Spinning gasodynamic projectile system identification experiment design

Abstract

Purpose The purpose of this paper is to present the methodology that was used to design a system identification experiment of a generic spinning gasodynamic projectile. For this object, because the high-speed spinning motion, it was not possible to excite the aircraft motion along body axes independently. Moreover, it was not possible to apply simultaneous multi-axes excitations because of the short time in which system identification experiments can be performed (multi-step inputs) or because it is not possible to excite the aircraft with a complex input (multi-sine signals) because of the impulse gasodynamic engines (lateral thrusters) usage. Design/methodology/approach A linear projectile model was used to obtain information about identifiability regions of stability and control derivatives. On this basis various sets of lateral thrusters’ launching sequences, imitating continuous multi-step inputs were used to excite the nonlinear projectile model. Subsequently, the nonlinear model for each excitation set was identified from frequency responses, and the results were assessed. For comparison, the same approach was used for the same projectile exited with aerodynamic controls. Findings It was found possible to design launching sequences of lateral thrusters that imitate continuous multi-step input and allow to obtain accurate system identification results in specified frequency range. Practical implications The designed experiment can be used during polygonal shooting to obtain a true projectile aerodynamic model. Originality/value The paper proposes a novel approach to gasodynamic projectiles system identification and can be easily applied for similar cases.

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…In the study, the output vector consists of all longitudinal and lateral motion states y = x lon x lat T . Stability and control derivatives were the estimated parameters and their initial values Θ Θ Θ 0 were obtained from previous studies [9]. For model structure determination, backward elimination method was used.…”

“…This makes full flight simulator development very costly, because the data cannot be gathered during scheduled flights (specific experiments are required) and the dedicated flight tests last multiple flight hours [3]. Despite the high cost in aeronautics, the system identification is widely used for airplanes [4,5], rotorcrafts [6,7], projectiles [8,9] or pilot modelling [10,11] as it delivers very accurate mathematical models of these objects.…”

Study of Model Uncertainties Influence on the Impact Point Dispersion for a Gasodynamicaly Controlled Projectile

“…The correction thruster must be ignited so that the resultant thrust force was in the direction of the desired lateral displacement [35,36], which means that the absolute value of the difference between the error phase γ and thruster azimuth angle Φ i,j diminished by the control prediction times τ d and τ sk multiplied by the roll angular velocity was lower than some limit value γ t .…”