Vehicles often incorporate an electronic stability control system to assist a driver in maintaining control of the vehicle during certain driving conditions. Electronic stability control systems can augment or adjust the response of the vehicle to input from the driver depending on the detected circumstances. For example, where a surface becomes hazardous due to precipitation or other artificial condition, an electronic stability control system can manipulate the steering or braking systems, together with input from the driver, to retain control of the vehicle in a manner superior to driver input alone.
Electronic stability control systems receive input from a variety of sources, such as driver input from a brake pedal or steering wheel, as well as information regarding the vehicle, such as the rate of rotation of its wheels and/or derived travel speed. Electronic stability control systems can operate in more effective modes when supplied with accurate information regarding the vehicle. For example, when supplied with accurate travel speed information, an electronic stability control system can alter its adjustment of, among other things, the braking system, in response to detecting movement of the steering wheel by the operator. Thus, for a relatively slow-moving vehicle, little to no correction need be applied, whereas a relatively rapidly-moving vehicle will experience a greater amount of correction by the electronic stability control system.
Determining the forward speed of a vehicle from passive sensors can be difficult, however, as compared to detected input such as the operation of a steering device. For example, during situations of challenging operation, the vehicle can be moving in directions other than forward, such as during a turn. As sensors are typically placed so as to detect forward speed of a vehicle, determining the velocity of the vehicle can be difficult.
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