Active Steering
Encyclopedia
Active steering a type of power electric variable gear ratio power steering technology introduced by BMW
in 2003 first appearing on the redesigned 5-series which varies the degree that the wheels turn in response to the steering wheel. At lower speeds, this technology reduces the amount that the steering wheel must be turned -- improving performance in situations such as parking and other urban area traffic maneuvers. At higher speeds, the performance is such that the normal increased responsiveness from speed is avoided and it provides improved directional stability.
In a parking situation, the computer varies the ratio so that the steering wheel needs less than two turns to move the wheels lock to lock. As vehicle speeds increase, the steering ratio increases, so it takes larger movements of the steering wheel to move the wheels and that lessens the usually increasing vehicle response resulting from increased speed. Besides providing variable steering ratios, the computer is linked with the vehicle stability control system to aid in directional stability of the vehicle.
If the driver experiences a skid or slide because of poor road conditions, the Active Steering will react to information from the yaw rate sensor
s to modify the steering angle of the front wheels to stabilize the vehicle. This occurs much faster than the driver can react. If the Active Steering angle is not enough, then the Stability Control system intervenes to help as well.
Safety is one of the prime objectives of this system. Steering angle sensors on the steering column sense the direction the driver wants to go and the system only intervenes if the car is beyond stable limits. If an error or problem occurs in the electronics, the computer shuts down the operation of the electric motor, locking the ring gear of the planetary gear set and making it fixed ratio steering. Finally, if there is a problem inside the planetary gear unit, there is a second shaft that runs all the way through from the steering wheel shaft to the steering rack so that conventional steering is available.
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
in 2003 first appearing on the redesigned 5-series which varies the degree that the wheels turn in response to the steering wheel. At lower speeds, this technology reduces the amount that the steering wheel must be turned -- improving performance in situations such as parking and other urban area traffic maneuvers. At higher speeds, the performance is such that the normal increased responsiveness from speed is avoided and it provides improved directional stability.
In a parking situation, the computer varies the ratio so that the steering wheel needs less than two turns to move the wheels lock to lock. As vehicle speeds increase, the steering ratio increases, so it takes larger movements of the steering wheel to move the wheels and that lessens the usually increasing vehicle response resulting from increased speed. Besides providing variable steering ratios, the computer is linked with the vehicle stability control system to aid in directional stability of the vehicle.
If the driver experiences a skid or slide because of poor road conditions, the Active Steering will react to information from the yaw rate sensor
Yaw rate sensor
A yaw rate sensor is a gyroscopic device that measures a vehicle’s angular velocity around its vertical axis. The output is usually in degrees per second or radians per second. The angle between the vehicle's heading and vehicle actual movement direction is called slip angle, which is related to...
s to modify the steering angle of the front wheels to stabilize the vehicle. This occurs much faster than the driver can react. If the Active Steering angle is not enough, then the Stability Control system intervenes to help as well.
Safety is one of the prime objectives of this system. Steering angle sensors on the steering column sense the direction the driver wants to go and the system only intervenes if the car is beyond stable limits. If an error or problem occurs in the electronics, the computer shuts down the operation of the electric motor, locking the ring gear of the planetary gear set and making it fixed ratio steering. Finally, if there is a problem inside the planetary gear unit, there is a second shaft that runs all the way through from the steering wheel shaft to the steering rack so that conventional steering is available.
External links
- BMW Active Steering — BMW Sauber F1 Team driver Nick Heidfeld explains the innovative active steering technology.