Apparatus and method for generating steering wheel reaction torque in SBW system

1. An apparatus for generating steering wheel reaction torque in a steer-by-wire (SBW) system for a vehicle, the apparatus comprising:

an offset determiner determining an offset based on input factors;

a target reaction torque determiner determining target steering wheel reaction torque based on at least one of the input factors and the offset determined based on the input factors; and

a reaction torque generator generating steering wheel reaction torque based on the target steering wheel reaction torque,

wherein the reaction torque generator is restricted such that variations in the steering wheel reaction torque over time are lower than or equal to a preset slope value.

2. The apparatus according to claim 1 , wherein the input factors are a steering angle and a steering angular velocity.

3. The apparatus according to claim 1 , wherein the input factors are rack force and variations in the rack force over time.

4. The apparatus according to claim 1 , wherein the target reaction torque determiner determines the target steering wheel reaction torque on the basis of a reaction torque map that stores a relation of the steering wheel reaction torque to the input factors.

5. The apparatus according to claim 4 , wherein:

the steering wheel reaction torque has hysteresis characteristics; and

the offset determiner determines the offset based on the input factors such that the hysteresis characteristics of the steering wheel reaction torque on the reaction torque map represent a constant interval with respect to reference reaction torque within a steerable range.

6. The apparatus according to claim 1 , wherein a magnitude of the target steering wheel reaction torque is proportional to a speed of the vehicle.

7. A method for generating steering wheel reaction torque in an SBW system for a vehicle, the method comprising:

determining an offset based on input factors;

determining target steering wheel reaction torque on the basis of at least one of the input factors and the offset determined based on the input factors; and

generating steering wheel reaction torque based on the target steering wheel reaction torque,

generating of the steering wheel reaction torque is restricted such that variations in the steering wheel reaction torque over time is lower than or equal to a preset slope value.

8. The method according to claim 7 , wherein the input factors are a steering angle and a steering angular velocity.

9. The method according to claim 7 , wherein the input factors are rack force and variations in the rack force over time.

10. The method according to claim 7 , wherein the determining of the target steering wheel reaction torque comprises determining the target steering wheel reaction torque based on a reaction torque map that stores a relationship of the steering wheel reaction torque to the input factors.

11. The method according to claim 10 , wherein:

the steering wheel reaction torque has hysteresis characteristics; and

the determining of the offset comprises determining the offset determined based on the input factors such that the hysteresis characteristics of the steering wheel reaction torque on the reaction torque map represent a constant interval with respect to reference reaction torque within a steerable range.

12. The method according to claim 7 , wherein a magnitude of the target steering wheel reaction torque is proportional to a speed of the vehicle.