Leg Structure Research Articles

Leg Configuration Analysis and Prototype Design of Biped Robot Based on Spring Mass Model

The leg structure with high dynamic stability can make the bionic biped robot have the inherent conditions to perform elastic and highly dynamic motion. Compared with the quadruped robot, the leg structure of the biped robot is more complex and has more degrees of freedom. This also complicates kinematic and dynamic modeling. In this paper, the kinematics model of a bionic biped robot is established. The leg configuration of the robot is a series parallel hybrid mechanism with five active joints and six passive joints. The mechanism is a spring mass model that interacts organically with the environment and mimics the characteristics of human walking well. By analyzing the topological configuration of leg mechanism, we use the screw theory to establish the forward and inverse kinematics models. Then, we build the prototype, and use a step gait to test the model and prototype. The research of this paper has obvious application significance for the design and iteration of biped robot prototype.

Estimation of Overall Fatigue Life of Jack-up Leg Structure

Jack-up platforms are designed to work in three conditions: Transit, Preloading and Operating. The fatigue life of the jack-up platforms in operating condition will be determined to be similar to that of offshore fixed steel structures. In preloading conditions, fatigue damage is usually ignored. Up to now, the fatigue damage of the jack-up leg structure in transit conditions has been calculated at approximately 20% of the total fatigue damage of the jack-up leg structure in two conditions (transit and operating). The approximate calculation method is usually accepted by consultants and register agencies. If the approximation is used, the fatigue life of the jack-up leg structure will be calculated only as for the jacket structure of the fixed offshore structure, with 80% of the allowable fatigue life based on standards. The approximation proved to have many disadvantages: the different travel times of each jack-up rig cannot be mentioned; hot spots that need to be maintained during the transit condition have not been pointed out; it is difficult to guarantee the safety of the jack-up leg structures in the transit condition. In order to overcome the limitations of the approximation method, this paper will propose a method to predict the overall fatigue life of the jack-up leg structure in three main problems. Firstly, we use the analysis method of fatigue of fixed steel offshore structures for jack-up leg structures in operating conditions. Secondly, we suggest a method to analyze the fatigue of the structures in transit conditions. Herein, motion analysis and determination of inertia forces on the leg structure are performed by the Boundary Element Model (BEM) in SACS software. Then the inertia forces are assigned to a Finite Element Model (FEM) in SACS to decide the internal forces of the structures. Hotspot stresses are determined by combining nominal stress from FE analysis results with a concentrated stress factor from the analysis of joint local models in the ANSYS program. Then, fatigue damage and fatigue life of hotspots of the structure are determined in the transit condition. Finally, a formula is suggested to determine total fatigue damage in operating conditions and transit conditions with different cases in relation to different fraction factors. These results are used to predict fatigue life corresponding to the most dangerous cases of structural joints. These new suggestions are applied to fatigue analysis for jack-up Tam Dao 05. Currently, the Tam Dao 05 platform has been operating in the Vietnam East Sea. Doi: 10.28991/CEJ-2022-08-03-06 Full Text: PDF

Simulation and analysis of a single actuated quadruped robot

Abstract. In this paper, a leg structure of quadruped robot was designed, based on mechanism synthesis, and aims to allow a system for the complex control of a quadruped robot. This structure is composed of a crank linkage mechanism and quadrilateral mechanism. The innovativeness of this robot is that it can achieve a special gait driven only by single motor. In this research, we set up the kinematic model of leg mechanism through an analytic method. Then we draw the foot track of multiple groups of parameters and select the best parameter group by comparing multiple groups of parameters. After that, the robot model was built and analyzed for its walking ability and climbing ability with virtual prototype technology. Finally, we made an experimental prototype to trial the motion ability of the robot. Simulation and experimental analysis prove that the mechanism is reasonable, reliable and can meet the requirements of linear walking and climbing. The conclusions of this research will be useful for application in the field of single actuated quadruped robots.

