Legged robots are widely used for walking, running, jumping, and landing on the ground. As mission terrains become increasingly complex, legged robots with greater adaptability are required. However, limited research attention has been paid to enhancing their impact resistance and obstacle-surmounting capabilities. Due to the limitations of motor manufacturing and material, it is more difficult to improve the impact resistance of the motor than to design proper leg lengths. Considering rigid multi-link medium- and large-sized legged robots, we optimize leg lengths to minimize the impact torque on leg joints. An optimal leg-length combination that maximizes obstacle-surmounting capability for medium- and large-size multi-link legged robots is conducted. This research provides a concrete design basis for leg-length optimization in medium- and large-sized multi-link legged robots with the aim of improving impact resistance and obstacle surmounting.

Abstract In order to study the wheel-ground interaction characteristics and influencing factors during the obstacle crossing process of Mars rover, the ground simulation test and analysis are carried out with the ' Zhurong ' Mars rover as the research object. A wheel-ground interaction measurement system is designed and developed to measure and evaluate the mechanical interaction between Mars rover wheels and obstacle stones. Aiming at the Mars patrol scene, the experimental scheme including stone height, driving speed and bilateral obstacle crossing is proposed. The effects of the above factors on the energy consumption and obstacle-crossing three-dimensional force of the Mars rover are tested. The test results show that the increase of obstacle height, the acceleration of driving speed and the obstacle crossing of multiple wheels can increase the wheel-ground force value, and the vehicle power and current also show an upward trend. There are also some deviations in the force value and obstacle surmounting performance between the wheels of the same side suspension. In order to quickly estimate the Mars rover state and simplify the analysis of complex ground mechanical parameters and obstacle-crossing process, a simplified model of the Mars rover considering the conventional obstacle-crossing factors is established. The experimental methods and results of this study can provide data reference for Mars surface inspection, and the obstacle-crossing model can provide theoretical support for the optimization of the obstacle-crossing performance and coordinated control of Mars rover.

In response to the complex unstructured environment of coal mines, a design scheme for variable wheel diameter robots is proposed. Based on the gear, connecting rod and sliding rail mechanism, a wheel with variable diameter was designed. Through the change in the wheel diameter of the robot, the obstacle-crossing ability and terrain adaptation ability of the robot were improved. The kinematic model of a single wheel was established and the variation rule of radial length was analysed. The kinematics model of the whole vehicle was established, and the motion state of the robot under different driving speeds was analysed. Based on RecurDyn software, the robot turning, wheel diameter change process and obstacle surmounting process were simulated. Through 3D printing technology, the robot prototype was made, and the limit obstacle crossing test was carried out. Simulations and prototype tests show that the smallest radius of the wheel radius change is 107 mm, the largest radius is 158 mm, and the limit height for the robot to cross obstacles is 172 mm. After the wheels are unfolded, the centroid of the robot rises by 50 mm, and the fluctuation amplitude of the centroid of the robot when walking with the maximum radius is 3.6 mm. The diameter was increased by 47.6% through the gear, link and sliding rail mechanism, and the exceeding limit height was increased by 60.7% compared with the common wheel-type robot. Compared with tracked and legged robots, the robot designed in this article has high flexibility and lightweight. It can reduce the wheel diameter and accelerate forward on flat roads, and when encountering obstacles, it can increase the wheel diameter to improve obstacle crossing performance. This provides new ideas for the research of special detection robots and the intelligence of coal mines in the future.

PurposeThis study aims to improve the stability and obstacle surmounting ability of the traditional wall-climbing robot on the surface of the ship, a wheel-track composite magnetic adsorption wall-climbing robot is proposed in this paper.Design/methodology/approachThe robot adopts a front and rear obstacle-crossing mechanism to achieve a smooth crossover. The robot is composed of two passive obstacle-crossing mechanisms and a frame, which is composed of two obstacle-crossing magnetic wheels and a set of tracks. The obstacle-crossing is realized by the telescopic expansion of the obstacle-crossing mechanism. Three static failure models are established to determine the minimum adsorption force for the robot to achieve stable motion. The Halbach array is used to construct the track magnetic circuit, and the influence of gap, contact area and magnet thickness on the adsorption force is analyzed by parameter simulation.FindingsThe prototype was designed and manufactured by the authors for static failure and obstacle crossing tests. The prototype test results show that the robot can cross the obstacle of 10 mm height under the condition of 20 kg load.Originality/valueA new structure of wall-climbing robot is proposed and verified. According to the test results, the wall-climbing robot can stably climb over the obstacle of 10 mm height under the condition of 20 kg load, which provides a new idea for future robot design.

