Shunsuke Nansai

Exploration of adaptive gait patterns with a reconfigurable linkage mechanism

Legged robots are able to move across irregular terrains and some can be energy efficient, but are often constrained by a limited range of gaits which can limit their locomotion capabilities considerably. This paper reports a reconfigurable design approach to robotic legged locomotion that produces a wide variety of gait cycles, opening new possibilities for innovative applications. In this paper, we present a distance-based formulation and its application to solve the position analysis problem of a standard Theo Jansen mechanism. By changing the configuration of a linkage, our objective in this study is to identify novel gait patterns of interest for a walking platform. The exemplary gait variations presented in this work demonstrate the feasibility of our approach, and considerably extend the capabilities of the original design to not only produce novel cum useful gait patterns but also to realize behaviors beyond locomotion.

On a Jansen leg with multiple gait patterns for reconfigurable walking platforms

Legged robots are able to move across irregular terrains and those based on 1-degree-of-freedom planar linkages can be energy efficient, but are often constrained by a limited range of gaits which can limit their locomotion capabilities considerably. This article reports the design of a novel reconfigurable Theo Jansen linkage that produces a wide variety of gait cycles, opening new possibilities for innovative applications. The suggested mechanism switches from a pin-jointed Grübler kinematic chain to a 5-degree-of-freedom mechanism with slider joints during the reconfiguration process. It is shown that such reconfigurable linkage significantly extend the capabilities of the original design, while maintaining its mechanical simplicity during normal operation, to not only produce different useful gait patterns but also to realize behaviors beyond locomotion. Experiments with an implemented prototype are presented, and their results validate the proposed approach.

Energy Based Position Control of Jansen Walking Robot

Theo Jansen mechanism is gaining attention among legged robotics researchers due to its scalable design, energy efficiency, low payload to machine load ratio, bio-inspired locomotion, and deterministic foot trajectory. In this paper, we present a novel position control strategy for Jansen walking robot derived using projection method for which energy based control forms the core. Numerical simulations are done to validate the efficacy of the designed controller. This work identifies an appropriate controller gain that decreases the overshoot necessary for successful real world deployments.

A Survey of Wall Climbing Robots: Recent Advances and Challenges

In recent decades, skyscrapers, as represented by the Burj Khalifa in Dubai and Shanghai Tower in Shanghai, have been built due to the improvements of construction technologies. Even in such newfangled skyscrapers, the facades are generally cleaned by humans. Wall climbing robots, which are capable of climbing up vertical surfaces, ceilings and roofs, are expected to replace the manual workforce in facade cleaning works, which is both hazardous and laborious work. Such tasks require these robotic platforms to possess high levels of adaptability and flexibility. This paper presents a detailed review of wall climbing robots categorizing them into six distinct classes based on the adhesive mechanism that they use. This paper concludes by expanding beyond adhesive mechanisms by discussing a set of desirable design attributes of an ideal glass facade cleaning robot towards facilitating targeted future research with clear technical goals and well-defined design trade-off boundaries.

Observer-based state estimation of snake-like robot with rotational elastic actuators

The long-term goal of this study is to realize a locomotion control for snake-like robots on various environments. A key point for the locomotion control is the normal direction friction force of each link of the robot. Because, a real snake can locomote by utilizing the difference of frictions in the propulsive and in the normal direction. In previous our study, a locomotion control of the snake-like robot considering side-slipping has been proposed. However, there are some problems to realize the control by a real machine. As the problems, all state of the snake-like robot is supposed to be observed, and computational load of the control law is too large to be real-time. To solve these problems, this paper aims to develop a state estimation of the snake-like robot in consideration of side-slipping by utilizing an observer. Moreover, a rotational elastic actuator consisting of a motor and a spring is installed for the robot to adapt to various environments. Motion equations of the snake-like robot with rotational elastic actuators and side-slipping effect are derived. Constraint forces of the normal direction of each link are also formulated in the modeling process. A type-I observer based on State Dependent Riccati equation: SDRE is utilized to detect a slipping link of the robot. This detection is based on the generalized coordinate of the robot link estimated by the observer. Numerical simulations are given to verify the effectiveness of the proposed method.

Wheel spider with rolling locomotion: Modeling and simulation

This study aims to develop mathematical model which can capture behavior of “wheel spider” that can perform rolling locomotion and analyze characteristics of the behavior to realize biologically inspired locomotion by robots. Therefore, a rolling wheel spider model is developed by applying constraint force on the ground to a wheel spider model without the ground and considering velocity transformation due to collision. As a result, it was found that the wheel spider goes downhill at a constant speed with rolling whether it is provided with initial velocity or not. In conclusion, the wheel spider can go down the slope over a certain pitch without providing initial velocity.

Dynamic modeling and nonlinear position control of a quadruped robot with theo jansen linkage mechanisms and a single actuator

The Theo Jansen mechanism is gaining widespread popularity among the legged robotics community due to its scalable design, energy efficiency, low payload-to-machine-load ratio, bioinspired locomotion, and deterministic foot trajectory. In this paper, we perform for the first time the dynamic modeling and analysis on a four-legged robot driven by a single actuator and composed of Theo Jansen mechanisms. The projection method is applied to derive the equations of motion of this complex mechanical system and a position control strategy based on energy is proposed. Numerical simulations validate the efficacy of the designed controller, thus setting a theoretical basis for further investigations on Theo Jansen based quadruped robots.

Development of a Module Robot for Glass Façade Cleaning Robot

Our ultimate goal is to develop a glass facade cleaning robot capable of adapting to any skyscrapers. Reconfigurable modular robot system allows to realize different morphology through assembling/disassembling/organizing system of each module. This paper proposes the modular robot strategy for the glass facade cleaning robot, and implements a module robot, which compose most basic role, including both design/development of the real robot and design of a control system on a glass surface. Firstly, design challenges of the glass facade cleaning robot is discussed from sides of glass cleaning process and area coverage, and our basic strategy based on the modular robot system is proposed. And, a control system for a biped type module robot based on the strategy consists of the inverse kinematics, the fifth polynomial interpolation and the sequential control. Finally, an experiment of the developed module on a glass surface is performed.