The front steering wheels seem to be the simplest part of an automobile. All you need to do is turn the wheel in the desired direction and the car would follow. However, there is quite a complex scientific theory behind this functionality. This is where the Ackermann steering mechanism comes in. It ensures the accuracy of a turn by allowing varying physics to be applied to the rear and front tyre angles.
Before the implementation of Ackermann, the car manufacturers found it incredibly difficult to manufacture a vehicle that could turn with accuracy and steeply.
The Ackermann steering is one of the core components of cards that ensures better handling. While the other versions of electronic and hydraulic steering systems is not exactly the same as the first version of Ackermann steering the core principle of the technology remains the same.
History
Cars manufactured before 1818 suffered from the problem of rolling and slipping. This problem was resolved by Rudolf Ackermann’s principal in the year 1818. This was a revolutionary invention that fix a major problem in combustion engine automobiles.
What is the Ackermann steering mechanism?
In this mechanism, two wheels are connected by a rod such that they turn and different angles. Hence essentially the turning over need is not dependent on the other. There is one fixed length and three moving links in this mechanism resulting in the shape of a trapezium.
The four-bar linkage with the trapezoid platform leads to different slip angles of tires thereby allowing better vehicle handling.
Why this principle is needed
To understand this principle you need to understand how a wheel works. A wheel has two velocities. The first one is rotational velocity and the second one is translational velocity. While both these velocities are equal in magnitude their directions are opposite which results in them cancelling each other out. While turning, the rotational velocities direct is changing which may lead to a slip. In order to avoid slipping, it is necessary that the translational velocity also changes. However, the problem is that during turning, the inner wheel travels a very small distance which is why a very small amount of translational velocity is needed as compared to the outer wheel which needs a larger translational velocity. Hence in order to turn accurately both the wheels need varying translational velocities and different rotational velocity directions. This difficulty is overcome by the Ackerman principle as it ensures that the two wheels have different steering angles.
How does Ackermann steering work?
The steering column transfers the motion to the steering axis whenever the steering wheel is turning. The steering axis is in turn connected to the centralized moving link of the steering mechanism. The moving link is responsible for changing wheel directions by transferring motion to the link which is connected with the wheels. This is the basic working of Ackermann’s steering kinematics. The word kinematics is used here since there aren’t any external forces involved. The only force involved is the relative motion present between force links. The Ackerman steering geometry is such that the alignment of the front wheels is always in the direction of the common centre of the turning radius.
