System Description: Description

• 4WAS system consists of two control units (4WAS front control unit and 4WAS main control unit) and 4WAS rear actuator components.
• 4WAS main control unit calculates front wheel and rear wheel angles via CAN communication based on the information of the steering angle sensor signal and vehicle speed signal.
• 4WAS main control unit controls 4WAS rear actuator according to the value calculated in 4WAS main control unit.
• It transmits the value that is calculated by 4WAS main control unit to 4WAS front control unit via 4WAS communication line (exclusive line of 4WAS system). 4WAS front control unit controls 4WAS front actuator based on the received demand.
• Self-diagnosis can be performed with CONSULT-III at each control unit to another (4WAS front control unit and 4WAS main control unit).
• It transmits/receives each signal from the following control unit via CAN communication line.
  COMPONENT DESCRIPTION
  
  

  Component parts	Function
  Steering angle sensor	It mainly transmits the following signals to 4WAS main control unit with CAN communication. Steering angle sensor signal
  ABS actuator and electronic unit (control unit)	It mainly transmits the following signals to 4WAS main control unit with CAN communication. Vehicle speed signal
  ECM	It mainly transmits the following signals to 4WAS main control unit with CAN communication. Engine speed signal
  Combination meter	It mainly transmits the following signals from 4WAS main control unit with CAN communication. 4WAS warning lamp signal

*: Communication line between 4WAS front control unit and 4WAS main control unit

Operation Description 

• The following performance is gained by controlling the best front wheel steering angle and the rear wheel steering angle.
  • The desirable vehicle movement is gained toward the driver's steering angle operation (steering angle).
  • The steering gear ratio changes according to the vehicle speed. The steering wheel operation (steering angle) load decreases.
    Fig 1: Front Steering Gear Ratio Graph

    Courtesy of NISSAN MOTOR CO., U.S.A.

When Driving at Low Speed 

• Increased front wheel angle gains the optimum front wheel angle by minimum steering wheel operation (steering angle).
  Fig 2: Front Steering Gear Ratio Graph - When Driving At Low Speed

  Courtesy of NISSAN MOTOR CO., U.S.A.

When Driving at Middle Speed 

• Increase the front steering angle while controlling to turn the rear wheel steering angle to the same steering angle side of steering wheel operation (steering angle). these operations make response better for vehicle yaw rate/lateral acceleration and also decrease the angle of sideslip.
  Fig 3: Front Steering Gear Ratio Graph - When Driving At Middle Speed

  Courtesy of NISSAN MOTOR CO., U.S.A.

When Driving at High Speed 

• Decrease the front wheel steering angle while controlling to turn the rear wheel steering angle to the same steering angle side of steering wheel operation (steering angle). these operations make car response better and vehicle stability higher.
  Fig 4: Front Steering Gear Ratio Graph - When Driving At High Speed

  Courtesy of NISSAN MOTOR CO., U.S.A.

Operation Feature 

4WAS FRONT ACTUATOR

• It is driven by 4WAS front motor.
• The front steering gear ratio (4WAS front actuator) changes with 4WAS front motor and the gear shaft when releasing the lock structure (4WAS front lock solenoid valve).
  NOTE: The lock structure is released when turning 4WAS lock solenoid valve ON.
• The lock structure (holder) absorbs force and applies the lock when applying strong force to 4WAS front actuator.
  CAUTION: Replace 4WAS front actuator when the system breaks down due to the excessive external force (rotating direction) applied to 4WAS front actuator.

4WAS REAR ACTUATOR

• It is driven by 4WAS rear motor.
• The irreversible efficiency performance hypoid gear secure the toe-stiffness of rear wheels against the road external force and keep the steering angle when system is malfunction.
• The power from the pinion gear (motor side) is transmitted, but the pinion gear does not rotate as caused by the gear mechanical characteristics (teeth angle) even though the ring gear (tire side) starts to rotate.