Electric power steering apparatus

Abstract

[Problem] An object of the present invention is to provide an electric power steering apparatus that enables more precise estimation of a coil temperature by considering a heat transfer phenomenon between a control substrate and a coil in addition to a heat transfer phenomenon between respective phases of a poly-phase coil for a poly-phase motor having a multi-system motor winding, and enables the estimation of the coil temperature even when an abnormality occurs in any of the systems. [Means for Solving the Problem] An electric power steering apparatus comprises a temperature sensor that detects a substrate temperature of the control substrate; and a coil temperature estimating section that obtains coil calorific values of respective phases of the poly-phase motor and a substrate calorific value of the control substrate by a motor current of the phase, and estimates a coil temperature of the phase by the coil calorific value, the substrate calorific value and the substrate temperature based on a heat transfer phenomenon between the respective phases that is caused by a difference in temperature between coils of the respective phases and a heat transfer phenomenon between the coil and the control substrate; the coil temperature estimating section estimates the coil temperature by values that are obtained by correcting the coil calorific value and the substrate calorific value that are obtained in a normal system, and the substrate temperature, when an abnormality occurs in any of systems; and the heat transfer phenomenon is expressed by a differential equation.

Dependencies are inferred from the claim text.