In this article, we propose an intrinsic contact force sensing method on an arbitrary surface using six-axis force/torque information. An arbitrary surface is defined by a triangle mesh structuring, and the contact sensing solution is achieved by searching the contacted triangle and predicting the actual contact point. The contact sensing algorithm is designed as a three-stage process for swift detection: 1) initial contact triangle selection, 2) solution of the contact point within the triangle plane, and 3) the implementation of a technique for switching the candidate triangle. The performances of the proposed method were evaluated in an experimental setup using a robot manipulator with a commercial force sensor to measure reference data. In addition, to show the usability of the potential robotic applications, the performance verification was performed by measuring the contact force in the complex shape of a commercial collaborative robot.
