Position-Force Adaptive Control of a Robot with Applications in Construction

Typical tasks in construction engineering which can be performed by robots include the spraying or cleaning of surfaces. Both applications require that the external force at the end of the manipulator be properly controlled. In this paper, the force control problem in spraying is analyzed. The paper shows that an unknown 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 modelled as soft contact. Therefore, the force control problem is simplified to the position control problem because both force error and displacement of the end-effector are measurable. 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 is reduced to 8 % with new control scheme.