This paper presents the design of a compliant manipulator using a series elastic actuator (SEA) and a mechanism for precisely measuring the force acting on the contact part of the manipulator without using a force sensor. It is important to maintain a constant contact force between the compliant manipulator and the wall in order to guarantee cleaning performance, and the ball screw mechanism is used to adapt to changes in the distance and the angle. Position-based impedance control is used to maintain a constant contact force when the manipulator interacts with the wall of the building, and the results confirm that the system stability is guaranteed when using SEA, regardless of the variation in the actual stiffness of the manipulator. The results of extensive experimentation using the test bench demonstrate the force tracking performance against various types of wall changes using the stiff wet-type cleaning manipulator. The results indicate that the stiffness of SEA affects the force tracking performance and system stability under the condition of the manipulator and environment interaction, and that the system stability and control performance can be improved by applying a robust force measurement mechanism to noise.

This paper presents design and force-tracking impedance control of 2-degree-of-freedom (DOF) wall-cleaning manipulator equipped with disturbance observer (DOB) and sliding mode control (SMC). In order to keep in contact with various shapes of walls, the proposed manipulator is designed to ensure 2-DOF motions of translation and tilting by using ball screws. The position-based force tracking impedance control (FTIC) is first adopted for the proposed manipulator not only to interact with walls in a desired dynamic behavior but also to maintain a constant contact force. Also, to improve the force tracking capability of proposed manipulator against different walls and brushes for manipulator, the FTIC is combined with the disturbance observer (DOB) and the sliding mode control (SMC). Extensive experiments prove that although different brushes used for manipulator rotate against varying shapes of walls, the proposed manipulator can keep a constant contact force within a bound of ± 4.5 N by virtue of the proposed FTIC equipped with the DOB and the SMC.