Adaptation of a Small Robot for Paddy Fields to the Water Depth Change Using Variable Legs

In this study, the authors conduct an operational test of a small weeding robot in paddy fields, and classify its behavioral incapacitations into two groups. Furthermore, the authors propose a leg structure for overcoming a sudden increase in water depth, one of the main causes of incapacitation. The robot is a two-wheeled vehicle with balance floats in the front and rear of the body, and the proposed structure enables the wheels to reach the ground by deforming the legs holding the wheels (variable-leg). The variable-leg robot is compared with a fixed-leg robot via a water tank experiment. It is verified that the variable-leg model can run at water depths of up to 180 mm, whereas the fixed-leg model can only run at water depths of approximately 80 mm. Furthermore, the variable-leg robot can adapt to dynamically changing water depths, as demonstrated by running over a hole.

Comparison of the Structure of Leg and Pectoral Muscles between Lonchura striata and Copsychus saularis

Background: Bird is important in maintaining biodiversity and its lifestyles and behaviors will pose an important impact on the ecological environment. Birds are also inseparable for ecological stability. Birds’ movement and living habits are a widely studied topic. Methods: Two economic valuable birds, Lonchura striata and Copsychus saularis, were selected in this study. It aims at investigating the characteristics of muscle fiber tissues and comparing the differences between male and female species. Histological techniques were used to determine the characteristics of the muscle fiber (diameter, area and density) in leg and pectoral muscles. Result: There were differences in the muscle fiber characteristics of the Lonchura striata and the Copsychus saularis. The characteristics of muscle fibers between males and females of the same species were significantly different and there were also significant differences in the same parts of different species. The diameter and area of muscle fibers are correlated to the density of muscle fibers. This study suggested that the characteristics of muscle fibers are related to their living habits and population characteristics.

A new species of Clypeocaenis Soldn 1978 (Ephemeroptera: Caenidae) from Tamil Nadu, India.

Clypeocaenis malzacheri sp. nov. is described from the Kottakudi River in southern India, based on larvae and eggs. Clypeocaenis malzacheri sp. nov. appears to be closely related to C. bisetosa Soldn. The new species is distinguished from this species and other congeners based on the structure of the frons; the structure, setation, and maculation of legs; the shape and orientation of the abdominal tergum II projection; and by the shape and denticulation of abdominal sternum IX. Updated couplets for an identification key to Clypeocaenis larvae in the Indomalayan region are provided. The total number of Clypeocaenis species is thereby increased to twelve in the world and seven in India.

Motion coordination control of planar 5R parallel quadruped robot based on SCPL-CPG

The parallel leg of the quadruped robot has good structural stiffness, accurate movement, and strong bearing capacity, but it is complicated to control. To solve this problem, a series connection of parallel legs (SCPL) was proposed, as well as a control strategy combined with the central pattern generator (CPG). With the planar 5R parallel leg as the research object, the SCPL analysis method was used to analyze the leg structure. The topology of CPG network was built with the Hopf oscillator as the unit model, and the CPG was the core to model the robot control system. By continuously adjusting the parameters in the CPG control system and changing the connection weight, and the smooth transition between gaits was realized. The simulation results show that the SCPL analysis method can be effectively used in the analysis of parallel legs, and the control system can realize the smooth transition between gaits, which verifies the feasibility and effectiveness of the proposed control strategy.

Realization of indoor and outdoor localization and navigation for quadruped robots

The quadruped robot has the advantages of flexible movement and large load because of the bionic leg structure. In order to improve their intelligence and autonomy in the complex environment, we build a highly integrated sensing system with lidar and an inertial measurement unit (IMU) on a quadruped robot. After the robot completes the construction of the map, point clouds are aligned using Normal Distribution Transform(NDT) registration to realize the localization of the robot. In the experimental part, we quantitatively tested the accuracy of outdoor localization and also completed indoor-outdoor navigation experiments for the quadruped robot. The experimental results validate the effectiveness of the perception system.

