Load Estimation and Compensation Control of a Vertical Two-Link Robot

It is widely recognized that the industrial robots used in production lines or in other engineering fields are installed with comparatively higher rated actuators and have higher rigidity than required, whereas they have too small payload capacity. To achieve high speed drive and accurate positioning under a high payload is indispensable for an advanced industrial robot. In order to increase payload/deadweight ratio without losing high speed driving and accurate control of robots, the nonlinear terms in the equations of motion relating to their load and attitude must be well compensated. The authors have developed and examined two kinds of load estimation and compensation control methods for a vertical-type manipulating robot, which are based on gravity estimation-compensation and fuzzy-set theory. It is confirmed experimentally that although both compensating methods are useful, the fuzzy theory is much better than the gravity compensation method.