Hello this is Devansh from Srm university,chennai. I am working on vehicle dynamics for our 2nd vehicle for FSAE 2016. We have been plotting force moment diagrams for our vehicle. We first created Cn-Cy diagram on Matlab in which for each delta and beta ranging from -5 to 5 in steps of 0.5 we iterated Ay based on slip angles and verticle loads (considering lateral load transfer with new Ay for each iteration). All the Fy data was imported from pacejka tire model.In Cn-Cy Ax=0.2
Then we plotted Cn-Ay in which we first assumed intial yaw rate and iterated yaw rate along with Ay similar to Cn-Cy but this time slip angles were calculated for each iteration(as yaw rate varies).
The Cn-Ay and Cn-Cy graphs looked almost similar. The constant steer lines of Cn-Ay are intersecting 0 yaw moment(Cn=0) line almost at max acceleration. Which makes this graph similar to Cn-Cy.Even when I change my CG location close to front axle in both the graphs the lines now intersect Cn=o before max Acc. which again makes both the graphs look similar.
I guess my understanding of the difference between Cn-Cy and Cn-Ay is not fully clear. In RCVD its mentioned that the most significant difference between Cn-Cy diagrams and Cn-Ay diagrams is that in Cn-Cy the total lateral force generated is not assumed to resist the acceleration of the vehicle mass. Instead, some portion could be used to resist an outside disturbance. whereas in Cn-Ay all lateral force created by the tires is used to hold the vehicle in steady state equilibrium without any outside disturbances.
Does this difference b/w the 2 diagrams change the way in which Ay iterations are done? Am I missing something or this behaviour of graph is acceptable?
I have attached respective images of the plotted graphsCn-Cy.jpgCn-Ay.jpgCn-Cy cg front.jpgCn-Ay cg front.jpg