Scanning electron microscopy of cuticular sensory structures on the legs of Micronecta haliploides (Horvath, 1904) and Hydrometra greeni (Kirkaldy, 1898) (Hemiptera: Heteroptera)

Structures on the legs of two hemipteran bugs, Micronecta haliploides (Horvath, 1904) and Hydrometra greeni (Kirkaldy, 1898), belonging to family Micronectidae and Hydrometridae of two infra orders Nepomorpha and Gerromorpha, respectively were investigated using scanning electron microscopy. Both species have a distinctive leg structure bearing specialised cuticular sensory structures. In the study, the sensilla were classified into five basic types: sensilla trichoidea, sensilla basiconidea, sensilla placoidea, porous circular sensilla and sensilla bell mouthed. These sensilla were further differentiated on the basis of shape, size, number, flexibility and type of socket attached. A total of 26 types of sensilla in the legs of these two species were observed. M. haliploides showed 18 types of sensory structures and H. greeni 8 types. A specific morphological structure of the porous circular sensilla was observed and found to be unique.

A novel one-dimensional force sensor calibration method to improve the contact force solution accuracy for legged robot

• This method can be carried out on LHDS without disassembling the force sensor. • This method can avoid the irregular variation of calibration coefficient. • This method can simply compensate for the influence of dynamics. Abstract In this paper, aiming at the phenomenon that the calibration coefficient deviation of the one-dimensional force sensor will lead to the deviation in measuring force, a novel method is proposed to recalibrate the one-dimensional force sensors of each joint directly on the leg hydraulic driving system (LHDS) of legged robot. This method has two main contributions. One is that it not only can be carried out directly on LHDS without disassembling the force sensor but also can avoid the irregular variation of calibration coefficient caused by the installation preloading force, friction, mechanical clearance, and other factors. The other is that the method can simply compensate for the influence of dynamics in the calibration process and avoid the complicated mathematical calculation. Under eight working conditions, the experimental results show that the proposed calibration method can decrease the foot end contact force deviation rate more than 20% in the whole cycle. The novel calibration method proposed in this paper can be extended to any leg structure equipped with the same kind of one-dimensional force sensor. It has practical value in engineering.

A Review of Bioinspired Vibration Control Technology

Due to huge demand in engineering, vibration control technology and related studies have always been at the frontiers of research. Although traditional vibration control methods are stable and reliable, they have obvious shortcomings. Through evolution and natural selection, certain body-parts of animals in the natural world have been cleverly constructed and well designed. This provides a steady stream of inspiration for the design of vibration control equipment. The prime objective of this review is to highlight recent advances in the bionic design of vibration control devices. Current bionic vibration control devices were classified, and their bionic principles were briefly described. One kind was the bionic device based on the brain structure of the woodpecker, which is mostly used to reduce vibration at high frequencies. Another kind of bionic device was based on animal leg structure and showed outstanding performance in low frequency vibration reduction. Finally, we briefly listed the problems that need to be solved in current bionic vibration control technology and gave recommendations for future research direction.

A new species of Tritodynamia (Brachyura, Macrophthalmidae) from Papua, Indonesia

Abstract Tritodynamia nontjii n. sp. is described from Papua, Indonesia, and is distinguished from congeners by its proportionately broader carapace and relatively shorter ambulatory legs. The new species superficially resembles T. yeoi Naruse & Ng, 2010, from Singapore, in having the male first gonopod stout with the distal portion broad and curved, but the two species differ in the proportion of the carapace and structures of the ambulatory legs. A table of morphological differences of all known species of Tritodynamia is also provided to distinguish the taxa.

On some deep-sea Stenheliinae from the Gulf of California and the west coast of the Baja California Peninsula (Mexico): the genus Delavalia Brady, 1869 and proposal of Archaeohuysia gen. nov. and Diarthropodella gen. nov. (Copepoda: Harpacticoida: Miraciidae).

