4WAS SYSTEM : System Description

4WAS system consists of two control units (4WAS front control unit and 4WAS main control unit), 4WAS front actuator 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).
INFINITY drive mode selector make it possible to change the steering characteristics of the front and rear wheels, and drive mode select switch is able to select STANDARD mode or SPORT mode.

SYSTEM DIAGRAM

Fig 1: 4WAS System Diagram

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

INPUT/OUTPUT SIGNAL

It transmits/receives each signal from the following control unit via communication line.

COMPONENTS SIGNAL CHART

Component parts

Control signal

4WAS main control unit

Transmits/receives the following signal to 4WAS main control unit via communication line⁽¹⁾.

4WAS system control signal

Steering angle sensor

Transmits the following signal to 4WAS main control unit via CAN communication line.

Steering angle sensor signal

ABS actuator and electronic unit (control unit)

Transmits the following signal to 4WAS main control unit via CAN communication line.

Vehicle speed signal

ECM

Transmits the following signal to 4WAS main control unit via CAN communication line.

Engine speed signal

Combination meter

Receives the following signal to 4WAS main control unit via CAN communication line.

4WAS warning lamp signal

A/C auto amp.

Transmits the following signal to 4WAS main control unit via CAN communication line.

Drive mode select switch signal

⁽¹⁾	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.
In SPORT mode, the steering characteristics of the front and rear wheels are switched to reduce load of steering wheel operation (steering angle) more than that in STANDARD mode and enable smooth motion.
NOTE:
- When driving at low speed: In SPORT mode, make front steering wheel operation (steering angle) increase more than that in STANDARD mode.
- When driving at high speed: In SPORT mode, make rear steering wheel operation (steering angle) decrease more than that in STANDARD mode.
  
  Fig 2: Steering Gear Ratio Versus Vehicle Speed 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 3: Steering Wheel Performance Graph (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 4: Steering Wheel Performance Graph (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 5: Steering Wheel Performance Graph (High Speed)

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

4WAS WARNING LAMP INDICATION CONDITION

4WAS system stops (error) when turning 4WAS warning lamp ON.

Turn 4WAS warning lamp ON when ignition switch turns ON from OFF for the purpose of lamp check. Then, turn 4WAS warning lamp OFF after the engine is started if system is normal.

4WAS WARNING LAMP REFERENCE CHART

Condition	4WAS warning lamp
Ignition switch OFF	OFF
Ignition switch ON	ON
After engine starts (system normal)	OFF
4WAS system malfunction	ON