Active steering first appeared in the BMW 5 series in 2003. According to BMW, “Active Steering offers precision, agility, and comfort in every driving situation.” What does that mean for the driver? It means that active steering will enhance your car’s driving performance when you are driving in city traffic, when you are parking your car, or when you are turning through a sharp curve. When you are driving at lower speeds the steering ratio becomes more direct, meaning that the wheels will turn more with less effort. At higher speeds the
Active Steering system adjusts the ratio to become less direct. As a result the wheels are less responsive to small steering adjustments. This prevents oversteering at high speeds when it could potentially threaten the stability of your car.
How does active steering work? At the heart of the Active Steering system is the planetary gear set that is integrated into the steering column. There is a motor in the joint that adjusts the front wheel’s steering angle. A speed sensor passes information to the Active Steering system so that the front wheels can be adjusted according to the speed that you are traveling.
Remember our blog on Electronic Stability Control? Well, Active Steering and ESC work together in most modern cars. If the Electronic Stability Control system senses that the vehicle is becoming unstable at any point while you are driving, ESC sends a message to Active Steering to help the vehicle regain stability. If your vehicle experiences an unsafe yaw, Active Steering can almost instantly increase the angle of the steering wheels. It can do this, “faster than even the most expert driver.”
The point of Active Steering is to increase the safety of your vehicle. At no point does Active Steering interrupt the direct connection between the steering wheel and the front wheels. Even if there is total electronic failure in your car, the driver will always be able to maintain control. At the first sign of trouble, an adaptation mechanism shuts off Active Steering by locking the ring gear of the planetary gear set, which makes the gear set a fixed ratio. If there is ever a problem inside the planetary gear set, there is an alternate shaft that runs from the steering wheel shaft to the steering rack that gives the driver the ability to implement conventional steering.
