Towards low cost electrical servo-motor design using backlash/friction compensative control law

The development of mechatronics systems, human interfaces (as force feedback joystick) or toys (as the Aibo robot of Sony) increases the need for small size and low cost components. In order to reduce production costs it should be interesting to reduce the precision of the design or to use less resistant materials. Such choices introduce some imperfections like backlash and friction. To keep in spite of those concessions a good product and an efficient working, we must apply a robust control law to maintain the needed performances. A compensation method for friction and backlash effects in control system is presented. This method uses nonlinear observers to estimate respectively friction force and transmitted torque inside the dead zone.