Shunsuke Nansai

The purpose of this paper is to implement a path-following control system based on the kinematics of the Lizard-Inspired Single-Actuated robot (LISA). LISA is a new type of robot that mimics the quadrupedal walking morphology of lizards with a four-bar linkage mechanism and can realize both propulsion and turning with 1 degree-of-freedom. To achieve this purpose, this paper takes 3 approaches: kinematics formulation, control system design, and experimental verification. In the kinematics formulation, we formulate LISA’s turning angle, stride length, posture, propulsive direction, curvature, and position coordinate. In control system design, we design a control system that converges not only the distance error but also the posture error and control input. Conditional equations that can achieve these 3 control targets are formulated using forward kinematics and reference path functions. The experimental verifications were carried out to verify the effectiveness of the designed path-following control system using three types of paths: linear, circular, and combined linear and circular. As a result, it was confirmed that the Root Mean Square values for the control input, the distance error, and the attitude error were sufficiently small in steady state. Therefore, it was confirmed that the 3 control objectives had been achieved.

The purpose of this paper is to develop a new Lizard-Inspired Single-Actuated (LISA) robot prototype capable of achieving the theoretical maximum input angle. Various morphologies for one-degree-of-freedom (1-DOF) robots have been proposed in previous studies. However, these designs face challenges due to their morphology, such as the need for toe slippage during walking. LISA introduces a new multi-legged morphology that overcomes these disadvantages, allowing propulsion and turning in 1-DOF. In this paper, we develop a new LISA prototype with the design requirement of achieving the theoretical maximum input angle while maintaining the robot’s morphology. Three key design points were identified to meet this requirement. The first is to design collision-free link geometry even at the maximum input angle. The second is to develop a push-back mechanism for posture recovery. The third is to implement balancing mechanisms. To evaluate the performance of the new prototype, we formulated the kinematics of LISA. The kinematic formulation defines the robot’s coordinate system, termed “robot coordinate,” and derives key parameters such as turning angle, stride length, posture, direction of travel, and curvature. We then experimentally evaluated the new prototype through two types of tests: a wobble and mechanism evaluation, and a motion performance evaluation. In the wobble and mechanism evaluation, we verified the reproducibility of the newly designed balance mechanism, the ability to achieve the maximum input angle, and the effectiveness of the push-back mechanism. Wobble and the angles of each link during walking were quantitatively measured. The results confirmed that the new LISA prototype meets the design requirement of achieving the maximum input angle and can produce a stable gait. In the motion performance evaluation, we compared the theoretical kinematics with LISA’s actual motion. Measurements from motion capture and angle sensors were compared with the theoretical values. Errors of approximately 4.7% for turning angle and 6.4% for stride length were observed. The causes of these errors are discussed, and the results confirm that the new LISA prototype performs effectively, validating this morphology.

The purpose of this paper is to design a path following control system based on the kinematics of the Lizard-Inspired Single-Actuated robot (LISA). LISA is a new type of robot that mimics the quadrupedal walking morphology of lizards with a four-bar linkage mechanism and can realize both propulsion and turning with 1 degree-of-freedom. To achieve this purpose, this paper takes 3 approaches: kinematics formulation, control system design, and numerical simulation. In the kinematics formulation, we formulate LISA’s turning angle, stride length, posture, propulsive direction, curvature, and position coordinate. In control system design, we design a control system that converges not only distance error but also the posture error and control input. Conditional equations that can achieve these 3 control targets are formulated using forward kinematics and reference path functions, and control inputs are obtained by solving the inverse problem. Numerical simulations verify the effectiveness of the designed control system using 3 types of trajectories: linear, circular, and a combination of circular and linear trajectories. As a result, it is confirmed that the designed control system is effective for all 3 types of trajectories and that not only the distance error but also the attitude and control input can be converged.

Legged locomotion is essential for navigating challenging terrains where conventional robotic systems encounter difficulties. This study investigates the sensitivity of the reconfigurable Klann legged mechanism (KLM) to variations in the input geometric parameters, such as joint position location, link lengths, and angles between linkages, on the continuous coupler curve, which represents the output trace of the leg movement.The continuous coupler curve’s sensitivity is explored using global sensitivity analysis based on Sobol’s sensitivity method. Furthermore, a novel reconfigurability strategy is presented for the Klann mechanism, aiming to reduce the number of required actuators and the complexity in control. In simulation, the coupler curves obtained from the reconfigurable KLM are classified as hammering, digging, jam avoidance, and step climbing using machine learning approaches. Experimental validation is presented, discussing an approach to identifying geometric parameters and the resultant coupler curve. Illustrations of the the complete assembly of the reconfigured KLM with the obtained gaits using limited experiments are also highlighted.

