Determining deviation of a multi jointed robot under load using a tribological contact between an end of the robot and any available hard constraint near the robot, involves pressing the end against the constraint, and then soliciting a movement of the end relative to the constraint in a tribologically resisted direction to apply a force that does not overbear the resistance. By measuring the force and a position encoded by the robot, a deviation of the robot under the corresponding load is determined. Correction terms may be required for deformation of the tribological surface and/or constraint. The constraint may be tooling or parts subjected to an intended process. The deviation at many measurement poses of the robot, each in multiple resisted directions, within the ordinary operating space of the robot, was used to derive compliances of the robot, and a kinetostatic model.