The Integrated Design Method Of Guidance And Control With Control Constraints

The missile guidance system and the flight-control system are critical parts relatedto whether it can fly successfully or achieve precision strikes.The design of integratedmissile guidance and autopilot has unparalleled advantages on the overall performanceaspects compared with the traditional design methods. So it is becoming a potential trendon developing high-performance missile. However, the coupling between the the guideand control channels are considered only in a small number of the existing literatureon integrated design. And these algorithms are more complex, di?cult to ensure therobustness of the system. The constraints on typical states( such as the angle of attack,sideslip angle, terminal impact angle) and input saturation do not take into account. Itgreatly limits the application in practice. This paper aims to consider the typical stateconstraints and input saturation on the design of integrated guidance and control system.Combined with backstepping method, dynamic surface control design, command filteringand adaptive control law, the integrated missile guidance and autopilot system based onthe three channels independence design idea and with angular constraints are studied inthe presence of unmodeled uncertainties and external disturbances. The main contents arestated as follows:A class of uncertain nonlinear systems in the presence of input saturation is consid-ered based on the robust adaptive control law design. Note that saturation function is notsmooth, but the backstepping approach requires all functions differentiable. In order tofacilitate the controller design, a smooth function is introduced and an auxiliary systemis constructed to augment the control system. Then the Nussbaum function is employedto compensate for the nonlinear term arising from the input saturation. In addition, thenonlinear system with lower triangular form consist of the unmatched uncertainties andthe matched uncertainty. The bounds of each nonlinearly parameterized uncertainty termsare supposed to be unknown. Besides adaptive control showing stability, transient perfor-mance is also derived to be explicit function. The proposed schemes can ont only handlethe systems with input saturation, but also be applicable to other nonlinearities which arebounded by a bounded smooth nonlinear function. Furthermore, it improves and enlargesthe nonlinear systems currently studied by the traditional backstepping approach.The integrated guidance and control system based on the three channels indepen-dence design idea can be abstracted into a class of uncertain strict-feedback nonlinearsystems. Motivated by the robust adaptive control approach above,the saturation of theactuators are further taken into account in the design of the integrated guidance and con-trol system for homing missiles. The method of handling input saturation is developedby considering the character of the integrated guidance and control system. In the end, itcan guarantee the stability of the missile in the presence of input saturation and unknownuncertainties. 6 degree-of-freedom simulation results by using the proposed method inthis paper are compared to the approach without considering saturation. Clearly, the per-formances are significantly improved by the proposed schemes. These results verify theeffectiveness of the proposed dynamic surface adaptive controllers in tackling with inputsaturation.In the sequel, based on the three channels independent design of integrated guidanceand control system, the problem of the input saturation and state constraints for homingmissiles are further considered. Command filters are exploited in the integrated guidanceand control design to deal with the state and actuator constraints. At the same time, thecommand filters can also avoid ’explosion of complex’ problem in backstepping. Afterthat, the dynamic characteristics of the actuators are limited for the integrated design.And auxiliary systems are introduced into the integrated guidance and control models toanalyze the constraint effect. An adaptive law is adopted to compensate unknown uncer-tainties in the varying-time system. A quadratic Lyapunov function is used to analyzestability. The proposed control scheme guarantees all the states of the missile to be uni-formly bounded and the line-of-sight angular rate converges to a small neighborhood ofthe origin. The nonlinear numerical simulations illustrate the effectiveness of the designedintegrated controller.Then, according to the work above, integrated missile guidance and autopilot in thepresence of input saturation and terminal angular constraints are studied. An integratedmodel of guidance and control loop in the pitch channel is first taken into account. Totackle with the problem of input saturation, robust adaptive algorithm is modified for theuncertainty time-varying system. Then the similar design procedures are applied to theyaw and roll channels. The final three-channel control algorithms constitute the designof integrated control with saturation constrain. Furthermore, adaptive filtered backstep-ping control is investigated for the integrated missile guidance and autopilot consideringthe input and state constraints. The 6-DOF nonlinear simulations have shown under theconstraint conditions the missile can fly stably and hit the target with the desired impactattitude angle, which demonstrates the feasibility of the proposed scheme.Finally, a novel backstepping control algorithm is proposed by adopting the non-linear continuous predictive approach. By adjusting the weighting matrix, the controlmagnitude in the initial stage can be reduced. The proposed approach is further appliedto the full integrated guidance and autopilot system. The numerical simulations of theproposed control approach compared with backstepping control approach are given forthe homing missile, which indicates the advantages of the continuous predictive approachdesign strategy. After then, the integrated guidance and control model for full statescoupling design are taken into account. The full integrated guidance and control model isuncertain MIMO time-varying nonlinear system,which satisfies the so-called block low-triangular structure. Based on the result mentioned above, adaptive block backsteppingcontrol methodology is proposed for the system with input saturation constraints.