This paper presents an approach to the estimation of a window shape for increasing the adaptability of glass façade-cleaning robots to different buildings. For this approach, a window scanning robot equipped with a 2D laser range scanner installed perpendicularly to a window surface is developed for the testbed, and a method for the window shape estimation is proposed, which consists of the robot’s pose estimation with an extended Kalman filter (EKF) and the loop closure based on the robot’s pose estimated. The effectiveness of the proposed approach is demonstrated through an experiment that is carried out on a window placed on a floor. The experimental results show that the window scanning robot can acquire a window shape, moving on a window surface, and the proposed approach is effective in increasing the accuracy of the window shape estimation.

In this study, trajectory-tracking control for a lizard-inspired single-actuated robot (LISA) is implemented using a novel morphology. A high degree of reproducibility is obtained between the results of kinematic analysis and the behavior of the actual robot. Several 1-degree-of-freedom (DOF)-driven robots have been proposed. However, the application of these robots is severely restricted because of their inherent morphology limitations. LISA is a multilegged robot that can overcome these disadvantages and propel and turn with 1-DOF. In this study, we formulate the kinematics, such as the turning angle and stride length, of LISA. Furthermore, a unique robot coordinate is defined to enable the symmetrical representation of critical robot state quantities. Next, a trajectory-tracking control system based on the proportional-integral-derivative (PID) control is designed, and it is verified by both experiments and numerical simulations. Finally, the results of the experiments and numerical simulations are quantitatively compared according to the root mean square, and the reproducibility of the kinematics analysis and the behavior of the actual system are discussed. This study makes the following contributions: (1) The morphology of LISA facilitates analytical results with only kinematic analysis, which is considerably simpler than dynamics analysis. (2) LISA achieved sufficiently good kinematic performance for the required motions. Experiments revealed that the designed trajectory-tracking control system allows for LISA to appropriately track several types of trajectories.

The purpose of this paper is to design a lizard-inspired robot driven by a single actuator. Lizard-inspired robots in previous studies had the issue of slippage of their supporting legs. To overcome this issue, a lizard-inspired robot consisting of a four-bar linkage mechanism was designed. The purpose of this paper was achieved through three processes. The first process was kinematic analysis, where the turning angle and stride length of the robot were analyzed. The kinematic analysis results were verified via numerical simulations. The second process was the design and fabrication of the robot. For the robot’s design, both a shuffle-walking method utilizing a claw-shaped leg mechanism and a sliding-rod mechanism for equipping the actuator on the robot’s own coordinates were designed. The third process was experimental verification. The first experimental result was that the claw-shaped leg mechanism was capable of generating an 85.26 N difference in the static frictional force in the longitudinal direction. The other three experimental results were that the robot was capable of driving with 3.51%, 3.16%, and 3.53% error compared to the kinematic analyses, respectively.

The purpose of this paper is designing a head control system capable of adapting to passive side-slipping. The environments in which snake-like robots are expected to be utilized generally have ground surface conditions with nonuniform frictional coefficients. In such conditions, the passive wheels of the snake-like robot have a chance of side-slipping. To locomote the snake-like robot dexterously, a control system which adapts to such side-slipping is desired. There are two key points to realizing such a system: First, a dynamic model capable of representing the passive side-slipping must be formulated. A solution for the first key point is to develop a switching dynamic model for the snake-like robot, which switches depending on the occurrence of the side-slipping, by utilizing a projection method. The second key point is to adapt the control system’s behavior to side-slipping. An idea for such a solution is to include the side-slipping velocity in the weighting matrices. An algorithm to estimate the occurrence of side-slipping and the particular side-slipping link is constructed, to formulate the dynamic model depending on the actual side-slipping situation. The effectiveness of the designed Luenberger observer and the head control system for side-slipping adaptation is verified through numerical simulation.

The purpose of this study is to propose a foot location algorithm for a glass façade cleaning robot. As an initial stage of this study, we set three assumptions regarding aimed module robot and window shape. These assumptions set the system some geometric constraint conditions: Right edge of the right cleaning unit moves along with the line of the right window frame. The cleaning area of right and left cleaning unit overlaps a little. The module robot walks with a step at a time. From the conditions, a foot location determination algorithm is constructed corresponding to four situations. The effectiveness of the algorithm is verified through a numerical simulation.