The problems encountered when reading the relevant information. ABS needs to determine the slip rate of the wheel in order to combine the other parameters to determine whether to increase, maintain or reduce the brake fluid pressure. The angular velocity of the wheel is easy to determine, but how is the accuracy of the wheel's speed measured in the case of a slip rate?
Fuzzy estimator method is a common method. Its reasoning rules according to the different driving conditions, the size of the sensor error to determine, according to the sensor error, the above five estimates of the weighted calculation, and ultimately determine the body forward speed.
The speed is generally achieved by four equivalent wheel speeds and longitudinal acceleration sensor information fusion. Integrating the longitudinal acceleration can be used as the fifth estimate of the vehicle speed. As the basis for calculating the tire slip rate, the estimation of the vehicle speed must be accurate. Some of the electronic control system only use the maximum value of four equivalent wheel speed as the vehicle speed estimates, when the four wheels at the same time locked, this method becomes extremely inaccurate.
When the car turns or slip occurs, the speed of the four wheels will be different, we can according to the degree of side of the body, and the yaw rate, calculate the equivalent wheel speed. This equivalent wheel speed can be used as an estimate of the body mass velocity.
Obviously, how to determine the weight of the rules, is the car manufacturers to do, to collect a lot of data, but also to determine the appropriate trigger time, the appropriate weighting factor, which is more complex, of course, there are Kalman filter and other methods, Do not start to say.
