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.

A new lizard-inspired robot is presented in this paper, which enables to maintain its moving direction by lateral body motions even during high-speed bipedal running. First, a dynamic model for lizard-inspired robot is derived to simulate the lateral body motion of real lizard. Based upon the simulation using dynamic model, the lizard-inspired robot is tactfully built so that its hind leg is optimally designed on a 4-bar mechanism and its body is simplified to consist of two body links and a tail connected by two revolute joints. The experiments verify that the proposed robot can maintain its moving direction via proper lateral motions during high-speed bipedal running similar to that of real lizard.

This paper presents a new mobile robotic platform (R-Mo) which can reduce unexpected variations in height as well as pitch angle of its main body while traversing rough terrains. As a measure for the smooth movement of mobile platform, the variations in height and pitch angle are chosen in this study. Then, the kinematic analysis on the Rocker-Bogie mechanism is carried out to investigate its variations in height and pitch angle on rough terrains. Based on this result, a new mobile platform is systematically designed by combining the Rocker-Bogie with the inverse four bar linkage. The extensive experiments are carried out by using the Rocker-Bogie mechanism and the proposed R-Mo against rough terrain, which validate that in comparison with the Rocker-Bogie mechanism, the average and maximum variations in height of proposed R-Mo are reduced by 12.72% and 5.96%, respectively, and the average and maximum variations in pitch angle of proposed R-Mo are considerably reduced by 65.87 % and 60.53 %, respectively.

This paper presents a locomotive strategy for a stair-climbing mobile platform built on a rocker-bogie platform, which can surmount indoor stairs or steps by virtue of a new contact angle estimation method. First, link parameters of the rocker-bogie mechanism are optimized through the Taguchi method, with the aim of making the trajectory of the center of mass (CM) of the mobile platform as smooth as possible. Based on the optimization result, the mobile platform is compactly designed to suit indoor applications. A simple, robust and cost-effective estimation method is then proposed to obtain information of the contact angle between each wheel and the stairs with high fidelity. A composite locomotion strategy is suggested, based on the kinematic and kinetic analysis, combined with the contact angle estimation. The stair-climbing capability of the proposed mobile platform is successfully validated through extensive experiments.