Power Steering System Description And Function

General Information:

The VF 35 is equipped with rack assisted redundant electric power steering (R-EPS).

Power support is generated by an electric motor mounted directly on the steering rack.

R-EPS allows for the integration of ADAS functions, for example Park Assist or Lane Keep Assist, which creates the foundation for autonomous driving capabilities.

Basic Steering Functions:

Mechanical connection between steering column and wheel knuckles
To translate rotation of steering wheel to axial movement of rack
To translate input torque to rack force
To provide assistance force to reduce steering effort
To provide feedback torque to driver
To provide signal interface to communicate with other ECUs

Steering Components Overview:

Fig 1: Power Steering System Components Location

Courtesy of VINFAST, LLC

Basic Information on Steering Rack:

The VF 35 steering gear is a belt-driven EPS. An axially parallel electric motor leading to the steering rack transmits the steering-power assistance directly to the steering rack by means of a toothed-belt drive and a recirculating-ball mechanism. This system is distinguished by the precise responsiveness of the steering and immediate feedback from the road surface.

The steering angle sensor (SAS) is implemented into the steering gear assembly, and measures the steering angle and torque.

The electric powertrain supports the mechanical steering function and provides feedback for the driver. At the same time, it also makes safety and comfort functions (ADAS) possible.

Steering Rack R - EPS Assembly:

Courtesy of VINFAST, LLC

Technical Description:

R-EPS is designed as failsafe system by redundancy. It is equipped with one dual wound electric motor, two independent motor control units, and two torque sensors.

Schematic Diagram:

Courtesy of VINFAST, LLC

R-EPS - Electrically Controlled Functions:

Vehicle speed based steering assist
Active return
Active damping
Friction compensation
Inertia compensation
Temperature protection
Soft end stops
Shimmy compensation
Pull drift compensation
Selectable steering modes

R-EPS - ADAS Functions:

Lane keep assist - LKA
Lane departure warning - LDW
Lane centering control - LCC
Emergency lane keeping - ELK
Automatic lane change assist - ALCA
Highway pilot
Fully automated park assist
Remote parking
Summon mode