Variable Structure Control Algorithm And Its Applications In Missile Control System

The modern battlefield environment increasingly high demand for missile defensepenetration capability and combat effects, that means the missile with a strong mobile combatcapability is demanded. In order to abtain good mobile combat performance, the missile needto flight with a large attack angle. It makes the small perturbation linearization basicassumptions no longer hold[1], which is the basis of traditional control system design methodfor missile. Meanwhile, to make full advantage of the missile’s mobile overload capacity,Bank-to-Turn (BTT) control technology is used on missiles, it makes the missile lateralmovement and the longitudinal movement exist strong cross-coupling effect[2]. When themissile guidance system is designed, even the missile is viewed as a particle, the model of therelative motion between the missile and target is also strong nonlinear[3]. Above all, futuremissile system is a seriously coupling, strong nonlinear, serious interfered, rapid time-varying,complex multi-variable systems. So, Traditional missile guidance and control system designmethod (small perturbation theory and the coefficient of system frozen basic assumption) willno longer hold.Because of the unique advantages of Sliding Mode Variable Structure Control (SMC),such as the simplicity, independence of precise and when the parameter system perturbationand external interference and match exactly, the control system is invariant, therefore SMC isideally suited for missile guidance and control system design. But the chattering phenomenonin classic SMC system brings great difficulties for us to use classic SMC to design the missileguidance and control system[4]. In order to eliminate chattering phenomenon while maintainstrong robustness in the classic mode variable structure control, some scholars have proposedHigh-Order Sliding Mode Variable Structure Control (HOSMC) idea[5-12]. This article focus onthe research of High-Order Sliding Mode Variable Structure Control algorithm, and theHOSMC algorithm is used to design the missile guidance and control systems. Main works ofthe paper are as follows:1. The basic principle of the SMC algorithm is briefly described, and the reasons forchattering phenomenon in SMC system is detailedly analyzed. Several methods forsuppressing chattering phenomenon are introduced, then it is pointed out that these methodscan effectively suppres the system chattering, at the same time can reduce the system controlperformance.2. Basic concept and idea of the HOSMC is introduced and the reason why it caneliminate chattering phenomenon is analyzed, A typical HOSMC algorithm is introduced. To overcome the demanding deficiencies for controlled object of the typical HOSMC algorithm,a approximate high order sliding variable structure control algorithm is proposed.3. Aiming at the limitations of existing HOSMC algorithm, such as the algorithms arecomplex and the controlled object must satisfy some strict conditions, a new reachingcondition of second order sliding mode variable structure control system is proposed. And anew design method of second order sliding mode variable structure control algorithm basedon the reaching condition is proposed. Under the reaching conditions, the robustness of thecontrol system and the system phase trajectory could asymptotic converge at the sliding modeis proved by constructing Lyapunov function. Combined with the theory of ordinarydifferential equations, the system phase trajectory is proved converge at the sliding mode infinite time. Then an overview of the definition for linear and sliding terminal sliding mode isgiven. The simulation results demonstrate the correctness and effectiveness of the proposedcontrol algorithm which is based on the linear and sliding integral sliding mode according tothe proposed sliding mode reaching condition.4. Atmosphere flight tactical missile guidance and attitude control mathematical model isbuilt, and the missile guidance law which is based on the proposed reaching condition. Inorder to simplify the design process of the missile attitude control system, the complexmissile attitude motion equation is decomposed into three simple subsystem, including thepitching channel subsystem, the yaw channel subsystem and the roll channel subsystem. Thecoupling items among three channels is equivalently viewed as external disturbance. Whenthe coupling items among the three channels is bounded, the controllers the three subsystembased on the proposed reaching condition is given separately. Simulation results show that theproposed method is correct and effective, and can eliminate the chattering effectively of themissile system.