An Integrated, Modular Simulation System for Education ... - Cal Poly

Time Invariant (LTI) systems in Matlab to obtain time histories to compare to each otherand the 6DOF simulation. The LTI systems used a unit step input while the 6 DOF modelused a 2 degree step input to scale the response so that they could be compared on a timehistory. The perturbation was kept small in the 6 DOF in an attempt to keep the dynamicsas close to the linearized system as possible, however the stepsize could still be largeenough to introduce the nonlinear effects for the non-linear model. Note that in all thegraphs the 6 DOF response is the dotted line. The first axis compared was the pitch in theshort period. Figure 20. shows the two state space models have very similar short period0Impulse ResponsePitch AngleAmplitude0.511.5State Space6 DOF22.50 0.5 1 1.5 2 2.5 3 3.5 4 4.5Time (sec.)Figure 20 Theta to Elevator - Short Period Longitudinal Dynamicswn and damping while the 6 DOF is less damped and higher frequency. The Long perioddynamics show similar differences between the state space models and the 6 DOF. Thewn is higher and less damped than the state space but the time constants are the same.The pitch angle response (figure 21.) is one where the state space models differed. Thenatural frequency of the 6 DOF model falls between the two state space models. The 6DOF model shown in Figure 18 has the correction for the forces mapped from the windaxis to the body axis. The effect of the mapping is to decrease the natural frequency andincrease the damping in the long period dynamics. Figure 21 shows the decrease innatural frequency from the Archangel model, and the decrease in damping compared to61