Flight Performance And Reduced Order Model Of A Trajectory Correction Projectile With Decoupled Canards

The concept of trajectory correction projectile with decoupled canards(TCPDC)provides an innovative approach for the low-cost&guidance level-up of artillery projec-tiles and is growing up as a research hotspot.However,the application of TCPDC is accompanied with lots of problems,such as the coupled nonlinear dynamic model and asymmetric dual-spin configuration.Concerning flight and control,a dual-spin trajectory model is established and the dynamic response of TCPDC to a cont,rol input is inves-tigated based on numerical simulation and flight tests.In addition,the suitable flight control methods are evaluated in the dual-spin guidance,navigation and control system(Dual-spin GNC).With the body-axis-vector method,a dual-spin trajectory model is established and the analytic solution of yaw of repose is derived to investigate the dynamic response of a TCPDC to control input.Based on the rigid body trajectory,the 7th degree of freedom(DoF)is extended along a projectile's longitudinal axis with the body-axial vector method.Assumption of the sustainable flight stability and small yawing motion,an analytic solution of yaw of repose taking correction items into account is derived.Both theoretical and numerical results indicate that the response of TCPDC to a side force is out of phase and the phase shift ?? is approximately 180.The transition between stability,critical stable and divergence are obtained by visualising the angular motion.The diagram of control authority indicate that the shift of yaw is the source of trajectory correction and the impact response show the similar 180° phase shift as yaw of repose.In order to improve the aerodynamic module in dual-spin system,a quasi-steady model is set up.Combining the computational fluid dynamics(CFD)and wind tunnel test,an aerodynamic database including a variable of Mach and AoA is constructed.Results indicate that the drag of TCPDC is identical to the 43 drag law except for the 14%augmentation(The sliding effect of canards can make the reduction of range to 10V%).The cant angle has more effect on lift than drag and is proportional to roll moment.Decomposing the aerodynamics with the small perturbation,a quasi-steady model is obtained which can take both complex AoA and phase angle effects into account.In small AoA regime,a symmetric model can fit the drag of TCPDC with less than 3.3%residual,which implies the perturbation of canards on drag is ignorable.The lift keeps the sinusoidal feature while a secondary sinusoidal vibration arises along the curve of side force when ?p = 180°.A dynamic model for dual-spin channel,which is base on transient simulation and improved LuGre friction,enable trajectory to predict canards' roll motion.The compo-nents in transient simulation is build-up by several sliding interfaces and a sinusoidal roll rate is generated by interpolation to actuate canards.Parameters in the quasi-steady model are estimated by a lease square method(LSE)and the predictive residuals of ma-noeuvre and roll moment are less than 4 × 10-3.The improved LuGre friction regards the Column effect as a function of axial aerodynamic pressure and relates the dynamic part to the dual-spin motion.By identifying the roll rate in dynamic wind tunnel tests,the friction coefficients are captured.With aerodynamic and friction model set up,the working condition in dual-spin channel is evaluated.Regardless of the angular motion featured with high frequency,a reduced order model(ROM)predictive controller is assessed in dual-spin GNC system.The yaw of repose vector ?R is re-defined as hybrid product of axis and velocity vector and its analytic solution is derived,which leads to an approximate extraction of attitude in a low-cost navigation kit(only consists of velocity and spin rate).When this 4 states ROM is embedded into the dual-spin GNC system,the performance of impact predictive controller can be assessed.Results indicate that the ROM has a better accuracy of impact prediction than modified mass model(MPM).Even though the updating rate is lowers,ROM can generate an adaptive command related to ?? due to its own optimised capability and has a high efficiency than MPM.Both ROM and MPM methods can decrease the circular error probable(CEP)of delivery from 175m to less than 30m.To validate the dual-spin model,dynamic response and control authority,a series of flight tests including dual-spin measurement and manoeuvre capability are accomplished.Taking measured parameters around the muzzle as initial values,the referential trajecto-ries are calculated.Comparing with references,the dual-spin model shows the capability to predict canards' roll motion,along trajectory.The phase shift of dynamic response is validated around 180°,and the control authority of TCPDC is 600m at least.