A novel method of vehicle height control utilizing semi-active actuator

Soft array structure has the advantages of super redundancy, high fault-tolerance, high adaptability, and high reliability, and has a promising application in soft grasping, soft locomotion, and interface science. However, the variable stiffness of soft array structures has always been challenging. Inspired by the biological tube foot and water vascular system of starfish, we propose a fiber-reinforced soft fluidic tube-foot array with variable stiffness. The soft tube-foot array can be assembled on various shapes of surfaces and can be modularized, enabling the functions of self-adapting, cushioning, variable damping, and obstacle surmounting. Furthermore, we build a peak stiffness model for the bioinspired tube foot, and the theoretical and experimental comparison results show that the mean absolute percent error is ≤9.3%. Finally, we apply the soft tube-foot array to the soft grasping and amphibious wheels. The contribution of this work is to propose a novel soft array structure and a simple and universal method to control the stiffness of fluid-actuated soft array structures.

The wheeled chassis, which is the carrying device of the existing handling robot, is mostly only suitable for flat indoor environments and does not have the ability to work on outdoor rugged terrain, greatly limiting the development of chassis driven handling robots. On this basis, this paper innovatively designs a four-wheel-driving Ackerman chassis with strong vibration absorption and obstacle surmounting capabilities and conducts performance research and optimization on it through quantitative experiments and dynamic simulation. Firstly, based on the introduction of the working principle and structure of the four-wheel-driving Ackerman carrier chassis, a multi-sensor distributed dynamic performance test system is constructed through the analysis of the chassis performance evaluation index. Then, according to the quantitative operation experiment of the chassis, the vibration and acceleration characteristics of the chassis at different positions of the chassis, the amount of slip and straightness of the chassis under different running distance, and the operating characteristics of the chassis under different road conditions and different damping springs conditions were analyzed respectively, which verified the rationality of the chassis design. Finally, by constructing the chassis dynamics simulation model; the influence law of chassis structure; and performance parameters such as chassis wheelbase, guide rod structure, and parameters, wheel friction coefficient and assembly error on the dynamic characteristics of the chassis is studied, and the optimal structure of the four-wheel-driving Ackerman chassis is determined while it is verified based on the simulation results. The research shows that the four-wheel-driving Ackerman chassis has good vibration performance and stability and has strong adaptability to different roads. After optimization, the vibration performance, stability, amount of slip, and straightness of the chassis structure are significantly improved, and the straightness is reduced to 0.399%, which is suitable for precise carriage applications on the chassis. The research has important guiding significance for promoting the development and application of wheeled chassis.

With the innovation and advancement of technology, the research in the field of transformable robots have shown explosive growth and are moving towards intelligence and diversification. Transformable robots can transform their mobile mechanisms according to different terrains for obstacle surmounting, with high flexibility, strong adaptability, and scalability. Thus, transformable robots are widely used in fields such as reconnaissance, rescue, and military. In this article, the characteristics of different obstacle surmounting mechanisms of transformable robots are analysed. Based on three traditional obstacle surmounting mechanisms: wheeled, tracked, and legged, this article introduces the concepts and advantages of combined obstacle surmounting mechanisms and emerging soft and biomimetic robot obstacle surmounting mechanisms. After elaborating on the current research status and partial applications of composite transformable obstacle surmounting robots, the key technologies and difficulties in the research of obstacle surmounting mechanisms for transformable robots are summarized. In addition, this article provides prospects for the application of transformable obstacle surmounting robots in medical and agricultural fields.

Abstract This paper presents on the edge obstacle surmounting method for QuadRunner, a hybrid quadruped robot, to overcome obstacles using hybrid locomotion where both legged and wheel configurations are utilized. When obstacle heights exceed the workspace of its leg, QuadRunner becomes quasi-statically mismatched, meaning the robot’s kinematic constraints are not satisfied, and it fails to achieve the climbing task quasi-statically. By incorporating its body as contact support, the center of gravity (COG) of QuadRunner can be successfully shifted on top of the obstacle to perform surmounting task. The unique design of the QuadRunner leg allows it to behave as a four-bar or slider-crank mechanism depending on the leg’s configuration. Here, we detail the sub-state strategy for its surmount task, where QuadRunner goes through the sub-states {L}EAN, {H}OOK, {F}OUR-BAR, {S}LIDE, {G}ET-UP to climb obstacles. In addition, limitations of the operation are analyzed and the requirements for climbing are identified. With our proposed method, QuadRunner can surmount obstacles of heights between 10 cm and 22 cm (higher than its kinematic max height of 16 cm) within 25 s. Lastly, a reliability test shows that the robot can climb the obstacle with a 70% success rate.

