Development of Wheel-Legged Biped Robots:A Review

The wheel-legged biped robot is a typical ground-based mobile robot that can combine the high velocity and high efficiency pertaining to wheeled motion and the strong,obstacle-crossing performance associated with legged motion.These robots have gradually exhibited satisfactory application potential in various harsh scenarios such as rubble rescue,military operations,and wilderness exploration.Wheel-legged biped robots are divided into four categories according to the open–close chain structure forms and operation task modes,and the latest technology research status is summarized in this paper.The hardware control system,control method,and application are analyzed,and the dynamic balance control for the two-wheel,biomimetic jumping control for the legs and whole-body control for integrating the wheels and legs are analyzed.In summary,it is observed that the current research exhibits problems,such as the insufficient application of novel materials and a rigid–flexible coupling design;the limited application of the advanced,intelligent control methods;the inadequate understanding of the bionic jumping mechanisms in robot legs;and the insufficient coordination ability of the multi-modal motion,which do not exhibit practical application for the wheel-legged biped robots.Finally,this study discusses the key research directions and development trends for the wheel-legged biped robots.

Detachment Behavior of Gecko Toe in Functional Strategies for Bionic Toe

Geckos can efficiently navigate complex terrains due to their multi-level adhesive system that is present on their toes.The setae are responsible for the gecko’s extraordinary adhesion and have garnered wide attention from the scientific community.The majority of the reported works in the literature that have dealt with the peeling models mainly focus on the gecko hierarchical adhesive system,with limited attention given to investigating the influence of gecko toe structure on the detachment.Along these lines,to gain a deeper understanding of the rapid and effortless detachment abilities of gecko toes,the peeling behavior of gecko toes on vertical surfaces was primarily investigated in this work.More specifically,the detachment time of a single toe on a smooth acrylic plate was measured to be 0.41±0.21 s.Moreover,it was observed that the toe assumed a"U"-shaped structure upon complete detachment.Additionally,Finite Element Analysis(FEA)models for three different types of gecko toes were developed to simulate both the displacement-peel and the moment-peel modes.Increasing the segmentation of the adhesive layer led to a gradual decrease in the resultant force,as well as the normal and tangential components.Lastly,a gecko-inspired toe model was constructed and powered by Shape Memory Alloy(SMA).A systematic comparison between the vertical drag separation and the outward flip separation was also conducted.From our analysis,it was clearly demonstrated that outward peel separation significantly necessitated the reduction of the peeling force,thus confirming the advantageous nature of the outward motion in gecko toe detachment.Our data not only contribute to a deeper understanding of the gecko detachment behavior but also offer valuable insights for the advancement of the wall-climbing robot feet.

Design of an Active Flexible Spine for Wall Climbing Robot Using Pneumatic Soft Actuators

Wall climbing robots can be used to undertake missions in many unstructured environments.However,current wall climbing robots have mobility difficulties such as in the turning or accelarating.One of the main reasons for the limitations is the poor flexibility of the spines.Soft robotic technology can actively enable structure deformation and stiffness varations,which provides a solution for the design of active flexible spines.This research utilizes pneumatic soft actuators to design a flexible spine with the abilities of actively bending and twisting by each joint.Using bending and torsion moment equilibriums,respectively,from air pressure to material deformations,the bending and twisting models for a single actuator with respect to different pressure are obtained.The theoretical models are verified by finite-element method simulations and experimental tests.In addition,the bending and twisiting motions of single joint and whole spine are analytically modeled.The results show that the bionic spine can perform desired deformations in accordance with the applied pressure on specified chambers.The variations of the stiffness are also numerically assessed.Finally,the effectiveness of the bionic flexible spine for actively producing sequenced motions as biological spine is experimentally validated.This work demonstrated that the peneumatic spine is potential to improve the spine flexibility of wall climbing robot.

Design and Theoretical Research on Aerial-Aquatic Vehicles:A Review

With the rapid development of unmanned aerial and underwater vehicles,various tasks,such as biodiversity monitoring,surveying,and mapping,as well as,search and rescue can now be completed in a single medium,either underwater or in the air.By systematically examining the water–air cross-medium locomotion of organisms,there has been growing interest in the development of aerial-aquatic vehicles.The goal of this review is to provide a detailed outline of the design and cross-medium theoretical research of the existing aerial-aquatic vehicles based on the research on the organisms capable of transiting between water and air.Although these designs and theoretical frameworks have been validated in many aerial-aquatic vehicles,there are still many problems that need to be addressed,such as inflexible underwater motion and unstable medium conversion.As a result,supplementation of the existing cross-medium biomimetic research,vehicle design,power selection,and cross-medium theory is urgently required to optimize the key technologies in detail.Therefore,by summarizing the existing designs and theoretical approaches on aerial-aquatic vehicles,including biomimetic research on water–air cross-medium locomotion in nature,different power selections,and cross-medium theoretical research,the relative problems and development trends on aerial-aquatic vehicles were thoroughly explored,providing significant help for the subsequent research process.

Effect of Dual-Tasks Walking on Human Gait Patterns

A human gait pattern conformed to the law of the inverted pendulum and could be described by the movement of its center of mass(COM).A sinusoidal function based on an inverted pendulum was used to plan the COM trajectory of humanoid robots for gait control.Therefore,studying the human dual-tasks gait pattern is essential for improving the gait adaptability of humanoid robots.Many well-known humanoid robot prototypes can complete stable walking,running,jumping,and other movements closely mimicking human beings.This study provides a theoretical reference for the gait planning and design of humanoid robots by comparing differences in the stride time,cadence,step length,step width,stride length,walking speed and COM movement during single-and dual-tasks walking.Results showed no significant difference in the time parameters.In dual-tasks walking,the walking speeds decreased(P=0.001)and the COM sidewise movement increased,indicating an enhancement in the automatic motion rhythm in cognitive tasks.Humans can easily select new different speeds to better adapt to the competition of attention resources.To enhance the adaptability of humanoid robots to the COM offset,the independent motion of the hip joint separated from the trunk and lower limbs must be considered in the robot design.

Wheel-legged In-pipe Robot with a Bioinspired Hook and Dry Adhesive Attachment Device

In-pipe robots have been widely used in pipes-with smooth inner walls.However,current in-pipe robots face challenges in terms of moving past obstacles and climbing in marine-vessel pipeline systems,which are affected by marine biofouling and electrochemical corrosion.This paper takes inspiration from the dual-hook structure of Trypoxylus dichotomus’s feet and gecko‑like dry adhesives,proposing an in-pipe robot that is capable of climbing on rough and smooth pipe inwalls.The combination of the bioinspired hook and dry adhesives allows the robot to stably attach to rough or smooth pipe inwalls,while the wheel-leg hybrid mechanism provides better conditions for obstacle traversal.The paper explores the attachment and obstacle-surmounting mechanisms of the robot.Moreover,motion strategies for the robot are devised based on different pipe structural features.The experiments showed that this robot can adapt to both smooth and rough pipe environments simultaneously,and its motion performance is superior to conventional driving mechanisms.The robot’s active turning actuators also enable it to navigate through horizontally or vertically oriented 90°bends.