Several species belonging to the harpacticoid families Ameiridae Boeck, Ancorabolidae Sars, Argestidae Por, and Rhizothrichidae Por have been described so far as an ongoing long-term project on the diversity of deep-sea benthic harpacticoids collected from the Gulf of California and Mexican Pacific. Amongst the several harpacticoid taxa, the subfamily Stenheliinae Brady (Miraciidae Dana) showed to be one of the most important components to overall species richness in deep-sea sediments. Following the rejection of segmentation pattern of the first swimming leg as the only discriminant for subgeneric assignment of stenheliin taxa, four new species of Delavalia Brady, 1869 and two new genera, Archaeohuysia gen. nov. and Diarthropodella gen. nov. are proposed herein. The new Delavalia species belong to the longicaudata-group with close relatives in shallow-water habitats. The so far monotypic Archaeohuysia gen. nov. showed to be unique in the combination of the general structure of the first swimming leg and retention of the primitive complement of four setae on the second endopodal segment of the same leg. Diarthropodella gen. nov. is the only stenheliin taxon with a two-segmented exopod of the first swimming leg. Some comments are given on probable multiple colonization events of stenheliin taxa.

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

Design and analysis of a new frame-foot wall-climbing robot

This paper designs and develops a new type of frame-foot wall-climbing robot structure. According to the bionic principle, a new parallel telescopic leg structure is proposed, and the 3D design of the overall structure of the wall-climbing robot is completed. Secondly, the kinematics analysis of the robot is carried out, and the forward and inverse solution models of the leg structure position are completed to verify the feasibility of the leg structure stability. Based on the polynomial motion equations, the robot motion planning and gait design are established, and the speed and acceleration change graphs of the leg structure slider are obtained, which avoids the rigid impact between the parts, and realizes the alternate adsorption and continuous movement of the robot legs, which the rationality of the legs structure design and the stability of the movement are verified. Through simulation and experimental results, it is shown that during the robot’s movement, the leg structure can adjust the step distance and step height according to obstacles, so as to achieve the expected obstacle crossing goal. The leg structure is adjusted according to the working environment to ensure that the fuselage and the working surface are always kept parallel to improve the stability of the overall structure.

Thermo-economic, exergetic and mechanical analysis of thermoelectric generator with hollow leg structure; impact of leg cross-section shape and hollow-to-filled area ratio

Filled square cross-section shape is the common conventional structure for n-type and p-type legs of thermoelectric generators. However, other cross-section shapes with hollow structure can significantly increase the output power of thermoelectric generator. However, mechanical strength and economic considerations may still remain as the significant challenges and factors. Hence, in this research, different hollow cross-section leg shapes are investigated for thermoelectric generator from all thermal, economic, exergetic and mechanical viewpoints simultaneously through a 3D validated numerical simulation. Output voltage/power, energy-efficiency, exergy efficiency, Von-Mises stress, and the dollar/watt value are calculated for all mentioned structures and optimum conditions are identified. As a sample result, the triangular shape leg is able to generate up to 100% more power and better conversion/exergy efficiency (compared to the rectangular) at maximum input heat flux while mechanically less reliable design. Many other remarkable and interesting findings are provided in this manuscript.

Undrained bearing capacity of spudcan in soft-over-stiff clay after penetration

As the boundary condition of jack-up systems, the foundation model of offshore structures affects the vibration mode and structural behavior of leg structure. Typical simple foundation models such as pinned and linear spring do not reflect either plastic failure or the resulting plastic behavior of the soil. Alternatives, for example Model B for clay, derived for consideration of the nonlinear behavior of soil, have been studied continuously improved until recently. Additionally, research on the foundation models has been continued in multi-layered soils, especially stiff-over-soft layer soils that present a risk of punch-through. In the present study, a yield envelope analysis is performed for the situation wherein the jack-up leg penetrates deeply through the soft clay and meets the stiff clay. In such soft-over-stiff clays, both the upper soft clay and the lower stiff clay affect the spudcan, thereby complicating the use of a foundation model of single clay. The numerical analysis used in this study is based on the Coupled Eulerian-Lagrangian (CEL) analysis with strain-dependent nonlinear soil properties. Installation effect and corresponding soil disturbance are considered in the following yield envelope analysis. Undrained bearing capacities of the single clay are calculated at the deep embedment for checking the suitability of the analysis, and continuous results have shown to the existing theories of single clay. In the soft-over-stiff clay case, the lower stiff clay has a significant effect on the capacities in the vertical, horizontal and rotational directions. The squeezing effect does not affect the vertical tensile capacity but increases the compressive vertical, horizontal, and rotational capacities. The stronger the underlying clay and the deeper the embedment, the asymmetrically larger the yield envelope becomes. The calculated yield envelopes are normalized to the increased capacities, and a yield envelope expression for the soft-over-stiff clay is suggested for the normalized shape. The effect of the maximum capacity on the yield envelope equation is examined, and it is found that the largely calculated capacity can make the yield envelope close to the paraboloid.

