Position-force adaptive control for construction robots

Typical tasks in construction engineering that can be performed by robots include the spraying or cleaning of surfaces. Both applications require that the external force at the end effector of the manipulator be properly controlled. In this paper, the force-control problem in spraying is analyzed. The paper shows that an unpredictable jet force causes the end effector to diverge from its desired trajectory. The interface between the end effector of the robot and the jet force is modeled as soft contact because both force error and displacement of the end effector are measurable. Therefore, the force-control problem is simplified to the position-control problem. The proposed control scheme, using a position-force adaptive controller, is applied to counterbalancing a jet force. Computer simulation demonstrates that the scheme works well. The maximal position error can be controlled to within 4 mm with the new controller.