Subsequent systems in the car yield to the pressure of electronics and automation like badly defended strongholds. The computer will decide about the work of the steering wheel and the power steering system.
Steering servos have long gained the function of changing the intensity of the power steering depending on the speed of the car. The idea of ​​such a solution is obvious: when the car is moving slowly, the support is strong, which is conducive to the comfort of using the car. And when it goes fast, the power steering wears off, because at high speeds, deep and nervous steering wheel turns are unnecessary.

Variable gear ratio
Designers would like to use the steering system, on par with the brake, to cooperate in stabilizing the track. Hence the idea for the steering gear 0 variable gear ratio, implemented by BMW, ZF i Boscha. The first serial car with such a system was BMW 5. This rack and pinion steering system is classic, hydraulic booster. Placement on the steering shaft (before the traditional rack) additional planetary gear, which allows the system to correct the position of the front wheels, without breaking the mechanical continuity between them and the steering wheel.
The input shaft of this planetary gear is the steering shaft, the output shaft is a regular pinion, rack and pinion steering gear. The housing of the planetary gear is a worm wheel, which can be rotated by an external electric motor or remain locked. In the latter case, the entire steering gear works like a classic fixed-ratio device. In turn when this casing is subject to rotation, the effective gear ratio varies, because the angles of rotation of the steering shaft and the rack pinion are not the same then.
At low car speeds, the planetary gear reduces the gear ratio of the entire system or, in other words, automatically increases the angle of the wheels, to facilitate maneuvering. As the car's speed increases, the total steering ratio increases smoothly, and at high speeds it is obviously the greatest, hence then a small turn of the wheels requires a large turn of the steering wheel. This helps in precise and smooth driving. The operation of these transmissions is supported by the aforementioned variable power steering. Everything is controlled by an electronic system, which retrieves the data used for the operation of ESP, i.e. the angle and speed of the steering wheel, wheel rotation and car speed etc..
The disadvantage of the BMW solution is its high cost, and sure, difficult for some drivers to accept, non-smooth operation of the steering system on the road, where you go once faster, and once slower.