Hello people, I am not sure if I am doing something wrong but the lin function for linearization of a non-linear function surrounding a given point is returning different results each time I call it. And sometimes the results affects the following calculations I am performing (like root locus, for example). Below I pasted the output of a same linearization call.
--> [A_body,B_body,C_body,D_body] = lin(sim_f16_body, X0_lin_body, U0); A_body A_body = -0.0209023 0.0519875 -32.14689 0.454861 -0.0403812 -1.0077261 -1.17722 456.03564 0. 0. 0. 1. 0.0002606 0.0026867 -0.0006798 -1.0747435 --> [A_body,B_body,C_body,D_body] = lin(sim_f16_body, X0_lin_body, U0); A_body A_body = -0.0201514 0.0538445 -32.14483 0.4545237 -0.0464131 -1.0221136 -1.1907031 456.02225 0. 0. 0. 1. 0.000417 0.0020722 -0.0011822 -1.0745151 --> [A_body,B_body,C_body,D_body] = lin(sim_f16_body, X0_lin_body, U0); A_body A_body = -0.0195838 0.0528224 -32.148353 0.4557581 -0.0495045 -1.0029337 -1.1827851 456.02261 -1.970D-16 0. -1.203D-16 1. 0.0000567 0.0028515 -0.0000533 -1.0754311 --> [A_body,B_body,C_body,D_body] = lin(sim_f16_body, X0_lin_body, U0); A_body A_body = -0.0196784 0.0539473 -32.148072 0.4556623 -0.050291 -1.0081099 -1.1862481 456.02452 1.263D-16 0. 0. 1. 0.0002898 0.0026783 -0.0003306 -1.075333 Also, I made an overplot of a simulation using the linear and non-linear systems, as shown below (blue curve is the non-linear system and the green curves are linear system from several lin executions). [image: image.png] The full code is here [1]. Anyone faced something like that? I'd appreciate any help. [1] https://github.com/fsandre/mcflight/blob/master/scripts/controls/nz/sim_body_stab_comparison.sce -- André
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