Steering Geometry

Steps:

-first Lca suspension is opened

-then steering simulation is performed

-the simulation is driven by the rack which is specified to have maximum travel of 85 mm in both directions ,in order to do that length has to be chosen from steering input

-then x-axis variable is chosen to be the steer angle

-then y-axis variable axis was chosen to be outside turn diameter

-then the outside turn diameter for the original configuration is plotted, it shows that original turning diameter is 9343 mm (9.343 m)

-then y axis is chosen to be the percent acherman

-then the percent acherman curve with steer angle is plotted,The curve shows that the maximum inner steering angle is 38.4 degs

-it also shows that at 20 degree inner tyre steering angle the acherman percentage is -15.9 (anti acherman)

-Tuning the steering to achieve target with the given constraints:

-the hpl_tierod_outer point was modified

original table

modified table

-then the steering simulation was re runned

-then outside diameter curve was plotted which showed the outside diameter of 9779 mmm (9.779 m) which is with in constraints limit

-then the percent acherman curve was plotted which shows that maximum inner tyre angle of 34.5 degrees which lies within the constraints limit

-it also shows that the target of 60% Ackerman at 20 degrees of inner tyre steer angle was achieved

c-factor calculation:

in order to calculate that we need to plot a curve between steering rack length and pinion angular displacement

-this can be done by selecting x- axis variable as pinion_displacement_from steering displacement

-then select y axis as rack_displacemen_front also from steering displacment

-this will result in curve plotted between pinion angular displacement and rack ravel,the curve shows that at 360 degrees the rack travelled 36 mm ,from that we deduce:

c factor=rack travel /360 degrees of pinion travel (1 rev)

c- factor = 36 mm/rev

-then in order to plot the steering ratio,we need to select steer angle as x-axis input variable

-then we need too select steering_wheel_angle_front from MDI_FRONT_STEERING as y-axis input variable

-this will result in a plotted curve between steer angle and steering wheel angle, so the slope of the curve is the steering ratio which is 26.735

-then the c factor was changed in order to reach the new target steering ratio of 16

-This can be done from the menu on the left hand side

-The reduction gear was modified from 0.174 to 0.1047

-Then the steering simulation was re-runned

-then c factor curve was plotted which showed a tuned c factor of 60 mm/rev

-then the tuned steering ratio curve was plotted which showed that the target of 16 steering ratio was achieved

-then the original and tuned steering ratio curves were plotted together (curve overlay)

-Then assembly was saved

Files:

https://drive.google.com/drive/folders/1czt7iEKzRW2emaFBL6KP2FXAA1WiP6mG?usp=sharing