Real-Time Evaluation Algorithm of Human Body Movement in Football Training Robot

As one of the most challenging topics in the field of artificial intelligence, soccer robots are currently an important platform for humanoid robotics research. Its fields cover a wide range of fields, including robotics, artificial intelligence, and automatic control. Kinematics analysis and action planning are the key technologies in the research of humanoid soccer robots and are the basis for realizing basic actions such as walking. This article mainly introduces the real-time evaluation algorithm of human motion in the football training robot. The football robot action evaluation algorithm proposed here designs the angle and wheel speed of the football robot movement through the evaluation of the angular velocity and linear velocity of the center of mass of the robot. The overall system of the imitation human football robot is studied, including the mechanical system design. The design of the leg structure, the decision-making system based on the finite state machine, the robot vision system, and the image segmentation technology are introduced. The experimental results in this article show that the action of the football training robot model is very stable, the static rotation movement time is about 220 ms, and the fixed-point movement error is less than 1 cm, which fully meets the accuracy requirements of the large-space football robot.

A Bizarre Planthopper Nymph (Hemiptera: Fulgoroidea) from Mid-Cretaceous Kachin Amber.

Simple SummaryThe fossil record of adult planthoppers is relatively rich, but the nymphs are rare and not well studied. Here, we describe a bizarre armoured planthopper nymph: Spinonympha shcherbakovi gen. et sp. nov. from mid-Cretaceous Kachin amber. The new genus and species is characterized by its large size, armoured body, extremely long rostrum, and leg structure. The fossil nymph cannot be attributed to any known planthopper family, but can be excluded from many families due to its large size and leg structure. The armoured body was probably developed for defence, and the extremely long rostrum indicates that, in the past, planthopper feeding on trees with thick and rough bark was more widespread than today. The new find reveals a new armoured morphotype previously unknown in planthopper nymphs.The fossil record of adult planthoppers is comparatively rich, but nymphs are rare and not well studied. Here, we describe a bizarre armoured planthopper nymph, Spinonympha shcherbakovi gen. et sp. nov., in mid-Cretaceous Kachin amber. The new genus is characterized by its large size, body armed with spines and tubercles, extremely long rostrum reaching well beyond the apex of the abdomen; profemur and mesofemur subcylindrical, covered with setae; protibia and mesotibia subquadrangular, densely covered with setae; protarsus and mesotarsus with two segments, tarsomere II longer and wider than I; metatrochanter swollen, metafemur subcylindrical, covered with short setae; metatibia subquadrangular, densely covered with short setae, without lateral spine and pectens without setae; metatarsus with three segments, and metatarsomere III extremely small. The fossil nymph cannot be attributed to any known planthopper family, but can be excluded from many families due to its large size and leg structure. The armoured body was probably developed for defence, and the extremely long rostrum indicates that, in the past, feeding on trees with thick and rough bark was more widespread than today. These features indicate that the new specimen represents a new armoured morphotype of planthopper nymph from the fossil record.

Design of Quadruped Inspection Robot for Substation

The intelligent inspection robots in substations mostly use wheeled chassis, which have good passability when running on flat roads, but it is difficult to effectively cross obstacles under terrain conditions such as steps and stairs. A quadruped inspection robot for substation is designed to improve the walking ability of the robot with a four-leg alternate walking mode to optimize the leg structure design for road conditions such as steps and stairs in the substation. The robot is equipped with pan-tilt detection components and inspection equipment such as multi-degree-of-freedom manipulators can complete intelligent inspection and lightweight maintenance tasks in open substations, and achieve full coverage of the inspection area.