Stability of Grinding Robot with Compliance

Abstract

In a grinding robot system, a grinder, which is mounted on the wrist of the manipulator, is liable to vibrate and sometimes made unstable because the stiffness of the manipulator is insufficient. The vibration makes the ground surface rough and the unstable condition may break the manipulator.
The stability in grinding using a compliant manipulator is discussed in this paper. If a plane surface of a workpiece is ground, the motion of the grinder is represented by a linear differential equation. From the equation, it is shown that the stability of the grinder depends on the stiffness matrix of the manipulator, an angle of the inclined plane and a coefficient of friction between the grinder and the workpiece. When a curved surface is ground, the differential equation turns to nonlinearity. Then the bounds of the stable condition is affected by the curvature of the ground surface. From the discussion, it is shown that the rotational angle of the manipulator wrist must be controlled to keep the grinder stable in grinding of a curved surface.