To improve the insufficient adaptability of single degree-of-freedom (DOF) closed-chain legs to unknown surroundings, this paper studies a novel adjustable closed-chain leg mechanism. Based on the traditional six-bar Stephenson-III leg mechanism, we add one degree-of-freedom to realize the adjustment of frame rod position, by which different shapes of foot trajectory curves are obtained. The height of the foot trajectory can be adjusted longitudinally to enhance the obstacle-surmounting ability, and the length of the walking stride can be changed in the transverse direction to achieve the landing point placement of the swing leg. The structure optimization, gait analysis and obstacle-surmounting simulation in different scenarios are carried out. The test results of walking ability and obstacle surmounting performance in specific surrounding show that the designed closed-chain leg mechanism can increase the maximum obstacle-crossing height and walking stability, which proves the promising characteristics of the proposed leg mechanism in the application of multi-legged robots.

PurposeSoft rod-climbing robots have been known to have great potential in a wide variety of working conditions, including cable inspection and pipeline maintenance. However, one of the most notable issues preventing their popular adoption is their inability to effectively cross obstacles or transfer between rods. To overcome these difficulties, this paper aims to propose an inchworm-inspired soft robot with omni-directional steering.Design/methodology/approachTheoretical models are first established to analyze the telescopic deformation, bending, steering and climbing ability of the soft robot. The main modes of movement the soft robot is expected to encounter is then determined through controlled testing so to verify their effectiveness (those being rod climbing, steering and obstacle surmounting).FindingsThe soft robot demonstrated a capability to cross obstacles 1.3 times its own width and bend 120° omni-directionally, evidencing outstanding abilities in both omni-directional steering and obstacle surmounting. In addition, the soft robot also exhibited acceptable climbing performance in a variety of working conditions such as climbing along vertical rods, transferring between rods with differing diameters or friction surfaces and bearing a payload.Originality/valueThe soft robot proposed in this paper possesses abilities that are both exceptional and crucial for practical use, specifically with regard to its omni-directional steering and obstacle surmounting.

Wheel-legged robots have fast and stable motion characteristics on flat roads, but there are the problems of poor balance ability and low movement level in special terrains such as rough roads. In this paper, a new type of wheel-legged robot with parallel four-bar mechanism is proposed, and the linear quadratic regulator (LQR) controller and fuzzy proportion differentiation (PD) jumping controller are designed and developed to achieve stable motion so that the robot has the ability to jump over obstacles and adapt to rough terrain. The amount of energy released by the parallel four-bar linkage mechanism changes with the change of the link angle, and the height of the jump trajectory changes accordingly, which improves the robot's ability to overcome obstacles facing vertical obstacles. Simulations and real scene tests are performed in different terrain environments to verify obstacle crossing capabilities. The simulation results show that, in the pothole terrain, the maximum height error of the two hip joint motors is 2 mm for the obstacle surmounting method of the adaptive retractable wheel-legs; in the process of single leg obstacle surmounting, the maximum height error of the hip joint motors is only 6.6 mm. The comparison of simulation data and real scene experimental results shows that the robot has better robustness in moving under complex terrains.

At present, there are more and more wall climbing robots applied to metal surfaces at home and abroad, and traditional wall climbing robots can no longer meet the needs of reality. In this paper, a wall climbing robot structure based on a flexible track with variable curvature is designed. By increasing the contact area between the caterpillar and the contact surface, the structure principle, static analysis, and simulation of the influence of wall thickness and air gap on the adsorption capacity of the permanent magnet are introduced. The prototype is manufactured to verify its feasibility. The result proves that. The wall climbing robot designed in this paper can move with the load on the variable curvature elevation and has a certain adaptive ability of variable curvature and obstacle surmounting ability.

Today, with the rapid development of robots, intelligent robots can bring us a lot of convenience in all aspects of life. Dangerous and difficult operations can make machines that can adapt to the changes in work tasks and working environments replace manual work. At the same time, they can also ensure personal safety, reduce labor intensity, improve labor productivity, and reduce production costs. As an intelligent mobile robot driven by multiple wheels, the intelligent car has the advantages of small size, lightweight, low cost, and convenient operation. When encountering complex terrain, it is particularly important to study the environmental adaptability and obstacle-surmounting ability of the car. The key technologies of terrain adaptability and obstacle surmounting include obstacle identification, azimuth and distance measurement, and wheel structure design.

