A Force Control for a Peg-Hole System in Assembly Technology

In this paper, the problem of a mated-piece inser- tion is examined due to the current search for precision in the process of fitting. When the required precision is so high that the machine vision is no longer useful, it is necessary to control the force, distinctively in the operations where the gap is narrow such as gear matching, machine tooling or special automation. Thinking about that objective, a peg-hole model was developed in Matlab based on both, the geometric deformation of the sensor, and another passive element for calculating the reaction forces, which are present in the mating process.

Once the peg-hole model is implemented, it is possible to develop a force control for the reference position of the robot’s final point. The force control’s goal is to lower/adequate the reaction forces and this ensures that the peg reduces the contact forces with the walls of the hole. This control calculates the new position of the robot, taking the old position and adding the reaction force multiplied by a proportional constant. The proportionality constants are tuned using an empirical knowledge of the system. At the end of the document the results from the simulation are shown and the tolerance between the piece and the hole is varied.