The Signal Controller selects one of four driving modes, based on vehicle operation:

• High Speed Driving
• Suburban Driving
• Winding Road Driving
• City Driving

High speed driving requires the least amount of power assist. As the vehicle speed increases, the power assist decreases. During suburban driving the vehicle speed is slower but the steering input is usually more frequent. In this mode of operation the power assist generally increases.

For winding road driving the speed varies, but it is generally moderate. In this case, the steering input is frequent and the power assist is close to maximum. City driving is characterized by its low speed and frequent steering inputs. In this case, assist is at or near maximum. When the steering input stops the power assist gradually decreases.

Operating Conditions Above 6 MPH

The driving mode is determined by the steering frequency and the vehicle speed. The signal controller then selects a driving mode and determines an appropriate duty ratio for that mode. When the driving mode changes, the duty ratio is altered gradually (approximately 2.5 percent every 0.1 second). This provides a smooth transition from one steering mode to another, which prevents possible feedback to the steering wheel.

Operating Conditions Below 6 MPH

When there is NO steering input, the duty ratio is zero percent (no assist). However, with any steering input, the duty ratio immediately increases to 100 percent (maximum assist). The sub-fan turns off (if it was on) but turns back on again when the steering input ceases. With continued steering input, the duty ratio remains at 100 percent unless the vehicle speed exceeds 6 MPH. When the steering input ceases, the duty ratio reduces approximately 2.5 percent every 0.5 second. This prevents possible feedback to the steering wheel.