An electric power steering apparatus includes a control section that includes a feed-back control section which sets a viscoelastic model as a reference model within a predetermined angle at front of a rack end. The feed-back control section includes a feed-back element to calculate a target rack displacement based on an input-side rack axial force and a control element to output an output-side rack axial force based on a position deviation between the target rack displacement and a rack displacement.

An electric power steering apparatus includes a control section that includes a feed-back control section which sets a viscoelastic model as a reference model within a predetermined angle at front of a rack end. The feed-back control section includes a feed-back element to calculate a target rack displacement based on an input-side rack axial force and a control element to output an output-side rack axial force based on a position deviation between the target rack displacement and a rack displacement.

An electronic control device controls an electronic power steering apparatus including a motor configured to assist steering of a steering wheel provided in a vehicle and a torque sensor configured to detect a steering torque applied to the steering wheel. The electronic control device includes: a torque current control unit that sets a first current command value to be supplied to the motor according to a value of the steering torque applied to the steering wheel; a differential control unit that calculates a torque differential value as a differential value of the steering torque and sets a second current command value according to the torque differential value and a rotation speed of the motor; and a command value calculation unit that calculates a motor current command value to be supplied to the motor based on the first current command value and the second current command value.

An electronic control device controls an electronic power steering apparatus including a motor configured to assist steering of a steering wheel provided in a vehicle and a torque sensor configured to detect a steering torque applied to the steering wheel. The electronic control device includes: a torque current control unit that sets a first current command value to be supplied to the motor according to a value of the steering torque applied to the steering wheel; a differential control unit that calculates a torque differential value as a differential value of the steering torque and sets a second current command value according to the torque differential value and a rotation speed of the motor; and a command value calculation unit that calculates a motor current command value to be supplied to the motor based on the first current command value and the second current command value.

An adaptive front steering system is capable of ensuring steering convenience and driving safety by changing a steering gear ratio in accordance with a driving situation of a vehicle. The adaptive front steering system is implemented as a new type of active front steering (AFS) system in which a hollow motor is applied to a steering column shaft, and a steering gear ratio is changed in accordance with a rotation direction and a rotation amount of a shaft of the hollow motor which is rotated together with an upper shaft.

An adaptive front steering system is capable of ensuring steering convenience and driving safety by changing a steering gear ratio in accordance with a driving situation of a vehicle. The adaptive front steering system is implemented as a new type of active front steering (AFS) system in which a hollow motor is applied to a steering column shaft, and a steering gear ratio is changed in accordance with a rotation direction and a rotation amount of a shaft of the hollow motor which is rotated together with an upper shaft.

Restriction values (upper limit and lower limit) for an assist control amount are set individually for each of state amounts including steering torque τ used to compute the assist control amount. A value obtained by summing such restriction values is set as a final restriction value for the assist control amount. Even though the assist control amount with an abnormal value is computed, the assist control amount is restricted to an appropriate value by the final restriction value. In addition, a transition is made from a primary assist control amount which is restricted to a secondary assist control amount computed separately from the primary assist control amount at the timing when a certain time elapses since the assist control amount is restricted. As the steering torque τ is increased, the speed of transition from the primary assist control amount to the secondary assist control amount is increased.

Restriction values (upper limit and lower limit) for an assist control amount are set individually for each of state amounts including steering torque τ used to compute the assist control amount. A value obtained by summing such restriction values is set as a final restriction value for the assist control amount. Even though the assist control amount with an abnormal value is computed, the assist control amount is restricted to an appropriate value by the final restriction value. In addition, a transition is made from a primary assist control amount which is restricted to a secondary assist control amount computed separately from the primary assist control amount at the timing when a certain time elapses since the assist control amount is restricted. As the steering torque τ is increased, the speed of transition from the primary assist control amount to the secondary assist control amount is increased.

The following description relates to a fault tolerant apparatus for an independent controlled steering in a four wheel system, particularly a fault tolerant apparatus for an independent controlled steering in a four wheel system which can stabilizes a vehicle body through actively adjusting a steering angle of a vehicle and a velocity of a vehicle according to a breakdown environment and a vehicle driving road environment. Further, a fault tolerant apparatus for an independent controlled steering in a four wheel system that may assist a safe driving environment by adjusting a turning function adoptively to a surrounding road environment.

Technical features are described for a steering system to compute a state flag value that is indicative of a vehicle motion state, such as an understeer or an oversteer condition. The steering system further generates a reference torque signal based on the state flag value, and generates a motor-assist torque signal based on the reference torque signal. The state flag value indicates the vehicle motion state in both a dynamic-state or a steady-state. Further, the steering system generates the reference torque signal based on the state flag value by blending a first rack force generated based on a vehicle-speed signal and motor angle, and a second rack force generated based on a motor torque and an input torque provided to a handwheel of the steering system.