HyunGyu Kim

Water and Ground-Running Robotic Platform by Repeated Motion of Six Spherical Footpads

Bioinspired robotic platforms are based on knowledge from nature. Most robots focus on a single type of locomotion, such as walking or flying. However, multilocomotive robots have recently attracted considerable attention from researchers. In this study, an amphibious robotic platform was developed for operating on water and ground surfaces with a single design. The robot uses spherical footpads to remain on the water surface based on buoyancy and drag forces. Ground walking is also achieved by repeated tripod motion of the spherical footpads. Klann mechanism was adopted and optimized to achieve the footpad motion for stable locomotion on both surfaces. The velocity and pitching angle were analyzed by simulation and experiments at various operating frequencies to validate the performance of the platform. This robot could be applied in nuclear power plant accidents after hydrodynamic-force-based steering by the tail is achieved.

Rolling Stability Enhancement via Balancing Tail for a Water-running Robot

Running on water produces very energy-efficient and fast motion in water environments. Many studies have been performed to develop bio-inspired water-running robots. To achieve good performance, the lifting force is very important for a robot to be able to run on water. The loss of lifting force is associated with the rolling stability of the robot on water. The purpose of this study is to improve the rolling stability of a water-running robot through the periodic motion of a balancing tail. Kinematic analysis was performed to calculate the motions of the legs and the tail, and static analysis was performed to calculate the balancing effect of the tail motion. A numerical model was suggested to determine the dynamic performance of the robotic platform based on kinematic and static results. A simulation based on the numerical model was performed, and the results were compared with empirical data from a robot prototype. The simulation results are in good agreement with the experimental data in terms of rolling stability The lifting force has only a slight effect. The results of this study can be used as a guideline for designing a stable water-running robot.

Empirical Study on Shapes of the Foot Pad and Walking Gaits for Water-Running Robots

Recently, various kinds of biomimetic robots have been studied. Among these biomimetic robots, water-running robots that mimic the characteristics of basilisk lizards have received much attention. However, studies on the performance with respect to different geometric parameters and gaits have been lacking. To run on the surface of water, a water-running robot needs sufficient force with high stability to stay above the water. We experimentally measured the performance of the foot pads with different geometric parameters and with various gaits. We measured and analyzed the forces in the vertical direction and rolling angles of five different foot pad shapes: a circular shape, square shape, half-spherical shape, open half-cylinder shape, and closed half-cylinder shape. Additionally, the rolling stabilities of three kinds of gaits: biped, trotting, and tripod, were also empirically analyzed. The results of this research can be used as a guideline to design a stable water-running robot.

Hexapedal Robotic Platform for Amphibious Locomotion on Ground and Water Surface

Bio-inspiration is a starting point from which to design engineering products by learning the secrets of living creatures. We present the design, analysis, and experimental results of a robotic platform inspired by the basilisk lizard, which is well known for its ability to run on water surface. The goal is to develop a robotic platform for amphibious locomotion on ground and water using a single configuration. A tripod gait is achieved with a hexapedal configuration and four-bar-based repeated motion of the legs. The hexapedal configuration is empirically proven to have an advantage in terms of rolling stability on water. On ground, the tripod gait can satisfy the requirements of static stability to make the center of gravity and center of pressure occur at the same position. The footpad design was determined based on an empirical study of the rolling stability and lifting force. The theoretical background and experimental results are presented to validate the ability of the proposed design to run on water and on the ground.

AnyClimb: A New Wall-Climbing Robotic Platform for Various Curvatures

Climbing robots are being developed to clean, paint, or inspect high areas that are hard to reach for human beings. To widen their application area, robotic platforms have been suggested using bio-inspired attachment methods, such as dry and wet adhesion for smooth and rough surfaces. Generally, robots can climb either walls or poles, but there has been no single robotic platform that can climb both. We developed a new robotic platform to vertically climb a surface with various curvatures in the horizontal direction. Flat dry adhesive was used to make eight footpads. Walking locomotion of the footpads was achieved by a four-bar mechanism with a single motor. To adapt to curved walls, a compliant mechanism is suggested with an asymmetric four-bar mechanism. The kinematics and compliance design parameters were determined by analysis, and experiments were performed on walls with different curvatures. We plan to apply the platform to clean the surfaces of solar panels with different curvatures after modifying the design for commercialization.

