PROBLEM TO BE SOLVED: To improve a steering feeling of a driver by optimally setting an assist ratio of steering.SOLUTION: A steering assist ratio calculation device of a power steering system comprises: an assist ratio calculation part 124 for calculating an assist ratio in which a discretion degree of biological information is lowered in each operation state on the basis of a database indicating a relationship between the discretion degree of the biological information related to steering, an assist ratio of steering, and an operation state an assist ratio deviation calculation part 128 for acquiring the deviation of the calculated assist ratio and an assist ratio selection part 129 for selecting one of an average value of the calculated assist ratio, an assist ratio which is obtained by applying an operation state corresponding to an operation route to the database an assist ratio which is obtained by applying the past operation state to the database and an assist ratio which is obtained by applying a current operation state to the database on the basis of the acquired deviation.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】操舵のアシスト比を最適に設定することで運転者の操舵感を向上する。【解決手段】ステアリング操舵に関連する生体情報の離散度と、ステアリング操舵のアシスト比と、運転状態と、の関係を示すデータベースに基づいて、各運転状態において、生体情報の離散度が低くなるアシスト比を演算するアシスト比演算部124と、算出したアシスト比の偏差を求めるアシスト比偏差算出部128と、求めた偏差に基づいて、算出したアシスト比の平均値、運転経路に応じた運転状態を前記データベースに当てはめて得られるアシスト比、将来の運転状態を前記データベースに当てはめて得られるアシスト比、現在の運転状態を前記データベースに当てはめて得られるアシスト比、のいずれかを選択するアシスト比選択部129と、を備える。【選択図】図1
