Electric Power Steering Apparatus

摘要

To provide an electric power steering apparatus capable of suppressing a vibration of an assist torque while keeping a steering feeling. A current command value is calculated by adding a torque differential compensation value depending on a differential value of a steering torque to a basic assist current command value calculated based on the steering torque and vehicle speed. In this situation, the torque differential compensation value is calculated to be smaller when the steering speed of a steering wheel falls within a specific steering speed region in which a resonance phenomenon easily occurs due to a disturbance vibration of a steering assist torque, in comparison with when the steering speed falls outside the specific steering speed region.

主权项

1. An electric power steering apparatus comprising:
a steering torque detection unit configured to detect a steering torque applied to a steering mechanism; a current command value calculation unit configured to calculate a current command value based on at least the steering torque detected by the steering torque detection unit; an electric motor configured to generate a steering assist torque to be applied to a steering shaft of the steering mechanism; a motor control unit configured to control driving of the electric motor based on the current command value; and a steering speed detection unit configured to detect a steering speed of a steering wheel, wherein the current command value calculation unit comprises: a basic assist current calculation unit configured to calculate a basic assist current command value based on the steering torque detected by the steering torque detection unit; a torque differential compensation value calculation unit configured to calculate a torque differential compensation value based on a differential value of the steering toque; and a correction unit configured to correct the torque differential compensation value calculated by the torque differential compensation value calculation unit when the steering speed detected by the steering speed detection unit falls within a specific steering speed region in which a resonance phenomenon occurs at a vehicle body due to a disturbance vibration of the steering assist torque to be smaller than the torque differential compensation value when the steering speed falls outside the specific steering speed region; and a specific steering speed setting unit configured to calculate a steering speed region in which a vibration frequency of the steering assist torque falls within a range of a natural frequency of the vehicle body based on a plurality of relational expressions corresponding to a plurality of occurrence factors of a vibration, respectively, each of the plurality of relational expressions indicating relationships between the vibration frequency of the steering assist toque and the steering speed, and to set the steering speed region as the specific steering speed region, and the current command value calculation unit is configured to calculate the current command value by adding the torque differential compensation value corrected by the correction unit to the basic assist current command value calculated by the basic assist current calculation unit.