In comparison with progressive rack steering, the - steering is much higher in efficiency and has a harmonious progression
Function of a steering with a progressive rack:
The variable ratio rack is known for many years, car manufacturers and suppliers like Mercedes Benz, Ford and ZF have filed patent applications within the last century for pinion/rack systems with uniform pinion and with non uniform toothed rack.
Basically, the sinusodial progression curve, the changes in the progression and the characteristics of the system high friction affect the driving experience. In addition, the high pressure force in the yoke and the complex, the non linear load of the rack result in an additional introduced spin to the rack.
Today, only thanks to the most modern manufacturing technologies, the wear-resistance could be upgraded and is now tolerable.
The applications of electronics are over-steering the effect of a sudden change in the progressive curve, as well as the disharmony of the sinusodial progression. Thus, this system allows to fill in the need for progressive steering and equip vehicles with steering ratio of 2.7 to 2.3 turns from lock to lock, realizing a progression up to 25%.
Especially while driving slowly, a direct steering is very tiring because the slightest movement of the driver automatically has an effect on the steering and therefore it requires a high concentration to avoid weaving lines. Driving faster, the driver has to be more concentrated to stay on track
In contrast to variable toothed rack steerings, PSS offers with its logarithmic progression and the unchanging toothing a harmonious progression curve without abrupt changes. It allows different progression between 0.8 and 2.3 steering wheel turns (~ 400%). Especially in the central position, with PSS steering system, there is a secure and steady straight driving with a higher implemented ratio. This with very low wear, which reduces the need of power supply – no electronic over-steering needed at all!
While driving slow, the indirect steering is relaxing because slight movements from the driver are not indicating disturbing changes of direction. During faster driving, PSS steering offers, due to the indirect center position, more driving comfort and keeps you on a safe track.
The sequence (red) of the steering with the progressive rack shows well recognizable the short, progressive part with the strong decreasing ratio out of the middle position. (The uneven partition of the progressive rack is represented in general manner, the radius of the pinion is not changing.)
The pitch circles of the PSS steering (green, black and blue) are even and smooth.