is introduced to estimate the mismatched system disturbance. The nonlinear model predictive control scheme based on the estimation value is proposed to obtain the virtual control command, and the mismatched disturbance can be effectively removed from the output channels of the NSI by designing a feed-forward disturbance compensation term with an appropriate compensation gain matrix. Moreover, a new DCA method is given to distribute the above virtual control command among the corresponding actuators (reaction jets and aerodynamic fins). Finally, numerical simulations illustrate that the proposed control scheme can track the command signal with high precision and have strong robustness against the mismatched disturbance.

Cooperative near-space interceptor mid-course guidance law with terminal handover constraints

A cooperative problem in mid-course guidance phase is addressed in this paper. For providing suitable initial conditions of successful terminal salvo attack, a novel finite-time cooperative mid-course guidance law with terminal handover constraints is proposed. Firstly, a three-dimensional guidance model of mid-course is decoupled in a planar line-of-sight frame as a two-point boundary value problem. The terminal handover constraints which can guarantee an ideal zero effort terminal engagement are proposed and analyzed. Secondly, the design of the cooperative mid-course guidance law is separated into two stages. The acceleration commands along the line-of-sight direction are developed based on the finite-time average-consensus protocol and super-twisting algorithm in the first stage. In the second stage, the model predictive static programming method is adopted to solve the two-point boundary value problem in line-of-sight frame with a known final time from first stage. Furthermore, sliding mode control theory is used in combination with model predictive static programming method to satisfy terminal handover constraints with bounded perturbation. Finally, numerical simulations of two four-interceptor cooperative scenario are carried out to verify the validity of the proposed cooperative guidance law. The simulation results reflect that all the four interceptors can reach their own predictive interception points with specific approach angles simultaneously.

Multi-model soft switching tracking control for near-space interceptor based on the disturbance observer

A disturbance observer–based multi-model soft switching tracking control design is proposed for the near-space interceptor. Initially, based on the Takagi–Sugeno modeling approach, a slow–fast loop soft switching model is employed to approximately describe the nonlinear dynamics of the near-space interceptor. Subsequently, a disturbance observer is constructed to estimate the unknown disturbance. Based on the disturbance observer, a descriptor system approach is proposed to solve the multi-model soft switching tracking control design problem. The suggested controller can not only ensure the stability of the closed-loop near-space interceptor system but also provide an upper bound of the cost function. Moreover, a robust least-squares weighted control allocation algorithm is employed to distribute the virtual control command among the redundant actuators (the aerodynamic fins and reaction jets). Finally, simulation results demonstrate the effectiveness of the proposed control scheme.

Integrated Guidance and Control Design for the Near Space Interceptor

Considering the guidance and control problem of the near space interceptor (NSI) during the terminal course, this paper proposes a three-channel independent integrated guidance and control (IGC) scheme based on the backstepping sliding mode and finite time disturbance observer (FTDO). Initially, the three-channel independent IGC model is constructed based on the interceptor-target relative motion and nonlinear dynamic model of the interceptor, in which the channel coupling term and external disturbance are regarded as the total disturbances of the corresponding channel. Then, the FTDO is introduced to estimate the target acceleration and control system loop disturbances, and the feed-forward compensation term based on the estimated values is employed to effectively remove the effect of disturbances in finite time. Subsequently, the IGC algorithm based on the backstepping sliding mode is also given to obtain the virtual control moment. Furthermore, a robust least-squares weighted control allocation (RLSWCA) algorithm is employed to distribute the previous virtual control moment among the corresponding aerodynamic fins and reaction jets, which also takes into account the uncertainty in the control effectiveness matrix. Finally, simulation results show that the proposed IGC method can obtain the small miss distance and smooth interceptor trajectories.

Integrated guidance and control based on block backstepping sliding mode and dynamic control allocation

A novel integrated guidance and control (IGC) design method based on the block backstepping sliding mode and extended state observer is proposed for the near space interceptor (NSI) with aerodynamic fins and reaction jets. Initially, the IGC model is employed by combining the interceptor-target relative motion model with the nonlinear dynamic of the NSI. Subsequently, the ESO is constructed to estimate the target acceleration and autopilot loop disturbance. Based on the estimated value and block backstepping sliding mode method, the IGC algorithm is given to obtain the virtual control moment. The stability of the closed-loop IGC system is also proven based on the Lyapunov theory. Moreover, a new dynamic control allocation algorithm is proposed to distribute the previously virtual control moment among the redundant actuators, while the actuator saturation and rate constraints are also taken into account. Finally, simulation results demonstrate that the proposed IGC algorithm can not only obtain a small miss distance, but also ensure the stability of the NSI dynamic.

Guidance Law for Near Space Interceptor based on Block Backstepping Sliding Mode and Extended State Observer

This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

Disturbance-Observer-Based Robust H∞Switching Tracking Control for Near Space Interceptor

A novel robust <TEX>$H_{\infty}$</TEX> switching tracking control design method with disturbance observer is proposed for the near space interceptor (NSI) with aerodynamic fins and reaction jets. Initially, the flight envelop of the NSI is divided into small subregions, and a slow-fast loop polytopic linear parameter varying (LPV) model is proposed, to approximate the nonlinear dynamic of the NSI, based on the Jacobian linearization and Tensor-Product (T-P) model transformation approach. A disturbance observer is then constructed, to estimate the modeled disturbance. Subsequently, based on the descriptor system method, a robust switching controller is developed, to ensure that the closed-loop descriptor system is stable with a desired <TEX>$H_{\infty}$</TEX> disturbance attenuation level. Furthermore, the outcome of the proposed switching tracking control problem is formulated as a set of linear matrix inequalities (LMIs). Finally, simulation results demonstrate the effectiveness of the proposed design method.

Optimal Controller for Near-Space Interceptor with Actuator Saturation

The saturation of the actuator impairs the response performance of the near space interceptor control system. A control system based on the properties of linear tracking system is designed for this problem. The properties are that the maximum value of the pseudo-Lyapunov function of the linear tracking control system do not present at the initial state but at the steady state, based on which the bounded stability problem is converted into linear tracking problem. The pseudo-Lyapunov function of the linear tracking system contain the input variables; the amplitude and frequency of the input variables affect the stability of the nonlinear control system. Designate expected closed-loop poles area for different input commands and obtain a controller which is function of input variables. The coupling between variables and linear matrices make the control system design problem non-convex. The non-convex problem is converted into a convex LMI according to the Shur complement lemma and iterative algorithm. Finally the simulation shows that the designed optimal control system is quick and accurate; the rationality of the presented design techniques is validated.