NANO ePAS

STEERING

1.1.3 GENERAL DESCRIPTION

The

EPAS

(electrical power assist steering - column

Type) is made up of the following components

The system consists of the steering column (2) and a

servo unit (4). The steering torque is transmitted via

the intermediate shaft (5) with universal joints (6) to

the mechanical rack and pinion steering (7). Sensor

technology and torsion bar are next to the helical

gear drive in the servo unit (4). The helical gear drive

converts the support torque generated by the servo

motor (4) and transmits it to the intermediate shaft

(5). The support torque and operating torque of the

steering wheel generated are transmitted via the in-

termediate shaft (5) to the rack-and-pinion steering

(7) and then to the wheels. If the vehicle power sup-

ply or electrical supply fails, then the vehicle can still

be steered due to the mechanical connection be-

tween the steering wheel and the wheels being

steered.

In Nano EPAS speed base assistance feature is con-

figured which provides the different motor assistance

at different speeds which is called as boost curves.

FUNCTION

The torque sensor in servo unit registers the steering

torque and steering speed once the driver performs

a steering motion.

All data (including the vehicle signals such as engine

speed, vehicle speed, ignition signal) is transmitted

to the control unit (ECU). This then calculates the

necessary support torque and on the basis of the

calculated results, controls the servo motor (4).

A rotor position sensor is attached to the servomotor

(4). An index sensor is integrated in the torque sen-

sor.

The control unit (3) uses the integrated index sensor

and the rotor position sensor to calculate the steering

wheel’s steering angle.

Depending on the programming, the steeringwheel’s

angle signal can be sent back to the vehicle.

BLOCK DIAGRAM OF EPAS SYSTEM