Steering unit and internal drag calculation apparatus used therein

摘要

A power steering apparatus is provided to generate an assistant force corresponding to a change of viscous friction in the steering unit or the like, without losing information on reaction force from a road surface. An external force calculation portion calculates an external force, that is, a force other than a force for steering (i.e. a steering force) among forces (action forces) acting on the steering unit of a vehicle. The external force is assumed to be composed of an outside force received from the road surface, such as an SAT (self-aligning torque), and an internal drag resulting from a viscous friction generated in the steering unit, and the like and these two forces are separated in an outside force and internal drag calculation portion. In separating these two forces, under the assumption that the outside force is a function of a side slip angle and an internal drag is a function of a steering angular velocity, and coefficients of functions are obtained. On the basis of the thus calculated internal drag, a motor control portion controls a motor so as to generate an adequate assistant force. <IMAGE>