STEERING 2 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 intermediate shaft (5) to the rack-and-pinion steering (7) and then to the wheels. If the vehicle power supply or electrical supply fails, then the vehicle can still be steered due to the mechanical connection between the steering wheel and the wheels being steered. In Nano EPAS speed base assistance feature is configured 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 sensor. 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:
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