Regular inspection and maintenance can ensure safe working conditions of transport pipelines without leakage and damage. Pipeline-climbing robots can be used for rapid inspection of pipelines, effectively reducing labor costs and time consumption. For the annular pipelines outside spherical tanks, the special distribution and installation form presents more high obstacles, and puts forward higher requirements for the robot’s climbing performance and obstacle-surmounting ability. An elastic obstacle-surmounting pipeline-climbing robot with composite wheels is proposed in this paper. The designed elastic shock-absorbing suspension mechanisms and composite wheels were designed to increase the stability and obstacle-surmounting ability of the robot. The adjustable robot frame and rotating joint mechanisms allowed the robot to adapt to pipelines of different diameters and radians. Force analysis and simulation of obstacle surmounting by the robot were performed. Experiments were conducted on a 110-mm diameter pipeline to test the payload performance and obstacle-surmounting ability of the robot. With its elastic shock-absorbing suspension mechanisms, the pipeline-climbing robot could carry a 30 kg payload and stably climb the pipeline. The maximum height of obstacles surmounted by the composite wheels of the robot was 20 mm. In the process of surmounting obstacles, the velocity and inclination angle of the robot could remain relatively stable. This novel composite wheels and mechanisms can improve the performance of the pipeline-climbing robot and solve the problem of surmounting high obstacles. By carrying various equipment and instruments, the robot can promote the automated maintenance and inspection of complex pipelines.

PurposeTo take the advantages of terrain-adaptive capability of legged platform and fast-moving ability of wheeled platform, this paper aims to design a leg-wheel mobile platform for obstacle surmounting and analyze the feasibility and locomotivity of different moving modes.Design/methodology/approachThe platform consists of six leg-wheel units. Each of the units has a close-chain mechanical leg and an actuated wheel at the end of the leg. The platform moves with two modes: legged mode and leg-wheel composite mode. The legged mode achieves high mobility driven by crank motors, while the leg-wheel composite mode achieves obstacle-surmounting ability actuated by crank motors and pitch link motors and obtains high efficiency with the hub motors. The gait planning in different modes has been carried out and the obstacle-surmounting capacity has been analyzed.FindingsBased on the results of kinematic analysis and gait planning of the close-chain leg-wheel platform, the high mobility and efficiency obstacle-surmounting ability are demonstrated with the two movement modes. The feasibility of the design and the performance of the mobile platform is verified with the prototype experiment. The results of this paper show that the platform possesses good obstacle-surmounting capability.Originality/valueThe work presented in this paper is a novel exploration to design a close-chain leg mechanism and with an actuated wheel in series. The close-chain leg mechanism has the advantages of high leg lift and single degree of freedom characteristics, which makes the platform obtain the ability of obstacle-surmounting.

PurposePeriodic inspection of bridge cables is essential, and cable-climbing robots can replace human workers to perform risky tasks and improve inspection efficiency. However, cable inspection robots often fail to surmount large obstacles and cable clamps. The purpose of this paper is to develop a practical cable inspection robot with stronger obstacle-surmounting performance and circumferential rotation capability.Design/methodology/approa/chA cable inspection robot with novel elastic suspension mechanisms and circumferential rotation mechanisms is designed and proposed in this study. The supporting force and spring deformation of the elastic suspension are investigated and calculated. Dynamic analysis of obstacle surmounting and circumferential rotation is performed. Experiments are conducted on vertical and inclined cables to test the obstacle-surmounting performance and cable-clamp passing of the robot. The practicality of the robot is then verified in field tests.FindingsWith its elastic suspension mechanisms, the cable inspection robot can carry a 12.4 kg payload and stably climb a vertical cable. The maximum heights of obstacles surmounted by the driving wheels and the passive wheels of the robot are 15 mm and 13 mm, respectively. Equipped with circumferential rotation mechanisms, the robot can flexibly rotate and successfully pass cable clamps.Originality/valueThe novel elastic suspension mechanism and circumferential rotation mechanism improve the performance of the cable inspection robot and solve the problem of surmounting obstacles and cable clamps. Application of the robot can promote the automation of bridge cable inspection.

Origami-inspired magnetic-driven soft actuators with programmable designs and multiple applications

In this paper, the static analysis of an electric four-wheel drive rodless aircraft tractor over obstacle with load is carried out. Based on MATLAB, all combination of front and rear wheel driving forces are calculated, and the minimum driving force required for obstacle surmounting under different parameters is obtained. The above work provides necessary theoretical basis for tractor design.

The paper proposes a novel multi-legged robot with pitch adjustive units aiming at obstacle surmounting. With only 6 degrees of freedom, the robot with 16 mechanical legs walks steadily and surmounts the obstacles on the complex terrain. The leg unit with adjustive pitch provides a large workspace and empowers the legs to climb up obstacles in large sizes, which enhances the obstacle surmounting capability. The pitch adjustment in leg unit requires as few independent adjusting actuators as possible. Based on the kinematic analysis of the mechanical leg, the biped and quadruped leg units with adjustive pitch are analyzed and compared. The configuration of the robot is designed to obtain a compact structure and pragmatic performance. The uncertainty of the obstacle size and position in the surmounting process is taken into consideration and the parameters of the adjustments and the feasible strategies for obstacle surmounting are presented. Then the 3D virtual model and the robot prototype are built and the multi-body dynamic simulations and prototype experiments are carried out. The results from the simulations and the experiments show that the robot possesses good obstacle surmounting capabilities.