Experimental Study on Drag-induced Balancing via a Static Tail for Water-running Robots

Robotics is one area of research in which bio-inspiration is an effective way to design a system by investigating the working principles of nature. Recently, tails have received interest in robotics to increase stability and maneuverability. In this study, we investigated the effectiveness of a static tail for bio-inspired water-running locomotion. The tail was added to increase the stability in the rolling and yawing directions based on the hydrodynamic force from interaction between the tail and the water. The drag coefficient in the interaction is not easy to calculate analytically, so experimental studies were done for various static tail shapes. Five different shapes and compliances in two directions were considered for experimental design candidates. The result was applied to design a stable amphibious robot that can run on ground and water surfaces.

Hexapedal robot for amphibious locomotion on ground and water

Many bio-inspired robots have been developed. Generally, these robots can drive in one environment. It is hard to drive in multiple environments. Therefore, in this study, we developed a robotic platform that can drive in two environments: on the water and the ground. We made a hexapedal robotic platform and analyzed its locomotion when the robot drove on the water and the ground. This analysis considered running speed and pitch motion when the robot drove in the two environments. In addition, we performed an experiment to compare the analyzed results. As a result, this research can be an example to help develop robotic platform amphibious locomotion.

Analysis and Experiment on the Steering Control of a Water-running Robot Using Hydrodynamic Forces

Steering is important for the high maneuverability of mobile robots. Many studies have been performed to improve the maneuverability using a tail. The aim of this research was to verify the performance of a water-running robot steering on water using a tail. Kinematic analysis was performed for the leg mechanism and the interaction forces between the water and the feet to calculate the propulsive drag force of the water. This paper suggests a simplified planar two-link rigid body model to determine the dynamic performance of the robotic platform with respect to the effect of the tail’s motion. Simulations based on a dynamic model were performed by applying a range of motions to the tail. In addition, a simulation with a Bang-bang controller was also performed to control the main frame’s yawing locomotion. Finally, an experiment was conducted with the controller, and the simulation and experimental results were compared. These results can be used as a guideline to develop a steerable water-running robot.

Tail-Assisted Mobility and Stability Enhancement in Yaw and Pitch Motions of a Water-Running Robot

Water-running robots have been developed inspired by a basilisk lizard, which demonstrates highly agile, stable, and energy-efficient locomotion on water surfaces. Current water-running robots are not as stable and agile as their biological counterparts. This study shows how the stability of a water-running robot in the pitch direction can be improved by using an active tail to enable increased propulsion. The mobility of the robot is also increased. To generate force in the pitch and yaw directions, a two-degrees-of-freedom tail is implemented with two circular plates to provide drag. We developed two types of dynamic models for pitch and yaw behavior, and the results are recursively calculated by considering the correlation between the models. The relationship between pitch motion and propulsion was analyzed by simulations. The steering behavior of the robot is also validated while considering the pitch behavior. Experiments were conducted to verify the simulation results.

Optimal Design of Klann-linkage based Walking Mechanism for Amphibious Locomotion on Water and Ground

Walking mechanisms are very important for legged robots to ensure their stable locomotion. In this research, Klann-linkage is suggested as a walking mechanism for a water-running robot and is optimized using level average analysis. The structure of the Klann-linkage is introduced first and design variables for the Klann-linkage are identified considering the kinematic task of the walking mechanism. Next, the design problem is formulated as a path generation optimization problem. Specifically, the desired path for the foot-pad is defined and the objective function is defined as the structural error between the desired and the generated paths. A process for solving the optimization problem is suggested utilizing the sensitivity analysis of the design variables. As a result, optimized lengths of Klann-linkage are obtained and the optimum trajectory is obtained. It is found that the optimized trajectory improves the cost function by about 62% from the initial one. It is expected that the results from this research can be used as a good example for designing legged robots.