Adams Assignments – Problem 4 – Steering geometry 2

1. For baseline hardpoints, these are the results:

These hardpoints were simulated for 1000 steps under parallel wheel travel simulation.

Caster angle: 5.37 deg (shown in image 1)

Caster Moment arm: 8.56 mm (shown in image 2)

KPI angle: 10.07 deg (shown in image 3)

Steer axis offset: 85.77 mm (shown in image 4)

Steer axis longitudinal offset: -18.74 mm (shown in image 5)

Scrub radius: 33.80 mm (shown in image 6)

2. Hard point tuning:

We need to find out which hardpoints require tuning to achieve the target in the question. To do that, I have created a CAD parametric sketch of the whole suspension using the given baseline hardpoints (shown in image 7). Using that 3D model, I tuned the hardpoints to achieve the targets in CAD first, which gave me an idea of the initial hardpoints. In the side view geometry, the caster angle, caster moment arm and steering offset longitudinal can be determined by changing the X-location of outer ball joints of the control arms. In the front view geometry, the Kingpin angle, steer axis offset (resultant), and scrub radius can be determined by tuning the Y-location of the outer ball joints. These hardpoints are exported over to Adams to do final tuning.

After 14 iterations, the hardpoints are given in image 8.

Caster angle: 4.03 deg (shown in image 9)

Caster Moment arm: 20.53 mm (shown in image 10)

KPI angle: 13.19 deg (shown in image 11)

Steer axis offset: 84.93 mm (shown in image 12)

Steer axis longitudinal offset: -0.0005 mm (shown in image 13)

Scrub radius: 19.18 mm (shown in image 14)

All these parameters are controlled through the control arm outer ball joints. Changing x-location will affect 3 parameters: caster angle, caster moment arm, and steer axis longitudinal offset at once. Changing Y-location will affect the other 3 parameters: KPI, scrub radius, and steer axis offset resultant. So, all these parameters cannot be controlled independently.