Parameter Identification and Transition Detection of Contact Conditions of a Robot by Active Force Sensing

Abstract

When a grasped object is in contact with external environment, it is required to identify contact conditions prior to performing assembly tasks. The contact conditions include contact position, contact force, contact type, direction of contact normal, and direction of contact line between a grasped object and external environment. In order to achieve the assembly tasks, the contact type must be measured and controlled, for example, when changing from point contact type to line or planar contact type. This paper discusses parameter identification and transition detection of the contact conditions by active force sensing. The contact type is assumed to be point, soft-finger, line, or planar contact type with friction. To detect transition of contact type quickly, the limited number of measurement data is utilized, and weight of the latest data are enlarged. To eliminate offset of measurement data, deviated force and moment are derived. To correct and reduce an error of judged contact type, continuity of time series of the judged type is checked and revised. The effectiveness of this method is demonstrated by using numerical examples.