Patent ID: 8315758
Filing Date: 2012-11-20
Classification: B60T,B60W,B62D,Y10T

Abstract:
1. A road surface frictional coefficient estimating apparatus which estimates a frictional coefficient of a road surface, on which a vehicle is traveling, while updating the frictional coefficient, comprising: a first neutral steer point (NSP) yaw moment estimator that is configured to estimate a first estimated value of the NSP yaw moment, which is an external force moment generated about a yaw axis at the NSP of the vehicle by a resultant force of road surface reaction forces acting on each wheel of the vehicle from a road surface, said first estimator using a friction characteristic model indicating a relationship between a slip between a wheel of the vehicle and the road surface and a road surface reaction force, an estimated value of a frictional coefficient already determined and an observed value of a predetermined type of amount to be observed, which is related to a behavior of the vehicle to estimate said first estimated NSP yaw moment value; an acceleration sensor that generates an output based on a lateral acceleration of the vehicle; a second NSP yaw moment estimator that is configured to estimate a second estimated NSP yaw moment value wherein said second estimator determines a value of an external force moment that balances out an inertial force moment from an observed value of a motional state amount of the vehicle that defines the inertial force moment produced about a yaw axis at the NSP by a motion of the vehicle, the observed value of the motional state amount including an observed value of an acceleration indicated by an output of the acceleration sensor, and then obtains the determined value of the external force moment as the second estimated NSP yaw moment value; a frictional coefficient determining device that is configured to determine an increasing/decreasing manipulated variable of an estimated value of the frictional coefficient of the road surface based upon at least a difference between the first estimated NSP yaw moment value and the second estimated NSP yaw moment value or a difference between a first estimated filtering value obtained by passing the first estimated value through a first filter for frequency component adjustment and a second estimated filtering value obtained by passing the second estimated NSP yaw moment value through a second filter for frequency component adjustment, such that the difference is converged to zero; and a frictional coefficient estimated value updater which determines a new estimated value of a frictional coefficient by updating the estimated value of the frictional coefficient of a road surface on the basis of the increasing/decreasing manipulated variable; and a μ sensitivity calculator that is configured to calculate a μ sensitivity value, which is the ratio of an incremental amount of the NSP yaw moment relative to an incremental amount of the frictional coefficient of a road surface, by linearly combining the observed value of a steering angle of a steering control wheel among the wheels of the vehicle and the observed value of the yaw rate of the vehicle, wherein the frictional coefficient determining device determines the increasing/decreasing manipulated variable based upon a difference between the first estimated NSP yaw moment value and the second estimated NSP yaw moment value or the difference between the first estimated filtering value and the second estimated filtering value and the μ sensitivity value.