Adams Assignments – Problem 4 – Steering geometry 2

A double wishbone suspension steering assembly was opened-

Hardpoint modification- In order to perform kingpin geometry optimization, the first task is to run the simulation using the original hardpoints specified in the adams. Based on the initial values and there results obtained, points are changed various times to achieve the desired targets. mention below are the initial/ original hardpoints which are checked with the hardpoints mentioned in our challenge,

Lower control arm outer, Upper control arm outer and wheel center hardpoints are changed. The outer hardpoints are the main reason for the steering related parameters(steering arm). The y-axis of the hardpoints were changed to reach the goal of kingping inclination angle, steer axis resultant offset and scrub radius. As we know its hard to control all the parameters at the same time, we start with KPI, scrub radius and steer axis offset and after achieveing these. we can move on to caster angle, moment arm and steer axis offset longitudinal. these are modified by changing the appropriate values in x-axis as these are viewed from side view geometry.
While doing this we also should monitor that if any changes are happening in KPI and scrub radius and SA
Even though the KPI and scrub radius were same, SA offset was hard to contain within our specified range as changing the X-axis of UCA and LCA also effected SA.
So, after various changes, the modified hardpoints are given below-

Coming to the plots,

Caster angle- The initial value of caster angle was 5.4 deg but the target required in 4 deg.. reducing the caster angle would effect the KPI by decreasing it. (we know positive caster means KP axis leaning to back of the car)

Caster moment arm- The target required is more than initial value. target=13mm and initial is 8.6mm. Increase in caster moment arm would lead to an increased in aligning moment of the car but would result in a greater masking if the breakaway point of the tire during limit handling conditons.

Kingpin inclination angle- it is changed from 10.6 to 13 deg. this will help in increasing self centering torque of the car and a greater tilt of the top of the top of kingpin towards inside of car.

Scrub radius- With the scrub radius decreased from 33 to 20. lower positive scrub radius gives more stable braking.

Steering axis offset resultant and longitudinal- With the longitudinal offset increase from -18mm and 0mm. increases the stability of car.

(the graphs are attached below in order)