摩擦オブザーバを用いた空気圧サーボ系の位置決め制御

摘要

A technique for compensating friction in a pneumatic servo system to perform position control is addressed in this paper. In our technique, a friction observer is introduced into the control system in order to cancel the effect of the friction, since it is capable of estimating dynamically varying friction. Prior to its application to the control system, a conventional friction observer is extended for adapting to a pneumatic actuator by taking account of the influence of pressure inside the cylinder chambers on the friction at the seal. The effect of this modification on the estimating accuracy is confirmed experimentally. The modified observer is also incorporated into a pneumatic positioning device based on pressure control, and the control performance on the positioning accuracy is evaluated. In addition, it is demonstrated that the device's control performance is maintained by using both the above observer and a velocity observer, even when neither an accelerometer nor a velocity sensor is used for the construction of the lower cost system.%空気圧アクチュエータは，出力/重量比の高さ，取 り扱いの簡便さ，空気の圧縮性による柔らかさなどの 特長を備えるため，人が装着あるいは携帯する用途や 人との接触を伴う用途での活用が期待されている．そ こで更なる機能の充実を図るため，サーボ系を構成し て位置決めの柔軟性を持たせようとする場合，種々の 非線形要素が制御系の設計を困難にしている．とりわ け摺動部では高い気密性の確保に相反して大きな摩擦 が生じ，その特性の把握の難しさ，それによるスティ ックスリップの発生などが制御性能の向上に対する妨 げとなっている．近年は発展が著しいロバスト制御な どの先進的な手法による高性能化が注目を集め，報告 例も多岐にわたるが，摩擦補償に焦点を絞った 報告は少ない.