Road surface state change estimation device and automobile equipped with the same

摘要

The control procedure of the invention sets the measured value of the rotation angular acceleration alpha to a first peak angular acceleration alpha1 at a timing when the rotation angular acceleration alpha of a motor, which directly outputs torque to a drive shaft, reaches a first peak after an increase over a preset threshold value alphaslip that suggests the occurrence of a wheelspin-induced skid. The control procedure also sets a second peak angular acceleration alpha2 by multiplication of the measured value of the rotation angular acceleration alpha by '-1' at a timing when the rotation angular acceleration alpha reaches a negative second peak detected immediately after the first peak. A change of a road surface condition (for example, a shift from a low mu road surface to a high mu road surface) is estimated when the second peak angular acceleration alpha2 is not less than a preset reference value alpharef or when the second peak angular acceleration alpha2 is less than the preset reference value alpharef but is greater than the product of the first peak angular acceleration alpha1 and a constant k. The output torque level from the motor to the drive shaft is restricted for a preset time period, in response to estimation of the change of the road surface condition.