CONTROL METHOD OF ELECTRIC MOTOR, MOTOR CONTROLLER, AND ELECTRIC POWER STEERING SYSTEM USING THE SAME

摘要

PROBLEM TO BE SOLVED: To continue steering assistance also by an electric power steering system without involving in deterioration of functions of electrical equipment, when a battery is abnormal.

SOLUTION: Electric energy Pw which can be currently generated by an alternator 26 is presumed from a rotating speed of an engine, then the remained electric energy which is secured for the electric equipment 27 to such an extent as deterioration of the functions is not caused is considered as power Pmax which can be supplied for an electric motor 12 to generate steering auxiliary force. When requested torque Treq in which steering torque T is limited according to motor characteristics is or more than torque Tmax which can be output and corresponds to the power Pmax which can be supplied, the requested torque Treq is limited to the torque Tmax which can be output, then steering auxiliary torque command value IM*is computed based on the torque Tmax which can be output. Supposing that a d-axis target current value Id*equals to zero, a q-axis target current value Iq*which can generate the steering auxiliary torque command value IM*is computed, then current values corresponding to the d-axis and q-axis current command values Id*, Iq*are supplied to the electric motor 12.

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