Steering Control Module: Description and Operation

Servotronic Control





The Servotronic system provides steering assistance which is proportional to vehicle speed. It comprises the steering control module, and Servotronic valve forming part of the hydraulic control valve assembly.
The Servotronic valve is an electro-hydraulic device with a variable orifice, which varies in size according to the position of a needle valve. The needle valve is controlled by a solenoid in response to a variable current input from the steering control module. This regulates the fluid flow through the hydraulic control valve, which determines the amount of steering assistance.

Steering Control Module
The steering control module receives the vehicle speed from the instrument cluster and outputs the corresponding current values to the Servotronic valve. At parking speeds, when maximum assistance is required, the current is at its maximum value of 854 mA and the valve is closed. As the vehicle speed increases, the current progressively decreases to its minimum value of 15 mA and the valve opens in small increments. This results in an increasing amount of hydraulic pressure being applied to the reaction piston, making the steering feel more precise and responsive.
The rate of progression and shape of the characteristic between parking and high speed operation, is determined by the algorithm within the steering control module, and is matched to each suspension variant within the vehicle range.








Control Module Connections