Adams Assignments – Problem 4 – Steering geometry 2

Steps:

-First sla suspension opened

-Then parallel wheel simulation was performed

-then hardpoint table was changed

Original table

modified hard point table

-then x axis input variable is chosen for all the curves which is wheel travel

-then curves are plotted by choosing the y axis variable as required in the assignment

Curves:

Original caster angle=5.369 deg

Modified angle= approx. 4 degs

Effect:Reducing the caster angle value will reduce the steering effort but, at the same time will also reduce the straight-line stability

Original caster moment arm=8.58 mm

Modified caster moment arm=approx. 21 mm

Effect: increasing caster moment arm will decrease the useful feedback to the driver via the pneumatic rail ,because it will dilute it ,so the driver won’t be able to know when the car will lose grip

Original kingpin angle=10.085 deg

Modified kingpin angle=approx.. 13 deg

Effect: increasing kingpin inclination angle will increase the self centering effect by increasing the raising action of the car

Original steering axis offset=85.7 mm

Modified steering axis offset=approx. 85 mm

Effect: decreasing the resultant steering offset will reduce torque steer effects.

Original longitudinal steering axis offset=-18.74 mm

Modified longitudinal steering axis off set=0 mm

Effects: removing longitudinal offset from the suspension increases the trail and thus increases the straight-line stability

Original scrub radius=33.308 mm

Modified scrub radius =approx. 20 mm

Effects: reducing scrub radius will reduce road, torque and braking disturbances transferred to the steering ,so it will increase braking stability and it will reduce tyre wear. also, it will reduce torque steer

The answer to whether we can control all the above the parameters independently is no because all the parameters are interdependent on each other.

The above mentioned targets are achieved by changing the control arm's outer ball joint hard point. If we consider the side view, the X-hard point modification will change the caster angle, the caster moment arm and the steer axis longitudinal offset values. If we change the hard point for tuning any of the three values, the other two are affected.

Similarly, if we consider the front view, the Y-hard point modification of outer ball joint will change the kingpin inclination angle, scrub radius and the steer axis lateral offset. For a particular value of KPI inclination angle and scrub radius, there will be a particluar value of steer axis lateral offset. If we change the offset, the KPI angle may be same, but the scrub radius will change. Thus, in short if we change the hard point for tuning any of the three values, the other two are affected.

Thus, all the values are dependent on each other and we cannot tune each value independently.

Files:

https://drive.google.com/drive/folders/1yBZFfWqu85jOjYmtUIwtA96jOra2XYCe?usp=sharing